CN1306952A

CN1306952A - Process for producing compound diammonium hydrogen phosphate fertilizer

Info

Publication number: CN1306952A
Application number: CN 00101341
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: 2001-08-08
Anticipated expiration: 2020-02-01
Also published as: CN1118445C

Abstract

By combining the normal pressure pre-neutralization reaction and pressuirzed reaction in tubular reactor, the present invention lowers the escape rate of ammonia during pelletizing process of diammonium phosphate fertilizer production, and lowers production cost greatly. The product has the advantages of high nitrogen content, low water content, high grain strength, etc.

Description

Process for producing diammonium phosphate compound fertilizer

The invention relates to a fertilizer, in particular to a process for producing a diammonium phosphate compound fertilizer by taking phosphoric acid as a basic raw material.

At present, the production process of diammonium phosphate compound fertilizer based on phosphoric acid at home and abroad mainly includes ⑴ preneutralization-drum ammonization granulation process, in which the neutralization process of phosphoric acid and ammonia is implemented by two steps, one step is implemented in preneutralization tank, and one step is implemented in granulating machine, and the heat released by ammonia neutralization is used for evaporating lots of water₃And H₃PO₄⑵ tubular reactor process, which is a new process developed in the last two decades, adopts a high-efficiency tubular reactor to replace a groove type preneutralizer for ammonia neutralization reaction, still needs gas-solid phase secondary ammonification granulation reaction in the granulator, so that the problems of high escape rate of secondary ammonification ammonia and low equipment operation rate are still not solved, the problem of secondary ammonification in a rotary drum granulator is solved by the ESPINDESA single-tube reactor process of the Spanish TR company, the internal parts in the granulator are greatly reduced, but the escape rate of ammonia is higher, and exceeds the escape rate of ammonia in the preneutralization rotary drum granulation process and the tubular reactor process.

Therefore, the invention aims to provide a process for producing the diammonium phosphate compound fertilizer, which can reduce the escape rate of ammonia and ensure high equipment operation rate, aiming at the defects of the process.

The object of the present invention can be achieved by the following scheme, and the raw material required by the present invention is 50% PO₂O₅The production process of the concentrated phosphoric acid, the liquid ammonia and the 98 percent concentratedsulfuric acid comprises the following steps:

1. adding concentrated phosphoric acid accounting for 26-43% of the total weight of the raw materials and washing liquid from a washing system into a preneutralizer from the top of the preneutralizer, wherein the amount of the washing liquid is 4 times of that of the concentrated phosphoric acid (the N/P corrected molecular ratio of the washing liquid (0.3 specific gravity is 1.35-1.45), and gaseous ammonia accounting for 15-50% of the total weight of the raw materials from an ammonia evaporator enters the preneutralizer from the bottom tangential direction of the preneutralizer, in the preneutralizer, the concentrated phosphoric acid, the washing liquid and the gas ammonia are fully mixed and react to prepare qualified slurry (the corrected molecular ratio of the slurry is 0.6-0.8 or 1.2-1.4, and the specific gravity is 1.50-1.56), the slurry has good fluidity and less corrosivity, the reaction tail gas is washed in a Venturi scrubber, which has the following main chemical reaction formula:

(1)、

(2)、 .

2. the accept slurry obtained in the preneutralizer reaction was pumped into a tubular reactor and the pressure before entering the tubular reactor was maintained at 5kgf/cm²About, gas ammonia from an ammonia evaporator accounting for 13-40% of the total weight of the raw materials enters the tubular reactor from the head part of the tubular reactor and the pressure is maintained to be 5kgf/cm before²About 1-10 wt% of concentrated sulfuric acid based on the total weight of the raw materials is fed from the head of the tubular reactor and maintained at a pressure of 5kgf/cm²About, the gas ammonia and the slurry are rapidly and fully mixed in the tubular reactor and react with the free phosphoric acid in the slurry to prepare the high-temperature slurry with the temperature of 130-170 ℃ and the N/P correction molecular ratio of more than 1.8, the molten slurry prepared in the tubular reactor is discharged from the tail end of the tubular reactor arranged outside a cylinder body at the discharge end of a granulator and sprayed and coated on a return bed layer in a rotary drum granulator, the main component of the return is dust collected by a system, crushed materials and part of finished product particles are screened, the materials roll in the granulator to form particles, the finished product materials containing 2.0-3.0% of water are discharged from the tail part of the granulator and fall into a dryer for drying, the molten slurry quickly discharged from the tubular reactor is discharged in the moment of being sprayed on the granulation return bed layer, most of the water in the slurry is flashed in the granulator with micro negative pressure and is pumped out by a tail gas fan to a washing system for washing, and the main chemical reaction formula is as follows:

(1)、

(2)、

(3)、

3. the granulation tail gas, the reaction tail gas and the equipment exhaust tail gas are sent to an RGV Venturi scrubber, the drying tail gas is sent to a dryer Venturi scrubber, and is respectively washed by circulating washing liquid, and then is sent to a horizontal scrubber through respective draught fans to remove ammonia and fluorine and is exhausted into the atmosphere through a chimney.

4. Drying, screening and cooling the granulated material to obtain the diammonium phosphate compound fertilizer.

The embodiment takes the daily production of 960 tons of diammonium phosphate compound fertilizer as an example: the amount of the ammonia gas to be removed from the preneutralizer is 5.35 tons/hour, the amount of the ammonia gas to be fed into the tubular reactor is 3.57 tons/hour, the amount of the concentrated phosphoric acid to be removed from the preneutralizer is 5.57 tons/hour, and the amount of the concentrated sulfuric acid to be fed into the tubular reactor is 1.1 tons/hour.

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 nitrogen content 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 diammonium phosphate compound fertilizer by taking phosphoric acid as a basic raw material comprises the following steps:

(1) adding concentrated phosphoric acid with the weight of 26-43% 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 corrected molecular ratio of the washing liquid is less than 0.3, the specific gravity is 1.35-1.45, the using amount of the washing liquid is 4 times that of the concentrated phosphoric acid, gaseous ammonia with the weight of 15-50% 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 the concentrated phosphoric acid, the washing liquid and the gaseous ammonia are fully mixed and react in the pre-neutralizer to prepare slurry;

(2) will react in a preneutralizer to produceThe resulting slurry was pumped into a tubular reactor while maintaining the pressure before entering the tubular reactor at 5kgf/cm²About, gas ammonia from an ammonia evaporator in an amount of 13 to 40% by weight based on the total weight of the raw materials is introduced into the tubular reactor from the head part thereof while maintaining the pressure at 5kgf/cm²About 1-10 wt% of concentrated sulfuric acid based on the total weight of the raw materials is fed from the head of the tubular reactor and maintained at a pressure of 5kgf/cm²Left and right, gas ammonia and slurry are mixed rapidly and fully in the tubular reactor and react with free phosphoric acid in the slurry to prepare high-temperature slurry with the temperature of 130-; at the moment that the molten slurry quickly discharged from the tubular reactor is sprayed on a granulation returning bed layer, most of moisture in the slurry is flashed in a micro-negative pressure granulator and pumped out by a tail gas fan to be sent to a washing system for washing;

(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 circulating washing liquid, and then the dry tail gas is sent to a horizontal scrubber through respective induced draft fans to remove ammonia and fluorine and is exhausted into the atmosphere through a chimney;

(4) and drying, screening and cooling the granulated material to obtain the diammonium phosphate compound fertilizer.