A real options approach for cost benefits assessment of power generation from underground coal gasification with CCS

Global and micro/macro structural models simulating the Longwall generator concept for underground coal gasification (UCG) are formulated for several geometric and loading conditions. Dynamic thermal and stress response solutions are computed for axisymmetric boundary value problems represented by a stationary circular cavity model and an expanding radially propagating circular cavity. Static thermoelastic response solutions are presented for circular and elliptical cylindrical presented for circular and elliptical cylindrical cavities in a homogeneous, isotropic medium and layered media. Considerations pertaining to roof collapse and surface subsidence are discussed. The micro/macro modeling investigations include thermorheological representation of Pittsburgh coal at elevated temperature and studies on thermal crack propagation of coal fissures. Finally, the relevance of stress and temperature profiles, fracture permeabilities, and fissure response is discussed in relation to the propagation and stability of the UCG process. Introduction Fossil fuels are currently the main energy resource for the U.S. with coal reserve estimates ranging from 3 to 4 trillion tons. Only one-sixth of this coal can be extracted by state-of-the-art mining techniques. It is anticipated that about one-third of the U.S. total coal energy reserves, particularly thin coal beds and thick-seam deep coal, can be recovered by underground coal gasification (UCG). This process entails ignition of a coal seam and circulation of gas through a controlled path. The resulting chemical reactions produce a gas with calorific value, depending on several process parameters and variables. Their optimization parameters and variables. Their optimization requires sophisticated analytical simulations of the structural, heat transfer, fluid flow, and reaction kinetics aspects along with controlled laboratory experiments and field tests. Descriptions and appraisals of various underground coal pregasification schemes and gasification processes mad a discussion of significant problems, processes mad a discussion of significant problems, such as roof collapse, gas leakage, water control, and surface subsidence, etc., have been given in a detailed report by Arthur D. Little, Inc.. Reports on UCG experiments in the Soviet Union, Great Britian, and other countries have been summarized in excellent monographs. The outlook for UCG in the U.S. was discussed recently at the First Annual UCG Symposium conducted by the Laramie Energy Research Center in Wyo. It appears that several candidate concepts and solutions exist, depending (on the type of coal, coal seam thickness, overburden, and environmental requirements. The concepts currently being investigated by ERDA's research centers and laboratories includethe vertical well to well linking experiments at Hanna, Wyo., for medium seams (Laramie Energy Research Center),the packed-bed concept for thick coal seams (Lawrence Livermore Laboratory), andthe Longwall generator concept for thin seams (Morgantown Energy Research Center). This paper presents results obtained from analytical structural and thermal simulations associated moth the Longwall generator UCG concept. Temperature and stress response solutions are presented for different boundary value problem representations. The results of this study provide fundamental insight to the interpretation of UCG global and micro/macro mechanisms. UCG LONGWALL GENERATOR CONCEPT AND MECHANISMS Morgantown Energy Research Center presently is developing the Longwall generator concept to gasify thin-seam eastern coals (Fig. 1). In this concept, directional holes (6-in. diameter) are drilled from the ground surface with horizontal holes, 500 ft in length, entering through the 6-ft-thick coal seam (1,000-ft overburden) and returning vertically back to the coal surface. The gasification reaction zone propagates horizontally in the coal propagates horizontally in the coal maximum-permeability direction between the parallel horizontal holes drilled approximately in the coal butt-cleat direction. JPT P. 413

