SU711019A1 - Method of preparing complex nitrogen-phosphorus fertilizer - Google Patents

Description

one

The invention relates to methods for the processing of phosphate raw materials by its nitric-sulfuric acid decomposition and can be used in industry for the preparation of complex mineral fertilizers.

Methods are known for producing complex fertilizers by nitric acid decomposition of natural phosphate, followed by treatment of the reaction mixture with sulfuric acid, separation of calcium sulfate by filtration, and processing the resulting filtrate into the final product. In order to save sulfuric acid, part of it can be replaced with ammonium sulfate (1.

The closest to the present invention is a method for the preparation of complex fertilizers, including the decomposition of natural phosphate with sulfuric acid at 60-90 ° C so that part of the calcium; present in natural phosphate; converted to calcium sulphate. The resulting pulp reacts with nitric acid, and the PzOs contained in the phosphate are converted to phosphoric acid. Further, by adding ammonium sulfate, the calcium nitrate present in the solution is converted

. calcium sulphate. The phosphogypsum is separated and the production solution is ammoniated to produce ammonium phosphate 2.

The disadvantage of this method is significant. the duration of the process is 7 hours. In addition to this, the crystallization of calcium sulfate protec- tion is not in optimal conditions, which causes a deterioration in filterability and washing of phosphogypsum. The degree of washing in PjOs does not exceed, and the content of nitrogen in the washed sediment reaches 2.4–5%, respectively, which reduces the degree of utilization of phosphate raw materials.

The purpose of the invention is to intensify the process and increase the degree of utilization of the cf by improving the washing of phosphogypsum.

