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A slit-less gas-solid vortex reactor (SL-RFBSG) has high heat and mass transfer capability, applicable in pharmaceutical and food processing industries, especially in food grain drying and preservation. Validating the numerical outcomes with experimental results of the SL-GSVR vortex chamber with a capacity of 500 g, the scale-up of this reactor is performed numerically to a solid capacity of 3000 g. In the present investigation, a three-dimensional computational fluid dynamics analysis of gas-solid hydrodynamics and heat transfer characteristics in SL-GSVR has been performed using the commercial software ANSYS FLUENT 14.5, applying an Eulerian-Eulerian approach for the gas-solid phase. As the SL-GSVR vortex chamber is developed without slits, it improves bed-uniformity and fluidization, along with the reduction in system cost and complexity. Comparing numerical outcomes with experimental results, the measured temperature difference, inventory, heat transfer coefficient in the radial direction and transverse directions are 0.24%, 7.72%, 14.8%, and 17.8%, respectively. The requirement of drying air in the SL-GSVR dryer is decreased by 18.6%, with an improvement in the product quality compared to the RFB reactor. Further, the solid loading capacity of the scaled-up SL-GSVR drying chamber has been increased to 3000 g.

The present research is focused on the gasification study of a lab-scale pressurized circulating fluidized bed (PCFB) gasifier considering low-grade Indian coal and biomass such as sawdust and rice husk with a mean particle size of 600 μ m as feed materials. Syngas composition, lower heating value (LHV), dry gas yield (Y), carbon conversion efficiency (CCE), and cold gas efficiency (CGE) are evaluated based on the experiments in the range of pressure 1–4 bar. It is observed that the concentration of CH4 increases with pressure for all the three feed materials. The concentration of CH4 is found to be increasing from (3.65–4.86 vol%) and (2.98–3.46 vol%) for sawdust and rice husk, respectively. Similarly, the LHV is found to be increasing with pressure for coal and sawdust. There is a significant increase of 12% in LHV with an increase in pressure from 1 to 4 bar for both coal and sawdust. The CGE is found to increase by 34, 51, and 61% for rice husk, coal and sawdust, respectively with the increase in pressure from 1 to 4 bar.

This paper reports gasification of coal/biomass blends in a pilot scale (50 kWe) air-blown circulating fluidized bed gasifier. Yardsticks for gasification performance are net yield, LHV and composition and tar content of producer gas, cold gas efficiency (CGE) and carbon conversion efficiency (CCE). Net LHV decreased with increasing equivalence ratio (ER) whereas CCE and CGE increased. Max gas yield (1.91 Nm3/kg) and least tar yield (5.61 g/kg of dry fuel) was obtained for coal biomass composition of 60:40 wt% at 800 °C. Catalytic effect of alkali and alkaline earth metals in biomass enhanced char and tar conversion for coal/biomass blend of 60:40 wt% at ER = 0.29, with CGE and CCE of 44% and 84%, respectively. Gasification of 60:40 wt% coal/biomass blend with dolomite (10 wt%, in-bed) gave higher gas yield (2.11 Nm3/kg) and H2 content (12.63 vol%) of producer gas with reduced tar content (4.3 g/kg dry fuel).

Growing concern about the rapid depletion of fossil fuels, current environmental conditions, energy challenges and new environmental regulations has encouraged the researchers worldwide for new environmentally compatible alternatives from natural resources. In this context, biogas produced from anaerobic digestion of organic resources may be considered as a significant bioenergy with the potential to address these concerns. Biogas is a mixture of methane and carbon dioxide as the major constituents with other trace components like water vapor, hydrogen sulfide, ammonia, carbon monoxide and nitrogen. Uses of biogas can be seen in heating, cooking, lighting and power production. However, cleaning of biogas from its impurities, mainly CO2 and H2S, can extend its scope of applications. There are numerous physico-chemical (viz. cryogenic, adsorption, membrane separations and absorption) and biological (in situ and ex situ) technologies for biogas upgradation. These operations are aimed at enriching the methane content of biogas above 90% and thereby enhancing the calorific value up to 35.3 MJ/m3. The purpose behind such upgrading is generally focused to meet the fuel standards to be used in vehicles, for injection in the natural gas grid, and to be used as substrate for the production of chemicals or for fuel cell applications. Enriched biogas is compressed and stocked in gas cylinder and transported to the desired location for utilization. Additionally, use of enriched biogas reduces greenhouse gas emissions. This chapter aims at meticulously evaluating the existing and emerging biogas production and upgradation technologies and confers the outlook for overcoming the challenges associated with them.