Underground Gasification for Unrecoverable East Appalachian Coals

The underground gasification of coal and lignite is of interest when traditional coal extraction is impossible or unprofitable and also with increasing demand for thermal and/or electric power. In the Soviet Union, at six industrial Podzemgaz stations, beginning in the 1930s, more than 15 million t of coal was processed to obtain more than 50 billion m3 of gas. The South Abinsk station operated from 1955 to 1996, while the Angren station has been operating since 1963. Research on the underground gasification of coal has been largely theoretical, without close connection to industrial practice, and the results are based on mathematical modeling and data from 50–70 years ago. Obviously, Russia’s leading position in the underground gasification of coal has been lost. Russia now lags a number of countries that are making significant investments in the process. Note that, in Russia, despite the obvious benefits of underground gasification of coal, interest in the process has waned, on account of its significant deficiencies: the possibility of gas filtration to the surface; insufficient controllability of coal-bed preparation and thermal processing; the relatively low heat of combustion of the gas produced; and considerable losses of gas and coal underground. Note also the environmental impact of the underground gasification of coal, associated with the deformation of rock, its thermal, chemical, and hydrogeological changes, increase in its temperature, and active chemical pollution of groundwater. An obstacle to the adoption of the underground gasification of coal is the lack of clear ideas regarding the preparation and use of fuel gas. Recommendations for improving the process focus on the design of the underground gas generator and the gasification of the coal bed, without addressing the technology of the underground system, whose cost accounts for ~75% of the total equipment costs. The method proposed in the present work for the preparation of fuel gas from coal challenges the notion that the gas produced in underground gasification of coal should be divided into two products: gas and the tar (hydrocarbons) that forms in the preparation of the gas for combustion. If the specified temperatures are maintained, no condensation of hydrocarbons in the equipment and gas lines is observed, and dry dust removal from the gas may be employed, without complex processing of wastewater and of explosive and toxic materials. That significantly improves the economic and environmental characteristics of the process, Analysis of the results shows that the proposed approach to purifying the fuel gas produced by underground gasification of coal and lignite reduces capital costs in construction of the system by almost half; and the costs of gas production by a factor of 1.7. The time to recoup the initial investment is shortened by 41%; the yield of thermal energy is increased by 10.5%; and annual power output is increased by 151296 MW-h.

Underground Coal Gasification (UCG) is expected to be game changer for nation like ours that requires large amounts of energy but have few natural resources other than coal. ONGC, being an integrated energy company and due to synergy between E & P operations and UCG, envisaged opportunities in UCG business. Its first campaign on UCG started in 1980s. With its initiative, a National Committee for UCG was constituted with representatives from Ministry of Petroleum, Dept. of Coal, CSIR, CMPDIL, State of Gujarat and ONGC for experimenting a pilot. It was decided in mid-1986 to carry out a UCG pilot in Sobhasan area of Mehsana district which was to be funded by OIDB. Two information wells were drilled to generate geological, geophysical, geo-hydrological data and core/coal samples. 3-D seismic survey data of Mehsana area was processed and interpreted and geological model was prepared. Basic designing of pilot project, drilling and completion, strategy of process wells and designing of surface facilities were carried out. The project could not be pursued further due to escalation in cost and contractual difficulty with design consultant. ONGC second UCG campaign commenced with signing of an agreement of collaboration (AOC) with Skochinsky Institute of Mining (SIM), Russia on 25th November 2004 for Underground Coal Gasification (UCG). In parallel, MOUs were signed with major coal and power companies, namely, Gujarat Industries Power Company Ltd (GIPCL), Gujarat Mineral Development Corporation Ltd (GMDC), Coal India Ltd (CIL), Singareni Colliery Company Ltd (SCCL) and NLC India Ltd. Under the AOC, suitability study was carried out for different sites belonging to MOU companies. Only Vastan mine block, Nani Naroli, Surat, Gujarat was found to be suitable for UCG. Therefore, subsequent stages of detailed characterization & pilot layout, detailed engineering design were taken up for Vastan site. After enormous efforts for quite long since 2006, in the absence of UCG policy with Ministry of Coal (MoC), MoC finally allotted in-principle Vastan Lignite block to GIPCL in Aug. 2015. The project was to be carried out through a joint venture between ONGC and GIPCL. Unfortunately, efforts lacking sincerity were made by GIPCL for JV. MOC also did not bother adequately to monitor development of JV between ONGC and GIPCL. And finally, GIPCL citing the company to be small sized and it being without any experience on UCG, withdrew from the project in Dec. 2016. Now the block allocation process for the Vastan will have to be initiated afresh by MOC. The future of ONGC yet another UCG campaign seems to have once again hanged in balance. In view of the association with UCG for the decade and based on the feedback from the world-wide status of the technology, the author tries to make important suggestions in the paper for expeditious and efficient implementation of UCG technology in the country.

