Production status of NPK compound fertilizers at home and abroad and development trends of compound fertilizer enterprises in China

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1. Production status of NPK compound fertilizers at home and abroad. According to statistics from the Food and Agriculture Organization of the United Nations, global fertilizer production in 1995 was 350 million tons, of which 120 million tons contained the main nutrients essential for plants, namely N+P2O5+K2O. Between 1990 and 1995, the International Fertilizer Development Center (IFDC) conducted research on the production of various fertilizers, with a focus on compound fertilizers. In 1994, the global production volume and proportion of different types of fertilizers were as follows: 178 million tons of single-component fertilizers, accounting for 54% ； 50 million tons of bulk blended fertilizers, 15% ； Granular fertilizers: 46 million tons, 14% ； 23 million tons of binary fertilizer, 9% ； 25 million tons of liquid fertilizer, 8%. After the mid-1970s, urea and ammonium phosphate experienced the fastest growth in world fertilizer production. In 1990, urea accounted for 40% of the total production of nitrogen fertilizers. In 1997, the consumption of ammonium phosphate accounted for 50% of the world’s total phosphatic fertilizer consumption. Although the production and use of chemical fertilizers in developed countries have declined since the mid-1990s, the degree of combination of P and K nutrients there is much higher than that in developing countries; Table 1 presents the data compiled by the International Fertilizer Association in 1997. In 1997, 15% of the world’s total nitrogen fertilizers, 66% of phosphorus fertilizers, and 30% of potassium fertilizers were processed into compound fertilizers. Table 1: Composite fertilizer rate % for certain countries and regions in 1997. ** or region: NP2O5K2O. United States: 1994, 33%; Western Europe: 28%, 87%, 69%; India: 13%, 83%, 31%; China: 10%, 25%, –; World average: 14.5%, 6%, 5.8%. The main types of composite fertilizers include: non-granular composite fertilizers, uniformly granulated composite fertilizers, pelletized mixed fertilizers, and fluid composite fertilizers. The development of compound fertilizers varies depending on the climate, crops, soil, and national conditions in different regions. The use of compound fertilizers in the United States dates back over a century, and it has gone through all the various stages of production and use of such fertilizers: in the 1948/49 farming year, non-granular mixed fertilizers accounted for 69.2% of the total 18.542 million tons of fertilizers consumed in the U.S. In 1960, the total fertilizer consumption in the United States was 23 million tons, of which 12 million tons were in the form of uniform granular NPK fertilizers, accounting for 52% of the total. There were 260 factories that produced granular compound fertilizers; our factory is at this same level today, meaning we are more than 40 years behind others. With the scaling up and mechanization of agricultural farming ； Improvement of basic fertilizer varieties in the field of chemical fertilizers, with large-scale factories located in resource-rich areas for production ； Agricultural service activities are widespread across the country. By 1995, mixed fertilizers accounted for 46% of total fertilizer consumption, liquid fertilizers accounted for 37.2%, *ao acid an and ammonium phosphate used for direct application made up 12.6%, while balanced NPK fertilizers accounted for only 4.2%. If our factory wants to get out of this difficult situation (without modifying the existing equipment), it should pursue the path of producing blended fertilizers. The reason for this is that granulation plants can address the granulation issues associated with N-K and P-K fertilizers. With several grades of N-K, P-K, and N-P base fertilizers, along with commercially available urea and ammonium phosphate, it is possible to prepare NPK blends in any desired ratio. Equip whatever the user needs; there is no longer a need for frequent changes in production, allowing for scaled and standardized manufacturing. Costs can be significantly reduced, as urea and ammonium phosphate are available commercially and do not require granulation. Western Europe is the birthplace of fertilizer technology. However, before World War II, the focus was on producing single-element fertilizers; after the war, emphasis was shifted to the production of compound fertilizers. During the 1970s and 1980s, it was the region with the highest production of compound fertilizers in the world. In the early 1980s, there were 140 compound fertilizer plants in the region, with a total production capacity of 32 million tons per year. By the end of the 1980s, due to rising environmental regulations, political reforms in Eastern Europe, and other factors, the use of fertilizers decreased. Fertilizer production underwent processes of consolidation and closure, resulting in the number of factories dropping to 95, with a total production capacity of 27 million tons per year. With the mergers of factories, the total number of companies operating in the fertilizer industry also decreased from 70 in the 1970s to 29 in the 1980s. Most products are sold within the home country and Western Europe, with only 10% of the products being sold to regions outside Western Europe. Russia’s production capacity for compound fertilizers is approximately 13 million tons per year, while that of the Eastern European countries is around 7 million tons per year. Compound fertilizers account for ~20% of the region’s fertilizer consumption. The proportion of compound fertilizers in India is higher than that in China. The production of large-scale urea-phosphate-ammonium compound