Search

The paper drying process has the highest level of energy consumption in the pulp and paper production process. Analysis and optimization of the energy system during the paper drying process is critical for improving the energy efficiency of the entire paper mill. In the existing model for the paper drying process, the solution requires accurate boundary conditions such as the air temperature and humidity of the pocket area and the cylinder surface temperature, which are very difficult to obtain in the papermaking process. This can result in significant deviations between the model solution and the actual production process. This paper focuses on the single-tier dryer cylinder-based paper drying process that has been widely used with high-speed papermaking machines in recent years. A mathematical model is proposed based on real-time data. The verification via industrial production demonstrates that the proposed model is reliable for the paper drying process. Based on the simulation results, two optimization operations have been proposed. The energy consumption decreases from 1.51 t steam/t paper to 1.44 t steam/t paper, 4.6% of the steam and 1.26 × 106 RMB can be saved for a medium-scale paper mill with the annual production capacity of 105 t paper.

In this paper an original and exhaustive mathematical modelling of air impingement drying systems for the production of tissue paper in the Yankee-hoods configurations is reported, which offers the possibility to optimize its energy performance. The model takes into account many detailed operative parameters of the overall drying process with the aim to execute its energy and mass balance and to evaluate its energy performances. The validity of the mathematical model has been assessed by comparison with actual data from an existing tissue paper mill. Finally, the energy performances of two different layouts of the air system have been evaluated and compared. Changing the operative parameters of the drying process, such as air jet temperature and speed and moisture content of the extraction air, it is possible to obtain the same paper production with an energy saving of about 4.5%. In average, the layout with two parallel air circuits assure an energy saving of about 1% with respect to the layout with a single air circuit.

In order to explore hydrothermal carbonization (HTC) behavior of municipal solid wastes (MSW), four typical components, waste textile, wood, paper and food, were employed to perform HTC and co-HTC process. The experiments were conducted at 240 ○C and 90 min with a 1:12 solid/liquid ratio, where blending ratios of 1:3, 1:1 and 3:1 with waste textile were investigated. As expected, the increase of fixed carbon and carbon content improved the fuel potential of hydrochar. The synergistic index (SI) analysis clearly indicated that significant synergistic effects occurred during co-HTC process. Specifically, all the SI values of hydrochar yield from co-HTC of waste textile with wood and paper were negative, while all SI values of hydrochar yield for waste textile with food were positive. Particularly, the SI values of fuel ratio for all hydrochars were positive which suggested co-HTC could promote to enhance the coalification degree of hydrochars. However, the undesirable increment of O content for hydrochars (derived from 75%waste textile-25% waste food and 50%waste textile-50% waste food) decreased the high heating value. The combustion behavior and nth-order kinetic model analysis showed that hydrochars derived from co-HTC rendered a more stable and lasting combustion profile.

Production of transportation fuels from biorefineries via biomass gasification has been suggested as a way of introducing renewable alternatives in the transportation system with an aim to reduce greenhouse gas emissions to the atmosphere. By co-locating gasification-based processes within heat demanding industries, excess heat from the gasification process can replace fossil or renewable fuels. The objective of this study was to compare the heat integration potential of four different gasification-based biorefinery concepts with a chemical pulp and paper mill. The results showed that the choice of end product which was either methanol, Fischer-Tropsch crude, synthetic natural gas or electricity, can have significant impact on the heat integration potential with a pulp and paper mill and that the heat saving measures implemented in the mill in connection to integration of a gasification process can increase the biomass resource efficiency by up to 3%-points. Heat saving measures can reduce the necessary biomass input to the biorefinery by 50% if the sizing constraint is to replace the bark boiler with excess heat from the biorefinery. A large integrated gasification process with excess steam utilisation in a condensing turbine was beneficial only if grid electricity is produced at below 30% electrical efficiency.

Paper mill sludge (PMS) can be efficiently utilized to produce fuels and chemicals. However, wastewater is usually generated during the de-ashing step of the PMS for fibrous materials recovery. Per process requirements, the wastewater stream must be treated which results in an increase in the overall process production cost. Therefore, this research aims at reusing the wastewater produced during the de-ashing step as a substitute for freshwater addition during the conversion of PMS into ethanol. The advantages of this approach include reducing the amount of wastewater produced and enhancing the overall efficiency of the process. It will contribute to the circular economy of zero waste discharges. The results showed that 30% of the process wastewater can be recycled without affecting the enzymatic hydrolysis and ethanol fermentation. Hence, the amount of wastewater that needs to be treated is reduced by 30% resulting in a cost reduction of 22.5%. The results also showed that wastewater recycling minimized the energy demands in the distillation and evaporation units by 1206 kJ/kg. The energy reduction is due to the increase of metals and total soluble solids in the broth stream after fermentation. This process configuration enhanced the process economy, saved energy and managed waste streams.

In this study, through orthogonal experiments design, the influences of ultrasonic pretreatment (frequency, power and treatment time) on co-pyrolysis and catalytic pyrolysis of municipal solid waste and paper mill sludge were explored. The differential thermogravimetry curves became steeper and the peak values were larger after pretreatment, which made the pyrolysis reaction rapidly and the volatile separated out timely. However, the change of pyrolysis characteristics was not obvious after adding MgO. The catalytic effect of MgO increased with the increase of sludge ratio. After pretreatment, the average activation energy of the samples had an overall increasing trend, but the change was small. MgO had a decreasing effect on activation energy, and with the increasing proportion of sludge the degree of reduction became significant. In addition, high ultrasonic frequency had a negative effect on reducing activation energy.

The waste biomass has immense opportunities and plenty of potentials to be an efficient source of renewable energy. Initially, native unripe coconut husk (NCH) was used as raw material for fluidized bed gasification. Then NCH was treated with paper and pulp waste water to impregnate metals present in it for getting enhanced H2 yield in fuel gas. Humidified air was used as gasifying medium, which served the purpose of introducing water vapour to take part in the gasification process. Then after, gasification medium was retrofitted with CO2, which enhanced both the higher heating value (HHV), and CO and H2 content in the fuel gas. This research serves the dual benefit of energy generation and waste minimization. HHV of unripe coconut husk was investigated and found to be 20.95 MJ/kg. H2 yield and HHV from impregnated coconut husk (ICH) were obtained as 55.55 vol % and 5.24 MJ/Nm3, respectively at HER 0.1 and gasification temperature of 850 °C in case of fluidized bed gasification. The GC-MS analysis of fuel oil obtained from ICH gasification was done to get the information about high yield of fuel gas as promise product of fluidized bed gasification.

