Document Type

Working Paper

Date of this Version

4-20-2018

Comments

Sour water is a waste product of various crude oil refining processes at refineries. Ammonia and hydrogen sulfide, the main contaminants of sour water, must be removed from the sour water before it can be discharged or used elsewhere in the refinery. Through a process known as stripping, the contaminants are transferred from the sour water to the gaseous stripping agent in a large stripping column containing trays or packing. The designs outlined in this report analyze the economic and environmental validity of using two alternative stripping agents, air and natural gas, compared to the industry incumbent, steam. The Net Present Value for a natural gas-fed stripper is -$15 MM over 19 years compared to -$16 MM for that of an air-fed stripper. One novel feature included in both designs is the option of recycling the extract stream to reduce NOx emissions in natural gas-fed burners. Careful analysis of the economic, environmental, and safety considerations of each of the two stripping agents reveals that the natural gas stripping process is economically and efficaciously superior, while the air stripping process is environmentally superior with less safety concerns. Therefore, it is recommended that management pursues both options as potentially viable replacements for traditional sour water stripping processes.

The analysis was performed assuming an average sour water flow rate of 37.5 gallons per minute and an average ammonia concentration of 1650 ppm in the sour water feed. The recommendation of pursuing natural gas and air equivalently as stripping agents is dependent on the assumed location of the refinery. Because environmental regulations for water and atmospheric discharge vary by region, a separate analysis of the validity of each alternative should be performed for stripping operations in different areas.

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Date Posted:20 April 2018