This document provides an overview of underground coal gasification (UCG) in 3 stages: 1) Coal is fractured and ignited to produce syngas through controlled combustion without mining the coal seam. 2) Syngas is brought to the surface through a production well while process variables like temperature are controlled. 3) UCG offers advantages like access to deep, unmineable coal reserves and reduced emissions, but risks include subsidence and groundwater contamination. The document outlines the UCG process and highlights recent interest and projects in countries like China, India, South Africa and Australia.

2. PRESENTATION TOPIC
UNDERGROUND COAL GASSIFICATION
PRESENTATION BY
KOMAL AROOSH
DEPARTMENT
CENTER FOR COAL TECHNOLOGY
PUNJAB UNIVERSITY LAHORE

3. *COAL
*COAL GASSIFICATION
*UNDERGROUND COAL GASSIFICATION
*THE BASIC UCG PROCESS
*UCG 1ST STAGE
*UCG 2ND STAGE
*UCG 3RD STAGE
*COMPLETE UCG PLANT OVERVIEW
*PROCESS CONTROL
*UCG PRODUCTS
*WHY UCG IS IMPORTANT
*UCG ADVANTAGES
*UCG DISADVANTAGES
*DEVELOPMENTS, PROJECTS AND INTERESTS

4. *COAL
*Coal is a black or brown rock that can
be ignited and burned to produce
energy in the form of heat.

5. Coal Gasification-Controlled combustion of
coal and obtain syngas (H2, CO).
1.Underground coal gasification (UCG)
2.Surface coal gasification(SCG)
*

6. *
* Underground coal gasification (UCG) is the in-
situ conversion of coal into combustible gases.
In which unmined coal seams are reacted
underground, with insufficient oxygen for
complete combustion to produce
syngas(CO+H2)

7. *
Two wells drilled into the
coal, one for injection of
the oxidants, another to bring
the product gas to
the surface.

8. 8
Two boreholes are drilled into the coal seam and a path between these
two borholes is established.
UCG – 1st stage

9. 1.Fracture of the coal seam by air pressure or
explosions
2.Reverse combustion technique
3.Modern directional drilling techniques(magnetic target,
magnetic detector)

10. 10
Coal is ignited, combustion is maintained by injecting air or oxygen and
steam
–

11. 11
The resulting gases are brought to surface by the second bore hole
–

12. 12

13. Operator of an underground coal gasification plant has
following controls over the process.
1.Temperature
2.Pressure
3.Gas flow rate
4.Composition of gas at injection and production
well
*

14. *
*Flammable gases combust in the first ten meters, consuming all of
the available oxygen and causing a sharp rise in gas temperature.
*At the end of the combustion zone, the gases primarily consist of
hot, non-flammable N2,CO2, and H2O. In the following 40 meters,
steam and CO2 react with char, so H2 and CO concentrations rise
while steam and CO2 levels fall.
*The methanation reaction raises the concentration of methane. The
gas calorific value increases as the gas flows through the cavity.
*The temperature falls due to the endothermic nature of the steam
and CO2 gasification reactions, as well as the heat required to
evaporate water seeping into the cavity. By the time the gas
reaches the production well at 50 meters, the temperature is barely
sufficient to sustain a significant rate of gasification.

15. Temperature 200-550oC Temperature 550-900oC Temperature more than 900oC
Drying & Pyrolysis Zone Reduction Zone Oxidation Zone
Coal CH4 + H2O
CO + CO2
H2 + C
Hydrocarbons
C + H2O CO + H2
CO2 + C 2CO
CO + H2O CO2 + H2
CO + 2H2 CH4
C + O2 CO2
C +1/2 O2 CO
CO +1/2O2 CO2
Coal + O2 CO2 + CO + H2O
Schematic of the processes involved in UCG
Air, Oxygen & Steam Product Gases ( CO, CO2, H2, CH4, N2 , Steam & Tar

16. *

17. 17
Coal
UCG - Products

19. *

20. Coal seam shallower then 150m is rejected
Coal seam Deeper then 600m is rejected.
Coal Seams thinner then 10m are also rejected
Recovery fector is 65% and remaining 35% is left for roof
support.
*

21. 1. Most known coal resources in the world are too deeply buried
to be economically mined out. Nearly 85% of known coal
reserves are un-mineable with surface mining. So, UCG is
proposed for these reserves.
2. The costs of drilling air injection and syngas production wells
are a small fraction of the cost of a gasification complex, so
deeply buried coal seams may be gasified at a reasonable cost.
3. UCG is producing fuels and hydrocarbon feedstock today from
unrecoverable coal deposits.
4. Countries are turning to UCG to fully utilize their coal
resources in an economically viable and environmentally
acceptable manner.
*

22. 22
UCG - Utility

23. 23
Facilitates exploitation of deep /
unminable coal reserves
Higher efficiency coupled with low capital
costs than conventional coal-fired station
Eliminates SO2 emission
Radio active ash remains deep down…
UCG - Advantage

24. 24
*Environmentally friendly
*Significant reduction in CO2, SOx, NOx emissions
*No Waste disposal (Ash Trapped Underground)
*Reduced emission of Green House Gases by
CO2 Sequestration
*Short Construction and Commissioning Time
UCG - Advantage

25. 1.Surface subsidence
2.Aquifer water
contamination
Removal of the coal from coal seam can
cause the roof fall, when roof collapses the
water from a shallow freshwater aquifer
mixed with the tar-contaminated coal and
rock and is contaminated.
*

26. In the last few years there has been significant renewed interest in UCG as
the technology has moved forward considerably.
1. China has about 30 projects in different phases of preparation that use
underground coal gasification.
2. India plans to use underground gasification to access an estimated 350
billion tonnes of coal.
3. South African companies Sasol and Eskom both have UCG pilot facilities
that have been operating for some time, giving valuable information and
data.
4. In Australia, Linc Energy has the Chinchilla site, which first started
operating in 2000. Carbon Energy has completed a successful 100 day
commercial scale study in Bloodwood Creek in 2008.
*