Malay Karmakar - Academia.edu (original) (raw)

Papers by Malay Karmakar

Journal of energy and environmental sustainability, Jul 31, 2016

Dual fluidized bed gasification (DFBG) technology is a promising option to produce medium calorif... more Dual fluidized bed gasification (DFBG) technology is a promising option to produce medium calorific value N 2-free fuel gas. The present study deals with the development of a self sustaining lab scale are shown below DFBG consisting of a bubbling fluidized bed gasifier and a fast bed combustor, coupled through L-valves. Stable operation of this set up can be achieved by supplying liquefied petroleum gas to the combustor to generate N 2 free syngas in the gasifier. Rice husk was used as the feedstock, steam as the gasifying agent. Experimental investigation includes a parametric study of process parameters such as gasifier temperature and steam flow rate. H 2 concentration increases with higher gasification temperature and higher steam flow. CO concentration increases with increasing gasification temperature but decrease with higher steam flow. Higher heating value of fuel gas, char conversion and cold gas efficiency has been analyzed as performance indicators of the system.

Waste coal production is an important worldwide issue, especially in India. Indian waste coal has... more Waste coal production is an important worldwide issue, especially in India. Indian waste coal has great importance due to the increase of production in latest years. With the increasing demand of high-quality coal, waste category coals also can be used for combustion and chemical production. Indian waste coal is usually featured with high moisture content, high ash content and low carbon content, which especially exhibits high volatile and low heating value. The physio-chemical analysis (proximate and ultimate analysis) of Indian waste coal were carried out as per ASTM-D 5373 and results shows that the volatile matter, fixed carbon, ash contents and moisture contents are in the range of (14-16%), (5-8%), (73-79%) and (2-3%), respectively, with a moderate amount of carbon contents (10-15%). The present review article provides a comprehensive overview of the various thermal treatments and advanced technologies, characterization of Indian waste coal (proximate and ultimate analysis) for the possibility of using waste category coal as a fuel. The review starts from basic aspects of the process such as important operating parameters than focus on comparative analysis of the utilization of Indian waste coal with their characterization and the environmental performances of different fluidized-bed gasifiers. The analysis indicates that gasification and pyrolysis are technically viable

IOP conference series, Dec 7, 2019

In this study Indian coal material were used for the experiments and presents the results from ga... more In this study Indian coal material were used for the experiments and presents the results from gasification of Indian sub-bituminous coal in a (4.0 m tall X 0.75 m diameter) circulating fluidized bed gasifier. All the experiments were performed at the temperature range 700-800 °C. A number of experiments were carried out to see the effect of different parameters like coal feed rate, coal particle size on the quality of syngas production during the gasification of coal in circulating fluidized bed gasifier. All the above parametric study performed on three different superficial velocities of 5, 6 and 7 m/s. During the experiments coal feed rate was in the range of 0.036-0.073 g/s and coal particle size was varied from 80-212 mm respectively. With this experiment it is found that with increasing the superficial velocity, the solid circulation rate of material increases as well as with increases in solid inventory. It is observed that coal particle size also affect the heat transfer coefficient means it is decreases with increase the size of coal particle.

Thermal science and engineering progress, Aug 1, 2020

The thermal degradation and kinetics of coal is a key element for the design of pyrolysis process... more The thermal degradation and kinetics of coal is a key element for the design of pyrolysis process. In order to optimize the particle size effect on coal conversion and reaction kinetics, this research work elucidates the thermal degradation and reaction kinetics of Indian coal with different particle size (106-150, 212-300, 300-425, 425-600 and 600-1000 µm). The pyrolysis behaviours of different particle size coal were investigated through thermo-gravimetric analysis (TGA) under various heating rates with the temperature range 30°C to 950°C. The kinetic parameters were calculated using an iso-conversional model free Ozawa-Flynn-Wall (OFW) analysis. All the experimental results obtained from TGA, were validated with model prediction for all four heating rates. Good agreement with model prediction was found for all experimental TGA data. The results showed that the particle size of the coal sample remarkably affects the mass loss with the change in heating rate. These findings can provide the crucial data for the different industrial applications such as designing, handling and modelling of different coal gasifiers as well as other pyrolysis and gasification process. Our results also reveal that the Ozawa-Flynn-Wall approach used for coal kinetics helps significantly to calculate the meaningful activation energy.

