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 AGROINDUSTRIA 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 AGROINDUSTRIA 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/