The velocity distribution in the axial direction of a conical fluidized bed is not uniform due to the expansion of cross-sectional area along the height. As such, the hydrodynamic and heat transfer characteristics of a tapered fluidized bed differ from that of the columnar fluidized bed. Various operating parameters have a significant effect on these characteristics. In this paper, the effect of bed inventory and airflow rate on the hydrodynamic and heat transfer characteristics in a columnar and conical are investigated and compared both experimentally and numerically. A Eulerian-Eulerian model is employed to investigate the hydrodynamics and heat transfer behaviour for both the types of bed. The Syamlal-O’Brien model is used as a drag model. The pressure drop across the bed is found to higher for the columnar bed. The heat transfer is also found to be better for the conical bed. Results obtained by experiments are seen to be excellent agreement with the numerical results.

Applying oxy-fuel combustion requires more advanced combustion control methods to avoid inadmissible high flam temperature. In fluidized beds and pulverized unites, enhanced heat transfer and recirculation flue gas are used. On other hand, higher oxygen concentration has pluses viz. better heat transfer, higher efficiency, compact setup and lower installation and operating costs. In pulverized power unites, pure oxy-fuel combustion is used with 100% O2 in the oxidant. In contrast, the highest experimental O2 % in oxy-fuel circulating fluidized bed (CFB) combustor is 70%. To the best of authors’ knowledge, there is no single CFB power plant operating under pure oxygen condition. In this work, we are aiming to use pure oxygen for oxy-CFB combustion, with new temperature controlling method for CFBs depending on combustion staging by fuel staging rather than using RFG. Fuel staging allows controlling combustion and varying SR. At the first stage, the used oxidant is 100% O2, and fuel is fed to achieve over SR (λ>1), where the excess oxidant absorbs heat and does not take a part in the reaction. The products of the first stage are reach of O2 and subsequently it is used as an oxidant for the second stage. For validation, a series of experiments are conducted using mini-CFB, and an oxidant of 100% O2 concentration is used with three SR ratios λ=1.25, 2.0, and 3.0. The resulted average temperatures along the riser for biomass are 1031°C, 950°C, and 798°C; and for coal 1129 °C, 1051 °C, and 961 °C respectively. The controlling of AFT with pure oxy-fuel combustion eliminates the recycled flue gas (RFG) in oxy-fuel CFB combustion and flue gas recirculation section; this simplifies the power plants’ design, fabrication and its installing-operating costs. Familiarising this concept can accelerate adapting oxy-fuel combustion in CFB power plant for Carbon Capturing and Sequestration (CCS). This contribution can commence and commercialise the third generation of oxy-fuel CFB combustion with zero recycled flue gas. Finally, the concept of controlling AFT by SR (λ) is validated experimentally.

A critical review and analysis of co-gasification of coal/biomass blends is presented. Initially, the chemistry of gasification of coal and biomass has been described along with different models for pyrolysis of cellulose/biomass. The mechanistic issues of catalytic effect of alkali metals on coal char gasification have been reviewed. This is followed by literature review on gasification of coal/biomass blends in two parts, viz. thermogravimetric and fluidized bed gasification. First part deals with effects of operational parameters on char reactivity. Second part analyzes influence of these parameters on gasification chemistry and producer gas. Factors governing tar content in producer gas have been discussed. Finally, the literature on kinetic modeling of coal/biomass blends has been analyzed. Some new approaches in kinetic modeling of solid-state reactions have been discussed.

The absorber plate and outlet water temperature of a solar flat plate collector with straight riser and header arrangement is investigated. The effect of different operating parameters, viz., inlet water temperature, solar insolation, ambient temperature, and mass flow rate on the outlet water temperature and thermal efficiency were studied. Both the closed as well as open loop solar water heating system is considered for the present investigation. It is observed that the thermal efficiency of the solar water heating system increases with ambient temperature, solar insolation, and mass flow rate of water. However, thermal efficiency decreases as inlet water temperature increases. Numerical simulations were carried out using a 3-dimensional computational fluid dynamics (CFD) to predict the outlet water and absorber plate temperatures using the experimental values of solar insolation, ambient temperature and inlet water temperature within one hour interval. The CFD results were validated with the experimental results. It was found that the developed model could predict the outlet water and absorber plate temperature of the heating system with reasonable accuracy.