The goal is achieved by the fact that 40-60% of phosphate raw materials are treated with sulfuric acid, taken in stoichiometric amount to bind all the calcium contained in the total mass of phosphate raw materials fed to the process at 95-130 ° C, and the rest of the phosphate raw materials are treated with nitrogen acid in the presence of circulating filtrate at 50-70 ° C, followed by mixing both streams at 60-90 C, for 30-120 mt. It is more expedient to conduct acid decomposition within 15-30 minutes. At cMoiJjeHHM streams, the SOJ ions and calcium ions interact with the sulfuric acid and nitric acid stages of the process to form well-filtered calcium sulfate hemihydrate crystals. A part of the anhydrite that came from the sulfuric acid stage is recrystallized in the semihydrate. Under these conditions, the total duration of the process does not exceed 180 minutes, the filtration rate is 600-800 kg / h of dry, washed sludge from 1 and 2 of the filtering surface, and the degree of washing reaches 96-98%. Example 1. The entire flow of apatite concentrate (100 parts by weight) entering the process is divided into two parts. One of the lm, in the amount of 40% of the total flow is treated in the reactor, 149.8 parts by weight. 60% sulfuric acid at 95 ° C. The useful volume of the reactor is 0.25 m per ton of raw material, which ensures a residence time of pulp in the reactor for 15 minutes. During this time, the degree of decomposition of apatite reaches 96% and 20% of fluorine is released into the gas phase from the amount introduced with apatite to this stage. The second part of the apatite concentrate, in the amount of 60% of the total flow, is treated with 212.7 parts by weight. 55% nitric acid and 300 weight.h. working solution containing 20% and 35% HNOj. The duration of the nitric acid decomposition is 30 minutes and the temperature is 50 ° C, while the entire apatite concentrate introduced into this stage is almost completely decomposed. The pulp after the first and second are mixed in the reactor-crystallizer at 60 ° C for 30 minutes. Under these conditions, 75% of the total anhydrite formed during the acid decomposition of apatite is recrystallized into the hemihydrate, i.e. The composition of phosphogypsum includes 90% hemihydrate of Krc sulfate and 10% ashhydrite. This composition of phosphogypsum, as well as the micro-granulometric characteristics of the crystals, provides filtration performance of 950 kg of dry washed sediment per hour, to the extent of washing according to PjOs of 98.5%. A part of the first filtrate, in an amount corresponding to the productivity of the raw materials, is sent for ammonization and further processing to the finished product. The total process time is 75 min. The degree of use of the raw material, which is a derivative of the degree of phosphochoptic production from P2O5 and decomposition coefficient 1, is 96.2%. 94 Example 2. From 100 weight.h. apatite concentrate entering the process, 55 ipec.K. It is fed to 1 reactor with a capacity of 0.27 m 1 ton of raw material, where 149.8 wt.t. 60% sulfuric acid. The total residence time of the pulp in the reactor is 20 minutes, the decomposition temperature is maintained at 125 ° C. After the end of the sulfuric acid decomposition, the pulp flows into the mixer-crystallizer. At the same time 45 weight.h. Apatite concentrate process 212.7 weight.h. 557-oh nitric acid and 300 weight.h. a working mixture of nitric and phosphoric acids containing 19.2 P2O5 and 33% HNO3. Processing of apatite with a mixture of nitric and phosphoric acids is carried out at 60 ° C for 20 minutes, after which the pulp also flows into the mixer-crystallizer. Calcium sulfate hemihydrate crystallizes in the mixer-crystallizer at 75 ° C for 60 minutes and 55% of the anhydrite recrystallized from the sulfuric acid stage. Thus, the phosphorescent consists of 25% of anhydrite and 75% of calcium sulfate hemihydrate. At the sulfuric acid stage, 1.45 parts by weight are released into the gas phase. fluorine, i.e. 85% of that entered at this stage, or 46.8% of the total amount of fluorine introduced into the process with apatite. After the mixer-crystallizer, the pulp is filtered on a self-leveling vacuum filter with a capacity of 75 kg / m per hour of dry washed sludge and washed three times counter-current, so that the degree of washing is 97.5%. The second filtrate, containing 14.5% and 27% HNO3, and the first filtrate, containing 19.2% and 33.1% HNOj, are wrapped for decomposition of apatite into the nitric acid stage, and part of the first filtrate is transferred in an amount corresponding to the performance of apatite. for ammoniation and processing in the finished product by known methods. The total process time is 100 minutes. The degree of use of raw materials is 95.6%. Example 3. Of the total of 100 weight.h. apatite concentrate, which is drained into the process, 60% is fed to the first reactor, where it is treated for 30 minutes - weight.h. sulfuric acid containing 60% H2SO4. The decomposition temperature is maintained at 180 ° C. At the same time, 95% of apatite is decomposed and 85% (1.6 parts by weight) of fluorine is released into the gas phase from the introduced into this stage. The second part of apatite in the amount of 40% of the total mass of the raw material is processed 212.7 parts by weight. 55% nitric acid and 300 weight.h. a working mixture of acids containing 18% Р2О5 and 30% НЫСз- Nitric acid decomposition during 5 minutes at 70 ° С, which ensures the decomposition of the raw material by 99.2%. In the reactor-crystallizer for 120 minutes, the slurry flows are mixed with the sulfuric acid and nitric acid process stages. The temperature in the crystallizer is maintained at 90 ° C, while 30% of the anhydride coming from the sulfuric acid stage recrystallizes. After the crystallizer, the pulp is filtered on a vacuum filter and the precipitate is washed with hot water. Phosphogypsum contains 60% calcium sulfate hemihydrate and 40% anhydrite. The filtration rate is 600 kg / hr of dry, washed sludge, and the degree of phosphogypsum washing from PjOs is 95%. The total process time is 170 and the utilization rate of the raw material is 93.1%. Formula of the invention 1. A method for producing a complex nitrogen-phosphate fertilizer, including decomposition of a phosphate raw material with sulfuric acid and nitric acid, followed by filtration of the phosphogypsum formed, characterized in that, in order to intensify the process and increase the utilization rate of the raw material due to improved washing of phosphogypsum - 60% of the phosphate raw material is treated with sulfuric acid, taken in stoichiometric amount for binding all the calcium contained in the total mass of the phosphate raw material supplied to the process, at 95-130 ° C, and Flax amount of the phosphate raw material is treated with nitric acid in the presence of circulating the filtrate at 50-70 ° C, followed by mixing both streams at 60-90 ° C for 30-120 min. 2. The method according to claim 1, about tl and h and y and i, with it, that the acid decomposition of phosphate raw materials is carried out within 15-30 minutes Sources of information taken into account during the examination 1. USSR author's certificate No. 491600, cl. C 05 V 1/06, 15.11.75. 2. The patent of Great Britain No. 1187952, cl. C 05 V 11/00, 04/15/1950 (prototype).

Claims (2)

Claim 1. A method of producing a complex nitrogen-phosphorus fertilizer, including the decomposition of phosphate raw materials with sulfuric and nitric acids, followed by filtration of the formed phosphogypsum, characterized in that, in order to intensify the process and increase the ₅ degree of utilization of raw materials by improving the washing of phosphogypsum, 40-60% phosphate raw materials are treated with sulfuric acid, taken in stoichiometric amount on a bond; all calcium contained in the total ₁₀ mass of phosphate feed to the process is charged at 95–13 ° C, and the remaining amount of phosphate feed is treated with nitric acid in the presence of a reverse filtrate at 5– 7 ° C, followed by mixing of both streams at 60– 90 ° C for 30-120 minutes 2. The method according to p.