Underground Coal Gasification Technology Research Articles

Дослідження геоміграційних процесів під час підземних газифікації та спалювання вугілля

Today one of the main problem for areas of intense technological activities related to the production, processing and use of fossil fuels is management and environmental protection. With the current technology development difficult to achieve effective results in terms of further improving the technical and economic performance and in terms of environmental protection. Fundamentally new in the transition to underground coal gasification (UCG) and coal combustion (UCC) is the transition to non-waste technology. The possibility of smoke emission elimination through recycling. directing the underground gasification oxides of sulfur, nitrogen and other toxic components of smoke emissions. In underground water is possible their destruction to non-toxic state. Other harmful for the biosphere chemicals substances (arsenic, strontium) also remain in the underground gas generator. Also in the underground space may direct solid waste for laying out space voids possible reduction surface subsidence and preserve the landscape. Reducing the volume of drilling and laying out space allows you to transfer temporarily useless agriculture territory. Underground space of gas generators with hot rocks can be used for commercial purposes. Utilization of physical warm rocks by pumping cold and getting hot coolant can increase efficiency. But with all the above-mentioned, the environmental justification for building the station of underground coal gasification and coal combustion necessarily involves the analysis and forecast of man-made impact on the geological environment. In terms of the studied region of brawn coal Dnieper basin the prospects of widespread introduction of underground coal gasification and coal combustion technology inherent protection from problem resolution is actively used in the household groundwater from chemical contamination of underground coal combustion, disposal and coolant waste.

Underground coal gasification (UCG): A new trend of supply-side economics of fossil fuels

China has a huge demand for energy. Under the present energy structure of rich coal, lean oil, less gas, limited and low-rising rate renewable energy, discussion focus is now on the high-efficient mining of coal as well as its clean-and-low-carbon use. In view of this, based on an analysis of the problems in the coal chemical industry and the present coal utilization ways such as Integrated Gasification Combined Cycle (IGCC), this paper proposes that underground coal gasification (UCG) technology is a realistic choice. By virtue of its advantages in many aspects such as safety & environment, integrated use of superior resources, economic feasibility, etc. this technology can serve as the front-end support and guarantee for coal chemical industry and IGCC. Under the present situation, the following proposals were presented to promote the development of this technology. First, R&D of technical products should be strengthened, a comprehensive feasibility study assessment system should be established, and the relevant criteria in the industry should be formulated. Second, precise market positioning of UCG products should be made with much concern on the integrated economic indicators of each product's complete flow scheme, following the principle of “Technical Feasibility First, Economic Optimization Followed”. Third, a perfect operation and management pattern should be established with strict control over high-efficient, environmentally-friendly, safe, harmonious & compact objectives in the whole industry chain. In conclusion, to realize the large-scale UCG commercial production will strongly promote the optimization and innovation of fossil fuels supply-side economics in China.

Low Carbon Cycle Mining Technology of Fossil Energy and Demonstration Project in Xinjiang

Combined with the unique resources of coal seams and oil reservoirs in Xinjiang area, the application and demonstration projects of deep fossil energy low carbon cycle mining technology are developed. In the reservoir formation containing both coal seam and oil, the underground gasifier is constructed by drilling or waste oil-well in the upper coal seam and the coal resources is gasified by using underground coal gasification (UCG)technology. Gas is separated into CO₂, CH₄, CO and H₂. CH₄ is liquefied to natural gas (LNG). CO and H₂ are used to generate electricity. And CO₂ is injected into oil displacement at the bottom of the coal seam to enhance oil recovery, which can be stored up at the same time. The technical system comprises an underground coal gasification unit, a gas separation and compression unit, a generating unit and a drive oil storage unit. The demonstration project would reduce carbon dioxide of 208900 tons per year.

