SU1465436A1 - Method of producing granulated superphosphate - Google Patents

Abstract

The invention relates to the production of granular superphosphate and will increase the yield of the product fraction and simplify the process of its production by reducing the number of chemical operations. The method involves the decomposition of phosphate raw materials, in the amount of 60-90% of the initial material in the form of a suspension with a T: W 1: 1–2.3, sulfuric acid with a concentration of 75-98% in an amount of 1.6-2.5 mash. . for 1 h, phosphate, mix the resulting pulp with the remaining part of the phosphate raw material, either dry or in suspension with T: W 1: 1-2.3, simultaneous granulation and drying of the product with flue gases into the granules torus dryer with subsequent absorption of waste gases and the use of effluents. After the absorption stage to prepare suspensions of phosphate raw materials. 3 h.p., f-crystals, 1 tab. (/)

Description

 one

The invention relates to a process for the production of granular superphosphate widely used as a fertilizer in agricultural machinery.

The purpose of the invention is to increase the yield of the product fraction and simplify the process by reducing the number of manufacturing operations. .

The method of producing granulated superphosphate is carried out as follows.

At the first stage of decomposition, 60-90% of the initial phosphate raw material is fed in the form of a suspension with T: W equal to 1: 1-2.3, and all sulfuric acid is added to the remaining phosphate raw material or in the form of a suspension with T: W equal to

1: 1-2.3, either in dry form, granulation and drying are simultaneously flue gases in the dryer granulator, the exhaust gases are captured by absorption, and the absolute wastewater is used to prepare a suspension of the phosphate raw material. Feeding all sulfuric acid at a concentration of 75-98% avoids the pre-dilution stage of sulfuric acid. When concentrated acid is fed, a high temperature develops, which leads to an increase in the decomposition coefficient in the first stage. A mixture of monocalcium phosphate and free phosphoric acid is formed, which is neutralized by the remaining part of the phosphate raw material in the second stage, due to which

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ate

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an additional amount of monocalcium phosphate is formed. Neutralization takes place almost completely - only 2-5% of free acid remains, which is necessary for the normal conduct of the granulation step. No additional neutralization step is required before granulation. During granulation, optimal conditions are created due to a certain ratio in the pulp of salts and free acid, which leads to an increase in the yield of the product fraction. The supply of phosphate-deficient decomposition, at an acid concentration of more than 98%, the yield of the product / fraction remains high, but sulfur trioxide begins to be released from the reactor to the gas phase, which will require an additional purification of the exhaust gases,

The table shows the dependence of the yield of the product fraction and the content of the free acid in the pulp before granulation from T: W in the phosphate slurry suspension supplied to the decomposition (conditions of experiments: concentration

Whose raw material in the form of suspension allows 5% sulfuric acid 93%, the amount of sulfuric acid

eliminate foaming in the reactor, improve mixing conditions, obtain a more homogeneous pulp and thereby result in uniform granules, i.e. an increase in the yield of commodity fraction. Conducting, granulating, and drying at the same time allows the process to be significantly simplified due to the use of 2.1 wt.h. on 1 ma.ch. phosphate raw materials).

As can be seen from. data table, if the ratio in suspension T: J less Isl, then the yield of marketable fraction is reduced due to the formation of a small fraction of the pulp is thick, difficult

a logical chain of one apparatus, 25 equipment operation and granulation are bad. At T: W more than 1: 2.3, the overmoistening of the pulp occurs and the formation of large agglomerates at the granulation stage, which also reduces

and also allows for more precise adjustment of the ratio of the pulp and retur of the marketable fraction and, accordingly, leads to an increase in the yield of the marketable product. Use for the output of the product fraction. With an increase in the preparation of the suspension of absorption of acidity up to 4% after the granules - effluent, this production is practically wasteless. In addition, the presence in the effluent of fluorosilicic acid: its native acid and its salts also produces and increases drying by association and drying. As the drying rate exceeds the rate of interaction of phosphate with acid, which ultimately reduces the yield of the product fraction and requires additional neutralization of the product. Free acid content

it promotes the decomposition of phosphate raw materials, and their presence at the granulation stage plasticizes the pulp, improves the granulation conditions and increases the yield of the marketable product.