In hot and dry climatic zones, direct evaporative cooling (DEC) system is used as an economical and efficient alternative to traditional air conditioning systems. The present paper concerns comprehensive experimental investigations and analysis of heat and mass transfer characteristics and thermal performance parameters of a bee-hive construction of corrugated-cellulose papers as a new cooling pad material. The performance parameters used to evaluate the effectiveness of the cooling pad materials are the outlet air temperature and relative humidity, pressure drop, humidifier effectiveness, rate of the evaporated water, sensible cooling capacity, specific cooling capacity (SCC), coefficient of performance (COP), specific water consumption (SWC), and Nusselt and Sherwood numbers. The cooling pad performance was investigated for a wide range of air and water temperatures and flow rates and pad thicknesses. The results show the enhancements of heat and mass transfer coefficients and the performance parameters with rising air temperature and water flow rate to humidifier. High values of the performance parameters (hc = 45 W/m2 oC and hm = 0.23 m/s, e h u m = 0.85 and COP = 170) are obtained compared to the traditional pad materials. Experimental correlations for the evaporative cooler performance parameters in terms of air and water temperatures and flow rates pad thicknesses are presented.

Power generation by variable renewable energy (VRE) is expected to expand for decarbonization, although it is difficult to ensure stabilization of the energy demand due to fluctuations in the power output from VRE. To accelerate VRE implementation, wind-powered thermal energy systems (WTth-ES), which can provide dispatchable power using wind–thermal energy converter (WECth) and thermal energy storage (TES), have been proposed. In this study, we are tackling the installation of VRE, i.e., wind energy, by TES with WECth compared with wind turbine (WTp) in paper mills to demonstrate the applicability of TES in an industrial sector. Conventional and alternative energy systems in paper mills with TES were mathematically modeled and simulated to analyze the transmittable power output and the greenhouse gas (GHG) emissions by life cycle assessment. With the installation of TES and wind energy, transmittable power could be increased with GHG emissions reduction. However, their excess installation or unbalanced combination resulted in an increase in GHG emissions and a decrease in transmittable power. By comparing the cases, the combination of paper mill, TES, and WECth could convert thermal energy efficiently and mitigate fossil fuel consumption for multiple production of paper and power from the paper mill.

This paper investigates the performance and emission analyses of a turbo-charged diesel engine fuelled with pre-mixed and post-mixed hybrid biodiesel blends at varying load condition thereby maintaining injection timing, injection pressure and speed constant at 230bTDC, 220 bar and 1500 RPM. The experimental result depicted that post-mixed biodiesel blends (POBD 20) showed higher brake specific energy consumption and exhaust gas temperature by 4.6% and 2.02% than that of diesel while brake thermal efficiency was reduced by 5.68%. However, engine overall performance of post-mixed biodiesel blends (POBD 20) was found to be comparable with diesel and other prepared test fuel blends. Similarly, comparing exhaust emissions, oxides of nitrogen and carbon dioxide were on its higher side by 2.64% and 2.43% than normal diesel fuel. On the contrary, carbon monoxide, hydrocarbon and smoke opacity for POBD 20 were found to be 36.87%, 51.5% and 23.2% lower than conventional diesel fuel. From the above study, it is finally concluded that POBD 20 blend may be used as an alternative optional fuel that can substitute present diesel fuel without much engine modification and exhaust related problems.

The co-gasification of coal and dried sewage sludge (DSS) was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor. In this study, the effect of the blending ratio of coal and DSS was investigated. Producer gases that were obtained from the tar-cracking reactor filled with active carbon contained high levels of hydrogen (maximum H2: 27.7 vol%) and low tar contents (minimum tar: 0 mg/Nm3). Upon gasification of the coal/DSS blends, the hydrogen content decreased and tar content increased with increasing DSS. Blends with coal/DSS ratios of 70/30 and 50/50 showed a synergetic effect on tar reduction, which could be attributed to the high ash content of the DSS. The gasification of the 70% DSS blend increased the condensed tar yield by only 0.1 wt%, compared to coal gasification. Lastly, a hot filter filled with Fe-impregnated active carbon was applied to completely remove tar from producer gas, which led to the production of a tar-free and hydrogen-rich gas (30 vol%). Furthermore, the Fe-impregnated active carbon reduced the H2S content to 229 ppmv. In summary, it was possible to produce a clean gas from coal and DSS blends in the UOS gasification process.

The energy consumption of an ammonia process plays an important role in the industrial energy consumption. For an ammonia synthesis process using pure oxygen gasification, the energy consumption of cryogenic air separation occupies a large proportion. The purity of the oxygen product from the air separation unit is mostly 99.6% in an ammonia process with pure oxygen gasification. The energy consumption of air separation will decrease significantly, if the purity of the oxygen product is reduced properly, which will lead to the decrease of the energy consumption of the total ammonia process, as the nitrogen element is needed for ammonia synthesis. However, the operating costs of the subsequent units will increase because of the increase of the syngas flow rate. So, there is an optimal oxygen purity that can minimize the energy consumption of the whole ammonia synthesis process. According to temperature, purification technology can be divided into cold and hot technologies. In this work, two different process models for ammonia production from coal with different purification technologies are developed to determine the process energy consumption with different inlet oxygen purity. In the process of ammonia production from coal with cold purification, the reduction of oxygen purity leads to the increase of energy consumption of oxygen compressor, methanol regeneration and refrigeration, and the decrease of nitrogen compressor power consumption. In the process with hot purification, the reduction of oxygen purity leads to the increase of energy consumption of oxygen compressor, preheating and MDEA regeneration, and the decrease of nitrogen compressor power consumption. The relationships between the eight kinds of energy consumption and oxygen purity are linear. Combined with the relationship between oxygen purity and the energy consumption of the air separation unit, the optimal oxygen purity which minimizes the process energy consumption is obtained. In the ammonia production process with cold purification, the optimal oxygen purity is 95%, which can save 10.3% of the energy consumption of the air separation compared with the current process using the 99.6% purity oxygen. While in the ammonia production process with hot purification, the optimal oxygen purity is 96%, which can save 8.4% of the energy consumption of the air separation.

The main objective of the research was to develop a method of biomass grindability determination (Biomass Grindability Index), which would allow for a clear classification of different types of solid biofuels in terms of their milling properties. The objective of the research included also the assessment of the possibility of adaptation of the existing coal grindability determination methods for evaluation of biomass milling. In the course of research, the biomass grindability determination method was modified to obtain the highest possible reliability of the developed index. The scope of laboratory tests being focused on influence of circumferential speed of test mill beaters, particle size distribution of sample, test time, mass and volume of sample. The results of laboratory and industrial tests have shown that the grindability index based on mean particle sizes of feed and product is unreliable. Grindability of different types of biomass, comminuted in beater mills, can be clearly determined by the index expressed as the ratio of energy consumption during the test to the amount of specified product size fraction. During the study laboratory test results obtained for proposed grindability index were compared to other grindability indices determined for utilized in research types of biomass.

