CN-121990856-A - Method for preparing slow-release nitro fertilizer while recycling fluorine in white fertilizer

CN121990856ACN 121990856 ACN121990856 ACN 121990856ACN-121990856-A

Abstract

The invention discloses a method for preparing a slow-release nitro fertilizer while recycling fluorine in a white fertilizer, and belongs to the technical field of phosphorus resource clean processing and utilization. The invention uses nitric acid to carry out graded acidolysis on the white fertilizer, and the phosphorus-containing filtrate after preliminary acidolysis has low impurity content and can be used for preparing water-soluble ammonium phosphate. And (3) carrying out complete acidolysis on the residual acidolysis slag, completely leaching phosphorus and fluorine elements, then carrying out defluorination, precipitating fluorine in a fluorosilicate form, and further separating to obtain a fluorosilicate product. The defluorination liquid is neutralized and then dried to obtain a slow-release nitro fertilizer product, and the method comprehensively utilizes phosphorus and fluorine resources in the white fertilizer to realize the clean processing and utilization of the phosphorus resources. The method has the advantages of simple whole process implementation method and low production cost, and fully utilizes the phosphorus and fluorine resources in the white fertilizer.

Inventors

XU DEHUA
YANG LIN
WAN QINGHUA
YANG JINGXU
WANG XINLONG
CHEN KUN
YANG WENGONG
YANG YANG
ZHANG ZHIYE
YANG XIUSHAN

Assignees

四川大学

Dates

Publication Date: 20260508
Application Date: 20260408

Claims (7)

1. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer is characterized by comprising the following steps of: (1) Preparing slurry, namely mixing water and white fertilizer according to a liquid-solid ratio of 1.5-3.5 to obtain slurry; (2) The first step of acidolysis, namely heating the slurry to 30-70 ℃, then adding nitric acid until the pH value of the system is 1.0-3.0, and then carrying out heat preservation reaction for 0.5-2 hours; (3) Adding nitric acid and water into the residual acidolysis slag to enable the mass fraction of the nitric acid in the obtained system to be 18% -25%, then carrying out heat preservation reaction for 0.5-2 h at 30-70 ℃, and then filtering; (4) Defluorination, namely adding a defluorinating agent into the filtrate obtained in the step (3), and then carrying out heat preservation reaction for 50-70 min at 20-60 ℃ and then filtering to obtain fluorosilicate and defluorinated filtrate, wherein the defluorinating agent is potassium nitrate; (5) And (3) neutralizing, namely introducing ammonia into the defluorinated filtrate, reacting for 0.5-1 h at 60-70 ℃, and drying to obtain the slow-release nitro fertilizer.
2. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer according to claim 1, wherein the mass fraction of nitric acid in the step (2) is 65-70%, the pH of a system is 2.5 by adding nitric acid, the reaction temperature of acidolysis in the first step is 50 ℃, and the acidolysis time is 0.5h.
3. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer according to claim 1, wherein the mass fraction of nitric acid in the step (3) is 65-70%, the reaction temperature of acidolysis in the second step is 40-50 ℃, and the acidolysis time is 1h.
4. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer according to claim 1, wherein the adding amount of the potassium nitrate is based on the mole ratio of F to K in the system of 3.
5. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer according to claim 4, wherein diatomite is added simultaneously with the potassium nitrate, the adding amount of the diatomite is based on the molar ratio of F to Si in the system being 6, and the fluorosilicate is potassium fluosilicate.
6. The method for recovering fluorine from a white fertilizer and simultaneously preparing a slow-release nitro fertilizer according to claim 5, wherein the defluorination reaction temperature in the step (4) is 40 ℃ and the defluorination time is 60min.
7. The method for preparing the slow-release nitro fertilizer while recycling fluorine in the white fertilizer according to claim 1, wherein ammonia is introduced to the system in the step (5) until the pH value is 4-5, the neutralization reaction temperature is 65 ℃, and the reaction time is 1h.

