Economic Feasibility Analyses 3509 



28-6 $350,000— WOOD GASIFIER RETROFITTED TO 

 EXISTING GAS/OIL-FIRED BOILERS 



The Georgia Forestry Commission, the Georgia Institute of Technology, and 

 the Applied Engineering Company cooperated to retrofit a 19,000-pound/hour 

 gas/oil burner at the Northwest Georgia Regional Hospital in Rome, Ga. , with a 

 25-million-Btu/hour updraft wood gasification system fired with hardwood 

 chips. The gasifier design (fig. 28-7) is described in section 26-4. Consumption 

 of wood chips is projected to average 22,093 tons (green-weight basis) annually; 

 the wood is converted with 85-percent thermal efficiency to gas having a heating 

 value of 127 Btu/cu ft and constituents about as follows: 

 Constituent Percent 



Nitrogen 53.0 



Oxygen/argon 2.4 



Carbon dioxide 9.5 



Carbon monoxide 25.0 



Hydrogen 8.0 



Methane 1.8 



Other .3 



100.0 



Overall efficiency of the entire gasification system (fig. 28-7) is estimated at 70 

 percent. Computations by the authors indicate a yield of 5,500 to 6,500 pounds 

 of gas from one ovendry ton of chips. Capital cost of the retrofit system was 

 $350, (X)0 with expected life of 20 years. With 7,000 operating hours annually, a 

 wood cost of $15/green ton, and a net heat output of 6.02 million Btu/green ton 

 of wood, cost comparisons with operation on No. 6 fuel oil (table 28-2) indicate 

 annual savings of $272,095, indicating payback of the $350,000 investment in 

 1.3 years. 



Table 28-2. — Annual costs of retrofitted wood gasifier compared to existing system 

 fired with No. 6 fuel oil (Bulpitt et al. 1981) 



Retrofit Existing 



Item wood gas/oil 



gasifier furnace 



Dollars 



Annual cost of capital 59,034' 



Maintenance 10,500 2,250 



Operating costs of labor and electricity 48,290 30, 107 



Fuel 331,3952 668,9573 



Total annual cost 449,219 721,314 



'Total investment in system, $350,000. 

 ^Hardwood chips at $15/ton, green- weight basis. 

 ^No. 6 fuel oil at $26/barrel. 



^Abstracted from Bulpitt et al. (1981). 