In this work, the liquefaction of coal and biomass with direct liquefaction strategy was explored. The point of liquefaction is both to utilize a greater amount of the current coal and biomass assets all the more productively and to create an alternative liquid fuel to oil. Along these lines, the procedure parameters must be resolved to expand the liquefaction efficiency. In addition, it is proposed to do the liquefaction efficiency, particularly in the reactant conditions, to expand the measure of oil. Process parameters were controlled by utilizing Factorial Experimental Design technique in the liquefaction procedures. The solid/liquid ratio was changed as 1/2-1/4, the catalyst concentration was 2–6%, the temperature was 375–400 °C and the duration was 30–90 min. Starting nitrogen pressure was set at 30 bar, stirring speed was 400 rpm, coal/biomass proportion was settled at 1/1. Tetralin as a solvent and MoO3 as catalyst were utilized. Toward the finish of the liquefaction procedure, the total conversions were computed in view of the acquired non-reactive solid (char). As indicated by the outcomes obtained, the most total conversion (81.9%) was acquired at a solid/liquid proportion of 1/2, a catalyst concentration of 2%, a reaction time of 90 min and a reaction temperature of 400 °C. In light of total conversions and elective liquid fuel (oil) in the given conditions, the solid/liquid ratio should be taken as 1/2, the catalyst concentration is 2%, the reaction time is 30–90 min and the reaction temperature is 400 °C. The lowest reaction time found, in this study, is the innovative solution for reducing co-liquefaction cost preferred.

Biodiesel appears as a replenishable and sustainable energy source and can be used a direct replacement to petro-diesel without any major transformations in ongoing diesel engines. This work concentrates on production of Calophyllum Inophyllum biodiesel (CIB) and preparing 10% blend (CIB10) sample to investigate the effects of varying the injection strategies and exhaust gas recirculation (EGR) in common-rail direct injection engine. The experimental results shows that 10% of pilot fuel and 90% main injection strategy (B10@P10-M90) is superior among all others injection strategies with respect to pure diesel. B10@P10-M90 fuel injection strategy produces the maximum efficiency of 35.8% and lowest fuel consumption of 0.25 kg/kWh compared to all the injection strategies. The carbon monoxide (CO) and hydrocarbon (HC) emissions are also found to be quite low compared to all the other test samples including pure diesel. However B10@P10-M90 results in higher average oxides of nitrogen (NOx) emission which is 18.9% higher in contrast to conventional diesel at full load condition. With the implementation of 10% and 20% EGR with B10@P10-M90, the average NOx emissions decreased by 14.4% and 27.6% respectively compared to B10@P10-M90 without any EGR without significant loss in the performance of the existing diesel engine.

Two sugarcane biofuels and mineral diesel fuel are tested under full load conditions, under the same values of performance and under the European Transient Cycle on an engine test bench, without any modifications to the ECU. The target is to compare engine performance and emissions. At full load, engine performance varies due to the variation in LHV. Under the same values of performance, the sugarcane biodiesel-LS9 provides the lowest THC emissions. The higher CN and exhaust gas recirculation of the sugarcane biodiesel-LS9 and the higher H/C ratio of the sugarcane diesel-farnesane compared to the diesel S50 provide a NOx reduction. Neither the increment in bsfc nor the increment of %EGR for the sugarcane biodiesel-LS9 deteriorate the combustion, so its CO emissions are lower. The sugarcane biodiesel-LS9 leads to the lowest NOx and PM specific emissions under transient operation, followed by the sugarcane diesel-farnesane. The THC and CO specific emissions are higher for the biofuels in comparison to the diesel S50. The main reason for these results is the impact of the properties of the biofuels on the ECU response However, both biofuels produce less harmful emissions at idle conditions, which supports their usage to reduce exhaust emissions in urban areas.

Brazil has a well-developed forest sector and is the largest producer of charcoal in the world in addition to being one of the main producers of wood. A big part of this production is destined to the steel industry. However, approximately 30 wt% of all wood energy is transformed into charcoal, and the other 70 wt% consisting of condensable and non-condensable gases (NCG) emitted in the atmosphere generating pollution and energy waste. With the purpose of altering this scenario, the present project, undertaken in laboratory scale from muffle furnace, saught as its main objective to carbonize species of Eucalyptus urograndis. Charcoal physical-chemical characterization, bio-oil and (NCG) produced by the process have also been done. In parallel, the performance of some operational variables (heating rate and final carbonization temperature) have been analyzed which affect the process of charcoal production through experimental design. The average income in charcoal, bio-oil and NCG has reached values of approximately 32.6, 40.1 and 27.3 wt% respectively. To obtain a quality charcoal as in the quantitative point of view (yield), as to the qualitative point of view (performance in fixed carbon and low friability), it must operate at a lower heating rate and milder final carbonization temperatures.

This study presents the energy and exergy-based performances of a solar dryer integrated with packed bed (TES) as thermal energy storage medium. As a sample application, drying kinetics of orange slices was determined. The aim of this study is to evaluate the thermal storage potential of the packed bed by focusing on energy consumption and exergy-sustainability indicators. Experiments were repeated twice a day (sunshine hours and off-sunshine hours). The results indicated that solar dryer integrated with packed bed reduced the moisture content of orange slices from 93.5% to 10.28% (at the first experiment) and 10.76% (at the second experiment), respectively. Total useful energy consumption for both the two status were detected as 89.892 MJ and 88.11 MJ, respectively. The exergy efficiency for the drying system during the sunshine hours ranged from 50.18 to 66.58%.The exergy efficiency of the drying process, in case of using the stored thermal energy, also changed between 54.71 and 68.37%. Moreover, a mathematical model was developed to predict the change of the moisture ratio of orange slices during time. According to the results of the model, Modified Henderson and Pabis Model presented the optimum parameters for determining the drying kinetics of orange slices.

The main purpose of this study was the optimization of torrefaction conditions for biochar cofiring with new Taguchi indicators. However, the combustion characteristics of biochar cofiring in different furnaces and reactors are distinct. Examining optimal torrefaction conditions using the Taguchi method based on maximum energy or mass yields is paradoxical. Accordingly, three indicators, that is S index, proximate-based index (PA index), and elemental-based index (EB index), were proposed for solid fuel combustion. To study the combustion behavior of biochar torrefied under optimal conditions, a single pellet combustor was employed to record the characteristic time and gas emission at various reaction regions. Furthermore, the effects of ambient temperature and biomass blending ratio (BBR) on combustion behavior were investigated in the single pellet combustion experiment. When the temperature was increased to 600 °C, the ignition delay time ranged from 8 to 29 s, whereas at 800 °C, the fuels were ignited within 4 s of each other. The total combustion times were shortened as the reaction rate increased. The total combustion time of Australian coal, raw Miscanthus, 50% blended biochar (S index), 50% blended biochar (PB index), and 50% blended biochar (EB index) were shortened by 19.3%, 18.9%, 14.2%, 12.9%, and 13.5%, respectively.

