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The present work is to study the effect of pressure on the gasification of sugarcane bagasse in a pressurized circulating fluidized bed reactor. The range of operating pressure is maintained at 1–4 bar, and thereby the composition of generated syngas is measured with the help of gas chromatography. The gasification parameters like dry gas yield, lower heating value (LHV), cold gas efficiency (CGE), and carbon conversion efficiency (CCE) have been calculated from the syngas composition. The output yields some interesting results, i.e., with the increase in pressure from 1 to 4 bar, and there is an increment of concentration value by 26% for CH4 as well as CO2. However, a decreasing trend of H2 concentration (7.62–6.75% by volume) is observed for the same pressure rise. In addition, it has been observed a little deviation in the trend for CO (16.39–16.86%), which bears an increasing trend from a pressure of 1–2 bar and a decreasing trend thereafter. Following a similar trend for CO, the LHV first increases from 4013 to 4200 kJ Nm−3 with an increase in pressure from 1 to 2 bar and thereafter decreases gradually to 4081 kJ Nm−3 at a pressure of 4 bar. Apart from these parameters, gas yield, CCE, and CGE values imparted positive effects with pressure rise, and the magnitudes increased from 0.93 to 1.27 Nm3 kg−1, 38.3–57.5 and 23.3–32.3%, respectively, with an increase in pressure from 1 to 4 bar. The exergy destruction and exergy efficiency are observed to be 140 MW and 76% at 4 bar operating pressure.

Biogas produced from anaerobic digestion of organic waste is composed of methane (CH4) and carbon dioxide (CO2) as the major constituents with trace amounts of other components like water vapor, hydrogen sulfide, ammonia, and nitrogen. Scrubbing of CO2 is essential for upgradation of biogas, which increases the calorific value of the treated gas and enhances its efficiency for power production and cooking. This study was conducted to investigate and compare the effects of different concentrations of KOH (0.1, 0.3, 0.5, 0.7, and 1.0 M) and natural base ash solutions prepared from different parts of banana plant, viz. banana pseudostem (BPS), Musa balbisiana Peel (MBP), and Musa acuminata Peel (MAP) for scrubbing of CO2 from biogas. The methane content of the untreated biogas analyzed in a gas chromatograph was found to be 56.9%. The scrubber with natural base solution from MBP could enrich the methane content in biogas from 56.9% to 86.3% followed by MAP (78.4%) and BPS (76.8%). The experiments revealed that banana peel ash base solutions have nearly equivalent potential as KOH for CO2 absorption from biogas. The highest CO2 absorption of ~ 68% was achieved with MBP with saturation time of 19 min approximately at a flow rate of 200 ml/min. The study also indicated that CO2 absorption by different natural as well as chemical base solvents is transient and has to be replenished after saturation. Natural bases have the added advantage of being easily available, cheap production method, environment friendly and require no treatment for disposal.

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.

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.

The rise in mean atmospheric temperature resulting from the emissions of greenhouse gases, especially CO 2 , has become a widespread concern in the recent years. This awareness of increase in greenhouse gas emissions has resulted in the development of new technologies which would lower emissions of CO 2 from flue gases. The purpose of this study is to investigate the performance of bubbling fluidized bed for CO 2 adsorption to mitigate CO 2 from flue gas. Adsorption of CO 2 had been carried out onto zeolite 4A, zeolite 5A, zeolite 13X and activated carbon at a pressure up to 4 bars. The effects of adsorbent mass on breakthrough time, gas velocity, adsorption isotherm, thermodynamics and heat transfer characteristics were also investigated during the continuous operation of the bubbling fluidized bed. As flow rate increased, the breakthrough curves become steeper and reached the breakthrough quickly due to the residence time of the adsorbate in the column, which was long enough for adsorption equilibrium to be reached at high flow rate. The experimental data were fitted with isotherm models like Langmuir and Freundlich isotherm model. It was found that the Langmuir model fit well with the zeolites based adsorbent and Freundlich model fit well with activated carbon. The experimental results permitted the determination of adsorption capacities of the adsorbents and showed that there is an improvement in the adsorption capacity using fluidized bed due to a better gas solid contact as compared to conventional fixed bed.

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.

