I would like to ask everyone for advice regarding the energy-saving upgrades for medium-sized nitrogen fertilizer enterprises!

30 measures for energy conservation in nitrogen fertilizer plants (provided by HaiChuan; please refer to: http://bbs.hcbbs.com/viewthread.php?tid=348872&page=1#pid1863042). I. Comprehensive renovation techniques for gas generation furnaces: These techniques include expanding the diameter of the gas generation furnace, raising the height of its jacket, moving the outlet pipe, using special grates suitable for different types of coal, and employing frequency converters to control the speed of the furnace bottom’s rotating mechanism, among other comprehensive renovation measures. After modification, the gas production capacity of the gas generator can be significantly improved, and coal consumption can be reduced. 　　II. Rational selection of high-efficiency gas generation blowers It is necessary to carefully select the appropriate blower by taking into account factors such as the diameter of various gas generation furnaces, the type of coal used, the required gas production volume, as well as the resistance associated with the supporting equipment and pipelines in the system. The blower must be capable of meeting the requirements for air supply needed for gas production, while at the same time preventing excessive air flow from leading to an increase in the amount of material carried away by the airflow. 　　III. Automatic coal feeding machine technology This technology helps to reduce downtime, enable continuous gas production, minimize heat loss, shorten the blowing time, increase the gas output per furnace, and contribute to stabilizing both furnace temperature and gas composition. It also reduces the coal consumption per ton of ammonia produced, lessens the workload on operators, and decreases the risk of accidents. 　　IV. Oil-pressure microcomputer control, furnace condition monitoring, and system optimization technologies This technology enables reasonable adjustment of parameters such as the cycle time for gas production, the amount of steam supplied to the furnace, the hydrogen-to-nitrogen ratio, as well as operations like coal feeding and ash discharge. It allows for comprehensive monitoring of the furnace conditions in a gas production furnace and enables closed-loop optimization, thereby improving the operational efficiency of the system and achieving high production levels, stability in production, and reduced energy consumption. 　　V. Use of efficient dust collectors 　Choosing high-efficiency cyclone dust collectors with low resistance can improve the dust removal efficiency of gas, while reducing the loss of dust particles and the wear on equipment pipes. 　　VI. Centralized recovery of waste heat from upstream and downstream gas streams The use of a centralized heat pipe-type waste heat recovery unit designed for multiple gas generation furnaces enables the recovery of waste heat from these upstream and downstream gas streams, which helps to reduce system resistance and improve the efficiency of waste heat recovery. 　　VII. Centralized High-Efficiency Gas Scrubber The use of a centralized, high-efficiency and low-resistance packed gas scrubber replaces the conventional setup of a gas generator paired with a tower-type spray scrubber, which helps to reduce system resistance and improve the efficiency of washing and cooling. It also allows for a reduction of 15% to 20% in the amount of cooling water and wastewater required. 　　VIII. Improving the quality of steam supplied to the furnace The use of superheated steam for feeding into the furnace helps to maintain a stable furnace temperature during the gas production process, increases the steam decomposition rate and the amount of gas produced per furnace by 5%–8%, and reduces the consumption of coal and steam per ton of ammonia produced. 　　IX. Waste heat recovery from purge gas By utilizing the synthetic purge gas for combustion support, a centralized combustion furnace purge gas recovery system is employed to recover the sensible and latent heat contained in the gas used for gas production, thereby generating superheated steam as a by-product. Enterprises with the necessary resources can adopt the three-waste fluidized mixed combustion furnace technology to combine blast air with gas generation slag, recover the by-produced superheated steam, and implement cogeneration, which helps to further improve energy savings and economic benefits. 　　X. Reducing the resistance in the gas generation system As the gas production capacity per furnace increases, it is necessary to increase the diameter of the associated pipes and valves as well. The number of bends in the piping should be minimized, and the flow direction of the pipes must be optimized. Adjustments must also be made to the depth at which the gas pipes penetrate the gas cleaning tower; these measures help improve gas production in the furnace and reduce the electricity consumption of the blowers. 　　11. Installation of high-efficiency electrostatic tar removers High-efficiency electrostatic tar removers shall be installed in front of the Roots pump in the desulfurization section and behind the cleaning tower. The former helps to maintain the quality of the desulfurization solution and improve desulfurization efficiency, while the latter helps to improve the quality of the gas fed to the nitrogen and hydrogen compressors, reduces the frequency of valve replacement due to high tar content in the gas, and extends the effective operating life of the compressors. 　　XII. High-efficiency desulfurization agents and anti-clogging, low-resistance desulfurization towers High-efficiency desulfurization agents such as 888 or 888+tannin can be used, along with low-resistance desulfurization towers that are less prone to clogging. This improves the desulfurization efficiency, reduces the volume of desulfurization fluid that needs to be circulated, and lowers power consumption. 　　Configure a regeneration tank with an appropriate sufficient residence time and nozzles with a sufficient air intake volume. The regeneration efficiency can only be improved by ensuring an appropriate residence time and sufficient air volume, while maintaining the quality of the lean liquid, thereby enhancing the desulfurization efficiency. 　　13. Use of high-efficiency solution filters: This can improve the purity of the desulfurization liquid, enhance the desulfurization efficiency, reduce the operational load on the sulfur melting tank, and save steam consumption. 　　14. Increasing the shift pressure By adjusting the enterprise’s product portfolio and carrying out capacity expansion upgrades, the shift pressure can be increased from 0.8 MPa to 1.5–2.1 MPa (depending on the overall production process); this can result in energy savings of around 30–50 kWh per ton of ammonia produced. 　　15. Energy-saving full low-temperature shift and medium-low-low temperature shift processes 　　With the use of wide-temperature cobalt-molybdenum low-temperature shift catalysts, energy-saving full low-temperature shift or medium-low-low temperature shift processes can be employed, depending on the specific production conditions of the enterprise. This process features a high conversion rate, a simple flow structure, low resistance, and low steam consumption; the steam consumption per ton of ammonia is ≤250 kg and ≤350 kg respectively. 　　16. CO2 removal processes using improved propanol carbon method, NHD method, and pressure swing adsorption (PSA) method. All three of these processes are low-energy-consuming decarbonization technologies currently used by various enterprises; the choice among them should be determined based on the requirements for the purified gas, the conditions of the processes before and after, as well as technical and economic factors, taking into account the specific circumstances of each enterprise. 　　17. Recovery of power by turbine units In the wet solvent decarburization process, at certain production scales, turbine units can be used to recover the energy from the decarburized liquid; this allows for a reduction in electricity consumption for the decarburization pumps of 12–36 kWh per ton of ammonia produced. 　　18. Alcohol alkylation (dimethyl) or alcohol hydrocarbonation gas purification process: This technology represents a clean production method that replaces the traditional copper-based purification process. It allows for savings of 40–50 kWh of electricity per ton of ammonia produced, as well as reductions in the use of raw materials such as electrolytic copper, glacial acetic acid, and ammonia. It offers excellent environmental benefits and economic advantages, making it a key energy-saving improvement measure for the future. 　　19. Adoption of economically reasonable synthesis pressure 　　With regard to the production intensity for ammonia synthesis catalysts, based on considerations such as low space velocity, high specific yield, low resistance, and energy savings, as well as technical and economic analyses, it is recommended to select synthesis towers and catalysts that allow for a production intensity of 18–20 t of ammonia per m3•day. This results in an operating pressure of 22 M–24 MPa (slightly lower, around 2 MPa, in the initial stage). Such settings enable savings of around 50 kWh per ton of ammonia produced, while also increasing ammonia output by 2%–3%. 　　