INTRODUCTION
Biomass gasification is the process which converts the wood, crop husks and other agriculture residue into useful gases ( syngas or producer gas) for several uses. The device which is used to do gasification is known as gasifier.
A wood chipper machine plays a crutial role in gasification which convert the wooden logs into small wood chips of desired size. A typical wood chipping machine consists of rotating blades and hammers which converts the raw wood into wood chips of desired size.
Dimensions of gasifier
Length of upper cylinder = 74 cm
Length of lower cylinder = 60.5 cm
Diameter of cylindrical body(outer) = 34.7 cm
Length of feed inlet = 17 cm
Diameter of feed inlet(outer) = 21.3 cm
Thickness of feed inlet = 3.34 mm
Thickness of cylinder (gasifier body) = assume equal to thickness of feed inlet (3.34 mm)
Diameter of air flow pipe (outer) = 60.08 mm
Diameter of air flow pipe (inner) = 49.24 mm
Length of air flow pipe (from blower to burner = 385 cm
Diameter of gas flow pipe (outer) = 11.77 mm
Length of gas flow pipe = 212.5 cm
Length of ignition pipe = 16.3 cm
Diameter of gas removal pipe = 25 mm
Length of gas removal pipe = 49 cm
Distance between two burners = 31 cm
Total no. of burners = 3
Diameter of each burner = 17.5 cm
Height of each burner = 25.5 cm
Calculations
Volume of gasifier = πr^2 h
Radius of gasifier cylinder (r) = d/2
r = (34.7/2) – 3.34
r = 14.01 cm
Total height of gasifier cylinder,h (above grate) = 74 + 30 = 104 cm
Volume = π (14.01)^2 * 104
= 64.09 * 10^-3 cubic m
Density of wood, Albezia lebbeck (siris) = 550 – 660 kg/m^3 ; ( source : wikipedia)
Capacity of gasifier (in kg) = 34.24 kg (considering density 550 kg/m3)
Wood chipping machine
Motor for cutter = 3 hp = 2238 watt
Motor for feeder = 1 hp =746 watt
Size of wood chips
length = 42 mm
diameter = 40 mm (avg.)
Total power consumption of wood chipper = 2.238 + 0.746
= 2.984 kw
~ 3 unit/hr
Machine operating time = 20 minutes
Power consumed by machine = (3/60) * 20
= 1 unit
Weight of wood chips = 10 kg
Wood specification
Wood — Albezia lebbeck (siris)
Type of wood — hardwood
Density of wood — 550 kg/m^3 ( wikipedia)
Moisture content (wet basis) — 35.7 % (need drying)
Colour — light brown
Texture — slightly rough
Challenges faced
The machine getting stuck repeatedly during wood chipping.
Oversized wood pieces caused frequent choking at the cutter blades.
The machine suddenly powered off and didn’t restart for a while. The issue has now been resolved after inspection.
High Moisture Content in Wood Feedstock –
Moisture content was found to be 35.7% (wet basis).
Feeding of wood chips in GASIFIER
04/07/2025 : Test 1
Testing of gasifier with wood chips of higher moisture content
Result
Combustion takes place instead of gasification as lot of air supplied
Blockage of wood chips seen inside the gasifier.
12/07/2025 : Test 2
Gasification with limited supply of air and sealing the bottom of gasifier with water to reduce leakage of gas.
Result:-
Gas not formed properly
White smoke come out from burner
Cause: –
High moisture content of wood chips (35%).
15/07/2025 - 17/07/2025
Drying of wood using different methods:- wood after cutting into smaller sizes had found moisture content upto 35%, that is not reliable for gasification. For proper gasification these wood chips needs to be dried until the moisture content of wood decreases from 35 – 15% or less. For drying of wood following methods were adopted :
- Drying inside chulha :- Drying of wood is done inside the unsued burning chamber of chulha with the help of flue gases allowing them to pass through wood chips. Drying was not done properly, 20% moisture removed in 2hrs but most of the wood chips burned due to extremely high temperature. Temperature of chamber increases upto 300 °C which starts torrefaction.