International Journal of Coal Science & Technology, Jan 23, 2019

The present research work deals with the thermogravimetric analysis (TGA) and kinetic analysis of... more The present research work deals with the thermogravimetric analysis (TGA) and kinetic analysis of three typical Indian low rank coals selected from Indian coal mines at various temperature ranges. Experiments were performed at four different heating rate (50, 100, 150, 200 K/min) for three typical Indian low rank coal samples in a nitrogen atmosphere from temperature range 30-950°C. The peak of temperature and mass loss for Indian low rank coal were evaluated. Current study also deals for the utilization and the behaviour of Indian low rank coal during the pyrolysis by using TGA. The activation energy for Indian low rank coal were calculated based on TGA data by using Friedman Method. Corresponding calculated mean value of activation energy for Indian low rank coal is found 49.132 kJ/mol. These experimental results help to explain and predict the behaviour of Indian low rank coal in practical applications.

Elsevier eBooks, 2021

Abstract Waste coal is the starting phase of coal transformation, which has less carbon (20%) wit... more Abstract Waste coal is the starting phase of coal transformation, which has less carbon (20%) with high moisture content (4%–6%) and is less volatile (12%) compared to bituminous coal. It burns like wood but generates minimum heat and release more smoke and ash. However, in spite of waste coal quality, it has not been as widely used as other good rank coal. Generally, waste coal has one or more unwanted challenges such as low calorific value and high moisture and high ash content along with very low ash fusibility that causes fouling potential. In this chapter, utilization of waste coal with detailed reaction kinetics is discussed. The few case studies available on kinetics of waste coal reveal that adding chemical additives and blending with waste coal can effectively improve the slurry ability and thermal degradation. The blending of waste coal with biomass offers carbon neutrality for further development of cofiring system. The mechanism for waste coal utilization for energy generation is also discussed in this chapter.

Journal of Applied Fluid Mechanics, Jul 1, 2017

Cyclones are one of the most widely used gas-solid separators in circulating fluidized bed (CFB) ... more Cyclones are one of the most widely used gas-solid separators in circulating fluidized bed (CFB) systems. This paper focuses on numerical study of the gas-solid flow in a cyclone attached to the CFB system. The objective was to understand the flow pattern in the cyclone in order to run the CFB setup problem free. The previous works on cyclone separators do not include critical parameter such as coefficient of restitution which is responsible for swirling effect and increase in efficiency. Reynolds stress model (RSM) is used to obtain the gas flow characteristics. The resulting flow and pressure fields are verified by comparing with the measured experimental results and then used in the determination of solids flow that is simulated by the use of a discrete phase model. The simulation results show how the particle trajectories and cyclone efficiency change with varying coefficient of restitution and particle size keeping inlet velocity of gas and mean particle diameter constant. The separation efficiency, pressure drop and particle trapping time from the numerical analysis are shown to be comparable to those observed experimentally. The velocity distribution pattern obtained from the analysis exhibits strong flow recirculation with large turbulent eddies in the cyclone separator. The particle trajectories depend upon relative velocity of fluid/particles and concentration of particles. Efficiency of the cyclone is found to be dependent on particle size and coefficient of restitution. The results obtained are further utilized to optimize the velocity range of gas flow in the loop seal and riser for stable operation of CFB setup.

Advanced Powder Technology, Sep 1, 2010

The hydrodynamics of a circulating fluidized bed gasification system with dual fluidized bed conc... more The hydrodynamics of a circulating fluidized bed gasification system with dual fluidized bed concept has been studied through a cold model investigation. The article focuses on the axial voidage, the pressure drops across various components and the solid circulation under different operating conditions. The control of solids circulation between the dual fluidized beds has been done through an L-valve system. A mathematical model of hydrodynamic behavior of the system has been presented. It is observed from the investigated operating parameters that the aeration flow, the secondary air flow and particle diameter have the strongest influence on system pressure drop and solid circulation.

Journal of Thermal Analysis and Calorimetry, Nov 21, 2021

In this work, a comprehensive and systematic study on synergistic effect and kinetics of three co... more In this work, a comprehensive and systematic study on synergistic effect and kinetics of three coal ranks (anthracite coal, bituminous coal, and waste coal), and three biomass materials (wheat straw, sawdust, groundnut) were performed under different blending ratios. The kinetic parameters of coal and biomass devolatilization were estimated by means of thermogravimetric analysis (TGA) at 10, 20, 30 and 40 Kmin−1. These kinetic parameters were subsequently validated using Artificial Neural Network (ANN) Model. Further, for fitting the experimental data, a numerical approach to distributed activation energy model (DAEM) has been evaluated and the experimental findings were compared with simulated data. Subsequently, the kinetic and thermodynamic parameters were estimated and compared with three model-free methods viz., KAS, OFW, and Friedman. The results from TG study indicate that the interactions between the waste coal with higher rank coal and biomass samples present an inhibitive effect during the devolatilization process. Furthermore, the values of activation energy were found in the range of 270, 250, 149 kJmol−1 by using OFW, KAS and Friedman model, respectively. Additionally, the thermodynamic parameters viz., enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS) were estimated as 275.2 kJ mol−1, 184.5 kJmol−1, and 59.7 Jmol−1, respectively.

