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.

Background: Agricultural waste has been proposed as an alternative energy resource to meet fossil fuel crisis, green house emission, and other environmental impacts worldwide. In Iran, rice husk and bagasse are main resources of biomass which can be used to produce syngas. This paper deals with a simplified model of combined gasification of coal and biomass processes considering chemical equilibrium.Results: It should be noticed that the CO2 which is produced from agricultural waste gasification is natural because the biomass absorbs CO2 from nature and gives it back after gasifying; however, mixing agricultural waste with coal leads to enrich syngas quality and Gasifier efficiency.Conclusions: In this regard, an advanced coding was developed to simulate the thermodynamics of the co-Gasifier and to find the produced syngas composition. The effects of moisture content, steam-to-biomass ratio, and Gasifier temperature are then discussed on the system performance. Additionally, co-gasification of rice husk/coal was compared with co-gasification of bagasse/coal. The results indicated that adding coal to biomass increases lower heating value of syngas from 4, 694 kJ/Nm3 to 5, 321 kJ/Nm3 and Gasifier efficiency from 71.29% to 77.85%.

An Eulerian–Eulerian-based two-dimensional mathematical modeling approach for bubbling fluidized bed Gasifier using FLUENT has been proposed to transfer energy, momentum, and mass between two phases namely solid and gas together with the application of the kinetic theory of solid particle flow. The modeling equation involves eight homogeneous and five heterogeneous reactions kinetics. The eddy dissipation model of FLUENT has been used to incorporate homogeneous reaction kinetics and a user-defined code has been developed that describes the kinetics of heterogeneous reactions. The simulation result shows that the exit syngas composition is in line with the experimental one and has a maximum error of around 4.05% for CO and 2.68% for hydrogen. This model has been used to study the variation in hydrogen concentration in the syngas to maximize hydrogen production based on different operating and design parameters.

The main advantage of a fluidized bed is its capability in excellent gas-fuel mixing. However, due to the lacks of gas radial momentum, its lateral mixing of gas-solid is not adequate. Therefore, this research is focused on fluidized bed hydrodynamics enhancement using the modified gas distributor plate design. For getting an optimum fluidized bed hydrodynamics prediction, three different classical ANSYS Fluent drag models, namely Wen-Yu, Syamlal O’ Brien, and Gidaspow are examined first. Afterward, a novel distributor plate called swirl distributor plate (SDP) is proposed in order to enhance the gas-fuel mixing in vertical and radial directions. In terms of simulation approach, results were presented and compared with the experimental data. It has been observed that better hydrodynamics prediction is achieved by Syamlal O’ Brien drag model. The effect of SDP on gas-solid mixing was then studied numerically and compared with conventional distributor plate (CDP). Compared with CDP, better gas-solid mixing was found while the SDP was used. As a final point, gasification test was conducted in a lab scale system in order to study and compare the composition of produced syngas using both distributor plates. Based on the gasification results, SDP leads to promotion of Hydrogen and Carbon monoxide by 34. 85 and 65. 92 percent, respectively.

Concerning the global warming due to large CO2 emission, the efficient use of coal becomes important for getting sustainable energy production. Coal gasification under CO2-rich condition is expected to be an effective way to produce a concentrated and pressurized carbon dioxide stream, resulting in reduction in separation energy of CO2 for CCS. Moreover, the soot formation, which is of significant environmental concern, is still being neglected in the past studies of coal gasification. A one-step soot formation reaction mechanism is proposed in this study and implemented in numerical simulations of coal gasification with the aim of describing the gasification behaviors in a two-stage entrained-flow Gasifier. In addition, the effects of O2 ratio and CO2 concentration on soot concentration, syngas heating value and carbon conversion are numerically studied in an effort to increase the syngas production. The Eulerian–Lagrangian approach is applied to solve the Navier–Stokes equation and the particle dynamics. Finite rate/eddy dissipation model is used to calculate the rate of nine homogeneous gas-to-gas phase reactions including soot formation and soot oxidation. While only finite rate is used for the heterogeneous solid-to-gas phase reactions. It is found that formation of soot enhances the H2 production in the Gasifier. Carbon conversion gradually increases with an increase in O2 ratio, while producing a low heating value syngas beyond a certain limit of O2 ratio. In contrast, an increase in CO2 concentration in the Gasifier increases heating value of product syngas.

Abench-scale updraft Gasifier was used as a fluidizedand fixed-bed gasification unit in three modes (fluidizedbed at equivalence ratios (ER) =0. 2 and 0. 25, and a mode in fixed-bed). The experiments were done in five different temperatures (650, 700, 750, 800 and 850oC). To obtain the required data to develop a thermodynamic equilibrium model, the proximate and ultimate analysis were carried out on potato shoot as feedstock. Since the developed model is a temperature-based model, it gives different outcomes in different temperatures. The model gave a completely exact result to predict CH4 in fluidized-bed at ER=0. 25. The average error for the difference between each produced gas in experiments and the model showed the best result of the model for CO with the error of just 0. 7%. Regarding each experiment data difference with the model data, the model was more accurate to be used in fluidized-bed, especially at ER=0. 25 than the other two modes. Moreover, the best performance of the model was obtained for CO, N2 and CO2, according to the average errors. Since the maximum amount of high heating value (HHV) and carbon conversion efficiency (CCE) was observed at higher temperatures, it can be contended that the model has better performance at higher temperatures.