Requesting "Compilation of Materials from the Thirteenth National Technical Experience Exchange Meeting on Small Nitrogen Fertilizers"

Looking forward to it...:) :handshake

I'm also waiting anxiously :L :L

Speech at the 13th National Small Nitrogen Fertilizer Technical Experience Exchange Meeting Kong Xianglin, Vice Chairman of China Nitrogen Fertilizer Industry Association (November 27, 2006) Dear experts and colleagues: In the first year of the "Eleventh Five-Year Plan", on the eve of the Fourth Member Congress of the China Nitrogen Fertilizer Industry Association, we held the "Tenth National Small Nitrogen Fertilizer Technical Experience Exchange Meeting" here. The purpose is to implement the spirit of the Fifth Plenary Session of the 16th CPC Central Committee, guided by the scientific outlook on development, and at a new starting point for development, promote industry technological progress and industrial upgrading, and make new contributions to the comprehensive, coordinated and sustainable development of the nitrogen fertilizer industry. This meeting also has extremely important historical significance, that is, the fourth member representative conference of the China Nitrogen Fertilizer Industry Association will be based on the actual development of the nitrogen fertilizer industry, as well as enterprises and * * In response to the requirements for the work of the association, it is planned to cancel the two branches of the Large and Medium Nitrogen Association and the Small Nitrogen Branch. In the future, the association will no longer organize meetings in the names of Small Nitrogen Fertilizer and Large and Medium Nitrogen Fertilizer (except for the 50th anniversary of the birth of the small nitrogen fertilizer industry). In the actual situation where small nitrogen fertilizer companies and large and medium nitrogen companies have long been difficult to define, and the scale boundaries have long been blurred, dividing nitrogen fertilizer companies into these two types is no longer conducive to the development of the industry. In a sense, it is the development and growth of small nitrogen fertilizer itself that makes the name "small nitrogen fertilizer" become history. This is a glorious history! This meeting is the last national small nitrogen fertilizer technical experience exchange meeting held by the Nitrogen Fertilizer Association in the name of small nitrogen fertilizer. Since the Ministry of Chemical Industry held the first national experience exchange meeting on technical transformation of small nitrogen fertilizers in Hangzhou in 1974, each technical experience exchange meeting has played an important role in promoting the technological development of the small nitrogen fertilizer industry. Each meeting is a milestone in the development of small nitrogen fertilizers. In 1974, the Hangzhou Conference proposed the development policy of “exploiting equipment potential, technological transformation, small reforms, and complete supporting facilities”, and began the journey of technological transformation of small nitrogen fertilizers. For many years, even in * * In a difficult environment where destiny denies technology, talent, and a large number of "productivity-only" people believe that small nitrogen fertilizers still adhere to technological progress and continuous development. In 2005, the national output of minor synthetic ammonia was 30.563 million tons, the output of nitrogen fertilizer was 18.485 million tons, and the output of urea was 20.983 million tons, accounting for 66.0%, 63.3% and 50.6% of the national output respectively. ； The national small methanol output is 3.176 million tons, accounting for 76.6% of the national methanol output of nitrogen-reducing enterprises. The small nitrogen fertilizer industry has made great contributions to the national economic development and agricultural production increase. The theme of our technical experience exchange meeting is: Independent innovation, technological progress, and meeting new challenges. This meeting will comprehensively summarize the achievements and experiences in the development and progress of small nitrogen fertilizer technology nationwide since the 12th National Small Nitrogen Fertilizer Technical Experience Exchange Conference in November 2002, and commend the achievements made in the past four years. * * Technical achievements and individuals who have made outstanding contributions to the technological progress of the industry, other than the technological progress awards at the national and provincial levels, will also study the direction and focus of technological progress in the small nitrogen fertilizer industry from the perspective of the pressures and challenges faced by the nitrogen fertilizer industry and from an overall and strategic perspective. Below, I will share some thoughts and opinions for your reference. 1. The main achievements in the technological progress of small nitrogen fertilizers in recent years: 1. A number of technologies with independent intellectual property rights have been developed, which has improved the core competitiveness of the industry. On December 28, 2004, Shandong Hualu Hengsheng's large-scale localized ammonia plant with an annual output of 300,000 tons was put into operation. This is our first domestically produced 300,000-ton ammonia plant. Since 1973, my country has introduced 13 sets of complete sets of plants with a daily output of 1,000 tons of synthetic ammonia and a daily output of 1,620-1,740 tons of urea from the United States, the Netherlands, Japan, and France. The first set was put into operation in Sichuan Chemical in May 1976. Subsequently, 19 sets of large-scale nitrogen fertilizer plants were introduced successively, and a total of 32 sets of plants were introduced. Only after Hualu Hengsheng’s domestically produced equipment was successfully put into operation, the history of large-scale nitrogen fertilizer equipment mainly relying on imports was ended. The technology of this domestically produced device with independent property rights includes: Large-scale clean coal gasification technology, low-temperature methanol washing and liquid nitrogen washing technology, 11.0MPa ammonia synthesis technology, new full-cycle urea transformation technology, double drum fluidized bed large particle urea and 40000m3/h large-scale air separation, etc. In August 2005, my country's first domestically produced 200,000-ton ammonia synthesis plant with an annual output of 200,000 tons with independent intellectual property rights was completed and put into operation in Meifeng, Sichuan. This plant adopted an advanced new natural gas continuous catalytic conversion process, 15MPa low-pressure synthesis, and a new improved CO2 stripping urea process. The completion of these two sets of large-scale nitrogen fertilizer domestically produced equipment has brought my country's nitrogen fertilizer production equipment design and manufacturing technology into the world's advanced ranks. This is the pride of Hualu Hengsheng and Meifeng Enterprises, and also the glory of the entire small nitrogen fertilizer industry. In recent years, a large number of technologies with independent intellectual property rights have been developed and applied in small nitrogen fertilizer plants, such as: Ash-fused polypulverized coal gasification technology, alcohol hydrocarbonization synthesis gas purification technology, "quasi-zero" steam consumption low-temperature conversion technology, pressure swing adsorption decarbonization technology, low-pressure methanol technology, etc. have been adopted in the small nitrogen fertilizer industry, which has effectively promoted the improvement of the core competitiveness of the industry. 2. The large-scale equipment promotes the optimization and upgrading of the small nitrogen fertilizer industry. The technological progress of small nitrogen fertilizers has promoted the development of large-scale equipment. According to incomplete statistics, so far, there are 15 sets of "18, 30" units and more than 90 sets of "8, 13" units for small nitrogen fertilizers across the country, including Yihua, Deqilong, Yishan, Alliance, and Xinlianxin. It is expected that 6 sets of "18, 30" units will be completed and put into operation in small nitrogen fertilizer plants next year. The enlargement of the device promotes the enlargement of the capabilities of a single piece of equipment. So far, three sets of Φ2000 ammonia synthesis towers have been put into production: Hualu Hengsheng, Mingshui and Shouguang. ； Five sets of Φ1800 ammonia synthesis towers have been put into operation in small nitrogen fertilizer plants. The Φ2200 ammonia synthesis tower will be put into production in early 2007 in Luxi, Shandong. There are 5 sets of Φ1800 CO2 stripping urea synthesis towers supporting the "18, 30" small nitrogen fertilizer devices, and there are also 7 sets of Φ2680 urea towers with a volume of 142m3. The single-system medium-pressure string tower device for co-production of methanol using a Φ2000 methanol tower has an annual output of 60,000 tons. With the improvement of coal gas production technology and equipment level, the dominant furnace type Φ2400 has been replaced by the Φ2600 furnace type. Large-scale host equipment has also developed rapidly with the large-scale equipment. At present, there are many hydrogen-nitrogen compressors with a single unit annual output of 25,000 tons and 40,000 tons of synthetic ammonia in operation, with gas volumes of 180 m3/min and 305 m3/min. ； CO2 compressors have also been produced for supporting the "8, 13" and "18, 30" units with a single gas volume of 85 m3/min, 112 m3/min, 153 m3/min and 195 m3/min. With the enlargement of host equipment, other static equipment and pumps are also developing towards enlargement. 3. Promote a number of key and common new processes, new equipment, and new technologies to improve the overall level of the small nitrogen fertilizer industry. The past few years have been an important period of opportunity for the development of small nitrogen fertilizers. First, because * * Pay special attention to agriculture and chemical fertilizers ； Second, because of the gradual increase in market pressure, ； Third, because the economic benefits of enterprises are relatively good, advanced technologies and equipment have developed rapidly. A large number of advanced technologies have won science and technology progress awards at all levels or been recommended as "circular economy supporting technologies". according to * * At the request of the National Development and Reform Commission, the association reviewed and recommended 18 development units and 24 technologies such as Shijiazhuang Jinggong Chemical Equipment Company and Beijing Dalike Company as supporting technologies for circular economy in the nitrogen fertilizer industry, 15 of which have been recommended by the National Development and Reform Commission. Recently, the association reviewed the Nitrogen Fertilizer Technology Progress Award and commended the * * , advanced technologies and individuals other than provincial and ministerial level scientific and technological progress awards. Through the review, a total of 15 technologies including zero discharge of wastewater from nitrogen fertilizer production, development and application of enterprise management and control integrated systems, ammonia synthesis raw materials with mild gasification furnaces, clean production technology for coal-to-gas nitrogen fertilizer production equipment, ammonia synthesis tower control and online operation optimization, and prilling tower dust purification methods, were awarded. 