What is Underground Coal Gasification (UCG)?

UCG uses the process of gasification to produce Syngas, which is rich in hydrogen (H2), carbon monoxide (CO) and methane (CH4).

The process gasifies coal in-situ, that is, where it lies under the ground. This eliminates the need for mining the coal and processing it through a surface gasification plant. UCG has been utilised in both commercial scale and trial applications since the early 1900s.


In its simplest form, the UCG process works like this:

  1. Vertical wells are drilled into the coal and linked together horizontally.
  2. The coal seam is ignited and air or oxygen is pumped into a well (the injection well) to allow for combustion of the coal.
  3. Combustion produces heat, carbon dioxide and some Syngas through partial combustion.
  4. Through a series of chemical reactions involving pressure, heat and carbon dioxide from combustion, steam (generated from water in the coal) and carbon from the coal, Syngas is produced.
  5.  The Syngas flows from the gasification chamber through the horizontal connection in the coal seam and flows to the surface through another well (production well.)

The composition of the gas produced depends on many factors including coal type, operating pressure and temperature, water ingress to the process, and the type of oxidant used (air or oxygen).

 

Underground Coal

Did you know?

  • UCG means coal is accessed underground, without the need for a surface mine.
  • New technology, such as directional drilling, and demand for energy, are driving expansion in the Syngas industry.
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