Coal Gas Technologies - New Initiatives

Ajay K. SinghCentral Institute of Mining and Fuel Research(Erstwhile Central Mining Research Institute)

DHANBAD – 826001ajayabha@yahoo.com

Manuguru, SCCL4 July 2007

Methane in Coal

Organicdebris

Peat Pressure

HEAT

TIME

GasWater

COAL

Anthracite

Bituminous

Lignite

Peat

Mechanism of retention• Unconventional Reservoir.

• In conventional natural gas reservoirs, gas is in free state at high pressure.

• Unlike natural gas reservoirs, most of the gases are adsorbed on the coal surface in CBM reservoir.

• In CBM reservoir only a small percentage is present in free state in the macro-pores.

Adsorption of gases

Two types of adsorption are believed to occur between the gaseous and the solid phases. These two types of adsorption are:

1. Physical Adsorption

2. Chemical or Chemisorption

Physical Adsorption

• Involves intermolecular forces (Van der Waals forces) between the gas (methane) molecules and the solid (coal) molecules.

Chemisorption

•Chemisorption usually involves sharing or transfer of electrons.

Transport of Methane in Coal

• Three Stage process

> Desorption from coal surface.

> Diffusion through micropores.

> Flow in macropores.

FloorNOT TO SCALE

2m

Roof

4.2m

Cover

Safety Hazard in u/g Mines

Opencast Mines

O.B.DUMP

Greenhouse Effect

EARTH

SUN

ATMOSPHEREInfra-red radiation is emitted from the earth’s surface

Solar radiation passes through clear atmosphere

Most solar radiation is absorbed by the earth’s surface and warms

it

Some solar radiation is reflected by the earth to

the atmosphere

Some of the infra-red radiation is absorbed and re-emitted by the

greenhouse gases

Key GHGsCO2 CH4 N2O CFCs

Atm. Conc. ppm ppb ppb ppb

Pre Industrial 280 750 270 0

Present 360 1730 310 0.8

Present rate ofChange/year

0.5% 0.5% 0.2% 0.5%

AtmosphericLifetime

50-200years

8years

120years

50-100years

Short-lived Air PollutantsCO NMHC NOx SO2 Soot

Atm. Conc. ppb ppb ppb ppb NgC/m3

Pre Industrial Unknown

Present 50-500 2-10 0.05-5 0.05-5 0.8

Present rate ofChange/year

Regionally variable

AtmosphericLifetime

2-3months

Hours-weeks

1-2days

A fewdays

Days-weeks

Contributions to Global Warming

CARBON DIOXIDE (63.5%)

HALOGENATED GASES (11.5%)

METHANE (20.5%)

NITROUS OXIDE (4.5%)

N O

Others

CO 2

CH 42N O

Energy from fossil fuels contribute to about 50% of the enhanced greenhouse effect

Measures to reduce greenhouse emissions

• Direct Reductions through:– Energy efficiency improvements

• Demand and supply side– Fuel switching

– Replacing fossil fuels with renewable energy

– Nuclear power??

– CO2 Capture and Storage

• Indirect measures (Kyoto instruments)– Emissions trading

– Joint Implementation actions

– Clean Development Mechanism

Global CO2 geological storage capacity

Note: Economical CO2 Storage potential at a storage cost of 20 US $ per tonne of CO2

Deep Saline Aquifers400-10 000 Gt CO2

Able to store 20 - 530 Years of 2030 Emissions

Depleted Oil & Gas Fields930 Gt CO2

Able to Store 50 Years of 2030 Emissions

Unminable Coal Seams30 Gt CO2

Able to store <2 Years of 2030 Emissions

SnøhvitSleipner

Weyburn

In-Salah

CCS Demonstration Projects

Images Courtesy of BP, Statoil Chevron and PTRC

Typical CBM Well in Production

GasWater

0

20

40

60

80

100

120

0 500 1000 1500 2000 2500

Reservoir Pressure (psi)

% G

as

in P

lac

e

What about Enhanced Gas Recovery ?!?

Affinity of CO2 Adsorption for Coal

CO2

CH4

What if we use CO2 for pressure maintenance?

Reservoir Pressure Psi

Gas

Conte

nt

Methane

CO2

Using CO2 for pressure maintenance can also reduce CO2 emissions (sequestration).

CO2 Injection

Methane Production

Utilisation of VAM

Underground Coal Gasification

Background Paperon

UNDERGROUND COAL GASIFICATIONPrepared by

Ajay K. SinghCentral Mining Research Institute

(Council of Scientific and Industrial Research)Barwa Road, Dhanbad - 826 001, India

Prepared at the initiative ofTECHNOLOGY INFORMATION, FORECASTING AND ASSESSMENT COUNCIL

(Department of Science and Technology)Vishwakarma Bhawan, A-Wing

Shaheedjeet Singh Marg, New Delhi - 110 016, India

July 2006

Steam andAir Injection

Well

GasProduction

Well

Overburden

Water Table

Ground

Coal Seam

Gas

H2 CH4

CO2

N2CO

H2O

Processing

Oxidation

PowerGeneration

What is Gasification?

