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Biomass> (Gasification) > Producer Gas

conversion of solid fuels into combustible gas mixture

called producer gas (CO+H2+CH4). Involves partialcombustion of biomass

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+ StoichiometricAIR+ SUBStoichiometricAir+ SUBStoichiometricAir

SUB

Stoichiometric

Air

COMBUSTION

GASIFICATION

PYROLYSIS

CARBONISATION

E R = 1

ER = 0.3

ER = 0.1

ER = 0.1

P R I N C I P L E

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P R I N C I P L E - S I M P L I F I E D

Solid

Fuels

+Excess Air

Actual

Combustion

Stoichiometric

Air

Ideal

Combustion

Sub-

Stoichiometric

Air

Gasification

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GASIFICATION PROCESS

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H O W O L D O R N E WG A S I F I C A T I O N T E C H N O L O G Y I S ?

1 8 3 91s tCommercial Gasi f ierInstalled( updraft )

1 9 2 0Oil fuel led sys tems took over Gasi f ier

1 9 4 2 ( During 2nd World War )

Thousands of Gasi f iers used in Europe

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1 9 5 0

Gasi f iers decomm issionedWidespread avai labi l i ty o f l iqu id fuels.

1 9 7 0 sEnergy Cris is b rough t renewed in terest.

2 0 0 0 sIncreasedFocus onBiomassGasif icat ion

Regarded as Clean & Green Energy

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3 E N G I N E E R I N G I N D U S T R Y

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4 PROCESSES IN GASIFICATION

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Moisture must be

removed

Failure to remove

moisture results in the

inability to produce

clean fuel.

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Occurs when the wood chips are

heated without enough oxygen to

burn.

Does not begin until the

temperature reached about 550 K.

Causes the wood chips to

decompose into tar and charcoal. Tars are burned off, leaving

charcoal with a high carbon

content.

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exothermic combination of

hydrocarbons with oxygen.

oxidation temperature of about

14500C

main reactions :

C + O2 = CO2 (+ 393 MJ/kg mole)

2H2 + O2 = 2H2 O (- 242 MJ/kg mole)

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Reverts completely combusted

hydrocarbons into a form that can beused as fuel.

Opposite of combustion process-

endothermic removal of oxygen from

hydrocarbons.

Reduction in a gasifier occurs when

CO2and water vapor flows through

heated charcoal.

The heated carbon removes the

oxygen from both the CO2 and the

H2O.

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(i) Fixed Bed Gasifier

- up draught gasifier

- downdraught gasifier

- cross draught gasifier

(ii) Fluidized Bed Gasifier

Types of Gasifier

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Counter-current fixed bed ("updraft") gasifier Carbonaceous fuel (e.g. coal or

biomass) through which the

"gasification agent flows in

counter - current configuration.

The ash is either removed dry

or as a slag.

Thermal efficiency is high.

Gas exit temperatures are low.

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U

P

D

R

A

F

T

F u e l

G

A

S

A

I

R

a

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A s h Z o n e

Oxidation Zone C + O 2 = C O 2

G a s s p a c eDrying & Carbonisation Zone

Primary Reduction Zone

C + H 2 O = C O + H 2

C + 2 H 2 O = C O 2 + 2 H 2C + C O 2 = 2 C O

Secondary Reduction Zone

C + C O 2 = 2 C OC + 2 H 2 O = C O 2 + 2 H 2

Producer

Gas

Fuel

A i r

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C t fi d b d ("d d ft") ifi

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Co-current fixed bed ("down draft") gasifier

Gasification agent gas flows in

co-current configuration with

the fuel.

The produced gas leaves the

gasifier at a high temperature.

Most of this heat is often

transferred to the gasification

agent added in the top of the

bed.

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D

O

W

N

D

R

A

F

T

F u e l

G

A

S

A I RA I R

b

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A s h Z o n e

D r y i n g

Reduction Zone

C + H 2 O = C O + H 2

C + 2 H 2 O = C O 2 + 2 H 2

C + C O 2 = 2 C O

P y r o l y s i s

Producer

Gas

Fuel

Oxidation Zone C + O2 = C O 2A i r

G

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-

GA

SIF

ICA

TIO

N

P

RO

C

E

S

S

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C R O S S D R A F T G A S I F I E R

Air enters from one side of

gasifier reactor and taken out

from other side

Simplest gasifier designs

Quick start time and

reaches high temperatures

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Pressured air is passedthrough distributor plate and

the velocity of air is

progressively increased.