Below is the dependence of the yield of the product fraction on the concentration of sulfuric acid supplied to the first stage (the amount of supplied acid is 2.1 parts per hour per part of phosphate feed, T: W of the suspension of phosphate feedstock is 1: 1.1). Sulfuric acid yield,% fraction,% 7265

7578

8585

9890

10085

As can be seen from the data, when using an acid with a concentration below 75%, the yield of the product fraction decreases due to a decrease in the decomposition temperature and, accordingly, a decrease in the recovery rate.

acid supplied to the decomposition of 2.1 mach. on 1 ma.ch. phosphate raw materials).

As can be seen from. data table, if the ratio in suspension T: J less Isl, then the yield of marketable fraction is reduced due to the formation of a small fraction of the pulp is thick, difficult

nul qi At T: W more than 1: 2.3, the waterlogging of the pulp occurs and the formation of large agglomerates at the granulation stage, which also reduces

the output of the commodity fraction. With an increase in acidity up to 4% after granules -

o yield of product fraction. With an increase in acidity up to 4% after granules -

This product is obtained with a higher content of free acid, since the drying rate exceeds the rate of interaction of phosphate with acid, which ultimately reduces the yield of the product fraction and requires additional neutralization of the product. Free acid content

0 in the pulp of less than 1.5% has little effect on the yield of the product fraction.

Below is shown the dependence of the yield of the product fraction on the norm of sulfuric acid supplied to decomposition (conditions of VIA experiments: the concentration of sulfuric acid is 93%, the ratio T: W 1: 2). The rate of sulfuric acid. Output commodity ma.ch. on 1 ma.ch. 0. fraction%

1.568

1.675 2.0 80 2.5 85

2.770, When the content of acid is less than

1.6 ma.ch. by -1 ma.ch. phosphate decreases the yield of the product due to the formation of fine fractions, with an increase in the acid content of more than 2.5 due to pulp

0

five

granulation leads to the formation of large agglomerates and a decrease in the yield of the product fraction.

Feed to the first phosphate stage

In an amount of less than 60% of the initial, results in pulps, with high acidity, to neutralize which requires an increased amount of phosphorus or herd additional neutralization is required, feeding more than 90% of the syph leads to an increase in the solid phase in the suspension ... and to obtain sedentary slurries.

Note .1. 1000 kg (60% of the total amount) of apatite are mixed with absorption drains to obtain a suspension with a T: W of 1: 1.2 and fed into the reactor. There also serves sulfuric acid concentration of 75% in the amount of 2.34 May, h. on 1 ma.ch. sf. The decomposition temperature is 100 ° C. The decomposition time is 3 hours. The decomposition coefficient at the 1st stage is 96%. The result is 3000 kg of pulp containing 13% j of free phosphoric acid. The pulp is fed to the second reactor, where the remaining amount (40%) of Kingisepp phosphate, containing 28% in the form of a suspension with T: W 1: 1.2, is simultaneously fed. The temperature in the reactor is 90 ° C, the reaction time is 90 minutes. The resulting pulp contains 3% P 205 free acid. The resulting pulp is fed into a drum granulator-dryer, where it is granulated and dried with flue gases with inlet and outlet temperatures. Gases are led to an absorption step. Absorption is carried out with clarified water. The resulting effluent is used to mix with apatite and phosphate. As a result, after granulation and drying, 2642 kg of the product of the composition,%: 5 total, are obtained. 22-, Pa.05 uev. 20, J free. 3. The yield of the product fraction with a granule size of 1-4 mm is 90%.

PRI me R. 2. 1000 kg of phosphorite (83% of the total mass) containing 32% are mixed with absorption solutions in the ratio necessary to obtain a suspension with T: W 1: 2.3. Sulfuric acid concentration of 93% in the amount of 2 parts per hour. on 1 ma.ch. Piji.Og feed to the reactor. The decomposition is carried out at 96 ° C for 2 hours. The pulp is obtained in the amount of 317 kg eo free acidity of 6%

which is served in the second reactor. Tua also introduced .. suspension of phosphate with T: W 1: 2.3. Enter the rest of phosphorite (17%). A pulp with a free chicity ratio of 6% is sent to a drum granulator torus dryer, where it is granulated and dried with flue gases with an inlet temperature of 800 ° C and an outlet. Exhaust gases are led to an absorption step. The effluent from it is divided into 2 streams, one of which is directed to the first stage of decomposition, and the other ..- to the second stage. As a result, 1842 kg of product of composition,%: total. 21 j Wg 05 uy. 18j PjOs

free 2.9. The yield of product fraction is 80%.

