CN108117190B

CN108117190B - Process for treating low-concentration ammonia nitrogen wastewater of phosphate fertilizer plant

Info

Publication number: CN108117190B
Application number: CN201711334640.6A
Authority: CN
Inventors: 郭举; 杨毅; 刘松林; 刘美霞
Original assignee: Wengfu Group Co Ltd
Current assignee: Wengfu Group Co Ltd
Priority date: 2017-12-14
Filing date: 2017-12-14
Publication date: 2021-04-02
Anticipated expiration: 2037-12-14
Also published as: CN108117190A

Abstract

The invention discloses a process for treating low-concentration ammonia nitrogen wastewater of a phosphate fertilizer plant, which relates to a novel process for low-cost treatment and resource utilization of low-concentration ammonia nitrogen wastewater of traditional phosphate fertilizer and phosphorus compound fertilizer production enterprises, and the specific process flow mainly comprises the procedures of wastewater pretreatment precipitation, plate-frame filter pressing, secondary membrane concentration treatment, synthesis reaction, secondary plate-frame filter pressing and post-treatment, wherein the low-concentration ammonia nitrogen content in the wastewater is concentrated by utilizing a combined technology taking membrane treatment as a main part, so that the treatment cost is greatly reduced; the resources such as ammonia nitrogen, phosphorus and the like in the wastewater and the added magnesium resource are utilized to produce the magnesium ammonium phosphate fertilizer, so that the resource utilization value of the wastewater is improved, and the economic benefit is created; waste residues in the treatment process are used as base materials to enter a phosphate fertilizer production system, treated fresh water is recycled, and no new three wastes are generated in the whole treatment process, so that the environmental protection problem caused by waste water discharge is thoroughly solved. The invention can effectively solve the problem of treatment of ammonia nitrogen wastewater of phosphate fertilizer and phosphorus compound fertilizer production enterprises.

Description

Process for treating low-concentration ammonia nitrogen wastewater of phosphate fertilizer plant

Technical Field

The invention relates to a process for treating low-concentration ammonia nitrogen wastewater of a phosphate fertilizer plant, belonging to the field of phosphorus chemical industry.

Technical Field

The products of the traditional phosphorus fertilizer and phosphorus compound fertilizer production enterprises mainly comprise products such as ammonium phosphate, phosphorus compound fertilizer and phosphate, a large amount of low-concentration ammonia nitrogen wastewater can be generated in the production process, the resource concentration (such as nitrogen and phosphorus) in the wastewater is low and cannot meet the requirements of the valuable utilization degree and the discharge standard, if the wastewater is discharged, the wastewater is treated to reach the standard by spending expensive treatment cost, and if the wastewater is directly discharged, the environmental protection problem is generated, so the low-concentration ammonia nitrogen wastewater becomes a difficult problem for the phosphorus fertilizer and phosphorus compound fertilizer production enterprises.

At present, phosphorus and phosphorus compound fertilizer production enterprises mainly adopt two methods for treating the wastewater, wherein the method is used for recycling in a production system, such as dry tail gas washing water, condensed water and the like, but the long-period recycling enables impurity ions in the wastewater to be enriched to a certain extent, so that the using effect of the wastewater is influenced, the product quality is further influenced, and part of the wastewater is discharged to a sewage treatment system for treatment after the long-period recycling; and secondly, directly discharging the waste water to a sewage treatment system for treatment, wherein lime is mostly adopted for neutralization, and the waste water is further subjected to advanced treatment and discharged after reaching the standard. In view of the two typical treatment methods of the current wastewater, the wastewater is expensive to treat, and the resources in the wastewater are not utilized effectively.

Disclosure of Invention

The invention aims to solve the problems and provides a process for treating low-concentration ammonia nitrogen wastewater in a phosphate fertilizer plant, which solves the problems of environmental protection and benefit from two aspects of treatment cost and valuable recovery.

The method takes low-concentration ammonia nitrogen wastewater of a phosphate fertilizer plant as a raw material, and produces the magnesium ammonium phosphate fertilizer through the working procedures of pretreatment precipitation, plate-frame filter pressing, secondary membrane treatment concentration, synthesis reaction, secondary plate-frame filter pressing and post-treatment, thereby achieving the purposes of treating the low-concentration ammonia nitrogen wastewater at low cost and solving the environmental protection problem.