Power generation from solar photovoltaic (PV) plants depends on multiple factors such as solar radiance and ambient temperature. Effective monitoring and control of the energy generated with the solar PV plants may augment the complete performance of the system. The local controllers regulate switching between solar PV, local battery, community battery, and grid according to the availability of power in each system. The sensor data and user information are stored in the cloud that can be accessed with the Internet of Things (IoT) device for further computation. A Web-based graphical user interface (GUI) has been developed for appropriate monitoring and control of energy flow and also to enable the power pooling. The app gets information from the cloud on which various sensor’s data regarding energy pooling are stored by the local/community controllers, and it displays the information that is stored in the cloud. The primary task is to design and develop a Web-based application with sufficient data security. To secure the user data in the cloud, multi-factor authentication and symmetric key encryption are used for authorized access and data encryption. The basic model of the Web-based application is presented in this paper.

The coupling of renewable energy systems has proven to be advantageous in achieving sustainable and reliable energy generation. In this study, the techno-economic and environmental assessment of a hybrid 1 kW solar photovoltaic (PV) plant (having battery backup) and a 3.5 kVA biogas fueled (BF) generator was investigated. The hybrid system was subjected to constant load conditions from 20% to 80% of the rated power conditioning unit (PCU), and energy shared by the combined systems was investigated. At lower loads, the photovoltaic system was sufficient to meet the demand. Whereas at higher loads, energy share from the biogas system was required for meeting the load demand. Economic analysis over a project lifetime of 25 years revealed a high positive net present value of $1562.15 with a Levelized cost of the energy value of $0.21/kWh for the hybrid system. A comparative financial analysis for the standalone solar photovoltaic system was also performed using the system advisor model (SAM). System advisor model analysis resulted in a positive net present value of $306.45 and a Levelized cost of the energy value of $0.15/kWh. The environmental analysis revealed net CO2 mitigation of 104.59 Tons, equivalent to an earned carbon credit of $2090.31 from the hybrid system.

The use of porous burner in combustion appliances finds widespread attention due to its inherent nature of low emission and high efficiency. This paper presents a finding on the effects of the porous medium (PM) configuration and operating parameters on the performance of a kerosene pressure stove equipped with Silicon Carbide (SiC) and Alumina (Al2O3) operating in the submerged combustion mode. The study covers three different diameter burners: 60 mm, 70 mm and 80 mm, and their thermal performances are assessed through thermal efficiency, emissions and radial temperatures at different air and fuel flow rates. The best performance is observed in the case of 70 mm diameter burner with a minimum of 44 ppm CO (carbon monoxide) and NOx (oxides of nitrogen) ∼1.5 ppm. An air flow rate range of 120–130 lpm is found optimum.

Porous media combustion (PMC) is relatively a new concept, and due to its inherent characteristics of high efficiency and low emissions, it has found wide applications in many practical systems like internal combustion engine (IC engine), water heater, LPG (Liquefied Petroleum Gas) stoves, etc. In this study, the concept of PMC has been employed in a kerosene pressure stove, and the usefulness of the media consisting of alumina (Al2O3) and silicon carbide (SiC) in terms of efficiency and emissions is investigated. Further, the conditions for optimum efficiency and emission are brought out through a systematic analysis with different burner geometry and exergy calculation. The major highlight of this study is that the highest efficiency of the stove with porous media is found to be ∼10% higher than the average thermal efficiencies of the stoves available in the Indian market.

The present study's main objective is to develop a best-performing gas-solid vortex reactor (GSVR) dryer observing at the effect of spiral versus conical chimney outlet in capacity enhancement. Three-dimensional computational fluid dynamics study of the GSVR model with spiral and the conical chimney has been conducted using a commercial software ANSYS FLUENT 14.5, applying an Eulerian-Eulerian approach for gas-solid. The fluidization capacity of the SL-GSVR drying chamber with a spiral chimney is enhanced by increasing chamber-length. In contrast, in the case of SL-GSVR with a conical chimney outlet, the fluidization capacity is increased by improving the diameter of the reactor, considering various operating parameters, such as air velocity, pressure, bed-thickness, temperature, and heat transfer coefficient. For the same input parameters, the solid loading capacity of the SL-GSVR with a spiral drying chamber is found to be 27% higher than the SL-GSVR with a conical-chimney outlet. Also, the capacity enhancement seems simpler and easy by using a spiral-chimney outlet due to its symmetric nature of construction.