- Drying above chulha :- Drying of wood is done above the chulha on a pan by just using the heat of flue gases without allowing them to pass through it. Drying was done properly and temperature of drying was 140 – 180 °C and 20% moisture is removed in 6 hrs. But capacity of drying above pan was 2kg per cycle which was time taken.
- Drying of wood chips using dryer:– For drying of wood chips solar flat bed dryer is uses sun’s energy to dry the feed. The temperature of drying was 50 °C and 10% moisture removed in 8hrs. It is also time taking method but has capacity more than 10 kg which reduces time of drying in bulk quantity. In it 20% moisture removal takes 20 hrs of drying.
21/07/2025 Test 3
Trial with 10 kg wood of moisture content ~16%.
Biomass:- wood
Amount of Biomass:- 10 Kg Amount of charcoal:- 500 gm Amount of small wood chips:- 1 Kg Weight of Pot :-1.5 Kg
Amount of Water :- 13.16 Kg (Including Pot).
Starting Time :-3:07 PM.
Flow of gas from Burner :- 3:15 PM
Start burning of burner Time :- 3:17 PM
Burner Stopping Time :-3:27 PM.
Wood not burned completely.
Amount of water left :- 12.82 Kg .(including Pot)
Initial Temperature:- 24°C
Final Temperature:- 68°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 10 k
Calorific value of wood(siris): – 18.5 MJ/Kg (dry) Calorific value with 16% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 18.5 MJ/Kg L : Latent heat of water vapourisation = 2.26 MJ/Kg
NCV = 18.5 x (1- 0.16) – ( 0.16 x 2.26) = 15.178 MJ/Kg
Total input energy of wood = 10 x 15.178 = 151.78 MJ Actual energy of wood used : 2.84 x 15.178 = 43.1 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 0.5 x 28 = 14MJ
Input energy of small dry wood chips = 1 x 18.5 = 18.5 MJ
Total input energy = 151.78 + 14 + 18.5 = 184.28 MJ Energy of wood left unused = 151.78 – 43.1 = 108.68 MJ Actual input energy = 184.28 – 108.68 = 75.6 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 11.32 x 4.2 x 44
= 2091.94 KJ = 2.092 MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
= 0.34 x 2.26
=0.768 MJ
Total output energy = (2.092 + 0.768) MJ
= 2.86 MJ
Efficiency = (total output energy/input energy) x 100
= (2.86/75.6) x 100
= 3.78 %
The gasification efficiency of 3.78% is too low because of the large amount of unburned wood that gets trapped in the gasifier, improperly produced gas, and heat that is released into the atmosphere in the form of flue gases.
22/07/2024 : Test 4
Trial with 10 kg wood of moisture content ~10%.
Biomass:- siris wood (Albizia lebbeck)
Amount of Biomass:- 10 Kg Amount of charcoal:- 3 Kg Weight of Pot :-1.518 Kg
Amount of Water :- 18.992 Kg (Including Pot).
Starting Time :-2:54 PM.
Flow of gas from Burner :- 3:02 PM
Start burning of burner Time :- 3:04 PM
Burner Stopping Time :- 4:19 PM.
Amount of water left :- 16.684 Kg .(including Pot) charcoal left after gasification :- 307 gm
Initial Temperature:- 23°C
Final Temperature:- 95°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 10 kg
Calorific value of wood(siris): – 18.5 MJ/Kg (dry) Calorific value with 10% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 18.5 MJ/Kg L : Latent heat of water vapourisation = 2.443 MJ/Kg
NCV = 18.5 x (1- 0.1) – ( 0.1 x 2.443) = 16.4057 MJ/Kg
Total input energy of wood = 10 x 16.4057 = 164.057 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 3 x 28 = 84MJ
Total input energy = 164.057 + 84 = 248.057 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 15.166 x 4.2 x 72
= 4586.198 KJ = 4.586 MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
= 2.308 x 2.26
=5.216 MJ
charcoal energy = 0.307 x 28 = 8.596 MJ
Total output energy = (4.586 + 5.216 + 8.596) MJ
= 18.398 MJ
Efficiency = (total output energy/input energy) x 100
= (18.398/248.057) x 100
= 7.42 %
gasification efficiency was found 7.42%, which is slightly low cause pot is cooling due to wind.
