Method for preparing ammonium sulfate by conversion of phosphogyspum with polycrystalline method

Abstract

The invention relates to a method for preparing ammonium sulfate by continuous conversion of phosphogyspum with a polycrystalline method, belonging to the technical fields of resource comprehensive utilization and chemical industry, and relates to a method for producing ammonium sulfate by conversion of phosphogyspum with a polycrystalline method based on a byproduct phosphogyspum in a (sulfuric acid) wet phosphoric acid industry as a main raw material. The production process comprises the following steps: (1) pretreating the raw material of phosphogyspum discharged in the wet phosphoric acidindustry so as to obtain purified phosphogyspum; (2) absorbing ammonia and carbon dioxide with a ammonia-sulfate-containing primary lotion which is produced by washing a calcium carbonate filter cakewith water in a filtration process in a carbonation tower so as to produce an ammonia sulfate and carbonate solution; (3) connecting a calcium carbonate polycrystalline nucleus generator with a multiple-tank or multiple-partition groove type reactor with a stirrer in series to constitute a conversion crystallizer; (4) filtering a reaction material slurry discharged from the conversion crystallizer so as to obtain a filter cake and filtrate containing 38-40% by weight of ammonium sulfate; (5) carrying out secondary countercurrent washing on the filter cake obtained in the step (4) with clear water, and feeding the ammonia-sulfate-containing primary lotion to the carbonation tower for absorbing gas ammonia and carbon dioxide so as to produce an ammonia sulfate and carbonate liquid; and (6) neutralizing and decarburizing the filtrate containing ammonium sulfate from the step (4) with sulfuric acid, then centrifugally separating so as to obtain a crystal containing wet ammonium sulfate, separating out a mother liquid, carrying out cycle concentration on the mother liquid, and drying the crystal containing wet ammonium sulfate so as to obtain a finished product ammonium sulfate.

Description

technical field [0001] The invention belongs to the fields of resource comprehensive utilization and chemical technology, and relates to a method for producing ammonium sulfate by using phosphogypsum, a by-product of the wet-process phosphoric acid industry (sulfuric acid method), as a main raw material, and converting phosphogypsum by polycrystallization. technical background [0002] Sulfur is the fourth plant nutrient along with nitrogen, phosphorus and potassium. Studies in many countries have shown that S:N in soil is less than 1:5; S:P 2 o 5 If it is less than 1:3, it can be considered as a lack of sulfur, which will cause a decrease in the utilization rate of N and P elements by plants. With the development of contemporary society and economy, the "three wastes" treatment measures are becoming more and more perfect, and the sulfur lost to the rivers and the atmosphere in the industry is decreasing day by day. In addition, a large amount of sulfur-free high-concent...

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Problems solved by technology

[0006] On September 24, 2008, the Chinese Patent Office disclosed "A Method for Producing Ammonium Sulfate Using Phosphogypsum as a Raw Material" (publication number: CN101269823A); Calcium method” (publication number: CN101492178A), and related patents published over the years in which the intermediate step is the production of ammonium sulfate from phosphogypsum, none of these patents involves the development of process technology to improve the filtration strength of the conversion product calcium carbonate filter cake; Does not involve research on the continuous conversion process of polycrystalline phosphogypsum; does not involve the utilization of calcium carbonate filter cake washing water; for SiO-containing 2 The utilization of high-silicon calcium carbonate slag with w%≥15% is not involved

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