SK279011B6 - Method for conversion of ammonium sulphate to potassium sulphate - Google Patents

Abstract

This conversion procedure is initiated mixing of water solutions related to ammonium sulphate and potassium chloride in a molar ration of pure salts 1 up to 1,25 : 2, after that a molar ration of water related to molar ratio of incoming salts 7,5 up to 5,0 : 1 is provided, which is aimed based on this principle a partial amount of water is being evaporated and a hot suspension is being cooled to the temperature of +45 up to +20 Celsius degrees after that, and the pH value corrected, when supplying ammonium so that, the pH value in the interval of 7 up to 12 is reached, however the suitable value is 10, and a separation of crystal of the such prepared suspension is provided, while the separated crystalline prepared based on this suspension is being washed with the use of water. The prepared crystalline of potassium sulphate containing less than 1,5 weight percent of chlorides and 0,6 up to 3 weight percent of 0,6 up to 3 weight percent ammonium nitrogen is applied as potassium manure.

Description

Technical field

The present invention relates to a process for the conversion of ammonium sulfate to potassium sulfate by mixing aqueous solutions of ammonium sulfate and potassium chloride in a molar ratio of pure salts of 1 to 1.25 to 2.

BACKGROUND OF THE INVENTION

Potassium sulphate is a synthetic potassium salt used mainly as a potassium fertilizer for the cultivation of flowers, vegetables, fruit, tobacco and other plants not tolerating the high concentration of chlorides contained in the cheaper potassium fertilizer - potassium chloride.

The dominant method of potassium sulfate production is the double decomposition of schonite mineral with potassium chloride according to the reaction:

Kaso ₄ . MgSO '. 6 H ₂ 0 + 2KC1 - 2R ₂ SO ₄ + MgCl _second 6H ₂ O

Ammonium sulfate is a synthetic nitrogen fertilizer. It is currently produced by treating its aqueous solutions resulting from the synthesis of caprolactam, methyl methacrylate and the ammonia scrubber containing sulfur oxides.

The large increase in the reported production linked to the necessary by-product ammonium sulphate led to an extraordinary increase in the production of ammonium sulphate and caused its price to fall below the value of the raw materials contained therein.

This situation is the reason for the search for methods for more efficient utilization of ammonium sulfate.

One possible solution to the problem is the conversion of ammonium sulphate to potassium sulphate by the action of potassium chloride in the technical literature, according to the equation:

(NH ₄ ) ₂ 5O ₄ + 2KCl ---> - K ₂ SO ₄ + 2NH ₄ C1

The reaction described in CS AO no. 269030. Its disadvantage is higher energy consumption and lower yield.

It is an object of the present invention to provide a process for achieving high yields and good quality of potassium sulfate.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a process for converting ammonium sulfate to potassium sulfate by mixing aqueous solutions of ammonium sulfate and potassium chloride at a molar ratio of pure salts of 1 to 1.25 to 2 by adjusting the molar ratio of the the sum of moles of the incoming salts to 7.5 to 5.0 to 1, the hot suspension is cooled to +45 to + 20 ° C, the ammonia is adjusted to pH 7.0 to 12.0 by addition of ammonia, preferably pH 10 1.0, and such a suspension is separated by washing the separated crystal with water.

The advantage of the conversion of ammonium sulfate to potassium sulfate according to the invention is the low energy consumption of the process, as the aqueous ammonium sulfate solution directly enters the conversion.

The advantage of the process is to achieve 86 to 93 percent recovery of potassium sulfate per conversion of more expensive potassium chloride.

Another advantage of the process is to obtain a product with a low chloride content - at a level of 0.3 to 1.0% by weight. and 100% solubility of the salt obtained.

A characteristic feature of the technical potassium sulphate produced by the process of the invention is the simultaneous presence of ammoniacal nitrogen at a concentration of 0.6 to 3.0% by weight, which partially classifies it as a two-component potassium-nitrogen fertilizer.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

400 g of an aqueous ammonium sulfate solution containing 150.8 g of a soluble salt was mixed with 450 g of an aqueous potassium chloride solution containing 149.1 g of a soluble salt.

13.4 g of water were evaporated from the resulting suspension under atmospheric pressure.

The hot suspension at 108 ° C was cooled in a water bath with stirring. Ammonia gas was suspended in the suspension at + 60 ° C. The suspension was cooled to + 28 ° C and adjusted to pH 11.

The suspension thus treated was separated by vacuum filtration. The crystal was washed with 30 g of water. After drying, 161 g of salt and 578 g of mother liquor were obtained. The yield of K ₂ SO ₄ crystal was 92.4%.

Example 2

1807 kg / h was fed into the mixer via a metering pump. aqueous potassium chloride solution containing 594.2 kg of pure salt. A second metering pump supplied 1379 kg / h to the same mixer. aqueous ammonium sulfate solution containing 579.3 kg of pure salt.

The solution mixture was continuously fed to a vacuum evaporator operating at an absolute pressure of 40 kPa. At a temperature of about 70 ° C, 398.2 kg / h were distilled off from the mixture. water. The hot slurry flowed to a crystallizer with forced circulation of the slurry through a condenser where it was cooled to + 33 ° C. The cooled slurry was fed with ammonia gas at a rate of 8 kg / hr to adjust the pH of the solution to 9.5-10.5.

The suspension was drained onto a centrifuge. The centrifuged crystal was washed with 80 L / h. water.

The amount of potassium sulfate produced per hour after drying to a water content of 0.4% by weight. amounted to 598 kg ·

Analyzes revealed a chloride content of 0.56% by weight, a sulfate content of 55.9% by weight in the dried product. and an ammonia cation of 3.4%, which corresponds to 49% K ₂ O and 2.7%

Claims (1)

A process for converting ammonium sulfate to potassium sulfate by mixing aqueous solutions of ammonium sulfate and potassium chloride in a molar ratio of pure salts of 1 to 1.25 to 2, characterized in that the molar ratio is adjusted by evaporating water against the sum of moles of the incoming salts to 7.5 to 5.0 to 1, the hot suspension is cooled to +45 to +20 ° C, the pH of the ammonia is adjusted to 7.0 to 12.0, preferably to pH 10.0, and such a suspension is separated while washing the separated crystal with water.