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

Underground Coal Gasification (UCG) technology is steadily improving due to high scientific and industrial efforts in currently over 14 countries worldwide. A fundamental UCG objective refers to syngas production for multiple end-uses, accompanied by environmental impact mitigation focusing contaminant reduction. In terms of this topic, the control of groundwater quality endangering tars has been a key problem rarely addressed in UCG publications so far. Considering UCG main sub-processes, operating parameters and tar spectrum knowledge grounded upon established thermodynamic equilibrium principles, an innovative and flexible model approach for coupled gas quality-tar production balances is presented here. The model is validated against literature data of the Hanna-I and Centralia-Partial Seam CRIP (PSC) field trials. For both trials good matching results were found. Main gas compounds and Lower Heating Values (LHVs) results are close to reported data partly reaching less than 10% deviation (relative error range for main compounds 4.32–18.6%, LHV 6.60–21.7%). Tar literature trend-modeling comparisons down to the single pollutant scale are addressed for the first time considering published data. Results here successfully reflect main qualitative tar tendencies, while current quantitative prognoses are on a satisfactory level, and expected to be further improved with the availability of more comprehensive in-situ data.

Life cycle assessment of heat production from underground coal gasification

In Poland, coal is the main fuel used for heat production. Innovative clean coal technologies, which include underground coal gasification (UCG), are widely developed. This paper presents the analysis results of life cycle assessment (LCA) and material flow analysis (MFA) of using synthesis gas from UCG for heat production. The paper presents the results of a comparative analysis of MFA and LCA for four variants of heat production, which differed in the choice of gasifying agent and heat production installations. Environmental analysis was made based on LCA with ReCiPe Midpoint and ReCiPe Endpoint H/A method, which allowed to analyse of different categories of the environmental impact. LCA was performed based on the ISO 14040 standard using SimaPro 8.0 software with Ecoinvent 3.1 database (Ecoinvent 2014). Umberto NXT Universal software was used to develop MFA for heat production. LCA analyses included hard coal from a Polish mine and synthesis gas obtained in the experimental installations in the Central Mining Institute in Poland. MFA performed for technology of utilizing gases from UCG have made it possible to visualize materials and energy flow between different unit processes in the whole technological chain. Moreover, the analyses enabled identification of unit processes with the largest consumption of raw materials, energy and the biggest emissions into the environment. It has been shown that the lowest environmental burden is attributed to the technology, which uses high-pressure chamber with gas turbine in which the synthesis gas from UCG is burned and oxygen was a gasifying agent. Analysis of LCA results showed that the major environmental burden includes greenhouse gas (GHG) emission and the fossil fuels depletion. GHG emission results primarily from the direct emission of CO2 from gas combustion for heat production and electricity consumption used in gasifying agents preparation phase. In order to increase the environmental efficiency of heat production technology using UCG, the most important activity to be considered is limitation of dust-gas emissions, including primarily CO2 removal process and efficiency increase of the installation, which is reflected in the reduction of coal consumption. It is important to highlight that this is the first attempt of MFA and LCA of heat production from UCG gas. Since no LCA has ever been conducted on the heat production from underground coal gasification, this study is the first work about LCA of the heat production from UCG technology. This is the first approach which contains a whole chain of unconventional heat production including preparation stages of gasifying agents, underground coal gasification, gas purification and heat production.

Competitiveness and Cost Sensitivity Study of Underground Coal Gasification Combined Cycle Using Lignite

To push the underground coal gasification (UCG) technology toward commercialization, its competiveness and cost components still need to be investigated. This paper compares the power generation cost of underground coal gasification combined cycle (UCGCC) with pulverized coal (PC) plants, integrated gasification combined cycle (IGCC), and natural gas combined cycle (NGCC). Cost sensitivity of the UCGCC as a function of coal seam depth and thickness was also examined. The results indicate that UCGCC is very competitive compared to PC and IGCC. Within the same assumed fuel price range, the power generation cost for UCGCC was $45–48/MWh, whereas it was $45–60/MWh for PC and over $100/MWh for IGCC. The generation cost of UCGCC was as low as NGCC at low natural gas prices, but UCGCC was able to provide a lower CO2 capture cost. Dependent upon the assumed fuel prices, the capture cost for the UCGCC was $27–28/tonne of CO2, whereas it was $47–58/tonne of CO2 for NGCC. It is also found that the cost of UCGCC decr...

