Selection of Claus flue gas treatment process
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Currently, the SCOT process is commonly used for Claus off-gas treatment in natural gas processing plants. However, for plants with a capacity of less than 50,000 tons per year, the SCOT process is relatively complex and costly. I was wondering if anyone has projects that use alkaline methods to treat Claus off-gases? How are waste liquids or alkaline residues disposed of?
Today’s environmental standards are stricter; SCOT is no longer determined by the scale of the facility. We have been using SCOT since 1998 for sulfur production of 5,000 tons per year, and it was also used for productions of 20,000 tons per year in 2002 and 40,000 tons per year in 2012.
Direct complexation with ionic liquids for desulfurization is the simplest method
The SCOT process is also an option, but given the strict environmental regulations, existing SCOT plants need to be modified to meet these requirements. For newly built plants, various exhaust gas treatment processes such as alkaline washing and ammonia washing can be added after the SCOT process. Existing devices handle CLAUS flue gas directly and absorb SO2 after combustion, such as the ionic liquid washing process and the power wave washing process. Ionic liquid washing uses an organic amine that is different from MDEA, while power wave washing can employ either alkalis or ammonia. Indeed, as the original poster said, the issue of waste liquid is a drawback of the alkaline method; different people have different opinions on this.
Alkaline methods for hydrogen sulfide removal generate by-products salts, which can lead to secondary pollution through the discharge of waste fluids. Our company specializes in the wet method of removing hydrogen sulfide using complexed iron, and we have a track record of successful implementations on offshore platforms in Shandong and Shanxi provinces.
I’m not very familiar with ionic liquids; is Shell’s Consolv one of them?
Thank you very much. For the new environmental standards, are there any treatment processes that do not generate waste liquid?
Both ionic liquid washing and shock wave washing generate waste liquids. In both methods, H2S is first converted to SO2 before absorption takes place; the waste liquids consist mainly of sodium sulfite solutions. Shock wave washing oxidizes these waste liquids in conjunction with air, resulting in waste liquids containing sodium sulfate salts, and all of these require further treatment. Processes that do not generate waste fluids, such as the complexed iron process, produce no waste fluid; the complexed iron catalyst is continuously recycled. However, this process is limited by equipment constraints, and due to economic considerations, it is only suitable for sulfur recovery units with a capacity of up to 10,000 tons per year. If the volume of acidic gas is low, it can be directly fed into the complexed iron process flow, but a sulfur refining system must be added.
Gases can be converted into other products, such as dimethyl sulfoxide, to increase the added value of these products
The Konsov method doesn’t address the fundamental problem.