We report here the characterization of five biomass samples ( Impereta cylindrica, Eragrostis airoides, Typha angustifolia L., Arundinella khasiana Nees ex Steud, and Echinochloa stagnina (Retz.) P. Beauv) based on the proximate, ultimate and compositional analysis. The biomasses were examined physico-chemically and characterized to understand their compositional and structural properties. The moisture content was found to be highest in Typha angustifolia (13.951%) and lowest in Eragrostis airoides (8.275%). Ash content was seen to be maximum in Arundinella khasiana (8.12%) and minimum in Eragrostis airoides (3.660%). Derivative Thermogravimetric (DTG) peak was observed below 120 °C indicating the loss of water molecules from the biomass. Cellulose degradation occured between 350 °C to 500 °C. The maximum carbon content was visible in Typha angustifolia (52.895%) and minimum in Eragrostis airoides (41.024%). The FTIR spectra showed a range of peaks such as 3450 cm −1 , 2860 cm −1 , 1668 cm −1 , 1175 cm −1 , 1097 cm −1 , 7872 cm −1 , 625 cm −1 , 554 cm −1 etc. The cellulose content was found maximum in Eragrostis airoides (43.17%) and minimum in Echinochloa stagnina (24.90%). The results demonstrate that the collected lignocellulosic biomass could be potential candidate for bioethanol production.

Due to the complicated structure of lignocellulosic plant cell wall, their utilization for biogas production via anaerobic digestion has not been widely adopted. Alternative to this is to use aquatic plant materials as feedstock for biogas production. In this context, duckweed, an aquatic plant may prove to be a promising new energy source for bioenergy as well efficient CO 2 sequestration. This study entails a detailed characterization of duckweed to evaluate their potential as an alternate feedstock to cattle dung for biogas production. The duckweed was characterized for volatile matter, moisture content, ash content and carbon, hydrogen, and nitrogen (CHN) content. Property analysis of duckweed was also done by Fourier transform spectroscopy and thermogravimetric analysis. The volatile matter of duckweed was found to be 84.24± 0.2% with a lignin content of 12.2%, which is very encouraging for biogas production. Co-digestion of duckweed (DW) with cattle dung (CD) in varying ratios (DW:CD = 90:10, 75:25, and 50:50 respectively) in batch type anaerobic digesters was performed at 37 °C temperature for 55 days. The cumulative biogas production for CD (100%), DW/CD (90:10), (75:25) and (50:50) was found to be 11,620, 305, 11,695, and 12,070 mL, respectively, which indicated that duckweed can be a potential lignocellulosic feedstock when co-digested with cattle dung at an optimum ratio of 1:1. Methane content of the biogas from co-digested feedstock is comparable to the biogas from cattle dung alone.

This study has been performed to enhance the performance of the solar air heater (SAH) using copper tubes to the absorber plate. Thermodynamic analysis of the SAH with and without copper tubes attached to the absorber plate has been performed. The improvement potential, sustainability index, and waste energy ratio have also been studied. From the results, it has been found that the thermal and exergy efficiency of the absorber with copper tubes is higher as compared to the absorber without copper tubes for the same climatic conditions. The energy efficiency of the SAH with and without copper tubes absorber was ranged from 14.53 to 20.36% and 12.45–17.53% with an average of 18.26% and 16.29%, respectively in the natural convection mode. The exergetic efficiency was ranged from 1.2 to 1.939% and 0.95–1.53% with an average of 1.69% and 1.41%, respectively. Energy and exergy analysis of the SAH with copper tubes attached absorber have also been performed for the forced convection mode at varying air flowrate from 0.0166 to 0.058 kg/s. The maximum value of energy and exergy efficiency of the SAH was obtained as 62.8% and 5.848%, respectively at the airflow rate of 0.05 kg/s.

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.

The intensification of interfacial mass, heat, and momentum transfer makes vortex chambers potentially interesting for the efficient drying of paddy, allowing shorter drying times and/or more compact equipment. The presence of a shell introduces particular challenges. Intraparticle diffusion limitations are strong and may reduce the advantage from intensified interfacial mass and heat transfer and the efficiency of air usage. Furthermore, high shear and normal stresses in the fast rotating particle bed may cause damage to the paddy shell, posing problems for transport and storage. With these specific aspects in mind, the use of vortex chambers for paddy drying is experimentally evaluated.

This study reports pyrolysis kinetics of biomass blends using isoconversional methods, viz. Friedman, FWO and KAS. Blends of three biomasses, viz. saw dust, bamboo dust and rice husk, were used. Extractives and volatiles in biomass and minerals in ash had marked influence on enhancement of reaction kinetics during co-pyrolysis, as indicated by reduction in activation energy and increase in decomposition intensity. Pyrolysis kinetics of saw dust and rice husk accelerated (positive synergy), while that of bamboo dust decelerated after blending (negative synergy). Predominant reaction mechanism of all biomass blends was 3-D diffusion in lower conversion range (α ≤ 0.5), while for α ≥ 0.5 pyrolysis followed random nucleation (or nucleation and growth mechanism). Higher reaction order for pyrolysis of blends of rice husk with saw dust and bamboo dust was attributed to catalytic effect of minerals in ash. Positive ΔH and ΔG was obtained for pyrolysis of all biomass blends.

