1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Experimental Characterisation of a Downdraft Gasifier Fueled with Woodchar/Woodchips Mixtures
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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 + 159.9 kJ/mol (Boudouard, endo-th.) C + H2O CO + H2 + 118.5 kJ/mol (water gas reaction, endo-th.) CO2 + H2 CO + H2O + 40.9 kJ/mol (water gas shift reaction, endo-th.) C + 2 H2 CH4 - 87.5 kJ/mol (methanisation, exo-thermic)
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Biomass Gasification: Fundamentals
Despite the substoichiometric conditions prevailing everywhere, oxidation of CO and H2 may locally take place according to:
CO + ½ O2 CO2 - 283.9 kJ/mol (exo-thermic) H2 + ½ O2 H2O - 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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Biomass Gasification at DIMSET/SCL
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Biomass Gasification at DIMSET/SCL
To a Gas EngineOr Gas Turbine
Conceptual Sequence of Processes from Biomass to End Products
Product GasCleaning Equipment
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Biomass Gasification at DIMSET/SCL
HEARTH LOAD OPTIMISED FOR MINIMUM TAR CONTENT
Temperature Distributions for Varying Fuel Typologies
Wood@32% hu
Wood@25% hu
W@15% Coal
W@30% Coal
S-2
S-3
S-4
TC3
TC2
TC1
TC4
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Biomass Gasification at DIMSET/SCL
HEARTH LOAD OPTIMISED FOR MAX GAS ENERGY
Temperature Distributions for Varying Fuel Typologies
Wood@32% hu
Wood@25% hu
W@15% Coal
W@30% Coal
S-1
S-2
S-3
S-4
TC3
TC2
TC1
TC4
S-1
Wood@32% hu
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
TC3
TC2
TC1
TC4
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Product Gas Heat Values for Varying Fuel Typologies
TC1TC1
S-2
S-3
S-4
Wood@25% hu
Wood@15%Coal
Wood@30%Coal
Product Gas Heat Values
0
500
1000
1500
2000
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Hea
t Val
ue H
i (kC
al/N
m3)
Serie1
Serie2
Serie3
S-2
S-2
S-2
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Product Gas Flow Rate for Varying Fuel Typologies
TC1TC1
Product Gas Flow Rate
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Syng
as F
low
Rat
e (N
m3/
s)
Serie1
Serie2
Serie3
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30%Coal
S-2
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Gas Thermal Power for Varying Fuel Typologies
TC1TC1
Gas Energy Flow Rate (kCal/h)
0
10000
20000
30000
40000
50000
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Gas
Ene
rgy
(kC
al/h
)
Serie1
Serie2
Serie3
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Electric Power (kW)
024
68
1012
1416
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Elec
tric
Pow
er (k
W)
Serie1
Serie2
Serie3
Electric Power Generation for Varying Fuel Typologies
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Tar + Particulate in Gas
01000200030004000
5000600070008000
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Tar +
Par
ticul
ate
(mg/
m3)
Serie1
Serie2
Serie3
Tar and Particulate Levels for Varying Fuel Typologies
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
1° Convegno SIBA Salerno, 22-23/10/07
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
Tar + Particulate in Gas
050
100150200250300350400
0 0.1 0.2 0.3 0.4 0.5 0.6
Superficial Velocity (m/s)
Tar +
Par
ticul
ate
(mg/
m3)
Serie1
Serie2
Serie3
Tar and Particulate Levels for Varying Fuel Typologies
S-2
S-3
S-4
Wood@25% hu
Wood@15% Coal
Wood@30% Coal
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
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
F. Pittaluga – University of GenoaDIMSET/SCL – Savona Combustion [email protected] - http://proxy.sv.inge.unige.it/SCL/
SOCIETA’ ITALIANA BIOENERGIA E AGROINDUSTRIA
ConclusionsThe 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 up-to-date technologies (e.g. auto-thermal retorts) could be conceived, with interesting environmental and economic returns.