Gasification is a process that converts carbonaceous
material, Such as fossil fuels and biomass in to a mixture
of mostly hydrogen and carbon monoxide( called
Synthesis gas & Syngas)
The syngas can be burned as a fuel or processed to
produced chemical and other fuels
coal gasification is still in development, it is also supposed
to be a very perspective technology. Be a very perspective
technology. applied to many branches of industry such as
chemistry, metallurgy and energy production, provided
that different requirements about its parameters will be
fulfilled. Many characteristics of product gas are strongly
connected with its composition. Therefore, problem of
optimization of CG technology becomes an especially
important issue. In context of using syngas for particular
aims, earlier mentioned optimization could be
understood as a choice of the best scope of input
parameters and appropriate proceeding of process.
Underground Coal Gasification
Underground coal gasification (UCG) is an industrial
process, which enables coal to be converted into
product gas.UCG is an in-situ gasification process
carried out in non-mined coal seams using injection of
oxidants, and bringing the product gas to surface
through production wells drilled from the surface.
The process converts coal into a gaseous form (syngas)
through the same chemical reactions that occur in
The economics of UCG look promising as capital expenses
should be considerably less than surface gasification essentials.
Different stages for UCG:
Step 1: Find the coal
Step 2: Drill the boreholes
Step 3: Link the boreholes
Step 4: Ignite the coal
Step 5: Inject O2 and steam
Step 6: Extract the syngas
Condition suitable for UCG
Coal seam should not have major geological disturbances
• The roof and floor of the seam should have low permeability
so that leakage is minimized.
• Seam should be preferably free from water. Water should be
drained off before process.
• Coals of low quality is preferred. Using sub-bituminous coal
has advantages of having greater permeability & its tendency
to sink and spell when heated aids to providing the ‘packed
• Any seam thickness can be gassified. Thickness of 6m is
• Reserve should be high and it should be nearer to customer.
Technology Involved in UCG
Opening up coal seam for gasification
• Drilling pattern
• Linkage between boreholes
• Linking operation
• Gasification process
• Extraction process at the surface (not that mining
Benefits of UCG
Un-economical seams (low quality/ greater depth with thin
seam) can be made useful.
It provides an indigenous gas/energy source.
Flexibility in commercial use, less Nitrogen and sulphur oxides.
Potential method of exploitation of reserves which are not
amenable to conventional mining.
Elimination of hard and often unhealthy jobs of men in u/g
Impact on the environment is far less. The fertile soil is
conserved. No dumps or waste heaps.
Possibility of recovering coal with high sulphur and ash.
Much less time for construction work of UCG station.
The gas is a potential chemical feed stock
Ash is left in u/g and less tipping dirt is produced
Labour intensity is low.
The extraction of reserve is less than deep mining (energy
balance is also less favourable)
Capital input is greater than deep mining
Gas produced is dirty, has a low calorific value and is variable
The cost of making SNG will be higher than importing liquid
The gas is costly to pipe much over 16km and to store
There will be noise from drilling
New skills are to be taught.
Surface Coal Gasification
Developed in 1800s to produce town gas and city lighting
Renewed interest due to rise in oil prices, depleting oil &gas
reserves and IGCC technology
Coal is exposed to hot steam and controlled amounts of air or
oxygen under high temperatures (250°-900°C) and pressures.
Produces Syngas, hydrocarbons, water vapours, anhydrous
ammonia and phenols. The gas comprises of N2, CO2, CO, H2,
CH4, O2, etc•
Reduced greenhouse gases e.g. CO2 can be captured easily
and at lower costs
One of the most abundant energy sources
it can be burned directly, transformed into liquid, gas, or
Inexpensive compared to other energy sources
Good for recreational use (charcoal for barbequing, drawing)
Can be used to produce ultra-clean fuel
Can lower overall amount of greenhouse gases ( liquification
Leading source of electricity today
Reduces dependence on foreign oil
By-product of burning (ash) can be used for concrete and
Source of pollution emits waste, SO2 , Nitrogen Oxide, ash
Coal mining mars the landscape
Liquidification , gasification require large amounts of water
Physical transport is difficult
Technology to process to liquid or gas is not fully developed
Solid is more difficult to burn than liquid or gases
Not renewable in this millennium
High water content reduces heating value
Dirty industry—leads to health problems
Dirty coal creates more pollution and emissions