79 individuals won the "Nitrogen Fertilizer Unemployed Technology Progress Award." In addition, there are a large number of new technologies and small reforms that have also played a good role in the production of small nitrogen fertilizers, such as ERP enterprise resource planning management system, gas generation and pressure regulating fans, pressure-resistant water jackets, urea self-stripping towers, urea twin-tower series technology, etc. The development, promotion and application of all these technologies are the overall level of small nitrogen fertilizers. * * Improved support. 4. The adjustment of raw material and product structure has opened up broad prospects for the development of small nitrogen fertilizers. In recent years, the nitrogen fertilizer industry has adjusted its raw material and power structure. Nitrogen fertilizer production capacity has been more rationally distributed to raw material production areas and concentrated markets, and significant progress has been made in the localization of raw materials and comprehensive utilization of resources. In 2005, the output of synthetic ammonia using coal as raw material accounted for 73.0% of the national ammonia output. From 2004 to 2005, it was included in the * * There are 25 nitrogen fertilizer companies piloted by the National Development and Reform Commission to adjust the raw material and power structure. Among them, there are 16 small nitrogen fertilizer plants and 21 projects. So far, 8 projects including Fujian Yongan and Deqilong have been completed and put into operation. At present, the construction of non-anthracite coal gasification equipment has generally received attention. The ammonia production capacity of the non-smokeless block gas equipment that has been put into operation has reached 2.38 million tons/year, and there are 60 sets of gas furnaces that have been put into operation (including 21 sets of Lurgi, 29 sets of Texaco coal-water slurry furnaces, 6 sets of Ende furnaces, 3 sets of ash fusion furnaces, and 1 set of Shell furnaces) ； There are about 48 units under construction (including 3 Lurgi furnaces, 18 coal-water slurry furnaces such as Texaco, 1 Ende furnace, 11 ash fusion furnaces, 12 Shell furnaces, and 3 space furnaces). In addition, pulverized coal forming devices for humic acid coal rods and briquettes have been built and used in many factories, greatly improving the utilization rate of anthracite pulverized coal. In the adjustment of nitrogen fertilizer product structure, in recent years, in addition to the increase in the proportion of high-concentration nitrogen fertilizer products and the increase in compounding rate, the most outstanding benefit is the substantial increase in methanol production of nitrogen fertilizer companies. This is also an outstanding achievement of nitrogen fertilizer companies in reducing CO and CO2 losses and comprehensive utilization. In 2005, the methanol output of small nitrogen fertilizer enterprises was 3.176 million tons, accounting for 76.6% of the methanol output of nitrogen fertilizer enterprises. From January to September this year, the output of joint alcohol increased by 24.8% year-on-year. Five sets of low-pressure methanol were put into operation at Deqilong, Fengxi, Lianhe, Guangshan, and Suiping, making the methanol production equipment of small nitrogen fertilizer plants a big step forward in the direction of large-scale and energy-saving. The increase in methanol production of small nitrogen fertilizer enterprises not only increases the economic benefits of the enterprises, but also lays a certain foundation for my country's coal-to-oil energy processing. 5. The development of clean production and pollution control technologies for small nitrogen fertilizers has created favorable conditions for the sustainable development of small nitrogen fertilizers. In recent years, nitrogen fertilizer companies have generally attached great importance to and gradually implemented cleaner production, reducing the generation of pollutants from the source and improving the efficiency of resource and energy utilization. All companies have basically been able to discharge water pollutants up to standard, and under the leadership of industry associations, they have developed and begun to promote "zero discharge technology for nitrogen fertilizer production wastewater." This technology has been listed as * * It is the focus of the special project on the use of sewage fees by the State Environmental Protection Administration and the Ministry of Finance, and is promoted in pollution control projects in key watersheds such as the "Three Rivers and Three Lakes". It is especially commonly used in the pollution control projects of nearly a hundred nitrogen fertilizer companies in the Huaihe River Basin. The implementation of these projects will * * Improve the environmental protection status of nitrogen fertilizer companies. Recently, Hebei Zhengyuan Company Lingshou Fertilizer Stone, on the basis of implementing a zero-discharge sewage project, creatively used reverse osmosis desalted water as supplementary water, which increased the concentration factor of circulating water by dozens of times, making the circulating water basically non-discharged, or "circulation-level zero discharge." This technology greatly saves water consumption. This is another major development in zero wastewater discharge. This technology is also very meaningful for the national water conservation work. Ministry of Finance and * * The State Environmental Protection Administration has included it in the pilot program. 2. The direction and focus of the development of small nitrogen fertilizer technology in the next few years. In today's world, technological development is changing with each passing day. Science and technology have become an important factor in promoting economic development, promoting social progress and maintaining * * The leading force in security. The history of the development of small nitrogen fertilizers is originally a history of technological progress. ； Without technological progress, there would be no small nitrogen fertilizer today. Relying on technological progress, we have overcome one difficulty after another in development. At present, my country's nitrogen fertilizer industry faces very prominent contradictions: First, the market economy continues to develop, and the marketization process of the nitrogen fertilizer industry is accelerating. ； Second, as promised upon joining the WTO, foreign fertilizer wholesale and retail industries will enter China on December 11 this year. ； Third, energy supply is becoming increasingly tight, and ammonia energy quota management has been put on the agenda. * * The National Development and Reform Commission has required the China Nitrogen Fertilizer Industry Association to prepare the "Synthetic Ammonia Energy Consumption Quota Standard." we base on * * At the request of the Bureau of Statistics, the "Statistical Methods for Nitrogen Fertilizer Production" are being re-edited, among which the "Statistical Methods for Ammonia Energy Consumption" will be trialled in this year's annual report. In the future, it may be necessary to formulate price increase measures or quota supply measures for energy consumption that exceeds the quota. ； Fourth, environmental protection and safety requirements have become increasingly strict. Synthetic ammonia and methanol have been included in the management of hazardous chemicals, and pollutant emission standards and total volume control requirements for nitrogen fertilizer production are constantly improving. How will we deal with these current contradictions? What can we rely on to win the future? The top priority is to rely on structural adjustment and technological progress. Although the small nitrogen fertilizer industry has made great progress in technological progress, its competitiveness is still weak. Next, I will give you some opinions on the direction and focus of the development of small nitrogen fertilizer technology in the next few years for your discussion. 1. Vigorously develop and apply advanced practical technologies, adhere to economical development, clean development, and safe development, develop circular economy, and achieve sustainable development. Energy saving, water saving, environmental protection and safety must be the foundation for the existence and development of small nitrogen fertilizer companies in the future. Nitrogen fertilizer production is a major energy consumer in the country. In 2005, the national anthracite output was 220 million tons, and the national nitrogen fertilizer companies used 55 million tons, accounting for 25% ； National natural gas production is 50 billion m3, of which 22.7% is used by national nitrogen fertilizer companies. ； The national electricity output was 2,474.7 billion kWh, and the national nitrogen fertilizer electricity consumption was 68.13 billion kWh (including 58.6 billion kWh for process power), accounting for 2.75% and 27% of the chemical industry's electricity consumption. Nitrogen fertilizer production is still a large user of water. In 2005, nitrogen fertilizer enterprises across the country used approximately 2.4 billion meters of water3. It can be seen that energy conservation and water conservation in nitrogen fertilizer production are not only the key for enterprises to reduce costs, but also a major event in the development of the national economy. Therefore, the nitrogen fertilizer industry must strive to achieve the goals of reducing energy consumption by 5-8% and water consumption by 20% by the end of the "Eleventh Five-Year Plan" through the development, application and vigorous promotion of advanced technologies. Here I will make the following simple analysis. It can be seen that adhering to economical development, further saving energy, reducing consumption, and reducing production costs have a huge impact on the development of the nitrogen fertilizer industry. ； For example, the current national average price of natural gas for nitrogen fertilizers is 0.7 yuan/m3, and the natural gas expenditures of nitrogen fertilizer companies nationwide have reached 7.7 billion yuan. If the natural gas price is raised to 1.0 yuan/m3, expenditures will increase by 3.3 billion yuan, and the total natural gas expenditures will reach 11 billion yuan. ； For example, the current average coal price for nitrogen fertilizer companies nationwide is 670 yuan/ton, and the national coal expenditure in the nitrogen fertilizer industry has reached 36.9 billion yuan. If the coal price is slightly raised to 700 yuan/ton, the total coal expenditure in the national nitrogen fertilizer industry will reach 38.5 billion yuan. ； For example, the current national average electricity price for nitrogen fertilizer is 0.33 yuan/kwh, and the electricity expenditure of the national nitrogen fertilizer industry has reached 24.8 billion yuan. The above three energy expenditures are currently 69.4 billion yuan, accounting for 64.5% of the country's total nitrogen fertilizer output value of 107.55 billion in 2005. If the preferential prices for gas and electricity are not calculated, the above three expenditures are 87.83 billion yuan, accounting for 81.6% of the total output value. Expenditures on freight rates and value-added tax are not calculated here, nor are the impacts of further increases in industrial natural gas and electricity prices. It can be seen that only by adhering to economical development, clean development, and safe development, nitrogen fertilizer companies can achieve sustainable development of the nitrogen fertilizer industry. 