Browsing by Author "Sheth, Pratik N."

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Air-CO2 and oxygen-enriched air-CO2 biomass gasification in an autothermal downdraft gasifier: Experimental studies
(Elsevier, 2022-10) Sheth, Pratik N.
The mounting CO2 emission and rapid depletion of fossil fuels are two significant challenges for sustaining growing energy requirements and keeping the environment clean. Biomass gasification using CO2 as a gasifying agent may be one of the alternative techniques to tackle such emerging problems. CO2 behaves as an inert gas at low temperatures and can be converted to CO at high temperatures. In the present study, air-CO2 and oxygen-enriched air-CO2 biomass gasification are successfully conducted in the autothermal reactor. The impacts of varying concentrations of CO2 and oxygen in the gasifying agent on the performance of the gasifier are analyzed. The CO2 content in the gasifying agent is varied from 0 to 45 vol% at two different oxygen concentrations (21 and 35 vol%). The reactor used is an Imbert-type downdraft gasifier with a thermal capacity of approximately 10 kW. The results reveal that the yield of CO in the producer gas increases compared to air gasification resulting in a higher heating value of the producer gas. However, the average temperature in the gasifier reduces with increasing CO2 percentage in the gasifying agent. Upon increasing the O2 fraction from 21 to 35 vol%, while keeping 30 vol% CO2 content constant, CO content is found to upsurge from 23.96 to 31.37 vol%. The inclusion of CO2 inside the gasifier promotes the endothermic Boudouard reaction that causes the conversion of CO2 into CO.
Aspen plus simulation of an inline calciner for white cement production with a fuel mix of petcoke and producer gas
(Elsevier, 2023-11) Sheth, Pratik N.
The white cement industry is facing the challenge of alternative fuel utilization replacing conventional fuel due to the impact of alternative fuel ash on the whiteness of clinker. On the other hand, municipal solid waste (MSW) disposal is a huge waste management problem worldwide. The present article focuses on utilizing MSW-based refuse derived fuel (RDF) as an alternative fuel in white cement. The ash-free producer gas derived via RDF gasification is proposed to overcome the challenge of direct RDF utilization. Aspen plus-based producer gas co-processing model for a calciner has been developed, considering 100% petcoke firing as the baseline scenario. The co-processing of producer gas further augmented the model to achieve a 15–20% thermal substitution rate (TSR). The developed model is validated using the actual plant data. The model results at 15% TSR predicted that the calciner outlet temperature will get reduced by 19 °C, with a 5.3% rise in calciner exit gas volume, which is manageable. CO2 mitigation potential at 15% TSR is estimated to be 11.33% of the baseline scenario. The TSR contribution of producer gas sensible heat at 593 °C is 2.7%, whereas the petcoke enters the system at 60 °C with negligible sensible heat.
CFD analysis of biomass gasification using downdraft gasifier
(Elsevier, 2021) Sheth, Pratik N.
CFD model has been developed for the 2D axisymmetric model of an Imbert downdraft gasifier. The present Model has been validated with experimental data. The model predicts CO, hydrogen, and CO2 with precise accuracy. Producer gas composition and gasifier temperature have been studied at different equivalence ratios (ER) i.e. 0.25 to 0.60. It is noted from the observation that the rise of the equivalence ratio tends to decrease the amount of CO, hydrogen, and methane in the producer gas whereas nitrogen and CO2 excessively increased. It has also been observed that the increase of the equivalence ratio tends to increase the temperature inside the gasifier.
CFD analysis of the downdraft gasifier using species-transport and discrete phase model
(Elsevier, 2022-11) Sheth, Pratik N.
In the present study, a 2-D axisymmetric steady-state computational fluid dynamics (CFD) model has been developed for biomass gasification in a fixed bed Imbert downdraft gasifier. A discrete phase model (DPM) based on the Euler-Lagrangian approach with species transport is applied to the gasifier having the capacity of ≈ 5 kW. The use of DPM for the particle-continuous phase interaction leads to capture more realistic gasification phenomena. The proposed model is an effort to carry forward the CFD technique by implementing an alternative chemical kinetic scheme to study the various gasification parameters. The model is validated at different values of equivalence ratios (0.19–0.33) for producer gas composition and found to be in better agreement with the experimental values reported in the literature. The standard estimated error for the present model is 6.64, 7.55, 2.92, and 5.28 % for carbon monoxide, hydrogen, methane, and carbon dioxide, respectively. Moreover, the calculated standard deviation is 0.44 only. The biomass feed and airflow rates vary from 3.43 to 5.82 kg/h and 2.41–8.02 Nm3/h, respectively. It has been found that an equivalence ratio in the range of 0.25 to 0.30 is the most appropriate condition in the present operating range of the gasifier. The proposed scheme allows accurate prediction under various operating conditions, which may enable the designer to optimise the operating conditions. The model predictions would help to design the process integration of gasification with any existing commercial energy-producing unit based on conventional fuels. Hence, it deliberates significant contribution and value addition in the current literature for the CFD modelling of biomass gasification. The present study not only helps to improve the overall performance of the gasifier but also provides the profiles of essential design variables across the length of the gasifier.