Eco-efficiency of underground coal gasification (UCG) for electricity production

Hard coal is one of the main fossil fuels used to produce electricity in the world. Its combustion in power plants is associated with emissions of gas and dust pollutants. The article presents results of eco-efficiency assessment, life cycle assessment (LCA) and life cycle costing (LCC) of underground coal gasification (UCG) with the shaftless method and sensitivity analysis of eco-efficiency of electricity production from UCG. Eco-efficiency analyses considered Polish conditions. Results of LCA consider such damage categories as: impact on human health, quality of an ecosystem and use of resources. The largest impact on damage categories was caused by CO2 emission from syngas combustion and electricity consumption. Based on LCC results was concluded that for cost effective production of electricity with UCG it is necessary to maximise the scale of an installation while optimising use of the produced electricity. Through combusting UCG syngas in existing power plants, combined heat and power plants or heat plants, as well as electricity producing for own needs of a mine which enables avoiding transmission fees, which are actions increasing competitiveness of UCG technology. Sensitivity analysis showed, that the main determinants of eco-efficiency of producing electricity with UCG are availability of an installation to produce electricity and thickness of a coal seam.

Research on the surface movement rules and prediction method of underground coal gasification

With the continuous development of the technology of underground coal gasification (UGC), it gradually moves into commercial development. However, there is limited measured data and related research on the overlying strata and surface movement rule caused by underground coal gasification, which has severely restricted the further application of underground coal gasification. In order to solve the problem of surface subsidence prediction of underground coal gasification, this numerical simulation software, FLAC3D, is adopted to study the differences of overlying strata and the surface movement rule of UGC strip mining (UCG mining) and strip mining, and the differences of prediction parameters under different recovery ratios. The model is established according to the geological and mining conditions of the underground coal gasification experiment area in China. The research results show that overlying strata and surface movement rules of UCG mining and strip mining are similar. So, the surface subsidence prediction of UCG mining can refer the prediction method of strip mining. Meanwhile, the difference values of surface movement extrema under different recovery ratios are less than 5 mm and the difference values of surface subsidence boundary are not more than 10 m. Therefore, the surface subsidence prediction parameters of UCG mining can be chosen as the corresponding prediction parameters of strip mining. Finally, the surface subsidence prediction method of UCG mining is proposed based on the above research results and prediction software is compiled for engineering application. Research results have important theoretical and practical significance for promoting the application of underground coal gasification.

Basic Aspects Of Productivity Of Underground Coal Gasification Process

Abstract An analysis of conditions which enable attaining possibly highest productivity of industrial scale underground coal gasification technology is presented. The analysis was prepared basing on results obtained during an experimental gasification process conducted in workings of an active hard coal mine. Basic aspects determining application and productivity of the technology concern both general conditions, referring to the hard coal seam being gasified, and practical issues, which need to be considered in coal mine conditions. To present them, the technology of underground coal gasification and still commonly used classical longwall method of mining coal seams are compared.

Low-calorific gasification of underground coal with a higher humidity

The technology of underground coal gasification (UCG) belongs to the group of so called clean coal technologies. It can form a product called syngas, which can serve as a fuel for energy production or can be further processed in the chemical industry. This technology can gasify coal underground which cannot be mined by current methods from economic and technological reasons. Like any technology, UCG also has its limitations. One of them is the high humidity of coal (40%). Article, based on long lasting experimental research, analyzes the possibilities of increasing the UCG efficiency. Especially for lignite with a higher humidity content using only air as an oxidiser. It analyzes the creation of syngas components (CO, H2, CH4), its calorific value during the process in a special laboratory equipment for UCG research. It was demonstrated that the calorific value and syngas quality also depends on the location of sampling point. Based on this knowledge, the principle of a new method, that for the above mentioned conditions (low-calorific coal with a higher humidity), improves the UCG technology from the point of syngas quality and is mentioned in the conclusion.

Underground coal gasification: issues in commercialisation

Back in 2007, it was expected that commercial gas production from underground coal gasification (UCG) technology would be in progress within the following 5 years. This has not occurred, particularly in Australia, where at the time three commercial projects were being aggressively pursued. This paper reviews each of five key issues that may be considered to have delayed UCG commercialisation. Of these, it is concluded that the primary factor is the use of government environmental policy to achieve its preferred energy outcomes, as in the development of the coal seam gas industry in Australia. It is concluded that the UCG industry must select appropriate markets and utilise small-scale financially viable projects to achieve its required commercial breakthrough.

