Development of Mercury and Hydrogen Chloride Emission Monitors for Coal Gasifiers

The gas conditioning issues involved with coal gasification streams are very complex and do not have simple solutions. This is particularly true in view of the fact that the gas conditioning system must deal with tars, high moisture contents, and problems with NH{sub 3} without affecting low ppb levels of Hg, low levels (low ppm or less) of HCl, or the successful operation of conditioner components and analytical systems. Those issues are far from trivial. Trying to develop a non-chemical system for gas conditioning was very ambitious in view of the difficult sampling environment and unique problems associated with coal gasification streams. Although a great deal was learned regarding calibration, sample transport, instrumentation options, gas stream conditioning, and CEM design options, some challenging issues still remain. Sample transport is one area that is often not adequately considered. Because of the gas stream composition and elevated temperatures involved, special attention will need to be given to the choice of materials for the sample line and other plumbing components. When using gas stream oxidation, there will be sample transport regions under oxidizing as well as reducing conditions, and each of those regions will require different materials of construction for sample transport. The catalytic oxidation approach worked well for removal of tars and NH{sub 3} on a short term basis, but durability issues related to using the catalyst tube during extended testing periods still require study