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This study presents the experimental results obtained from hybrid filtration combustion using biomass pellets. The experiments were carried out using a porous media gasifier filled with pellets and inert material. The gasifying agent used was an air–steam mixture, with 40% being steam. The dependence of the temperature in the gasifier's reaction zone from the volume percentage of inert porous material in the gasifier, the specific heat capacity of this material, as well as the air–steam blowing rate, was investigated. The multifactor experiment method was used. A maximum temperature of 1245 °C was achieved using 28 vol% of porous material with a heat capacity of 1000 J/(kg·°C) and at a blowing rate of 42 m3/h. The maximum hydrogen content in the syngas was 28 vol%. This was achieved at an air–steam blowing rate of 42 m3/h and 40 vol% porous material, with a heat capacity of 1000 J/(kg·°C). The calorific value of the syngas was 12.6 MJ/m3. The highest CO content in the gas was 28 vol% and was obtained at 20 vol% porous material with a heat capacity of 1000 J/(kg·°C) and a blowing rate of 42 m3/h. The obtained information is applicable in the design, management, and control of gas production by way of a hybrid filtration combustion process in a downdraft gasifier. [ABSTRACT FROM AUTHOR]

In this work, a study was performed on the influence of the ratio of height to the diameter of the reduction zone of a small-size downdraft gasifier as well as of the fuel fraction sizes on the gas quality (the quality was evaluated for CO content). The ratio of a full side area to the volume of a fuel fraction (SVR) was used as a fuel parameter. The maximum CO concentration was observed when using a small fuel fraction with SVR—0.7–0.72 mm−1 and when adhering to the ratio of height to the diameter of the reduction zone H/D—0.5–0.6. The maximum electric power for gasoline generators (nominal power equaled 4 kW) when using the gas received from the fast-growing hybrid willow biomass equaled 2.4 kW. This power is 37.5% lower than when using gasoline and 7.0% lower than when using the gas received from the hardwood biomass. The emissions of harmful gases into the atmosphere by the gasoline generator engine equaled 0.12–0.14% CO and 24–27 mln−1 CxHy. The emissions were 64.8 times less for CO and 8.5 times less for CxHy when compared with using gasoline. [ABSTRACT FROM AUTHOR]

The gasification rate of fuel, biomass gasification in particular, is an important parameter which is worth considering in the process of creating a gasifier with a continuous operation process. The gasification of biomass is a complex thermochemical process. The theoretical and practical studies of the gasification rate of biomass are complicated because of a high thermochemical rate of reactions in the functioning zones of a gasifier. The complexity of the study prevents the achievement of the required accuracy of the analytical model of the gasification rate of biomass. The known theoretical models of the gasification rate only partially describe the dynamics of the gasification rate of biomass. Moreover, most scientific studies are focused on establishing the effects of gasifier parameters and the gasification process on the quality indicators of the received gas but not on the gasification rate of fuel. To build an accurate model of the gasification rate the authors propose a series of experimental studies in a well-defined range of the parameters of a gasifier. The paper suggests a simple mathematical model of the gasification rate of biomass, which is proportional to the amount of plant biomass that remained non-gasified. The coefficients of the gasification rate for straw pellets, wood pellets and wood in pieces have been determined. Under a minimal air supply into an active zone of a gasifier (0.00088 m3/s) a coefficient of gasification rate is nearly the same for the test fuel materials and it differs by 4.7% between wood pellets and straw pellets. When the air supply increases, the gap between the coefficients increases as well and it reaches 9.44 × 10−5 c−1 for wood pellets, 1.05 × 10−4 c−1 for straw pellets and 8.64 × 10−5 c−1 for wood in pieces under air supply into an active zone of a gas generator of 0.01169 m3/s. Straw pellets have the highest gasification rate and wood in pieces has the lowest gasification rate. [ABSTRACT FROM AUTHOR]