Decentralized energy generation at community level is the need of the hour for meeting the increasing load demands. A pilot-scale 1 kW photovoltaic (PV) system was installed at Auniati Satra near IIT Guwahati for studying the effects of its operating parameters at different loading conditions corresponding to the environmental conditions prevalent in Guwahati, Assam (India). The PV system was subjected to constant electrical load both in standalone mode and grid-connected mode during the daytime at eight different loading conditions viz. 20%, 30%, 40%, 45%, 50%, 60%, 70% and 80% and half-hourly data of different parameters like solar insolation, PV energy, PV charge, temperature, and battery capacity were analysed. Optimum loading condition in standalone mode was found to be at 45% − 50% load under normal solar insolation without much burden on the battery bank and can be extended to a maximum load of 70% during the daytime at high solar insolation. In grid-connected mode, load application upto 45% was economically beneficial as less power was utilized from local grid. Though it can be subjected to almost its full rated capacity with input from the ac supply.

In the present study, a three-dimensional computational fluid dynamics (CFD) simulation is carried out to investigate the gas-solid fluidization behavior and heat transfer characteristics in a rotating solid-bed with static geometry (RFB-SG) without slits. With a static geometry adit as the research objective, this paper makes use of the Eulerian–Eulerian approach to carry out numerical simulations in ANSYS FLUENT 14.5 software. The prediction of particle fluidization capacity and its behavior in the developed reactor has been analyzed, using appropriate parameters and simulation analysis. The results illustrated that the main factors, such as air inlet velocity, inlet pressure, temperature, and heat transfer coefficient, affected the reactor capacity. It is observed that for a solid inventory of 300 g, a well-stabled solid-bed has been obtained at an air velocity of 22 m s−1. On enhancing the inlet air velocity up to 33 m s-1, not only the fluidization capacity of the reactor is increased by 500 g but also the drying efficiency is found to be increased. On validating numerical results with experimental findings, the maximum error of temperature is found to be 6.98%.

The ever-increasing population of India accompanied by the recent concerns regarding fossil fuel depletion and environmental pollution has made it indispensable to develop alternate mode of transportation. Electric vehicle (EV) market in India is expanding. For acceptance of EVs among the masses, development of charging infrastructure is of paramount importance. This paper formulates and solves the charging infrastructure-planning problem for Guwahati, India, that will develop as a smart city soon. The allocation of charging station problem was framed in a multi-objective framework considering the economic factors, power grid characteristics, such as voltage stability, reliability, power loss, as well as EV user's convenience, and random road traffic. The placement problem was solved by using a Pareto dominance-based hybrid algorithm amalgamating chicken swarm optimization (CSO) and the teaching learning-based optimization (TLBO) algorithm. Finally, the Pareto optimal solutions were compared by fuzzy decision-making.

The increasing global concerns about reduction of carbon footprint, climate change, and energy crisis have led researchers to delve into an alternative of fossil fuel reliant transportation. As a result of which 21st century has witnessed a renaissance of electric vehicle (EV) as a means of sustainable, environmental-friendly alternative. The electrification of the transportation sector has initiated the development of charging infrastructure for hassle-free operation of EVs. The development of charging infrastructure is accompanied by increase in load of the distribution network. The relatively high charging load of EVs is indeed a challenge for the power system engineers globally. It is essential to investigate the impact of EV charging load on distribution network for apposite placement of charging stations in the distribution network. Thus, this chapter aims to investigate the impact of EV charging station load on different operational parameters of the distribution network. Furthermore, an attempt will be made to optimally place the EV charging stations in the distribution network taking into account different operating parameters of the network. The entire analysis will be carried out on IEEE 69-bus test system which is a standard radial distribution network.

Electricity generation through coal–thermal route is one of the highest contributors to environment pollution through greenhouse gas emission, which has given rise to issue of climate change risk. Among different alternatives of renewable energy, an important source is biomass-based energy. Utilization of biomass for energy production in coal-fired power plants is essentially in terms of partial substitution of coal feed with biomass. Major challenge in this route is fluctuating supply and varying compositions of biomass. It can be overcome by adopting co-gasification technology (using mixed feed of biomass and low-grade coal) for power generation. In this chapter, we have presented a critical review and analysis of the literature in the area of co-gasification of biomass and coal. Analysis in this paper touches upon several facets of co-gasification process such as effect of biomass/coal ratio, the composition (proximate/ultimate analyses of biomass/coal), gasification media, temperature and heating rates on the gasification kinetics, producer gas composition, and yield. The synergistic effects between gasification of coal and biomass have been reviewed. The alkali/alkaline earth metal content in the ash of biomass catalyzes the kinetics of the gasification of coal char. However, if coal has high silica content, adverse reaction between silica and potassium oxides can deactivate the catalytic effect. Actual chemical mechanisms related to this synergy have also been described and discussed. Finally, a brief review of the literature on gasification of coal/biomass blends in bubbling/circulating fluidized bed gasifiers has also been presented.