20. By using ammonia catalysts with good activity, wide operating temperature range, and high strength, along with efficient and energy-saving synthesis towers that match them, the net ammonia yield can be increased. This reduces the volume of gas that needs to be recycled, lowers the electrical energy consumption associated with the recycling process, and decreases the energy required for cooling. 　　21. External temperature-raising synthesis process and two-stage waste heat recovery technology: The use of this process technology for the recovery of heat generated during the ammonia synthesis reaction enables the waste heat from the syngas production process to be utilized in multiple stages based on its potential energy level. Steam is produced by waste heat boilers, and soft water is heated using soft water heaters; this approach helps to significantly increase the efficiency of waste heat recovery and reduce the amount of circulating cooling water required. 　　22. Ammonia and hydrogen recovery technologies In the ammonia synthesis process, changes in production load lead to an increase in the amount of gas released from the synthesis system and from the ammonia storage tanks in order to maintain an appropriate operating pressure in this system. These gases contain large amounts of ammonia and hydrogen, which are thus wasted, resulting in increased consumption of materials used in ammonia synthesis and higher costs. Based on the different components and properties of these two gas sources, membrane separation technology can be used to recover hydrogen from the vented gas, while unpowered ammonia recovery technology can be employed to recover ammonia from the gas released from the ammonia tanks. 　　23. Evaporative Condenser in Refrigeration Systems This device utilizes advanced engineering techniques from thermodynamics and heat transfer to optimize the combination of cross-flow cooling towers and traditional evaporative condensers. It features a compact structure, low space requirement, light weight, and easy installation. By using high-efficiency heat transfer elements, it improves heat exchange efficiency and cooling performance, resulting in lower operating power consumption, reduced electricity usage, and less demand for cooling water. It is an effective energy-saving solution that can replace traditional vertical water-cooled condensers. 　　24. Utilization of low-grade waste heat through lithium bromide absorption refrigeration technology: By making use of the low-grade waste heat generated during the production of urea and synthetic ammonia (such as hot water and condensate), hot-water-type lithium bromide absorption chillers can be used to produce low-temperature chilled water. This chilled water is employed for cooling the gas at the inlet of the first stage of nitrogen-hydrogen compressors, as well as the gas at the inlets of the third, sixth, and seventh stages; it is also used in the decarburization absorption process and in the ammonia synthesis cycle. By making full use of this low-grade heat, it is possible to increase the compression capacity of the compressors, reduce the volume of fluid required for the decarburization absorption process, and lower the load on ammonia chillers and freezers. This leads to increased production and reduced electricity consumption, with particularly significant benefits during hot seasons such as summer. 　　25. Variable frequency speed control technology is used for pump motors. For rotating equipment where the load varies, resulting in situations where the pump motor has to work under excessive load, such as furnace strip machines used in gas production, boiler coal feeders, feed water pumps, air blowers, Roots blowers, ammonium methyl pump, liquid ammonia pumps, etc., variable frequency speed control is employed to achieve smooth, stepless speed adjustment. This allows for better speed control during production, thereby achieving significant energy savings. For the speed control of high-voltage medium and large-capacity AC motors, internal-fed carrier speed control technology can be employed; compared with high-voltage frequency conversion, it offers advantages such as higher efficiency, lower cost, and greater power output. 　　26. Power savings in nitrogen-hydrogen compressors The power consumption of nitrogen-hydrogen compressors accounts for about 70% of the total electricity used in ammonia synthesis; therefore, the proper selection and use of compressors have a significant impact on the electricity consumption per ton of ammonia produced. It is necessary to phase out outdated and energy-intensive compressors such as L3.3-17, 4M8, and 4H8. By adopting energy-saving upgrades, large and medium-sized units with a synthetic ammonia production capacity of ≥20,000 tons per year should be selected, thereby significantly reducing the electricity consumption per ton of ammonia produced. Technical measures such as using reliable air valves to extend the fault-free operation time of the unit, ensuring effective cooling of the circulating oil, increasing the inlet pressure, reducing the inlet temperature, and improving the efficiency of inter-stage cooling and separation equipment. Try to avoid operating different compressor models in parallel, in order to prevent unnecessary power losses resulting from incompatible operation and to avoid issues related to the operational failure cycle. 　　27. Power savings in corporate power grid systems This power-saving solution relies on significant advancements in semiconductor transient current control technology, composite real-time filtering technology, and remote monitoring and diagnostic technologies. It enables timely detection and effective control of transient currents and high-order harmonics with a response time of 10–12 seconds. It also eliminates the transient currents caused by sudden changes in energy resulting from the switching on and off of equipment, thereby improving power quality, reducing power losses, and enhancing the efficiency of the electrical equipment in the system. 　　28. Energy savings in steam pipeline systems The steam pipeline system that transports steam from the boiler room to various consumption points should follow the principle of high-pressure transmission and low-pressure use, which can reduce pipeline construction costs and heat loss. The system should appropriately select and configure sufficient steam traps; the performance of these steam traps has a direct impact on steam consumption, making it the area with the greatest potential for energy savings. It is necessary to carry out insulation work on the steam pipeline system in order to reduce heat loss in the pipeline network. 　　29. Recycling of Condensate Water 　　Currently, the condensate water generated by steam heating is largely discharged directly into sewers. It should be transformed as much as possible to be fully recycled; this not only allows for the recovery of its heat and thus reduces fuel consumption in boilers, but also saves on water and water treatment costs, thereby lowering production expenses. 　　30. Pay attention to research on energy conservation and consumption reduction during the hot seasons. Under different seasons and temperature conditions, the output of synthetic ammonia as well as the electricity consumption per ton of ammonia vary. In particular, the electricity consumption per ton of ammonia during the hot seasons in the third quarter is 50–150 kWh higher than that in the cold seasons of the first quarter, and it is 30–100 kWh higher than the annual average. This is more evident in the south than in the north. Finding a way to address the issue during periods of high temperatures is an important task for further improving energy efficiency and reducing costs in ammonia synthesis, and it deserves attention from all relevant parties.

For ammonia synthesis plants using this typical process, energy-saving efforts can generally only focus on gas generation. Coal selection, furnace condition adjustment, and so on. At the micro level, it means strengthening management ； Management of personnel, management of equipment, management of production processes, management of leaks and other issues.

I agree with what was said above. Generally speaking, it’s about generating gas; the consumption associated with gas generation accounts for half of the total consumption in ammonia synthesis. Energy savings and reduction in consumption are evident. The suggestions put forward by the person on the second floor are excellent, and most factories already use them – they should have been widely adopted by now. On a smaller scale, it comes down to management; private enterprises perform better than state-owned enterprises, and that is due to better management.

