PRESENTATION TOPIC

UNDERGROUND COAL GASSIFICATION

PRESENTATION BY

ABDURRABB KHAN

COAL

COAL GASSIFICATION

UNDERGROUND COAL GASSIFICATION

THE BASIC UCG PROCESS

COMPLETE UCG PLANT OVERVIEW

PROCESS CONTROL

UCG PRODUCTS

WHY UCG IS IMPORTANT

UCG ADVANTAGES

UCG DISADVANTAGES

DEVELOPMENTS, PROJECTS AND INTERESTS

CONTENTS

COAL

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

Coal Gasification-Controlled combustion of coal and obtain syngas (H2, CO).

1) Underground coal gasification (UCG)2) Surface coal gasification(SCG)

COAL GASIFICATION

Underground Coal Gasification

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)

TheBasicUCGProcess

Two wells drilled into the

coal, one for injection of

the oxidants, another to bring

the product gas to

the surface.

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Two boreholes are drilled into the coal seam and a path between these two

boreholes is established.

Borehole maximum depth 600m, Distance between two boreholes is about

50m.

UCG – 1st stage

1. Fracture of the coal seam by air pressure or explosions2. Reverse combustion technique3. Modern directional drilling techniques(magnetic target, magnetic

detector)

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

–

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

–

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Operator of an underground coal gasification plant has following controls over the process.

TemperaturePressureGas flow rateComposition of gas at injection and production well

PROCESS CONTROL

Change in gas composition and temperature from the injection well to the production well at 50meter apart.

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.

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Coal

UCG - Products

Coal seam shallower then 150m is rejected.

Coal seam Deeper then 600m is rejected.

Coal Seams thinner then 10m are also rejected

Recovery factor is 65% and remaining 35% is left for roof support.

LIMITATIONS FOR THE SELECTION OF COAL DEPOSIT

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.

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.

UCG is producing fuels and hydrocarbon feedstock today from unrecoverable coal deposits.

Countries are turning to UCG to fully utilize their coal resources in an economically viable and environmentally acceptable manner.

WHY UCG IS IMPORTANT?

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UCG - Utility

Composition of syngas:

syngas chemical composition can vary based on the raw

materials and the processes, the syngas from coal

gasification generally is a mixture of 30 to 60% carbon

monoxide, 25 to 30% hydrogen, 5 to 15% carbon dioxide,

and 0 to 5% methane.

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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

1. Environmentally friendly

2. Significant reduction in CO2, SOx, NOx emissions

3. No Waste disposal (Ash Trapped Underground)

4. Reduced emission of Green House Gases by CO2 Sequestration

5. Short Construction and Commissioning Time

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UCG - Advantage

1) Surface subsidence

2) Aquifer water contamination

3) 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.

UCG- DISADVANTAGES

In the last few years there has been significant renewed interest in UCG as the technology has moved forward considerably.China has about 30 projects in different phases of preparation that use underground coal gasification.India plans to use underground gasification to access an estimated 350 billion tones of coal.South African companies Sasol and Eskom both have UCG pilot facilities that have been operating for some time, giving valuable information and data.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 Blood wood Creek in 2008.

DEVELOPMENTS, PROJECTS & INTEREST