Before the mining of fossil fuels, biomass was the main source of energy for heating and cooking including hot fuel gas production. With rapid industrialization and use of fossil fuels with high calorific values, use of biomass decreased rapidly. However, in the present context of both climate change and energy security, importance of biomass is regaining as a sustainable energy solution. Life cycle of CO2 emission during the secondary energy production from biomass is lesser than that of the fossil fuels. It is even negative, say for bioenergy with carbon capture. Biomass with good calorific value is abundantly available in countries with rapidly increasing energy demands like India, China, Brazil. Utilization of biomass may increase energy access in rural areas and long-term energy security in India. However, proper selection of biomass, their logistics, and conversion pathways will play an important role. Sustainability of the biomass-based energy system should be assessed for its future feasibility. In this chapter, role of biomass for sustainable energy is assessed specifically for India. Present challenges of energy generation are reviewed. Availability of different types of biomass and logistics are explored. Then, various possible conversion technologies for the conversion of biomass for fuels, electricity are discussed. Possible energy system design for biomass inputs including direct firing, co-firing, gasification and polygeneration are discussed in this chapter. Sustainability assessment of these energy systems is discussed in this chapter. Finally, challenges and prospects related to biomass-based distributed energy solution are presented.

Rural electrification is an important measure for prompt and sustainable growth of the developing nations. Providing electricity access to extreme remote localities is a challenging task for distribution utilities. Microgrids with renewable energy based distributed generation using locally available energy resources may be one of the effective solutions. This paper presents a study on recent developments in microgrid with the Hybrid Renewable Energy System (HRES). A brief discussion and analysis of modeling, control, reliability and energy management of microgrid with HRES is presented. A brief survey and examination of the potential of power generation with HRES in South-Asian nations is also undertaken in this research.

Gasification is the thermochemical conversion of solid fuel into the gas which contains mainly hydrogen, carbon monoxide, carbon dioxide, methane and nitrogen. In gasification, fluidized bed technology is widely used due to its various advantageous features which include high heat transfer, uniform and controllable temperature and favorable gas–solid contacting. Modeling and simulation of fluidized bed gasification is useful for optimizing the gasifier design and operation with minimal temporal and financial cost. The present work investigates the different modeling approaches applied to the fluidized bed gasification systems. These models are broadly classified as the equilibrium model and the rate based or kinetic model. On the other hand, depending on the description of the hydrodynamic of the bed, fluidized bed models may also be classified as the two-phase flow model, the Euler–Euler model and the Euler–Lagrange model. Mathematical formulation of each of the model mentioned above and their merits and demerits are discussed. Detail reviews of different model used by different researchers with major results obtained by them are presented while the special focus is given on Euler–Euler and Euler–Lagrange CFD models.

Combustion of fossil fuels is one of the major sources of greenhouse gas CO2, it is therefore necessary to develop technologies that will allow us to utilize the fossil fuels while reducing the emissions of greenhouse gases. Pressure swing adsorption (PSA) is a potential technique for removing CO2from high-pressure fuel gas streams. Zeolites are suitable candidate sorbents for use in the PSA process. Studies of the gas adsorption of CO2onto zeolite 13X and zeolite 4A were conducted at a temperature of 25 °C, 35 °C, 45 °C and 60 °C up to a pressure of 1 bar. The data fitting is accomplished with the Toth and Sips adsorption models which are generally used for micro-porous adsorbents such as zeolites. Moreover, regeneration studies have been conducted in order to verify the possibility of adsorbents reutilization, to determine its CO2adsorption capacity within consecutive cycles of adsorption–desorption. Zeolite with higher surface area showed higher CO2adsorption capacity. There is no full reversibility for the two zeolites.

This paper presents the study of carbonization systems for the production of Bamboo Charcoal which is formed on dry distillation of raw bamboo. The paper mentions the drawbacks of the conventional practices of production of Bamboo Charcoal. Design of a new charcoal production unit is aimed at eliminating the identified drawbacks in the present methodology of production making the process of production faster and more efficient by minimizing heat loss during the production process. Designing is attempted with strong consideration for manufacture, operational cost and ease of operation of the furnace as the process finds application amongst rural people with little or no technical knowhow, making simplicity of design absolutely critical for implementation of the developed technology. Results of testing and experimentation presented in this paper describe the working prototype confirming qualitative and quantitative improvements in the bamboo charcoal being produced as compared to the conventional method of production.

