Department of Chemical Engineering

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Subject: search.filters.subject.Gasification

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    Multizone model of a refused derived fuel gasification: A thermodynamic Semi-empirical approach
    (Elsevier, 2022-05) Sheth, Pratik N.
    Substitution of fossil fuels by sustainable energy sources has raised attention worldwide. Refuse derived fuel (RDF), which is the combustible fraction of Municipal solid waste (MSW), is used as an alternative fuel through combustion route. The gasification of RDF is gaining importance due to the operational issues of RDF combustion. The multizone RDF gasification model is developed to predict syngas composition in the present study. A stoichiometric approach is followed for modelling the pyrolysis and combustion zone. The reduction zone is modelled as a cylindrical fixed bed reactor with a uniform cross-sectional area. The developed set of differential equations is solved using MATLAB to predict the syngas properties. The novelty lies in the fact that the model can predict the output of each zone satisfactorily since the model assumptions are more realistic and cater to the heterogeneous nature of RDF. The impact of Equivalence ratio (ER), moisture content and reduction zone length on the performance of the gasifier are evaluated. The optimum values of lower heating value (LHV), gas yield, cold gas efficiency (CGE) and carbon conversion efficiency (CCE) for three different RDF at optimum ER is determined. Notably, 90% of the conversion is achieved within 60% length of reduction zone for all three types of RDF at all ERs. Predicting syngas properties can pave the way for the process integration of RDF gasification-based syngas in various industrial applications.
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    Tar cracking enhancement by air sparger installation in the combustion zone of the downdraft gasifier
    (Elsevier, 2022-11) Sheth, Pratik N.
    In the present article, experimental studies are performed on Imbert downdraft gasifier using two different air distribution systems (two-nozzle and air-sparger) for the combustion zone. A novel air distribution system (air-sparger) is designed to supply uniform air across the combustion zone for achieving uniform temperature and enhancing the tar cracking. The effect of operating parameters (Equivalence ratio, temperature, air flow rate, and biomass consumption) on the tar cracking and producer gas compositions are investigated. Tar is measured in the producer gas before and after the gas cleaning units using a stack monitoring system. The experiments are performed by varying the airflow rate between 3 and 7 Nm3 h−1, and the equivalence ratio varies from 0.24 to 0.38. The operating parameters and air-sparger have significantly influenced the zone's temperature, producer gas composition, and the tar content in the producer gas. The maximum temperature of the combustion zone and reduction zone increases from 764 to 975 °C and 467 to 760 °C respectively with the air-sparger compared to the two-nozzle conventional air distribution system at the airflow rate of 7 Nm3 h−1. The lower heating value of the producer gas and the cold gas efficiency of the gasifier increased from 4.28 to 4.37 MJ Nm−3 and 48.55–55.05%, respectively, with the air-sparger. The incorporation of air-sparger reduces tar in producer gas from 23.95 to 0.97 g Nm−3 before gas cleaning unit at the airflow rate of 7 Nm3 h−1. Air-sparger has shown the adequate potential to enhance tar cracking and improve the overall gasifier performance.
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    Improving the properties of producer gas using high temperature gasification of rice husk in a pilot scale fluidized bed gasifier (FBG)
    (Elsevier, 2019-01) Pandey, Jay
    Biomass gasification is a well-studied thermo-chemical conversion route for the generating producer gas, a renewable energy carrier, for thermal and power applications as well as for bio-fuel production. High energy efficiency and clean gaseous fuel with low tar and suspended particulate matters (SPM) contents are some of the major challenges with biomass gasification. Herein, we report non-catalytic high temperature (720–855 °C) gasification of rice husk using fluidized bed gasifier (FBG). Producer gas mainly comprising of CO and H2 exhibited good higher heating value (HHV) and lower heating value (LHV) of 3.6 and 3.2 MJ/Nm3 respectively. Our experimental observations revealed that 790 °C is the optimum temperature for rice husk gasification with high carbon conversion efficiency (91.6%), thermal efficiency (75%) and high gas yield 2.7 m3/kg. High temperature gasification also resulted into reduced tar + SPM content (0.33 g/Nm3). Rice husk derived producer gas with good heating value and low tar + SPM content can be used as replacement of conventional fossil fuels for thermal applications in many processing industries.
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    Advances in Downdraft Biomass Gasification
    (‎ Nova Science Publishers, 2010) Sheth, P.N.
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    Experimental studies on producer gas generation from wood waste in a downdraft biomass gasifier
    (Elsiever, 2009-06) Sheth, P.N.