2. Accelerate the development of domestic pulverized coal gasification technology and promote the adjustment of raw material structure. At present, some small nitrogen fertilizer companies have urgent requirements for the construction of pulverized coal gasification equipment, but they are difficult to decide on the choice of furnace type. We hope that Linquan Nitrogen Fertilizer Plant will strengthen cooperation with aerospace engineering companies, speed up the construction of localized space furnaces, and set an example for pulverized coal gasification in nitrogen fertilizer plants as soon as possible. In addition, it is recommended that domestically produced ash melting furnaces should work hard to increase the pressure and reduce methane, and continuously improve the gasification level during development. Of course, we must also pay attention to the construction of coal gasification projects using imported technologies. It is hoped that through these works, the construction speed of pulverized coal gasification equipment will be accelerated and the adjustment of raw material structure will be promoted. 3. Accelerate the development of coal chemical industry, expand business areas, and improve corporate economic benefits. The coal chemical industry refers to the industry that uses coal as the main raw material to produce chemical products, including coal coking, coal gasification, keroseneization, calcium carbide and other industries. It covers coke, calcium carbide, fertilizer, methanol, bisether, olefins, oil products and other products produced from coal as raw materials. It implements the oil substitution strategy, alleviates the contradiction between oil supply and demand, and promotes stable social and economic development. according to * * The National Development and Reform Commission predicts that the market demand for methanol (including dimethyl ether and methanol for olefins) will increase by 20 million tons from 6.66 million tons in 2005 in 2010. ； Civilian demand for dimethyl ether will increase from 200,000 tons to 7 million tons. In 2005, the national methanol output was 6.418 million tons, of which 3.179 million tons were produced by small nitrogen fertilizer plants (of which 3.018 million tons were co-produced methanol). The production of methanol by nitrogen fertilizer plants has the advantages of combining technical advantages, market layout advantages, and equipment technology. In the future, alcohol and ammonia co-production will be developed while the methanol unit is large-scale, and great efforts will be made in developing the civilian dimethyl ether market and methanol downstream products, so that nitrogen fertilizer companies can expand their business areas and further improve the economic benefits of the company. 4. Strengthen technical exchanges between large, medium and small nitrogen fertilizer companies, learn from each other's strengths, and further improve the technical level of small nitrogen fertilizers. At present, there is little communication between large, medium and small nitrogen fertilizer companies. Although small nitrogen fertilizers have many advantages in technological development, the equipment level and technical level of large and medium-sized enterprises, especially large enterprises, are much higher than that of small nitrogen fertilizers. The technical quality of technical personnel in medium-sized enterprises is generally better than that of small nitrogen fertilizers. For example, some medium nitrogen fertilizer enterprises such as Anhui Huaihua and Henan Anyang are all worthy of learning from small nitrogen fertilizers. * technology and experience. In the future, the association will not only hold meetings to strengthen exchanges, but also organize mutual learning between enterprises. * , hoping that small nitrogen fertilizers can learn more technologies and experiences from the integration of large, medium and small nitrogen fertilizer companies to promote the improvement and development of small nitrogen fertilizer technology levels. 5. Build a technological innovation system with enterprises as the main body and improve the independent innovation capabilities of small nitrogen fertilizers. Building a technological innovation system with enterprises as the main body and integrating industry, academia and research is an objective need to promote technological innovation in the industry. In the recent work of selecting well-known urea brands, we felt that small nitrogen fertilizer companies still have a large gap in corporate R&D systems, independent innovation projects, R&D investment and intellectual property awareness, and cannot keep up with the needs of development. In the future, small nitrogen fertilizer companies must establish and strengthen corporate R&D institutions, further improve technology development and the ability to absorb scientific and technological achievements, pay attention to the construction of a scientific and technological talent team, establish a mechanism to cultivate and give full play to the role of outstanding talents, strengthen the work of professional skills monitoring stations, ensure capital investment in technological innovation, actively apply for patents, and comply with laws and regulations that protect intellectual property rights. Through this work, a technological innovation system with enterprises as the main body will be built to further improve the independent innovation capabilities of small nitrogen fertilizer enterprises. 3. Suggestions on promoting the 200-kWh ammonia power-saving technology for nitrogen fertilizers, namely the "200-kWh Nitrogen Fertilizer Production Energy Saving Project". Nitrogen fertilizer production is a large consumer of electricity. In 2005, the national nitrogen fertilizer output was 32.007 million tons, and the process electricity consumption was 68.6 billion kWh, accounting for 27% of the national chemical industry electricity consumption. Electricity expenses account for 20-25% of product manufacturing costs. Therefore, under the current situation of tight power supply and rising electricity prices, saving electricity is not only the social responsibility of enterprises, but also an important way for enterprises to reduce costs and improve market competitiveness. In recent years, the nitrogen fertilizer industry has made great progress in technological advancement. Many companies have made great efforts to save energy and reduce consumption, and have achieved good economic benefits by saving electricity. Here, on the basis of carefully summarizing advanced experience, we propose the "200-degree Electricity Saving Project for Nitrogen Fertilizer Production". This is an integrated transformation measure, which consists of eight sub-items that are technically mature, effective and have obvious effects. Its main contents include: 1. Waste heat power generation. The "three-gas" waste heat boiler and the slag-fired and coal-fired boiler are used to generate steam by blowing air from the gas generator, synthetic purge gas after isobaric recovery, and storage tank gas. The steam is generated first and then extracted for gas generation and urea. A ton of ammonia can generate electricity at a differential pressure of 220 degrees. 2. Reduce ammonia synthesis pressure. Using a new ammonia catalyst and optimizing the synthesis conditions, the net ammonia value increased by three percentage points. ； Using a large-diameter ammonia synthesis tower, the ammonia synthesis pressure is reduced from 31.4 to 20-26Mpa, and 100 degrees of electricity can be saved per ton of ammonia. 3. Purification process transformation. Using the alcohol hydrocarbonization or methanol methanation process to replace the copper washing process can save 50 degrees of electricity per ton of ammonia. 4. Low energy waste heat absorption refrigeration. A lithium bromide refrigeration unit is used to refrigerate the urea vapor condensate and the hot water waste heat of the first-suction cooler to produce refrigerant water for compressor process gas suction stage cooling, propylene carbon lean liquid cooling, and gas cooling before synthetic ammonia cooling. A ton of ammonia can save 110 degrees of electricity. 5. Pressure swing adsorption decarbonization. Under the pressure condition of 1.7Mpa, pressure swing adsorption decarburization replaces propylene carbon solution decarburization and can save 60 degrees of electricity per ton of ammonia. 6. The turbine unit recovers power. By using the turbine unit to recover the energy of the decarbonized rich liquid, one ton of ammonia can save 12-36 degrees of decarbonization pump power consumption. 7. Increase transformation pressure. The conversion pressure is increased from 0.8Mpa to 1.7-2.1Mpa, and a ton of ammonia can reduce the gas compression work by 50 degrees. 8. Frequency conversion speed regulation of the machine pump. Pumps such as methylammonium pumps, liquid ammonia pumps, fans, coal feeders, and grate machines adopt variable frequency speed regulation, which can save 10 degrees of electricity per ton of ammonia. It can be seen that the actual power-saving effect of these technologies is far more than 200 kilowatt-hours per ton of ammonia. However, due to the different scales, products and technologies of nitrogen fertilizer companies across the country, or some measures have been partially implemented, the power-saving effects are not exactly the same. We calculated based on the power saving of 200 per ton of ammonia. If half of the enterprises in the country implement this project measure, the country can save 8 billion kilowatt hours of electricity every year. If the electricity price is calculated at 0.3 yuan/kWh, the production cost of synthetic ammonia per ton can be reduced by 60 yuan. A synthetic ammonia plant with an annual output of 100,000 tons can generate annual benefits of 6 million yuan. Due to the adoption of these measures, not only will there be an energy saving effect, but also because the raw gas utilization rate and compressor output will be significantly improved, the annual production of ammonia can be increased by 6,000 tons, and the profit can be increased by more than 6 million yuan. At present, we have reported the recommendations of the "Nitrogen Fertilizer Production Electricity Saving 200 Degree Project" to relevant departments, hoping to gain some support. In addition to the above-mentioned current power-saving measures for nitrogen fertilizer production, there may be some better power-saving measures that have not been included in this project. I am also soliciting your opinions here and hope that you can put forward more and better suggestions. :lol

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Brothers on the 5th floor, could you please scan and upload the information so that everyone can share it? Thank you so much, like a torrential river!

