CN1706745A

CN1706745A - Ammonium carbonate process of producing monoammonium phosphate

Info

Publication number: CN1706745A
Application number: CN 200510018528
Authority: CN
Inventors: 陈思敏; 陈所安
Original assignee: CHEN SUO'AN; CHEN SUO AN
Current assignee: CHEN SUO'AN; CHEN SUO AN
Priority date: 2005-04-08
Filing date: 2005-04-08
Publication date: 2005-12-14

Abstract

The ammonium carbonate process of producing monoammonium phosphate includes continuously throwing crushed ammonium carbonate and phosphoric acid into reactor with heating pipe and special structure for continuous neutralizing reaction to produce ammonium phosphate slurry; overflowing slurry to buffering tank for regulating the neutralizing level; evaporation concentrating and spray drying to obtain monoammonium phosphate product; and absorbing CO2 containing tail gas with strong alkali solution to purify before exhaust. The present invention features the replacement of liquid ammonia with ammonium carbonate, continuous and closed neutralizing reaction, CO2 recovery and utilization and tail gas purification, and has the advantages of high efficiency, low power consumption, low cost, and environment friendship.

Description

Process for producing monoammonium phosphate by ammonium bicarbonate method

Technical Field

The invention relates to a new process for producing monoammonium phosphate by using ammonium bicarbonate (hereinafter referred to as ammonium bicarbonate) to replace liquid ammonia, namely a new process for producing monoammonium phosphate by an ammonium bicarbonate method.

Background

The traditional slurry method for producing monoammonium phosphate (hereinafter referred to as ammonium phosphate) is to gasify liquid ammonia and then carry out neutralization reaction with phosphoric acid to obtain ammonium phosphate slurry, and the ammonium phosphate slurry is evaporated, concentrated and granulated to obtain the ammonium phosphate fertilizer. The disadvantages of this method are: large investment, shortage of liquid ammonia supply as raw material, inconvenient transportation, storage and use, insecurity, toxicity and pertinence of pollution. The process of producing ammonium phosphate by using ammonium bicarbonate to replace liquid ammonia to perform neutralization reaction with phosphoric acid is called ammonium bicarbonate method ammonium phosphate production process. Its recognized advantages are: the investment is low, the raw materials are cheap and easy to purchase, the transportation and the storage are convenient, the safety is realized, and the toxicity and the pollution are low. This is fully described in chinese patent application publication No. CN 1094964a "process for producing monoammonium phosphate from ammonium bicarbonate" and chinese patent grant publication No. CN 1048227C "a method for producing ammonium phosphate from ammonium bicarbonate instead of liquid ammonia". Both of the above patents are ammonium bicarbonate process, but both of the above patents also have technical drawbacks. The main drawback of the former patent CN 1094964a has been pointed out by the latter patent CN 1048227C, i.e. preheating phosphoric acid increases the cost and is not safe to handle; the degree of neutralization is low. Compared with the former patent CN 109499964A, the latter patent CN 1048227C has a great improvement, but the latter patent itself has a great defect, mainly:

1. in the detailed description of the attached drawings of the specification, the ammonium bicarbonate solid is crushed and then is sent into a reaction tank 3 through a conveyor belt 1, and the feeding is carried out by the conveyor belt, so that the neutralization reaction tank cannot be sealed; and because the discharge port is arranged at the lower part of the reaction tank (see the attached drawing in detail), the neutralization reaction, the feeding and the discharging of the neutralization reaction are necessarily in an intermittent mode, and the continuous production cannot be realized. Therefore, the neutralization reaction tank has low use efficiency and production strength. The CO generated in the neutralization reaction tank which is not closed and can not be continuously produced₂When harmful gases are necessary to escape to the outside of the neutralization reaction tank in large quantity, the operation space and the surrounding environment are seriously polluted, and CO cannot be discharged₂And the harmful gases are fully concentrated for recycling and purification, which obviously does not meet the requirement of environmental protection. Next, the specificationAlthough "carbon dioxide gas generated by the reaction is discharged and recovered through the recovery system 4" is described in the above, there is no specific technical measure for recycling and purification, and there is no feasibility and operability.

2. The open and unclosed neutralization reaction tank, the intermittent heating neutralization reaction and the intermittent feeding and discharging operations consume more energy (steam and electric power), which is not in accordance with the energy-saving principle.

3. Because the neutralization reaction is carried out in a batch mode and can not be carried out continuously, the control range of the neutralization degree is narrow (1.15-1.2), and the production control time and the production cost are increased.

Disclosure of Invention

The invention aims to replace the open and intermittent neutralization reaction old process by a closed and continuous neutralization reaction new process so as to improve the production efficiency and strength of equipment and save energy; the strong absorption of strong alkali liquor to acid gas or other modes are used to realize the purpose of sealing concentrated harmful byproduct CO₂The full recycling and the tail gas purification of the process are realized.

