Preparation method of compound fertilizer applying coal-fired boiler tail gas

Abstract

The invention discloses a method for preparing a compound fertilizer by using coal-fired boiler tail gas, and relates to the technical field of compound fertilizer preparation.According to the method, the coal-fired boiler tail gas is introduced into a drying kiln to participate in compound fertilizer particle drying treatment, heat of the coal-fired boiler tail gas is fully utilized, and heat energy consumption and production cost are reduced; meanwhile, elements in the coal-fired furnace tail gas are absorbed and utilized by the compound fertilizer, and compound fertilizer particles are changed into compound fertilizer particles capable of absorbing sulfur dioxide and nitrogen oxide under the action of citric acid and urea, so that the sulfur dioxide and the nitrogen oxide are converted into nutrients in the fertilizer, and the production cost of the compound fertilizer is reduced; one set of tail gas treatment equipment is reduced in the aspect of tail gas treatment, so that air pollution is reduced, and investment and operation cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of compound fertilizer preparation technology, and in particular to a method for preparing compound fertilizer using coal-fired boiler exhaust gas. Background Technology

[0002] In existing compound fertilizer production technologies, water vapor is required during the granulation process. The water vapor is generated by heating tap water from an externally installed coal-fired boiler. The carbon dioxide, water, sulfur oxides, nitrogen oxides, and calcium and magnesium ion-containing dust in the exhaust gas of the coal-fired boiler are usually directly discharged into the atmosphere at high altitude after being treated by a separate desulfurization and denitrification exhaust gas treatment device. The heat in the exhaust gas is not reused, and the sulfur oxides, nitrogen oxides, and calcium and magnesium-containing dust contained in the exhaust gas are not effectively utilized. Moreover, it requires the investment of an exhaust gas treatment system, resulting in high investment and operating costs.

[0003] Therefore, it is essential to provide a method for preparing compound fertilizer using coal-fired boiler exhaust gas to address the shortcomings of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing compound fertilizer using coal-fired boiler exhaust gas. This invention involves introducing coal-fired boiler exhaust gas into a drying kiln to participate in the drying process of compound fertilizer particles, making full use of the heat of the coal-fired boiler exhaust gas, reducing heat energy consumption and production costs. At the same time, the elements in the coal-fired boiler exhaust gas are absorbed and utilized by the compound fertilizer. Under the action of citric acid and urea, the compound fertilizer particles become compound fertilizer particles that can absorb sulfur dioxide and nitrogen oxides, converting sulfur dioxide and nitrogen oxides into nutrients in the fertilizer, reducing the production cost of compound fertilizer. In addition, it reduces the need for a set of exhaust gas treatment equipment, reducing air pollution while lowering investment and operating costs.

[0005] The above-mentioned objectives of the present invention are achieved by the following technical means.

[0006] A method for preparing compound fertilizer using coal-fired boiler tail gas is provided, comprising the following steps: S1: Raw material preparation, weighing and preparing urea, ammonium sulfate, 55% monoammonium phosphate, 60% potassium chloride, synthetic ammonium chloride and citric acid respectively; S2: Grinding and crushing. The prepared raw materials are conveyed to the chain mill for grinding and crushing via a mixing belt. S3: Granulation, after grinding and crushing, the raw materials are transferred to the granulator to granulate and form moist compound fertilizer granules; S4: Drying, the moistened compound fertilizer granules are conveyed to the drying kiln for drying; S5: Discharge, the dried granules are processed into finished fertilizer products; In step S3, water vapor, liquid urea, ammonia and sulfuric acid are introduced into the granulator during the granulation process. The granulator is connected to a coal-fired furnace, and a tap water source is connected to the outside of the coal-fired furnace. The coal-fired furnace heats the tap water to provide water vapor in the granulator. A tail gas pipe is connected to the coal-fired furnace, and the tail gas pipe is connected to the drying kiln in step S4. In step S4, a drying fan is connected to the drying kiln. The air inlet of the drying fan is connected to the exhaust gas pipe. The air inlet of the drying fan is also connected to a hot air furnace to provide hot air. The hot air is mixed with the exhaust gas from the coal-fired furnace and then sent into the drying kiln. The moist compound fertilizer particles are fully mixed with the exhaust gas from the coal-fired furnace and dried by heat exchange. Due to the ammonia overflowing from the surface of the moist compound fertilizer particles, an ammonia-containing liquid film is formed on the surface of the moist compound fertilizer particles. At the same time, under the action of citric acid and urea, the compound fertilizer particles become particles that can absorb sulfur dioxide and nitrogen oxides and convert them into nutrients. The moist compound fertilizer particles adsorb the ultrafine fly ash in the exhaust gas and form a uniform fly ash dust layer on the surface of the compound fertilizer particles, protecting the compound fertilizer particles and playing a role in preventing agglomeration. The compound fertilizer particles are dried by direct contact with the high-temperature flue gas and participate in the reaction of trace metal elements to form a stable nutrient structure.