The increasing cost of fossil fuels as well as increasing environmental pollution has attracted research in alternative fuels and additives for improving the performance and reducing emissions of diesel engines without costly engine modifications. In the present article, an exhaustive analysis of the performance and emissions of oxygenated ternary fuel blends is done through modeling and experimental investigation to determine the optimal blending ratio of additives for reduced emissions. The Nitromethane-n-butanol–diesel blend is termed as bio-oxygenated fuel. Baseline data were generated by using diesel and a blend of 20% (v/v) n-butanol with diesel (B20). Ternary blends of Nitromethane (NM) and B20 containing 1–3% NM by volume were prepared and experiments were conducted. It was observed that 1% of Nitromethane by volume (NM1B20) gives best results for emission reduction. The overall effect of this ternary blend was reduction in smoke and nitrogen oxides (NOx) by 61.85% and 8.07%, respectively, as compared to diesel. Moreover, the performance of ternary blend was also found to be better than the base fuels. It was thus concluded that Nitromethane-n-butanol–diesel blends can be highly effective alternatives in reducing emissions in diesel engines with a little improvement in the overall performance characteristics.

One prevailing issue for assessing the performance of hydrothermal liquefaction is understanding the role of the extraction solvent used for product separation. This study evaluated the extraction agent's impact on the hydrothermal liquefaction products and energy efficiency. Three representative solvents (acetone, dichloromethane, and toluene) were chosen with three representative high-carbohydrate, protein, and ash content feedstocks (Chlorella sp., Nannochloropsis sp., and Enteromorpha pr., respectively). Extraction of the oil using dichloromethane led to the highest biocrude oil yield (dry biomass) for Chlorella sp. (48.8%), toluene for Nannochloropsis sp. (23.3%), and acetone for Enteromorpha pr. (9.8%). The solvent selection led to a maximum variation of 20.4% for all oil yields. Dichloromethane produced high energy recovery values (maximum: 67.1%) and low energy consumption ratios (minimum: 0.06) regardless of the feedstock chemical composition. Dichloromethane also led to consistently high net energy values and high fossil energy ratios amongst all feedstocks. We speculate that the solvent polarity, chemical structure, hydrogen bonding, and dipole-dipole interactions influenced output parameters by the selective isolation and extraction of the chemical compounds in the biocrude oil. This study suggested that the extraction solvent selection should be carefully considered and normalized for the reporting of hydrothermal liquefaction yields and energy efficiency values.

In this study, the utilization of textile fibres as energy feedstock in the form of biochar was investigated depending on the fibre type. The biochars were produced from waste natural and synthetic fibres and its blends. For this purpose, different types of textile fibres (cotton, viscose, polyester, acrylic) and their blends (cotton/polyester, acrylic/wool, acrylic/polyester, acrylic/viscose) were torrefied at temperatures between 300 and 400 degrees C. The effects of torrefaction temperature and fibre type on biochar yield and biochar properties (fuel properties, morphological and structural properties and combustion characteristics) were investigated. The results showed that the temperature had a significant effect on biochar yield whereas the fibre type was the only significant factor on energy densification ratio and biochar properties. The torrefaction of tested fibres and blends resulted in an energy-intensive solid fuel, having a negligible amount of ash and sulphur. Although torrefied acrylic based textile fibres had similar H/C and O/C ratios to bituminous coal, it was concluded that high nitrogen contents will limit their usage as fuel. Overally, this study showed that torrefaction of cotton and cotton/polyester textile wastes is a promising process for the production of a solid fuel, which can be used as a substitute fuel in coal/waste co-firing systems. (C) 2018 Elsevier Ltd. All rights reserved.

In this study, municipal solid waste was gasified with switchgrass, i.e., co-gasification, using a commercial-scale downdraft gasifier to produce power. The experiments were performed using a commercial-scale 100 kg/h downdraft gasifier at co-gasification ratios of 0, 20 and 40%. The hot and cold gas efficiencies, syngas compositions, heating value and yield, gasifier temperatures and tar content were measured and analyzed. The results indicate that co-gasification of up to 40% MSW performed satisfactorily. The heating values of syngas were 6.2, 6.5 and 6.7 MJ/Nm3 for co-gasification ratios of 0, 20 and 40%, respectively. The cold and hot gas efficiencies were 60.1, 51.1 and 60.0% and 65.0, 55.2 and 64.4% for co-gasification ratios of 0, 20 and 40%, respectively.

Lignite is one of common applied fossil fuels worldwide, and solid wastes like biomass as well as sewage sludge are promising alternatives of fossil fuels. The isothermal combustion performances of lignite/solid wastes (eucalyptus bark and sewage sludge) briquettes between 500 °C and 800 °C in a bench-scale fixed bed furnace were examined based on a macro-thermogravimetric analysis approach. Compared with untreated samples, the average combustion rates of lignite and sewage sludge with the microwave treatment decreased, while those for treated eucalyptus bark increased. The drying, devolatilization and char combustion processes overlapped in the isothermal combustion for all samples. The treated lignite had a high aromatic hydrocarbon, while both the treated sewage sludge and eucalyptus bark had high hydroxyl and methyl group (CH3). After the microwave pretreatment, the fuel rank of lignite was prompted, while that for eucalyptus bark and sewage sludge degraded. Through the microwave pretreatment, the activation energies of lignite, sewage sludge, and eucalyptus bark grew from 15.45 to 21.20 kJ mol−1, 18.23–20.77 kJ mol−1, and 13.27–14.22 kJ mol−1. The study can provide some basic data for the energy utilization of lignite and solid wastes.

Chemical looping combustion (CLC) is regarded as the most promising technology for CO2 capture to mitigate greenhouse gas effect. In this work, a technical and economic performance of CH4-feed CLC power plant by means of utilizing promising nickel-, copper-, and ilmenite-based oxygen carriers is studied. Nickel-based CLC power plant has the highest net power efficiency of 50.14%, followed by 48.02% for ilmenite-based case and 45.59% for copper-based case. By contrast nickel-based case has a specific CO2 emission of 1.44 kg/MW h, which is dramatically lower than the referenced NGCC with CCS system (40.10 kg/MW h). The economic analyse reveal nickel-based case is most economic-benefits due to the lowest cost of electricity (COE) of 71.66€/MW h, approximately 0.32 €/MW h and 13.06 €/MW h COE reduction benefits have been increased in comparison with ilmenite-based and copper-based case, respectively. The natural gas price has an important influence on COE, as approximately 49.73%, 48.60% and 56.30% of COE enhancement is expected with the natural gas price ranging in 4–8 €/GJ for nickel-based, copper-based, and ilmenite-based case, respectively. Finally a comparison between NGCC and CLC-related power system in terms of economic performance further demonstrates the feasibility of the latter system.

