SU947150A1 - Process for producing complex fertilizer - Google Patents

Description

(5) METHOD OF OBTAINING A COMPLEX FERTILIZER

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The invention relates to a technique for producing complex fertilizer for the nitric-acid processing of dolomitic effects.

Known methods for producing complex fertilizers are the decomposition of natural phosphates with nitric acid, followed by isolation of excess calcium by cooling, separation of calcium nitrate by filtration, ammonization of the solution and drying of the finished product}.

A disadvantage of the known methods is that in the processing of phosphates with a high carbonate content, the stage of decomposition of the raw materials is difficult due to the foaming of the pulp, which leads to a decrease in the utilization rate of the raw materials.

The closest to the proposed method is the decomposition of pre-decarbonated calcination at 780PC of dolomitized phosphate raw material (SOD) with 55% nitric acid

and processing the resulting pulp into the finished product by known methods (cooling, removing calcium nitrate from the solution, neutralizing the nitrate-phosphate solution to pH 5 with ammonia gas, mixing ammonium pulp with potassium salt, granulation and drying) 2.

The disadvantage of this method is the complication of the process due to the preliminary calcination of the raw material and, consequently, an increase in the cost of the product due to the presence of an additional stage (raw material calcination) and the associated costs for fuel and equipment. In this process, there is a low degree of freezing of calcium nitrate 70-75, which leads to a low content in the final product PyjOy in a water-soluble form (65-70).

The purpose of the invention is to co-simplify the process and improve the quality of the finished 3. 9 by increasing the content of water-soluble P Og. This goal is achieved in that in a method involving the decomposition of pre-decarbonated dolomitized phosphate raw material with nitric acid and processing the resulting pulp, decarbonization is carried out by treating the phosphate raw material with a 58-b5% nitric acid in the amount of 100-150% of stoichiometry decomposition of carbonates within 10–20 min, and decomposition with 50–55% nitric acid is carried out for 50–60 min at stoichiometric rate for CaO with subsequent separation of calcium nitrate from living. The distinctive features of the invention allow, in addition to the decarbonization of phosphate, to evaporate a part of the water. In this case, in the first stage, calcium nitrate is precipitated as anhydrous crystalline hydrate. During the subsequent treatment of decarbonated phosphate with a weaker nitric acid (50-55% HNO3 together with 58-65% HNO, which is used in the first stage), anhydrous calcium nitrate is recrystallized into a four-water crystalline hydrate, which for each mole of calcium nitrate binds a mole of water. This makes it possible to increase the concentration of the solution and, accordingly, the degree of freezing of calcium nitrate in the next stage — while cooling the nitric acid extract. Increasing the degree of freezing of Ca (NO) -L-H, up to 82-93%, will allow to obtain a fertilizer in which the chRc is in water-soluble form against 75-70% in the known method. Heating phosphate to 80-150 ° C is necessary for better decarbonization of the raw material and evaporation of water, which, combined with the use of strong nitric acid in the first stage, results in anhydrous calcium nitrate. Phosphorite, treated in the first stage with nitric acid, is a granular mixture, during which no foam release is observed in the rest of the nitric acid. The use of stronger nitric acid in the first stage, and in the second, weaker is in sum equivalent to the use of 588% nitric acid at its stoichio metric of CaO, but the degree of freezing of calcium nitrate (depending on the concentration of nitric acid) on 12-18% higher; Example 1. The raw material used is phosphorite from the Karatau deposit, of the following composition, wt.%: Pfl 26.3; WITH 8.0; CaO 2,6; MDO 3.0. 100 weight.h. phosphorite, preheated before, is treated in a screw-mixer for 20 minutes 39, kg of 58% nitric acid (100% of carbonates stoichiometry). At the same time, 48% of CO-C, 16 kg of sal are emitted from the total mass contained in the raw material into the gas phase. The mixture, containing 3.84 kg of CO 2, is sent to the decomposition reactor, in which it is treated with 168 kg. nitric acid (l20% of stoichiometry on CaO) for 50 minutes at 60 ° C. The nitric acid extract in an amount of 303.24 kg is cooled to -15 ° C in a shell-and-tube heat exchanger and 210.24 kg of calcium nitrate is separated by filtration, which is used for conversion. The degree of freezing of calcium nitrate is 82%. The solution in the amount of 93.0 kg is processed into the finished product by ammoniation of 16 kg of gaseous ammonia in the presence of 73.2 kg of a 50% NH.NO solution (from the stage of conversion of calcium nitrate to balance the N: P ratio) with parka 29.2 kg of water. Received 153 kg of the finished product - nitroammofoska brand 17:17:17 contain 77% in water-soluble form. Example 2. 100 kg of phosphate, heated to 80 ° C, are treated for 20 minutes in an auger-mixer 59.0 kg of 58% nitric acid (150% of carbonates stoichiometry). In this case, 75% of CO2 (6 kg) of phosphorite contained in the gas phase is released. The charge, containing 2 parts by weight, CO, is sent to the decomposition reactor for processing 147 parts by weight of nitric acid (the norm is 120% of the total temperature of CaO) for 50 minutes at. A 300 kg nitric acid extract is cooled down in a shell-and-tube heat exchanger and 207.5 kg of calcium nitrate is separated by filtration. The degree of freezing of calcium nitrate is 84%. The solution in the amount of 91.5 kg is processed into the finished product as in Example 1,