Advanced Powder Technology, 2018

Chemical Looping Combustion (CLC) in two interconnected fluidized beds, i.e., the air reactor and... more Chemical Looping Combustion (CLC) in two interconnected fluidized beds, i.e., the air reactor and the fuel 32 reactor has been recognized to be promising. As the CLC setup design is critical and sensitive to oxygen 33 carrier (OC) materials, it is very much essential to investigate hydrodynamics in a specially fabricated 34 cold model set up for the successful development and operational control of corresponding large-scale 35 hot model. In this study, a pilot-scale cold flow model CLC system has been designed and tested. The riser 36 and fuel reactor were operated at circulated fluidized bed and bubbling fluidized bed conditions, respec-37 tively and the control of solid circulation between two reactors was done by two loop seals operated in 38 bubbling fluidized bed conditions. The effect of fluidization velocity in the riser on the voidage profiles, 39 solid circulation rate, and pressure profiles were investigated using Indian ilmenite (150-212 µm) as OC. 40 The stable operation of the system was established under various operational conditions. The results will 41 be useful for the development of ilmenite based hot model CLC system. Moreover, the achievable varia-42 tions of solid circulation rate in the present study in cold model setup will determine obtainable limit of 43 extent of oxygen transport and thermal energy.

Environmental Science and Pollution Research, Mar 23, 2023

Among all subsystems ofa solar thermal energy system, thereceiverplays a major role while getting... more Among all subsystems ofa solar thermal energy system, thereceiverplays a major role while getting the heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy being collected by the receiver, which ismainlycharacterised by the optical parameters likefocal length, aperture diameter, surface absorptivity and slope error. In this paper,the optical analysis of a cylindricalhemispherical type receiver coupled with a3m diameter parabolic dish concentrator has been discussed. The studyhas been carried out using SolTracesoftware by varying the parameters likereceiver aperture diameter (D a) ranging from 0.125 to 0.162 m, surface error of the concentrator from 1.7453 to 34.907mrad and also surface absorptivity (α) from 75% to 95%for different receiver distances(H) ranging from 1.7 to 1.95m. From the simulation results, it is observed that the optical e ciency is maximum when the receiver distance is 1.85m for receiver aperture diameter of 0.150 m for the given system. Increase in the slope errors from 1.7453 to 17.453 mrad decreases the average optical e ciency by almost 50% for all receiver diameters.It is alsonoticed that uniform heat ux distribution can be achieved when the position of the receiver is maintained at H = 1.85 m from the concentrator for the given receiver diameterand surface absorptivity of the receiver of 0.150 m and 95% respectively.The simulated results of heat ux intensity on the receiver surface are then compared and validated by the experimental results available in literature. The simulatedoptical e ciency of the presentreceiver is also found to be 8% higher when it is compared with a conventional cylindrical receiver having similardimensions. Highlights 1. The manuscript investigates the various performance parameters affecting the optical e ciency of a cylindrical-hemispehrical type receiver used in a solar thermal system having a parabolic dish concentrator, as there is very limited information available specially on this type of receiver in published literature. 2. The present investigation is based on simulation study considering the present system and the obtained results are brie y highlighted belowa. The effect of receiver aperture diameter was investigated with varying receiver diatances from the concentrator and it was observed that the optical e ciency is maximum when the receiver is maintained at 1.85m for receiver aperture diameter of 0.150 m. b. It was observed that higher slope error of the concentrator deteriorates the optical e ciency. The simulated results show that the average decrease in the optical e ciencies is about 50% for increase in slope errors from 1.7453 to 17.453 mrad for all receiver diameters. c. The receiver absorptivity was also found to in uence the optical e ciency and it was seen that the receiver having 95% absorptivity has the optical e ciency is 62.31%. 3. The simulated results of heat ux intensity on the receiver are compared and validated by the experimental results available in literature. Page 3/28 4. In this manuscript, the performance of the cylindrical-hemispherical receiver has also been compared with a conventional cyldrical receiver with similar dimensions and it was observed that the present receiver is 8% more optically e cient than a conventional cylindrical receiver for the given range of parameters.

