Producer Gas

This work presents an experimental study of the gasification of a wood biomass in a moving bed downdraft reactor with two-air supply stages. This configuration is considered as primary method to improve the quality of the producer gas, regarding its tar reduction. By varying the air flow fed to the gasifier and the distribution of gasification air between stages (AR), being the controllable and measurable variables for this type of gasifiers, measuring the CO, CH4 and H2 gas concentrations and through a mass and energy balance, the gas yield and its power, the cold efficiency of the process and the equivalence ratio (ER), as well as other performance variables were calculated. The gasifier produces a combustible gas with a CO, CH4 and H2 concentrations of 19.04, 0.89 and 16.78% v respectively, at a total flow of air of 20 Nm3 h−1 and an AR of 80%. For these conditions, the low heating value of the gas was 4539 kJ Nm−3. Results from the calculation model show a useful gas power and cold efficiency around 40 kW and 68%, respectively. The resulting ER under the referred operation condition is around 0.40. The results suggested a considerable effect of the secondary stage over the reduction of the CH4 concentration which is associated with the decreases of the tar content in the produced gas. Under these conditions the biomass devolatilization in the pyrolysis zone gives much lighter compounds which are more easily cracked when the gas stream passes through the combustion zone.► Obtained results an important for a better phenomenological understanding of processes occurring in two stage gasification reactors. ► The air flow is the fundamental parameter in the operation of downdraft gasifiers. ► CH4 reduction is associated with a decreases in the tar content. ► An enhancement in the thermal cracking of tar is carried out in the two-air downdraft gasifier.

Producer gas derived from biomass gasification can be used as an alternative to fossil fuel for generating power. Low heating value and high CO content are the main obstacles for using it via a combustion process, leading to require a special combustor design to achieve its efficient burning. This study aims to investigate premixed combustion characteristics of producer gas in a cyclonic flow combustion chamber under varying from single to four burners using 3D computational fluid dynamics simulation. Combustion process is operated at a fixed thermal power input of about 90 kW with respect to injection of air-fuel mixture at the ambient condition. A 17 species skeletal reaction scheme with 73 chemical reversible reactions is used for chemical interactions. The numerical result is well agreed with the experimental data. Through all studied results it could be concluded that the peak combustion temperature, which is higher than 1600 K, is obtained for the case of multiple burners, except for the single burner case. The lowest CO formation is obtained for the case of four burners, which is approximately 243 ppm while lowest NO formation is obtained for the single burner case, which is approximately 17 ppm.

Flameless combustion is considered as a flexible and efficient combustion process for low heating value gas fuel. This paper presents numerical simulations of premixed flameless combustion using producer gas as a fuel. Different initial conditions of the premixed fresh reactant (air/fuel mixture) and dilution levels are taken into account for the investigation. The numerical simulations were investigated using a network of chemical reactor models with the detailed reaction mechanism of GRI-Mech 3.0. A threshold dilution level for flameless combustion fuelled by producer gas was determined. The numerical results show that dilution of the fresh reactant with hot combustion products and initial fresh reactant temperature play important roles in flameless combustion formation and its auto-ignition behaviour, rather than equivalence ratio of the fresh reactant. In the flameless combustion regime, temperature and chemical concentrations were reduced while chemical kinetics process was decelerated, resulting in delay of the auto-ignition process. KEYWORDS auto-ignition, dilution ratio, flameless combustion, gas recirculation, producer gas 1 | INTRODUCTION Flameless or moderate or intense low oxygen dilution combustion 1 is a promising combustion technology to suppress NOx emissions with high thermal efficiency of the combustion system. 2 Flameless combustion takes place under high reactant temperature and dilution environment where molar fraction of oxygen before the reaction of air/fuel mixture is less than 5% to 8%. 3-5 In flameless combustion mode, the peak flame temperature is controlled and the temperature gradient between the initial and maximum state is lower than the traditional combustion mode. This results in a decrease of thermal nitrogen oxide formation. 6 High-temperature environment (above the auto-ignition temperature of the fuel) allows air and fuel mixture to ignite spontaneously within the entire combustion volume, leading to complete oxidation and reduced fuel consumption, thus enhances the combustion efficiency. 2 These phenomena can be achieved when the incoming air and fuel mixture is preheated and diluted prior to the reaction. For this reason, recirculation of hot flue gas into the fresh air and/or fuel streams is often used. 7 Wünning and Wünning 8 proposed the gas recirculation factor K V > 3 (which calculated using a ratio of internal flue gas recirculation to a sum of combustion air and fuel flow rate) with furnace temperature higher than the auto-ignition temperature of the fuel to describe the regime of flameless combustion. Cavaliere and De Joannon 1 summarized that flameless combustion is bounded by inlet temperature of air/fuel mixture and combustion temperature, which

