(71g) Low Energy Direct Contact Condenser Designs for Claus Tail Gas Treating Units In Desert Environments

Authors: 
Kister, H. Z., Fluor Corporation
Chow, T. K., Fluor Corporation
Nielsen, D. B., Fluor Corporation
Sanchez, A. E., Fluor Corporation


In a conventional Claus/Hydrogenation Sulfur plant design, tail gas from the Claus plant is hydrogenated to convert all the sulfur species to H2S and the tail gas is then cooled in a Direct Contact Condenser (DCC) before the H2S is removed from the tail gas by treating with generic or formulated MDEA or a specialty solvent such as ExxonMobil’s Flexsorb SE® or SE Plus®. The feed gas to the MDEA or Flexsorb system has to be cooled in the DCC to a certain minimum temperature in order to meet SOx emission requirements.

In many situations, especially in arid regions, DCC air coolers cannot cool sufficiently to meet SOx emission requirements and cooling water is usually not available for trim cooling. Instead of using cooling water for DCC trim cooling, many Claus/Hydrogenation Sulfur plants in these environments must use refrigerant to cool the tail gas to the appropriate temperature.. Conventional DCCs utilize a single pumparound that takes the process water from the bottom of the DCC column, through air coolers, followed by cooling water or refrigerant coolers for trim cooling, and then back to the top of the column. For this type of design, the air coolers provide about half the duty and the refrigerant or water coolers provide the other half.

Fluor has invented a new DCC design that transfers as much as 50% of the trim cooling duty to the air coolers. An evaluation of a recent large-scale Middle East project indicated that this new design would result in about $20 MM in power savings over the 20-year life of the plant and an additional $70 MM in capital cost savings. Other Claus/Hydrogenation sulfur recovery facilities can achieve significant savings in proportion to the size of the plant.

This paper provides a technical background for Fluor’s new patent pending Direct Contact Condenser technology, and discusses the economic advantages and operational flexibility that can be realized through its implementation.