PRI me R 3. 1000 kg of apatite (75% of the total amount), containing 36% PjOj, are fed to the reactor. There are simultaneously directed aberation solutions in an amount necessary to obtain a suspension with a T: M 1: 1.6, and sulfuric acid with a concentration of 98% in an amount of 2, 5, wt.h. on 1 mah. pheofata. The decomposition is carried out at 100 ° C for 3 hours. The pulp is obtained in the amount of 2750 kg with a free acidity of 11% 5, which from the first reactor enters the second. Phosphorite (24%) in the amount of 25% was introduced into this reactor. The pulp with evobodnogo kielnost '5.5% P-iO 5 is sent for granulation and drying into a pelletizer-dryer (like RKSG), where it is granulated and dried with furnace basins, providing

material temperature. Exhaust gases are sent for purification to an absorption stage. Absorbable solutions are displaced from the chati-tom. After granulating and drying, 1920 kg of product of composition are obtained,%: total. 22 uy. 19, PrO S bvb 3. The output of the product fraction is 85%.

The use of the proposed method allows to increase the yield of commodity fractions in the product: C 65-70 up to 75-90%, significantly simplify the production scheme by eliminating an additional neutralization stage, not adding additional reagents (for example, chalk) to the process. Drying and granulation in a stream of flue gases in a single apparatus by conducting granulation by means of an inlaid product at the granule-forming centers also has an effect on the yield of the product fraction, and the use in the process of absorption effluent reduces the pollution of the environment. In the proposed method, phosphate raw materials from different deposits can be used to produce superphosphate.

Claims (4)

1. A method of producing granulated superphosphate comprising decomposing a part of phosphate with sulfuric acid, subsequently mixing the obtained pulp with the remaining part of the phosphate raw material, granulating, drying the product, and then, in order to increase the yield fractions and simplification of the process by reducing the number of technological operations, the decomposition of phosphate raw materials is carried out with sulfuric acid 15 20 In this case, the phosphate raw material for decomposition is fed as a suspension with a T: W equal to 1: 1-2.3, and after mixing the resulting pulp with the remaining part of the phosphate raw material, granulation and drying are carried out simultaneously. 2. Method POP.1, characterized in that phosphate raw material is fed to the decomposition of sulfuric acid in an amount of 60-90% of the initial and the rest of the raw material is fed to the displacement either in a dry form or in the form of a suspension with T: W 1i (1-2.3), .1. 3. Method POPP.1 and 2, cast Due to the fact that the granulation and drying of the product is carried out with flue gases in the granulator dryer with the subsequent absorption of flue gases. 4. The method according to claims 1-3, characterized in that for the preparation of suspensions of phosphate raw materials, HIS SEVEN iJtVAJ ЛГ1Ч h / g, "w i-tffei concentration of 75-98%, taken in the amount of 5 °, there are drains after the absorption stage of 1.6-2.5 wt.h. for 1 h, gas phosphate. The ratio of T: W in suspension 1: 0.8 1: 1 1: 1.5 1: 2.3 1: 2.5 The output of commodity fraction,% 68 The content of free acid in the pulp before granulation,% 4,0 3,5 2,5 1,5 1,5 1,2 0 five 0 In this case, the phosphate raw material for decomposition is fed as a suspension with a T: W equal to 1: 1-2.3, and after mixing the resulting pulp with the remaining part of the phosphate raw material, granulation and drying are carried out simultaneously. 2. Method POP.1, characterized in that phosphate raw materials are fed to the decomposition of sulfuric acid in an amount of 60-90% of the initial and the rest of the raw material is fed to the displacement either in a dry form or in the form of a suspension with T: W 1i (1-2.3), .1. 3. Method POPP.1 and 2, cast This is caused by the fact that the granulation and drying of the product is carried out with flue gases in a granulator dryer with the subsequent absorption of flue gases. 4. The method according to claims 1-3, characterized in that for the preparation of suspensions of phosphate raw material is used 5 ° there are effluents from the gas absorption stage. 75 80 85 80