Emission control solutions for biomass and coal combustion sector - Energy - Bioenergy
For particulate matter (PM) emission control in high temperature exhaust streams, such as those from biomass or coal boilers and heaters, common dedusters such as cyclones and multicyclones are not able to comply with current emission limits. This is mainly due to their low efficiency, particularly for small particles (less than 10µm). In order to meet emission limits this usually requires an additional investment in a final stage deduster. Bag filters (BF) are very efficient dedusters. They can also be very high maintenance requiring regular cleaning and new filter elements. Biomass and coal boilers frequently release burning particles that damage filter elements and result in immediate increases in emissions.
Solving this problem means spending money and production downtime. Electrostatic Precipitators (ESPs) are very effective for a given range of dust resistivity. However, efficiency frequently drops outside this range as a consequence of temperature changes.
The cost of retrofitting an ESP or process changes are out of reach for many companies. Venturi Scrubbers are a good alternative for end stage dedusters if the infrastructure to treat the liquid effluent already in place. If not the cost of secondary wet pollution restricts its usage.
Clients' needs include a highly efficient final dedusting system at a reasonable price, robust enough to operate for several years without significant maintenance or operating costs and avoiding production downtime.
The general arrangement of a biomass coal combustion plant is the use of a pre-separator to reduce the concentration of particles after the boiler, especially the coarser dust which is richer in Silica (SiO2). This is the case of several types of biomass, such as Eucalyptus, Palm Shell and Fibers, Empty Fruit Bunch, Rice Husk and all types of coal.
The Median Volume Diameter (MVD) of the fly ash coming directly from the furnace is typically 11µm with 8% under 1µm. The MVD of the particles escaping the pre-separator is usually 6 to 8µm.
The end stage deduster (either a Bag Filter, a ESP, a Venturi Scrubber, a Hurricaneor aReCyclone System), is placed downstream of the pre-separator.