6 main fertilizer process technologies and NPK compound production method

Solid pellet/steam drum method compound fertilizer process technology

• Using monomer basic fertilizers such as: urea, ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium phosphate (monoammonium phosphate, diammonium phosphate, heavy calcium, ordinary calcium), potassium chloride (potassium sulfate), etc. as raw materials, after crushing After reaching a certain fineness, the material is agglomerated and granulated in the rolling bed of the drum granulator (or disk granulator) through humidification and heating.
• During the granulation process, if possible, a small amount of phosphoric acid and ammonia can be added to the drum granulator to improve the granulation conditions. The granulated materials are dried, screened, and cooled to obtain NPK compound fertilizer products. This is also one of the methods widely used internationally. In the early days, the United States and Southeast Asian countries such as India, Japan, and Thailand all used this method for production.
• The raw materials of the solid pellet method are widely available, the processing process is relatively simple, the investment is low, the production cost is low, the start-up is fast, the production flexibility is great, the grade adjustment of the product is simple and easy, and the versatility is strong. The raw materials used are all solid, and the raw materials are The reliance is not strong. Since it is a secondary processing process of basic fertilizer, there is almost no environmental pollution problem.
• Since most of the current basic fertilizers in our country are in powder and granular form, most of our country’s small and medium-sized compound fertilizer plants use this method. At present, this kind of production technology has become increasingly mature in China. The earliest unit in China to develop and own the intellectual property rights of this production technology and complete sets of equipment is Zhejiang Tongli Compound Fertilizer Machinery and Equipment Research Institute.

Slurry method compound fertilizer production process technology

• Using phosphoric acid and ammonia as raw materials, the neutralized slurry is coated and granulated in the ammonia granulator using a neutralizer and a tubular reactor, and some nitrogen, potassium and other substances are added during the production process, and then After drying, screening and cooling, NPK compound fertilizer products are obtained. This is a production method commonly used by major domestic and foreign fertilizer companies and factories for large-scale production.
• Phosphoric acid can be produced by decomposing phosphate rock with sulfuric acid. If conditions permit, commercial phosphoric acid can also be purchased directly to reduce investment and simplify production processes. The advantage of this method is that it can produce both ammonium phosphate and NPK fertilizer. At the same time, it also makes full use of the neutralization heat of acid and ammonia to evaporate the moisture of the material, reduce the granulation water content and drying load, and reduce energy consumption.
• The advantages of this method are: large production scale, low production cost, good product quality, and high product strength. Since it is usually necessary to construct supporting phosphoric acid plants and sulfuric acid plants, the construction not only requires large investments and a long cycle, but also involves the supply of phosphorus and sulfur resources and numerous environmental protection issues (such as phosphogypsum, fluorine, acid foam, acid mud, etc.), which are generally relatively It is suitable for phosphate rock processing bases and large-scale production with a small number of products.
• If purchased commercial phosphoric acid is used as raw material, the current stable source, transportation problems and price factors have to be considered. In recent years, due to the improvement of my country’s phosphoric acid industry technology and equipment level, wet phosphoric acid has entered the market as a commodity. Conditions, establishing phosphoric acid bases in areas with resources and conditions, and using commercial phosphoric acid to meet the needs of other areas for the development of high-concentration phosphorus compound fertilizers are forming a new idea and approach. Market demand will definitely promote the development of this industry, and also It will surely solve the demand problem of raw material phosphoric acid in many regions.
• Foreign companies with this kind of production technology mainly include Norsk Hydro of Norway, Incro and Espindsea of Spain, AZF and KT of France, Davy/TVA of the United States, etc.

Partial slurry method compound fertilizer production technology

• In recent years, on the basis of TVA urea, ammonium nitrate semi-slurry method and pellet method, China has developed a spray granulation process using urine or ammonium nitrate solution – that is, the partial slurry method. This technology uses urea and ammonium nitrate solution. Ammonium nitrate can form a high concentration solution at high temperature (95%)
• Due to the characteristics of high temperature, high solubility and large liquid phase of urine or ammonium nitrate solution, urine or ammonium nitrate concentrated solution is directly sprayed into the bed layer of the granulator, and the liquid phase provided by urine or ammonium nitrate solution is combined with other Solid basic fertilizer and Huike are coated and granulated together
• The partial slurry method can reduce the amount of water or steam added and the water content of granulation materials. It can also achieve the purpose of reducing granulation water content, drying load and energy consumption. The granulated materials are dried, screened and cooled to obtain (urea-based or nitro-based) compound fertilizer products.
• At present, the domestic units that develop and own the production technology of this intellectual property are Zhejiang Tongli Heavy Machinery, etc.

