CS265291B1 - Process for the processing of crystalline ammonium sulfate - Google Patents

Abstract

The aim of the solution is to convert crystalline ammonium sulphate into a granular spreadable product. This objective is achieved by first preparing a mixture containing 98 to 99.9% by weight of crystalline ammonium sulphate and 2 to 0.1% by weight of powdered calcium carbonate, based on the pure anhydrous substance, and then pressure granulating this mixture.

Description

(57) The purpose of the solution is to convert crystalline ammonium sulphate into a granular spreadable product. This object is achieved by first preparing a mixture containing 98 to 99.9 wt. % crystalline ammonium sulfate; and 2 to 0.1 wt. of calcium carbonate powder, based on pure anhydrous material, and then the mixture is pressure granulated.

CS 265291 Bl

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The invention relates to a process for converting crystalline ammonium sulfate into a granular product.

In the manufacture of caprolactam and other products, large amounts of ammonium sulfate are eliminated in the crystalline form. The main customer is agriculture, but with a downward trend. Surplus ammonium sulphate is stored in open landfills, which pose a high environmental risk. · The solution does not seem to be the sale of surplus ammonium sulphate abroad at a loss price. One of the barriers to higher sales in the agricultural sector is the crystalline form of ammonium sulphate, unsuitable for transport, storage and especially application by spreading or otherwise. It can be assumed that the granulated product would have significantly better sales opportunities.

Granulation of ammonium sulphate in a wrapping process is known. The crystalline form of ammonium sulfate is not suitable for this granulation method.

and

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Pressure granulation of ammonium sulfate is also known. It was verified several years ago with a fairly good result. It was, however, the processing of the powder product from the spray drier. Pressure granulation of ammonium sulfate with urea has the advantage that a product with a higher nitrogen content is obtained. However, in the ammonium sulphate pressure granulation tests from the caprolactam plant, it has been shown that the crystalline product has properties that significantly impair the pressure granulation process, both in the treatment of the ammonium sulphate alone and in admixture with urea. The behavior did not change significantly by wetting the mixture. Other tackifiers have not been tested.

Recently, it has been found that the quality of ammonium sulfate can be improved by pressure granulation of mixtures containing 75 to 98% by weight. % of crystalline ammonium sulfate? 2 to 25 wt. calcium nitrate or calcium chloride. Strengthening of the granules is probably achieved by conversion of ammonium sulfate to calcium sulfate.

Even more advantageous in terms of maintaining the purity of the original ammonium sulfate appears to be a process for converting the crystalline ammonium sulfate that is lost in the production of organic products such as formic acid or caprolactam to the granular product of the present invention, comprising preparing a mixture containing 98-99, 9 wt. % crystalline ammonium sulfate; and 2 to 0.1 wt. of calcium carbonate powder, based on pure anhydrous material, and then the mixture is pressure granulated.

By tableting tests and subsequent quarter-trial test, it was shown that the behavior of crystalline ammonium sulphate during pressure granulation is significantly improved by the slight addition of powdered calcium carbonate.

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By crystalline ammonium sulphate is meant ammonium sulphate formed by crystallization from solution and not by drying of water, for example in a spray drier. Calcium carbonate powder means ground limestone or precipitated calcium carbonate, the limestone finely ground according to ČSN 72 1250.

• The addition of calcium carbonate powder alters the flow properties of the feed mixture and, apparently, the external friction angle, provides good draw-in between the rolls and increases the working pressure, which is a prerequisite for good pressure granulation and sufficient granulate strength.

The addition of powdered calcium carbonate significantly improves the physico-mechanical properties of the granulate without requiring drying. Due to the low addition of calcium carbonate powder, there is practically no reduction in the concentration or purity of ammonium sulfate.

Example

The continuously prepared mixture of 99.7 kg / h of crystalline ammonium sulfate, 0.3 kg / h of ground limestone and 100 kg / h of the return material from the previous operation was pressed between the rollers of a two-roll granulator and the resulting sheets were crushed. The crushed mixture was screened on a 2-mesh screen with 2x2 mm and 4x4 mm sieves. The entrained fraction from the coarse sieve was returned to the crusher, the 2 to 4 mm fraction was withdrawn as product and the sub-sieve fraction from the fine sieve returned to the raw material mixing operation. The whole operation was operated continuously. The strength of the granules thus produced complied with the usual requirements for storage or spreading.

Claims (1)

OBJECT OF THE INVENTION 265 291 A process for converting crystalline ammonium sulphate, which is produced during the production of organic products such as formic acid or caprolactam, into a granular product, characterized in that a mixture containing 98 to 99.9% by weight of a mixture is prepared first. % crystalline ammonium sulfate; and 2 to 0.1 wt. of calcium carbonate powder, based on pure anhydrous material, and then the mixture is pressure granulated.