Research Report on Energy Saving and Consumption Reduction in the Production of Small-scale Nitrogen Fertilizers (Part 1) I. The historical role of small-scale nitrogen fertilizers in China’s fertilizer industry China’s small-scale nitrogen fertilizer industry began to develop in 1958, and the use of ammonium bicarbonate as a fertilizer was an innovation on a global scale. Its raw materials are simple; aside from ammonia, it uses waste products from ammonia synthesis plants (carbon dioxide), and it does not require sulfuric acid or nitric acid like sulfuric acid and anhydrous acid. At the same time, the materials used in manufacturing its equipment do not require stainless steel or non-ferrous metals, as is the case with *ao acid and urea. The processing of urea requires high pressure, whereas the processing of ammonium bicarbonate is carried out under low pressure. The equipment and materials it requires are merely ordinary pig iron and standard carbon steel. Therefore, the equipment structure is relatively simple, and the investment is also low. At the same time, small-scale ammonia synthesis uses coal as the main raw material, showing strong adaptability to different raw materials. Using local materials, producing locally, and applying them on-site avoids long-distance transportation. Research conducted by the Soil and Fertilizer Research Institute of the Shanghai Academy of Agricultural Sciences has shown that ammonium carbonate, when used in rice cultivation, exhibits a higher fertilizing efficiency than ammonium sulfate and urea with equivalent nitrogen content. It is used for dry farming and applied in conventional ways; its fertilizer efficiency is slightly lower than that of ammonium sulfate and urea. However, by choosing appropriate application methods and making use of its strengths while mitigating its weaknesses, its fertilizer efficiency can reach a level comparable to that of stable nitrogen fertilizers. Therefore, the long-term use of ammonium carbonate as a fertilizer in China is inevitable from social, economic, and technical perspectives. II. Current status of the small nitrogen fertilizer industry At present, there are over 1,300 small ammonia synthesis plants in China, of which more than 1,200 use coal as raw material, over 80 use natural gas, and 5 use oil. In 1981, the total national production of small-scale synthetic ammonia reached 7.79 million tons, accounting for 52.6% of the country’s total synthetic ammonia production. The small nitrogen fertilizer industry holds an important position in China’s fertilizer industry, making significant contributions to supporting agriculture. Small nitrogen fertilizer plants have long been perceived as having low production, high consumption, high costs, and significant losses. Over the past 24 years, during its formation and development, the small nitrogen fertilizer industry has been affected by erroneous \"leftist\" ideas. Especially during the ten-year catastrophe, many places, regardless of objective and subjective conditions, rushed to build factories blindly, resulting in many of these factories remaining in a backward and disadvantaged situation characterized by low productivity, high consumption, high costs, and heavy losses. However, in recent years, the small nitrogen fertilizer sector has resolutely implemented the eight-character policy centered on adjustment, focusing on improving enterprise management; it has carried out numerous minor reforms to reduce consumption and save energy, placed emphasis on operational management based primarily on economic accounting, and achieved good results in turning losses into profits. Table 1: Profitability trends of small-scale nitrogen fertilizer production nationwide from 1976 to 1981
Year: 1976, 1977, 1978, 1979, 1980, 1981, 1982
Profit/loss (in 100 million yuan): –9.7, –8.9, –6.1, –4.1, –0.85, –0.69, –0.31
Loss per ton of ammonia (in yuan): –265, –185, –92, –56, –10.4, –5

The key to turning losses into profits was a significant reduction in the consumption of raw materials such as coal and electricity. The comparison of coal and electricity consumption for small-scale nitrogen fertilizer production nationwide in 1981 versus 1976 is shown in Table 2.

Table 2: Comparison of coal and electricity consumption for small-scale nitrogen fertilizer production in 1976 and 1981
Year | Coal consumption (10,000 tons) | Electricity consumption (10,000 kWh) | Total energy consumption (10,000 kcal)
1976 | 418 | 122 | 393 | 634
1981 | 226 | 91 | 458 | 2040
Percentage decrease: 43.3%, 44.3%

Among these regions, Shanghai, Jiangsu, Beijing, and Shandong had coal consumption levels below the national average; their coal consumption for small-scale nitrogen fertilizer production was under 2,000 kilograms per ton, while electricity consumption was 1,400 kWh per ton. Shanghai’s total energy consumption per ton of ammonia was 16.07 million kcal, and Zhejiang Province’s was 16.22 million kcal – both figures being lower than the average energy consumption of medium-sized nitrogen fertilizer plants nationwide, which was 17.07 million kcal per ton. 130 small-scale nitrogen fertilizer plants that used coal as a raw material achieved the goal of reducing their total energy consumption per ton of ammonia to below 17.5 million kcal by 1985 ahead of schedule. However, the development levels vary greatly among different regions and enterprises, which is a prominent issue in the small nitrogen fertilizer industry at present. There are significant differences between provinces as well as between enterprises in terms of energy consumption and product costs. In terms of energy consumption, when analyzing on a provincial level, in 1981, six provinces and regions including Guizhou, Qinghai, Xinjiang, and Ningxia still had a high coal consumption per ton of ammonia produced, with it remaining above 2,900 kilograms. The electricity consumption per ton of ammonia remains above 1,700 kWh. Guizhou has the highest consumption levels: the coal consumption per ton of ammonia there is 3,271 kilograms, while the electricity consumption is 1,878 kWh – figures that are 100% and 40% higher respectively than those in Shanghai, which has the lowest consumption levels. There are also significant differences among enterprises in a single province. For example, in Zhejiang Province, one of the provinces in China with the best economic benefits from the use of small-scale chemical fertilizers, the coal consumption was 1392 kilograms in the lowest cases and 2138 kilograms in the highest cases, representing a difference of 75%. When examining enterprises on a per-unit basis, in 1981 there were still 238 small nitrogen fertilizer manufacturers in the country whose coal consumption per ton of ammonia produced exceeded 2,800 kilograms, and whose electricity consumption exceeded 1,600 kWh – figures that were 23.5% and 23.4% higher respectively than the national average for such small fertilizer manufacturers. Using coal coke as raw material, in 1981 the fertilizer plant in Taicang, Jiangsu, had the lowest total energy consumption per ton of ammonia among all small fertilizer plants in the country, at 12.86 million kcal; the average national figure was 20.4 million kcal. According to theoretical calculations conducted by the Shanghai Chemical Engineering Institute, the total energy consumption per ton of ammonia can be reduced to 11,460,400 kcal. If the output of small-scale fertilizers in 1981 is calculated based on the consumption levels of 1976 and the actual consumption amount is deducted, it can be determined that the energy saved in 1981 was approximately over 13.7 million tons of standard coal. Based on the fact that an industrial output value of 100 million yuan in 1981 required an average of 60,800 tons of standard coal, the energy saved through the use of small-scale fertilizers could have contributed to an increase in industrial output value of 17 billion yuan. If the energy consumption level for small-scale fertilizer production across the country were to approach or reach that of the Taicang Fertilizer Factory, the savings in energy would be substantial, which is particularly significant given the current tight energy supply situation. This research report summarizes the successful experiences of small fertilizer plants in saving energy and reducing consumption, and explores the directions that can be followed for further improvements. The main methods used were reviewing relevant materials and conducting on-site inspections (with Gaocheng Fertilizer Plant as a case study). The findings of this research along with our opinions are presented as follows: III. Successful experiences of small nitrogen fertilizer plants in saving energy and reducing consumption 1) Management issues in small nitrogen fertilizer plants: Scientific management and technological upgrades are the two key factors driving the development of small nitrogen fertilizer production; some say that effective management accounts for 70% of success in this field, while technology accounts for 30%. Under the same design and equipment conditions, as well as similar factory construction conditions, there are significant differences in economic efficiency due to variations in corporate management levels—that is, differences in subjective factors. A considerable number of small nitrogen fertilizer plants have weak management systems; a few are even in a chaotic state. Even those that are more advanced still face the challenge of improving their management practices to make them more scientific. Therefore, efforts to manage and reorganize small nitrogen fertilizer enterprises must not be relaxed in the slightest; improving enterprise management is both urgent and a long-term task. 1. To strengthen raw material management, it is necessary to earnestly implement the 48-point coal plant management approach, which includes ensuring that both types of coal enter the plant, weighing and measuring them, sorting them by quality, labeling them, removing impurities such as gangue, and sieving out coal dust. To achieve dry coal (3% moisture), clean powder (3% coal dust), and low stone content (5%). 