CN1132802C

CN1132802C - Process for producing compound N-P-K fertilizer

Info

Publication number: CN1132802C
Application number: CN 00101342
Authority: CN
Inventors: 郑秀兴; 洪细安; 刘琨; 黄式鹏; 江寿良; 黄平; 郑光辉
Original assignee: GUIXI CHEMICAL FERTILIZER PLANT JIANGXI
Current assignee: Jiangxi Guixi Fertilizer Co., Ltd.
Priority date: 2000-02-01
Filing date: 2000-02-01
Publication date: 2003-12-31
Anticipated expiration: 2020-02-01
Also published as: CN1306955A

Abstract

The present invention provides a process for producing nitrogen phosphorus potassium compound fertilizer by using phosphonic acid as base materials. A preneutralization normal pressure reaction and the pressurizing reaction of a tubular reactor are organically combined. The optimal combination of the reasonable distribution of materials and reaction procedures is realized in theory for the reversible reaction of the phosphonic acid and ammonia, and the problem of high ammonia escaping rate generally existing in the granulating process of the phosphorus and ammonium production technology in the world at present is successfully solved. The process has the advantages of high utilization rate of the ammonia and low production cost, and the produced product has the advantages of high nitrogen content, little water content, high granule intensity, hard agglomeration of the product, no floating in water, etc.

Description

Process for producing nitrogen-phosphorus-potassium compound fertilizer

The invention relates to a fertilizer, in particular to a process for producing a nitrogen-phosphorus-potassium compound fertilizer by taking phosphoric acid as a basic raw material.

At present, the production process of nitrogen-phosphorus-potassium compound fertilizer based on phosphoric acid at home and abroad mainly comprises (a) preneutralization and drum ammonization granulation process, wherein the neutralization process of phosphoric acid and ammonia is carried out in two steps, one step is carried out in a preneutralization tank, and the other step is carried out in a granulator, the heat released by ammonia neutralization is utilized to evaporate a large amount of water, and NH generated by the reaction of ammonia and phosphoric acid in the preneutralization tank₃And H₃PO₄The slurry is pumped into a granulator, and simultaneously a certain amount of sulfuric acid is required to be added into the granulator to balance the heat required by evaporating water, the water quantity carried into the granulator by the processslurry is high, a high material return ratio and a large drying system are required, and a large-capacity washing system is required to be prepared because the secondary ammoniation of the granulator belongs to gas-solid phase reaction, and in addition, a secondary ammoniation device, a slurry spray pipe, a phosphoric acid spray pipe, a crossbeam and other internal parts are arranged in the granulator, so that the operation rate of equipment is seriously influenced; the process of the (two) tubular reactor is a new process developed in the last two decades, a high-efficiency tubular reactor is adopted to replace a groove-type pre-neutralizer to carry out neutralization reaction of ammonia, the process still needs to carry out gas-solid phase secondary ammoniation granulation reaction in a granulator, so the problems of high escape rate of secondary ammoniation ammonia, low equipment running rate and the like still cannot be solved, although the ESPINDESA single-tube reactor process of the Spanish TR company solves the problem of secondary ammoniation in a rotary drum granulator, the internals of the granulator are greatly reduced, but the process for producing nitrogen, phosphorus and potassium needs to use concentrated ammonia as the process of other tubular reactorsThe condensed phosphoric acid needs to be supplemented with a large amount of solid nitrogen such as ammonium sulfate and the like in the returned materialFertilizer and the ammonia escape rate of the granulator is higher.

Therefore, the invention aims to provide a process for producing the nitrogen-phosphorus-potassium compound fertilizer by using dilute phosphoric acid and sulfuric acid, which can reduce the escape rate of ammonia, ensure high equipment operation rate and overcome the defects of the process.

The object of the present invention can be achieved by the fact that the starting material required for the invention is less than or equal to 24% PO₂O₅Diluted phosphoric acid, 98% concentrated sulfuric acid, potassium chloride and liquid ammonia, and its production process is as follows:

1. adding concentrated sulfuric acid accounting for 10-20% of the total weight of the raw materials, dilute phosphoric acid accounting for 5-12% of the total weight of the raw materials and a washing liquid from a washing system into a preneutralizer from the top of the preneutralizer, wherein the using amount of the washing liquid is 3.45 times of that of the concentrated sulfuric acid (the N/P corrected molecular ratio of the washing liquid is less than 0.3, and the specific gravity is 1.30-1.35), and gaseous ammonia accounting for 5-12% of the total weight of the raw materials from an ammonia evaporator enters the preneutralizer from the bottom tangential direction of the preneutralizer, and in the preneutralizer, the concentrated sulfuric acid, the phosphoric acid and the washing liquid are fully mixed with the gaseous ammonia and react to prepare qualified slurry (the corrected molecular ratio of the slurry is 0-0.5 or 1.2-1.4, and the specific gravity is 1.47-1.51), the slurry has good fluidity and less corrosivity, can be conveyed by a common centrifugal pump, and the heat generated by the, the reaction tail gas is washed in a Venturi scrubber. The main chemical reaction formula is as follows:

