Ammonia separating process for ammonia synthesis

Abstract

The invention relates to an ammonia separating process for ammonia synthesis, in particular to an absorption ammonia separating process. In the ammonia separating process, two units of absorption ammonia separating and absorption refrigeration are merged, wherein in the unit of the absorption ammonia separating, ammonia is absorbed and separated, and is desorbed and condensed to form liquid ammonia serving as a product; and in the unit of the absorption refrigeration, the refrigeration is performed by utilizing the absorption principle so as to provide refrigeration capacity for the absorption of the ammonia. The ammonia separating process is mainly characterized in that in the processes of the ammonia separating and the refrigeration, heat transfer and mass transfer are performed simultaneously, an absorption method is adopted, ammonia stilling equipment is shared, and absorption barren liquor is processed together; the heat of the ammonia stilling process is derived from low heat energy of ammonia synthesis gas; liquid ammonia serving as a cold source in the process of the refrigeration is one part of the liquid ammonia serving as the product, and an analyzer and a condenser are not needed to be arranged individually; and absorption working medium pairs adopted by the absorption ammonia separating and the absorption refrigeration are sodium thiocyanate-ammonia working medium pairs, sodium thiocyanate is not contained in a vapor phase, and ammonia is separated from sodium thiocyanate-ammonia solution easily. Compared with the conventional condensate ammonia separating, the ammonia separating process of the invention has the advantages that: the power dissipation of ice machines is replaced by the recovered low heat energy, and the effect of energy conservation is obvious.

Description

technical field [0001] The invention relates to an ammonia separation process for ammonia synthesis, in particular to an absorption type ammonia separation process. Background technique [0002] Ammonia is synthesized from nitrogen and hydrogen. Since the content of ammonia in the gas after the synthesis reaction is not high, generally only 12% to 22%, it is necessary to extract the ammonia from the tower synthesis gas (mainly nitrogen, hydrogen, ammonia, which is called product gas here). Ammonia is separated (often referred to as "ammonia"), and the remaining nitrogen and hydrogen gas (called cycle gas) is returned for recycling. The methods of separating ammonia mainly include condensation method and absorption method, and condensation method is basically used at present. In the history of the development of ammonia synthesis, the absorption method has been used, but because the absorbent used is water, water will be entrained in the circulating gas after ammonia separat...

AI Technical Summary

Problems solved by technology

In the history of the development of ammonia synthesis, the absorption method has been used, but because the absorbent used is water, water will be entrained in the circulating gas after ammonia separation, which will cause poisoning of the catalyst for ammonia synthesis, and nitrogen and hydrogen will dissolve in water under high pressure. This leads to the loss of nitrogen and hydrogen, so the process of absorbing and separating ammonia in the large-scale synthetic ammonia industry is eliminated, and it is only used in some small fertilizer processes for the production of ammonia water

Although the ammonia separation by condensation overcomes the problems of catalyst poisoning and other problems, it must fully cool down the synthesis gas under high pressure, and consumes a lot of refrigeration work in the ammonia cooling link.

If the operating pressure is reduced, the difficulty of condensing and separating ammonia will further increase

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