Underground Coal Gasification: A Regulatory Framework for Alberta

Underground Coal Gasification (UCG) is a new emerging clean coal technology. It holds promise for reaching and making use of very deep coal seams that technically could not otherwise have been mined at these depths. UCG technology and knowledge developed significantly during the 20th century. Countries around the world with large coal deposits sustain and promote UCG research and launch projects with the intention to commercially deploy UCG. Alberta currently hosts two UCG projects, and a third project is under consideration. The development of these projects suggested the need for a UCG specific regulatory approval process. In 2011, Alberta enacted specific UCG legislation. This article deals with recent developments in UCG technology and its regulations. The aim of this article is to present Alberta’s current UCG regulatory framework as a model for other jurisdictions.

Overview and modeling of mechanical and thermomechanical impact of underground coal gasification exploitation

From an economic point of view Underground Coal Gasification (UCG) is a promising technology that can be used to reach coal resources that are difficult or expensive to by conventional mining methods. Furthermore, the process addresses safety concerns, by avoiding the presence of workers underground. An optimal UCG process requires the integration of various scientific fields (chemistry, geochemistry, geomechanics) and the demonstration of limited of environmental impacts. This paper focuses on the mechanical component of the UCG operation and its impact on the surrounding environment in terms of stability and land subsidence. The mechanical components are also considered. Underground mining by coal combustion UCG challenges include the mechanical behavior of the site and of stability of the overburden rock layers. By studying the underground reactor, its inlet and outlet, we confirm the key role played by mechanical damage and thermo-mechanical phenomena are identified. Deformation or collapse above the cavity may cause a collapse in the overlying layers or subsidence at the surface level. These phenomena are highly dependent on the thermoporomechanical behavior of the rock surrounding the cavity (the host rocks). Unlike conventional methods, the UCG technology introduces an additional variable into the physical problem: the high temperatures, which evolve with time and space. In this framework, we performed numerical analyses of the coal site that could be exploited using this method. The numerical results presented in this paper are derived from models based on different assumptions describing a raw geological background. Several 3D (3 dimensional) and 2D (2 dimensional, plane) nonlinear finite element modelings are performed based on two methods. The first assumes a rock medium as a perfect thermo-elastoplastic continuum. In the second, in order to simulate large space scale crack propagation explicitly, we develop a method based upon finite element deactivation. This method is built on a finite element mesh refinement and uses Mohr-Coulomb failure criterion. Based on the analysis of the numerical results, we can highlight two main factors influencing the behavior and the mechanical stability of the overburden, and consequently the UCG process evolution. The first is the size of the cavity. This geometrical parameter, which is common to all types of coal exploitation, is best controlled using the classic exploitation method. We show that in the case of UCG, the shape of the cavity and its evolution over time can be modified considerably by the thermomechanical behavior of the host rocks. The second is the presence of a heat source whose location and intensity evolve over time. Even if thermal diffusivity of the rock is low and only a small distance from the coal reactor is thermally affected, we show that the induced mechanical changes extend significantly in the overburden, and that subsidence can therefore be estimated at the surface. We conclude the integration of the mechanical analysis into a risk analysis process mechanical analysis can be integrated in a thorough risk analysis.

Impact analysis of the oxidant in the process of underground coal gasification

Technology of Underground Coal Gasification (UCG) is still under developing and providing alternative for conventional underground coal mining. Underground coal gasification is a process with may be environmentally and economically attractive for widespread use in the future. The quality of the produced gas from UCG can vary substantially depending on the injected oxidant used, operating pressure, oxidizer flow rate, type of coal, hydrological conditions of the coal seam, coal type and the mass and energy balance of the underground reactor. Paper analyzes the impact of the oxidant on calorific value of the syngas in a laboratory and operating conditions. Also is analyzed the effect of temperature in the oxidation zone of gasifier on gas composition and calorific value. Effect of oxidant on the gasification process has been verified on experimental gasifier equipment. The paper describes an experimental gasifier and devices that were used for measurement and control.

