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The demand for energy has been increasing all over the world, necessitating the introduction of novel devices to work with lower energy consumption. Modern technologies used for paddy drying are on...

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).

Biogas is made up of methane, carbon dioxide, and traces of numerous trace of elements. It is created through the anaerobic digestion of organic materials, such as cattle manure, and is dependent on a number of parameters impacting the population and activity of the bacteria that make biogas. Temperature is one of the many variables that affect biogas production from cattle manure. The effect of temperature on biogas production from cattle dung was investigated at temperatures ranging from 35°C to 55°C, with each step of 5°C. The effect of temperature on the rate of biogas production from cattle dung is evaluated using a mathematical model developed in this study. The temperature impact is added to the modified Gompertz model to create the new mathematical model. The new model was found to be capable of predicting biogas production from cattle dung at temperatures ranging from 35°C to 55°C. The results of the new model are found to be highly correlated with the experimental data of the current study.

Tea has become an important crop in a many regions of the world. India is one of the best quality tea producers in the world. Despite of being an important cash crop, much research has not been made on tea, due to which modern drying technologies have not been employed in this regard. This work reflects the drying characteristics for tea in a bubbling conical bed dryer. Fresh Assam tea leaves have been processed into crush, tear, and curl (CTC) tea initially, followed by fermentation and drying in a conical bubbling fluidized bed dryer. The effect of various parameters, such as drying air temperature, superficial air velocity, inventory, and cone angle, on moisture removal rate from CTC tea in the conical bed dryer has been experimentally investigated and analyzed in this present work. Drying temperature and superficial air velocity are found to be the major parameter that affects the moisture removal rate from tea. The moisture removal rate from tea varies proportionally with the increase in drying temperature, but the quality deteriorates after a certain limit of temperature. Different cone angles of 0°, 5°, and 10° for the conical bubbling fluidized bed dryer are also inquired into for a static inventory bed height of 15 cm. It is found that moisture removal rate is highest for the case 10° cone angle of the dryer.

Pressurized Circulating Fluidized Bed (PCFB) has earned appreciation in using low-grade coal for gasification and combustion applications because of its built-in capacity to capture sulphur and NOx. It becomes more attractive due to its compactness and elevated heat release rate. Whether the fluidized bed is used to separate or react, the key objective is to operate the bed at a flow rate that optimizes the application. Accurate models would help a great deal but modelling continues to challenge engineers and researchers even at a qualitative level. In this present investigation, numerical simulation is carried out in two conical risers and one columnar riser by considering coal as a bed inventory. The simulation is performed at a superficial velocity of 4 m/s for an inventory of 1 kg. The model k–e is used as a turbulence model. The simulation is performed to investigate the optimum parameters for the efficient use of the pressurized circulating fluidized bed. From the simulation, the variation of bed voidage, suspension density and pressure over the riser height are calculated at the operating pressure of 1, 2, 5 and 10 bar and results have been compared among the three risers. It is observed that pressure drop decreases up to a certain height and then increases with the height of the riser. Suspension density is also found to be decreasing with height. The pressure drop in the conical bed is found to be lower than that of columnar bed.

Biogas is mainly composed of methane (CH4) and carbon dioxide (CO2) with trace amounts of hydrogen sulfide (H2S), of which CO2 and H2S are impurities. Scrubbing of these two impurities are crucial for purification and upgradation of biogas, which would simultaneously also increase the calorific value of the treated biogas and address the issue of corrosion. Several studies have used expensive and environmentally harmful chemicals for the purification of biogas. This study reports a simple biogas purification system that utilizes biomass biochar and biochar–clay composites to remove CO2 and H2S from biogas by the process of adsorption. The biomass biochar could enrich the methane content of raw biogas from 59.7 to 84.6%, which shows the potentiality and applicability of biomass biochar for the removal of CO2 and H2S from biogas. This simultaneously enhanced the calorific value of the biogas and retarded the corrosiveness due to H2S. The study also indicated that CO2 adsorption by biomass biochar and biochar–clay composite is transient and has to be reloaded after saturation. Biochar and clay have the added advantage of being environment friendly and require no treatment for disposal. Observed results indicated that similar degree of enrichment, compared to commonly used chemical, could be achieved by application of biomass biochar and biochar–clay at a much lesser cost.

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.

Anaerobic digestion of lignocellulosic biomass has gained attention in recent years due to its increase availability and productivity. In this study, anaerobic mono- and co-digestion of three lignocellulosic biomass, viz. duckweed, switchgrass, and rice straw, were performed in 1 litre laboratory-scale batch reactors. The initial biochemical methane potential (BMP) test was performed at three different total solids concentrations (10%, 15%, 20%) and cattle dung: feedstock ratios (1:1, 1:1.5, 1:2) under mesophilic conditions (28–32 °C) for 36 days. Co-digestion of feedstocks at 1:1 ratio yielded better results than other cattle dung: feedstock ratios. Optimized physical parameters were further implemented for a scale-up co-digestion study of biogas potential from 4 m3 community-size biogas digesters. The investigation was performed for 60 days maintaining a hydraulic retention time (HRT) of 40 days, and a comparative analysis with mono digestion of cattle dung was also analyzed. Average daily biogas production for digester containing rice straw and cattle dung was 0.36 m3/kg-VS, whereas it was 0.34 m3/kg-VS and 0.32 m3/kg-VS for switchgrass and duckweed, respectively. An overall comparative analysis of the biogas production and its composition for both BMP tests and continuous processes are discussed in this work.

