Over 5 years, 70 to 80 FGD scrubber units have exhibited corrosion problems. Many were after only a few months of service. This paper will provide an overview of readily available technical information in the published literature and past experience that could have been used to minimize corrosion problems in these FGD units.

 

Liquid absorbents have been utilized for decades to remove impurities from produced natural gas. Throughout the last 15 years, monoethanolamine (MEA) triazine has become an industry-recognized name for the removal of sour gas (H2S). MEA triazine has one of the lowest cost profiles in terms of cost per mass of H2S removed and has obtained a commodity status. It is widely used in the oil and gas industry, both on production (upstream, midstream) and processing (downstream). MEA Triazine is typically applied via direct injection into flowlines or applied in contactor vessels (“scrubbers”, “towers”, “bubble columns”). The application type depends on numerous factors but in general, the application via contactor vessel is preferred due to its increased efficiency. However, due to the many different contactor configurations available, a wide range of efficiencies are achieved, ranging from 50 – 70%. MEA Triazine systems are also known to foul with acid-insoluble polymeric solids. This occurs when the MEA Triazine and its reaction products are not managed properly, or the system is not designed for the specific conditions. The spent material, commonly referred to as dithiazine, can form solids (amorphous dithiazine) in the contactor packing, post contactor separator, or in downstream pipelines if carry-over occurs. This paper aims to provide the reader guidance on how to optimize MEA Triazine contactor vessels to achieve maximum efficiency and to reduce or eliminate fouling. Optimization principles discussed will include contactor configurations, contactor modifications, and MEA Triazine properties and its effect on system performance. Increasing system efficiency and eliminating solids formation in these systems will have a direct impact on the user’s operating expense (OPEX). This is due to better scavenger utilization and a reduction in maintenance and downtime due to solids formation. A reduction in scope three emissions will also be achieved.