(58c) Strategies for Acid Gas Enrichment and Tail Gas Treatment:

                                                                         Strategies for Acid Gas Enrichment and Tail Gas Treatment:

Special Solvents or Better to Stick With Generic Solvents

Tofik K. Khanmamedov

TKK COMPANY, Sugar Land / Houston, Texas

Abstract

The quality of the acid gas feed stream to sulfur recovery units is crucial for proper operation. In this regard, acid gas streams with low H₂S concentration should be enriched with H₂S. This is also true for the amine section of tail gas treating units. There are different approaches for acid gas enrichment. One approach is based on using generic N-Methyl-Diethanol Amine (MDEA) with the family of patented HIGHSULF™ processes. Other approaches use more selective and very expensive solvents.

Also there are claims that some specialty solvents allow designing units using relatively smaller equipment than in case of MDEA, there are limited advantages in long term to say the least.

Due to depreciation of the unit in most cases the capital cost is not the primary concern of the clients. Even operating cost based on the use of local sources of power is not the major issue. However, they do seriously care about the costs of the solvents, that they have to purchase annually from the single foreign vendors and this factor limits their freedom of the choice. While this approach might reduce initial capital cost, it could significantly increase the operating costs over time due to the necessity to continue to purchase the expensive specialty solvents from the single vendor.

In most cases, switching from special solvents to generic, less expensive, solvents in the future would require a reduction of the overall unit capacity. Units designed for MDEA based HIGHSULF™ technologies can be easily switched to other specialty solvents within certain capacity constraints.

This paper focuses on advantages of the MDEA based family of HIGHSULF™ processes that require no additional equipment.