Conversion of an Oil/Gas-Fired Industrial Boiler to Fire Hogged Fuel

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distribution. The wood firing system should be able to tolerate a range of fuels from whole tree chips to planer shavings. Reliable and Safe Operation. The steam supply is key to the operation of the chemical process. While a stand-by boiler is available for emergencies, it is desirable to operate the wood firing system continuously except for a scheduled annual outage. No Ash Disposal Problems. The candidate boiler has no provision for ash disposal. The flat furnace bottom cannot be modified to form a hopper. Thus the wood firing system should provide for removal of most ash or char prior to the furnace. Alternately, ash and char must be kept in suspension and recovered in a dust collector. No Erosion Problems. The candidate boiler is designed with high gas velocities in the convective section. The boiler manufacturer has specified that velocities must be less than 100 ft/sec to avoid erosion if abrasive particles are present. This requirement would severely limit the maximum wood firing rate. Compatible with Boiler Systems. The wood firing system must be capable of operating automatically with only minimal supervision. If the boiler fan is used to supply combustion air, the firing system pressure requirements must be controllable; otherwise furnace pressure is limited to 10.0 in. H«0. Local Emission Requirements. The candidate boiler is located in a metropolitan area with stringent emissions regulations. The most difficult regulation to meet with a wood firing system would be the total particulate mass which must be less than 0.05 grains/scf. Note that the boiler is equipped with a cyclone and this may remove some of the particulate. Compatible with Space Requirements. The wood firing system must include a wood unloading facility, hoppers, conveyers, wood pre­paration equipment, the firing system and an ash disposal system. This may require considerable ingenuity since the existing space is quite limited. 28-8