Activated carbon production at biomass-fueled steam/electric power plants
A method and apparatus for producing activated carbon from biomass or other solid carbonaceous feed within a housing containing boiler components, by spatial separation of drying, pyrolysis and activation zones as the feed is conveyed across the bottom of the housing, such that the thermal requirements for drying, pyrolysis, and activation of the solid carbonaceous feed occur by direct radiation from the combustion flame located above the drying, pyrolysis and activation zones. The balance of the heat not required for drying, pyrolysis, and activation is used to vaporize and superheat steam as part of a conventional steam/electric power plant.
1. Apparatus which comprises:
a housing;
a boiler that includes means for heating water to produce steam and a single combustion zone, said combustion zone being disposed below said means for heating water to produce steam within said housing;
means for injecting air and/or oxygen into said combustion zone;
means for delivering steam from said boiler to an associated turbine;
means for moving a carbonaceous feed into said housing and activated carbon product out of said housing and located below said single combustion zone whereby said carbonaceous feed is sequentially dried, pyrolyzed, and activated by radiant heat from said combustion zone, and pyrolysis and activation product gases and vaporized liquids flow unrestricted upwards into said combustion zone resulting in said pyrolysis and activation product gases and vaporized liquids providing fuel for combustion in said combustion zone;
means to minimize the ingress of air and egress of gases and vapors from said housing by delivering inert gases below said means for moving carbonaceous feed, said inert gases flowing upwards through said carbonaceous feed in the areas where drying and pyrolysis occurs;
means for delivering steam or other gas with mild oxidative properties below said means for moving carbonaceous feed, said steam or other gases with mild oxidative properties flowing upwards through said carbonaceous feed in the area where activation occurs.
2. The apparatus as described in claim 1 further including an emissive perforated plate disposed under said single combustion zone and above said means for moving carbonaceous feed.
3. The apparatus as described in claim 1 wherein said means for moving carbonaceous feed is a horizontal conveyance apparatus.
4. The apparatus as described in claim 3 wherein said horizontal conveyance apparatus conveys said carbonaceous feed at a rate of speed that results in a residence time of said carbonaceous feed within said housing of at least 45 minutes.
5. The apparatus as described in claim 3 wherein said horizontal conveyance apparatus is obliquely disposed with respect to a horizontal plane.
6. The apparatus as described in claim 3 wherein said horizontal conveyance apparatus is selected from the group consisting of reciprocating grate bars, vibrating grates, underfed stokers, un-enclosed screw augers, and traveling grates.