Experimental Characterisation of a
Downdraft Gasifier Fueled with
Woodchar/Woodchips Mixtures
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
Biomass gasification is basically a conversion of solid fuels
(wood, wood-waste, agricultural residues, charcoal, etc.) into a
combustible gas mixture normally called Producer Gas.
The process is typically used for various biomass materials and it
involves partial combustion of such biomass.
Partial combustion process occurs when air supply (O2) is less
than adequate for the combustion of biomass to be completed.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
Biomass is usually composed of the elements carbon, hydrogen
and oxygen. In addition there may be nitrogen and sulphur, but
since these are present only in small quantities they will be
disregarded in the following discussion.
In the types of gasifiers considered here, the solid fuel is heated
by combustion of a part of the fuel. The combustion gases are
then reduced by being passed through a bed of fuel at high
temperature.
In complete combustion, carbon dioxide is obtained from the
carbon and water from the hydrogen. Oxygen from the fuel will of
course be incorporated in the combustion products, thereby
decreasing the amount of combustion air needed.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
Oxidation of carbon, or “combustion”, is described by the following
chemical reaction formulae (auto thermal gasification):
C + O2
CO2
- 393.8 kJ/mol (exo-thermic)
C + ½ O2
CO
- 123.1 kJ/mol (exo-thermic)
In all types of gasifiers, CO2 and H2O (vap.) are converted (reduced)
as much as possible to CO, H2 and CH4 , which are the main
combustible components of producer gas.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
The most important reactions that take place in the reduction zone of a gasifier
between the different gaseous and solid reactants are the following
C + CO2
2 CO
C + H2O
CO2 + H2
C + 2 H2
CO + H2
+ 118.5 kJ/mol (water gas reaction, endo-th.)
CO + H2O + 40.9 kJ/mol (water gas shift reaction, endo-th.)
CH4
- 87.5 kJ/mol (methanisation, exo-thermic)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
+ 159.9 kJ/mol (Boudouard, endo-th.)
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
Despite the substoichiometric conditions prevailing everywhere, oxidation of
CO and H2 may locally take place according to:
CO + ½ O2
H2 + ½ O2
CO2
H2O
- 283.9 kJ/mol (exo-thermic)
- 285.9 kJ/mol (exo-thermic)
Though they produce heat, to the advantage of the auto-thermal gasification,
they are undesired because the producer gas heat-value is lowered.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification: Fundamentals
The equilibrium of above seen “water gas” (heterogeneous) and “water gas
shift” (homogeneous) reactions largely govern the final gas composition.
On the other hand, the equilibrium composition of the gas will only be
reached when the reaction rate and the time for reaction are adequate.
Below 700 °C the reaction rates proceed so slowly that the product gas
composition is “frozen” : once formed, the gaseous products do not further
react with each other. Unfortunately, this applies also to the tars, which
build up in the gas, since they cannot undergo any “reduction”.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification at DIMSET/SCL
Manufacturer:
ANKUR Ltd.
located near the ancient
“Sama Jakat Naka”
Baroda-390008, Gujarat,
India
web site: www.
ankurscientific.com
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification
at DIMSET/SCL
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
To a Gas
Engine
Or Gas
Turbine
Biomass Gasification
at DIMSET/SCL
Conceptual Sequence of Processes
from Biomass to End Products
Product Gas
Cleaning Equipment
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Biomass Gasification at DIMSET/SCL
Fuel Parameters, Gasifier Performance, Product Gas, Slag, Emissions Monitoring
- Physico-chemical characterisation of fuel (woodchips and charcoal-woodchips mix)
- Air/Fuel Equivalence Ratio
- Inner temperature profile (overall gasifier)
- Pressure drop (@ sand filter)
- Product gas temperature (@ gasifier outlet)
- Water temperature (@ scrubbers)
- Product gas flow rate (@ gasifier outlet)
- Water pressure (@ scrubbers)
- Inner gasifier pressure
- Water flow rate (@ scrubbers)
- “Clean” product gas chemical composition
- Condensate chemical composition
- Slag composition and mass flow rate
- Condensate mass flow rate
●
●
●
●
●
●
- Exhaust gas composition and mass flow rate (@ gas engine outlet)
●
- Co-generation thermal power (@ overall equipment and gas engine)
●
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Temperature Distributions for Varying Fuel Typologies
HEARTH LOAD OPTIMISED
FOR MINIMUM TAR CONTENT
Height from platform level (cm)
2500
Biomass Gasification
Serie1
at DIMSET/SCL
TC3
Wood@32% hu
2000
S-2
Serie2
Wood@25% hu
1500
S-3
Serie3
TC2
1000
TC1
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