Can the poster send you a copy? Thank you. My email is 20lxy08@163.com. It is urgently needed.

Fully understand and develop the potential of increasing production and saving energy in aqueous solution full-circulation urea equipment Summary by Qian Jingqing, Chief Engineer of the original Xiangjiang Nitrogen Fertilizer Plant: The article introduces the 40-year technical development experience of the aqueous solution full cycle process urea unit in China, and details the production increase and energy-saving processes and equipment used in the process of technological progress. On this basis, the author proposes a new aqueous solution full cycle process with a steam unit consumption comparable to that of the stripping process unit, which efficiently recovers heat energy. Preface The author has devoted his life to the production technology and technology development of aqueous solution full cycle urea plant. Since 1958, it has been implemented in the urea pilot plant of Nanjing Fertilizer Company. * and study abroad * The urea production process has been around for 48 years, of which the first 28 years were spent in medium-sized urea plants, engaged in production command and technology development. ； Since 1986, he has been engaged in the guidance of production and technology development of small urea plants. Since small urea plants have always had an objective need to continuously increase production, this gives the author an excellent opportunity to study and explore the potential of small urea plants to increase production and save energy. Thanks to the cooperation of many small urea plants, the author combined the practical experience in the mid-urea plant and constantly summarized and improved the production practices of each small urea plant. The 40 years of technological development and development of the aqueous solution full cycle process in China is no longer the backward process with high energy consumption in the 1960s. In practice, we have a full understanding of the two advantages of the aqueous solution full cycle urea device. The author expects that there will be 192 sets of aqueous solution full cycle urea process units in my country, and there will be about 150 sets of original small urea units. Among them, a large proportion of the single unit production capacity will be developed from the original 60kt/a to 180-200kt/a. ； The original 110kt/a urine device has been developed to 260-300kt/a ； The newly designed 200kt/a device of Yuanhua Fourth Hospital can reach 300kt/a, which is a consensus among factory colleagues: (1) Only the aqueous solution full cycle process device can expand the production capacity by 1-2 times through a small number of technical transformation measures and low investment in technical transformation. ； (2) While increasing production, the existing heat energy recovery technology is used to increase the heat energy recovery rate for generating methylammonium, and the steam consumption has been reduced to 1105-1110kg. The author's newly developed technology can reduce steam consumption to less than 900kg without the need for high-pressure circulation loop modifications. It is expected that this technology can be shared and used by many factories with full-circulation aqueous solution process equipment. The investment in technical transformation only requires 2 to 3 million yuan (each urea plant can independently carry out technical transformation), which can achieve high benefits of increasing production and saving energy. In this article, two advantages of a full-circulation urea plant for aqueous solutions will be explained step by step. 1． It is hoped that many colleagues engaged in urea production will be fully aware of the technical advantages that exist in the design of small urea plants. 1.1 Adopt pre-distillation process The technology introduced in my country from the Dutch Stamicarbon Company in 1966 is the pre-separation process. Before the development of the small urea unit, design and research units had been debating whether the first stage of the decomposition system should adopt a pre-separation process or a pre-distillation process. They believe that since the pre-distillation process cannot save steam, it is better to engage in pre-separation. Therefore, in addition to the second version of Zhongnuo's design (about 1973), which used the pre-distillation process developed on the urea pilot plant of Nanhua Company, the subsequent third and fourth versions of the design still used the pre-separation process. However, medium-sized urea plants have realized the superiority of the pre-distillation process in practice, and most plants use pre-distillation towers instead of pre-separators. When it comes to small urea plants, engineering designers engaged in the design of small nitrogen fertilizers have already affirmed the advantages of this process. Compared with the pre-separation process,: 1.1.1 As the temperature of the pre-distilled gas drops to 125°C, compared with the original 160°C one-point gas, the amount of water vapor entering the first-stage recovery system is reduced, which is beneficial to the water balance of the system. Therefore, the water consumption in the first and second stages of absorption can be increased, improving the stability of the first and second-stage absorption operations. 1.1.2 The total process water circulation volume is reduced, the H2O/CO2 molecular ratio of the material entering the synthesis tower can be controlled at 0.65, and the conversion rate of the urine tower can reach 67%. 1.1.3 Due to the increase in water absorbed in the second stage, the CO2 component in the diuretic liquid can be reduced to 16-18%, and the gas-liquid balance pressure of the dimethyl liquid is reduced. Therefore, the operating pressure of the second stage can be reduced, and the temperature of the second stage can be reduced to 135°C for operation. The value-added value of diuretic shrinkage in the second stage is almost zero, which improves the rate of high-quality finished products. 1.1.4 Due to the heat and mass transfer in the pre-distillation tower, the steam consumption per minute is reduced. During the pre-separation process, since the conversion rate is 63%, the steam consumption per minute is 900kg/tur. ； During the pre-distillation process, since the conversion rate reaches 67%, the steam consumption per minute is 540 kg/tur. The measured steam consumption of the pre-separation process of the medium-sized Lunan Fertilizer Plant in 1981 was 1500kg (the conversion rate of the urine tower was 65%). The measured steam consumption of the pre-distillation process of the Sichuan Fertilizer Plant in 1983 was 1330kg. ； When the Fujian Yongan small urea plant operates at 120kt/a, the steam consumption value is 1380kg. 1.2 Adding an external suction cooler to the first absorption tower. Adding an external suction cooler absorbs the technology of Japan's improved "C" method, which shifts the absorption load of the first absorption tower outward. A ton of urea requires an absorption volume of 0.4m3, so the space between the tubes of the external cooler becomes the volume for absorbing CO2, thereby increasing the production capacity of the first absorption system, reducing the absorption load in the first absorption tower, and reducing the amount of reflux ammonia. The medium-sized device does not have an external cooler. During the pre-separation process, the amount of reflux ammonia at the top and bottom of the first absorption tower and urea per ton is 2.0 m3 ； There is an external suction cooler in a small device, so bottom reflux is not needed. The amount of ammonia used for refluxing urea per ton depends on how much heat is taken out by the external suction cooler, which is between 0.6-0.8 m3. After the production load of the entire absorption system is increased, there is no need to increase the area of ​​the ammonia condenser, because the role of a 1 m2 suction external cooler is equivalent to 5 m2 of an ammonia condenser. Make good use of the first-suction external cooler. When the production capacity of the device is increased, the circulation volume of desalted water must be increased. Simply increasing the area of ​​the first-suction external cooler is not enough. And twist-shaped aluminum strips should be added to each cooling tube to increase the turbulent velocity of the water, thereby improving the heat transfer system and removing the heat generated by methylammonium. The temperature of desalted water is controlled at 90-95°C so that there is no risk of crystallization of concentrated methylammonium in an external suction cooler. The upper limit is to adjust the temperature of water to 95°C. If it is circulated at 95-100°C, the circulation volume of the pump will decrease due to vaporization, and the temperature at the bottom of the absorption tower will rise. Setting up or adding an external suction cooler is an effective measure to improve the production capacity of the urea plant absorption system, and at the same time, the heat energy recovery rate is also increased accordingly. The desalted water volume of the cooling cycle should be able to remove the corresponding heat load. In this desalted water circulation system, a cold desalted water volume of 2.5 m3/tur can be supplied, the water supply pressure is not less than 0.4MPa, and the desalted water circulating volume should be 20-25m3/tur to configure a circulating water pump of corresponding capacity. An external suction cooler can not only reduce the amount of absorption absorbed by the bubbling section of the first absorption tower, but also improve the operating conditions of the fine washing section of the first absorption tower, reducing the amount of CO2 absorbed by ammonia water in the upper part of the tower, preventing methane ammonium from being saturated and entering the solution stratification zone, causing methane ammonium to crystallize and precipitate, thus improving the operational stability of the first absorption tower. Another area where the small urea device can improve production capacity is the heat energy utilization section of the evaporation heater. The design unit only calculated the heat energy utilization, and did not calculate the heat of methylammonium generation by absorbing CO2, and did not calculate the absorption capacity of this section. Therefore, without any modification, the original 60kt/a small urea unit can reach 80kt/a. By adding a suction external cooler of the same area, the output can reach 100kt/a. 1.3 Process improvement of dimethyl liquid in the first-stage absorption system In the pre-distillation process, the CO2 content in dimethyl liquid can be reduced to 16-18%. It is first sent to the heat utilization section of a steam heater, then to an external suction cooler, and then to the bubbling section of a suction tower. This can make full use of the space between the tubes of the first steam heating utilization section and an external suction cooler to absorb NH3 and CO2, and remove the heat generated by methylammonium. They are two parts of the pre-distillation process unit that can both increase production and improve the heat energy recovery rate. At present, a few factories have not controlled the operation of reducing the dimethyl liquid component, and the control is between 18-20%. After the medium-sized equipment was changed to the pre-distillation process, the dimethyl liquid component was not reduced from 20%. This is an inappropriate operating process and fails to achieve the benefits of increasing production and saving energy. 