2. Strengthen equipment management by continuing to implement the dual-responsibility system, carrying out activities aimed at upgrading equipment, and ensuring that the equipment’s condition rate remains above 85% while reducing the leakage rate to below 3‰. In particular, it is crucial to maintain high levels of reliability and low leakage rates for the compressors, which consume the most electricity; this is key to increasing productivity per machine hour and reducing power consumption. At the same time, based on the actual conditions of each factory, operations are carried out in a rational manner to ensure economic efficiency. By promoting the experience of \"operating three machines from one furnace,\" each enterprise determines the main and auxiliary operators, as well as the number of furnaces and machines to be used, the production volume, and the material consumption, based on its own circumstances. 3. Pay close attention to process management and strictly enforce the process parameters. The entire production process of small-scale chemical fertilizers is part of modern manufacturing; most of the machinery used in this process is mechanical or semi-mechanical. Physical and chemical changes occur throughout the production process, and fertilizer production is characterized by high temperatures, high pressures, as well as the risks of fire, explosion, and poisoning. There are twelve positions in total, ranging from water supply to fertilizer packaging; the boiler generates steam, and the compressor compresses the raw gas from low pressure to high pressure, which is a physical transformation process. Processes such as water treatment, gas production, shift reaction, copper washing, synthesis, and carbonization involve chemical reactions. Operators need to understand it, and leaders need to understand it as well. The entire process of fertilizer production is characterized by strictness and continuity; if this strictness is compromised, the continuity of the process will be disrupted. If a malfunction occurs at any stage of production, it will affect the overall production capacity of the plant. Process management must first ensure strict compliance with the 20 process indicators set by the authorities, preventing a situation where efforts are focused on increasing output at the expense of strict adherence to these indicators. It is also necessary to properly balance the need for strict process management and compliance with the requirements for high production volumes, stable output, low consumption, and safe production. The 20 process indicators issued by the ministry are experiences derived from long-term practice and must be strictly followed. ⑴The carbonization degree of coal balls is ≥80%. ⑵Semi-water gas: CO + H2 ≥ 68%. ⑶Semi-water gas: O2 ≤ 0.5%. High oxygen levels can cause a sharp rise in catalyst temperature, resulting in the waste of large amounts of steam to regulate this temperature; moreover, it damages the catalyst’s activity. For every 0.1% increase in oxygen content, the temperature of the conversion catalyst rises by 7°C, and a 1% increase in oxygen content leads to an additional 0.5 tons of steam being consumed per ton of ammonia produced. ⑷After desulfurization, H2S is <0.1 grams/m3. ⑸Total solids in the saturated tower < 500 Pm. ⑹The catalyst hotspot temperature variation is <±10°C. ⑺The CO content in the transformed gas is 3–3.5%. ⑻The raw gas CO2 content is ≤0.2%. ⑼Raw gas NH3 < 0.2 grams/m3. ⑽The raw gas H2S level is <0.01 grams/m3. ⑾The CO2 content in the gas entering the carbonization tower is ≥23%. ⑿Total copper content in the copper melt: 2.0–2.5 m/e. ⒀Refined gas CO + CO2 ≤ 30 ppm. ⒁Synthetic cycle gas H2/N2S 2.2～2.3. ⒂The synthetic cycle gas has a CH4 content of >12%. ⒃Ammonia at the inlet of the synthesis tower ≤ 2.0%. ⒄The hotspot temperature of the synthetic catalyst is <±5°C. ⒅Boiler feed water hardness < 0.3 degrees. ⒆Boiler feedwater alkalinity < 14 milliequivalents/liter. ⒇The salt content in the boiler feed water is <3000 mg/L. 4. Use the post responsibility system as a lever to carry out comprehensive economic accounting, ensuring that consumption is within specified limits. These include labor quotas, consumption quotas for raw materials, fuel, power, and tools, capital utilization, material reserves, as well as expense expenditure quotas. Costs are accounted for, economic activity analysis is conducted, and economic efficiency is continuously improved. Enterprises, workshops, and teams all operate on a cost-effective basis. Workshop teams are internal components of an enterprise, not independent business entities; therefore, unlike the enterprise’s financial accounting, their focus is primarily on comparing actual results with plans and assessing the level of economic efficiency. Therefore, to implement economic accounting at the workshop and team levels, it is necessary to assign targets to these units. The targets assigned to workshops and teams generally include: (1) product variety, quantity, and quality. ⑵Consumption quota or cost. ⑶Labor productivity and costs. Units can be added according to specific circumstances and needs. To carry out comprehensive economic accounting effectively, it is first necessary to improve enterprise management and establish appropriate staffing levels ； Second, it is necessary to strengthen the measurement of instruments and acceptance processes, keep accurate original records, and ensure their correctness and reliability. In accordance with the principle of combining responsibilities, powers, and interests, the economic responsibilities that the enterprise must assume are first assigned to the party secretary, factory director, departments, and workshops, and then further allocated at each level to the work teams as well as to every employee. Once responsibilities are clearly defined, rewards are calculated on a percentage basis; strict assessments are carried out, with more work leading to greater rewards, thereby effectively linking the post responsibility system to the company’s economic performance and individual interests. ““The three-man management system” is a corporate management approach that was introduced by Tongxiang Fertilizer Factory in 1978, and practice has shown that it still retains its strong vitality to this day. To this day, some enterprises suffer from chaotic management, poorly maintained equipment, lax control over technical parameters, inefficiencies in coal usage and electricity consumption, as well as a system of equal distribution for all. It’s the more advanced factories that also have many problems. Therefore, strengthening enterprise management, making serious efforts in operational management, striving to reduce various fixed and variable costs, paying attention to economic accounting and economic efficiency, minimizing waste, and closely integrating technical work with economic work are all prerequisites for achieving energy savings and reduced consumption in enterprises. The key to the success of management lies in having a cadre team with modern capabilities, while also rapidly improving the cultural and technical skills of the workforce. Currently, all enterprises must carry out comprehensive training for all employees. All those who are employed, whether workers, cadres, leadership officials, or technical personnel, receive planned training. Technicians graduated from specialized schools are needed to handle processes, testing, equipment, and power supply. Only by fundamentally improving the cultural and technical level of the workforce can scientific management of enterprises be achieved. This is a very important fundamental task, and it is also an essential step for the further progress and development of the small nitrogen fertilizer industry in the future. (ii) Focus on energy conservation and consumption reduction, and carry out efforts to tap potential, innovate, and upgrade. Over the 24 years since the inception of small nitrogen fertilizer production, thanks to the efforts of the numerous cadres, workers, and technical personnel involved in this field, the production technologies have become increasingly sophisticated. In 1981, the total energy consumption per ton of ammonia produced in Shanghai and Zhejiang was lower than the average energy consumption of medium-sized