Environmental Science and Pollution Research

Among all sub-systems ofa solar thermal energy system, thereceiverplays a major role while gettin... more Among all sub-systems ofa solar thermal energy system, thereceiverplays a major role while getting the heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy being collected by the receiver, which ismainlycharacterised by the optical parameters likefocal length, aperture diameter, surface absorptivity and slope error. In this paper,the optical analysis of a cylindrical-hemispherical type receiver coupled with a3m diameter parabolic dish concentrator has been discussed. The studyhas been carried out using SolTracesoftware by varying the parameters likereceiver aperture diameter (Da) ranging from 0.125 to 0.162 m, surface error of the concentrator from 1.7453 to 34.907mrad and also surface absorptivity (α) from 75% to 95%for different receiver distances(H) ranging from 1.7 to 1.95m. From the simulation results, it is observed that the optical efficiency is maximum when the receiver distance is 1.85m for receiver aperture diameter of 0....

Lecture Notes in Civil Engineering, 2020

Sheet materials, which are commonly used in sectors such as automotive and whitewares, are usuall... more Sheet materials, which are commonly used in sectors such as automotive and whitewares, are usually formed by applying bending operations. The most important problem encountered in bending processes is springback. Springback problem arising from elastic behavior of the material complicates the assembly of manufactured part due to dimensional differences and causes financial loss. For this reason, it is required to properly estimate the springback behavior to provide the dimensional integrity and cost savings of the shaped parts as a result of the bending operations. In this study, the springback behavior of DC series sheet metals forming by V bending was experimentally investigated the different process parameter of material quality, thickness, rolling direction and die angle. The sheet metals have the quality of DC01, DC04 and DC05 and the thickness of 1, 1.5 and 2 mm. The Vbending dies have 60, 90 and 120 o angles. From the experimental studies, it is seen that the behavior of springback changes depending on the die and the process parameters.

Encyclopedia of Renewable and Sustainable Materials, 2020

Coal and Biomass Gasification, 2017

Carbonaceous solid materials are converted into gaseous fuel through the gasification process. A ... more Carbonaceous solid materials are converted into gaseous fuel through the gasification process. A limited supply of steam, air, oxygen, or a combination of these serves as gasifying agent. Depending upon the gasifying agent used, the fuel gas will contain mainly hydrogen, carbon monoxide, carbon dioxide, methane, higher hydrocarbons, and nitrogen (if air is used). In gasification, different technologies are used depending upon the requirement. Technologies used for gasification can broadly be classified into four groups; fixed bed or moving bed gasification, fluidized bed gasification, entrained bed gasification, and plasma gasification. In the present chapter, a detail discussion on the design, working principle, merits and demerits of different types of gasifiers are presented. Some of the important commercial gasifiers installed worldwide are also discussed.

Coal and Biomass Gasification, 2017

Fluidized bed reactors are used in different industries to carry out multiphase chemical reaction... more Fluidized bed reactors are used in different industries to carry out multiphase chemical reactions. In these reactors, the fluid is passed through the reactor bed having granular solid materials. The velocity of the fluid is kept high enough to suspend these materials resulting to behave them like fluids. Such reactors are classified as bubbling bed, fast circulating bed or dual bed systems combining two beds depending upon the fluid velocities and constructions of the reactors. For combustion and gasification processes, circulating or dual fluidized bed systems are often preferred because they are more efficient having high throughput. However, the hydrodynamics of such fluidized beds, using normally low-grade feedstocks, is very complex and plays a critical role for successful operation of the plant. Lots of experimental and theoretical investigations are done in this area; however, the available information on the hydrodynamics is limited. In this chapter, the hydrodynamics of circulating fluidized bed systems has been discussed.

Advances in Mechanical Engineering, 2020

With the ever increasing growth in population across the nation, there is a need for proper dispo... more With the ever increasing growth in population across the nation, there is a need for proper disposal of solid waste of households. A comprehensive literature survey was conducted to study the status of sewage treatment plants (STP) in different states of India. More emphasis was laid on its status in different districts of Bihar. Existing plants are incapable of handling huge inflow of wastes through sewage pipe lines. If properly developed, STP could not only remove the problem of waste management but it will also provide financial gains. Biogas produced in most of these plants from the digesters is flared off and are not being stored, if done will certainly reduce the cost of cooking fuel. Only primary and secondary treatment of the plants is being done in most of the sewage treatment plants. If tertiary treatment is also provided, this might help in solving the problem of safe drinking water. Conventionally, these left over sludge from the digester still contains a lot of carbona...