1.4 One-point heater The one-point heater is a rising film tube heater with an orifice added at the bottom of the tube. This technology was hosted by the former Chemical Fertilizer Division's Central Nitrogen Division when conducting technical exchanges with Stamicarbon Company. The company provided this technology that saves energy and reduces the added value of biuret in one minute. The orifice technology allows urine to enter each row of tubes evenly at the bottom sealing head. The urine is already in a boiling state. After being introduced into the tubes through the orifice, the flow rate is increased, causing the fluid to rise as a liquid film, and the liquid side heat transfer coefficient value increases. This can save steam, reduce the residence time of the material in the tubes, and avoid back-mixing of urine in the original tube heater, thus reducing the value-added amount of biuret. If there is no orifice, the urine will rise greatly from the middle tube. When it reaches the upper end of the tube, due to the temperature difference between the urine, a large amount of low-temperature urine can flow back into the tubes on the periphery of the heater, forming a back-mixing of the circulating flow. The combination of the one-point heater and the pre-distillation process device can reduce the area of the one-point heater, that is, the one-point heater can increase the production capacity under the same area. In the second version of the design of the small urea device, the one-point heater area is increased to 94m2, which is larger than that of the medium urea predistillation device. The area is larger than the tons of urea in the process device. Moreover, the pre-distillation process is adopted and the bottom end of the tube is equipped with a throttling hole. Therefore, 94m2 can pass 360t/d output. If a pre-separator is added, it can pass 420t/d output. The requirements for good use of One Point Plus are that the secondary anti-corrosion air added at the bottom of One Point Plus must remove oil mist, otherwise oil scale and carbon deposits will be produced on the surface of the tubes, which will affect the heat transfer effect. However, in the current small urea unit, the one-point column tube is scaled and difficult to clean, so the orifice has been removed and the heat transfer effect due to scaling is poor. When increasing production, the area of ​​the one-point column is increased, and no orifice technology is used. As a result, the steam consumption increases while increasing production. All heaters in the urea plant adopt the rising film type, which has its unique advantages. When the output increases, due to the increase in the upward flow rate of the material, the heat transfer coefficient increases. In the same area, the output can be doubled, and high-quality urea can be obtained in the evaporation system. As for the corrosion of evaporator heater tubes, most of them have now adopted titanium or titanium alloy materials that are resistant to erosion and corrosion. 1.5 The desorption tower is equipped with a reflux condenser. The top of the desorption tower is only filled with ammonium bicarbonate liquid without heat exchange (called cold flow), and the temperature at the top of the tower is controlled by adjusting the cold flow rate, as well as other design factors. The adaptability is poor and the operation flexibility is small. The desorption system of the small urea plant is equipped with a reflux condenser, and the reflux condensate is used as the reflux liquid in the 1-6# distillation section at the top of the desorption tower. Therefore, it is more convenient to control the temperature after desorption and condensation at 112°C. The water vapor content in the desorption gas is relatively stable, which is very beneficial to the stable operation of two circulations and one cooling. The cooling water of the reflux condenser is 95-100°C hot water from the first suction external cooler, and the outlet water temperature is 105°C. Since the reflux condenser is at an altitude of 24m, the hot water flows automatically to the boiler room according to the level difference. A ￠700mm desorption tower, 1 A 6m2 reflux condenser can desorb 7-8m3 of ammonium bicarbonate liquid per hour. The waste liquid discharge indicator does not exceed the design value. Many factories also send the dilute ammonia water of the scrubbing liquid of the refined gas of the synthesis system to the desorption tower for desorption, which can desorb 10m3 per hour. 1.6 The inert scrubber is equipped with an explosion-proof space in the separation space above the inert gas scrubber. The separated gas contains a large amount of hydrogen (about 30-35%) and about 10% oxygen, which is an explosive gas. As long as there is a trace detonation source, a chemical explosion will occur. About 1/4 of medium-sized urea plants have experienced explosions in different parts in the early stage, and the explosion probability is greater in the separator part of the inert scrubber, so small urea devices are commonly used It is designed to install an explosion-proof plate at the separator of the inert scrubber. The space above the plate is an explosion-proof space. The gas from ammonia condenser A (containing 80% ammonia in the gas) passes through the explosion-proof space and reaches ammonia condenser B. Gas with a high ammonia partial pressure is used as the explosion-extinguishing gas source. Once an explosion occurs, the explosion-proof plate ruptures. After the explosive gas enters the explosion-proof space, the explosion will be stopped due to the dilution of a large amount of ammonia to avoid a crushing explosion at the separation part of the inert scrubber. Due to design reasons, the explosion-proof panel will break if there is a slight physical pressure difference, affecting its use. Sichuan Chuanhua Group Co., Ltd. has improved the installation method of explosion-proof panels to avoid rupture of explosion-proof panels and truly play an explosion-proof role. 2. Development progress of small urea plant technology 2.1 Development of pre-separation-pre-distillation process technology In 1983, the original pre-separator was restored in front of the pre-distillation tower in the secondary urea plant of Qilu No. 1 Chemical Industry Co., Ltd. At that time, the secondary urea plant did not have an external suction cooler, and the pre-separated gas directly entered the bubbling section of a suction tower for absorption. Looking back now, this process did not have a major impact at that time, and only Lanhua and Juhua plants were improved. The reason is that the original pre-separator has a small volume (￠800×2600, V=1.3 m3), and the pressure in the pre-separator rises during operation, and the pre-separation effect at the design pressure of 1.7MPa cannot be achieved. ； Secondly, the pre-separated air directly enters the first suction tower without the function of an external suction cooler. In terms of operation technology, although the medium-sized plants at that time changed to the pre-distillation process, they did not realize the superiority of the pre-distillation process and adjust the process indicators. If the CO2 component of the dimethyl liquid remains at 20%, it will still enter the first absorption tower directly. The dimethyl liquid component of the small urea plant drops to 16-18%. This dimethyl liquid is first sent to the first steam heating and utilization section, and merges with the pre-distilled gas. The partial pressure of CO2 gas rises to 18.6%, resulting in more methylammonium reactions. Then it enters the first suction external cooler and absorbs 92% of the ammonia in the pre-distilled gas. Because of the reaction of CO2, 80% of the total CO2 in one gas is absorbed in front of the first absorption tower (calculated based on the heat energy recovery rate). The increase in heat energy recovery rate also reduces the heat load of the first absorption tower. The amount of urea reflux ammonia in one absorption tower is reduced from 2.0M3 in the pre-separation process to 0.6M3. Therefore, after the pre-separator was restored in the intermediate urine unit at that time, the advantage of recovering the heat generated by methylammonium in this process was not fully demonstrated. However, due to the splitting effect of the pre-distilled gas and the pre-separator in the first-stage decomposition system, the overall pressure of the first-stage system dropped, which was beneficial to the first-stage decomposition rate. At that time, the intermediate urine device did not restore the pre-separator to improve production capacity. It just believed that the gas phase material separated by the pre-separator did not need to be heated to save steam consumption, and the water