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.

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.

Pressurised circulating fluidised bed (CFB) technology is a potentially promising development for clean coal technologies. The current work explores the hydrodynamics of a small-scale circulating fluidised bed at elevated operating pressures ranging from 0.10 to 0.25 MPa. The initial experiments were performed at atmospheric pressure with air and O2/CO2 environments as the fluidisation gas to simulate the hydrodynamics in a CFB. A comparison between the effects of air and O2/CO2 mixtures on the hydrodynamics was outlined in this paper for particles of 160 μm diameter. A small but distinct effect on axial voidage was observed due to the change in gas density in the dense zone of the bed at lower gas velocity, while only minimal differences were noticed at higher gas velocities. The hydrodynamic parameters such as pressure drop and axial voidage profile along the height were reported at two different bed inventories (0.5 and 0.75 kg) for three mean particle sizes of 160, 302 and 427 μm and three superficial gas velocities. It was observed that the operating pressure had a significant effect on the hydrodynamic parameters of bed pressure drop and axial bed voidage profiles. The effect of solids loading resulted in an exponential change in pressure drop profile at atmospheric pressure as well as at elevated pressure. The experimental results on hydrodynamic parameters are in reasonable agreement with published observations in the literature.

Carbon nitride thin films were deposited by RF plasma enhanced chemical vapor deposition using acetylene (C2H2) and nitrogen (N-2) mixture on Si (1 0 0) substrates. The films were deposited at 400 degrees C substrate temperature, 600 W RF power with 5 sccm C2H2 and different flow ratio of N-2 (5, 15, 30, 60) sccm. The deposition rate was characterized by surface profilometer, composition and bonding structure were characterized by EDS, Raman spectroscopy and Fourier transform infrared spectrometry (FTIR) and microstructure by Atomic Force Microscopy (AFM). The deposition rate decreased with the increase in nitrogen content. Nitrogen content of 15 atom% could be incorporated in the film at 60 sccm N-2. Deposition rate and roughness was found to decrease with the increase of nitrogen ratio. Spectroscopic studies confirmed the incorporation of nitrogen (C=N, C N) in the film and the amount of CN bonding was found to increase with increase of nitrogen content. AFM studies showed decrease of particle size with increase of nitrogen content in the precursor gas. All films were found to be X-ray amorphous. The atomic resolution picture from AFM of films confirmed the formation of C3N4 phase in the carbon nitride film.

Present work deals with the development of butanol−diesel−biodiesel blends to substitute for petrodiesel. These blends were tested for physical stability and various fuel properties conforming to ASTM standards. Subsequently engine performance and emission tests were conducted with each blend. Observations revealed the blends to be thermally and physically stable, and they showed good resemblance to the properties of diesel, with the exception of flash point only. Brake power showed marginal decrease and fuel consumption an increase in the range of 4.9%−10.7% as compared to diesel for identical performance. Exhaust gas temperature showed a drop in the range of 3.3%−9.4% due to quenching effect of butanol, whereas brake thermal efficiency showed a reduction of 6.3%−10% to that over petrodiesel. Exhaust gas emissions showed a significant decrease in CO (42%) at medium and higher loads, whereas NO showed an average increase of 2.4%−11% as compared to diesel.

Lipase was immobilized in silk fibers through glutaraldehyde cross-linking to a maximum loading of 59 U/g silk-fiber and the immobilized lipase was utilized for the hydrolysis of sunflower oil (Helianthus annuus). The hydrolytic activity of the lipase, which was poor in biphasic oil in water system, was increased significantly when the sunflower oil was emulsified in aqueous medium. The hydrolytic activities of the immobilized lipase were 48.73 +/- 1.26 U, 36.11 +/- 0.96 U, and nil when the substrate sunflower oil was used as emulsion created by a rhamnolipid biosurfactant, Triton X100, and ultrasonication, respectively. Although the efficiency of the immobilized lipase was less than 12% than the corresponding free lipase, the immobilized lipase could be reused for the biosurfactant-mediated hydrolysis of sunflower oil up to third cycle of the reaction. The yield of the fatty acids in the second, third, and fourth cycles were 49.45%, 22.91%, and 5.09%, respectively, of the yield obtained in the first cycle.

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.

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.