Scrubbing of HCl Gas from Synthesis Gas in a Multistage Dual-Flow Sieve Plate Wet Scrubber

Coal is a combustible substance composed of carbon along with several impurities like sulphur, chlorine, and nitrogen and metal compounds. These impurities get converted to gaseous species such as H2S, HCl and NH3 when this coal is processed. Therefore, removal of these impurities is essential to protect the energy production equipment and to meet environmental standards before entering into the atmosphere. During the gasification process, the chlorine present in the coal is volatilized to HCl or metal chlorides.

The chloride content is high in US coals with 0.01% to 0.5% and during coal gasification process these chlorides will produce HCl. In the gasification process, the chlorine content of coal volatilizes to metal chlorides or HCl. But major portion of chlorine is converted into HCl. Reports show that there is a wide variation in the HCl concentrations in synthesis gas streams. Bakker and Perkins  reported that the HCl concentration is five times higher in coal gas than in coal-fired boiler combustion gas stream.

The chlorine content of coal, the gasification temperature and the type of gasifier are the factors on which the HCl vapour concentration depends and the most reliable data was found from the fixed-bed gasifier operation at General Electric Corporate Research and Development at Schenectady, New York. At that facility, about 300 ppmv HCl vapour concentration was obtained using coal with 0.24 wt% chlorides. The concentrations of HCl are reported as high as 500 ppm in coal syngas from gasifier effluents. 

Read More...