Nitroammofoska contains 79 in water-soluble form.

Example 3-100 kg of phosphorite preheated before, are treated for 10 minutes in a screw-mixer with 35.2 kg of nitric acid (100 from stoichiometry for carbonates). In this case, 63% of CO2 (5.02 kg) of the total mass contained in the raw material is released into the gas phase. The mixture containing 2.98 kg C0d is sent to the decomposition reactor for treatment 184, kg of nitric acid (norm iO% of stoichiometry on CaO) for 60 minutes at 60 ° C. The nitric acid extract in the amount of 31.58 kg is cooled in a shell-and-tube heat exchanger to -15 ° C and 225.58 kg of calcium nitrate is separated by filtration. The degree of freezing of calcium nitrate is 91. The solution in the amount of 89.0 parts by weight. processed into the finished product as in example 1. The nitroammophoska contains B6% RL 0 in water-soluble form.

Example 4. 100 kg of phosphorite, heated to 150s, are treated to min in auger-mixer 52.6 kg of nitric acid (150 from stoichiometry to carbonates). In this case, 81 CO (6C, kB kg) from about & mass of the mass contained in the raw material is released into the gas phase. The mixture containing

1.52 kg of COj, are sent to the decomposition reactor to process 1b2 kg of 50% nitric acid (120 from stoichiometry on CaO) for 60 min at 60 ° C. 308.12 kg of nitric acid extract is cooled to a shell-and-tube heat exchanger and 220.92 kg of calcium nitrate was filtered off. The degree of freezing of calcium nitrate is 93. The solution in the amount of 87.2 kg is processed into the finished product according to Example 1. The nitroammophos contains 87% of a soluble form.

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The table shows the data confirming the receipt of a positive effect with the introduction of the process in the proposed range of parameters.

In carrying out the process for

In addition to the limits of the proposed parameter intervals, the main process indicators are degraded.

The proposed method allows efficient processing of dolomitization.

5 raw materials due to its preliminary decarbonization, and also increases the degree of freezing of calcium nitrate by 20–25% due to an increase in the concentration of the starting nitric acid when it interacts with carbonates and correspondingly increases the content in fertilizer and 0 in water-soluble form.

Claims (2)

Invention Formula The method of obtaining complex fertilizer from dolomitized phosphate raw material by its preliminary decarbonization followed by decomposition of SS% nitric acid and processing the resulting pulp, characterized in that, in order to simplify the process and improve the quality of the finished product, decarbonization is carried out by processing the preheated 80-150 ° C phosphate raw material 58-b5% nitric acid in the amount of 100-150% of stoichiometry on decomposition of carbonates within minutes, and decomposition of 50-55% nitric acid are 50-60 minutes at. its chiometric rate on CaO with the subsequent separation of calcium nitrate by freezing. Sources of information taken into account in the examination .one. Pozin ME, Technology of mineral salts. L., Chemistry, T. 2, lE7, p. 1307-1358. 2. Gzasop. techn. 1972, 7b, no. 8 p. 50-53.