The unconventional use of coal to supplement Natural Gas (NG) in the power and chemical industry makes Underground Coal Gasification (UCG) an important technology in economically producing unconventional gas. Present day exploration and production technologies pave the way "from a potential to actual production". A 3D seismic survey has been applied in Southern Hungary for the site selection of UCG resource blocks, as well as in the design of the most optimal exploration drilling program. The latter exploration techniques directional drilled injection and production wells are planned in the coal seams to sustain the burning front. Wildhorse UCG Kft is a pioneer in the design and introduction of the environmentally friendly coal based syngas for electric power generation in East-Central European countries. Additionally the syngas can be utilised to supplement national gas supplies as alternative fuel gas. In this presentation the role of 3D seismic is discussed in defining the "Mecseknádasd UCG project". Wildhorse UCG Kft completed 3D seismic measurements in April and May of 2011 in the Mecseknádasd UCG project area. The goal of the seismic measurements is to image and clarify the structural conditions and to reveal faults and other discontinuities in the coal formation explored previously by historic deep drilling in the area. The processing and interpretation of the survey results have been performed together by GEOMEGA Kft and Wildhorse UCG Kft and the presentation covers the complete survey results of the Mecseknádasd UCG exploration project: –Newly processed results of historical boreholes–Results of the seismic survey–Geological and geophysical results of new boreholes–Possibilities for upgrading the geological model with integrated interpretation by using the available geophysical data (seismic, new boreholes, historic boreholes)–The possibilities for the application of 3D seismic survey in the design process of the UCG technology and to monitor the UCG engineering process

Underground coal gasification: From fundamentals to applications

Exergy analysis in the assessment of hydrogen production from UCG

The Lawrence Livermore Laboratory (LLL) carried out two underground coal gasification (UCG) experiments at its Hoe Creek site in Northeastern Wyoming. We are conducting environmental studies in conjunction with these UCG experiments, including an investigation of changes in local ground-water quality. Such changes are a consequence of the residual reaction products coal ash, char, some of the coal tars, and roughly 10% of the product gases - which remain underground after gasification. When ground water returns to the gasification zone, leaching and dissolution processes lead to the formation of a plume of contaminated ground water, which begins to move through the coal seam. In addition, fissuring and roof collapse may destroy the integrity of the underground "reaction vessel" permitting contaminants to escape to the surface permitting contaminants to escape to the surface or into overlying aquifers. Our field investigations include ground-water quality monitoring near the UCG experiments, geotechnical measurements of ground deformations, and Post-burn coring. Limited water quality analysis is performed in the field, and more extensive analysis, including GC-MS, is carried out at LLL and U.S. Geological Survey laboratories. The field program is augmented by laboratory measurements and program is augmented by laboratory measurements and modeling studies. We have monitored ground-water quality in wells near the first LLL experiment for a period of 2 years following gasification. A large number of contaminants were found in wells located up to 100 ft (30 m) from the burn zone, but concentrations have decreased substantially as a result of sorption by the coal. During the second gasification experiment (Hoe Creek II), roof collapse and the inadvertent gasification of an overlying coal seam caused the interconnection of three aquifers, including the two gasified coal seams. We have measured the resulting changes in local hydrology and in the dispersal of reaction-product contaminants. Introduction The conversion of coal into combustible gases, as a source for synthetic fuels, promises to become an important method of coal utilization. If this conversion is carried out with the coal in place underground - in situ gasification, or UCG (Underground Coal Gasification) - additional economic and environmental advantages may be realized. For example, UCG may make the recovery of deep coals economically attractive, and it can be accomplished without the need to expose workers to the hazards of underground mining operations. Furthermore, the U. S. coal resource that is suitable for UCG, and not economical to strip or deep mine, has been estimated at nearly 2 trillion tons. The exploration and assessment of this prospective technology must include a critical investigation of potential environmental problems, together with potential environmental problems, together with efforts to identify effective environmental controls. We are attempting to explore some of the environmental implications of UCG - particularly, ground-water effects - in parallel with UCG process investigations, so that significant concerns process investigations, so that significant concerns can be addressed in a timely manner. Although underground coal gasification generally involves a complex series of chemical reactions, it can be simply characterized as the heating of coal in the presence of gasifying agents such as oxygen and steam. Some of the coal is burned to provide heat to drive the gasification reactions. In the simplest form of UCG, two or more process wells drilled into the coal seam are used, after the coal is ignited, to inject air or other gasifying agents and to withdraw the resulting combustible gas mixture (Figure 1). In most cases, the coal's permeability must be enhanced, before gasification, along a path connecting the process wells. (The need to achieve this preliminary connection reliably and economically represents an important current challenge in the development of a practicable UCG technology.)

