Amine regeneration flowsheet

Figure 4-1 is a process flowsheet showing how amine solution is circu­lated to various refinery scrubbers to absorb H2S. The lean amine chemically combines with H2S (and unavoidably some C02) in the scrubbers. The resulting rich amine is stripped in the regenerator. Released acid gases (H2S and C02) are charged to the sulfur recovery plant.

Amines are an organic base. When mixed with water, they turn pH paper blue. The two most common forms of amine used are monoethanol­amine (MEA) and diethanolamine (DEA). MEA is the most powerful and reactive. DEA and a host of other less-reactive amines are also used in the industry. Unfortunately, MEA is the most corrosive of the amines. It is this corrosive aspect of amine solutions that makes the operation of amine systems a challenging job.

The objective in operating an amine system is to maximize H2S recovery while keeping the solution inside the pipes and vessels—and out of the sewer. Refinery effluent-treatment plants have a limited capacity to digest amine. Even small amounts in a refinery’s outflow will violate environmental nitrogen limits.

circulating amine system

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