Journal of energy and environmental sustainability, Jul 31, 2016

Dual fluidized bed gasification (DFBG) technology is a promising option to produce medium calorif... more Dual fluidized bed gasification (DFBG) technology is a promising option to produce medium calorific value N 2-free fuel gas. The present study deals with the development of a self sustaining lab scale are shown below DFBG consisting of a bubbling fluidized bed gasifier and a fast bed combustor, coupled through L-valves. Stable operation of this set up can be achieved by supplying liquefied petroleum gas to the combustor to generate N 2 free syngas in the gasifier. Rice husk was used as the feedstock, steam as the gasifying agent. Experimental investigation includes a parametric study of process parameters such as gasifier temperature and steam flow rate. H 2 concentration increases with higher gasification temperature and higher steam flow. CO concentration increases with increasing gasification temperature but decrease with higher steam flow. Higher heating value of fuel gas, char conversion and cold gas efficiency has been analyzed as performance indicators of the system.

Waste coal production is an important worldwide issue, especially in India. Indian waste coal has... more Waste coal production is an important worldwide issue, especially in India. Indian waste coal has great importance due to the increase of production in latest years. With the increasing demand of high-quality coal, waste category coals also can be used for combustion and chemical production. Indian waste coal is usually featured with high moisture content, high ash content and low carbon content, which especially exhibits high volatile and low heating value. The physio-chemical analysis (proximate and ultimate analysis) of Indian waste coal were carried out as per ASTM-D 5373 and results shows that the volatile matter, fixed carbon, ash contents and moisture contents are in the range of (14-16%), (5-8%), (73-79%) and (2-3%), respectively, with a moderate amount of carbon contents (10-15%). The present review article provides a comprehensive overview of the various thermal treatments and advanced technologies, characterization of Indian waste coal (proximate and ultimate analysis) for the possibility of using waste category coal as a fuel. The review starts from basic aspects of the process such as important operating parameters than focus on comparative analysis of the utilization of Indian waste coal with their characterization and the environmental performances of different fluidized-bed gasifiers. The analysis indicates that gasification and pyrolysis are technically viable

IOP conference series, Dec 7, 2019

In this study Indian coal material were used for the experiments and presents the results from ga... more In this study Indian coal material were used for the experiments and presents the results from gasification of Indian sub-bituminous coal in a (4.0 m tall X 0.75 m diameter) circulating fluidized bed gasifier. All the experiments were performed at the temperature range 700-800 °C. A number of experiments were carried out to see the effect of different parameters like coal feed rate, coal particle size on the quality of syngas production during the gasification of coal in circulating fluidized bed gasifier. All the above parametric study performed on three different superficial velocities of 5, 6 and 7 m/s. During the experiments coal feed rate was in the range of 0.036-0.073 g/s and coal particle size was varied from 80-212 mm respectively. With this experiment it is found that with increasing the superficial velocity, the solid circulation rate of material increases as well as with increases in solid inventory. It is observed that coal particle size also affect the heat transfer coefficient means it is decreases with increase the size of coal particle.

Thermal science and engineering progress, Aug 1, 2020

The thermal degradation and kinetics of coal is a key element for the design of pyrolysis process... more The thermal degradation and kinetics of coal is a key element for the design of pyrolysis process. In order to optimize the particle size effect on coal conversion and reaction kinetics, this research work elucidates the thermal degradation and reaction kinetics of Indian coal with different particle size (106-150, 212-300, 300-425, 425-600 and 600-1000 µm). The pyrolysis behaviours of different particle size coal were investigated through thermo-gravimetric analysis (TGA) under various heating rates with the temperature range 30°C to 950°C. The kinetic parameters were calculated using an iso-conversional model free Ozawa-Flynn-Wall (OFW) analysis. All the experimental results obtained from TGA, were validated with model prediction for all four heating rates. Good agreement with model prediction was found for all experimental TGA data. The results showed that the particle size of the coal sample remarkably affects the mass loss with the change in heating rate. These findings can provide the crucial data for the different industrial applications such as designing, handling and modelling of different coal gasifiers as well as other pyrolysis and gasification process. Our results also reveal that the Ozawa-Flynn-Wall approach used for coal kinetics helps significantly to calculate the meaningful activation energy.

