Ammonia and carbon dioxide separation method

Abstract

The invention relates to an ammonia and carbon dioxide separation method. The method comprises the following steps: mixed gas containing ammonia and carbon dioxide is delivered into an absorption tower, and a carbon dioxide absorbent and a low-boiling-point substance are introduced; under the heating of a reboiler, ammonia-containing gaseous substance is recovered from the tower top, and a potassium bicarbonate rich liquor containing the low-boiling-point substance is obtained at the tower bottom; the potassium bicarbonate rich liquor containing the low-boiling-point substance is delivered into a recovery tower; the low-boiling-point substance is obtained at the tower top under the heating of a reboiler, and is recycled in the absorption tower; the potassium bicarbonate rich liquor with the low-boiling-point substance removed is obtained at the tower bottom; the potassium bicarbonate rich liquor with the low-boiling-point substance removed is delivered into a desorption tower; under the heating of a reboiler, carbon dioxide is obtained at the tower top, and potassium bicarbonate lean liquor is obtained at the tower bottom; the potassium bicarbonate lean liquor is returned to the absorption tower, and is reused as a carbon dioxide absorbent. With the ammonia-carbon dioxide separation method, a carbon dioxide recovery rate is close to 99.95%, and absorption tower bottom ammonia content is lower than 0.05%. Therefore, a problem of separation failure caused by the crystallization of ammonia and carbon dioxide is effectively solved.

Description

technical field [0001] The invention relates to the technical field of removing carbon dioxide in a mixture, in particular to a method for separating ammonia and carbon dioxide. Background technique [0002] A mixture of ammonia and carbon dioxide is produced during the production of urea or the synthesis of melamine from urea. How to efficiently separate ammonia and carbon dioxide from the mixed gas and make them as recycled materials or co-products / by-products plays a crucial role in the efficiency and economy of the production process. [0003] A special property of the mixture of ammonia and carbon dioxide is that, under normal pressure below about 59°C, the two tend to react spontaneously to form ammonium carbamate solid (Ammonium carbamate, referred to as methyl ammonium), which can easily lead to blockage of equipment and / or pipelines. However, since the boiling point of ammonia (-33°C under normal pressure) and carbon dioxide (-78°C under normal pressure) are far be...

AI Technical Summary

Problems solved by technology

[0008] One object of the present invention is to provide a kind of separation method of ammonia and carbon dioxide, this separation method adopts absorption decarburization process, introduces potassium carbonate solution as absorbent, introduces low boiler in the absorption tower, improves carbon dioxide recovery rate, realizes ammonia, carbon dioxide The high-efficiency separation effectively solves the problem that ammonia and carbon dioxide are easy to crystallize and cannot be separated

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