To support the entire weight

of the bed by the fluid drag

on the bed particles. This moving mass of solid

particles is called a fluidized

bed.

A D V A N T A G E S A N D

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N

o

Gasifier

Type Advantage Disadvantages

1 Updraft

- Low pressure drop

- good thermal efficiency

- little tendency towards

slag formation

- Great sensitivity to tar and

moisture content of fuel

- poor reaction capability with

heavy gas load

2 Downdraft

- Flexible adaptation of

gas production to load

- low sensitivity to

charcoal dust and tar

content of fuel

- Design tends to be tall

- not feasible for very small

particle size of fuel

3 Crossdraft

- Short design height

- very fast response time

to load

- flexible gas production

- Very high sensitivity to slag

formation

- high pressure drop

A D V A N T A G E S A N DD I S A D V A N T A G E S

U D & D D

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U p D r a f t D o w n D r a f t High Gasification High Moisture Content

Fuel can be used.

Low Gas Temperature

High Tar

Extensive Gas Cleaning

required for Power

Generation

Almost T A R F R E E G A S

Suitable for Power Generation

Presence of Ash & Dust

Particles

Strict in Fuel Sizing

Moisture < 1 5 %

High Gas Outlet Temperature

Lower Gasification

M O S T C O M M O N L Y U S E D ARE U D & D DA C O M P A R I S O N

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Typical Composition of Producer Gas

CO = 1 8 - 2 0 %

H2 = 1 8 - 2 0 %

CH4 = 2 - 4 %

CO2 = 1 0 - 1 2 %

N2 = R e s t %

Calorific

Value

1 000 - 1 200kcal / nm3

Low Btu

Gas

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O O

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W O O D

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W O O D C U T T O S I Z E

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W O O D C U T T O S I Z E

C O C O N U T S H E L L

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C O C O N U T S H E L L

B R I Q U E T T E D B I O M A S S

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Bulk Densit : 6 0 0 8 0 0 k / m 3

B R I Q U E T T E D B I O M A S S

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T H E R M A L E L E C T R I C A L

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T h l A l i i

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T h e r m a l A p p l i c a t i o n s

Hot Air Generators Dryers

Boilers

Thermic Fluid Heaters

Ovens

Furnaces & Kilns

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H E A T C O N T E N T

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Thermal Energy of the order of

4 . 5 to 5 . 0 M J / m3

Flame temperatures as high

as 1 2 0 0 C can be

obtained by optimal pre -

mixing of air with gas.

H E A T C O N T E N T

B L E A C H I N G

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B L E A C H I N G

C a n R e p l a c eI n e f f i c i e n t u s a g e

o f F i r e w o o d C H E M I C A L P R O D U C T I O N

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C H E M I C A L P R O D U C T I O N

N

oParameters Conventional With Gasifier

%

Reduction

1

Sp. Fuel Consumption

kg wood / kg 0 . 4 1 0 . 2 2 4 6 . 3

C O C O O N - C O O K I N G O V E N

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C O C O O N C O O K I N G O V E N

N

oP a r a m e t e r s Conventional With Gasifier

%

Reduction

1Sp. Fuel Consumption

kg wood / kg cocoon2 . 2 6 1 . 0 5 7

2

Water Consumption

lit / kg cocoon 3 . 0 2 5 2 . 1 6 5 2 8 . 4

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No P a r a m e t e r s Conventional With Gasifier

%

Reduction

1Sp. Fuel Consumption

kg wood / kg offabric4 . 9 1 2 . 2 7 5 2 . 4

2

Water Consumption

lit / kg fabric 1 7 . 3 1 1 3 . 5 4 2 1 . 8

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S C H E M E

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S C H E M E

Agricultural

Waste GasificationProcess Producer Gas

Internal

Combustion

Engine

Air at High

Temperature

Electricity Alternator

Mechanical

Power

P G t i

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P o w e r G e n e r a t i o n :

Pumping and Irrigation

Village electrification

Captive power ( industries )

Grid - fed power from energy

plant installed on wastelands

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5

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Consumes around 300 kg wood / Body

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W H Y G A S I F I C A T I O N ?

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W H Y G A S I F I C A T I O N ?

C l e a n T e c h n o l o g y( C O 2 N e u t r a l )

G r e e n T e c h n o l o g y( R e n e w a b l e )

D e c e n t r a l i z e d