fertilizers began in the late 1960s with the help of the United States. At the end of the 1960s, there were plans to develop mixed NPK production on the model of the United States. During the implementation of the plan, it was found that no pellet fertilizer manufacturers were available to produce pelletized fertilizers; as a result, it became difficult to find manufacturers capable of producing blended fertilizers. Through years of practice, it has been found that granulating compound fertilizer plants require low investment and yield quick results, making them an excellent method for increasing the production of compound fertilizers. By 1975, India had 40 granular compound fertilizer plants, accounting for 35% to 40% of India’s total compound fertilizer production. The scattered granular compound fertilizer plants have had a significant impact on agricultural production in India. At the end of the 1990s, India had over 70 compound fertilizer plants with an annual production capacity of 30,000 to 100,000 tons each. The ingredients of Indian granular compound fertilizers mainly include urea, ammonium phosphate, and potassium chloride, with small amounts of superphosphate and phosphate rock powder. The product specifications are mostly high-concentration products, such as 18‑18‑10, 15‑15‑15‑5 (S), 12‑12‑17‑2 (MgO). Due to Europe’s geography, climate, agriculture, and lack of sulfur resources, the production of chemical fertilizers and compound fertilizers has always focused on **synthetic products. In 1990, the world produced and consumed 4.33 million tons of P2O5 in the form of compound fertilizers manufactured using nitric phosphate fertilizer technology (equivalent to 20 million tons in terms of physical volume), accounting for 10.5% of the world’s total P2O5 production. With an ample supply of sulfur in recent years, fertilizer use in Europe has decreased, leading to a drop in the production of phosphate fertilizers to 3.2 million tons of P2O5. In 2000, China produced 31.857 million tons of chemical fertilizers (N+P2O5+K2O), of which 23.981 million tons were N, 6.63 million tons were P2O5, and 7.367 million tons were NPK compound fertilizers. The actual production volume of urea reached 30.701 million tons per year. In 2000, China imported 3.6 million tons of DAP, 5.992 million tons of potassium chloride, and 1.985 million tons of NPK compound fertilizers. The production volume and total application amount of compound fertilizers remain low; it is still necessary to develop production in order to increase supply. 2 Types and Applications of Compound Fertilizer Production Technologies. The development of compound fertilizer production is based on the observation in agricultural practice that fertilizers containing multiple nutrients enable crops to grow better and yield higher yields. Agronomists attribute this phenomenon to the synergistic effects among nutrients. The main explanation is that the simultaneous presence of nutrients enables plants to easily obtain various nutrients they need, leading to more developed roots and thus an improved ability of the plants to absorb and utilize different nutrients... which is more conducive to plant growth. In this regard, the research report by James T. Thorup of the American company Chevron Chemicals, titled “The Role of Uniform Compound Fertilizers in Achieving Balanced Fertilization,” provides strong evidence. Many researchers have also reached the same conclusion. Nitrogen fertilizer is the nutrient that crops require in the largest quantities. However, nitrogen fertilizers are prone to leaching and decomposition losses, so it is advisable to apply them separately in multiple doses; as a result, the proportion of compound fertilizers made from them is low. The types of production technologies for compound fertilizers and their applications are as follows: (1) Dry mixing of non-granular fertilizers. This was the main type of fertilizer in the United States before the 1950s, with specialized production technologies and equipment, formulations, and anti-caking measures. The production scale is mostly 10,000 to 50,000 tons per year. (2) Pelletization of mixed dry materials originated in the UK and is widely used in Europe, the United States, Australia, and Japan. India, China, and Thailand also widely used it in the 1960s to 1990s. (3) Dry material granulation with acid addition and ammonia introduction: In this dry material granulation technique, acid solution is sprayed, along with *ao acid or ammonia solutions as well as ammonia gas; the neutralization reaction takes place simultaneously with granulation, and this method is most widely used in the United States. With the availability of commercial phosphoric acid and the successful development of tubular reactors, the mid-1970s marked new achievements in compound fertilizer technology. (4) Slurry granulation method: Compound fertilizers such as the ammonium phosphorus sulfate series based on ammonium phosphate, and nitrate-phosphate compound fertilizers derived from the decomposition of phosphate rocks using a mixture of nitric acid and phosphoric acid are mainly produced using the slurry granulation method. The slurry method is suitable for the large-scale production of compound fertilizers in comprehensive chemical plants. 　　　　 