nitrogen fertilizer plants during the same period, and extensive experience has been accumulated over time. Table 3: Comparison of technical and economic indicators for medium and small ammonia plants from January to September 1980. Plants using coal and coke as raw materials: raw coal – Kg/TNN3; fuel coal or steam – Kg/TNN3; electricity – kWh/TNN3; total energy consumption – 10 Kcae/TNN3; cost – yuan/TNN3. Medium-sized ammonia plants: 3113, 29. Plants using steam: 3090, 1440, 1704. Plants using coal: 309; those using coke: 312. Zhejiang Small Nitrogen Fertilizer Plant: 4811, 56. Plants using coal: 602, 1289, 1653, 3315.41 Many of these successful practices have been adopted widely in small nitrogen fertilizer production systems, contributing to a reduction in the total energy consumption per ton of ammonia produced. These successful experiences are as follows: 1. Regarding the scale of construction, small nitrogen fertilizer plants are an industry with a strong local character; the fertilizers they produce are mainly used locally in the same county. Moreover, since the types of fertilizers consist mainly of carbon ammonium and ammonia water, which have low concentrations of active ingredients, it is not feasible to transport them over long distances. Therefore, the scale of construction for small nitrogen fertilizer plants is determined based on the ability to meet the average demand for nitrogen fertilizer application in the respective county or region. Generally, 30 to 40 kilograms of carbon ammonium should be applied per mu per growing season for grain crops; for crops grown on two harvests per year, this amounts to 20 kilograms of liquid ammonia per mu. For a county-owned factory operating on a land area of 500,000 mu, the production scale should be around 10,000 tons. Qin Zhongda, Minister of the Chemical Industry, wrote an article in the China Finance and Trade News in July 1982 stating that after years of repeated design revisions, an economically viable scale for small nitrogen fertilizer production has been determined, and equipment such as gas generators, compressors, and synthesis towers with high efficiency has also been largely finalized. In areas where coal power supply and transportation conditions are favorable, and where there is a local demand for fertilizers, these enterprises can, through restructuring, carry out planned and selective upgrades, gradually achieving standardization and serialization of their equipment, thereby raising their annual production capacity to around 10,000 tons. For those individual factories that do meet the requirements, their production capacity can be increased gradually, but it should not exceed 20,000 to 30,000 tons at most. The issue of a factory’s scale is, for such a factory, a matter of strategic planning. If one does not plan for the future, one will surely face troubles soon. When expanding, optimizing, and renovating, the final scale must be taken into account; avoiding or minimizing the need to keep patching things up after making changes can help achieve lower investment costs and faster results. 2. Regarding the selection of equipment, based on the scale of construction and future development prospects, we believe that two synthesis pressures, along with two types of furnaces, three types of machines, and two types of towers, are a more practical choice. That is, 320, 200 atmospheres, gasifiers with φ2260 and 1600 dimensions, M-type, H-type or L-type compressors, synthesis towers with φ500 and φ600 dimensions; in particular, the type of gasifier depends on the scale and the type of raw coal used. For a scale of 10,000 tons, one φ2200 furnace is not sufficient; using two is unnecessary as it is not cost-effective. Again, for capacities over 20,000 tons, using L-type compressors would result in a small cluster of units, which is also not cost-effective. In short, when small factories carry out technological upgrades, the selection of equipment should be based on the actual conditions of each factory; a one-size-fits-all approach cannot be used. At the same time, it is necessary to keep replacing and phasing out equipment that has insufficient capacity, high energy consumption, high maintenance costs, and outdated operating methods. Research Report on Energy Saving and Consumption Reduction in Small-scale Nitrogen Fertilizer Production (Part 2) 3 While carrying out technical upgrades, minor improvements and innovations should not be overlooked. Many small nitrogen fertilizer enterprises have adopted the ten minor improvements proposed by the Ministry of Chemical Industry; these improvements are characterized by low investment, rapid implementation, and good results. These ten minor improvements have played an important role in saving energy and reducing consumption. ⑴Improve the quality of semi-water gas. The task of gas production is to supply an adequate amount of gas, ensure its quality, and minimize raw material consumption. There are two main components that control the gas: one is the content of CO+H2. The second is oxygen content. The former ensures the proper progress of the ammonia synthesis reaction, while the latter protects the shift catalyst, saves steam, and ensures safe production. A high level of CO+H2 indicates proper temperature control in the furnace, efficient reactions within it, a high rate of steam decomposition, and a large amount of gas produced per furnace – which not only saves steam but also results in high-quality semi-water gas. The level of CO+H2 should be maintained at ≥68%. From a process perspective, the lower the oxygen content in semi-water gas, the better; this is highly beneficial for saving steam and increasing the pumping capacity of the high-pressure compressor. An oxygen content of ≤0.5% is reasonable. High oxygen levels can cause the catalyst temperature to rise sharply; in such cases, steam is used to regulate the temperature, which results in waste of steam and a reduction in the catalyst’s activity. For semi-water coal, an increase of 0.1% in oxygen content can raise the temperature of the conversion catalyst by 7°C, while an increase of 1% in oxygen content leads to a consumption of 0.5 tons more steam per ton of ammonia produced ； At the same time, the increased oxygen content in semi-water coal gas occupies the available volume, thereby reducing the pumping capacity of the compressor (in the context of the pressure conversion process), which affects production. ⑵When superheated steam is used to generate gas, not all of the steam entering the furnace can be decomposed and utilized; the undecomposed steam is condensed and wasted in the gas washing box and gas washing tower. The heat loss resulting from these steam losses determines the value of the steam decomposition rate. Using superheated steam for gas production can increase the steam decomposition rate, reduce heat loss caused by the superheated steam, and enhance the gasification efficiency of the gas generator. ⑶Reasonably control the CO2 content in the converted gas; generally, the CO2 level in the converted gas should not be too high to prevent minor accidents caused by copper washing. Theoretically, at a certain temperature, increasing the amount of water vapor used can raise the conversion rate; however, the conversion rate of CO does not increase in direct proportion to the amount of water vapor added – it increases rapidly at first and then more slowly. As a result, the CO2 content in the converted gas cannot be kept too low, otherwise steam consumption will increase. When the CO2 content in the shift gas is 30%, and the CO content in the shift gas decreases from 3.5% to 2%, the steam-to-gas ratio needs to increase from 0.97 to 1.37, resulting in a more than 37% increase in steam consumption. In actual production, it is reasonable to keep the CO content between 3% and 3.5%, as this helps to save steam and reduce coal consumption. ⑷Improving the heat recovery efficiency of saturated hot water towers means that, under certain outlet temperature conditions of the shift converter, when a specific conversion rate is required, the amount of steam fed into the shift converter remains constant. Therefore, the more heat recovered from the saturated slurry, the less external steam is required. The higher the temperature of the gas exiting the saturated tower, the higher the saturation level, and thus more steam can be recovered. The hot water entering the saturated tower comes from the hot water tower; therefore, increasing the temperature of the hot water entering the saturated tower corresponds to increasing the outlet water temperature of the hot water tower. In practical operation, the outlet water temperature of the hot water tower is determined by the hot water circulation volume. Generally speaking, increasing the hot water circulation rate improves gas-liquid contact, which facilitates mass and heat transfer; as a result, it is possible to increase the saturation of semi-water gas at the outlet of the saturated tower, as well as the temperature difference between the gas exiting the tower and the hot water entering it. However, if the amount of hot water circulating is too high, in addition to severe water carryover in the gas leaving