Charaterization of the Harmon Lignite for Underground Coal Gasification

The Harmon lignite bed of the Fort Union Formation (Tertiary Age) beneath western North Dakota presents opportunities for applying underground coal gasification (UCG) technology to recover the unmineable coal resources. However, some characteristics of the formation also present barriers. First, the local aquifers coincide with the lignite bed; second, the lithology of surrounding rocks changes greatly within a short distance. These factors set challenges in site screening, feasibility study and assessment of environmental risks. Although extensive investigation work about the Harmon lignite has been conducted, no work has been done for UCG application. In this paper, we review the site selection criteria of UCG, and apply the experience and tools of reservoir characterization in petroleum exploration to investigate the structure and properties of a target site in western North Dakota. Information and data from state and federal geological surveys, water resource commission and oil companies are collected. A 3-dimensional model is built to simulate the Harmon lignite bed, surrounding rocks and aquifers. This “coal reservoir characterization” work provides a clear view of the structure and composition of the lignite-bearing formation, as well as a better understanding of its in situ geology and hydrogeology. Results of this work greatly facilitate the UCG site selection process. Suitability of the potential site for UCG projects is discussed.

Underground coal gasification technology impact on coal reserves in Colombia

<p>In situ coal gasification technology (Underground Coal Gasification–UCG–) is an alternative to the traditional exploitation, due to it allows to reach the today’s inaccessible coal reserves’ recovery, to conventional mining technologies. In this article I answer the question on how the today’s reserves available volume, can be increased, given the possibility to exploit further and better the same resources. Mining is an important wealth resource in Colombia as a contributor to the national GDP. According with the Energy Ministry (Ministerio de Minas y Energía) [1] mining has been around 5% of total GDP in the last years. This is a significant fact due to the existence of a considerable volume of reserves not accounted for (proved reserves at year 2010 were 6.700 million of tons. Source: INGEOMINAS and UPME), and the coal future role’s prospect, in the world energy production.</p>

Environmental aspects of a field-scale underground coal gasification trial in a shallow coal seam at the Experimental Mine Barbara in Poland

A study on the environmental impacts of underground coal gasification (UCG) was conducted during a field-scale, in situ coal gasification experiment at the Experimental Mine “Barbara” in Poland. This two-week experiment was a part of a technological effort aiming to produce hydrogen-rich product gas using the UCG technology. As groundwater pollution is recognised to be the most serious environmental risk related to UCG, extensive investigations on the formation, release, and migration of contaminants were conducted. The study revealed a wide range of organic and inorganic contaminants that were characteristic for the UCG. The main organic contaminants were phenolic compounds and aromatic hydrocarbons (mono- and polycyclic). Among the inorganic species, heavy metals, ammonia and cyanides were the most serious group of contaminants. These compounds were identified in the post-processing effluents and in groundwater near the test site. The impact of the gasification process on the groundwater, however, was small and tended to effectively decrease over the time and distance from the cavity zone. A possible negative environmental impact of the gasification by-products, including ash and char left underground, was also evaluated. This study revealed that these post-gasification residuals are the main source of toxic trace elements, but the most volatile species, such as Hg, As and Se, tended to escape the cavity zone with the product gas during gasification phase. Monitoring activities detected no chemical hazards on the surface during the course of the experiment and after its termination; however, UCG-induced thermal effects on surface were observed.

Preliminary determination of the suitability of slags resulting from coal gasification as a pozzolanic raw material / Wstępne Określenie Przydatności Żużli Ze Zgazowania Węgla Jako Surowca Pucolanowego