In this work, 138 datapoints, including elemental composition and ultimate analysis of various types of sewage sludge, and the hydrothermal carbonization reaction conditions, are used to develop a prediction model for the nitrogen content of the hydrochar. The results suggested that a two-layer feedforward neural network with five (05) neurons in the hidden layer can accurately predict the nitrogen content of the hydrochar based on the reaction temperature and the contents of nitrogen, carbon, volatiles and fixed carbon in the feedstock. Over 100 runs, the R2 and RMSE are in [87.547–99.097%] and [0.243–1.431] wt.% (db), respectively. Moreover, a statistical and regression analysis revealed that the sewage sludge-N is the main contributor to the hydrochar-N. Mostly, 40–70% of sewage sludge-N goes to hydrochar-N. The results are consistent with previous experimental reports, and this model can be used to predict the sewage sludge-derived hydrochar-N.

Microbial fuel cell (MFC) technology allows renewable energy production from the decomposition of organic matter present in wastewater. This technology, however, poses challenges that hinder scaling up of its usage in practical implementation. Also, resource recovery from the available waste sources is attracting attention due to the immense amount of valuable nutrients present in the wastewater. Herein, the present study focuses on investigating high-performance anodes, that is, using a stainless-steel brush (SSB) and carbon brush (CB) to accommodate the MFC in terms of energy production, leading to transformation into a microbial nutrient recovery system (MNRS) for nutrients’ recovery from wastewater. The present novel SSB anode system generated a stable voltage of ∼0.4V and a maximum power density of ∼400 mW/m2 whereas CB anode system produced the voltage and maximum power density of ∼0.5 V and ∼800 mW/m2, respectively. Besides, using the MNRS process, recovery of nutrients in terms of PO43− (80–83.4% for CB-MNRS and 60–69.5% for SSB-MNRS when using feed PO43− concentration of 10–20 ppm) and NH4+ (63–80.64% for the CB-MNRS and 52–70% for the SSB-MNRS when using feed NH4+ with a concentration of 10–20 ppm) was achieved.

The present study evaluates a sugarcane biorefinery producing ethanol through juice fermentation and methanol via gasification of sugarcane lignocellulosic residues and liquid fuel synthesis. Two technologies of gasification named entrained flow and circulating fluidized bed are compared. Flowsheet modeling and thermo-economic analysis methods are applied, followed by a multi-objective optimization based on a genetic algorithm. The optimum Ethanol–Methanol biorefinery design options are compared with other previously studied sugarcane biorefineries. The results show that the biorefinery's energy efficiency increases significantly with the integration of a methanol production plant in a conventional ethanol distillery. The configuration using an entrained flow gasifier presents lower conversion efficiency than the one using a circulating fluidized bed gasifier. However, for the entrained flow gasifier configuration, the size of the methanol production process could be bigger since more heat is available for the ethanol process favouring the integration with the ethanol plant. Higher energy efficiency due to increase of methanol production leads to a higher total investment for both gasification technologies. The cost analysis shows that the calculated methanol production cost is 30% higher than its current market price. Environmental incentives for biofuels could change this scenario but are not in the scope of this study.

Co-hydrotreating of microalgae (M) and UEO (used engine oil) was examined for the direct production of gasoline and diesel fuels or blending components. The addition of the noble metal catalysts promoted the cracking and in situ hydrogenation of liquid products (oils) and was beneficial for the production of liquid products. Using Pt/C as the catalyst, the effects of temperature (350–450 °C), time (2–6 h), UEO/M mass ratio (6/0–0/6), catalyst loading (1–60 wt.%), and initial H2 pressure (0.1–8 MPa) on the yield and quality of the liquid products were studied. A synergistic effect existed during the co-hydrotreating of the UEO and microalgae, which not only favored the production of liquid products but also promoted in situ denitrogenation and deoxygenation. Co-hydrotreating produced an upgraded oil with fuel properties (e.g., density, calorific value) comparable to traditional liquid transportation fuels derived from fossil fuel. The S content (45 ppm) of the upgraded oil produced at 450 °C is even below the minimum requirement of China IV diesel (50 ppm). Examination of the composition of the upgraded oils showed the formation of dominant light aliphatic and aromatic hydrocarbons that could also be used as a chemical feedstock.

This paper is aimed at performing an environmental evaluation regarding biofuel production. The process combines four sections: biomass fast pyrolysis to bio-oil with two phases, oil-phase upgrading by hydrotreating, using H2 obtained by steam reforming, and a new process to produce Fischer-Tropsch biofuels from supercritical water reforming of the aqueous phase. This phase can be valorised in the latter process entirely so natural gas is reformed to H2 (case-study 1), or partially so a fraction of this aqueous phase is reformed (case-study 2), or all this phase is reformed to H2 (case-study 3). The two former can include CO2 storage and aqueous phase concentrations were 15, 25 and 35 wt% organic compounds. At 25 wt%, the global warming potential is 11 g CO2-eq/MJ-biofuel for the case 2 with CO2 storage, while it was 11.3, 12.6, 27.7 and 34 g CO2-eq/MJ-biofuel for the cases 3, 2 without CO2 storage, 1 with and without CO2 storage, respectively. Thus, the case-study 2 with CO2 storage gives the minimum global warming potential, allowing significant reductions with respect to the use of fossil fuels. For the other categories, the case-study1 presents the lowest impacts. Similar trends are found at 15 and 35 wt%.

During the operation of industrial gasifier, the concentrations of CO2 and H2O in gasification media vary with the change of stages, causing the gasification process being affected accordingly. Therefore, dividing the gasification process into different stages to study the effect of multi-stage switching atmosphere is significant. The conversion rate, reaction characteristics and reaction process for the gasification of Xiaolongtan (XLT) coal char in different atmospheres (CO2/H2O/N2) switching in the early, middle and late reaction stages were investigated using thermo-gravimetric analysis (TGA). The results indicated that the average reaction rate of coal char with H2O was approximately 3 times that of CO2. Increasing H2O concentration improved the reaction and conversion rate of coal char, which was the most obvious in the early stage. With the H2O concentration increasing from 0 to 95%, the increment of conversion rate in the early, middle, and late stages were 7.13%, 4.40%, and 3.92%, respectively. Thus, considering the problem of H2O corrosion in practical production, the H2O concentration could be appropriately increased in the early stage to improve efficiency. Compared with the random pore model, the shrinking core model fitted the gasification process of coal char better in a highly reactive 95% H2O/5% N2 atmosphere.