Outlook for the coal industry and new coal production technologies

Enjoying the twelfth largest coal reserve in the world, only 1% of Iran’s energy consumption basket is supplied by coal. In the recent decade, new technologies that produce low-cost and clean energy from coal have received much attention. One of these methods is underground coal gasification (UCG). The UCG has a potential for converting the world’s coal resources into energy, liquid fuels, and chemicals. For extraction of this valuable energy, firstly, the best site for UCG should be selected to minimize the implementation complications and to distribute this energy source properly in the country. UCG site selection is affected by many uncertainties including environmental, economic, and operational parameters. Therefore, it is important to use methods capable of taking into account the uncertainty of various parameters in the site selection. In this study, Z-numbers which are a new generation of fuzzy numbers are used to overcome this issue in suitable site selection for the UCG method. Technical considerations in UCG site selection consist of coal properties, surrounding rock properties, groundwater, and surface infrastructures of the region. In this paper, first, 15 criteria influencing UCG method and four available alternatives (four coal mines in Iran) are considered. Then, by using the Z-AHP method, which is a combination of Z-numbers and conventional analytical hierarchy process (AHP), the suitable mine site for UCG is determined. Based on the results, the alternative mine named Mazino is selected as the best place for UCG site with a final weight of 0.3713. The comparison of final weights of criteria also illustrates that the two criteria of “existence of fault” (C11) and “permeability of coal seam and overburden” (C9) are the most important parameters in UCG site selection. The Z-AHP method has the capability to make an appropriate decision in the existence of experts’ disagreement or lack of experts’ confidence.

Techno-economic assessment of hydrogen production from underground coal gasification (UCG) in Western Canada with carbon capture and sequestration (CCS) for upgrading bitumen from oil sands

Life cycle environmental impact assessment of coupled underground coal gasification and CO2 capture and storage: Alternative end uses for the UCG product gases

Underground coal gasification (UCG) is an advancing technology that is receiving considerable global attention as an economic and environmentally friendly alternative for exploitation of coal deposits. UCG has the potential to decrease greenhouse gas emissions (GHG) during the development and utilization of coal resources. In this paper, the life cycle of UCG from in situ coal gasification to utilization for electricity generation is analyzed and compared with coal extraction through conventional coal mining and utilization in power plants. Four life cycle assessment models have been developed and analyzed to compare (greenhouse gas) GHG emissions of coal mining, coal gasification and power generation through conventional pulverized coal fired power plants (PCC), supercritical coal fired (SCPC) power plants, integrated gasification combined cycle plants for coal (Coal-IGCC), and combined cycle gas turbine plants for UCG (UCG-CCGT). The analysis shows that UCG is comparable to these latest technologies and in fact, the GHG emissions from UCG are about 28 % less than the conventional PCC plant. When combined with the economic superiority, UCG has a clear advantage over competing technologies. The comparison also shows that there is considerable reduction in the GHG emissions with the development of technology and improvements in generation efficiencies.