[0007] Specifically, the rated evaporation capacity of both the coal-fired furnace and the hot blast stove is 6t / h. The coal-fired furnace and the hot blast stove are connected by pipes to the induced draft fan of the coal-fired furnace and the induced draft fan of the hot blast stove to guide the exhaust gas and hot air into the drying kiln.

[0008] Specifically, the drying kiln is 30 meters long and is filled with lifting plates. Drying fans are installed at both ends of the kiln, with an air volume of 82040-131000 m³ / h and a total pressure of 5650 / 4000 Pa.

[0009] Specifically, the granulator is also connected by pipes to a urea dissolving tank and a sulfuric acid tank. Concentrated acid pumps and urea pumps are installed on the pipes of the urea dissolving tank and the sulfuric acid tank, respectively, to pump sulfuric acid and liquid urea.

[0010] Specifically, in step S1, the formulation proportions are as follows: 15 parts ammonium sulfate, 45 parts 55% monoammonium phosphate, 14.8 parts 60% potassium chloride, 13.5 parts synthetic ammonium chloride, and 1 part citric acid.

[0011] Preferably, in step S1, urea, ammonium sulfate, 55% monoammonium phosphate, 60% potassium chloride, synthetic ammonium chloride, and citric acid are all weighed using separate measuring tapes and loss-in-weight scales.

[0012] Specifically, a gas distribution manifold is installed between the coal-fired furnace and the granulator, and the gas distribution manifold is also connected to the urea dissolving tank to introduce steam to prepare liquid urea.

[0013] This invention utilizes the heat from coal-fired boiler exhaust gas by introducing it into a drying kiln to dry compound fertilizer granules. This fully leverages the heat of the exhaust gas, reducing energy consumption and production costs. Simultaneously, elements in the exhaust gas are absorbed and utilized by the compound fertilizer. Under the action of citric acid and urea, the compound fertilizer granules become capable of absorbing sulfur dioxide and nitrogen oxides, converting them into nutrients in the fertilizer and reducing production costs. Furthermore, it eliminates the need for a separate exhaust gas treatment system, reducing air pollution and lowering investment and operating costs. Attached Figure Description

[0014] The invention will be further described with reference to the accompanying drawings, but the contents of the drawings do not constitute any limitation on the invention.

[0015] Figure 1 This is a flowchart of a method for preparing compound fertilizer using coal-fired boiler exhaust gas according to the present invention. Detailed Implementation

[0016] The present invention will be further described in conjunction with the following embodiments.

[0017] Example 1. like Figure 1 As shown, a method for preparing compound fertilizer using coal-fired boiler exhaust gas includes the following steps: S1: Raw material preparation. Urea, ammonium sulfate, 55% monoammonium phosphate, 60% potassium chloride, synthetic ammonium chloride, and citric acid are weighed and prepared separately. The formula ratios in step S1 are 15 parts ammonium sulfate, 45 parts 55% monoammonium phosphate, 14.8 parts 60% potassium chloride, 13.5 parts synthetic ammonium chloride, and 1 part citric acid. Urea, ammonium sulfate, 55% monoammonium phosphate, 60% potassium chloride, synthetic ammonium chloride, and citric acid are all weighed using separate metering belts and loss-in-weight scales. At the same time, a bag filter is installed during the raw material transportation process to prevent dust from flying during the transportation of raw materials.

[0018] S2: Grinding and crushing. The prepared raw materials are conveyed to the chain mill for grinding and crushing via a mixing belt. The chain mill feed belt is connected to the mixing belt containing the raw materials, and the chain mill discharge belt is connected to the granulator feeding mechanism.

[0019] S3: Granulation, after grinding and crushing, the raw materials are transferred to the granulator to granulate into moist compound fertilizer granules; In step S3, steam, liquid urea, ammonia, and sulfuric acid are introduced into the granulator during the granulation process. The granulator is connected to a coal-fired furnace, which is connected to a tap water source. The coal-fired furnace heats the tap water to provide steam for the granulator. A tail gas pipe is connected to the coal-fired furnace and is connected to the drying kiln in step S4. A gas separator is installed between the coal-fired furnace and the granulator. The gas separator is also connected to the urea dissolving tank to introduce steam to prepare liquid urea. Pipes on the granulator are connected to the urea dissolving tank and the sulfuric acid tank. Concentrated acid pumps and urea pumps are installed on the pipes of the urea dissolving tank and the sulfuric acid tank, respectively, to pump sulfuric acid and liquid urea. At the same time, ammonia is introduced into the granulator during the granulation process. Steam, 4 parts of liquid urea, 3.5 parts of ammonia, and 2 parts of sulfuric acid are introduced into the granulator and finally mixed with the solid raw materials to form moist compound fertilizer granules of 2mm-4mm.