(1)、

(2)、

(3)、

2. conveying qualified slurry obtained by the reaction of the preneutralizer to a tubular reactor by a pump, maintaining the pressure before the qualified slurry enters the tubular reactorto be 0.5Mpa, carrying out the tubular reactor from the head part of the tubular reactor by gas ammonia which accounts for 2-8% of the total weight of raw materials and maintains the pressure before the gas ammonia to be 0.5Mpa, introducing concentrated sulfuric acid which accounts for 5-10% of the total weight of the raw materials into the tubular reactor, maintaining the pressure before the gas ammonia to be 0.5Mpa, rapidly and fully mixing the gas ammonia, the slurry and the added concentrated sulfuric acid in the tubular reactor, reacting with free phosphoric acid in the sulfuric acid and the slurry to obtain high-temperature slurry with the temperature of 160-, the main components of the return material are dust collected by a system, the crushed material and part of finished product particles are screened, potassium chloride and solid nitrogen fertilizer enter a granulator, wherein the dosage of the potassium chloride is 12-24% of the total weight of the raw materials, the material rolls in the granulator to form particles, the finished product material with the water content of 2.0-3.0% is discharged from the tail part of the granulator and enters a dryer for drying, the molten slurry quickly discharged from a tubular reactor is flashed in the granulator at the moment of being sprayed on a granulation return material bed layer, most of the water content in the slurry is pumped out by a tail gas fan and sent to a washing system for washing, and the main chemical reaction formula is as follows:

(1)、

(2)、

(3)、

3. the tail gas of granulation, the tail gas of reaction and the tail gas of equipment air draft are sent to an RGV Venturi scrubber,the dried tail gas is sent to a dryer Venturi scrubber and is respectively washed by dilute phosphoric acid, concentrated sulfuric acid and circulating washing liquid, and then the tail gas is sent to a horizontal scrubber through respective draught fans to remove ammonia and fluorine and then is discharged into the atmosphere through a chimney, wherein the dosage of the dilute phosphoric acid and the concentrated sulfuric acid entering the Venturi scrubber is respectively 30-40% and 1-3% of the total weight of the raw materials.

4. Drying, screening and cooling the granulated material to obtain the nitrogen-phosphorus-potassium compound fertilizer.

The embodiment takes 1000 tons of nitrogen-phosphorus-potassium compound fertilizer produced per day as an example: the gas ammonia preneutralizer is 4.69 tons/hour, the concentrated sulfuric acid preneutralizer is 8.33 tons/hour, the diluted phosphoric acid preneutralizer is 4.64 tons/hour, the gas ammonia is carried out in the tubular reactor for 2.78 tons/hour, the concentrated sulfuric acid is 4.04 tons/hour when entering the tubular reactor, the potassium chloride is 10.13 tons/hour when entering the granulator, the diluted phosphoric acid is 18.55 tons/hour when entering the venturi for washing, and the concentrated sulfuric acid is 1.1 tons/hour when entering the washer. The invention organically combines the preneutralized normal pressure reaction and the pressurized reaction of the tubular reactor, theoretically realizes the optimal reasonable material distribution and reaction procedure combination for the reversible reaction of the phosphoric acid and the ammonia, successfully solves the problem of high escape rate of the ammonia commonly existing in the granulation process of the ammonium phosphate production technology in the world at present, and has the advantages of high utilization rate of the ammonia, low production cost, high nitrogencontent of the produced product, low moisture content, high particle strength, difficult caking of the product, no floating when the product is used in water and the like.

Claims

1. A process for producing a nitrogen-phosphorus-potassium compound fertilizer comprises the following steps:

(1) adding concentrated sulfuric acid with the weight of 10-20% of the total weight of the raw materials, dilute phosphoric acid with the weight of 5-12% of the total weight of the raw materials and washing liquid from a washing system into a pre-neutralizer from the top of the pre-neutralizer, wherein the N/P correction molecular ratio of the washing liquid is less than 0.3, the specific gravity is 1.30-1.35, the using amount of the washing liquid is 3.45 times of that of the concentrated sulfuric acid, gaseous ammonia with the weight of 5-12% of the total weight of the raw materials from an ammonia evaporator enters the pre-neutralizer from the tangential direction of the bottom of the pre-neutralizer, and concentrated sulfuric acid, the dilute phosphoric acid, the washing liquid and the gaseous ammonia in the pre-neutralizer are fully mixed and react to;

(2) conveying qualified slurry obtained by the reaction of the preneutralizer to a tubular reactor by a pump, maintaining the pressure before the qualified slurry enters the tubular reactor to be 0.5Mpa, introducing gas ammonia which is 2-8% of the total weight of raw materials from an ammonia evaporator into the tubular reactor from the head of the tubular reactor, maintaining the pressure before the gas ammonia to be 0.5Mpa, introducing concentrated sulfuric acid which is 5-10% of the total weight of the raw materials into the tubular reactor, maintaining the pressure before the gas ammonia to be 0.5Mpa, preparing high-temperature slurry with the temperature of 160-220 ℃and the N/P correction molecular ratio of more than 1.8, discharging molten slurry prepared in the tubular reactor from the tail end of the tubular reactor arranged outside a cylinder body at the discharge end of a granulator, spraying and coating the molten slurry on a material returning bed layer in a rotary drum granulator, introducing potassium chloride which is 12-24% of the total weight of the raw materials into the granulator, and rolling the materials, discharging the finished product material with the water content of 2.0-3.0% from the tail of the granulator and drying the material in a dryer;

(3) the granulation tail gas, the reaction tail gas and the equipment exhaust tail gas are sent to an RGV Venturi scrubber, the dry tail gas is sent to a dryer Venturi scrubber and is respectively washed by dilute phosphoric acid, concentrated sulfuric acid and circulating washing liquid, and then the dry tail gas is sent to a horizontal scrubber through respective draught fans to remove ammonia and fluorine and then is discharged into the atmosphere through a chimney, wherein the dosage of the dilute phosphoric acid and the concentrated sulfuric acid entering the Venturi scrubber is respectively 30-40% and 1-3% of the total weight of the raw materials;

(4) and drying, screening and cooling the granulated material to obtain the nitrogen-phosphorus-potassium compound fertilizer.