Effluent Treatment in a Gas-To-Liquid Plant
- Dennis Denney (JPT Senior Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- April 2012
- Document Type
- Journal Paper
- 112 - 115
- 2012. International Petroleum Technology Conference
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- 72 since 2007
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This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 14215, "A Novel Approach to Effluent Treatment in Gas-To-Liquid," by C.G. Enyi, M. Nagib, SPE, and G.G. Nasr, Salford University, prepared for the 2011 International Petroleum Technology Conference, Bangkok, Thailand, rescheduled to 7-9 February 2012. The paper has not been peer reviewed.
In a gas-to-liquid (GTL) plant, a large amount of reaction water is produced and various chemicals are used as intermediate treatment chemicals. The reaction water is contaminated by these chemicals. A laboratory-scale effluent-neutralization unit for pH control was designed and built to demonstrate the feasibility of the use of carbon dioxide (CO2) produced by reforming reactions in both the synthesis and the hydrogen-production units in the GTL plant for in-situ effluent treatment.
Deep saline formations appear to offer potential to store several hundred years’ worth of CO2 emissions. Wider international collaboration and consensus are needed to ensure the viability, availability, and permanence of CO2 storage. However, carbon capture/sequestration faces both technical and economic challenges. Therefore, there is the need to explore other methods to deal with CO2 emissions. Transformation to chemical feedstock such as methanol is a commercially proven technology; however, CO2 captured from furnace flue gas will not be economical for this purpose because of its low pressure. Compression is required before the CO2 could be processed into methanol.
Another process, the Sabatier reaction, converts CO2 to methane. This methanation process could prove to be less capital intensive, provided that reaction hydrogen is available from a low-cost source.
This work focused on the in-situ use of produced CO2 from the reforming and Fischer-Tropsch (F-T) reactions in a GTL plant for effluent treatment instead of the conventional use of sulfuric acid, which is not produced in the GTL-plant complex. Because the objective of this work is to reduce CO2 emissions, modifying the entire effluent-treatment system (e.g., corrugated-plate interceptor separators, aeration equipment, clarifiers, dissolved-air flotation separators, and chlorination and equalization units) will not be required. Only the neutralization unit, which controls the pH of effluent, will be modified.
GTL technology comprises a chemical conversion of natural gas to a stable liquid by means of the F-T process. This conversion makes it possible to obtain products that can be consumed directly as fuel (e.g., diesel, kerosene, and gasoline) or special products such as lubricants.
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