The specific process parameters are as follows: pretreatment and precipitation: mainly means that a certain amount of flocculant is added for precipitation under certain conditions, polyacrylamide solution with the concentration of 0.1 percent of the flocculant is added, the content of polyacrylamide in the added solution is 0.01 percent to 0.05 percent, and the precipitation time is 12 hours; plate and frame filter pressing: filtering the solution after precipitation, enabling filter residues to enter a phosphate fertilizer production system, and enabling filtrate to enter the next working procedure for use; third, second-level membrane treatment and concentration: the filtrate is subjected to two-stage reverse osmosis membrane step-by-step concentration, the ammonia nitrogen concentration is finally increased to 4% -6%, the treatment temperature is 20-50 ℃, the treatment pressure is less than or equal to 8MPa, the obtained fresh water is recycled in a production system, and the obtained concentrated water enters the next step; fourthly, synthetic reaction: reacting concentrated water with added magnesium chloride under certain conditions to produce magnesium ammonium phosphate, controlling the reaction temperature to be 40-60 ℃, the reaction time to be 2-6h, the reaction pH to be 8-10, and the mixture ratio of phosphorus, nitrogen and magnesium in the reaction liquid to be 1.05:1:1.1, entering the next working procedure after the reaction is finished; secondary plate-frame filter pressing, namely filter pressing the reaction solution in the previous process, returning the filtrate to the secondary membrane treatment concentration process for recycling, and feeding the filter residue to the next process; sixthly, post-treatment: and drying and crushing the filter residue obtained in the previous procedure to obtain the product magnesium ammonium phosphate fertilizer.

In the process, the wastewater comes from phosphate fertilizer, phosphorus compound fertilizer and phosphate fertilizer production enterprises taking ammonia and ammonium salt as raw materials, the pH value of the wastewater is 2-6, the temperature is not more than 80 ℃, the solid content is 0.1% -3%, and the wastewater mainly comprises the following components: the ammonia nitrogen content is 100 ppm-20000 ppm; 10ppm to 200ppm of total phosphorus; fluorine 10ppm to 100 ppm.

The invention has the beneficial effects that: the process is used for producing the magnesium ammonium phosphate fertilizer product, the used raw material is low-concentration ammonia nitrogen wastewater which is difficult to treat in a phosphate fertilizer plant, the raw material belongs to one of three wastes in the plant, the method is used for recovering resources such as low phosphorus, nitrogen and the like in the wastewater to produce the high-value magnesium ammonium phosphate fertilizer, a certain economic value is created, the treated mother liquor is recycled in the system, the obtained fresh water can be used for replenishing water for the production system, a certain amount of magnesium salt is added to precipitate the resources such as nitrogen, phosphorus and the like in the form of magnesium ammonium phosphate, and the magnesium ammonium phosphate fertilizer is finally produced, so that the nitrogen and phosphorus resources in the wastewater are recovered in a valuable manner; waste residues in the treatment process are used as base materials to enter a phosphate fertilizer production system, no new three wastes are generated in the whole treatment process, resources are utilized to the maximum extent, the problem of environmental protection is solved while economic benefits are created, and the circulating economic development of enterprises is realized.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

Example 1

Taking 1000g of washing wastewater, adding 100g of polyacrylamide solution with the concentration of 0.1%, precipitating for 12h, taking out, filtering, feeding the filtrate into a secondary membrane treatment concentration device, controlling the operation pressure to be 6MPa, the temperature to be 50 ℃, the water yield to be 60% and other indexes to ensure that the ammonia nitrogen concentration in the concentrated water reaches about 6%, adding a certain amount of magnesium salt to ensure that the mass ratio of phosphorus, nitrogen and magnesium in the solution is 1.05:1:1.1, controlling the reaction temperature to be 50 ℃, reacting for 4h, reacting at pH9.0, filtering after the reaction is finished, and drying the filter cake for 6h at 85 ℃ to obtain the product of the ammonium magnesium phosphate fertilizer.

The total phosphorus content in the product was found to be 29.1%, the magnesium oxide content was 16.4%, and the nitrogen content was 5.62%. The ammonia nitrogen content in the treated fresh water is 9 ppm.