[0020] S4: Drying. The moist compound fertilizer granules are conveyed to the drying kiln for drying. In step S4, a drying fan is connected to the drying kiln. The air inlet pipe of the drying fan is connected to the exhaust gas pipe. The air inlet of the drying fan is also connected to a hot air furnace to provide hot air. The exhaust gas of the coal-fired furnace is sent into the drying kiln. The moist compound fertilizer granules are fully mixed with the exhaust gas of the coal-fired furnace and dried by heat exchange. Due to the ammonia overflow on the surface of the moist compound fertilizer granules, an ammonia-containing liquid film is formed on the surface of the moist compound fertilizer granules. At the same time, under the action of citric acid and urea, the addition of citric acid can increase the reaction rate of sulfur dioxide in the exhaust gas, thereby achieving the desulfurization effect. The compound fertilizer granules become compound fertilizer granules that can absorb sulfur dioxide and nitrogen oxides and convert them into nutrients.

[0021] Moist compound fertilizer granules of 2mm-4mm are fed into a drying kiln with a cross-sectional area of ​​6 square meters and a length of 30 meters. Lifting plates at different angles are evenly distributed inside the kiln. The moist compound fertilizer granules form a uniform material curtain under the action of the rotating drying kiln and the lifting plates. At the same time, exhaust gas from a coal-fired furnace at 160-180 degrees Celsius is introduced. The heat of the exhaust gas from the coal-fired furnace is used to exchange heat with the material curtain formed by the moist compound fertilizer granules and dry it. The rated evaporation capacity of the coal-fired furnace and the hot air furnace is 6t / h. Pipes connected to the coal-fired furnace and the hot air furnace are used to guide the exhaust gas and hot air into the drying kiln.

[0022] Drying fans are installed at both ends of the drying kiln. The air volume of the drying fans is 82040-131000 m³ / h, and the air pressure under total pressure is 5650 / 4000 Pa. They are compatible with the 6-ton induced draft fan of the coal-fired furnace (air volume 21030 m³ / h, total pressure 2980 Pa) and the 6-ton induced draft fan of the hot blast stove (flow rate 27660-55165 m³ / h, total pressure 1019-702 Pa).

[0023] The surface of moist compound fertilizer granules contains ammonia, urea, and citric acid. During the heat exchange and heating process, these react with sulfur oxides, nitrogen oxides, and calcium and magnesium dust in the exhaust gas of the coal-fired furnace to produce ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite, nitrogen, water, carbon dioxide, calcium citrate, and magnesium citrate. Among these, the nutrients beneficial to crops are absorbed by the compound fertilizer, and the compound fertilizer granules are dried.

[0024] Urea reacts chemically with nitrogen oxides; ammonia reacts with sulfur dioxide and nitrogen oxides; citric acid reacts with calcium and magnesium insolubles. Urea reacts with nitrogen oxides: Ammonia reacts with sulfides and nitrogen oxides: The reaction of citric acid with calcium and magnesium salts: S5: Discharge. The dried granules are discharged as finished fertilizer. Finally, the dried compound fertilizer granules are screened, cooled, coated and packaged.

[0025] The compound fertilizer granules in this application, after being dried by exhaust gas, contain citric acid that reacts with metallic elements such as calcium, magnesium, and sulfur to form a complex state. Its effects on plants are mainly manifested in three aspects: maintaining stable cell structure and balancing nutrient supply, promoting metabolic activities and enhancing stress resistance, and improving yield and quality.

[0026] Balanced nutrient supply: Medium-level elements such as calcium, magnesium, and sulfur are essential nutrients for crop growth, participating in key physiological processes such as cell wall formation, chlorophyll synthesis, and protein metabolism. For example, calcium stabilizes cell structure, magnesium is a core component of chlorophyll, and sulfur participates in amino acid and protein synthesis. Adding these elements to compound fertilizers can compensate for soil nutrient imbalances, especially suitable for low- to medium-yield fields, with yield increase potential reaching 5%-50%. Enhancing stress resistance: Medium-level elements can improve crops' resistance to drought, cold, and pests and diseases. For example, calcium can enhance root development and reduce the risk of lodging; magnesium optimizes photosynthetic efficiency and improves energy metabolism; sulfur inhibits pathogen growth by regulating cell sap pH. Improving yield and quality: Applying compound fertilizer containing medium-level elements to crops such as wheat and corn can make the stems thicker and the leaves more robust, ultimately increasing yield. At the same time, it can improve the quality of agricultural products, such as increasing protein and sugar content and improving fiber strength.

