Energy Balance For The Second Underground Coal Gasification Experiment, Hanna, Wyoming

The second underground coal gasification experiment conducted by ERDA's Laramie Energy Research Center at a site near Hanna, Wyo., was completed on Jul. 30, 1976. During the experiment production reached 0.32 blm3/d (12 M cu ft/d) of 6.9 w/m3 gas (175 Btu per cu ft). Approximately 6100 tonnes (6700 tons) of coal were gasified during the experiment. Energy return ratios of 4.5 to 5.3, coal gas thermal efficiencies of 76 to 89%, and overall process efficiencies of 65 to 74% were achieved during the second Hanna experiment. This paper describes the experiment and the results obtained with emphasis given to the determination of the energy recovered relative to energy consumed in conducting the test. Data from this determination are compared with previously published data from the first test conducted at Hanna during 1973-74.