UNDERGROUND COAL GASSIFICATION (UCG)

UNDERGROUND COAL GASIFICATION (UCG)

BY- ABINASH SWAIN3rd year, NIT Rourkela

TOPICS TO BE COVEREDWhat is UCG?Process description & Required conditions Principles and technology involvedBenefitsDemeritsFuture Scopes with case-studiesConclusion

UCG?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 surface gasifiers. The economics of UCG look promising as capital expenses should be considerably less than surface gasification Essentials.

Process descriptionDifferent stages for UCG:Step 1: Find the coalStep 2: Drill the boreholesStep 3: Link the boreholesStep 4: Ignite the coalStep 5: Inject O2 and steamStep 6: Extract the syngas

Simple model

Source: www.groundtruthtrekking.org/WildResourceIssuesUndergroundCoalGasification.html

2/ Combustion Zone Oxidation zone exothermic Temperature rising Coal consumedC+O2 CO2 C+1/2 O2 CO 2CO+O2 2 CO2 CH4+O2 CO2+2H2O3/ Gasification Zone Reduction zone Endothermic Temperature falling until reactions stop no more coal consumedC+CO2 2 CO H2O+C CO+H2

4/ Reduction Zone Gas transport zone Lower temperature Shift conversion reaction reduces heat value of gas CO+H2O CO2+H2methanation C+2 H2 CH4General Gasification Zones in Burn Cavity along burn directionInitiation of cavity using counter current flow1/ De-volatilization zone

4

321

Source: www.ehp.qld.gov.aumanagementucgimagesucg-diagram.gif

Two wings of the model

The underground gas generator The surface plant to receive the gas and process it for use in power plants

Conditions Suitable for UCGCoal seam should not have major geological disturbancesThe roof and floor of the seam should have low permeability so that leakage is minimised.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 bed.Any seam thickness can be gassified. Thickness of 6m is preferable. Reserve should be high and it should be nearer to customer.

Factors Affecting UCG

Souce: www.ehp.qld.gov.au

Technology involved in UCGOpening up coal seam for gasificationDrilling patternLinkage between boreholesLinking operationGasification processSubsidence Extraction process at the surface (not that mining peoples job)

Benefits of UCGUn-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 oxidesPotential 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 stockAsh is left in u/g and less tipping dirt is produced Labour intensity is low.

Output gases and their USEThe predominant product gases are methane, hydrogen, carbon monoxide and carbon dioxide. Ratios vary depending upon formation pressure, depth of coal and oxidant balance. Gas output may be combusted for electricity production. Alternatively gas can be used to produce synthetic natural gas or hydrogen. carbon monoxide can be used as a chemical feedstock for the production of fuels like diesel, fertilizer, explosives and other products

DisadvantagesThe extraction of reserve is less than deep mining(energy balance is also less favourable)Capital input is greater than deep miningGas produced is dirty, has a low calorific value and is variable in quality.The cost of making SNG will be higher than importing liquid natural gasThe gas is costly to pipe much over 16km and to storeThere will be noise from drillingNew skills are to be taught. There is no rose without any thorn

Source: youtube.com/CSG

Future Scopes The former USSR had made success in this method. But countries like France, Belguim,UK have take up experimental projects to improve the technology.USBM and ERDA in their trials at Hanna, Wyoming have found encouraging results in UCG.In India, coal deposits of around 60 million tonnes has been found in Gujarat at depths of 1300-1800 m . Steps are being taken for UCG as conventional method of mining is not feasible.

By some estimates, UCG will increase economically recoverable reserves by 600billion tones. Lawrence Livermore National Laboratory estimates that UCG could increase recoverable coal reserves in the USA by 300%Cougar Energy and Linc Energy have conducted pilot projects in Australia based on UCG technology provided by Ergo EnergyIn South Africa, Eskom (with Ergo Energy as technology provider) is operating a demonstration plant in preparation for supplying commercial quantities of syngas for commercial production of electricity. ENN has also operated a successful pilot project in China.

CONCLUSION

Increase in the price of Oil and natural gasesGrowing Demand for alternative energy source Technological Advancement & resilience towards adopting thoseSuitable Condition for GasificationNon feasibility of Coal Seam

Oil price low? Dnt worry, the wave will hit soon. UCG will increase recoverable resources to 600 billion tons 18

Thank You! https://in.linkedin.com/in/abinash-swain-197b48101