Chemical characterization of refuse derived fuel (RDF) using Py-GC/MS
(Elsevier, 2024-05) Sheth, Pratik N.
The conversion of municipal solid waste (MSW) to refuse-derived fuel (RDF) and its utilization as an alternative fuel in the cement industry has been an emerging trend. However, RDF is highly heterogeneous, with its complex composition changing with season and source. This work is focused on the chemical characterization of six RDF samples listed as A, B, C, D, E, and F from different locations across the country using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), thermogravimetric instrument and CHONS elemental analyzer. Qualitative and semi-quantitative results were obtained using EGA, single-shot and double-shot analysis methods. EGA has been used to derive qualitative results in correlation with TGA. FTIR analysis was carried out to understand the initial functional characterization. XRF analysis along with ICP-MS triple quad revealed the inorganic makeup of the samples. Single-shot results indicated that apart from non-hydrocarbon gases (CO2 and O2), the long-chain alkenes were most abundant, followed by alkanes, aromatic compounds, and ketones. Double-shot analysis indicated the presence of chloride and sulphur-based compounds in RDF samples as limiting components. Polystyrene contribution to LHV of RDF has been highlighted. The study can be further used to conduct compositional studies of RDF and its pyrolytic behavior in the gasifier. It will further strengthen the future gasifier models where pyrolysis is one of the critical steps. This technique will be very helpful in obtaining a better characterization of volatile and non-volatile (bio-oil and ash) fractions of the pyrolytic products.
Co-processing of petcoke and producer gas obtained from RDF gasification in a white cement plant: A techno-economic analysis
(Elsevier, 2023-02) Sheth, Pratik N.
White cement production, unlike grey cement, depends entirely on ashless conventional fuels (oil, petcoke) to meet its thermal energy requirement. The primary barrier to utilizing any solid alternative fuel in white cement is the impact on whiteness due to ash content. The study is focused on establishing producer gas from refuse-derived fuel (RDF) gasification as an alternative fuel in clinker production in an Indian white cement plant with a 15% thermal substitution rate (TSR). A stoichiometric calciner model has been developed to predict calciner outlet parameters considering co-firing of petcoke and producer gas, where producer gas has a high heating value (HHV) of 3.95 MJ/Nm3 and gas yield of 2.36 Nm3/kg RDF. The model predicted the decrease in calciner outlet temperature by 2.6% at 15% TSR with 8.49% CO2 mitigation potential by replacing conventional fuel. It is concluded that RDF gasification is viable for white cement plants considering an IRR of 13.57% and discounted payback period of six years and two months for a 10-year gasifier operation. The study will facilitate the utilization of the RDF in white cement plants, reducing their manufacturing cost and dependence on fossil fuels.
Correction to: deciphering cleaner and sustainable frontiers in scientific cow waste valorization: a review
(Springer, 2024-09) Sheth, Pratik N.; Yadav, Sushil Kumar
Metabolomic profiling of cow urine of various breeds reveals bioactive metabolites of diverse industrial applications
(Springer, 2025-07) Yadav, Sushil Kumar; Sheth, Pratik N.
Cow urine is widely utilized for medicinal and agricultural purposes in rural areas of India, with urine from indigenous cow breeds (Bos indicus) believed to offer unique benefits compared to that of exotic (Bos taurus) breeds. This research aimed to profile the metabolites present in the urine of indigenous breeds of cows using gas chromatography–mass spectrometry (GC–MS) and to explore the potential applications of the identified compounds by referencing the established literature. The various cow breeds included in the study were Gir, Sahiwal, Gangatiri, Hariana, Kankrej, Rathi, Gaolao, and Jersey. Cows employed in the study to collect the samples from various locations differed in their body weight, age, and stage of lactation. GC–MS analysis revealed a range of compounds, including ethanone, cresol, bis(2-ethylhexyl) phthalate, phenol, eicosane, pentanol, isobutyl ester, ethyl ester, binapacryl, trifluoroacetate, xylene, amylene hydrate, dibutyl ester, and formamide. Notably, several compounds were consistently observed across multiple indigenous breeds. For instance, bis(2-ethylhexyl) phthalate and xylene were found in nearly all indigenous breeds, while ethanone was detected in Gir, Sahiwal, Gangatiri, Kankrej, Hariana, Gaolao as well as Jersey cows. Similarly, eicosane and pentanol were present in Gangatiri and Hariana breeds. These overlapping chemical signatures highlight potential metabolic similarities among the studied cow breeds. The identified compounds are known for their diverse industrial and pharmaceutical applications, including use in disinfectants, flavorings, cosmetics, and agrochemicals as well as metabolic engineering. Thus, this study—for the first time—comprehensively delineated the comparative metabolite profile of cow urine among different breeds of cows. The spectrum of urinary metabolites identified could offer opportunities to foster bio-based innovations having multifarious applications, including new product developments, across diversified fields.