29/07/2025 - 30/07/2025 : exhibition at vigyan ashram
I took part in a 2 days exhibition where i explained the working of gasifier, pyrolyser and incinerator.
In this I got an opportunity to explain the advantages of gasifier to different curious minds (students and business professionals)
This exhibition was occured every year in the memory of late Dr. s.s. kalbag sir. There I Gained valuable experience in public engagement and technical communication.
04/08/2025 : test 5
Trial with 10 kg wood MC : 10%
Biomass:-siris wood (albizia lebbeck)
Amount of Biomass:- 10 Kg Amount of charcoal:- 3 Kg Weight of Pot :-8.534 Kg
Amount of Water :- 29.430 Kg (Including Pot).
Blower starting time :-7:12 PM.
Flow of gas from Burner :- 7:15 PM
Start burning of burner Time :- 7:18 PM
Burner Stopping Time :- 8:50 PM.
Amount of water left :- 23.565 Kg .(including Pot) charcoal left after gasification :- 453 gm
Initial Temperature:- 23°C
Final Temperature:- 98°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 10 kg
Calorific value of wood(siris): – 18.5 MJ/Kg (dry) Calorific value with 10% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 18.5 MJ/Kg L : Latent heat of water vapourisation = 2.443 MJ/Kg
NCV = 18.5 x (1- 0.1) – ( 0.1 x 2.443) = 16.4057 MJ/Kg
Total input energy of wood = 10 x 16.4057 = 164.057 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 3 x 28 = 84MJ
Total input energy = 164.057 + 84 = 248.057 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 15.031 x 4.2 x 75
= 4734.76 KJ = 4.735 MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
= 5.865 x 2.26
=13.255 MJ
charcoal energy = 0.453 x 28 = 12.684 MJ
Total output energy = (4.735 + 13.255 + 12.684) MJ
= 30.674 MJ
Efficiency = (total output energy/input energy) x 100
= (30.674/248.057) x 100
= 12.37 %
gasification efficiency increased from 7.42% to 12.37% as cooling of pot from wind is stopped by making a cover from tin shed.
11/08/2025: test 6
Trial with 10 kg wood MC : 8%
Biomass:- Sagwan wood (Tectona grandis)
Amount of Biomass:- 10 Kg Amount of charcoal:- 3 Kg Weight of Pot :-8.534 Kg
Amount of Water :- 74.803 Kg (Including Pot).
Blower starting time :-11:00 AM.
Flow of gas from Burner :- 11:03 AM
Burner Igniting Time :- 11:05 AM
Burner Stopping Time :- 11:55 AM.
Amount of water left :- 69.6 Kg .(including Pot) charcoal left after gasification :- 1.473 Kg
Initial Temperature:- 23°C
Final Temperature:- 80°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 10 kg
Calorific value of wood(sagwan): – 19 MJ/Kg (dry) Calorific value with 8% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 19 MJ/Kg L : Latent heat of water vapourisation = 2.443 MJ/Kg
NCV = 19 x (1- 0.08) – ( 0.08 x 2.443) = 17.285 MJ/Kg
Total input energy of wood = 10 x 17.285 = 172.85 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 3 x 28 = 84MJ
Total input energy = 172.85+ 84 = 256.85 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 61.066 x 4.2 x 57
= 14.619MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
= 5.203 x 2.26
=11.758 MJ
charcoal energy = 1.473 x 28 = 41.244 MJ
Total output energy = (14.619+11.758 + 41.244) MJ
= 67.622 MJ
Efficiency = (total output energy/input energy) x 100
= (67.622/256.85) x 100
= 26.33 %
Maximum efficiency found, yellow flame visible.