Flameless combustion is considered as a flexible and efficient combustion process for low heating value gas fuel. This paper presents numerical simulations of premixed flameless combustion using producer gas as a fuel. Different initial conditions of the premixed fresh reactant (air/fuel mixture) and dilution levels are taken into account for the investigation. The numerical simulations were investigated using a network of chemical reactor models with the detailed reaction mechanism of GRI-Mech 3.0. A threshold dilution level for flameless combustion fuelled by producer gas was determined. The numerical results show that dilution of the fresh reactant with hot combustion products and initial fresh reactant temperature play important roles in flameless combustion formation and its auto-ignition behaviour, rather than equivalence ratio of the fresh reactant. In the flameless combustion regime, temperature and chemical concentrations were reduced while chemical kinetics process was decelerated, resulting in delay of the auto-ignition process. KEYWORDS auto-ignition, dilution ratio, flameless combustion, gas recirculation, producer gas 1 | INTRODUCTION Flameless or moderate or intense low oxygen dilution combustion 1 is a promising combustion technology to suppress NOx emissions with high thermal efficiency of the combustion system. 2 Flameless combustion takes place under high reactant temperature and dilution environment where molar fraction of oxygen before the reaction of air/fuel mixture is less than 5% to 8%. 3-5 In flameless combustion mode, the peak flame temperature is controlled and the temperature gradient between the initial and maximum state is lower than the traditional combustion mode. This results in a decrease of thermal nitrogen oxide formation. 6 High-temperature environment (above the auto-ignition temperature of the fuel) allows air and fuel mixture to ignite spontaneously within the entire combustion volume, leading to complete oxidation and reduced fuel consumption, thus enhances the combustion efficiency. 2 These phenomena can be achieved when the incoming air and fuel mixture is preheated and diluted prior to the reaction. For this reason, recirculation of hot flue gas into the fresh air and/or fuel streams is often used. 7 Wünning and Wünning 8 proposed the gas recirculation factor K V > 3 (which calculated using a ratio of internal flue gas recirculation to a sum of combustion air and fuel flow rate) with furnace temperature higher than the auto-ignition temperature of the fuel to describe the regime of flameless combustion. Cavaliere and De Joannon 1 summarized that flameless combustion is bounded by inlet temperature of air/fuel mixture and combustion temperature, which

The process by which biomass can be converted to a producer gas by supplying less oxygen than actually required for complete combustion of the fuel is known as gasification. It is a thermo-chemical process and it is performed by a device known as gasifier. For executing the gasification experiments nowadays single throated gasifier uses sugarcane industry waste. In the present study we get to know that sugarcane briquettes are manufactured from residue of sugarcane which is used as a biomass material for the gasification process. Briquettes are formed by extruding the sugar which is extracted from the residue of sugarcane (bagasse) dried in the sun. Equivalence ratio, producer gas composition, calorific value of the producer gas, gas production rate and cold gas efficiency are certain grounds for estimating the performance of the biomass gasifier. The experiential results are compared with those reported in the literature.