Incineration poisonous gases

In catalytic incineration, there are limitations concerning the effluent streams to be treated. Waste gases with organic compound contents higher than 20% of LET (lower explosion limit) are not suitable, as the heat content released in the oxidation process increases the catalyst bed temperature above 650 °C. This is normally the maximum permissible temperature to which a catalyst bed can be continuously exposed. The problem is solved by dilution-, this method increases the furnace volume and hence the investment and operation costs. Concentrations between 2% and 20% of LET are optimal, The catalytic incinerator is not recommended without prefiltration for waste gases containing particulate matter or liquids which cannot be vaporized. The waste gas must not contain catalyst poisons, such as phosphorus, arsenic, antimony, lead, zinc, mercury, tin, sulfur, or iron oxide.(see Table 1.3.111... 

Up to now a lot of attention has been paid to improving the performance of SCR catalysts with respect to making them more resistant to the poisonous compounds present in the flue gases, mainly SOx and As, which are results of burning with coal, oil and gas (ref. 5 and 6). At the same time relatively little information has been presented on the poisoning effect of flue gases from municipal waste incinerators, on the SCR-type de-NOx catalysts. 

For NGL plants, emissions usually come from gas sweetening units when acid waste gas is burned or incinerated. Most frequently, the acid waste gas is used as a feedstock in sulphur recovery units or in sulphuric acid plants. While flaring is often expected in NGL plants, the major poison and pollutant of concern is S02- Most plants employ elevated smokeless flares or gas incinerators for combustion of all waste gas constituent, including tail gas incinerator in which H2S is oxidized to SO2 (Berkel, 2000) [7]. Such practices are not sustainable. CP can be implemented to reduce and/or eliminate gas flaring or incinerations beyond acceptable level as stipulated by local environment authorities. 

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