The technical scheme for realizing the purpose of the invention is as follows: compared with the existing ammonium bicarbonate method for producing ammonium phosphate, the new process for producing ammonium phosphate by completely replacing liquid ammonia with ammonium bicarbonate is characterized in that: mixing crushed ammonium bicarbonate (containing N more than or equal to 17%) with medium-low concentration phosphoric acid (containing R)₂O₅About 22 percent) is continuously added into a closed reaction tank with a heating pipe and a special structure for continuous endothermic neutralization reaction, and the chemical reaction formula is as follows:

(Heat)

Ammonium phosphate slurry generated by neutralization reaction is continuously overflowed into a fine adjustment buffer tank, the neutralization degree of the slurry is adjusted to 1.16 +/-0.05 (namely, 1.11-1.21), and ammonium phosphate products (containing more than 10 percent of N and P) are obtained after continuous evaporation, concentration, powder spraying and drying (or granulation) are carried out₂O₅>46%). Containing CO₂Absorbing CO in the tail gas in the purifying tower₂The absorbent is discharged by an exhaust fan after being absorbed, utilized and purified. If strong base NaOH solution is used as absorbent, the acidic gas CO₂The chemical reaction formula used for absorption is as follows:

recovered product Na₂CO₃The solution can be used as a raw material for co-producing various sodium phosphate salts. According to different conditions, CO₂The absorbent can also be made into corresponding recovered substances by using other corresponding chemical substances, and can be used for coproducing other substancesRelated products or comprehensive utilization to reduce the total production cost. CO2₂The gas can also be frozenThe liquefied carbon dioxide is directly recovered to prepare a liquid carbon dioxide dry ice product. International 'Jingdu protocol' requires government efforts to reduce greenhouse gases and limit industrial CO₂The discharge amount of the air purifier is prevented from air pollution. The environmental protection law of China also has definite similar requirements, and the invention completely meets the requirements of preventing pollution and realizing comprehensive utilization in China and China.

The invention has the beneficial effects that: the invention not only updates and perfects the technique for producing ammonium phosphate by ammonium bicarbonate method, but also improves the production efficiency, strength, energy conservation, safety and cost reduction of equipment; and innovates or fundamentally improves harmful byproduct CO in ammonium bicarbonate method for producing ammonium phosphate₂The process technology of recycling and purifying the tail gas. Finally, on the premise of ensuring the product quality, the multiple purposes of high efficiency, energy conservation, low cost, safety and environmental protection in ammonium phosphate production by the ammonium bicarbonate method are comprehensively realized.

Drawings

The attached figure is a process flow schematic diagram of the 'new process for producing monoammonium phosphate by an ammonium bicarbonate method'.

The invention is described in detail below with reference to the accompanying drawings: after solid ammonium bicarbonate is put into a crusher 1 to be crushed, the crushed solid ammonium bicarbonate is put into a neutralization reaction tank 3 with a special structure through a screw conveyor 2, meanwhile, phosphoric acid is added into the neutralization reaction tank 3 through a feeding hole 4, and heat required by the neutralization reaction of the ammonium bicarbonate and the phosphoric acid is supplied by a heating pipe 5. CO produced by neutralization₂The gas enters an absorption purification tower 6 for recycling, and the purified tail gas is exhausted by an exhaust fan 7. CO2₂The absorption liquid enters the top of the tower from a feed inlet 8 of the tower and is sprayed downwards so as to fully contact and absorb the CO forcibly lifted from the bottom of the tower₂The gas, the solution of which is the recycled product, is discharged from a discharge port 9 at the bottom of the column for recycling. Ammonium phosphate slurry generated by neutralizing ammonium carbonate and phosphoric acid overflows from a discharge port at the upper part of the tank 3 and is discharged to a fine adjustment buffer tank 10, a small amount of ammonium carbonate or phosphoric acid required to be added for adjusting the neutralization degree of the slurry is fed from a feeding port 11, and the mixed slurry is wellneutralizedAmmonium phosphate slurry with a certain degree of neutralization is pumped into a heater 13 of an evaporation concentration system through a circulating pump 12, enters a flash evaporation chamber 14 for evaporation and dehydration after being subjected to rapid temperature rise, and the slurry is rapidly circulated among the evaporation concentration systems 12-13-14-12. The water vapour from the evaporation of the slurry is removed by a condensing system 15. After the ammonium phosphate slurry is circularly evaporated and concentrated to the required concentration, the ammonium phosphate slurry enters a powder spraying and drying (or granulating) system 16 to obtain the finished ammonium phosphate product.