International Journal of Coal Science & Technology, Jan 23, 2019

The present research work deals with the thermogravimetric analysis (TGA) and kinetic analysis of... more The present research work deals with the thermogravimetric analysis (TGA) and kinetic analysis of three typical Indian low rank coals selected from Indian coal mines at various temperature ranges. Experiments were performed at four different heating rate (50, 100, 150, 200 K/min) for three typical Indian low rank coal samples in a nitrogen atmosphere from temperature range 30-950°C. The peak of temperature and mass loss for Indian low rank coal were evaluated. Current study also deals for the utilization and the behaviour of Indian low rank coal during the pyrolysis by using TGA. The activation energy for Indian low rank coal were calculated based on TGA data by using Friedman Method. Corresponding calculated mean value of activation energy for Indian low rank coal is found 49.132 kJ/mol. These experimental results help to explain and predict the behaviour of Indian low rank coal in practical applications.

Elsevier eBooks, 2021

Abstract Waste coal is the starting phase of coal transformation, which has less carbon (20%) wit... more Abstract Waste coal is the starting phase of coal transformation, which has less carbon (20%) with high moisture content (4%–6%) and is less volatile (12%) compared to bituminous coal. It burns like wood but generates minimum heat and release more smoke and ash. However, in spite of waste coal quality, it has not been as widely used as other good rank coal. Generally, waste coal has one or more unwanted challenges such as low calorific value and high moisture and high ash content along with very low ash fusibility that causes fouling potential. In this chapter, utilization of waste coal with detailed reaction kinetics is discussed. The few case studies available on kinetics of waste coal reveal that adding chemical additives and blending with waste coal can effectively improve the slurry ability and thermal degradation. The blending of waste coal with biomass offers carbon neutrality for further development of cofiring system. The mechanism for waste coal utilization for energy generation is also discussed in this chapter.

Journal of Applied Fluid Mechanics, Jul 1, 2017

Cyclones are one of the most widely used gas-solid separators in circulating fluidized bed (CFB) ... more Cyclones are one of the most widely used gas-solid separators in circulating fluidized bed (CFB) systems. This paper focuses on numerical study of the gas-solid flow in a cyclone attached to the CFB system. The objective was to understand the flow pattern in the cyclone in order to run the CFB setup problem free. The previous works on cyclone separators do not include critical parameter such as coefficient of restitution which is responsible for swirling effect and increase in efficiency. Reynolds stress model (RSM) is used to obtain the gas flow characteristics. The resulting flow and pressure fields are verified by comparing with the measured experimental results and then used in the determination of solids flow that is simulated by the use of a discrete phase model. The simulation results show how the particle trajectories and cyclone efficiency change with varying coefficient of restitution and particle size keeping inlet velocity of gas and mean particle diameter constant. The separation efficiency, pressure drop and particle trapping time from the numerical analysis are shown to be comparable to those observed experimentally. The velocity distribution pattern obtained from the analysis exhibits strong flow recirculation with large turbulent eddies in the cyclone separator. The particle trajectories depend upon relative velocity of fluid/particles and concentration of particles. Efficiency of the cyclone is found to be dependent on particle size and coefficient of restitution. The results obtained are further utilized to optimize the velocity range of gas flow in the loop seal and riser for stable operation of CFB setup.

Advanced Powder Technology, Sep 1, 2010

The hydrodynamics of a circulating fluidized bed gasification system with dual fluidized bed conc... more The hydrodynamics of a circulating fluidized bed gasification system with dual fluidized bed concept has been studied through a cold model investigation. The article focuses on the axial voidage, the pressure drops across various components and the solid circulation under different operating conditions. The control of solids circulation between the dual fluidized beds has been done through an L-valve system. A mathematical model of hydrodynamic behavior of the system has been presented. It is observed from the investigated operating parameters that the aeration flow, the secondary air flow and particle diameter have the strongest influence on system pressure drop and solid circulation.

Journal of Thermal Analysis and Calorimetry, Nov 21, 2021

In this work, a comprehensive and systematic study on synergistic effect and kinetics of three co... more In this work, a comprehensive and systematic study on synergistic effect and kinetics of three coal ranks (anthracite coal, bituminous coal, and waste coal), and three biomass materials (wheat straw, sawdust, groundnut) were performed under different blending ratios. The kinetic parameters of coal and biomass devolatilization were estimated by means of thermogravimetric analysis (TGA) at 10, 20, 30 and 40 Kmin−1. These kinetic parameters were subsequently validated using Artificial Neural Network (ANN) Model. Further, for fitting the experimental data, a numerical approach to distributed activation energy model (DAEM) has been evaluated and the experimental findings were compared with simulated data. Subsequently, the kinetic and thermodynamic parameters were estimated and compared with three model-free methods viz., KAS, OFW, and Friedman. The results from TG study indicate that the interactions between the waste coal with higher rank coal and biomass samples present an inhibitive effect during the devolatilization process. Furthermore, the values of activation energy were found in the range of 270, 250, 149 kJmol−1 by using OFW, KAS and Friedman model, respectively. Additionally, the thermodynamic parameters viz., enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS) were estimated as 275.2 kJ mol−1, 184.5 kJmol−1, and 59.7 Jmol−1, respectively.