Molten prilling compound fertilizer granulation technology

• The production technology of melt oil cold granulation to produce high-concentration urea-based compound fertilizer is to use the urea solution, the intermediate product of the urea plant, with ammonium phosphate and potassium salts to successfully develop a high-concentration urea-based compound fertilizer with high quality, low energy consumption and less pollution. Production technology-melt granulation process.
• Melt granulation technology has been applied in chemical fertilizer production, such as urea tower spray granulation, nitric acid phosphate fertilizer tower spray granulation and biaxial granulation, ammonium nitrate tower spray granulation, urea ammonium phosphate tower Spray granulation, etc.
• The melting method compound fertilizer production process is still blank in China for manufacturing high-concentration urea-based compound fertilizers. This process does not require the largest investment and energy consumption of the drying system in traditional compound fertilizer production equipment, and because urea and urea-based compound fertilizers are not required. Due to the characteristics of fertilizer, it is especially suitable for the production of high-concentration compound fertilizers with ternary (N, P, K) and binary (N, K or N, P) urea-based and high nitrogen ratios.

Adventages of molten prilling compound fertilizer granulation method

Compared with commonly used compound fertilizer manufacturing processes, the melt granulation process has the following advantages:

1. Urea melt is directly used, eliminating the spray granulation process of urea melt, as well as the packaging, transportation, crushing of solid urea, etc., simplifying the production process.
2. The melt granulation process makes full use of the heat energy of the original molten urea. The moisture content of the material is very low, and no drying process is required, which greatly saves energy consumption.
3. The percentage of qualified product particles in production is very high, so the amount of material returned during the production process is small (almost none).
4. The product particles have a smooth and round surface, low moisture (less than 1%), are not easy to agglomerate, and the particles have high compressive strength (more than 30N), and have high market competitiveness.
5. The operating environment is good, there is no emission of three wastes, and it is a clean production process.
6. It can produce high nitrogen ratio urine-based compound fertilizer products.

Blending method(BB)bulk blending compound fertilizer production process

• The production process of bulk blended compound fertilizer is based on the nutrient ratio requirements, using various solid basic fertilizers of nitrogen, phosphorus, and potassium that do not undergo obvious chemical reactions and have basically the same particle size and roundness as raw materials, and are prepared through a certain blending method A blended fertilizer with evenly distributed nutrients.
• The processing process of bulk blending(BB)method is simple, the equipment investment cost and processing cost are relatively low, and it is a very practical and easy-to-promote method. However, this method places great emphasis on the particle size, weight and roundness of various basic raw materials during production, storage, transportation, and use. The degree is basically consistent, so that the mixture will not agglomerate and crush and have a low hygroscopic point.
• At present, the shape and specifications of basic fertilizers in my country do not meet this condition. Research shows that P2O5 and K2O in uniform fertilizers and P2O5 and K2O in blended fertilizers are absorbed by crop roots at different rates (6 times, 4.6 times). , there is a slight difference in fertilizer efficiency.
• In addition, the popularity of soil testing and fertilization in our country is not enough, and its products are not yet recognized and accepted by farmers in our country. Therefore, the application of this law is currently restricted to a certain extent in our country.
• Generally speaking, the blended fertilizer industry is a method of fertilizer production and use that can only be realized after chemical fertilizer production, sales and agricultural production have reached a higher level. It can reduce the cost of chemical fertilizer distribution and sales, make agricultural fertilization scientific, and help solve the problems of resource waste and chemical fertilizer pollution caused by excessive fertilization.

Extrusion fertilizer granulation method:

Extrusion granulation is a dry granulation process in which solid materials rely on external pressure to agglomerate. It has the following advantages:

1. The production process generally does not require drying and cooling processes, and is especially suitable for heat-sensitive materials, while saving investment and energy consumption.
2. The operation is simple and no three wastes are emitted during production.
3. It can produce high-concentration compound fertilizers with a lower concentration than ordinary compound fertilizers. Organic fertilizers and other nutrients can also be added as needed during production.

However, the extrusion granulation method also has shortcomings:

1. As the key equipment for extrusion granulation, the extruder consumes a lot of material during production and has a high failure rate due to problems in equipment manufacturing and the material of pressure parts.
2. The production capacity of the extruder is small and it is difficult to achieve large-scale production. Therefore, this method is generally used for production scales below 30,000 tons/year.
3. This method is currently mainly used for compound fertilizers such as rare earth ammonium bicarbonate. Zhejiang Tongli Heavy Machinery Manufacturing Co., Ltd. owns this production technology.

Conclusion:

In this article, we introduced 6 mainstream compound fertilizer production processes and described the advantages and disadvantages of various processes. For example, the drum steam granulation method has large output but high investment price, and the extrusion granulation method has low investment but low investment. Low yield and so on. In the next article we will introduce various compound fertilizer production processes in detail