Description

Method for preparing slow-release nitro fertilizer while recycling fluorine in white fertilizer Technical Field The invention belongs to the technical field of phosphorus resource cleaning and processing and utilization, and particularly relates to a method for preparing a slow-release nitro fertilizer while recycling fluorine in a white fertilizer. Background In the process of producing industrial monoammonium phosphate by wet phosphoric acid, impurity ions in slurry after ammonia is introduced to neutralize reaction generate a large amount of insoluble complex compound-white fertilizer, and the yield of the complex compound-white fertilizer is 0.5-1.0 times of that of the industrial monoammonium phosphate product. The content of phosphorus in the white fertilizer is very high, wherein the content of P 2O5 is about 30% -40%, and most of the phosphorus exists in a form of citrate soluble effective phosphorus, and meanwhile, the white fertilizer enriches most of fluorine, iron, calcium, aluminum, magnesium and other ions in wet-process phosphoric acid, so that the comprehensive recycling of the industrial ammonium white fertilizer is still a difficult problem for enterprises. The prior researches report technical routes for treating the white fertilizer, and the utilization way is mainly pulping and mixing into other devices for producing compound fertilizers or directly producing slow-release phosphate fertilizers, and fluorine in the white fertilizer is not recycled although the existence of the white fertilizer is reduced to a certain extent. In the prior art, white fertilizer is directly added into a fertilizer production device to produce magnesium ammonium sulfate and ammonium sulfate based phosphate products by utilizing elements such as available phosphorus, sulfur and the like, but the method sometimes needs to be modified on equipment, has high production cost, and does not fully utilize the elements in the white fertilizer. In the second prior art, white fertilizer and mother liquor are mixed to prepare slurry, nitrogen source and potassium source are added, and spray drying and granulation are carried out to obtain the nitrophosphate fertilizer, but the quality of the obtained product is unstable. In the prior art, the three treatment processes of water washing, acidolysis, defluorination, extraction, back extraction, neutralization and the like are designed to obtain ammonium phosphate, sodium fluosilicate and magnesium ammonium sulfate to realize the recovery of phosphorus, fluorine, nitrogen and magnesium, but the process flow is longer, the recovery effect of the extractant is poorer, and industrialization is difficult to realize. In the prior art, citric acid solution is added into the white fertilizer to be chelated to obtain the liquid fertilizer, but the method does not fully utilize fluorine resources in the white fertilizer. Disclosure of Invention Aiming at the prior art, the invention provides a method for preparing the slow-release nitro-fertilizer while recycling fluorine in the white fertilizer, which is used for preparing the slow-release nitro-fertilizer by classifying acidolysis, defluorination and neutralization of the white fertilizer, so that the high-value utilization of the phosphorus in the white fertilizer can be realized, and the fluorine resource in the white fertilizer can be effectively recycled. In order to achieve the above purpose, the technical scheme adopted by the invention is that the method for preparing the slow-release nitro fertilizer while recovering fluorine in the white fertilizer comprises the following steps: (1) Preparing slurry, namely mixing water and white fertilizer according to a liquid-solid ratio of 1.5-3.5 to obtain slurry; (2) The first step of acidolysis, namely heating the slurry to 30-70 ℃, then adding nitric acid until the pH value of the system is 1.0-3.0, and then carrying out heat preservation reaction for 0.5-2 hours; (3) Adding nitric acid and water into the residual acidolysis slag to enable the mass fraction of the nitric acid in the obtained system to be 18% -25%, then carrying out heat preservation reaction for 0.5-2 h at 30-70 ℃, and then filtering; (4) Defluorination, namely adding a defluorinating agent (the defluorinating agent is potassium nitrate, and alkali metal salts such as sodium nitrate, potassium carbonate or sodium carbonate can be adopted in addition) into the filtrate obtained in the step (3), then carrying out heat preservation reaction for 50-70 min at 20-60 ℃, and then filtering to obtain fluorosilicate and defluorinated filtrate; (5) And (3) neutralizing, namely introducing ammonia into the defluorinated filtrate, reacting for 0.5-1 h at 60-70 ℃, and drying to obtain the slow-release nitro fertilizer. The method uses nitric acid to carry out graded acidolysis on the white fertilizer, the content of impurities in the phosphorus-containing filtrate after preliminary acidolysis is low, and the filtrate can be sen