Modeling, Simulation and Experimental Studies on Downdraft Biomass Gasifier
(BITS, Pilani, 2009) Sheth, Pratik N.
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.
Prediction of HHV of fuel by Machine learning Algorithm: Interpretability analysis using Shapley Additive Explanations (SHAP)
(Elsevier, 2024-02) Sheth, Pratik N.
This study presents a novel approach using machine learning techniques to estimate waste materials' higher heating value (HHV), which plays a crucial role in waste-to-energy generation efficiency. The study utilizes a dataset comprising ultimate and proximate analysis of 16 different waste types. It employs six machine learning models: Extra Trees, Random Forest, Support Vector, Decision Tree, Extreme Gradient Boosting, and Multivariate Linear Regressors. The investigation explores the relationships between the features and outcomes through Spearman correlation, feature importance analysis, SHAP dependence, and decision plots, providing the interpretability of the model's predictions. The models are fine-tuned with hyperparameters for six feature sets, enabling researchers to anticipate HHV based on their specific input. The results demonstrate high accuracy in predicting HHV, with R2 ranging from 0.83 to 0.98, RMSE from 2.25 to 0.79, and MAPE from 6.01 to 0.92%. The study further reveals that higher carbon and hydrogen content increases HHV, while higher oxygen and ash content results in decreased HHV. Notably, Carbon, Ash content and Hydrogen content are the significant features with mean absolute SHAP values of 2.17, 0.65, and 0.37, respectively. The proposed alternative prediction method has practical implications for waste-to-energy generation research and practice, facilitating informed decision-making in this field.
Recent Progress in Refuse Derived Fuel (RDF) Co-processing in Cement Production: Direct Firing in Kiln/Calciner vs Process Integration of RDF Gasification
(Springer, 2022-06) Sheth, Pratik N.
Refuse-derived fuel (RDF) from municipal solid waste (MSW) is an alternative fuel (AF) partially replacing coal/petcoke in a calciner/kiln of cement plant. The maximum thermal substitution rate (TSR) achieved through RDF is 80–100% in the calciner, while it is limited to 50–60% in the kiln burner. Different AF pre-combustion technologies, advancements in multi-channel burners, and new satellite burners have supported high TSR. Extensive efforts in modelling kiln burner and calciner lead to enhance TSR. However, the cement industry faces operational issues such as incomplete combustion, increased specific heat consumption, reduced flame temperature, and kiln coating buildup. There is an interest in RDF gasification, a promising alternative to eliminate the operational issues of the cement industry, which needs to be integrated with the existing cement plant. The article reviews the integration of gasification in cement production and various experimental and modelling studies of the direct firing of AF/RDF in the kiln/calciner. The features and technology status of both approaches are compared. The different gasification integration technologies with varied configurations for cement plant calciner are highlighted. The article emphasizes the need to develop suitable calciner/kiln-gasifier models for predicting calciner output based on different RDFs.
Scientific characterization methods for better utilization of cattle dung and urine: a concise review
(Springer, 2023-07) Sheth, Pratik N.; Yadav, Sushil Kumar
Cattle are usually raised for food, manure, leather, therapeutic, and draught purposes. Biowastes from cattle, such as dung and urine, harbor a diverse group of crucial compounds, metabolites/chemicals, and microorganisms that may benefit humans for agriculture, nutrition, therapeutics, industrial, and other utility products. Several bioactive compounds have been identified in cattle dung and urine, which possess unique properties and may vary based on agro-climatic zones and feeding practices. Therefore, cattle dung and urine have great significance, and a balanced nutritional diet may be a key to improved quality of these products/by-products. This review primarily focuses on the scientific aspects of biochemical and microbial characterization of cattle biowastes. Various methods including genomics for analyzing cattle dung and gas chromatography-mass spectroscopy for cattle urine have been reviewed. The presented information might open doors for the further characterization of cattle resources for heterogeneous applications in the production of utility items and addressing research gaps.
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.