11/08/2025: test 7
Trial with 7 kg wood MC : 12%
Biomass:- Babool wood (Acacia nilotica)
Amount of Biomass:- 10 Kg Amount of charcoal:- 3 Kg Weight of Pot :-8.534 Kg
Amount of Water :- 62.296 Kg (Including Pot).
Blower starting time :-4:05 PM.
Flow of gas from Burner :- 4:17 PM
Burner Igniting Time :- 4:20 PM
Burner Stopping Time :- 5:07 PM.
Amount of water left :- 60.712 Kg .(including Pot) charcoal left after gasification :- 0.549 Kg
Initial Temperature:- 26°C
Final Temperature:- 83°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 7 kg
Calorific value of wood(babool): – 16.5 MJ/Kg (dry) Calorific value with 12% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 16.5 MJ/Kg L : Latent heat of water vapourisation = 2.443 MJ/Kg
NCV = 16.5 x (1- 0.12) – ( 0.12x 2.443) = 14.227 MJ/Kg
Total input energy of wood = 7 x 14.227 = 99.589 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 3 x 28 = 84MJ
Total input energy = 99.589+ 84 = 183.589 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 52.178 x 4.2 x 56
= 12.272 MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
=1.584 x 2.26
=3.58 MJ
charcoal energy = 0.549 x 28 = 15.372 MJ
Total output energy = (12.272 + 3.58 + 15.372) MJ
= 31.224 MJ
Efficiency = (total output energy/input energy) x 100
= (31.224/183.589) x 100
= 17.01 %
14/08/2025 : test 8 (final test)
Trial with nilgiri wood MC : 13%
Biomass:- Nilgiri wood (Eucalyptus)
Amount of Biomass:- 8.325 Kg Amount of charcoal:- 3 Kg Weight of Pot :-8.534 Kg
Amount of Water :- 62.16 Kg (Including Pot).
Blower starting time :-10:41 AM.
Flow of gas from Burner :- 10:48 AM
Burner Igniting Time :- 10:52 AM
Burner Stopping Time :- 11:51 AM.
Amount of water left :- 58 Kg .(including Pot) charcoal left after gasification :- 1.196 Kg
Initial Temperature of water:- 24°C
Final Temperature of water:- 99°C
Calculation
Input energy: – Weight x Calorific Value
Amount of wood: – 8.325 kg
Calorific value of wood(sagwan): – 19 MJ/Kg (dry) Calorific value with 13% moisture Net calorific value = Cv (dry) x (1- MC/100) – (MC/100 x L)
MC : moisture content Cv (dry) : dry calorific value = 19 MJ/Kg L : Latent heat of water vapourisation = 2.443 MJ/Kg
NCV = 19 x (1- 0.13) – ( 0.13 x 2.443) = 16.213 MJ/Kg
Total input energy of wood = 8.325 x 16.213 = 134.97 MJ
Calorific value of charcoal : – 28 MJ/Kg Input energy of charcoal :- 3 x 28 = 84MJ
Total input energy = 134.97+ 84 = 218.97 MJ
Output energy = m x Cp x ΔT
m= Weight of water left in pot after trial
Cp = Specific heat of water.
ΔT= Temperature difference.
Output energy = 49.466 x 4.2 x 75
= 15.582 MJ
Vapour energy = amount of water evaporated x latent heat of water vapourisation.
= 4.16 x 2.26
=9.402 MJ
charcoal energy = 1.196 x 28 = 33.488 MJ
Total output energy = (15.582 + 9.402 + 33.488) MJ
= 58.472 MJ
Efficiency = (total output energy/input energy) x 100
= (58.472/218.97) x 100
= 26.70 %