vapor partial pressure in the pre-separated gas phase was low and the water absorbed by the first stage could be reduced. The two sets of small urea plants in Shandong Mingshui are small urea plants that use pre-separators with a volume of 3.5M3 as recommended by the author. It is introduced that the installation height difference of the pre-separator in Qilu Yihua is 18 meters higher than that of the pre-distillation tower. These data are raised to question the installation height difference of the original design research unit which is only 5 meters or 7 meters, making the installation height difference of this plant 12 meters. It is also the first factory to put the pre-separated gas into the first suction external cooler and then into the first suction tower. (The original design of a certain hospital has a pre-separator and a suction external cooler, but the pre-separated air still enters the first suction tower). After the pre-separator was added to the two sets of devices, the steam consumption was significantly reduced, which was reflected in the decrease in the steam side pressure in the first heater. There is still a pressure balance valve installed on the pre-separated gas phase pipe. When the production load of the device is low, the two sets of devices can save steam. When the load of the two sets of devices was increased, the position difference was less than 15 meters, and the pre-separated gas phase tube was still ￠139 tube without enlargement. Therefore, the pressure balance valve of the old system is fully closed, while the pressure balance valve of the new system can only be opened a little, thus losing the function of the pre-separator. The author analyzes this situation and believes that it is not a problem with the pre-separation-pre-distillation process, but the result of not installing the pre-separator properly. The author believes that the installation of the pre-separator must meet two process requirements. One is to ensure that during the production process, the pressure inside the pre-separator must be close to the design pressure 1.7MPa in order to be close to the design value of the pre-separation efficiency. For this reason, the volume of the pre-separator and the diameter of the pre-separated gas phase pipe must match the corresponding production load. Unnecessary resistance losses should be eliminated during the process, such as canceling the pressure balance valve on the pipeline to reduce the actual pressure in the pre-separator. Second, the pre-separator and pre-distillation tower must have a sufficient head difference when installed. In the absence of a pressure balance valve on the pre-separation gas phase pipe, the pre-separated liquid can flow smoothly into the pre-distillation tower. Therefore, in the second plant, under the production load at that time, the pre-separator still used 3.5M3, the installation height difference was 15 meters, and the pre-separator gas phase pipe diameter was ￠159, which is the same as the pre-distillation gas phase pipe diameter. There was no pressure balance valve installed on the pre-separator gas phase pipe. The system logistics was normal, and the raw steam consumption was 1380kg. After installing the pre-separator, the steam consumption was 1280kg. To implement supporting measures for this process, it is necessary to adjust the area of ​​the first suction external cooler and the temperature-regulated desalted water circulation volume of the first suction external cooler, because the amount of CO2 absorbed increases. If the temperature of the gas-liquid mixture rises and the ability to absorb CO2 decreases, the amount entering the first absorption tower increases, making the operation of the first absorption tower difficult. 2.2 After adding a pre-separator, why does the steam consumption decrease? The design pressure of the pre-separator is 53% under the design pressure of 1.7MPa. The decomposition rate of methylammonium is 15%. The partial pressure of ammonia in the pre-separated gas phase accounts for 92%, CO2 accounts for 3.5%, and H2O4.5%. Therefore, the pre-distilled gas The NH3/CO2 ratio in the medium is reduced from the original 8.03 to 3.94. The pre-distilled gas with a reduced NH3/CO2 ratio is condensed in the first steam heating and utilization section. The NH3/CO2 ratio in the condensate also decreases, which increases the boiling point of the solution. As a result, the shell temperature of the heat exchange section is increased and the heat exchange amount is increased. ； At the same time, the partial pressure of CO2 in the pre-distilled gas increased from 10.4% to 18.7%, which increased the driving force for the liquid to absorb CO2. The author used the concept of water balance in the operation process to adjust the amount of water added in the second circulation and first cooling, so that the CO2 content in the dimethyl liquid dropped to 14-15%. The amount of CO2 absorbed in the first steam heating and utilization section increased, and the heat exchange rate also increased. Since the pre-separated gas containing 92% ammonia is introduced into the first suction external cooler, more residual CO2 in the first gas from the first steam heating and utilization section can be absorbed, and the amount of CO2 entering the first absorption tower is reduced. This process can reduce the amount of reflux ammonia per ton of urea in the first absorption tower to 0.35m3. In the first stage of the decomposition system, due to the installation of the pre-separator, about half of the gas volume after decomposition of the material coming out of the synthesis tower is the pre-separated gas phase volume, that is, 53% of the excess ammonia does not enter the pre-distillation tower, so it enters the pre-distillation tower. The amount of material decreases, and after passing through the pre-distillation section, a large amount of gas phase enters the pre-distillation gas phase, and the amount of material entering the one-minute addition will decrease significantly, and the steam consumption of the one-minute addition will also decrease at any time. An example of the decrease in the amount of material entering the one-minute addition is: When the original small urea unit was expanded to more than 100kt/a, the material pipe at the bottom of the pre-distillate was replaced to ￠159. After using the pre-separator, when the pre-separation efficiency was high, serious corrosion occurred in this pipe. This corrosion condition occurred in many plants. Only by reducing the pipe diameter and using ￠108 pipes can the corrosion problem be solved. This was caused by periodic cavitation corrosion in the original ￠159 pipe when the liquid level dropped to the pipeline. At the same time, serious corrosion occurred in the packing or trays in the pre-distillation section due to lack of oxygen. The first time the author encountered this working condition was at the Shanxi Jincheng Chemical Plant with a 200kt/a pre-distillation unit. When the unit was installed, the author suggested adding a pre-separator. Because the daily output of the plant was low, about 600t/d, steam corrosion occurred in the ￠159 pipe. ； In Shanxi Linyi Plant, in the same device, after adding a pre-separator, due to the daily production of 750 t/d, no corrosion problems occurred in the ￠159 pipe. It can be analyzed from this that the pre-distillation gas phase temperature is 115°C, which is caused by 53% excess ammonia being separated in the pre-separator. If it enters the pre-distillation tower and the pre-distillation outlet temperature is 125-130°C, the total enthalpy value in one part of the gas will increase. This part of the heat is provided by one part of the added steam. Therefore, the steam consumption of one minute of addition has decreased, and this reduction value should be the difference between the enthalpy value of the total amount of one minute gas and the heat enthalpy value of the pre-divided gas phase at 115°C. At the same time, due to the split flow of the two gases, the overall pressure of the first-stage system decreases, and the first-stage decomposition rate and total ammonia steaming rate increase. The first-stage decomposition rate and total ammonia steaming rate can be achieved without heating to 160°C. 2.3 The author's technical transformation process of reducing the steam consumption value to 1050kg in small urea plants. Since small urea plants have the requirement to continuously increase production capacity, there are already many single-set units with a capacity of 180-200kt/a. Through continuous practice, the author and many factories have gradually improved the capacity of a single unit and gradually reduced the steam consumption value to 1050-1100kg. 2.3.1 Use the pre-separator well. Set up a pre-separator in front of the pre-distillation tower. It was first used in the design of the Shandong Provincial Institute in 1986. Later, the pre-separator was used in the SHS energy-saving process and the self-stripping one-stage tower process. According to various reports or field investigations, the author found that the pre-separation efficiency did not reach Based on the original design value level of the Fourth Chemical Hospital, and based on the installation situation of the pre-separator after the medium-sized unit was changed to the pre-distillation process, it was analyzed that the pre-separator must first be installed so that the actual pressure of the pre-separator during operation must be close to the design value of 1.7MPa to obtain the designed pre-separation efficiency. Therefore, when setting up the pre-separator, it is necessary to have an appropriate volume and pre-separated gas phase pipe diameter. No heat exchange equipment is installed in the pipe path. There is no pressure balance valve on the pre-separated gas phase pipe. The gas phase pipe diameter must match the corresponding production load. The installation position difference must be greater than the position difference between the pre-separator and the pre-distillation tower. In the process where the pre-separator is set up by the author in the small urea plant, the pressure of the pre-distillation tower is 0.1MPa greater than the pressure of the pre-separator (actual measured value), and the theoretical head difference is 10 meters, so it is reasonable to set 15 meters during installation. Materials can circulate in the actual process. The position difference value of 15 meters has been agreed upon by many manufacturers and in the design of new energy-saving processes. 