Advanced Powder Technology, 2018

Chemical Looping Combustion (CLC) in two interconnected fluidized beds, i.e., the air reactor and... more Chemical Looping Combustion (CLC) in two interconnected fluidized beds, i.e., the air reactor and the fuel 32 reactor has been recognized to be promising. As the CLC setup design is critical and sensitive to oxygen 33 carrier (OC) materials, it is very much essential to investigate hydrodynamics in a specially fabricated 34 cold model set up for the successful development and operational control of corresponding large-scale 35 hot model. In this study, a pilot-scale cold flow model CLC system has been designed and tested. The riser 36 and fuel reactor were operated at circulated fluidized bed and bubbling fluidized bed conditions, respec-37 tively and the control of solid circulation between two reactors was done by two loop seals operated in 38 bubbling fluidized bed conditions. The effect of fluidization velocity in the riser on the voidage profiles, 39 solid circulation rate, and pressure profiles were investigated using Indian ilmenite (150-212 µm) as OC. 40 The stable operation of the system was established under various operational conditions. The results will 41 be useful for the development of ilmenite based hot model CLC system. Moreover, the achievable varia-42 tions of solid circulation rate in the present study in cold model setup will determine obtainable limit of 43 extent of oxygen transport and thermal energy.

Environmental Science and Pollution Research, Mar 23, 2023

Among all subsystems ofa solar thermal energy system, thereceiverplays a major role while getting... more Among all subsystems ofa solar thermal energy system, thereceiverplays a major role while getting the heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy being collected by the receiver, which ismainlycharacterised by the optical parameters likefocal length, aperture diameter, surface absorptivity and slope error. In this paper,the optical analysis of a cylindricalhemispherical type receiver coupled with a3m diameter parabolic dish concentrator has been discussed. The studyhas been carried out using SolTracesoftware by varying the parameters likereceiver aperture diameter (D a) ranging from 0.125 to 0.162 m, surface error of the concentrator from 1.7453 to 34.907mrad and also surface absorptivity (α) from 75% to 95%for different receiver distances(H) ranging from 1.7 to 1.95m. From the simulation results, it is observed that the optical e ciency is maximum when the receiver distance is 1.85m for receiver aperture diameter of 0.150 m for the given system. Increase in the slope errors from 1.7453 to 17.453 mrad decreases the average optical e ciency by almost 50% for all receiver diameters.It is alsonoticed that uniform heat ux distribution can be achieved when the position of the receiver is maintained at H = 1.85 m from the concentrator for the given receiver diameterand surface absorptivity of the receiver of 0.150 m and 95% respectively.The simulated results of heat ux intensity on the receiver surface are then compared and validated by the experimental results available in literature. The simulatedoptical e ciency of the presentreceiver is also found to be 8% higher when it is compared with a conventional cylindrical receiver having similardimensions. Highlights 1. The manuscript investigates the various performance parameters affecting the optical e ciency of a cylindrical-hemispehrical type receiver used in a solar thermal system having a parabolic dish concentrator, as there is very limited information available specially on this type of receiver in published literature. 2. The present investigation is based on simulation study considering the present system and the obtained results are brie y highlighted belowa. The effect of receiver aperture diameter was investigated with varying receiver diatances from the concentrator and it was observed that the optical e ciency is maximum when the receiver is maintained at 1.85m for receiver aperture diameter of 0.150 m. b. It was observed that higher slope error of the concentrator deteriorates the optical e ciency. The simulated results show that the average decrease in the optical e ciencies is about 50% for increase in slope errors from 1.7453 to 17.453 mrad for all receiver diameters. c. The receiver absorptivity was also found to in uence the optical e ciency and it was seen that the receiver having 95% absorptivity has the optical e ciency is 62.31%. 3. The simulated results of heat ux intensity on the receiver are compared and validated by the experimental results available in literature. Page 3/28 4. In this manuscript, the performance of the cylindrical-hemispherical receiver has also been compared with a conventional cyldrical receiver with similar dimensions and it was observed that the present receiver is 8% more optically e cient than a conventional cylindrical receiver for the given range of parameters.

