Study of by-products and potential pollutants from high-temperature entrained-flow gasifiers. Final report

Effluents from a high temperature, high pressure, entrained flow gasifier were analyzed for possible inorganic and organic pollutants. Samples were taken from the cooled and water-scrubbed product gas stream, the scrubber effluent water, the gas evolved on depressurization of the scrubber water, and the particulate matter filtered from the scrubber water. The compositions of these samples were determined using the analytical techniques of gas chromatography/mass spectrometry, proton-induced x-ray emission spectroscopy, x-ray fluorescence spectroscopy, thermometric titrimetry, ion chromatography, and atomic absorption spectroscopy. In order to observe the effects of different reactor conditions on the amounts and types of pollutants produced, five process parameters were varied; coal type, coal feed rate, reactor pressure, oxygen/coal ratio, and steam/coal ratio. It can be concluded that: effluent streams from this type of gasifier are extremely clean when compared to other types of gasifiers; all of the nonvolatile organic compounds produced are quantitatively adsorbed by the particulate matter in the scrubber water; the only potential pollutants from the gasifier are the particulate matter and NH/sub 4//sup +/ in the scrubber water, the bottom ash/slag, and the H/sub 2/S and HCN in the product and flash gases; increasing the pressure and decreasing the O/sub 2//coal ratio tendedmore » to reduce pollutants in the effluents and increase coal conversion efficiency; flocculation is probably the best method of removing char or soot from the scrubber water; the ash slurry stream can be treated by thickening clarification of the solids and the removal of hydrogen sulfide from the liquid stream by the addition of a base such as sodium hydroxide; and acid gas pollutants, H/sub 2/S, HCN and SO/sub 2/, may be removed from the product gas and the scrubber flash gas using the commercial RECTISOL absorption process.« less