2.3.2 The supporting measures for increasing production in this process device are the area of ​​a steam heating utilization section and the area of ​​a suction external cooler that are suitable for the production load, which can play a dual role. For example, increasing the area of ​​the first steam heating and utilization section can not only increase the absorption capacity and evaporation capacity of the first section, but also increase the recovery rate of the heat energy of the ammonium methane section. When increasing the area of ​​the first steam heating and utilization section, it must be considered that the flow rate of urine in the tubes should not decrease, otherwise the K value will decrease and the heat exchange rate will decrease. The tubes of the first-suction external cooler are originally equipped with twisted aluminum rods to increase the flow rate of circulating temperature-controlled water in the tubes and increase the K value on the water side. When many factories increase the area of ​​the first-suction external cooler, they do not install twisted aluminum rods and do not increase the circulation volume of the temperature-controlled water. Simply increasing the area (usually adding one unit) will not have a big effect. When increasing the output of the device, such as adding an external cooler, the circulating water volume of the two external coolers must be increased. If a large-capacity pump is replaced, a larger-diameter water pipe needs to be replaced. It is best to use one pump to one cooler as a circulation system to increase the circulation volume of temperature-adjusting water. The pre-separated gas phase pipe line should not be connected in series through two external coolers and connected to the original external cooler close to a suction tower. The diameter of the connected pipe should be enlarged accordingly, and the corresponding desalted water circulation volume needs to be increased in the other coolers. During the technical transformation to increase production, some plants only installed pre-separators, but did not accurately grasp some of the specific experiences put forward by the author in practice. After increasing production, steam consumption increased, and the amount of reflux ammonia in the first absorption tower increased, causing the ammonia condenser to operate overloaded, and the opening of the first-stage pressure regulating valve increased, gradually causing ammonia consumption to increase. 2.3.3 Utilization of high-pressure steam condensate waste heat and increasing urine flash heater Adding urine flash heater is a need for the evaporation system to improve the overall production capacity. In the pre-distillation process unit, the urine concentration after the second stage decomposition is 66.9%, which is one of the important signs of the system's process water balance (the pre-separation process is 70%). After the original simple flash separation, 70% of the urine is obtained (the pre-separation process is 74%). The author inserts a flash heater in the pipeline before the flash separator to reduce the resistance loss of the urine in the pipeline after bisection, so that the bisection tower can enter the flash separator at 0.25MPa. The heat source comes from the high-pressure steam condensate passing through 0.6MP * * 0.6MPa steam from the intermediate flash evaporation tank. Under a certain production load, with a suitable flash heater area, its heat supply and demand are balanced. The intermediate expansion tank at 0.6Mpa can flash out 15% of the steam volume of the condensate. According to on-site observations, after a factory uses this waste heat utilization measure, the urine concentration after flash evaporation can reach more than 74%, which can improve the production level of the evaporation system and save 80kg/tur of urea steam consumption. The original steam consumption of the plant was 1380 kg/tur. After installing the pre-separator, the steam consumption dropped to 1280 kg/tur under the same production load. After adding a flash heater, the steam consumption dropped to 1200 kg/tur. 2.3.4 While increasing the production capacity of the first-stage absorption system and evaporation system, the steam consumption is further reduced to 1050 kg/tur. When improving production capacity, the author tries his best to tap the production potential of existing equipment, with the premise of adding as little equipment as possible. Based on the above practice, it is considered that as long as the area of ​​a steam heating utilization section and a suction external cooler is increased, the absorption volume of the section is increased. At the same time, the production capacity of the evaporation system is also increased, and the heat energy recovery for generating methylammonium is also improved. When the device capacity reaches 180t/a, the steam consumption per ton of urea drops from 1200 kg/tur to 1050 kg/tur. This 1050 kg/tur steam consumption also includes the overall scale benefit after the production scale is expanded. During the practice of this plant, the author got the consensus from Sanming, a medium-sized urea plant in Fujian. Sanming is the original 110 kt/a unit. It has added technological measures to increase the production of urine towers. In 1999, it adopted the technology of adding a pre-separator. At that time, flash heaters that utilized waste heat had not yet been used. In the technical summary of the plant, it was reported that the annual output of the device in 2001 was 260kt/a, and the steam consumption was 1100kg. It is recommended that the plant use a flash heater that utilizes waste heat, and the steam consumption will be reduced to 1050kg. This technical transformation is simple, does not change the original production process and production conditions, and the investment in technical transformation is very low. It can be solved by the current self-raised funds of small and medium-sized urea plants. 2.3.5 The conversion rate of the synthesis tower must reach 67%. During the production increase process of the unit, the conversion rate of the urea synthesis tower cannot be less than 67%, otherwise the steam consumption per minute will increase. After increasing production, the production intensity of the urine tower increases. Generally, high-efficiency trays or new synthetic tower internals need to be used. If the production increase is higher than the production intensity of a single tower I=20, double towers must be used. When using twin towers, according to the author's investigation, when the production intensity I ≤ 14 in the twin towers, there is no need to use high-efficiency trays. Only 12 traditional trays (which can reduce the height of the non-tray section at the top of the tower) and 3 cyclone plates are used. For example, in a ф1400 urine tower, 5 cyclone plates need to be installed. The cyclone plate installation interval is preferably 400mm, and the tray spacing is preferably 1000-1500mm, otherwise it will affect the conversion rate. 2.4 There are several innovative technologies to improve the technical level of the aqueous solution full cycle urea unit. 2.4.1 Development of high-efficiency synthesis trays. Small and medium-sized urea towers in my country all use traditional porous sieve plates. With the need to increase the production capacity of small urea units, new trays have been developed. Bubble-type bubble caps are added to the trays to increase the probability of gas-liquid phase contact reactions and accelerate the diffusion rate of reaction heat, thereby improving the completion of the first reaction. In addition, it is necessary to increase the number of installed trays with a plate spacing of 1m to increase the reaction section in the tower. Therefore, under high production intensity (I≥20), the conversion rate is not less than 65%. Based on the new understanding of the urea synthesis reaction mechanism, a variety of new trays and new internal parts that can improve the urea synthesis conversion rate have been developed, aiming to improve the production intensity of the synthesis tower and reduce the energy consumption of the device. In recent years, the technology of synthesis tower internals has progressed rapidly, playing a positive role in reducing the energy consumption of traditional process equipment. The emergence of high-efficiency trays in the synthesis tower has deepened our understanding of factors affecting conversion rate. The diameter of the small urine tower is ф1200mm, and the volume of 17 m3 is equipped with 6 plates (3 cyclone plates, 3 porous plates), 20 m3 is equipped with 7 plates (3 cyclone plates, 4 porous plates), 24 m3 is equipped with 8 plates (3 cyclone plates, 5 porous plates), and 26 m3 is equipped with 8 plates (4 cyclone plates, 4 porous plates). The increase in reaction volume only increases the height, but does not increase the number of trays. Therefore, for a urine tower above 20 m3, about 2/5 of the space in the upper part of the tower is empty. The empty tower section has a great impact on the conversion rate. Under the designed production intensity (generally I=7-8), the conversion rate reaches 67% with a longer conversion time. As the production intensity increases, the conversion rate decreases. ； When the production intensity reaches 11, the conversion rate is lower than 60% ； When I reaches 14, the conversion rate rises to 64% instead, which shows that the rising speed of the materials in the tower increases and reduces the degree of backmixing in the empty tower section in the upper 2/5 of the tower. When I90%, ​​the average particle size is 1.95mm, the blanking temperature can meet the relevant packaging requirements. ② For daily output less than 500 tons, the tower diameter is above Φ12mm, the particles of 1.6-2.8mm are >80%, the average particle size is 1.85mm, and the temperature can meet the packaging requirements in summer. From the above report, it can be confirmed that the Φ12m tower device can use LP-type nozzles, which are the best nozzles for small and medium-sized urea devices to solve the granulation problem. 