the tower and an increase in internal resistance within the tower, the temperature of the semi-water gas exiting the saturated tower actually decreases. This is because the heat of the circulating hot water comes from the reformate gas, and this heat remains essentially constant for a given volume of gas. As the amount of circulating water increases, the temperature rise of the circulating water as it passes through the hot water tower and the water heater inevitably decreases. As a result, the temperature of the hot water in the saturated tower drops, which in turn lowers the temperature of the semi-water gas leaving the saturated tower; thus, the ultimate goal of increasing the water vapor content in the semi-water gas exiting the saturated tower is not achieved. Conversely, when the hot water circulation volume decreases, although the temperature of the hot water at the outlet of the hot water tower rises, the temperature of the semi-water gas at the outlet of the saturated tower also inevitably drops, as the amount of hot water entering the saturated tower decreases while the volume of semi-water gas entering it remains unchanged. An excessive or insufficient amount of hot water circulation is detrimental to the recovery of water vapor. In factory production, it is necessary to determine, based on the existing equipment conditions, the optimal circulation rate that allows for the highest water temperature at the inlet of the saturation tower and the greatest saturation level. ⑸The shift converter uses an electric furnace for heating; an electric heater is installed between the outlet of the heat exchanger and the inlet of the shift converter, with this electric heater being used to carry out the heating and reduction process. Initially, air can be used for heating, which saves coal gas and steam, and also provides time for maintenance of the gas generation boiler. This method is used when starting up the equipment after a normal shutdown; by supplying power, the furnace temperature can be increased, allowing normal production to resume quickly. This method is simple to operate and easy to use. With each heating and reduction cycle, costs can be saved by about 3,000 to 4,000 yuan compared to a combustion furnace; moreover, the time required for heating and reduction can be appropriately reduced, allowing for earlier commencement of production. ⑹In the piston-type high-pressure compressors used in fertilizer plants, which have a large number of stages, balance chambers are installed between each stage to balance the piston forces. In the original design, the return air interface of the balance chamber is usually located in the low-pressure section. The greater the pressure difference Δp between the working cylinder and the balance chamber, the larger the amount of air that leaks into the balance chamber through the piston rings. Therefore, by reducing the value of Δp, that is, by increasing the return air pressure of the balance chamber, it is possible to reduce the amount of air leakage and thus increase the pumping capacity of the high-pressure compressor. If connected, the return air from stages 6–7 of the L3.3–17/320 compressor should be connected to 5, the return air from stages 4–5 to 3, and the return air from stages 2–3 to 1. Similarly, the oil separation and gas release from compressor oil can also be recovered in stages. This alternative method should be used with caution; the forces acting on the piston need to be checked to prevent vibrations caused by uneven stress. ⑺The methane in the synthetic cycle gas meets the specified standards. The inert gases in the synthetic mixture refer mainly to CH4 and Ar; they occupy a certain volume, reducing the partial pressures of hydrogen and nitrogen and thereby decreasing the ammonia production rate. Therefore, the higher the inert gas level, the more unfavorable it is for ammonia formation. Inert gases do not participate in the reaction; as they pass through the synthesis tower, they carry away some heat, affecting the temperature of the catalyst layer. The presence of large amounts of inert gas also unnecessarily increases the power consumption of the compressors and circulation pumps. CH4 also undergoes decomposition reactions at high temperatures, causing damage to the catalyst. However, when inert gases are released, some hydrogen and nitrogen are also lost. Therefore, it is necessary to control the appropriate circulating CH4 level, which can reduce the consumption rate of make-up gas. Therefore, an appropriate amount of inert gas must be selected. Therefore, it is necessary to strictly comply with the ministry-set targets: for plants of 3,000 tons capacity, CH4 levels must be >12%, and for plants of 5,000 tons capacity, CH4 levels must be >15%. ⑻“Three” hydrogen recovery ①: Recovery of refined recycled hydrogen; CO content in the feed gas is 4%, with a consumption rate of 3400 standard m3 per ton of ammonia-producing feed gas. After the copper melt is regenerated, it is introduced into the regenerated gas, which is then recycled. Approximately 120 standard cubic meters of CO are recovered from this regenerated gas per ton of ammonia produced; assuming that 90% of this CO is converted into H2, 54.7 kilograms of synthetic ammonia can be generated, accounting for about 5% of the total output. The regenerated gas from the reflux tower mixes with the soft water (or dilute ammonia water) pumped in at the ammonia absorber; the ammonia and CO2 present in the regenerated gas are absorbed. The fluid moves to the recovery tower, while the liquid goes to the bottom of the tower. Gases such as CO, H2, and N2 are sent from the top of the recovery tower through pipes to the inlet of the Roots blower in the desulfurization unit. The dilute ammonia water from the recovery tower is pumped into a high-position ammonia absorber for circulation. When the concentration reaches 70 titers, it is pumped to the circulation tank in the ammonium carbamate section and soft water is supplied to the recovery tower. ② Synthesis off-gas recovery involves the absorption of ammonia from the synthesis off-gases by a pure ammonia tower; the synthesis off-gases enter at the bottom of this tower. The ammonia is absorbed by water to form dilute ammonia solution, which is used for desulfurization. The hydrogen, nitrogen, and methane gases after purification pass through an ammonia full-water seal before entering the boiler furnace for combustion. Per ton of ammonia, 259.521 standard cubic meters of exhaust gas can be recovered, and 20.72 kilograms of ammonia can be recovered as well, accounting for 2% of the total output. The calorific value of the exhaust gas is 3066 kcal per standard cubic meter, which corresponds to energy savings of over 700,000 kcal. ③ The ammonia from the ammonia tank’s vent gas is sent to the bubble absorption tower; after ammonia absorption in this tower, it proceeds to the pure ammonia tower, and finally is sent to the boiler for combustion via a pressure control valve. 11.31 standard cubic meters of combustible gas can be recovered from 1 ton of ammonia, yielding approximately 20 kilograms of ammonia. ⑼Improving boiler efficiency and promoting fluidized bed boilers according to local conditions involves taking measures to reduce losses due to mechanical incomplete combustion, heat loss from flue gases, chemical incomplete combustion, heat loss through radiation, and heat loss associated with ash and slag. Boiler systems that operate by boiling combustion can use substandard coal, have a high throughput, but lower thermal efficiency. Therefore, when choosing a boiling furnace, factors such as the source of the raw material (gangue) and the convenience of transportation must be taken into consideration. ⑽Waste heat recovery refers to the recovery of the process reaction waste heat from the conversion, synthesis, and gas generation units. The heat recoverable by the conversion system amounts to 555,000 kcal per ton of ammonia. The heat recoverable by the synthesis system per ton of ammonia amounts to 552,000 kcal. The jacket of the gas generator and the waste heat boiler can recover up to 270,000 kcal of sensible heat per ton of ammonia produced. The ten effective energy-saving technical measures promoted by the Ministry of Chemical Industry require low investment, can be implemented quickly, and yield good results. IV. Future efforts to save energy and reduce consumption in small nitrogen fertilizer plants through exploration, innovation, and reform: Key tasks, directions, and practical approaches. Experience has shown that as long as small nitrogen fertilizer plants pay close attention to the \"three managements and one accounting\" aspects of operation and management, as well as to technical upgrades focused on energy savings, they can improve their economic efficiency. Their total energy consumption can then reach the advanced levels seen in regions such as Shanghai and Zhejiang, allowing them to compete on par with medium-sized nitrogen fertilizer plants. This research report also aims to highlight those projects in the field of energy conservation and consumption reduction that receive little attention but have a significant impact. It discusses technical improvement projects that have already been successful in some areas yet have not yet been implemented on a wider scale, as well as some ideas for future efforts in this regard, in order to draw the attention of leaders and technicians in the small nitrogen fertilizer industry. 