Ceramic Filtration for Incinerators

Incineration processes produce hot effluent gases contaminated with particles and/or other pollutants. These gases require treatment before they can be safely released to the atmosphere. The use of ceramic filters enables the engineer to choose the temperature at which the particulate removal operation is performed. This is important for several reasons:

• Dioxin Reformation. Filtration at high temperatures, >400 degC, removes nucleation sites so that reformation of dioxins does not take place when or if the gas cools.
• Dry scrubbing. The acid gas removal efficiency when using sodium bicarbonate or hydrated lime in a  dry system is highly dependent on the reaction temperature.
• Acid Gas Scrubbing. Both wet and dry scrubbers operate more efficiently and reliably if the gases they are treating do not contain suspended solids.
• Vapour Condensation. Many emissions contain vapours, such as sulphur oxides, that cause serious corrosion when they condense. Ceramic filtration enables the gas temperature to be maintained well above the dewpoint right the way through the plant.
• Plume Avoidance. Gas filtration and treatment at high temperatures mean that the gas can be discharged to atmosphere at a temperature sufficiently high that a plume does not form.
• Heat Recovery. Heat exchangers operate more reliably and effectively if the gas does not contain suspended particulates.
• Catalyst Operation. Catalysts used, for instance for VOC removal or SO2 to SO3 conversion, operate at temperatures of ca. 400 degC and are quickly poisoned by fine particulates.
• No Dilution Air. The conventional method of cooling gases to bag filter temperatures is by the addition of dilution air. This increases the volume of gas that must be filtered.
• Resistant to Process Upsets. Processes do not always run exactly as planned. The stable nature of ceramic filters allows them to withstand temperature excursions, sparks and incandescent particles, and even fires inside the filter vessel without requiring expensive shutdown and filter replacement.
• Resistant to Corrosion. The alumino-silicate composition of ceramic filter elements renders them impervious to attack by almost all the corrosive agents encountered in emissions from combustion processes. Acid gases have no effect on the elements, even at elevated temperatures

Caldo ceramic filters have been used on a range of incineration processes and photographs of some are viewable on the Incineration Photos page.

The Powerpoint presentation 'Hot Gas Filters for Control of Emissions to Atmosphere' covers many of the above topics and can be downloaded as a 291 kB pdf file..