CORROSION ASPECTS2
Gasification takes place at high temperatures, depending on the process, anywhere between about 900 and 1500°C. Processes have been developed with the capability of operating at pressures of over 100 bar, although commercial experience is limited to about 80 bar (oil) or 40 bar (coal). Other processes operate at atmospheric pressure. The synthesis gas produced contains C02, CO, H2, CH4, N2, H20, and almost invariably sulfur compounds, mostly H2S. This gas is usually cooled down to ambient temperatures, and in doing so the temperature range imposed on the containing equipment is very wide and includes sub-dewpoint temperatures. It is not surprising, therefore, that particular attention has to be paid to material selection in a potentially corrosive environment. Some of the corrosion mechanisms that can arise under these circumstances are well known from other circumstances. The purpose of this section is not to address these, however, but to highlight those potential problems that might be less familiar to those with little prior experience of gasification, and to point to suitable literature where more information may be obtained.