Discussion on SO2 emission reduction technology during shutdown of sulfur recovery unit

Author of the article:QU Yang, HU Chao, CHEN Hong, XU Jiale, TANG Xingbo, XU Fei

Author's Workplace：PetroChina Southwest Oil & Gasfield Company. Natural Gas Purification Plant, Chongqing, 400021, China

Key Words：Sulfur recovery; Shutdown period; SO2; Emission reduction

Abstract：In a natural gas purification plant, during shutdown period of the sulfur recovery unit, the concentration of SO2 in tail gas increases and fluctuates a lot. The causes of the above problem are: 1) in the case of traditional process of fuel gas combustion to remove sulfur, the flow of hot inert gas is small; hence the concentration of SO2 in tail gas during the desulfurization period fluctuates significantly; 2) the hot nitrogen desulfurization process has significant limitation; 3) the alkaline flue gas desulfurization process has difficulties in its sewage treatment. This paper proposes SO2 reduction solutions during sulfur recovery unit shutdown period as follows: 1) control the fuel gas and combustion air mixing ratio strictly; 2)use higher nitrogen purging rate when there is plenty of nitrogen; 3) make use of existing tail gas processing unit, add alkali to absorb SO2; 4)recycle and reuse exhaust gas. The above proposals from the research study can reduce the risk of excessively high SO2 concentration in exhaust gas from the natural gas purification plant during shutdown period of the sulfur recovery unit, and ensure that the SO2 concentration of tail gas meets the national environmental protection requirements during such period.