The sour gas and sulfur industry is experiencing significant growth due to rising global demand, extending from traditional uses in fertilizers to new applications in the energy transition sector, such as solar cell manufacturing and electric vehicle batteries. This expansion has prompted the industry to focus on decarbonization and responsible production practices.
At the recent Middle East Sulfur Conference (MEScon) 2024 in Abu Dhabi, business and technical leaders highlighted carbon dioxide (CO2) capture from sour gas treating/sulfur recovery and minimizing the CO2 footprint of the tail gas treating (TGT) process as top priorities in innovation.
Although Sulfur Recovery Units (SRUs) in sour gas treating facilities or refineries contribute minimally to global emissions, capturing CO2 from these facilities offers several benefits, according to Angie Slavens, Managing Director of UniverSUL, a consultancy specializing in sour hydrocarbons and sulfur. These benefits include reducing environmental impact, improving the quality of acid gas feeding the SRU for more efficient sulfur recovery, and supplying captured CO2 for Enhanced Oil Recovery (EOR).
UniverSUL, along with CRU, a global commodities business intelligence company, organized MEScon 2024. Slavens explained that capturing CO2 from the Acid Gas Removal Unit (AGRU) during sour gas processing is the most efficient method due to the high operating pressure, which enhances CO2 capture efficiency. This process typically emits less than 1 tonne of CO2 equivalent for every 10 tonnes of CO2 captured.
Alternative options include capturing CO2 from acid gas in the Acid Gas Enrichment Unit (AGEU) and downstream of the SRU/TGTU incinerator post-combustion, which are economically viable due to median CO2 partial pressures. However, capturing CO2 from SRU tail gas downstream of the low-pressure TGTU absorber poses greater challenges due to lower CO2 partial pressures, with equivalent CO2 emissions exceeding 5 tonnes for every 10 tonnes of CO2 captured, depending on the solvent selection and process scheme.
The industry is also exploring ways to minimize the CO2 footprint of TGT processes. While conventional Claus SRUs have a negative CO2 footprint due to heat recovery from the Claus reaction, existing TGT technologies can diminish these energy benefits. New solvents and technologies are being developed with lower energy requirements and smaller CO2 footprints. For instance, converting sulfur species in SRU tail gas to sulfuric acid could make the SRU/TGTU complex an even larger energy exporter.
Slavens emphasized that cost per tonne is not the only factor in evaluating CO2 capture economics. Capital cost and layout considerations are crucial in retrofit situations where CO2 capture equipment is added to an existing facility. A minimum CO2 recovery factor is typically specified to measure the percentage of CO2 that can be economically and feasibly captured. Feed and product CO2 quantities can be measured using standard gas metering instrumentation, while CO2 quality requirements depend on the end-use, with specifications aimed at protecting compression and pipeline equipment from corrosion.
Survey respondents also identified AI and machine learning as essential for enhancing operational efficiency and sustainability. The “Sulfur 4.0” session at MEScon 2024 showcased advancements in automation and digitalization for sulfur recovery, with presentations from industry leaders like ADNOC, Aramco, and BR&E. These advancements included using an AI-assisted Copilot for improving control room operator performance, enhancing SRU reaction furnace temperature monitoring through machine learning, and sustainability improvements via automated start-up of SRU-fired equipment.
As the sour gas and sulfur industry experiences growth, its commitment to energy transition through decarbonization and responsible production practices will be crucial for ensuring a sustainable future.