[0027] This invention utilizes the heat from coal-fired boiler exhaust gas in a drying kiln to dry compound fertilizer granules, thereby reducing heat energy consumption and production costs. Simultaneously, elements in the exhaust gas are absorbed and utilized by the compound fertilizer. Under the influence of citric acid and urea, the compound fertilizer granules become capable of absorbing sulfur dioxide and nitrogen oxides, converting them into nutrients in the fertilizer and reducing production costs. Furthermore, it eliminates the need for a separate exhaust gas treatment system, reducing air pollution and lowering investment and operating costs.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing compound fertilizer using coal-fired boiler exhaust gas, characterized in that: Includes the following steps: S1: Raw material preparation, weighing and preparing urea, ammonium sulfate, 55% monoammonium phosphate, 60% potassium chloride, synthetic ammonium chloride and citric acid respectively; S2: Grinding and crushing. The prepared raw materials are conveyed to the chain mill for grinding and crushing via a mixing belt. S3: Granulation, after grinding and crushing, the raw materials are transferred to the granulator to granulate and form moist compound fertilizer granules; S4: Drying, the moistened compound fertilizer granules are conveyed to the drying kiln for drying; S5: Discharge, the dried granules are processed into finished fertilizer products; In step S3, water vapor, liquid urea, ammonia and sulfuric acid are introduced into the granulator during the granulation process. The granulator is connected to a coal-fired furnace, and a tap water source is connected to the outside of the coal-fired furnace. The coal-fired furnace heats the tap water to provide water vapor to the granulator. A tail gas pipe is connected to the coal-fired furnace, and the tail gas pipe is connected to the drying kiln in step S4. In step S4, a drying fan is connected to the drying kiln. The air inlet of the drying fan is connected to the exhaust gas pipe. The air inlet of the drying fan is also connected to a hot air furnace to provide hot air. The hot air is mixed with the exhaust gas from the coal-fired furnace and then sent into the drying kiln. The moist compound fertilizer particles are fully mixed with the exhaust gas from the coal-fired furnace and dried by heat exchange. Due to the ammonia overflowing from the surface of the moist compound fertilizer particles, an ammonia-containing liquid film is formed on the surface of the moist compound fertilizer particles. At the same time, under the action of citric acid and urea, the compound fertilizer particles become particles that can absorb sulfur dioxide and nitrogen oxides and convert them into nutrients. The moist compound fertilizer particles adsorb the ultrafine fly ash in the exhaust gas and form a uniform fly ash dust layer on the surface of the compound fertilizer particles, protecting the compound fertilizer particles and playing a role in preventing agglomeration. The compound fertilizer particles are dried by direct contact with the high-temperature flue gas and participate in the reaction of trace metal elements to form a stable nutrient structure.

2. The method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 1, characterized in that: The rated evaporation capacity of both the coal-fired furnace and the hot blast stove is 6t / h. The coal-fired furnace and the hot blast stove are connected by pipes to the induced draft fan of the coal-fired furnace and the induced draft fan of the hot blast stove to guide the exhaust gas and hot air into the drying kiln.

3. The method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 2, characterized in that: The drying kiln is 30 meters long and is filled with lifting plates. The drying fan is installed at both ends of the drying kiln. The air volume of the drying fan is 82040-131000 m³ / h and the air pressure under total pressure is 5650 / 4000 Pa.

4. The method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 3, characterized in that: The granulator is also connected by pipes to a urea dissolving tank and a sulfuric acid tank. Concentrated acid pumps and urea pumps are respectively installed on the pipes of the urea dissolving tank and the sulfuric acid tank to pump sulfuric acid and liquid urea.

5. The method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 4, characterized in that: In step S1, the formulation proportions are as follows: 15 parts ammonium sulfate, 45 parts 55% monoammonium phosphate, 14.8 parts 60% potassium chloride, 13.5 parts synthetic ammonium chloride, and 1 part citric acid.

6. The method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 5, characterized in that: In step S1, the urea, the ammonium sulfate, the 55% monoammonium phosphate, the 60% potassium chloride, the synthetic ammonium chloride, and the citric acid are all weighed using separate metering tapes and loss-in-weight scales.

7. A method for preparing compound fertilizer using coal-fired boiler tail gas according to claim 6, characterized in that: A gas distribution manifold is installed between the coal-fired furnace and the granulator. The gas distribution manifold is also connected to the urea dissolving tank to introduce steam for the preparation of liquid urea.

Images