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In Situ Coal Gasification:

In Situ Coal Gasification:. An Emerging Technology. Kristin M. Brown, Hydrologist. B.S. Geology – West Virginia University M.S. Hydrology – Colorado School of Mines Office of Surface Mining 1999 Broadway Ste 3320 Denver, Colorado 80202 (303)293-5048. Introduction.

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In Situ Coal Gasification:

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  1. In Situ Coal Gasification: An Emerging Technology

  2. Kristin M. Brown, Hydrologist • B.S. Geology – West Virginia University • M.S. Hydrology – Colorado School of Mines • Office of Surface Mining 1999 Broadway Ste 3320 Denver, Colorado 80202 (303)293-5048

  3. Introduction • In Situ Coal Gasification is the process of injecting an oxidant (air or steam) into a coal seam that reacts with the coal and water present underground to produce Synthesis gas (Syngas). • Syngas is can be used as fuel or feedstock for other chemical processes such as ammonia or liquid fuels. It can also be used for electricity production.

  4. History of In Situ Coal Gasification (UCG)

  5. History of In Situ Coal Gasification Continued

  6. HYDROSTATICPRESSURE

  7. PH = rgz • PH = Hydrostatic Pressure • r = Fluid Density • g = Gravitational Acceleration • z = Height of the Liquid Column Assuming the fluid is incompressible and z is reasonably small compared to the Earth’s radius

  8. Hydrostatic Pressure Courtesy of Susannah Strauss with www.UCG-GTL.com.

  9. Chemical Reactions for UCG Processes • Volatiles Oxidation • Char Oxidation • Water Evaporation • Pyrolysis • Gasification • Boudouard Reaction • Water Gas Shift • Methanation • Hydrogenating Methanation • O2 + CO, H2, CH4, HCs = CO2 + H2O • C + O2 = CO2 • H2O(l) = H2O(g) • Coal + Heat = Char + Ash + HCs + CH4 + H2 + H2O + CO + CO2 • C + H2O = H2 + CO • C + CO2 = 2CO • CO + H2O = H2 + CO2 • CO + 3H2 = CH4 + H2O • C + 2H2 = CH4

  10. Site Characterization • No high production aquifers within the expected vertical subsidence volume • Coal Seams > 30 feet thick are suitable • Coal seam depths 500 to 2,000 feet below ground surface are considered ideal • Immediate overburden unit should a thick vertical section of claystone or shale • Structural (faulting and Folding) considerations need to be made for UCG site selection.

  11. Well Completion and Linking • Air Pressurization between two wells • Injecting into man built galleries in the coal seam (i.e. to utilize remaining coal after underground mining) • Directional drilling in the coal seam with controlled injection • Injection in simultaneous channels is known as the Controlled Injection Procedure (CRIP)

  12. Well Completion and Linking

  13. Environmental Effects • Surface Subsidence • Groundwater Contamination • Carbon Capture and Sequestration (CCS)

  14. Surface Subsidence • Subsidence is the downward movement of subsurface material due to mining and the creation of an underground void that caves in. • surface disruptions, • excessive groundwater influx into the UCG reactor • mixing of separate water bearing units and • groundwater contamination • Subsidence can be and is controlled as it is in underground mining where surface movement is not desired. • UCG is analogous to conventional longwall mining with respect to subsidence

  15. Surface Subsidence At Hoe Creek, Wyoming, the cavity experienced a massive chimney collapse that propagated approximately 40 meters to the surface several weeks after the well was shut-in (LLNL, 2011).

  16. Groundwater Contamination • Groundwater contamination is considered the most serious potential environmental risk related to UCG. • Major groundwater pollutants include • Polynuclear and phenolic organic compounds • Ammonia • Sulfate and • Calcium

  17. Groundwater Contamination • Primary source of inorganic pollutants is ash leachate • Primary source of organic contaminants and ammonia is condensed vapors • Adsorption of organics to clay and lignite is an effective removal mechanism of the contaminant from groundwater

  18. Environmental Benefits • No Discharge of Tailings • Reduced Sulfur Emissions • Reduced discharge of Ash, Mercury and Tar • Carbon Capture and Sequestration

  19. Carbon Capture and Sequestration • CCS is the process to remove and store “greenhouse gases” from process streams to reduce the buildup of these gases in the atmosphere. • Involves the process of extraction, • Seperation • Collection • Compression • Transporting and • Geologic Strorage • CCS can be synergistically applied to Enhanced Oil Recovery or Enhanced Coal Bed Methane Recovery

  20. Carbon Capture and Sequestration

  21. Conclusions • Groundwater plays an important role in UCG • Positive Hydraulic Gradient towards the gasification chamber is needed. • Establishing a hydraulic circulation system is important so the gasification chamber can be flushed and cleaned • Hydraulic control is the most important feature of UCG. • Controls the UCG process and prevents groundwater contamination. • Site Characterization and well completion are also of utmost importance for a successful UCG operation. • Coal resources not suitable for conventional mining are ideally suited for UCG • Environmental Benefits to UCG (i.e. Carbon Capture and Sequestration)

  22. Questions?

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