Energy, fuels, and chemicals 3205 



the immediate (sensible) heat of the gas can be utilized (Love and Overend 

 1978). Such on-site utilization is best for low Btu gas since the gas cannot be 

 stored effectively, and its low Btu content makes transport economically unat- 

 tractive. After modification of burner nozzles, low Btu gas can be burned in 

 standard natural gas and oil furnaces. 



Such gasifier systems have advantages over solid- wood fueled furnaces. Ash 

 and carbon residues remain in the gasifier; the furnace is subjected only to 

 producer gas, a relatively clean fuel. While some tars, oils, and particulates may 

 be carried over with the producer gas, in most cases no pollution controls are 

 needed on the furnace.'^ 



A portable gasifier developed by the University of California was successfully 

 tested using wood as a fuel at the California State printing plant where the low 

 Btu producer gas was burned in one of the plant's boilers (table 26-12). A 

 feasibility analysis indicated that no major technical barrier exists to commer- 

 cialization of gasifiers that produce low Btu gas for furnace boiler fuel." Emis- 

 sions were within acceptable standards. The costs of using the gasifier system 

 over 20 years would be competitive with the cost of using natural gas (in 

 California) assuming price increases at the rate of inflation. 



Table 26-12. — Input and output for one hour of prototype gasifier operation^ 

 Input Output 



.75 ton of wood" 10 million Btu of gas 



1 gallon of gasoline 100 lb of char 



5 Kw of electricity 1 quart of tar 



SO^ - negligible 



NO^ - 129 ppm 



particulates - 0.8 grams per standard cubic foot 



'Data from California State Energy Commission, "Commercial Biomasss Gasifier at State Central 

 Heating and Cooling Plant", Feasibility Study prepared by Fuels Office, Alternatives Division, 

 April 1978, 63 p. 



-Tests were based on kiln-dry wood, demolition wood, and pelletized sawdust; average moisture 

 content was probably about 10 percent of ovendry weight. 



In another demonstration, Applied Engineering Company, Orangeburg, 

 S.C., designed, constructed, and in February 1981 began testing a wood gasifier 

 (fig. 28-10) retrofitted to a 19,000 Ib/hr watertube boiler originally equipped to 

 burn oil or gas. The work was done under contract by the Georgia Forestry 

 Commission and installation was made at the Northwest Regional Hospital at 

 Rome, Georgia. See section 28-6 for an economic analysis of the retrofit. 



The gasifier reactor vessel is cylindrical, insulated with firebrick, and en- 

 closed in a carbon-steel shell. Air is injected at the bottom of the reactor and fuel 

 added at the top. Gases produced exit at the top and ash is discharged from the 

 bottom. The grate area, located above the ash hoppers, is water cooled. Gas 



G.D. Voss and V.A. Ganger. Gasification of wood residues. Paper presented at the For. Prod. 

 Res. Soc. Annu. Meet. (Denver, Colo., July 1977). 13 p. 



