Modelling of down-draft gasification of biomass – An integrated pyrolysis, combustion and reduction process

The goal of this work is to understand the gasification process for Miscanthus briquettes in a double-stage downdraft gasifier, and the impact of different Equivalence Ratios (ER) on syngas, biochar, and tar characteristics. The optimal ER was found to be 0.35, which yielded a syngas maximum heating value of 5.5 MJ/Nm 3 with a syngas composition of 20.29% CO, 18.68% H 2 , and 0.86% CH 4 . To better understand the observed behavior, an equilibrium reaction model was created and validated using the experimental data. The model showed that the heating value decreased with increasing ER, and that hydrogen production peaked at ER = 0.37, while methane (CH 4 ) became negligible above ER = 0.42. Tar and particle content in the gas produced at a certain temperature can now be predicted. To assess the biochar characteristics, surface structure image analysis and a surface area porosity analysis were carried out. Employing images from a scanning electron microscope (SEM), the biochar cell bonds and pore structures were examined and analyzed. By using the Brunauer-Emmett-Teller (BET) analysis of the surface porosity, the surface area to be 186.06 m 2 /g and the micro pore volume was calculated to be 0.07 m 3 /g. The final aspect of the analysis involved an evaluation of tar production. Combining current and prior data showed a logarithmic relationship between the amount of tar produced and the gasifier bed temperature, where the amount of tar produced decreased with increasing bed temperature. This results in very low tar levels, which is one of the known advantages for a double-stage downdraft gasifier over a single-stage system. Energies 2018, 11, 3225 2 of 23where currently only 290 million of 915 million inhabitants have access to electricity [2]. It is clear that different sustainable technologies have to be developed to achieve clean energy production. Biomass gasification is one of the possible routes through which carbon-neutral energy can be produced.Gasification is a process that converts organic carbonaceous materials at high temperatures into a fuel gas containing carbon monoxide (CO), hydrogen (H 2 ), methane (CH 4 ), and carbon dioxide (CO 2 ) [3]. Produced gases, with high concentrations of CO and H 2 from the gasifier, can be fed into internal combustion engines for power production [4,5]. The syngas from the gasifier could be used for different purposes, such as producing chemical products, especially when it contains a high percentage of CO 2 and CH 4 [6]. The calorific value of the gas is dependent on the gasifying agent. The calorific value of the gas using air ranges between 4-7 MJ Nm −3 , while when gasifying with pure oxygen, the heating value of the gas ranges between 12-28 MJ Nm −3 [4]. There are many useful products of biomass gasification, including syngas, heat, power, biofuels, fertilizer, and biochar [4].The application of gasification can be found in several projects around the world, ranging from large industrial-scale projects (energy output in MW) to small-scale projects (in kW). Some examp...

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“…When gasifying with 100% oxygen, δ tends to zero. The Equations 20, 21, and 22 where obtained from sources [44,45].…”

Section: Model Formulationmentioning

confidence: 99%

An Experimental and Theoretical Study of the Gasification of Miscanthus Briquettes in a Double-Stage Downdraft Gasifier: Syngas, Tar, and Biochar Characterization

et al. 2018

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“…Syngas is mainly a mixture of combustible gases such as H2, CO and CH4, and noncombustible gases such as CO2 and N2 [5,6]. The gasification is a complex process that includes drying, pyrolysis, combustion, and reduction processes, as elaborated by Diyoke et al [7]. Typically, the quality of syngas is affected by some essential parameters such as biomass characterization, process operation parameters, and the gasifier reactor design [8].…”

Section: Introductionmentioning

confidence: 99%

“…From this, biomass is considered as the most vital key in the gasifier reactor design. Due to the high expenses of gasifier design, many biomass gasification models were carried out to study the feasibility of biomass gasification and to predict the amount and composition of syngas production [7,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Fuel Characterization Study and Simulation of Dewatered Domestic Wastewater Sludge Gasification Using ASPEN Plus