Streszczenie Wymagania dotyczące ochrony środowiska, takie jak: ograniczenie emisji CO2, NOx i SO2 spowodowały coraz większe zainteresowanie nowymi technologiami energetycznego wykorzystania węgla. Jednąz testowanych i promowanych obecnie technologii jest zgazowanie węgla. Jednak, jak każda technologia produkcji energii wykorzystująca węgiel, powoduje ona powstawanie odpadów: popiołów lotnych i żużli. Ze względu na niewielką ilość instalacji zgazowania węgla funkcjonujących obecnie w świecie, odpady te sąwniewielkim stopniupoznane, dlatego też przed podjęciem decyzji o wprowadzaniu technologii zgazowania węgla, powinno się opracować technologię utylizacji powstających w niej odpadów. Najlepszym rozwiązaniem będzie oczywiście opraco­wanie kierunku ich gospodarczego wykorzystania. Jedną z możliwości rozpatrywanych dla gospodarczego wykorzystania żużli ze zgazowania jest zastosowanie ich jako składnika spoiw mineralnych o charakterze pucolanowym. W artykule przedstawiono wyniki badań aktywności pucolanowej dwóch żużli: żużla ze zgazowania węgla z instalacji energetycznego zgazowania oraz podziemnego zgazowania. Ze względu na skład chemiczny żużel MI można zaklasyfikować jako żużel zasadowy o składzie chemicznym zbliżonym do krzemionkowego po­piołu lotnego ze spalania węgla kamiennego. Z kolei żużel BA, z powodu czteroktrotnie wyższej zawartości tlenku wapnia, należy do grupy żużli słabozasadowych. Podstawowym i jedynym składnikiem mineralnym żużla MI jest faza szklista. W żużlu BA, obok fazy szklistej, tworzą się również fazy krystaliczne, a mianowicie: mullit 3 AI2O3 · 2 SiO2, kwarc p-SiO2-, anortyt Ca(Al2Si2O8), gehlenit Ca2Al[(Si,Al)2O7], wollastonit Ca3[Si3O9], 2CaO · SiO2 i 4 CaO • Al2O3 • Fe2O3. W wyniku badań stwierdzono, że żużel BA wykazuje większe wartości wskaźnika aktywności pucolanowej (75,1% po 90 dniach) od żużla MI (69,9% po 90 dniach). Niestety, wstępne badania pozwalają stwierdzić, że żużle te charakteryzują się zbyt niską aktywnością pucolanową i nie mogą być traktowane jako materiał pucolanowy w technologii produkcji cementu i betonu.

Study of Transverse Section Temperature Distribution in Underground Coal Gasification

In order for current laboratory studies of strata performances under high temperature to be applied in Underground Coal Gasification (UCG) technology, the temperature scope (range) of UCG must be studied. Based on the heat conduction differential equation, this paper simulates the transverse section temperature distribution of UCG in the multi-physics coupling field. It demonstrates that the strata properties at a range of two meters are affected by high temperature, and the influence on sandstone is more obvious than that of coal. The temperature curves show a trend of linear to nonlinear as time goes. This paper presents the precedent of using multi-field coupling calculation to simulate UCG.

Pollution of water during underground coal gasification of hard coal and lignite

Groundwater pollution is considered the most serious potential environmental risk related to the underground coal gasification technology (UCG). A variety of hazardous water-born contaminants have been identified during different UCG operations conducted so far, and in some locations long-term groundwater contaminations were observed. Characteristic organic UCG-related pollutions are mostly the phenols, benzene with its derivatives, polycyclic aromatic hydrocarbons, and heterocycles. In the inorganic array, ammonia, cyanides, sulphates, and heavy metals are usually identified. Although the fact that the coal rank affects the contaminants’ formation and release processes during the UCG is known, the information is still scarce. The main goal of the study presented in the paper is the comparison of the processes of formation and release of water contaminants produced during UCG simulations on hard coal and lignite. Significant differences in the qualitative and quantitative description of the contamination profiles were identified for both types of coal. From the analysis it follows that the formation of contaminants is the function of coal rank, the elemental composition of coal, and the gasification temperature. In case of hard coal gasification, the total load of inorganic and organic pollutants in the process water is substantially higher in comparison to lignite. It has been identified that the reaction pH is the parameter affecting concentrations of heavy metals in process waters. The macromolecular structure of coal and temperature were recognized as the main factors governing the distribution of organic compounds. The highly aromatised structure of hard coal becomes the source of substantial quantities of aromatic compounds; still the contribution of smaller species (one or two rings) is high. For lignite, the relative contributions of higher aromatics are greater as compared to hard coal.