1. Implement strict water quality treatment and enhance water management. Currently, small nitrogen fertilizer plants generally do not pay enough attention to water quality treatment and water management. First, the requirements for water treatment are not strict; the water quality does not meet the specified standards, which leads to severe scaling of the equipment, affects heat exchange, increases energy consumption, and may even cause boiler tube failures. Second is the improper water treatment method. If only hardness is removed without removing alkalinity, and there is no deoxygenation device, this results in high boiler blowdown volumes as well as oxygen corrosion of pipes and heat exchange equipment. If the groundwater from Gaocheng Fertilizer Factory is treated only to remove hardness but not alkalinity, the boiler’s waste discharge volume can reach 50%. Soft water without deoxygenation causes one water heater B to get damaged every three months; each such heater is worth 35,000 yuan. In a little over a year, four water heaters B will have suffered corrosion, costing a total of 150,000 yuan. Third, the experience of tiered water supply is worth promoting. For example, Gaocheng Fertilizer Factory uses hydrogen-sodium bed exchange, taking into account the different water quality requirements for boiler operation and chemical process water (mainly for carbonization); high-quality soft water is supplied to the boilers, which reduces the boiler’s waste discharge from 50% to 10%. A separate sulfonation media bed is provided for carbonization. These two types of water have different qualities, and thus different costs; the cost per ton for soft water is 0.7 yuan higher. It can save over 70,000 yuan in operating costs per year. Fourth, water use is not metered, resulting in severe waste. Water resources are scarce in the north, so it is important to promote the reuse of water. Based on the characteristics of the small nitrogen fertilizer feeding system, two independent feeding systems can be used. One is the feedwater system of the gas generation section. The wash water discharged from the gas generation section contains substances such as H2S, phenols, cyanides, and dust; it cannot be discharged directly into water bodies, as this would pollute the environment and disrupt the ecological balance. The use of closed-loop circulating water systems and biological treatment towers for wastewater can reduce water consumption, ensuring that toxic substances meet the emission standards. The second is the combined cycle water system for processes such as carbonization, compression, synthesis, freezing, and refining. These sections are mainly used for tube cooling and washing water; they are characterized by being free from direct contamination and having a low temperature rise. A water pressure of 2.0–2.5 Kg/cm2 is sufficient, and it is advantageous to use a circulating water system. Except for the cylinder jackets, domestic use, and soft water requirements, the water available for circulation (including gas generation and desulfurization) accounts for 94% of the total water usage in the plant. By using recycled water, fresh water consumption can be reduced by over 90%. At the same time, the cost of recycled water is low; generally, the cost of direct water supply is 0.05–0.035 yuan per ton, while for a recycled water supply system, the cost is 0.03–0.035 yuan per ton. It protects the environment, prevents pollution, and improves heat transfer and production efficiency. 2. Utilizing waste heat for power generation in a manner suited to local conditions: On September 24th last year, the Ministry of Chemical Industry held a design seminar on differential pressure waste heat power generation in Wuxi. Differential pressure waste heat recovery power generation is an important measure to reduce energy consumption. The standard coal consumption per kilowatt-hour is 200–300 grams, which is 1/2 to 1/3 lower than that of the grid it is connected to; the power supply cost is 1/2 to 1/3 of that incurred by external power supplies. The energy consumption per ton of ammonia is reduced by 300,000 kcal, resulting in a cost reduction of 3–8 yuan per ton of ammonia. However, the following points should be noted when setting up new power generation facilities: (1) The \"recycling of three gases\" and \"utilization of three types of heat\" systems are not properly implemented; if the steam consumption per ton of ammonia is greater than 3 tons, it is not suitable to establish a power generation facility. ⑵Old boilers work well; there’s no need to install new boilers for power generation. Boilers with a pressure of less than 25 Kg/cm2 have low efficiency and are not suitable for power generation. ⑶It produces 15,000 tons of synthetic ammonia per year, boasts high levels of management and technology, and can generate electricity based on local conditions. For capacities below 3,000 tons, a 750KW backpressure unit is appropriate. ⑷The boiler’s steam parameters are low; there are more than two gas generators, and steam motors can be used, but low-frequency protection is required along with the installation of a steam bypass. Steam motors require low investment, yield quick results, and are simple to operate. 3. The electrical power consumption of the high-pressure motor in the electrostatic tar remover accounts for about 70–80% of the total electrical power consumption in ammonia synthesis. Improving the air delivery capacity of the high-pressure motor, ensuring its stable operation over a long period, reducing the frequency of start-up and shutdown operations, and minimizing internal leaks are all important ways to increase the output of the high-pressure motor and reduce electrical consumption. The tar and impurities in the semi-water gas after desulfurization are not completely removed, resulting in severe leakage at valves and piston rings. The internal circulation of gas is an important factor affecting the long-term stable operation of the compressor. The electrostatic tar remover has been successfully tested in areas around Shanghai, such as Qingpu, Jiaxing, and Wusong. The air production capacity of the high-pressure machines has increased from 8 tons per day per unit to 10 tons per day; moreover, the valves and piston rings do not need to be replaced for three months. This technology is worth promoting. 4. One of the characteristics of intermittent gas production using coal (coke) as raw material for latent heat recovery of low-pressure blast air is that a dedicated blowing stage must be established to burn part of the raw coal in order to provide heat for gas production. The blowing gas is the combustion product of the blowing stage. In addition to sensible heat, the blowing air also contains a certain amount of latent heat. This is the CO2 that passes through the carbon layer. This is caused by the reduction of hot carbon to CO, as well as the incorporation of the products from the dry distillation of the raw materials. The common practice in current production is that the latent heat of the blowing air is not recovered. In December 1977, the Fertilizer Industry Research Institute of the Ministry of Chemical Industry successfully resolved the issue of burning with directly added secondary air using low-temperature blast air. In March 1979, the Wendeng Fertilizer Plant in Shandong succeeded in recovering low-temperature blast gas by using low-temperature blast gas and continuous combustion synthesis of di-gas. Since then, the chemical fertilizer plants in Jimo and Jiaonan in Shandong, as well as the chemical fertilizer plant in Taicang in Jiangsu, have also achieved success by using the same method. The low-temperature purge gas contains 5.6% combustibles, with a low calorific value of 183 kcal per standard cubic meter. 1957 standard cubic meters of purge gas are generated per ton of ammonia; if the recovery rate is 86.5%, the actual amount of heat that can be recovered per ton of ammonia is 30.9783 kcal. The sensible heat of the low-temperature blowing gas is 102 kcal per standard m3, and the sensible heat that can be recovered per ton of ammonia is 199,614 kcal. Assuming a recovery rate of 51%, the actual amount of sensible heat that can be recovered per ton of ammonia is 309,783 kcal. If synthetic gas is introduced into the combustion boiler to burn together with low-temperature purge gas, at a rate of 200 standard cubic meters per ton of ammonia recovered, with hydrogen accounting for 57% and methane 21% of the components, the recovery rate is 87.2%, and the heat that can be recovered per ton of ammonia is 56.3614 kcal. A total of 980,200 kcal of heat can be recovered from three tons of ammonia; this is equivalent to saving 140 kilograms of standard bituminous coal per ton of ammonia, worth approximately 84,000 yuan. For a plant that produces 15,000 tons of ammonia per year, the annual value of heat recovered is 126,000 yuan. Low-temperature blast air recovery has accumulated extensive experience in testing and production since 1977; the technology is now largely mature, and its economic benefits are significant, making it worth adopting by various factories. 