Low-grade coal and biomass waste such as bamboo dust, sawdust, rice husk, etc. are abundantly available in India. Utilization of such resources to generate electricity is a challenging task with conventional methods. Atmospheric circulating fluidized bed (ACFB) is considered to be one of the potential devices to utilize coal or biomass or both for power production through gasification or combustion routes. In this paper, the effect of various operating parameters such as bed inventory, particle size, superficial velocity, blends of coal with sawdust (percentage by weight) and operating pressure on bed hydrodynamics, i.e., bed voidage, suspension density, and solid circulation rate were studied experimentally in a pressurized circulating fluidized bed (PCFB). The bed voidage decreases with an increase in operating pressure and increases with an increase in particle size. Maximum of 8.2% decrement in bed voidage is observed as operating pressure varies from atmospheric to 4 bar. Further, the suspension density is found to increase with an increase in inventory weight. Peak increment of 28.3% in suspension density is perceived with an increase in inventory weights at a pressure of 4 bar.

The desulfurization process to a two-dimensional (2-D) and three-dimensional (3-D) Eulerian–Eulerian computational fluid dynamic (CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SOx emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilization, heterogeneous, and homogeneous chemical reactions as well as calcination and desulfurization reactions are incorporated. A calcination-only model and a calcination plus desulfurization model are simulated in 2-D and 3-D and the concentrations of SO2 leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidized bed on the desulfurization is also considered. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1952–1963, 2013

SUMMARY Biomass gasification has been a viable alternative for decentralized electricity generation in developing countries. The efficiency of the biomass gasification process for operation of the engine-generator set is mapped in terms of quality and quantity of the producer gas. In this study, we have attempted to devise generalized correlations for four principal parameters that form the benchmark for the performance of the gasifier. These parameters are lower heating value and net yield (per unit biomass) of producer gas, and volume fractions of CO and CO2 in the gas resulting from biomass gasification process. The correlations have been constituted using simulations of gasification of three common biomass feedstocks (viz. rice husk, saw dust and corn cobs) using semi-equilibrium non-stoichiometric thermodynamic model. The independent variables used in the simulations are air ratio, carbon conversion, gasification temperature and three elemental ratios in the gasification mixture, viz. H/C, O/H and O/C. As many as eight expressions of linear and non-linear type have been evaluated to best fit the simulations data for each performance parameter. On the basis of statistical indicators, the compatibility of the correlations for best fit of the data has been assessed. Finally, the predictions of the correlation have been tested against experimental data on gasification of different biomass. The best correlation for each performance parameter was chosen on the basis of least average absolute error and highest (absolute) regression coefficient. It was found that the set of best correlations could predict the values of performance parameters within engineering accuracy of ± 10–20%. The correlations proposed in this work are independent of the type of biomass gasifier. These correlations can form a useful tool for design and optimization of fixed or fluidized bed gasifier for any biomass feedstock. Copyright © 2011 John Wiley & Sons, Ltd.

This article attempts to highlight the technical and economical issues related to decentralized power generation in India using biomass gasification. Biomass-based energy has several distinct advantages such as wide availability and uniform distribution that puts it ahead among the renewable energy options for India. The estimated potential of power generation through renewable sources in India is 85 GW with biomass power contributing approximately 20 GW. Especially, in the remote areas and hilly terrains of India, biomass gasification-based power generation offers a highly viable solution for meeting energy demands of small villages and hamlets, which would not only make them independent but will also reduce burden on state electricity boards. This paper reviews various technical options for biomass gasification-based low-, medium- and large-scale power generation. We essentially discuss the merits and demerits (operational and other problems) of different systems. Further, we also deal with economics of these systems and discuss principal factors influencing the viability of the biomass-based power generation. Finally, we review some case studies of biomass-based power generation for meeting energy needs, both thermal and electrical.

Fluoride contaminated drinking water is a severe problem in many parts of the world because of fluoride-related health hazards, which are considered to be a major environmental problem today. The present work is aimed at utilizing solar energy for removal of fluoride from drinking water by using a “solar still”. Also tests have been conducted with the “solar still” to find out hourly output rate and “still efficiencies” with various test matrixes. It is observed that the distillate from “solar still” showed a fluoride reduction of 92–96%. Further, the efficiency of “solar still” got increased by 11% when capacity of water in the solar basin was raised from 10 to 20 L. Upon suitable modification of the solar basin with appropriate base liner and insulation, this efficiency of the “solar still” is found to be further increased by 6% with a 20 L basin capacity.