Automotive engines are encouraged to utilize biofuels to lower the net CO2 and to enhance the usage of renewable energy. With well-proven biodiesel engine characteristics, a comprehensive study about the impact of biodiesel on the fuel filter is lacking in the literature. Hence the current study investigates the comparative impact of higher blends of biodiesel and diesel on the fuel filter. Here, the authors have conducted both experimental and simulation studies on the fuel filter with diesel, two biodiesel fuels namely karanja, and waste cooking oil. Filter blocking tendency (FBT) was measured for the test fuels following ASTM D2068 . Also, a comparative tensile strength analysis of an automotive filter media was examined. The test results reveal that FBT increases exponentially with an increase in biodiesel blend concentration with a maximum FBT value of 30 for karanja biodiesel. Further, the tensile strength of the filter media reduces significantly with soaking in biodiesel compared to fossil diesel. Filter pressure drop measurement results with biodiesel were observed to be 35% higher than diesel. Consequently, effective countermeasures such as fuel preheating, varying the filtration area and ethanol blending are proposed to reduce the filter pressure drop with biodiesel. Filter pressure drop with karanja can be reduced similar to diesel fuel by increasing the fuel temperature by 16 °C or enhancing the filtration area by 35%. Karanja blended with 20% ethanol was also observed to have lowered the pressure drop. The present study concludes that neat biodiesel operation affects the filtration process and the filter media of the conventional fuel filter significantly.

In the ethanol production process from sugarcane molasses, the distillation process is a high-energy demand stage. The distillation energy efficiency is strongly associated with the alcoholic fermentation performance in the process. The final ethanol concentration in the alcoholic wines has a direct impact on consumption of thermal energy in ethanol separation. In this paper, ethanol production with a H-SBMF (Hybrid-Simple Batch Membrane Fermenter) using PDMS (polydimethylsiloxane) pervaporation membrane was modelled and simulated, in order to determine its influence on energy consumption in distillation. Steam in distillation and electrical energy needs in permeate recovery were mainly influenced by membrane adaptation. The H-SBMF achieved a higher ethanol production in the range of 10–13% compared to the conventional batch fermenter, and an increase in productivity of 150%. The distillation system consisted of two sets of columns: the ethanol recovery column and the rectification column. The permeate recovery system (i.e. vacuum and compression) was regarded in order to evaluate the electrical energy requirement, and the thermal energy demand was evaluated. A decrease in steam consumption was evidenced by the adaptation of the membrane to the fermenter. Higher energy efficiencies were achieved in distillation with larger membrane areas, achieving almost 17% steam reduction.

This paper presents an in-depth exergy analysis of the ethanol fermentation process with various forms of fungus Mucor indicus under aerobic and anaerobic conditions to select the most productive and sustainable conditions. Various carbon sources including fructose, glucose, and sucrose as well as the whole and inverted sugar beet and sugarcanes molasses were used during the fermentation. The rational and process exergetic efficiencies were found to be in the range of 65.21%–88.54% and 0.00%–44.31%, respectively. Overall, the exergy-based parameter based on the process outputs could provide useful information about the sustainability and productivity of the fermentation process compared to the rational analysis. More specifically, the inverted sugar beet molasses with MF (mostly filamentous) form of M. indicus under anaerobic cultivation was shown to be the best option for industrial production phase with respect to the productivity and sustainability issues. The results obtained confirmed that the process yield alone cannot perfectly reflect the exact sustainability parameters of the renewable ethanol production systems. Finally, the developed exergetic framework could help engineers to couple biochemical and physical concepts more robustly for achieving the most cost-effective and eco-friendly pathways for bioethanol production.

Turpentine, a mixture of terpenes obtained as a product from oleoresin distillation or as a side product from paper industry, can contribute to the production of oxygenated fuels from renewable sources with properties different from normal alcohols or typical esters. In the present work, the product of turpentine oxyfunctionalization (oxyturpentine), which is composed mainly of nopol, α-terpineol and α-pinene, is evaluated as diesel fuel component blended at 20% vol., by measuring the performance and emissions of a Euro 6 engine under a standard driving cycle. The results show a reduction in particulate number, particulate matter and nitrogen oxides (the tightest emissions from diesel engines), while carbon monoxide and hydrocarbon emissions were increased. The emissions were influenced by the fuel properties and the changes in equivalence ratio and the EGR in the engine (derived from the fuel properties). These results show a high potential of oxyturpentine to be used as component of diesel fuel.

Regarding the supply of fossil fuels, greenhouse gasses emission, global warming, and increasing fuel price; there is a need to find alternative energy resources, which are renewable, environmentally sustainable, and economically viable. Agro-industrial biomass such as sugarcane bagasse, rice and wheat straw, corn stover, and switchgrass, named as lignocellulosic biomass (LCB) which is inexpensive, abundant, renewable, and provides a unique natural resource for large-scale and cost-effective bio-energy production. During the production of biofuels, pretreatment is a necessary step due to the recalcitrant structure of LCB. Various pretreatment methods were employed with a different mechanism of action, feasibility, and practicability to produce high yield biofuels. Since many years ago, the development of an effective pretreatment method has been challenging due to the existence of barriers and obstacles. Besides, each pretreatment method has its advantage and disadvantage, which should be investigated to obtain a higher yield of bioethanol. In this paper, the recent findings regarding the application of various pretreatment techniques such as chemical, physical and biological methods for bioethanol production from LCBs have been reviewed. The limitations of the mentioned methods based on the existing barriers were explained, and the future recommendations were discussed.

Chemical Looping Combustion (CLC) is an emerging technology that has shown great promise for capture of almost pure CO2 in combustion of fossil fuels in power plants. In this paper, the CLC process is modeled in ASPEN Plus and then validated using experimental data from combustion of three types of biomass as fuel, and Hematite (Fe2O3) as an oxygen carrier (OC). Three types of biomass used in the simulation are pine sawdust, almond shells, and olive stones. The effect of the fuel reactor temperature on gas concentrations (namely CO2, CO, H2, and CH4) in the fuel reactor, and the carbon capture efficiency are examined. It is found that all three biomass types have very high carbon capture efficiencies, with pine sawdust and almond shell reaching nearly 100% capture efficiency when temperatures are greater than or equal to 950 °C, while olive stones reach a capture efficiency of nearly 100% at temperatures greater than 980 °C. It is also found that the CO2 concentrations in the fuel reactor vary across the three biomass types. The effect of using Mn2O3 as OC in place of Fe2O3 was also investigated. It was found that switching the oxygen carrier to Mn2O3 caused the concentrations of CO and H2 in the fuel reactor to decrease slightly, while the concentration of CO2 increased slightly. Additionally, a mixture of coal and biomass at 895 °C was used with each of the two oxygen carriers. The results show that the system using Fe2O3 had a greater power output than the one using Mn2O3, and that power output increased as the fraction of coal in the coal-biomass mixture increased.

