UNDER GROUND COAL GASSIFICATION

PRESENTATION TOPICUNDERGROUND COAL

GASSIFICATION

PRESENTATION BY KOMAL AROOSH

DEPARTMENT CENTER FOR COAL TECHNOLOGY

PUNJAB UNIVERSITY LAHORE

CONTENTS*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

*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)

*The Basic

UCG

Process

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 borholes is established.

UCG – 1st stage

Techniques applied to establish

the flow path between the

vertically drilled boreholes

1.Fracture of the coal seam by air pressure or explosions

2.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

UCG – 2nd stage

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

UCG – 3rd stage

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Complete UCG plant overview

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

1.Temperature2.Pressure3.Gas flow rate4.Composition 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.

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

* Effect of the seam axial distance on calorifics value of

syngas and temperature of the seam.

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Coal

UCG - Products

* Cavity Growth

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

*Limitations for the selection of coal deposit

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.

*Why UCG is Important?

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UCG - Utility

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Facilitates exploitation of deep / unminable coal reservesHigher efficiency coupled with low capital costs than conventional coal-fired station

Eliminates SO2 emissionRadio active ash remains deep down…

UCG - Advantage

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*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

1.Surface subsidence2.Aquifer water

contaminationRemoval 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.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.

* Developments, Projects & Interest