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.

Recent strategies on fuel-development to reduce oil dependency to mitigate greenhouse gas emissions and to utilize domestic resources have generated interest in the search for alternative sources of fuel supplies. In this context, the industrial waste may be regarded as potential alternatives for biogas production. This study entails a detailed characterization of tea waste and food waste to evaluate their potential as an alternate feedstock to cattle dung for biogas production. The samples were characterized for volatile matter, moisture content, ash content and carbon hydrogen nitrogen (CHN). Property analysis of the biomass was also done by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The volatile matter content in tea and food waste was found to be 64.17% and 36.05% respectively, which is quite encouraging. The carbon-to-nitrogen (C:N) ratio, chemical oxygen demand and total solids of the sample also attributed its suitability for biogas production. The thermal behavior and heating values interpreted higher lignin content in tea waste. The lab scale study was conducted with combination of food waste/cattle dung and tea waste/cattle dung that showed higher biogas production in comparison to cattle dung alone implying their potential as biogas feedstock. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1247–1253, 2016

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 work, thermodynamic analysis of a natural convection dryer with and without sensible heat storage material (pebbles) has been studied. The purpose of this study is to enhance the performance of the dryer by using pebbles as a sensible heat storage medium. Energy and exergy analysis has been done to investigate the magnitude of losses whether the pebbles will be appropriate to use as a sensible heat storage material. The experiments were performed under different experimental conditions, without pebbles (case-I), pebbles filled up to the furnace height (case-II), pebbles filled up to the paraffin wax tray (case-III). In the case-IV, pebbles filled up to the paraffin wax tray but hot air is not allowed to flow from the rectangular chamber to the drying chamber. From the 1st three cases (I to III), it was observed that the energy losses and exergy destruction in the rectangular chamber are lower in the case-III. From the result, it can be seen that the use of sensible heat storage material and restricting the hot air in the rectangular chamber is promising in contributing to the performance of the dryer.

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.

Conversion of woody biomass, animal waste such as cattle dung, chicken litters, pig manure, municipal solid, and agricultural wastes to methane gas under oxygen-free environment and favorable temperature range is called anaerobic digestion. But achieving the required temperature range under normal condition is difficult which necessitates the development of a heating system for better digestion process. The endeavor of the present investigation was developing 1.8 m2 solar collectors intended to heat biogas digester and investigating its performance. The solar collector was tested experimentally and numerically for heating water before implementing in actual model. A three-dimensional computational fluid dynamics model was developed by taking a single straight tube attached with an absorber plate at the bottom to predict outlet water and absorber plate temperature. The developed model predicted the outlet water temperature and absorber plate temperature with a reasonable accuracy. Moreover, 53 °C of outlet water temperature and 44% daily average efficiency were achieved at a flow rate of 0.021 kg/s. As the obtained temperature was found to be good enough for anaerobic digestion, the developed solar collector could be regarded as an alternate option.

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.

Biomass gasifiers with capacities exceeding 1 MW have large biomass consumption, and mixture of biomasses need to be used as feedstock in these gasifiers. In this chapter, we have presented a review of our studies in gasification of biomass blends using approaches of non-stoichiometric equilibrium, semi-equilibrium, and kinetic models. Initially, gasification of biomass mixtures has been assessed using thermodynamic equilibrium and semi-equilibrium (with limited carbon conversion) model employing Gibbs energy minimization. Influence of operating parameters such as equivalence ratio, temperature of gasification, and composition of the biomass mixture has been evaluated using two criteria, viz net yield and LHV of the producer gas. Interestingly, optimum operating conditions for all biomass mixtures have been established as equivalence ratio ~0.3 and gasification temperature ~800 °C. The kinetic model analysis of gasification of biomass based on a circulating fluidized bed gasifier. A series of chemical reactions was considered for obtaining complete mass balance. Although the profiles of molar composition, net yield and LHV of the producer gas predicted by kinetic model matched with equilibrium models qualitatively, significant quantitative difference was evident. The processes of char gasification and tar oxidation have slow kinetics that adversely affects the carbon conversion in the riser of the circulating fluidized bed gasifier.

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.

In this study the effects of temperature on anaerobic co-digestion of saw dust with cattle dung is investigated. It also simulates the biogas production from saw dust with cattle dung at various temperatures. Results showed that high temperature could improve the anaerobic digestion and hence increase the biogas production rates. The operating temperatures used in this study were 35°C, 45°C, and 55°C. Modelling study revealed that exponential plot simulated better in both ascending and descending limb at all the three temperatures. However in ascending limb exponential plot was better for biogas production at 55°C and 35°C whereas in descending limb exponential plot was better for biogas production at 45°C. Gaussian plot had higher correlation at 35°C compared to other temperatures. Logistic growth model and modified Gompertz plot showed better correlation of cumulative biogas production than exponential rise to maximum plot for all the temperatures.