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.

This paper aims to establish a new standard process for heat and mass integration of hydrothermal liquefaction, co-located with an existing Kraft pulp mill, to produce bio-crude. Hydrothermal liquefaction is an energy-intensive process that operates at high temperature and pressure and produces a biocrude similar to conventional crude oil. The key advantages of installing hydrothermal liquefaction in proximity with a Kraft Mills enables the use of black liquor as a feed to hydrothermal liquefaction, asset repurposing and optimisation, as well as supply chain and logistics integration. This work follows a design process to increase the energy efficiency of the hydrothermal liquefaction process by using an iterative mass and heat integration procedure to optimise mass and energy flows and assets of the hydrothermal liquefaction process. The method uses process simulation tools, Pinch Analysis, heat exchanger network design tool, and the understanding of the process constraints to develop a heat exchanger network for the hydrothermal liquefaction process with maximum energy recovery, minimum number of units and enhanced mass integration. The number of heat exchangers in the network reduced from 14 to 7 when the proposed method was applied. Substituting bio-crude from the new integration hydrothermal liquefaction process for conventional fuels has the potential to decarbonise transport fuels by 11.3 kg CO2-e/GJ of fuel.

Bio-oil is produced as a promising fuel for improving the economics of biomass. However, bio-oil utilizations suffer from challenges due to its complex compositions. In this research three bio-oil samples (BSR, BPA and BFT) were blended with coal/char to prepare slurries as biofuels. The thermogravimetric analysis of combustion and ash compositions of biofuels were investigated. Results showed that bio-oils have more weight loss peaks than coal/char, and the Tm is concentrated in the range from 476.4 °C to 495.2 °C, which are much lower than char. The contribution of coal/char and bio-oils to biofuel blendings can be clearly seen in the combustion profiles. There is a synergistic effect between bio-oils and coal/char improving the combustion performance. Tb of lignite BSR slurry reduced up to around 40 °C in comparison with lignite. The temperature range for combustion became narrow. By blending BSR, the Ea of lignite, long flame coal and char reduced 5.65 kJ mol−1, 13.56 kJ mol−1 and 6.31 kJ mol−1, respectively. Lignite BSR slurry with the lowest activation energy presented best combustion characteristics among all biofuels. The improved performance may attribute to AAEMs contained in bio-oil and microexplosions occurred in combustion, and AAEMs also help form lower fusion temperature of ashes.

This study attempted to improve the properties and energy efficiency of torrefied biochar produced from the waste of two common street trees, namely, Washingtonia filifera and Sterculia foetida. The effects of various torrefaction temperatures (210–300 °C) and reaction times (30 and 60 min) were evaluated. W. filifera petiole (WFP) biochar exhibited a higher weight loss and energy yield than S. foetida follicle (SFF) biochar. As the torrefaction temperature and time increased, the higher heating values (HHVs) and fuel ratios of both types of biochar increased, and the H/C and O/C atomic ratios became similar to the atomic ratios of lignite and peat due to the decomposition of hemicellulose and cellulose in the biomass structures. Furans and acetic acid, respectively, were the major gaseous products of WFP and SFF torrefaction. The maximum energy return on investment (EROI) of 23.2 was achieved for WFP biochar torrefied at 210 °C for 30 min. Greenhouse gas (GHG) emissions can be reduced markedly by 74.7–91.6% if biochar is used as a substitute for bituminous coal. Moreover, cofiring WFP or SFF biochar with bituminous coal at power plants is sustainable and economically beneficial because of the high HHV, stability, thermal performance, sufficient EROI, and low GHG emissions.

This article presents a novel active-mode indirect solar dryer consisting of highly efficiency through-flow evacuated tube collector for air heating. A DC fan powered with solar photovoltaic (PV) module is provided for forced air flow through this dryer. The dehydration chamber is of tray type with loading capacity of 6 kg–45 kg depending on the drying product. The dryer was evaluated to dry fenugreek leaves (Trigonella foenum-graecum) and turmeric (Curcuma longa) in semi-continuous mode; and respective overall thermal efficiency was found to be 34.1% and 23.6%. The respective thermal efficiency in open sun drying (OSD) was 5.7% and 5.4%. The quality of dried fenugreek leaves and turmeric was found better than OSD. Economics of the solar dryer indicate the capital cost is negligible in comparison to cumulative present worth of life cycle savings. The values are 211,262 INR (1 US$ = 74.57 INR) and 229,152 INR respectively for fenugreek leaves and turmeric; and capital cost of the dryer is only 50,000 INR. The low value of payback period also confirms economic viability of this dryer. The generalized economic curves have also been plotted.

The present study aims to run a diesel engine completely with renewable source, which is biogas and waste cooking oil methyl ester (assumed when cooking methods not changed) on a dual fuel mode. Further, this study also attempts to unfold the combined effect of both fuel injection parameters and compression ratio on its performance, and combustion analyses of a diesel engine, modified to run on biogas-biodiesel. A series of tests were conducted by considering three different parameters (injection timing, injection pressure and compression ratio (CR)) at three different levels. i.e., injection timing advanced to 3°CA from standard 23°CAbTDC, injection pressure increased to 240 bar from standard 200 bar, one higher and one lower compression ratio from standard CR17.5. The results obtained were compared with the diesel at engine’s original settings (CR17.5, 23°CAbTDC, 200 bar and 4.4 kW). It was found that, the combination of CR18.5, 240 bar injection pressure and 24.5°CAbTDC gave a maximum BTE of about 31.2%. At the same condition, HC, CO and smoke emissions were found to be lesser by 55.5%, 3.5% and 19.1% respectively than diesel at full load. However, for the same CR and 240 bar, advancing from 24.5°CAbTDC to 26°CAbTDC resulted in a poor performance.

The development of a Ca-based CO2 capture sorbent from a limestone-rich mine waste via aqueous mineral carbonation was first time evaluated. Aqueous carbonation of calcined oil shale mine waste rock was conducted at the laboratory scale at ambient temperature and atmospheric gas pressure using CO2 gas mixture simulated the average exhaust gas composition of a fossil fuel power generation plant. The dissolution and carbonation of calcium were found to be optimal at 2.5% pulp density and were found to proceed faster during the initial 5–10 min. The overall aqueous carbonation efficiency was estimated at ≥89%. The carbonation process resulted in the production of pure calcite, whereas a mixture of Ca and Mg carbonates was found in the reaction residue. The CO2 uptake capacity (∼80 wt%) of the developed Ca-based sorbent was promising and revealed that it can be used for direct CO2 capture.