Example 2

Taking 1000g of washing wastewater, adding 100g of polyacrylamide solution with the concentration of 0.1%, precipitating for 12h, taking out, filtering, feeding the filtrate into a secondary membrane treatment concentration device, controlling the operation pressure to be 4MPa, controlling the temperature to be 40 ℃, controlling the indexes such as the water yield to be 80%, and the like, so that the ammonia nitrogen concentration in the concentrated water reaches about 5%, adding a certain amount of magnesium salt so that the mass ratio of phosphorus, nitrogen and magnesium in the solution is 1.05:1:1.1, controlling the reaction temperature to be 60 ℃, reacting for 2h, reacting the pH to be 10, filtering after the reaction is finished, and drying the filter cake for 6h at 85 ℃ to obtain the product magnesium ammonium phosphate fertilizer.

The total phosphorus content in the product was found to be 28.8%, the magnesium oxide content 15.9%, and the nitrogen content 5.77%. The ammonia nitrogen content in the treated fresh water is 14 ppm.

Example 3

Taking 1000g of washing wastewater, adding 100g of polyacrylamide solution with the concentration of 0.1%, precipitating for 12h, taking out, filtering, feeding the filtrate into a secondary membrane treatment concentration device, controlling the operation pressure to be 8MPa, controlling the temperature to be 40 ℃, controlling the water yield to be 70% and other indexes to ensure that the ammonia nitrogen concentration in the concentrated water reaches about 6%, adding a certain amount of magnesium salt to ensure that the mass ratio of phosphorus, nitrogen and magnesium in the solution is 1.05:1:1.1, controlling the reaction temperature to be 40 ℃, reacting for 6h, reacting at pH8.1, filtering after the reaction is finished, and drying the filter cake for 6h at 85 ℃ to obtain the product of the ammonium magnesium phosphate fertilizer.

The total phosphorus content in the product was found to be 28.89%, the magnesium oxide content was 15.93%, and the nitrogen content was 5.83%. The ammonia nitrogen content in the treated fresh water is 10 ppm.

Claims

1. A process for treating low-concentration ammonia nitrogen wastewater in a phosphate fertilizer plant is characterized by mainly comprising six process steps: firstly, pretreating precipitate; pressing and filtering by a plate frame; thirdly, secondary membrane treatment and concentration; fourthly, synthetic reaction; secondary plate-frame filter pressing; sixthly, post-treatment; wherein the step of pre-treating and precipitating mainly comprises the steps of adding a certain amount of flocculant to precipitate under certain conditions, adding a polyacrylamide solution with the concentration of 0.1 percent of the flocculant, wherein the content of polyacrylamide in the added solution is 0.01 to 0.05 percent, and the settling time is 12 hours; the plate-frame filter pressing step is to filter the solution after precipitation, filter residues enter a phosphate fertilizer production system, and filtrate enters the next process for use; the second-stage membrane treatment concentration step is to carry out the step-by-step concentration on the filtrate through a two-stage reverse osmosis membrane, finally, the ammonia nitrogen concentration is increased to 4% -6%, the treatment temperature is 20 ℃ -50 ℃, the treatment pressure is less than or equal to 8MPa, the obtained fresh water is recycled in a production system, and the obtained concentrated water enters the next working procedure; the synthetic reaction process is to react concentrated water with added magnesium chloride under certain conditions to produce magnesium ammonium phosphate, wherein the reaction temperature is controlled to be 40-60 ℃, the reaction time is 2-6h, the reaction pH is controlled to be 8-10, and the mass ratio of phosphorus, nitrogen and magnesium in the reaction liquid is 1.05:1:1.1, entering the next working procedure after the reaction is finished; the secondary plate-and-frame filter pressing step is to filter press the reaction liquid in the previous process, the filtrate returns to the secondary membrane treatment concentration process for recycling, and the filter residue enters the next process; the post-treatment process is to dry and crush the filter residue obtained in the previous process to obtain the product magnesium ammonium phosphate fertilizer; the wastewater comes from phosphate fertilizer production enterprises, the pH value of the wastewater is 2-6, the temperature is not more than 80 ℃, the solid content is 0.1% -3%, and the wastewater mainly comprises the following components: the ammonia nitrogen content is 100 ppm; 10ppm to 200ppm of total phosphorus; fluorine 10ppm to 100 ppm.