Effects of Oxygen Enrichment on Sulfur Recovery Efficiency and Contaminant Destruction in Claus Process

Abstract

Due to the depletion of light sweet crude fields, the recent discovery of new sour fields, and the advent of stringent environmental regulations, sulfur recovery units (SRUs) are now desired to work with high sulfur recovery efficiency (near 99.9%) and high processing capacity. In Claus process, an H2S-laden acid gas feed is burnt with air in a furnace, and its effluent gases are further processed in subsequent catalytic reactors to achieve a nearly complete H2S conversion. The associated contaminants of acid gas feed such as benzene, toluene, ethylbenzene, and xylene (BTEX) can increase the process's operational cost through catalyst deactivation and high fuel gas consumption and impact the sulfur recovery efficiency (SRE) and toxic gases emissions. In this work, the effectiveness of enriching inlet feed air with oxygen on the process performance has been studied by utilizing a detailed reaction mechanism for SRU feed combustion and pyrolysis to quantify its effect on toxic gases emissions, BTEX destruction, SRE, and fuel gas consumption in the incinerator. The results show that, upon increasing the oxygen concentration in air, BTEX concentration decreased substantially due to the enhancement in the radical pool, SO2 emissions increased, and CO2 emissions and fuel gas consumption in the incinerator decreased. Interestingly, oxygen enrichment increased the CO emission as the furnace temperatures increased up to 1350°C, but it decreased with further increase in the furnace temperature at higher oxygen concentrations. This decrease in CO emissions at high oxygen concentrations (accompanied with higher furnace temperatures) was found to be occurring due to its lower production in the furnace and its faster conversion to COS and CO2 in the waste heat boiler. The results clearly showed that higher oxygen concentration in air can be utilized to decrease fuel gas consumption and CO and CO2 emissions in SRU, if an economic source of it is available.

Date of Award	May 2019
Original language	American English
Supervisor	Abhijeet Raj (Supervisor)