DESIGN AND DEVELOPMENT OF A

NATURAL DRAFT BIOMASS

GASIFIER

by

R.KRISHNA KUMAR

OBJECTIVE

� DESIGN OF NATURAL DRAFT

GASIFIER (NDG)

� FABRICATION OF NDG

� PERFORMANCE EVALUATION

� FINE TUNING FOR OPTIMUM

PERFORMANCE

COURSE OF WORK

� Maximum Size of Fuel suitable for NDG

� Thermal Efficiency variation in

� Batch Process

� Continuous Process

� Influence of different Fuels on Performance

N D G - BASICS & PRINCIPLES

� Operates under the principle of “ Operates under the principle of “ Chimney Effect Chimney Effect ””

� Natural draft caused by density difference

� No blower is required for the operation

� Automatically takes the required quantity of air for

Gasification

� Convey the Producer Gas formed by Gasification - Naturally

���� Reduced fuel consumption compared to traditional chulas

UNIQUE FEATURES COMPARED TO

CONVENTIONAL SYSTEMS

PRINCIPLE

OF

OPERATION

ADVANTAGES - N D G

� Pretreatment of fuel viz., Sizing – Not Necessary

� Effective fuel utilization

� Abates Indoor air pollution –

* Over Two Billion people cook slowly on smoky

inefficient wood chulas

* Smoke from Traditional Chula is equal to smoking

20 cigarettes each day

* Avoids “Indoor smoke” and “Infant Underweight”

caused by CO poisoning

� Improvement of 1% in the thermal efficiency of a

traditional chulas will result in saving of about 3 million

tonnes of firewood every year

N D G A VIABLE OPTION INDEED

DESIGNED

DIMENSIONS

OF

NDG

Secondary Air

Supply

Hopper

Primary Air Supply

Ash Pit

0.3 m

0.58 m

0.25 m

Front View of

N D G

Top View of

N D G

TEST CONDUCTED

Water Boiling Test – VITA TEST

� Batch Type process

� Fuel (Prosopis Juliflora)

Wood size varied from

* 10 mm to 90 mm ( diameter )

* Fixed length of 300 mm

PHOTOGRAPH DEPICTING

TESTED WOOD SIZES

Fuel : Prosopis juliflora

Flame Generated

photoGlowing Bed

VITA Test –

Boiling Water

Damper fully

open

Damper controlled

operation

Wood Length 300mm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

10 20 30 40 50 60 70 80 90

Wood Diameter (mm)

k

g o

f c

ha

rco

al / k

g o

f w

oo

d

Variation in kg of charcoal / kg of wood with Wood size

Wood length 300mm

0

20

40

60

80

100

120

140

160

180

10 20 30 40 50 60 70 80 90

Wood Diameter (mm)

Are

a H

ea

t lo

ad

ing

(k

g/h

/m2

)

0

20

40

60

80

100

120

Co

mb

us

tio

n E

ffic

ien

cy

(%

)

Area Heat loading Combustion Efficiency

Variation in Combustion Efficiency and Area Heat Loading

with Wood size

Wood Length 300mm

0

5

10

15

20

25

30

10 20 30 40 50 60 70 80 90

Wood Diameter (mm)

Ov

era

ll T

he

rma

l E

ffic

ien

cy

(%

)

0

1

2

3

4

5

∆∆ ∆∆T

/ ∆∆ ∆∆

t (

oC

/min

)

Overall Thermal Efficiency DT/ Dt∆ T / ∆t

Variation in Overall Thermal Efficiency and Rise in water

temperature per unit with time to Wood size

Wood Length 300mm

0

20

40

60

80

100

10 20 30 40 50 60 70 80 90

Wood Diameter (mm)

Co

mb

us

tio

n E

ffic

ien

cy

(%

),

O

ve

rall

Eff

icie

nc

y (

%)

0

1

2

3

4

5

Po

we

r R

ati

ng

(k

W)

Combustion Efficiency Overall Efficiency Power Rating

Variation in Combustion Efficiency, Overall Thermal Efficiency and

Power Rating with respect to Wood size

0

200

400

600

800

1000

1200

10 20 30 40 50 60 70

Time (min)

Tem

pera

ture

(o

C)

1 2 3 4

Temperature profile of NDG

Heat Balance of NDG

NDG Heat Gain

34.11%

Vessel Heat Gain

0.09%

Heat in Charcoal

1.30%

Heat loss by burning

Hydrogen

9.11%

Heat loss due to

moisture in fuel

4.09%

Heat loss from

Vessel

1.26%

Unaccounted Heat

Loss

1.48%Useful heat

24.68%

Heat loss in Flue gas

8.37%

NDG Surface Heat

loss

15.51%

CONTINUOUS OPERATION

1 2 3 4

Wood weight

(kg)4.15 3.85 3.85 3.95

Weight of Charcoal

(kg)0.35 0.4 0.4 0.4

Water Evaporated

(kg)4.765 5.872 6.272 6.664

∆T / ∆t

(oC/min)2.13 2.275 2.44 2.64

Overall Efficiency

(%)25.06 32.5 34.41 35.19

EXPERIMENTAL STUDIES WITH

DIFFERENT FUELS

Fuel

Overall

Efficiency

(%)

Combustion

Efficiency

(%)

Power

Rating

(kW)

Prosopis

Juliflora24.68 87.34 3.12

Casuarina

Wood22.2 91.15 3.92

Workshop

Wood21.31 91.95 4.08

Coconut Shell 26.68 92.58 4.99

Groundnut

Shell17.9 91.4 2.8

IMMEDIATE APPLICATION OF NDG

� Manual Dyeing Units

� Tea Leaves Drying

� Canteen

� Bakeries

� Households

OBSERVATIONS

� Better Conversion Efficiency

� Fuel Flexibility

� Low Maintenance

� Related Environmental Benefits

� Scope to be a Popular Interim Measure for Pollution Mitigation

DISCUSSION GROUPS

Established contact and working member of

www.stoveslistserve.org

www.gasificationlistserve.org

www.repp.org

Based on discussions, details of the project is posted on the web in the

following sites

www.trmiles.com/stoves/kumar/KK%20NDG.pdf

www.repp.org/discussiongroups/resources/gal2003.htm

www.repp.org/discussiongroups/resources/kumar/ndg.htm

CONCLUSION

� Operated without any external power supply

� Nearly 50% fuel savings was achieved compared to

Conventional chulas in Batch process

� NDG is designed to suit different Biomass fuels that are

available locally – Fuel Versatile

� Continuous process of operation provided 35.19% which is

just 10% less than the Overall Efficiency of Downdraft Gasifier

� Fuel with Higher Moisture content can also be used

LIST OF PUBLICATION

Krishna Kumar R, Venkata Ramanan M, Sethumadhavan R,

Renganarayanan S (2004), ‘Replacement of Conventional Fuels

with Biomass Gasifier for Cooking Applications’ accepted for

presentation at International Engineering Conference (Mutah

2004). Mutah University, Jordan