Environmental Science and Pollution Research

Among all sub-systems ofa solar thermal energy system, thereceiverplays a major role while gettin... more Among all sub-systems ofa solar thermal energy system, thereceiverplays a major role while getting the heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy being collected by the receiver, which ismainlycharacterised by the optical parameters likefocal length, aperture diameter, surface absorptivity and slope error. In this paper,the optical analysis of a cylindrical-hemispherical type receiver coupled with a3m diameter parabolic dish concentrator has been discussed. The studyhas been carried out using SolTracesoftware by varying the parameters likereceiver aperture diameter (Da) ranging from 0.125 to 0.162 m, surface error of the concentrator from 1.7453 to 34.907mrad and also surface absorptivity (α) from 75% to 95%for different receiver distances(H) ranging from 1.7 to 1.95m. From the simulation results, it is observed that the optical efficiency is maximum when the receiver distance is 1.85m for receiver aperture diameter of 0....

Lecture Notes in Civil Engineering, 2020

Sheet materials, which are commonly used in sectors such as automotive and whitewares, are usuall... more Sheet materials, which are commonly used in sectors such as automotive and whitewares, are usually formed by applying bending operations. The most important problem encountered in bending processes is springback. Springback problem arising from elastic behavior of the material complicates the assembly of manufactured part due to dimensional differences and causes financial loss. For this reason, it is required to properly estimate the springback behavior to provide the dimensional integrity and cost savings of the shaped parts as a result of the bending operations. In this study, the springback behavior of DC series sheet metals forming by V bending was experimentally investigated the different process parameter of material quality, thickness, rolling direction and die angle. The sheet metals have the quality of DC01, DC04 and DC05 and the thickness of 1, 1.5 and 2 mm. The Vbending dies have 60, 90 and 120 o angles. From the experimental studies, it is seen that the behavior of springback changes depending on the die and the process parameters.

Encyclopedia of Renewable and Sustainable Materials, 2020

Coal and Biomass Gasification, 2017

Carbonaceous solid materials are converted into gaseous fuel through the gasification process. A ... more Carbonaceous solid materials are converted into gaseous fuel through the gasification process. A limited supply of steam, air, oxygen, or a combination of these serves as gasifying agent. Depending upon the gasifying agent used, the fuel gas will contain mainly hydrogen, carbon monoxide, carbon dioxide, methane, higher hydrocarbons, and nitrogen (if air is used). In gasification, different technologies are used depending upon the requirement. Technologies used for gasification can broadly be classified into four groups; fixed bed or moving bed gasification, fluidized bed gasification, entrained bed gasification, and plasma gasification. In the present chapter, a detail discussion on the design, working principle, merits and demerits of different types of gasifiers are presented. Some of the important commercial gasifiers installed worldwide are also discussed.

Coal and Biomass Gasification, 2017

Fluidized bed reactors are used in different industries to carry out multiphase chemical reaction... more Fluidized bed reactors are used in different industries to carry out multiphase chemical reactions. In these reactors, the fluid is passed through the reactor bed having granular solid materials. The velocity of the fluid is kept high enough to suspend these materials resulting to behave them like fluids. Such reactors are classified as bubbling bed, fast circulating bed or dual bed systems combining two beds depending upon the fluid velocities and constructions of the reactors. For combustion and gasification processes, circulating or dual fluidized bed systems are often preferred because they are more efficient having high throughput. However, the hydrodynamics of such fluidized beds, using normally low-grade feedstocks, is very complex and plays a critical role for successful operation of the plant. Lots of experimental and theoretical investigations are done in this area; however, the available information on the hydrodynamics is limited. In this chapter, the hydrodynamics of circulating fluidized bed systems has been discussed.

Advances in Mechanical Engineering, 2020

With the ever increasing growth in population across the nation, there is a need for proper dispo... more With the ever increasing growth in population across the nation, there is a need for proper disposal of solid waste of households. A comprehensive literature survey was conducted to study the status of sewage treatment plants (STP) in different states of India. More emphasis was laid on its status in different districts of Bihar. Existing plants are incapable of handling huge inflow of wastes through sewage pipe lines. If properly developed, STP could not only remove the problem of waste management but it will also provide financial gains. Biogas produced in most of these plants from the digesters is flared off and are not being stored, if done will certainly reduce the cost of cooking fuel. Only primary and secondary treatment of the plants is being done in most of the sewage treatment plants. If tertiary treatment is also provided, this might help in solving the problem of safe drinking water. Conventionally, these left over sludge from the digester still contains a lot of carbona...