Demonstration of flue gas desulfurization process by catalytic oxidation to produce sulfuric acid

Abstract

Since coal and oil fired plants are one of the major sources of sulfur dioxide emission to the atmosphere, it has been required to develop desulfurization processes with a lower cost and a smaller energy consumption than the conventional wet limestone flue gas desulfurization processes (FGD).
The catalytic SOx oxidation process (CASOX Process) is an innovative flue gas desulfurizing process that demonstrates a high performance in desulfurizing sulfur dioxide from flue gas by a newly developed desulfurizing catalyst. The flue gas is desulfurized in passing through the catalytic layer when the sulfur dioxide is oxidized to dilute sulfuric acid on the surface of the catalyst with oxygen and water vapor in the flue gas. The surface of the activated carbon as a catalyst is treated to have water-repellency, so that the dilute sulfuric acid produced on the surface of the catalyst can be separated from the catalyst rapidly and continuously. This treatment made the catalyst possible to be operated without regeneration procedures , so it can be operated without alkaline.
Demonstration tests were conducted on the pilot plant installed at Toyama Shinko Power Plant of Hokuriku Electric Power Company in order mainly to confirm the practical application of this process to a coal fired power plant. Through the treatment of the flue gas from the coal fired power plant, CASOX Process maintained more than 95% of SO₂ removal rate and stable over 15,000h of desulfurization performance. The demonstration tests also revealed that CASOX Process has the following advantages. First, the process can reduce energy consumption compared with the conventional FGD process, because of the small number of the equipments, especially on the point that no large fans and circulation pumps are required. Second, the process can be easily operated and maintained because of its simple configuration. Third, this process can be operated without alkaline because sulfuric acid is produced as a by-product.
The first commercial plant of CASOX Process has been operated from April 2003 successfully.