Ali¹,

Akıllı²

2019

acperpro

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Dewatered domestic wastewater sludge (DDWS) is one of the largest contributors of waste material in the world, and it immediately elevates local environmental problems, especially in the urban area. The conversion of this material into a usable form of green energy, such as syngas through gasification, can be a vital solution. Hence, this method not only solves the environmental issues related to DDWS disposal but also participates as an energy source. To achieve this goal, the essential fuel characterization, which includes initial moisture content, high heating value, ultimate analysis, and proximate analysis, were carried out to assess the potential energy in DDWS. Due to the high expenses of the successful design of the gasifier reactor, and there are no efficient methods to predict the gasification performance, the model of the DDWS gasification process using ASPEN Plus software was developed. As ASPEN Plus software does not contain a built-in gasifier reactor model, a combination of various reactors is used to simulate the gasification processes. These processes were divided out into two stages. In the first stage, DDWS was decomposed into its element by specifying yield distribution. By using Gibbs free energy minimization approach, the gasification reactions were modeled. The current model was validated with the previously published work. From the characterization findings, DDWS showed high initial moisture content 84.64% and potential energy with 16.84 MJ/kg high heating value. The proximate analysis based on the dry base of DDWS exhibited that more than 55.42 % of their mass is composed of volatile materials, and ash content is found to be less than 25.79%. The elemental of carbon, hydrogen, nitrogen, sulfur, and oxygen component in the DDWS sample was 34.29%, 5.20%, 5.80%, 3.12%, and 25.80%, respectively. By applying operating parameters, which include reaction temperature, reaction pressure, airflow rate, and moisture content, it's found that the increase in reaction temperature (673-1673K) enhanced the production of CO and H2 while increasing reaction pressure adversely affected the generation of H2 and CO. The increase in the airflow rate increases CO2 mole fraction in syngas and shift the gasification process to combustion. The heating value of syngas sharply decreased with the increase in the DDWS moisture content. From the simulation results, ASPEN Plus simulator software is presented with the high capability to be used as a predictive tool for optimization of the gasifier performance.

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“…Supported by the U.S. Poultry Association, our group proposed to use downdraft fixed bed gasifiers to dry and gasify the HPAI poultry. The downdraft fixed bed gasifier has been proposed as a solution because of its syngas temperature from the gasifier is above 600 • C, which has the potential to inactivate HPAI virus when combining with the drying process [13,14]. Moreover, downdraft fixed bed gasification technology works under atmosphere pressure and has the lowest tar emissions compared with other types of fixed bed gasifiers.…”

Section: Introductionmentioning

confidence: 99%

Clean Poultry Energy System Design Based on Biomass Gasification Technology: Thermodynamic and Economic Analysis

et al. 2019

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Despite growing attention has been paid to waste material gasification for high-efficiency energy conversion, the application of gasification technology in meat waste management is still limited. To fill this gap, this study designed two systems which evaluated the potential of using gasification technology to manage the poultry waste that has been exposed to highly pathogenic avian influenza (HPAI). Two systems are simulated by using Aspen plus combined with a one-dimensional kinetics control gasification model, and wood or dried poultry is selected as the feedstock for the gasifier. The results show that the energy efficiency of the poultry drying system (wood gasification) is 14.5%, which is 12% lower than that of the poultry gasification system when the poultry energy is accounted as energy input. Even though the economic analysis indicates the poultry elimination cost of the poultry gasification system is only 30 $/tonne lower than the poultry drying system, taking the absence of dried poultry burial into consideration, the poultry gasification system has development potentials. The sensitivity analysis shows that labor fee and variable factor has larger effects on the poultry elimination cost, while the uncertainty analysis determines the uncertainty level of the economic analysis results.

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Modelling of down-draft gasification of biomass – An integrated pyrolysis, combustion and reduction process

Cited by 53 publications

References 60 publications

An Experimental and Theoretical Study of the Gasification of Miscanthus Briquettes in a Double-Stage Downdraft Gasifier: Syngas, Tar, and Biochar Characterization

An Experimental and Theoretical Study of the Gasification of Miscanthus Briquettes in a Double-Stage Downdraft Gasifier: Syngas, Tar, and Biochar Characterization

Fuel Characterization Study and Simulation of Dewatered Domestic Wastewater Sludge Gasification Using ASPEN Plus

Clean Poultry Energy System Design Based on Biomass Gasification Technology: Thermodynamic and Economic Analysis

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