Gasification is the thermochemical conversion of solid fuel into the gas which contains mainly hydrogen, carbon monoxide, carbon dioxide, methane and nitrogen. In gasification, fluidized bed technology is widely used due to its various advantageous features which include high heat transfer, uniform and controllable temperature and favorable gas–solid contacting. Modeling and simulation of fluidized bed gasification is useful for optimizing the gasifier design and operation with minimal temporal and financial cost. The present work investigates the different modeling approaches applied to the fluidized bed gasification systems. These models are broadly classified as the equilibrium model and the rate based or kinetic model. On the other hand, depending on the description of the hydrodynamic of the bed, fluidized bed models may also be classified as the two-phase flow model, the Euler–Euler model and the Euler–Lagrange model. Mathematical formulation of each of the model mentioned above and their merits and demerits are discussed. Detail reviews of different model used by different researchers with major results obtained by them are presented while the special focus is given on Euler–Euler and Euler–Lagrange CFD models.

Application of the discrete transfer method is extended to solve transient radiative transport problems with participating medium. A one-dimensional gray planar absorbing and anisotropically scattering medium is considered. Both boundaries of the medium are black. The incident boundary of the medium is subjected to pulse-laser irradiation, while the other boundary is cold. For radiative parameters such as optical thickness, scattering albedo, anisotropy factor, transmittance, and reflectance at the boundaries are found. Results obtained from the present work are compared with those available in the literature. The discrete transfer method has been found to give an excellent agreement.

In the present paper, CFD simulations using ANSYS-Fluent 14.5 were accomplished to study the effect of bed or sand inventory and effect of scale-up of riser on heat transfer characteristics like temperature and heat transfer coefficient. To accomplish the scale-up study, 3D CFD simulations were performed on the Circulating Fluidized Bed (CFB) risers of cross section 0.15 × 0.15 m, 0.30 × 0.30 m, and each of height 2.85 m. CFD simulations to predict heat transfer characteristics were accomplished under same operating conditions on heated portion (heater) of both risers. The walls of heater were maintained at the constant heat flux q″ = 1,000 (W/m2). Modeling and meshing were done using ProE and ANSYS ICEM CFD software, respectively. RNG k-e model was used for turbulence modeling. Eulerian model with Gidaspow phase interaction scheme was used to simulate the two phase flow (air + sand mixture flow). Computational (CFD simulation) data was compared with experimental data for the validation purpose. After validation, further simulations were conducted on riser of cross section 0.30 × 0.30 m. Based on scale-up study, empirical correlation has been developed to predict the heat transfer coefficient.

In the present study, a new method is proposed for temperature controlling by combustion staging. Two combustion stages can be used with two stages of fuel feeding. A high stoichiometric ratio (SR) gimel > 1 is used at the first stage to mitigate adiabatic flame temperature (AFT) in case of high O2% in the oxidant. For validation, a series of experiments are conducted using mini-CFB (circulating fluidized bed), and an oxidant of 100% O-2 concentration is used with three SR ratios, i.e. gimel = 1.25, 2.0 and 3.0. The resulting average temperatures along the riser for biomass are 1031 degrees C, 950 degrees C and 798 degrees C; and for coal 1129 degrees C, 1051 degrees C and 961 degrees C respectively. The controlling of AFT with pure oxy-fuel combustion eliminates the recycled flue gas in oxy-fuel CFB combustion and flue gas recirculation section; this simplifies design, fabrication and installing-operating costs of the power plants. Familiarizing this concept can accelerate adapting oxy-fuel combustion in CFB power plants for carbon capturing and sequestration. This study can help commercialize the third generation of oxy-fuel CFB combustion with zero RFG. Finally, the concept of controlling AFT by SR is validated experimentally.

In recent years, biomass gasification has emerged as a viable option for decentralized power generation, especially in developing countries like India. In this chapter, we have given an overview of the energy scenario in India with statistics of electricity generation through various sources along with data on coal deposits and agro-residues, which are potential feedstock for electricity production through thermal route. Moreover, using the non-stoichiometric equilibrium and semi-equilibrium models, we have assessed the outcome of gasification process for different combinations of operating conditions and various biomass as feedstock, either single biomass or their mixtures. Four key parameters have been used for optimization, viz. biomass type, air or equivalence ratio, temperature of gasification, and gasification medium. The gasification medium has been taken to be either pure air or air–steam mixture. It is revealed that the biomass mixtures also form potential feedstock for gasifiers, and the performance of gasifier is very similar to that with single biomass as feedstock. On the basis of simulations results, we have also attempted to optimize the operating conditions for biomass gasifier operation. The optimum sets of operating conditions for gasifier for application of decentralized power generation are: Air Ratio = 0.3–0.4, Temperature = 700–800°C with gasification medium being air.

