CS262572B1 - Process for treatment ammonium sulphate - Google Patents

Abstract

The aim is to treat waste sulphate ammonium formed during some chemical productions. The method uses thermal decomposition of ammonium sulfate, preferably catalyzed, carried out under normal or pressure. In the first phase of decay the ammonia is cleaved to form ammonium hydrogen sulphate melt, in the second Phase oxidation of the remaining chemical occurs bound ammonia by the sulfate residue sulfur dioxide. Self reaction can be carried out in liquid or gas phase.

Description

The present invention relates to a process for the treatment of ammonium sulfate produced as waste during certain chemical processes.

The prior art methods of treating ammonium sulfate consist mainly of using ammonium sulfate as fertilizer, either alone or in the form of combined fertilizers. However, this use has recently become less important due to the adverse consequences of its application in agriculture. The disadvantage of treating ammonium sulphate as fertilizer is its low nitrogen content, high sulfur content and, in particular, the effect on reducing soil alkalinity.

The aforementioned drawbacks are overcome by the process for the treatment of the ammonium sulfate according to the invention. It consists in subjecting the ammonium sulphate to a continuous technical decomposition until substantially half of the ammonia is cleaved, and then the resulting ammonium hydrogen sulphate melt undergoes an oxidative reduction decomposition at a temperature above 500 ° C. According to a further feature of the invention, a catalyst based on transition metal compounds is added during the decomposition. It is further preferred to add air or oxygen or nitric acid.

The advantage of the process according to the invention is that the process leaves no waste, it can be carried out with minimal energy and material costs directly in the production unit producing waste ammonium sulphate and engaged in the production of sulfuric acid with minimal technology modification. The ammonia obtained by the process according to the invention can be completely recycled in a process that converts it into ammonium sulfate or otherwise used. The dried offgasses, consisting essentially of a mixture of pure sulfur dioxide and nitrogen, possibly with an unreacted excess of air oxygen, may be used after the post-treatment with dried air to produce sulfur trioxide on the contact catalyst.

The process according to the invention is an environmentally friendly process.

The process according to the invention is described in more detail below on two laboratory scale batches.

He did

132 g of ammonium sulfate (1 mol) was heated in a 300 ml fractionated glass flask equipped with a 35 cm reflux air condenser. Leaking gases were collected at the top of the condenser and absorbed in 800 ml dest. water. During the heating of the contents of the flask to about 530 ° C, half of the bound ammonia was cleaved to form a clear melt, which boils without further decomposition at about 550 ° C with further heating at atmospheric pressure. The contents of the flask was then added 18.1 g of vanadium pentoxide V ₂ Oj ^{and REA} CTION mixture was heated just enough that the temperature does not exceed the boiling point of ammonium bisulfate. In the process, vigorous gas evolution takes place and within 20 minutes the contents of the flask are decomposed to form a mixture of sulfur dioxide, nitrogen and a small amount of ammonia. After cooling off the off-gas, a condensate consisting of a solution of ammonium sulfite is formed, and the gaseous portion contains practically pure sulfur dioxide and nitrogen in a molar ratio of 1: 1.

Example 2

132 g of ammonium sulphate (11 mol) was heated in a 300 ml fractionated flask, flushed with incandescent nitrogen, equipped with a heated contact pad of the vanadium catalyst heated to 550 ° C. The contents of the flask were heated up to the boiling point of the gradually formed melt, with the off-gases produced in this heating phase being collected separately and containing only ammonia.

After the ammonium bisulfate melt was boiled, a slight stream of air was introduced below the reaction mixture in the flask and passed through the contact catalyst bed. The amount of air was chosen so as to ensure a constant excess of oxygen in the catalyst bed. The resulting fumes of the sulfuric acid after condensation to about 83% H 2 SO 4 solution contained less than 0.5% by weight. ammonium sulfate.

Claims (3)

A process for treating ammonium sulfate, characterized in that the ammonium sulfate is subjected to a continuous thermal decomposition until half of the ammonia is cleaved, and the resulting ammonium hydrogen sulphate melt is subjected to an oxidative reduction decomposition at a temperature above 500 ° C, 2. A process according to claim 1, wherein the decomposition comprises a catalyst based on transition metal compounds. 3. The process of claim 1 wherein air or oxygen or nitric acid is added to the reaction mixture.