The granulation equipment in the compound fertilizer workshop includes: twin-axis horizontal granulators, spray granulators, and rotary drum granulators, all of which convert slurry into pellets through feedback of material. For urea-phosphatic ammonium compound fertilizers, only the concentrated phosphoric acid-pipe reactor process can achieve good operating conditions. (5) Melting granulation: In the production of phosphoric acid fertilizers and ammonium nitrophosphate-based compound fertilizers, after obtaining a high-concentration molten slurry (>96%), granular products can be produced using a melting-spray granulation process. Ammonium phosphate urea-based compound fertilizers can also be produced using the melt granulation process, but this is only suitable when monoammonium phosphate is used as the raw material, and the m(N):m(P2O5) ratio of the product must be 1:1 or higher. (6) Extrusion granulation is suitable for the small-scale production of NPK compound fertilizers. Because of the poor appearance of the particles, obtaining particles with a good appearance requires complex production processes and equipment. Large-scale production of granular potassium fertilizer and granular sulfuric acid is more suitable, as other methods for producing granular potassium fertilizer yield inferior results compared to the extrusion method. (7) NPK blending: Under the influence of the United States, Ireland, Canada, and Brazil primarily use NPK blending technology. The blending method also has a certain influence in some countries in South America, Europe, Japan, and Africa. In 1996, the production of blended fertilizers in North America was 18.5 million tons in terms of physical volume; in Brazil it was 10.8 million tons, in Western Europe 5.6 million tons, in Latin America **1.2 million tons, in Asia/Oceania 2.7 million tons, and in Africa 0.7 million tons. The total amount was 39.5 million tons. The growth trend of blended fertilizers indicates that it is technically and economically viable. The blending plant may seem simple to construct on the surface, but in reality it requires a high level of capacity for producing basic fertilizers, and it becomes more meaningful when combined with methods such as soil testing and fertilizer application. In the absence of basic fertilizer production, it is reasonable to purchase granular basic fertilizers and mix them into NPK formulations of different specifications for use in agriculture. To reduce environmental pollution caused by phosphate production, it is reasonable to shut down phosphate plants and use purchased standard granulated fertilizers to produce blended NPK, replacing the previously produced granulated NPK; this is itself a process of development. Granulation technology and blending technology can be combined. Pelletizing plants can solve the pelletization problems of N-K and P-K fertilizers. With several grades of basic fertilizers such as N-K, P-K, and N-P, it is possible to prepare NPK blends in any desired ratio. (8) Fluid compound fertilizers: Fluid compound fertilizers are divided into three types: liquid type, suspension type, and slurry type. It already accounts for a significant proportion of the total fertilizer use in the United States. Fluid fertilizers have low production costs and high application efficiency, making them particularly suitable for fertilization in large-scale mechanized farms. However, it is only possible to apply it after meeting various corresponding conditions. 3 The technical approaches suitable for the development of compound fertilizer production by nitrogen fertilizer enterprises in our country: Urea is the nitrogen fertilizer with the lowest production cost per unit of nitrogen. Based on calculations and actual production, expressed per unit N, the production cost of urea is approximately 90% of that of *ao acid an, and 80% of that of sulfuric acid an. *Nitric acid used in the production of AO acid serves to decompose phosphate rocks to produce available phosphorus, which ultimately becomes the nitrogen component of fertilizers. From an economic perspective, urea-based compound fertilizers and phosphate nitrate-based compound fertilizers are superior to sulfur-based compound fertilizers. Urea production in our country accounts for about 60% of the total nitrogen fertilizer production; it is therefore only natural for urea to serve as the nitrogen source in compound fertilizers. For urea manufacturers, we recommend the following compound fertilizer production technologies: (1) Utilizing the concentrated urine (>95%) from urea plants, along with purchased ammonium phosphate powder, crystalline potassium chloride (or potassium sulfate), other ingredients, and fillers, to produce high-concentration compound fertilizers of various specifications. The compound fertilizer workshop is located near the urea workshop (200–500 m away). The process of the production unit is shown in the figure. Basic fertilizer – metering system – raw material conveyor belt – chain grinder – granulator – No. 1 dryer – coarse sieve – No. 2 dryer – cooler – finished product sieve – coating machine – metering and packaging scale. Auxiliary systems: clean water – flow meter – dissolution tank – spraying pump – metering system; solid urea – belt-type metering scale; steam; urine from the urea production plant – nozzle – granulator. Granulation mechanism: The granulated urea is fed into the urea melting tank after being metered continuously. The metering system automatically adjusts the amount of water added based on the amount of urea, thereby maintaining a stable urea concentration. At the same time, based on the set production volume, the total NPK content of the compound fertilizer, and the content of each individual nutrient, the metering control system automatically adjusts the flow rate of urine. The urine melted in the melting tank is pressurized by a melting pump and then sprayed through special nozzles to form mist-like droplets. Upon cooling, these droplets turn into semi-liquid, semi-solid granulation nuclei, which are sprayed onto the material already measured in the batching system; there they bond together to form particles, which are gradually rounded into qualified particles before being sent to the drying system. Fog-like droplets serve as the source for forming pellets; even without the use of steam, they can significantly increase the rate of pellet formation. Since steam is not used, the moisture content of the material to be granulated is reduced, thereby lowering the load on the dryer ； At the same time, since the size of the fog-like droplets is essentially consistent, when they adhere to the material inside the granulation machine, the thickness of the adhesive layer remains roughly the same, resulting in particles that are round, smooth, and have uniform particle sizes. 　　　 