3. A new aqueous solution full cycle process that efficiently recovers heat energy. After the author improved the traditional process device with the pre-separation-pre-distillation process, the steam consumption per ton of urea has been reduced to 1050-1100 kg. This new process is based on this and is further developed to further recover the reaction heat of methylammonium in the medium-pressure circulation system, which can reduce the steam consumption per ton of urea to less than 900 kilograms. This new process uses two utility model patents that the author participated in: ZL99233018.1 Urea synthesis tower with heat exchanger internals, ZL0227385.1 New process for recovering heat energy in urea production. This process can increase the output of traditional process equipment by 1-1.5 times, and the steam consumption is comparable to that of steam stripping process equipment. Since it does not use high-pressure circulation loop modification, the investment in technical modification is low, and it is suitable for the technical modification of current small and medium-sized urea plants. Using the mature pre-separation-pre-distillation process to further develop it, the technology is simple, easy to implement, safe and reliable, and there is no need to bear the initial risks associated with using other technical modification processes. 3.1 Technical basis for new process development The author has analyzed and confirmed through practice that the traditional aqueous solution full cycle urea plant has the advantages of increasing production and saving energy after adopting the pre-separation-pre-distillation process. During the development, the first thing I thought about was that the operating pressure of the pre-separator should be close to the design value, so that improving the pre-separation efficiency is the first priority. The installation distance difference of medium-sized devices is set at more than 15m. According to the author's actual measurement on a certain device, the pressure difference between the pre-separator and the pre-distillation tower (according to the author's process flow) is 0.1MPa, so there must be a certain margin during specific implementation. The author takes 15m, and this empirical value has been confirmed on many devices. The pre-separated gas and pre-distilled gas must be separated, not only to improve the production capacity of the sub-system, but also to bring out the advantages of their different components. Special effects can be produced in the respective heat exchange equipment. Therefore, the installation of the pre-separator must pay attention to achieving the highest pre-separation efficiency. Without pre-separation efficiency, the respective advantages of the two gases cannot be exerted. Increasing the first steaming area and adding a flash heater that utilizes waste heat are important elements in the author's overall technical transformation ideas. This measure can not only improve the production capacity of the device, but also reduce energy consumption. Increasing area and increasing production capacity must match each other to achieve better results. 3.2 Technical content for further development 3.2.1 In the first step of energy-saving technical transformation, the heat energy recovery rate of the CO2 gas generated in the first stage of the decomposition system is only increased in the first steam heating and utilization section and the first suction external cooler. Therefore, to develop a new heat energy recovery work, it is necessary to extract part of the CO2 that originally entered the synthesis tower reaction and send it to a section of heat energy recovery equipment that requires high energy. That is, a heat energy utilization section is added to the first section to reduce the steam consumption of the first section and increase the area of the original first steam heating and utilization section to reduce the steam consumption of the first section of evaporation. Through calculation, the heat energy recovered in these two parts can reduce steam consumption by 300kg, reducing steam consumption per ton of urea from the current 1050-1100kg to 800-900kg. 3.2.2 Improving the conversion rate of the urea synthesis tower is one of the important factors in reducing steam consumption in the new process. Due to the increased amount of methylammonium in the new process, the following two process conditions must be used when calculating process materials.: (1) The H2O/CO2 ratio entering the tower should not exceed 0.85. Therefore, the absorption water in the first and second stages can be used multiple times and the CO2 added by the medium-pressure system can be absorbed. (2) The composition of the methylammonium liquid should be kept consistent with the traditional process, so as not to increase the equilibrium pressure of a section of the system, so as to avoid causing changes in system operating conditions and causing adverse consequences. The temperature of the ammonium methane liquid entering the tower is still 95°C, which will not cause increased corrosion of the methane ammonium pump cylinder and its internal parts. Therefore, the H2O/CO2 ratio entering the tower needs to be maintained at 0.85. At present, the highest conversion rate of various domestic urine tower internals is 68% when the H2O/CO2 ratio is 0.65. In this new process, the H2O/CO2 ratio entering the tower increases to 0.85 due to the increase in the methylammonium circulation amount in one stage. Under this working condition, in order to ensure that the conversion rate is not less than 70%, new synthesis tower internals must be designed to ensure that the conversion rate is 70% or above under a high H2O/CO2 ratio. The design guiding principle of the new urine tower internals is an isothermal synthetic tower internals, which can keep the temperature at the top and bottom of the tower basically consistent to improve the conversion rate. The three materials enter the tubular reactor set up in the tower with NH3/CO2 less than 3. This reactor is also a heat exchanger. This equipment is made of high-temperature resistant 25-22-2 material and is fixed under the large cover at the top of the tower. After the reactants are moved from the central tube to the lower part of the tower, liquid ammonia is added until the NH3/CO2 is 4.2-4.3 to balance the reaction heat and improve the conversion rate. For this purpose, it is still necessary to use the existing high-efficiency trays in the tower and use them after slight modification. If the original medium-sized unit does not need to increase its production capacity, and this process is used for transformation, only the amount of CO2 entering the tower is adjusted, and part of the CO2 is fed into each heat exchange equipment at medium pressure, the steam consumption value can also be reduced to the design value. The internal parts of this urine tower are placed at the upper part of the urine tower. The three materials enter the tubular reactor. The first reaction formula is basically completed in this internal part. ； After the reaction, the material is guided from the central tube to the bottom of the tower, and the reaction heat is transferred to the rising molten material in the tower. The rising process of the material is also the process of the second reaction formula. This structure creates a good high-temperature environment for the transformation reaction. Part of the liquid ammonia needs to be added at the bottom of the tower to bring the NH3/CO2 to 4.2 to maintain a balance between the temperature at the bottom of the tower and the temperature at the top of the tower. The temperature at the top of the tower is 186-188°C. High-efficiency trays are also arranged in the tower from bottom to top, so it can be ensured that the conversion rate is not less than 70% (guaranteed value) under the condition of H2O/CO2 0.85. 3.3 Advantages of using new energy-saving technology to transform the existing traditional urea plant. The urea plant that has been transformed using pre-separation and pre-distillation can continue to be transformed according to the new process. The process changes are small, the addition of equipment is small, and the technical transformation project is easy to implement. The early technical transformation project can continue to play a role, but the investment in technological transformation is not big. Therefore, the new energy-saving process is simple and easy to master, is a low-input, high-output solution, and is suitable for the transformation of medium and small urea plants. 4． Conclusion In this article, the author introduced the 40 years of technological development experience of the aqueous solution full cycle process urea unit in China, so that the steam energy consumption is the same as that of the stripping process unit. If we evaluate the advancement of technology in terms of steam consumption, we can say that the Chinese-style aqueous solution full cycle urea process is no longer a backward process. If all the domestically developed new technologies introduced in this article are used in the new design or the technical renovation of the old equipment, the ammonia consumption and quality of urea as well as the safe production of the equipment can be ranked among the world's advanced levels. The author believes that the various energy-saving technologies currently available in China generally require high investment in technological transformation, and some of the effects are not as good as the new cost-saving technologies developed by the author. Moreover, the technical transformation task can be completed by the technical strength of our factory. Therefore, I hope that many urea manufacturers will reach a consensus with the author to transform the backward appearance of the original process equipment.

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