A permeation theory of in-situ coal gasification is developed, and a mathematical model is derived for the process. Predicted gas compositions, gas flow rates, and temperature profiles are in good agreement with field test data. For example, experimental gas compositions deviate no more than 3 to 4 mol% from calculated values. On the average, agreement is much better. The major purpose of the permeation theory is to provide a basis for quantitative understanding of in-situ coal gasification and to lead to important general conclusions concerning the nature of the process. The well instrumented Hanna 2, Phase 2 test was essential in providing needed Phase 2 test was essential in providing needed information to confirm the theoretical conclusions. This test was conducted near Hanna, WY, during 1976 and was the best instrumented and most successful held test ever conducted up to that time. PART 1: DEVELOPMENT OF THEORY PART 1: DEVELOPMENT OF THEORY The dilemma of rapidly decreasing reserves of natural gas in the U. S. and the need for a clean, easily transported fuel has spurred much interest in the production of gas from coal. One of the most promising methods of coal gasification was promising methods of coal gasification was demonstrated by field tests conducted for the last 5 years by the Laramie Energy Research Center at Hanna, Wy. In fact, Phase 2 of the Hanna 2 test (completed in May 1976) was perhaps the most successful in-situ coal gasification test ever conducted. It more complete description of this test is given later. The experimental data are presented in Part 2 to confirm the theory developed presented in Part 2 to confirm the theory developed in this section. Since May 1976, other successful field tests have been reported by the Alberta Research Council, Texas Utilities, and the Lawrence Livermore Laboratory. NEED FOR A THEORETICAL MODEL Before this study, no physical theory was available that successfully predicted field test data. Many of the most important features of underground coal gasification (UCG) were poorly understood or not understood at all. For example, the heating value of gas produced during the Hanna field tests was much higher than that reported for previous field experiments at other locations; the previous field experiments at other locations; the reasons for this anomaly were unknown. It was widely believed that the optimistic results from the Hanna field experiments might be peculiar or specific to the Hanna area. However, the development of a theory of UCG and successful field experiments with the linked, vertical well process at other locations now are proving this assumption false. The need for a theoretical understanding of UCG has become readily apparent. A more thorough interpretation of field test results required the development of a theoretical mathematical model for the process. In addition, design capability must be developed before UCG can become a commercial process. This capability is essential for carrying process. This capability is essential for carrying out economic studies and risk analyses as well as engineering design. The design method must determine many variables, such asgas composition,gas heating value,air injection rate requiredgas produced per unit volume of air injected,coal consumption rate,effect of coal composition,effect of coal bed thickness,effect of ash content,effect of moisture content,effect of varying pressure and air injection rate, andwell spacing and configuration. The theory developed in this study provides definite information concerning Items 1 through 10 as well as several items not listed. Item 11 can be determined by a two-dimensional extension of the methods described here. Not infrequently, design methods were developed empirically on the basis of experimental data. In fact, the Soviet Union has used this approach to UCG. A theoretical predictive method, however, is more desirable because much less costly field testing is required to validate the method. Once the method is fully validated, it can be used to predict UCG behavior even under operating predict UCG behavior even under operating conditions never tested previously. SPEJ P. 300

European energy crisis, triggered by the conflict between Russia and Ukraine, has again drawn attention to the decarbonization of fossil energy sources. However, few studies have objectively considered coal from an integrated life cycle and its position in the energy system. In the present study, we used the integrated life cycle analysis and fixed-effect panel threshold model to reveal that (1) power generation and heating and iron and steel smelting are the highest CO2 emission sectors. In addition, the coal chemical industry and power generation and heating are the two sectors with the highest contribution rate of CO2 emissions. (2) Based on these, underground coal gasification (UCG) and underground coal gasification-integrated gasification combined cycle (UCG-IGCC) technologies were introduced to innovate the coal life cycle (the process cycle of coal production and utilization). The panel threshold model has proved that when the energy intensity falls in the interval 0.363-2.599, UCG-IGCC technology could be the complement in mitigating CO2 emissions. (3) Finally, for the same amount of emission mitigations, the social cost of innovating coal production and utilization processes using UCG-IGCC technology will be lower than phasing out coal-fired power plants using carbon prices. For China, UCG-IGCC and renewable energy should be developed simultaneously.