The characteristic of this process is that it uses urea slurry as the liquid phase, replacing steam granulation, and the source of urine can be selected as needed ； The original process route of the granulation method is retained, with no need to make any changes to the existing equipment ； Reduced the moisture content in the granules, thereby lowering the load on the dryer ； It increased the granulation and balling rate, thereby boosting yield ； Product quality has been improved. The product is available in various specifications, making it particularly suitable for producing products with a high nitrogen content ； The amount of material returned is low, and the production efficiency is higher by ~30% compared to granulation using fully solid ingredients, resulting in reduced operating costs ； The scale of single-series plants is 50,000 to 200,000 tons of finished products per year. The scale should not be too large to allow for changes in product specifications. The total investment for a plant with an annual production capacity of 100,000 tons of compound fertilizer, including civil engineering costs, is 10 million yuan. Slight increases or decreases are possible based on the factory’s original conditions. (2) Ammonium phosphoric acid slurry (produced in a pipe reactor) is granulated together with solid urea, potassium salts, and other ingredients to produce compound fertilizers. The process is similar to (1), but supply of commercial phosphoric acid (~50% P2O5) is required. Equipment for supplying acid and ammonia, along with measuring instruments, are arranged in front of the granulation unit; phosphoric acid, sulfuric acid, washing liquid, and ammonia are added to the pipe reactor located at the front end of the granulator. The concentrated slurry discharged from the pipe reactor is sprayed onto the bed in the granulator for granulation. The granulated material is then processed through various steps to yield the final product. Features: ① Compared to Plan (1), it includes a storage system for sulfuric acid and a pipeline reactor system; in addition, higher requirements are placed on the materials used for exhaust gas washing equipment. As a result, the investment cost is 30% higher than that of Plan (1). ②　The particle appearance of the compound fertilizer product is worse than that in Scheme (1). Because the viscosity of the sulfuric acid AN slurry is much higher than that of urine. There is a strong tendency to bind into granules. Reducing the slurry concentration increases the moisture content of the granulated material, leading to a series of adverse effects. This technology has been applied in domestic phosphate ammonium plants as well as companies such as Qinhuangdao China-Arabia Fertilizer Company. This process can be used to build a workshop for urea-phosphate-ammonium compound fertilizers. (3) Double-slurry feedback granulation process: The concentrated slurry generated in the pipeline reactor through the reaction of concentrated phosphoric acid, flue gas washing liquid, and gaseous ammonia, along with urine from the urea plant and potassium salts, are granulated inside a rotating drum. Features: ① A large amount of liquid phase is present during granulation, requiring a feedback ratio of more than 4; as a result, the material flow rate through all equipment in the system increases. ② Maintaining a high return ratio means a high material crushing load, as well as higher loads for exhaust gas treatment and ventilation/dust collection. The amount of water introduced into the wet scrubber has increased. ③ Operational difficulties such as excessive granulation, unbalanced return material, and unbalanced washing liquid can occur. ④ The investment cost is more than 60% higher than that of Plan (1). (4) Melting granulation method: Concentrated urine is mixed with preheated ammonium phosphate powder and potassium salt powder to form a molten mixture, which is then granulated by spraying to produce the compound fertilizer. Features: ① Utilizes the physicochemical properties of eutectic mixtures formed between urea and MAP, and between urea and MOP, to enable direct granulation of the melt. ② The production process is relatively short, the powder ratio is low, and the particle quality is good. ③ Suitable for producing compound fertilizers with a high nitrogen ratio. Product specifications can be easily changed. ④ The investment cost is comparable to that of Plan (1). ⑤ Ammonium monophosphate is the only allowable phosphorus source. (5) Urea and potassium chloride melt granulated standard particle size N-K granular fertilizer. Several grades of N-K granular materials are mixed with N-P (anhydrous sulfate-based N material) to produce a variety of blended compound fertilizers with different N, P, and K ratios. (6) Nitric-phosphoric acid mixture method for nitric phosphate fertilizer: It is practical for nitrogen fertilizer plants that produce nitric acid to use the nitric-phosphoric acid mixture method to manufacture nitric phosphate fertilizer. One of the conditions is having a supply channel for commercial phosphoric acid. When the water solubility of P2O5 in the product is 50%, 69% of the P2O5 in the product comes from phosphoric acid. This post was last edited by Park Seok on 2009-3-26 19:28]