Research Report on Energy Saving and Consumption Reduction in Small-scale Nitrogen Fertilizer Production (Part 1)

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I. The historical role of low-nitrogen fertilizers in China’s fertilizer industry. China’s low-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 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 various raw materials. Using local materials, producing locally, and applying them on-site eliminates the need for long-distance transportation. Research conducted by the Soil and Fertilizer 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 equal 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 volumes, high consumption, high costs, and heavy 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 the improvement of enterprise management; it has carried out numerous minor reforms to reduce consumption and save energy, attached importance to 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 across the country from 1976 to 1981
Year: 1976, 1977, 1978, 1979, 1980, 1981, 1982.6
Profit/Loss (in 100 million yuan): –9.7, –8.9, –6.1, –4.1, –0.85, –0.69, –0.31
Average 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 across the country 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, Electricity consumption, Total energy consumption (10,000 kcal)
1976: 4,181, 2,239, 3,634
1981: 2,269, 1,458, 2,040
Percentage decrease: 43%, 34%, 43%

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 less than 2,000 kilograms per ton, while electricity consumption was 1,400 units 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 managed to meet 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 of over 2,900 kilograms per ton of ammonia produced by small-scale nitrogen fertilizer plants. 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 returns 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 producers across 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 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 chemical 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 chemical 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 considerable, 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 an example). The findings of this research along with our suggestions are presented as follows: http://static15.photo.sina.com.cn/middle/4eb68cd7t6147660dd6ee&000 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 plants; some say that successful production in this sector relies 70% on management and 30% on technology. 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 method, which includes ensuring that both types of coal enter the plant, weighing and measuring them, sorting them by quality, labeling them, removing all gangue, and screening out coal dust. It achieves the goals of 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 essential to ensure high reliability and low leakage rates for the compressors, which consume the most electricity; this is key to increasing productivity per unit of time and reducing energy 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 production; most of the machinery used is mechanical or semi-mechanical. During the production process, physical and chemical changes take place, and fertilizer production is characterized by high temperatures, high pressures, as well as 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. In the production process, a malfunction in any one station can 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 the catalyst temperature; this leads to the waste of large amounts of steam used for temperature control, and it also reduces 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 results in 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. ⒁The composition of the syngas is H2/N2S at 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. This includes 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 ensure sound comprehensive economic accounting, it is necessary first to improve enterprise management and establish appropriate staffing levels ； Second, it is necessary to strengthen the measurement instruments and inspection 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 managers, factory directors, departments, and workshops, and then further allocated at each level to work teams and individual employees. Once responsibilities are clearly defined, rewards are allocated on a percentage basis, strict assessments are carried out, and more work leads to greater rewards; this ensures that the post responsibility system is effectively linked to the company’s economic performance as well as 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 process parameters, inefficiencies in coal and electricity usage, and a system of equalitarian distribution. It’s the more advanced factories that also have many problems. Therefore, strengthening enterprise management, making great 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 effective management lies in having a cadre team with modernized skills, while also rapidly improving the cultural and technical proficiency of the workforce. Currently, all enterprises must carry out comprehensive training for all employees. All those who are employed, whether workers, cadres, leadership personnel, or technical staff, 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. http://static6.photo.sina.com.cn/middle/4eb68cd7t614765fe5785&000 ㈡ Focus on energy conservation and consumption reduction, and carry out efforts to tap potential, introduce innovations, and make improvements. 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. Using coal coke as raw material: Number of plants; Raw material coal in Kg/TNN3; Fuel coal or steam in Kg/TNN3; Electricity consumption in kWh/TNN3; Total energy consumption in 10 Kcae/TNN3; Cost in yuan/TNN3. For medium-sized ammonia plants: 31 plants, with values of 1329 for steam, 3090 for fuel coal, 1440 for electricity, 1704 for coal, and 312 for coke. For Zhejiang Small Nitrogen Fertilizer Plant: 48 plants, with values of 1156 for coal, 602 for fuel coal, 1289 for electricity, 1653 for steam, and 315.41 for total energy consumption. 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 primarily of carbonamide 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. Under normal circumstances, 30–40 kilograms of ammonium carbonate are 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, the 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, enterprises can, through restructuring, carry out planned and selective upgrades, gradually achieving standardization and serialization of equipment, thereby raising the 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 scale of a factory is a strategic planning issue for that factory. Those who do not plan for the future will surely face troubles soon. When expanding, optimizing, and renovating, the final scale must be taken into consideration; avoiding or minimizing the need to keep fixing problems one after another will help achieve lower investment costs and faster results. 2. Regarding equipment selection, 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 approach. That is, 320, 200 atmospheres, gas furnaces 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 gas generation furnace 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 would be uneconomical. Again, for capacities over 20,000 tons, using L-type compressors would result in a small fleet 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.