Detailed Description

Referring to the attached drawings of the specification, the specific process flow is as follows:

solid ammonium bicarbonate is put into a crusher 1 to be crushed, and then is put into a neutralization reaction 3 with a special structure through a screw conveyer 2, meanwhile, phosphoric acid is added into the neutralization reaction 3 through a feed port 4, and ammonium bicarbonate and phosphoric acid are addedAnd the heat required for the reaction is supplied by the heating pipe 5. CO produced by neutralization₂The gas enters an absorption purification tower 6 for recycling, and the purified tail gas is exhausted by an exhaust fan 7. CO2₂The absorption liquid enters the top of the tower from a feed inlet 8 of the tower and is sprayed downwards so as to fully contact and absorb the CO forcibly risen from the bottom of the tower₂The gas, the solution of which is the recycled product, is discharged from a discharge port 9 at the bottom of the column for recycling. Ammonium phosphate slurry generated by neutralizing ammonium carbonate and phosphoric acid overflows from a discharge hole at the upper part of the evaporator 3 and is discharged to a fine adjustment buffer tank 10, a small amount of ammonium carbonate or phosphoric acid required to be added for adjusting the neutralization degree of the slurry is fed from a feeding hole 11, the ammonium phosphate slurry with the adjusted neutralization degree (1.16 +/-0.05) is fed into a heater 13 of an evaporation concentration system through a circulating pump 12, the temperature is rapidly raised, the ammonium phosphate slurry enters a flash evaporation chamber 14 for evaporation and dehydration, and the slurry is rapidly circulated among the evaporation concentration systems 12-13-14-12. The water vapour from the evaporation of the slurry is removed by a condensing system 15. After the ammonium phosphate slurry is circularly evaporated and concentrated to the required concentration, the ammonium phosphate slurry enters a powder spraying and drying (or granulating) system 16 to obtain the finished ammonium phosphate product.

Claims

1. A new technology for producing monoammonium phosphate by an ammonium bicarbonate method is characterized in that: ammonium bicarbonate (hereinafter referred to as ammonium bicarbonate) is crushed by a crusher (1) and then passes through a screw conveyer (2)) Continuously adding the phosphoric acid and the phosphoric acid into a closed reaction tank (3) with a heating pipe and a special structure for continuous neutralization reaction, continuously overflowing and discharging the generated ammonium phosphate slurry to a fine adjustment buffer tank (10), and adjusting the neutralization degree of the slurry to 1.16 +/-0.05 (namely: 1.11-1.21), and obtaining an ammonium phosphate product (with the content of N being more than 10 percent; containing P₂O₅>46%); the produced CO with large content by neutralization reaction₂The tail gas passes through CO in the absorption tower (6)₂After the absorbent is absorbed and purified, the absorbent is discharged through an exhaust fan (7), for example: the caustic soda solution is used as an absorbent of CO2, so that CO is absorbed and utilized₂The chemical reaction formula of (A) is:

absorption and utilization of CO₂Obtained Na₂CO₃The solution can be used as a raw material for co-producing various sodium phosphate salts; according to different conditions, CO₂The absorbent can also use other corresponding chemical substances to prepare corresponding recovered substances, and can be used for coproducing other related products or comprehensively utilizing the recovered substances so as to reduce the total production cost.

2. The new process for producing monoammonium phosphate by the ammonium bicarbonate method according to claim 1, which is characterized in that: simultaneously and continuously putting the crushed ammonium bicarbonate and the phosphoric acid into a closed reaction tank (3) with a heating pipe and a special structure for continuous neutralization reaction to prepare ammonium phosphate slurry, and continuously overflowing and discharging the slurry into a fine adjustment buffer tank (10) to adjust and control the neutralization degree.

3. The new process for producing monoammonium phosphate by the ammonium bicarbonate method according to claim 1, which is characterized in that: the neutralization degree of the ammonium phosphate slurry is 1.16 +/-0.05 (namely: 1.11-1.21).

4. The new process for producing monoammonium phosphate by the ammonium bicarbonate method according to claim 1, which is characterized in that: the neutralization reaction tank (3) continuously generates a large amount of CO in a closed state₂The gas is intensively pumped into the bottom of an absorption purification tower (6) by an exhaust fan (7), and CO is₂Is forced to rise in the tower from the top of the towerPart of sprayed CO₂The absorbent is fully contacted and absorbed, and the generated recoveryThe utilization substances are discharged from a discharge port (9) at the bottom of the tower and are used as raw materials for co-production of corresponding chemical products, such as: here, caustic soda (NaOH) solution is used as CO₂Absorbent of (2), CO₂The chemical reaction formula used for absorption is as follows:

recycling NaCO₃The solution can be used as a raw material for co-producing various sodium phosphate salts, and the purified tail gas is exhausted by an exhaust fan (7) after being recycled, so that the purposes of comprehensive utilization and environmental protection are achieved; according to different conditions, CO₂The absorbent can also adopt other corresponding chemical substances to prepare corresponding recycled materials, and can be used for co-producing other related products or comprehensively utilizing to reduce the total production cost.