An Underground Coal Gasification Experiment, Hanna, Wyoming

Abstract

In the fall of 1972, the Bureau of Mines began an experiment to investigate the technologic, economic, and environmental considerations of underground gasification of a western subbituminous coal. The gasification site is near the town of Hanna, Wyoming, approximately 70 miles northwest of Laramie. The test results indicate that gas volumes and gas heating values have fluctuated over a wide range depending on operating conditions. The ranges have been from 50,000 to over three million standard cubic feet per day of produced gas with a composite heating value from 30 to 465 Btu per standard cubic foot. Even though these fluctuations have occurred, a semi-steady state condition existed for a six-month period. From September 1973 through February 1974 a low Btu gas averaging about 130 Btu per standard cubic foot was produced at an average rate of 1.6 million standard cubic feet per day. A material balance made during this period indicated:There was little or no underground gas leakage from the site;About 80 barrels of formation water were consumed each day;Between 13 and 46 tons of dry coal were affected each day depending on the assumptions made; andFrom 23 to 65 percent of the energy of the coal being subjected to carbonization and/or gasification is being recovered. If the gas can be sustained at this relatively steady Btu content and production rate, it could be used directly to fire a boiler or to fuel a combined gas turbine-steam turbine cycle in electric power stations. The average amount of energy power stations. The average amount of energy produced from this small field test would have produced from this small field test would have been adequate to supply fuel for about a one megawatt power station. Introduction Interest in underground coal gasification has been stimulated recently by the Nation's growing energy demand. Its potential for generating plentiful supplies of fuel gas without the environmental disturbance of surface mining and without exposing workers to the hazards of underground coal mining is especially promising. While not expected to replace coal mining, it offers an alternative method of bringing the energy value of the coal to the surface. If feasible, this clean energy form could supplement the gas supply used to produce electricity, particularly in the industrial sector. It may also be possible to upgrade the gas to pipeline quality or to produce methanol as a possible substitute fuel for gasoline. The role of oil and natural gas as sources of energy is almost as well known as the shortage of these vital fuels. More than three-fourths of the energy used in the United States in 1972 was derived from these sources. Coal, the most abundant fossil fuel, supplied only 17 percent of the Nation's energy needs in that year.

Innovative thermodynamic underground coal gasification model for coupled synthesis gas quality and tar production analyses

“…2), the relative error range for the main gas single compounds ranges between 4.32 and 9.95% [53], overall indicating quite good agreement, keeping in mind that this is only a snapshot of a reported average gas composition. Alongside, the relative error for the synthesis gas LHV comparison was found to be relatively low (6.60%) [55], probably slightly overestimated as a result of the higher tar and H 2 production prognosis.…”

“…Figs. 2 and 3 compare the dry synthesis gas composition, its lower heating value, and total tar production regarding the main source process of pyrolysis and expected mixed synthesis gas yields [26,47,[53][54][55]. In context of the syngas heating value analysis here, we used the standard internal Aspen Plus® software subroutine (Refsys correlation manager, LHV-0).…”

“…An overview of selected model components, including the principal tar pollutant set balanced within the model is outlined in Table 1. Relevant information on parameterization for specific modules is provided in Table 2 [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58]. In view of essential model validation test data only few precise background data on former UCG field trials are available to the public.…”

“…In view of essential model validation test data only few precise background data on former UCG field trials are available to the public. As a starting point, here we used data related to the early North American trials Hanna I and Centralia PSC [43][44][45][46][47][53][54][55][56][57].…”

Underground coal gasification

“…Over a 4 mo period, an average yield of 1 170 kcal/m3 was produced from a two-hole (inlet/outlet) system. The linked vertical well method was used, and forward burning was found unworkable without prior backward buming (Schrider and Pasini, 1973;Schrider et al, 1974;Campbell et al, 1974). Later analysis of this first test has shown that the linkage path was not performed at the bottom of the seam, which in turn gave the inconsistent product gas composition.…”