    A process of conversion of solid carbonaceous fuel into combustible gas by partial combustion is known as gasification. The resulting gas, known as producer gas, is more versatile in its use than the original solid biomass. In the present study, a downdraft biomass gasifier is used to carry out the gasification experiments with the waste generated while making furniture in the carpentry section of the institute’s workshop. Dalbergia sisoo, generally known as sesame wood or rose wood is mainly used in the furniture and wastage of the same is used as a biomass material in the present gasification studies. The effects of air flow rate and moisture content on biomass consumption rate and quality of the producer gas generated are studied by performing experiments. The performance of the biomass gasifier system is evaluated in terms of equivalence ratio, producer gas composition, calorific value of the producer gas, gas production rate, zone temperatures and cold gas efficiency. Material balance is carried out to examine the reliability of the results generated. The experimental results are compared with those reported in the literature.
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    Thermo-Chemical Conversion of Jatropha Deoiled Cake: Pyrolysis vs. Gasification
    (IJCEA, 2015-10) Sheth, P.N.
    Pyrolysis and gasification of biomass is considered to be the promising alternative solutions for the increase of energy demand and environmental awareness. Pyroysis process produces a variety of chemicals by limited degradation and gasification process leads to complete breakdown of the biomass into permanent gases. By gasification, solid biomass is converted into a combustible gas mixture normally called “Producer Gas” consisting primarily of hydrogen and carbon monoxide, with lesser amounts of carbon dioxide, water, methane, higher hydrocarbons, nitrogen and particulates. Whereas the pyrolysis process produces a mainly three types of products: solid (charcoal), liquid (tar and other organics) and gaseous products. In the present study, Jatropha de-oiled cake is taken as a biomass. The pyrolysis and gasification experiments are carried out for comparing the results. The biomass is pyrolyzed in a fixed bed reactor in a Nitrogen environment as well used to produce the producer gas in a fixed bed downdraft biomass gasifier.
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    Biomass gasification models for downdraft gasifier: A state-of-the-art review
    (Elsiever, 2015-10) Sheth, P.N.
    Among the different methods of energy production from biomass, gasification is considered as the most suitable option as it is a simple and economically viable process to produce thermal energy or decentralized electricity generation. Downdraft gasifiers are typically small-scale units having maximum power production capacity up to 5 MW. This feature makes it more suitable for decentralized power generation and distribution to the remote villages/islands deprived of grid electricity. Mathematical models can be helpful for the design of gasifiers, prediction of operational behavior, emissions during normal conditions, startup, shutdown, change of fuel, change of loading, and to alleviate the type of problems mentioned above. It has been observed that although many researchers have developed models of various types and degrees of complexity, reviews of these modeling and simulation studies are scarce. Largely, it is observed that the review articles reported in the literature fail to address the basic understanding of each model types and their applicability to design different gasifiers for a certain feedstock and variation of operating parameters. This review article discusses different models available for downdraft gasifiers such as thermodynamic equilibrium, kinetic, CFD, ANN and ASPEN Plus models. A comparative analysis of each model and its output is carried out. A critical analysis of the effect of different modeling parameters and finally the advantages and disadvantages of each modeling technique is outlined.
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    Recent progress in thermochemical techniques to produce hydrogen gas from biomass: A state of the art review
    (Elsiever, 2019-10-04) Sheth, P.N.
    The present work comprehensively covers the literature that describes the thermochemical techniques of hydrogen production from biomass. This survey highlights the current approaches, relevant methods, technologies and resources adopted for high yield hydrogen production. Prominent thermochemical methods i.e. pyrolysis, gasification, supercritical water gasification, hydrothermal upgrading followed by steam gasification, bio-oil reforming, and pyrolysis inline reforming have been discussed thoroughly in view of the current research trend and latest emerging technologies. Influences of important factors and parameters on hydrogen yield, such as biomass type, temperature, steam to biomass ratio, retention time, biomass particle size, heating rate, etc. have also been extensively studied. Catalyst is a vital integrant that has received enough attention due to its encouraging influence on hydrogen production. Literature confirms that hydrogen obtained from biomass has high-energy efficiency and potential to reduce greenhouse gases hence, it deserves versatile applications in the coming future. The study also reveals that hydrogen production through steam reforming, pyrolysis, and in-line reforming deliver a considerable amount of hydrogen from biomass with higher process efficiency. It has been identified that higher temperature, suitable steam to biomass ratio and catalyst type favor useful hydrogen yield. Nevertheless, hydrogen is not readily available in the sufficient amount and production cost is still high. Tar generation during thermochemical processing of biomass is also a concern and requires consistent efforts to minimize it.