• Gasification is a general term for various

processes that converts fuels such as

coal and heavy oil, into synthesis gas

(Syngas) by reacting them with steam

and oxygen at elevated temperatures.

• Gasification is NOT combustion.

• Syngas is primarily made up of H2 and

CO.

• Partial Combustion C + O2 = 2CO exothermic

• Combustion C + O2 = CO2 exothermic

C + CO2 = 2CO endothermic

• Water-Gas C + H2O = CO + H2 endothermic

• Hydrogasification C + 2H2 = CH4 exothermic

• Shift CO + H2O = CO2 + H2 exothermic

• Reformation CO + 3H2 = CH4+ H2O exothermic

Gasification (Contd..)

Two boreholes are drilled into the coal seam

UCG - Concept

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

UCG - Concept

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

UCG - Concept

• Oxygen (or Air or Enriched Air)

• Steam

Input of UCG

Typical composition of UCG Dry Syn GasTypical composition of UCG Dry Syn Gas

With no COWith no CO22 capture capture With COWith CO22 capture capture

Calorific Value 2600 Kcal / smCalorific Value 2600 Kcal / sm33 Calorific Value 4000 Kcal / smCalorific Value 4000 Kcal / sm33

Gas Composition

After Blinderman et al. (2002)After Blinderman et al. (2002)

Pre-requisites of UCG (1/5)

UCG is a high risk project. It is advantageous and rather mandatory to investigate various strategic aspects on pilot scale before going for commercial level projects.

Surface features including geography and topography of the UCG block.

Site geology such as faults, fractures, intrusions, dykes, boundary strata composition. Their orientation and extension etc.

Availability of virgin coal seams in the block.

Geotechnical data of coal seams and enclosing strata comprising depth, thickness, lithology, uniformity, dip, coal seam geometry and composition and cleat orientation.

Perophysical data such as porosity, permeability, water and gas saturation and pore pressure etc of coal seam and surrounding strata.

Data on hydrological subsurface characteristics such as aquifer identification, water table, transmissivity, ground water flow rate and direction.

Pre-requisites of UCG (2/5)

Physico-mechanical properties of coal seams and enclosing strata such as bulk density, uniaxial compressive strength, triaxial strength properties, Young's modulus and Poissons's ratio etc.

Chemical analysis of coal including proximate and ultimate analysis, calorific value and maceral analysis.

Special well completion design, high temperature resistant cement, temperature and corrosion resistant downhole casings, flow line and well head assembly with well bore cooling and sustaining high pressure provisions.

Pre-requisites of UCG (3/5)

Identification of an economical and feasible linking technique suitable for the target seam.

Understanding chemical kinetics of the prevalent coal seam conditions and perception of ideal composition of reactants such as air/oxygen and steam.

Cavity growth and subsidence prediction using UCG process models or simulators.

Environmental impact assessment of UCG processes such as treatment and disposal of produced chemicals, gases and water.

Pre-requisites of UCG (4/5)

Availability of drilling and other equipment, compressed air and surface installations.

Economic considerations in respect of UCG process as a whole for its commercialisation.

Pre-requisites of UCG (5/5)

Keeping in view the pre-requisites, the technical

criteria for successful UCG operation can be

grouped in the following three categories:

Coal characterisation.

Geological aspects.

Operational parameters.

Technical criterion for UCG

Shrinking coal, which do not swell on heating are preferred. Caking coals expend on heating and therefore not suited for

UCG. Coals with good permeability and well developed cleat systems

are better for transport of oxidants. Drying and Devolatilization of coal further increase the

permeability. Reactive coals are better choice. Optimum amount of ash in coal reduces the void volume and

minimizes oxygen bypassing. It withholds a considerable portion of sulphur.

VM percentage, hydrocarbons and some aromatic compounds are liberated. This carbonization behaviour is very important for prediction of the yield.

Coal Characterisation

Seam Thickness and water inflow

Roof failure (Sagging or fragmentation). Roof failure is desirable in the sense that the void space in the gasifier gets reduced which offers sufficient resistance to oxygen bypassing. It is damaging for the possibility of increase of water influx and gas leakage.

Geological Aspects

1 m3 of water per ton of gas produced2

3

4

Optimum pressure maintenance is crucial for UCG operation. While low pressure process lowers risk of gas leakage and simultaneously minimizes the possibilities of ground water adulteration, it may also result in higher rates of water influx into the gasifier.