Introduction C OLLAPSED dimensionmethod (CDM) is one of the ray tracing methods used for the solution of radiative transfer problems. Development of this method is partly based on the works of Shih and Chen1 and Shih and Ren2 on the discretized intensity method. Some light on the method was thrown by Blank. Subsequent developmentof the method was made by Blank andMishra.4 Detailed description of this method is available in Ref. 5. In CDM, three-dimensionalradiative information is mapped into a two-dimensionalsolutionplane in terms of effective intensity (EI) andoptical thicknesscoefŽ cient (OTC). Thus, unlikeothermethods, analysis and computations in this method are performed in a twodimensional solution plane instead of three-dimensionalspace. CDMhas beenused for the solutionof radiativetransferproblems with highaccuracy.4;5 Thismethodhasbeenfoundtowork for awide rangeof optical thickness (very low to high optical thickness). Furthermore, CDM has also been found to work well for the conjugate mode heat transfer problems. In CDM, for determinationof heat  ux and temperature information, at each point of interest EIs have to be integrated over planar angle in the solutionplane.Theseangularintegrationsareperformed by dividing the planar angle into intervals of equal sizes. In each subinterval, EI is assumed isotropic. Hence, for higher accuracy, CDM requiresmore EIs and, thus, higher computational time. In the presentwork,with the objectiveofmakingCDMmore economical, the method is modiŽ ed. In the modiŽ ed CDM (MCDM), angular integrations of the EIs are performed differently. The discretizationand integrationsperformed in thismethod originatefrom the concept of the discrete ordinate method (DOM). Here, the planar angle is divided into a Ž nite number of subintervals according to the number of Gaussian quadraturepoints considered.Hence, in MCDM, angular subintervals are unequal and instead of considering average values of interval, the weighted mean corresponding to the Gauss points is considered. With this, the method becomes more realistic, and it derives computational efŽ ciency with a more realistic representationof the radiative transfer process. In the present work, improvements in MCDM over CDM are tested by solving radiative transfer problems in oneand twodimensional Cartesian enclosures with gray and homogeneous, absorbing, emitting, and anisotropically scattering medium. Both radiative and nonradiative equilibrium situations are considered. MCDM and CDM results are compared with results from the exact method and DOM.

Combustion of fossil fuels is one of the major sources of greenhouse gas (GHG) CO2, it is therefore necessary to develop technologies that will allow us to utilize the fossil fuels while reducing the emissions of GHG. Removal of CO2 from flue gasses has become an effective way to mitigate the GHG and adsorption is considered to be one of the methods. Adsorption of CO2 on zeolite 13X, zeolite 4A and activated carbon (AC) have been investigated at a temperature ranging from 25 to 60 °C and pressure up to 1 bar. The experimental data were fitted with isotherm models like Langmuir and Freunlich isotherm model. The Langmuir model fit well with the two zeolites and Freunlich model fit well with AC. The thermodynamics parameters were calculated and found to be exothermic in natures for all three adsorbents. Moreover, regeneration studies have been conducted in order to verify the possibility of activated carbon reutilization, to determine its CO2 adsorption capacity within consecutive cycles of adsorption–desorption. Temperature swing adsorption was employed as the regeneration method through heating up to a temperature of approximately 100 °C. There is no full reversibility for zeolites while AC can achieve complete regenerations.

The Indian Government's National Biogas and Manure Management Programme (NBMMP) seeks to deliver renewable energy services to households across the country by facilitating the deployment of family-sized ( 3 ) anaerobic (biogas) digesters. NBMMP policy is implemented at three levels, from government and state nodal agency, via private contractors to households, creating multiple institutional arrangements. We analysed the scheme in Assam, north-east India, focusing on how policy was implemented across two districts and interviewing stakeholders in rural households, state and non-state institutions. The top-down, supply-side approach to policy enables government to set targets and require individual states to deploy the scheme, which benefits households who can afford to participate. NBMMP delivered improved energy service outcomes to a majority of households, although the level of knowledge and understanding of the technology amongst users was limited. Training and education of householders, and particularly women, is needed in relation to the maintenance of digesters, feedstock suitability and the environmental and potential livelihood benefits of digestate. A revised bottom-up approach to policy, which highlights the contextual and demand-side issues around adopting the technology, may deliver monetary benefits from market competition and enable development of community-focused microfinance schemes to improve the affordability of biogas systems.