5. The Shanghai Chemical Engineering Design Institute has recently achieved significant results in applying waste heat utilization – steam comprehensive balance measures in the energy-saving upgrades of several small fertilizer plants. One guiding principle is to use waste heat at lower energy levels to heat water, while using waste heat at higher energy levels to generate steam. ⑴For water treatment to produce soft water, it is first heated to 105°C in a second water heater; thereafter, it is divided into two streams – one going to the waste heat boiler for gas production, and the other being used in the boiler room. ⑵The outlet of the heater above the refined copper melt is at 80°C; the circulating hot water is sent to the synthetic water heater to be heated to 165°C, and then passes through the steam drum to heat the copper melt via the heater above it. After that, the circulating hot water cools down to 80°C and is sent back to the synthetic water heater to be heated to 165°C for reuse. In addition to heating the copper melt, the circulating hot water has a surplus, which can be used to generate a small amount of low-pressure steam for gas production. ⑶Recycle the gas generation purge gas and the steam generated as a by-product of synthesis combustion; per ton of ammonia produced, 10–13 Kg/cm2 of pressure is generated, along with 1.3 tons of steam. ⑷Saturated steam at 10–13 Kg/cm2 is supplied from the gas generation waste heat boiler and the boiler room; after combining, it enters the steam turbine to generate electricity using the steam pressure difference. The low-pressure steam at 2–3 Kg/cm2, resulting from backpressure, is superheated in the waste heat boiler before being used for gas generation. Approximately 15 kWh of electricity can be generated per ton of steam. ⑸The steam required by the transformation section and other sections is supplied by the boiler room. Through the above measures, the plant recovers 1.7 million kcal of heat per ton of ammonia produced. For a plant with an annual production capacity of 20,000 tons of synthetic ammonia, if the boiler needs to be replaced, a 6.5-ton/h boiler operating at 25 Kg/cm2 and 400°C can be used; the superheated steam resulting from backpressure can be supplied to the gas generation furnace for gas production, while the steam required for the shift reaction can be provided by a waste heat boiler powered by the heat generated by the purge air and exhaust air. ⑹The Shanghai Chemical Engineering Design Institute proposes for plants with a capacity of less than 20,000 tons to eliminate boilers, make the most reasonable use possible of waste heat, so that the amount of steam required within the production system can be nearly self-sufficient. ①In addition to burning purge gas and synthetic gas, the waste heat boiler in the gas production section also receives some semi-water gas, thereby producing superheated steam at 25 Kg/cm2. After power generation via differential pressure, this steam is supplied for use in the gas production process and other sections; no external steam boiler is used. ① The steam required for the conversion section is mainly supplied by the boilers located in the synthesis section, with a small amount supplied by the waste heat boilers from gas production. ② The heat for copper melt regeneration in the refining section is provided by the second water heater of the converter. In this concept, it is reasonable to improve the steam parameters for differential pressure power generation. Under this approach, 2,156 kilograms of steam can be generated per ton of ammonia, and differential pressure generation can produce 154 kWh of electricity. For a plant with a capacity of 20,000 tons, 500 KW generators can be used. If this scenario becomes a reality, the total energy consumption per ton of ammonia could reach 11,460,400 kcal. The above text provides a brief overview of the development history of the small-scale nitrogen fertilizer industry, the current status of energy conservation and consumption reduction, as well as potential areas for further improvement and innovation. Inevitably, there may be inaccuracies and mistakes; please feel free to point them out. Reference 1: “Design Technology for Small Nitrogen Fertilizers”, Issue 2, 1982; Issue 5. 2. Comrade Liu Zunsan’s speech at the National Red Flag Units for Small Nitrogen Fertilizers in May 1982. 3. Design Technology Center for Small-scale Ammonia Production of the Ministry of Chemical Industry, Vol. 1 and Vol. 2 of Compilation of Materials on Minor Reforms and Innovations to Reduce Consumption and Save Energy in Small Nitrogen Fertilizer Plants. 4. Shanghai Chemical Engineering Design Institute, “Utilization of Waste Heat from Small Fertilizer Plants – Concepts for Comprehensive Steam Balance”. 5. “Business Management”, Issue 9, 1982. 6. Hebei Provincial Petroleum and Chemical Industry Bureau, “Production and Process Management”. 7. Hebei University of Chemical Technology, “Basic Knowledge of Nitrogen Fertilizer Production”. 8. Gaocheng County Fertilizer Factory, “Preliminary Summary on Differential Pressure Waste Heat Power Generation”.

For medium-sized ammonia synthesis plants, energy conservation and emission reduction start with gas production. Coal selection, furnace modification. Add waste recycling incinerators. New technologies are adopted to replace the existing desulfurization, shift, decarburization, dimethyl process, and synthesis. Technologies such as low-temperature and pressure swing adsorption carbon removal can be employed.

1. Judging from the current situation, the key is to change the gas production method to an efficient coal-to-gas process, which will immediately reduce costs. 2. Depending on the conditions in the methanol market, if the market is favorable, an additional set of low-pressure methanol units with a pressure of 5.0 MPa will be added; in the dimethyl process, purification only will be carried out. As long as thermal balance can be maintained to minimize methanol production, the circulation pump will be stopped from operating. 3. Based on pressurized coal gasification, the syngas at the gasification outlet is sent directly to the shift system after washing; the shift process is modified to a sulfur-resistant full low-temperature shift process, and desulfurization is carried out using NHD or low-temperature methanol washing. On this basis, a new ammonia synthesis system has been installed with a production capacity of 180,000 tons; it operates at a pressure of 20–25 MPa. The original three small towers have been removed, and the operational energy consumption of the upgraded system will decrease significantly. It is best to use a completely new set; with technologies that have evolved from small nitrogen-based fertilizers, it is extremely difficult to achieve a significant reduction in energy consumption through merely partial modifications. It is best to install a new set of equipment with an appropriately increased air supply capacity, while using partial modifications to the old system as integrated utilization devices; such modifications depend mainly on the company’s comprehensive consideration and the determination of its decision-making level. This post was last edited by FEIJING on 2009-3-18 21:52.]

The heat transfer process in air-conditioning cooling equipment refers to the process by which hot and cold fluids exchange heat through a solid wall, that is, the process by which heat is transferred from the high-temperature fluid on one side of the solid wall to the low-temperature fluid on the other side. The heat transfer process generally consists of the heat conduction through the solid wall, as well as the convective heat exchange between the fluids on either side of the wall and the wall itself. Sometimes, there is also radiative heat exchange between the wall and the objects in the space surrounding it. The formula for calculating the heat transfer amount in a heat transfer process is also known as the heat transfer equation. The intensity of the heat transfer process is reflected by the value of the heat transfer coefficient, which refers to the amount of heat transferred per unit time per unit area of the wall, under an unit temperature difference between the hot and cold fluids; its unit is W/(m2·K). The reciprocal of the heat transfer coefficient is called the heat transfer resistance. For different heat transfer processes, the calculation expressions for the heat transfer coefficient and heat transfer resistance vary. Heat transfer processes that are commonly encountered in practical engineering, such as heat transfer in building envelopes and in various heat exchange devices, including the heat exchange between the working fluid in condensers and evaporators and the cooling medium as well as the material to be cooled, can often be classified as heat transfer through flat walls, circular tube walls, and ribbed walls. Recommended reading: More interesting logs -- http://bbs.hcbbs.com/home.php?mo ... &view=me&from=space