The present study involves the preparation and characterization of the biomass briquettes made from saw dust and rice husk. Five samples with different compositions were prepared using the old news papers as the binder for both the biomass. Ultimate analysis, proximate analysis, heating value and handling characteristic of all the samples were determined. It was observed that the compositions of the biomass sawdust (BMS)-15 and biomass rice husk (BMR)-15 are suitable for the downdraft gasifier.

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.

Biogas is a mixture of methane, carbon dioxide and traces of numerous trace of elements. It is produced by anaerobic digestion of organic matters including cattle dung which depend upon various factors affecting the population and activity of microorganisms producing biogas. Among the various factors temperature is one of them which play a significant role in biogas production from cattle dung. Biogas production from cattle dung was studied at temperatures 35°C to 55°C at a step of 5°C to study the effect of temperature on biogas production from cattle dung. In this work a mathematical model is developed for evaluating the effect of temperature on the rate of biogas production from cattle dung. The new mathematical model is derived by adding the effect of temperature on the modified Gompertz model. The new model is found to be suitable for predicting the biogas production from cattle dung in the temperature range 35°C to 55°C. The results from the new model are found to be highly correlated to the experimental data of present study.

In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a pressurized circulating fluidized bed (PCFB) has been studied. Experiments are conducted with two different bed inventories, viz. 500 and 750 g. Aeration superficial velocities, U sup = 0.65, 1.94, and 3.23 m/s respectively are used to observe the change of bed hydrodynamics of the PCFB. Operating velocities of 2.72, 3.4 and 4.08 m/s and pressures of 100, 200, and 250 kPa are maintained for each inventory and aeration rate. It has been observed that the suspension density increases along the riser height with the decrease in aeration rate. The solid circulation rate increases with the increase in aeration rate as well as primary air flow rate. The present study will help in optimizing the aeration rate for smooth operation of the non-mechanical valve or the stand pipe without obstruction of inventory material.

In the villages of developing countries, use of electricity or petroleum fuel is expensive for drying the agricultural products. In the current scenario, drying through “natural convection grain dryer” is an important alternative. This paper proposes the development and evaluation of the natural convection grain dryer in drying performance of paddy. The proposed system is capable of generating an adequate and continuous flow of hot air with range of 60-70 degree centigrade. Paddy was successfully dried from 33% moisture content to 14% (w.b). Woodchips (biomass) were burnt to heat the incoming air in the dryer. Experiments were conducted with fixed amount of sensible heat storage material with varying the amount of latent heat storage material. Increase in the latent heat of storage material indicates the improvement in standard drying temperature, time and enhancement in amount of paddy dried. Re-firing further enhances the duration of optimum temperature range for quality drying.

In recent years, biomass gasification has emerged as a viable option for decentralized power generation, especially in developing countries. Another potential use of producer gas from biomass gasification is in terms of feedstock for Fischer–Tropsch (FT) synthesis – a process for manufacture of synthetic gasoline and diesel. This paper reports optimization of biomass gasification process for these two applications. Using the non–stoichometric equilibrium model (SOLGASMIX), we have assessed the outcome of gasification process for different combinations of operating conditions. Four key parameters have been used for optimization, viz. biomass type (saw dust, rice husk, bamboo dust), air or equivalence ratio (AR = 0, 0.2, 0.4, 0.6, 0.8 and 1), temperature of gasification (T = 400, 500, 600, 700, 800, 900 and 1000 °C), and gasification medium (air, air–steam 10% mole/mole mixture, air–steam 30%mole/mole mixture). Performance of the gasification process has been assessed with four measures, viz. molar content of H2 and CO in the producer gas, H2/CO molar ratio, LHV of producer gas and overall efficiency of gasifier. The optimum sets of operating conditions for gasifier for FT synthesis are: AR = 0.2–0.4, Temp = 800–1000 °C, and gasification medium as air. The optimum sets of operating conditions for decentralized power generation are: AR = 0.3–0.4, Temp = 700–800 °C with gasification medium being air. The thermodynamic model and methodology presented in this work also presents a general framework, which could be extended for optimization of biomass gasification for any other application.

Lignocellulosic biomass has great potential for biogas production, but there are various factors which affect the performance of lignocellulosic biomass. Among the various factors, temperature is one of the important factors which play a significant role in biogas production from lignocellulosic biomass. Biogas production was studied for bamboo dust, sawdust, sugarcane bagasse and rice straw, all separately mixed with cattle dung. The effect of temperature on biogas production from various lignocellulosic biomasses was studied for temperature range from 35°C to 55°C at steps of 5°C. The objective of this work is to develop a mathematical model for evaluating the effect of temperature on the rate of biogas production from various lignocellulosic biomasses. The new mathematical model is derived by modification of the modified Gompertz model. The new model is found to be suitable for lignocellulosic biomass mixed with cattle dung in the temperature range 35°C to 55°C. The resulting estimated biogas production is found to be highly correlated to the experimental data of present study.