S-4
Serie4
W@30% Coal
500
TC4
0
0
1° Convegno SIBA
Salerno, 22-23/10/07
W@15% Coal
500
1000 1500 T (°C)
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Temperature Distributions for Varying Fuel Typologies
Biomass Gasification
S-1
Serie1
at DIMSET/SCL
TC3TC3
Height from platform level (cm)
2500
HEARTH LOAD OPTIMISED
FOR MAX GAS ENERGY
Wood@32% hu
2000
S-2
Wood@25%
S-2
hu
Serie2
1500
TC2TC2
1000
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
S-4
TC1TC1
W@30%Serie4
Coal
S-4
500
Wood@30% Coal
TC4TC4
0
0
1° Convegno SIBA
Salerno, 22-23/10/07
Wood@25%
S-1
hu
Wood@32% hu
S-3
S-3
W@15%Serie3
Coal
Wood@15% Coal
1000
2000 T (°C)
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Product Gas Heat Values for Varying Fuel Typologies
Heat Value Hi (kCal/Nm3)
Product Gas Heat Values
S-2
Serie1
S-2
2000
Wood@25% hu
Wood@25% hu
1500
S-2
Serie2
1000
Wood@15%S-3
Coal
Wood@15%Coal
500
TC1TC1
0
S-2
Serie3
0
0.1
0.2
0.3
0.4
Superficial Velocity (m/s)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
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0.5
0.6
Wood@30%S-4
Coal
Wood@30%Coal
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Product Gas Flow Rate for Varying Fuel Typologies
Product Gas Flow Rate
Syngas Flow Rate
(Nm3/s)
60
50
Serie1
S-2
40
Wood@25% hu
30
S-3
Serie2
20
Wood@15% Coal
10
TC1TC1
0
0
0.1
0.2
0.3
0.4
Superficial Velocity (m/s)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
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0.5
0.6
S-4
Serie3
Wood@30%Coal
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Gas Thermal Power for Varying Fuel Typologies
Gas Energy Flow Rate (kCal/h)
Serie1
S-2
Gas Energy (kCal/h)
50000
Wood@25% hu
40000
30000
S-3
Serie2
20000
Wood@15% Coal
10000
TC1TC1
0
0
0.1
0.2
0.3
0.4
Superficial Velocity (m/s)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
0.5
Serie3
S-4
0.6
Wood@30% Coal
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Electric Power Generation for Varying Fuel Typologies
Electric Power (kW)
Electric Power (kW)
16
S-2
Serie1
14
Wood@25% hu
12
10
8
S-3
Serie2
6
Wood@15% Coal
4
2
0
0
0.1
0.2
0.3
0.4
Superficial Velocity (m/s)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
0.5
Serie3
S-4
0.6
Wood@30% Coal
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Tar and Particulate Levels for Varying Fuel Typologies
Tar + Particulate in Gas
8000
S-2
Serie1
Tar + Particulate
(mg/m3)
7000
Wood@25% hu
6000
5000
4000
S-3
Serie2
3000
Wood@15% Coal
2000
1000
0
0
0.1
0.2
0.3
0.4
Superficial Velocity (m/s)
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
0.5
0.6
Serie3
S-4
Wood@30% Coal
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Tar and Particulate Levels for Varying Fuel Typologies
Tar + Particulate (mg/m3)
Tar + Particulate in Gas
S-2
Serie1
400
350
300
250
200
150
100
50
0
Wood@25% hu
S-3
Serie2
Wood@15% Coal
S-4
Serie3
0
0.1
0.2
0.3
0.4
0.5
0.6
Wood@30% Coal
Superficial Velocity (m/s)
IN ORDER TO QUANTIFY THE LOWER CONCENTRATIONS OF TARS,
THE VALUES REPORTED ARE LIMITED TO SV HIGHER THAN 0.25 M/S
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Conclusions
The experimental results above presented can be considered as safely
demonstrative of the actual possibility, provided by the fixed-bed downdraft
gasification technology, of successfully pursuing a widespread territorial
distribution of micro CHP (combined heat and power) generating plants
fueled by wood/charcoal mixtures.
One main outcome of the investigation has been that of unequivocally
assessing the great potential, for a given gasifier technology, residing in its
functional optimisation, to be achieved by imposing correct operative
parameters, most important among all, the hearth load.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Conclusions
Without the need of re-designing or complicating an intrinsically simple and
reliable basic technology, the performance parameters such as:
• power plant efficiency
• product gas yield
• and, most importantly, tar and particulate content in the gas
can be optimised by means of a careful functional-variables setting.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/
Conclusions
The outcome of pursuing a suitable mixing of woodchips with charcoal has
turned out extremely beneficial under all respects:
• gas yield and gas energy flow, increasing almost proportionally with the
increase of charcoal percentage
• decrease of tar content in the product gas, thanks to the higher hearth
temperatures
• “thermal nobilitation” of lower heat content woodchips, possibly even of
green waste too
From this perspective, a renewed interest in charcoal production, with upto-date technologies (e.g. auto-thermal retorts) could be conceived, with
interesting environmental and economic returns.
1° Convegno SIBA
Salerno, 22-23/10/07
SOCIETA’ ITALIANA BIOENERGIA E
AGROINDUSTRIA
F. Pittaluga – University of Genoa
DIMSET/SCL – Savona Combustion Lab.
[email protected] - http://proxy.sv.inge.unige.it/SCL/