Sweep efficiency which is the coal contacted or reacted over a large area of operation may vary from as low as 10% to a higher value of 90%. A maximum sweep efficiency ultimately results in a minimum operational cost. Sweep efficiency has been found to be a direct function of the well spacing by the Soviets. Sweep efficiency dropped from 83% to 63% with an increase in well spacing from 25m to 40m. Experiments with enriched air resulted in higher sweep efficiencies in comparison to those with air.

Operational Parameters

Different Drilling Technologies

Vertical wellsVertical wells Horizontal, multilateral wellsHorizontal, multilateral wells

UCG and Directional Drilling

Impact

• Supplementing gas resources for energy.

• Dependence on national resources instead of imported oil/gas.

• Clean source of energy.

• May attract Carbon Credit.

• Feedstock for fertilizers and other chemicals.

UN MINEABLE COAL RESOURCES : 210.14 Billion tons

UN MINEABLE LIGNITE RESOURCES : 32.76 Billion tons

TOTAL UNMINEABLE RESOURCES : 242.90 Billion tons

PERCENTAGE OF COAL AMENABLE TO UCG : 30 %

COAL RESERVES AMENABLE TO UCG : 72.87 Billion tons

UCG GAS (considering 2700 m3/ton) : 196.749 Trillion m3

NATURAL GAS EQUIVALENT : 19.67 Trillion m3

CALORIFIC VALUE OF PRODUCED GAS : 3- 5 MJ/m3

CALORIFIC VALUE OF NATURAL GAS = 38 MJ/m3

UCG UCG - Potential- Potential

• Expertise in:– Drilling– In-Situ Combustion– 3-D Seismic– Geological Mapping

• Capability of Handling High Pressures

Demonstrated Expertise & Strength

• UCG Expertise from Skochinsky Institute of

Mining

• IIT, Bombay; IICT, Hyderabad; CIMFR, Dhanbad.

CONSULTANTS, LABORATORY BACK-UP

Experience in:

• Ignition , Tracking Combustion Front

More than 50 air injectors

• Compression & Injection of Oxygen/ Air/ Steam:

Air injection @ 2 million m3/day is already going on in Balol & Santhal field

Similar facilities may be required for UCG

• Flue gas utilisation:

Flue gases producing from heavy oil areas are comparable with the UCG gases

UCG PROJECT AT CHINCHILA, QUEENSLAND, AUSTRALIA

Project objective: Coal deposit characterization programme with pilot burn for continuous and stable gas production in full compliance with environmental guidelines, industrial and health safety regulations for generation of base line for design and construction of full scale syngas fuel power plant.

Project details: covers an area 200 x 300 m with in a mine development lease area of 1.5 sq. km. Coal reserves of 100 mt.Sufficient to last the UCG project for sustaining an IGCC power plant for over 200 years. The project has an EMP and independent audits are made to confirm compliance.The underground gasifier covers an area of 200 X 300 m for coal seam thickness of 10 m at 140 m depth.It is designed to produce 155000 Nm3 /hr. with 63% operational capacity. Can sustain 67 MW combined cycle plant

Coal quality at Chinchila Deposit for UGC:Moisture- 6.8 % Ash- 19.3 %Volatile - 40% Fixed carbon - 33.9%, Total moisture - 10.1%, Relative density 1.50

Gas Resources & Quality of Gas: Link Energy, the developer of the project, has rights to Coal in Queensland alone to sustain power of 5000 MW of base load power for more than 300 years.Gas produced from UG gasifier comes to well head at 3000 C. The gas contains water, hydrocarbons and particulates. The water stream contains commercially recoverable quantities of phenol and Ammonia. The liquid hydrocarbons condensed from the gas have calorific value of 40 MJ/Kg and demonstrate physical properties similar to light crude oil. Commercial Power Generation: The continuous and stable gas production in Chinchila for the past many months, in full compliance with environmental guidelines has provided a reliable basis for construction of a full scale gas facility of 67 MW IGCC project.•The plant is under construction.

Plant OutputComplex plant combining energy and chemical out put.Optimization can be on power out or by-product chemicals.Deeper cooling of gas in process plant- more chemical output, but less gas flow in turbine. Chinchila plant optimized for power generation. Economics need to be worked out before hand. Once examination based on market study of power & chemicals is accomplished, plant outputs can be adjusted to get maximal commercial returns.

Chinchila project outputsProduct Output PowerPower 67 MWGas 800mil Nm3/yrhydrocarbons 15,000 te/yrphenol 3,700 te/yrAnhydrous NH3 1,500 te/yrClean water 200 mega lit./yr