Rubber wood (Ficus elastica) is one of the biomass waste that can be used as rawmaterial for gasification process, and has a calorific value of 4069 cal/g. Gasification is a process to convert a solid fuels to syngas (CO, CH4, and H2) through a partially combustion process using limited air between 20% to 40% of air stoichiometry. Depending on the direction of airflow, the gasifier are classified as updraft, Downdraft, and cross-flow. The Downdraft type of gasifier produces a lower tar content than updraft type. The gasification of rubber wood and rubber wood-coal mixture were carried out in this research. The purpose of the research is to determine the effect of Air Fuel Ratio (AFR) and temperature on calorific value and composition of syngas using a Downdraft gasifier. The variations of AFR were 0. 64, 0. 95, and 1. 26. The temperature of gasification was varied between 600-1000º C. The result showed that the percentage of CO, H2, and CH4 decreased with increasing of AFR and decrease in calorific value. The calorific value of syngas increased along with the temperature. The use of coal in the gasification process can maintain the stable combustion temperatures and increase the syngas produced. The best-operating conditions in this research occurred at AFR of 0. 64, temperature of 800º C and use of coal as a stabilizer. At this condition, the percentage of syngas of 35. 95% of CO, 15. 95% of H2, 9. 38% of CH4, and caloric value of 9. 42 MJ/m3 was obtained. The highest gasification yield of 35. 75% was also reached.

The use of biomass by means of gasification to produce bio fuels and reducing the environmental impact of fossil fuels has been the focus of many researchers in recent years. In the present study, the computational fluid dynamics method is used to predict the process of gasification inside a Downdraft gasifier. Recent studies have shown that although many studies have been carried out by various researchers to maximize the cold gas efficiency in the gasification process, so far, no study has been done to minimize the emission of pollutants as one of the other important design parameters along with the increase of cold gas efficiency. So, in this study, the effect of changing the equivalence ratio as design variable on the gasification efficiency as well as the amount of pollutant produced simultaneously is investigated. Also, in this study, CO/CO2 and H2 /H2O molar ratios are considered as another objective function in selecting the optimal process point. In order to verify the validity of the results, the simulation data was compared with the experimental results and the previous numerical study, and a good agreement was shown between their comparison. The results of this study show that in the ratio of 0. 64, the rate of production of nitrogen oxides relative to cold gas efficiency is optimal considering the maximum production of CO/CO2 and H2/H2O molar ratios. This point is the optimal point. Under the working conditions of the gasification process.

Municipal solid waste is the largest waste stream around the world and has a great potential for generating synthetic gas. An improved numerical model is used based on equilibrium thermodynamics to predict the composition of the municipal solid waste gasification products. To validate the superiority of the model, the results are compared and verified against some experimental studies. The developed model is then used to study the potential of energy extraction from solid waste in Iran as a case study. For this purpose, Iran is divided into ten separate zones, and the chemical composition of the wastes in each region is determined based on the type and amount of the waste compounds. Next, the effects of some important factors such as the amount of moisture content, environmental humidity, and equivalence ratio are investigated. The results show that at the equivalence ratio of 0.3, Khuzestan and Zagros regions have the highest and the lowest heating values of the produced synthetic gas with the cold gas efficiency of 20% and 16.5%, respectively. At the equivalence ratio of 0.6, the same qualitative results are obtained; however, the mentioned values of cold gas efficiency for Khuzestan and Zagros decrease to 14.8% and 13.8%, respectively.

Biomass gasification is one of the promising technologies to produce energy from the renewable energy sources, and the Downdraft biomass gasifier is a widely used biomass energy conversion device. Among the various components of a gasifier, the position and the inclination of air nozzle have a vital role in the generation of producer gas. Therefore, a proper design is needed to fix the position and angle of the air nozzle. Keeping the above aspects, the present work focuses on the numerical simulation to predict the appropriate position and inclination of the air nozzle in a 50kWth imbert type Downdraft gasifier by the species transport approach. The nozzle inclination varies from 0° , 20° , 30° , 45° and 60° , and the nozzle position is considered from 50mm, 100mm, 150mm and 200mm respectively. Experiments were also conducted to validate the numerical study. Both the studies show that the nozzle inclination at 45° and its position at 100mm above the reduction zone gives a reasonable composition of producer gas.

This paper investigated the possibilities of using birch wood chips for fixed-bed Downdraft gasification. The preliminary air gasification resulted producer gas with an average composition of 11.5% CO, 5.4% CO2, 5.9% H2, 0.38% CH4 corresponding to a mean lower heating value of about 2 MJ/kg. The approximate size of woodchips used for gasification was around 11.5 mm for a maximum solid throughput of 0.65 kg/h. The obtained equivalence ratio (ratio between actual air fuel ratio and stoichometric air fuel ratio) as a result of air and biomass feed was close to 0.45 which was stable throughout the test. Producer gas left the gasifier at ca. 150oC and was diverted for flaring owing to the level of low energy content. Despite availability, the option for gas to generate heat and electricity via integrated gas engine has not been utilized in the present case and remained for further ongoing research.

An analysis of the experimental characterization of the three agricultural residues redgram stalk, soyabean stalk, and chilli stalk (biomass) was carried out and the higher heating values (HHV) were determined using the available correlations from the literature. The selected agricultural residues proximate analysis results show moisture about 4.2 to 7.4%, the volatile matter about 79.3 to 85.8%, fixed carbon about 4 to 8.94%, and ash about 2.5 to 5.5%. The ultimate analysis results present elemental compositions such as carbon about 46 to 49%, hydrogen about 5%, oxygen about 30%, and the nitrogen about 3.1 to 3.7% with very low sulfur content. The HHV of agricultural residues varies from 14MJ kg-1 to 19MJ kg-1. The design of the Downdraft gasifier to accommodate agricultural residues was carried out taking into account the characteristics of the agricultural residues and the specifications of the internal combustion (IC) engine. The characteristics of the agricultural residues depict that the three agricultural residues are suitable for gasification and can be used in a single gasifier.

In this paper, a thermochemical equilibrium model is used to predict the performance of a Downdraft biomass gasifier. Numerical results are shown to be in good agreement with those of the experiments. Different biomass materials are tested using the model, and forest residual is shown to be the most energetic one. For this material, the gasification temperature, syngas composition and calorific value are calculated. The effects of moisture content, air/fuel ratio, air inlet temperature and steam/fuel ratio are also investigated. The air inlet temperature is found to be the only way to increase syngas calorific value and cold gas efficiency. The steam/fuel ratio, on the other hand, plays a key role in controlling the gasification temperature and H2/CO ratio.

In international development programs on improvement of energy supply for cooking in remote regions, where people are dependent on wood as the sole fuel resource, biomass cook stoves have a remarkable place. The thermal efficiency of such stoves are up to 3 times of those of traditional open fire stoves. In this research, a biomass cook stove was manufactured and evaluated according to the emission and performance test protocol. The fire power of the stove was 1. 4 kW, and flaming duration by feeding 400 g of pistachio shell was recorded to be 26 minutes. In order to improve the pyrolysis vapor combustion process, a damper was embedded in the stove, and also the outer wall of the stove was isolated by using a ceramic layer. Results showed that the control index was improved by three folds. Also, burning duration increased up to 57% and the emission of carbon monoxide was found to be in the permissible range.