Co-combustion of coal with distillery sludge waste (DSW) was investigated in a laboratory-scale Drop Tube Furnace (DTF) plant. This study examined the feasibility of combustion of sludge with coal using preliminary testing methods, such as thermogravimetric, ultimate and proximate analysis followed by combustion experiments. These methods helped to identify burnout efficiency, emitted pollutants, and metal constituents in the bottom/fly ash. The ratios of coal to DSW in the feed was 90:10%, 95:5%, 98:2% and 100:0% by dry weight basis. The vibrator feeder and airflow rate were set at the rate of 1.5 kg/h and 150 L/min with slightly negative pressure. The concentration of gases (i.e. nitrogen oxides (NOx), sulphur dioxide (SO2), carbon mono-oxide (CO), hydrocarbon (HC)) and particulate matter (PM) on DSW combustion was measured and compared with the combustion of coal. The pattern of gaseous emission and combustion efficiency showed high degree linear combinations through Pearson’s correlation coefficient. The decrease in the concentration of PM (76.67 ± 10.41 mg/m3 to 91.33 ± 17.62 mg/m3) and SO2 (444 ± 20.63 mg/m3 to 156.60 ± 12.26 mg/m3), increase in the concentration of NOx (136 ± 15.41 mg/m3 to 387 ± 15.2 mg/m3) and CO (26.15 ± 5.36 mg/m3 to 824.32 ± 43.70 mg/m3), unburnt carbon percentage in the fly ash, and clinker formation were taken into account to optimum the sludge proportion in the DTF under a given set of combustion conditions. Most importantly, an increase in sludge quantity (i.e. 2%, 5%, and 10%) showed a decrease in the burnout efficiency (98.41%, 95.91%, and 92.6%, respectively).

An experiment was conducted to investigate the effects of methane content in natural gas on combustion and performance of a liquefied natural gas (LNG) heavy-duty engine. Two kinds of LNG with different methane contents (i.e. 93% and 99%), in combination with three compression ratios (i.e. CR11.6, CR14 and CR16) and varied spark timings were tested and compared at various engine speeds. The results show that natural gas with 99% methane content has better actual antiknock performance than the one with 93% methane content, and subsequent better power performance and fuel economy. When compression ratio is increased from 11.6 to 14, natural gas with 99% methane content can maintain the maximum loads at all tested speeds, and achieve a maximum decrease of 6.4% in BSFC. On the contrary, the maximum load at high-speed is limited for natural gas with 93% methane content due to knocking combustion. Moreover, natural gas with 99% methane content has larger knock-limited spark advanced angle compared to the one with 93% methane content, so it achieves earlier ignition and then lower BSFC. In conclusion, higher methane content has better comprehensive performance than the lower one in natural gas engines with high compression ratio.

Given the scarceness of fossil fuels and high volume of pollution caused through the consumption of these fuels, many efforts are being made to produce alternative fuels. Biodiesel is one of the alternatives to diesel fuels. The main problem with biodiesel production is higher operation costs, as compared with diesel fuels. In this study, waste cooking oil and cow bone as the catalyst were used to reduce feed costs as much as possible. Moreover, a microreactor was utilized to reduce the residence time to 1 min. Using Box-Behnken design method, the effect of different variables including catalyst concentration (calcined cow bone), oil to methanol volume ratio, residence time, and reaction temperature on the purity of produced biodiesel were examined. The results showed that when using a catalyst concentration of 8.5 wt %, an oil to methanol volume ratio of 2.25 vol: vol, a residence time of 60 s, and a temperature of 63.1 °C, the maximum purity of biodiesel was 99.24%.

Single particle combustion behaviours of coal-biomass fuel mixtures are studied. Different biomass i.e. sawdust, wood and rice husk is blended with locally available low grade coal to carry out the experimental investigation. The combustion of solid fuel consists of flaming combustion and char combustion. Rice husk showed higher flaming time and char glowing time because of higher ash and particle density. The burning time of coal-rice husk mixture fuel sample is higher compared to other samples due to the combine effect of particle density and ash content of the fuel samples. Ignition mass flux of saw dust is higher compared to rice husk and wood fuel particles because of the presence of higher volatiles in sawdust. The diameter index for flaming combustion, char combustion are 1.13 to 0.47 and 0.63 to 1.23 respectively for 0%–40% coal in coal/wood fuel mixtures. It is observed that with the increases in surface area/volume ratio, flaming and char combustion decreases due to reduction in effective surface area of the particle for combustion. This study concludes that particle size or surface area/volume together with particle density are the primary controlling parameter for better conversion of fuel mixtures in any co-combustion system.

With huge demand of herbal medicine worldwide, herb residue (HR) treatment is attracting growing attention. This work proposed an integrated energy conversion system to treat and utilize HR, which contained a crushing and drying section to pretreat HR, a gasification section to convert HR into syngas, and a boiling section to produce hot steam for HR drying and herb steaming. A pilot scale plant was established to validate its feasibility. The results showed that HR with particle size below 10 mm and moisture content about 20 wt% was qualified as gasification feedstock. The energy efficiency, syngas heat value, and syngas yield during gasification reached 76.1%, 5.7 MJ/Nm3, and 0.6 Nm3/kgHR, respectively. When treating each kg of HR, 1.0167 kg of wastewater was emitted, which primarily came from HR dehydration and herb steaming. Meanwhile, 0.3292 kg of hot steam with 0.89 MJ of enthalpy would be produced per kg of HR as net energy output. This integrated system fully considered the upstream and downstream adaption of HR gasification technique. Highly efficient disposal and utilization of HR were thus achieved. It is hoped that this work could promisingly enhance the overall efficiency of herbal medicine production industry.

In terms of heat energy, woody biomass is not as effective as fossil fuels owing to its hydrophilic characteristics and low calorific value. These disadvantages can be overcome through torrefaction, a low-temperature pyrolysis method that can increase the energy density of woody biomass by increasing its carbon content ratio. However, it is difficult to increase the calorific value within a short processing time, while long processing times decrease the useful heating value. Therefore, optimal conditions need to be determined. Accordingly, this study attempted to optimize the torrefaction of woody biomass using a one-dimensional simulation analysis. Changes in the elemental contents of biomass were predicted by analyzing the mass reduction and characteristics of volatile matter emission due to torrefaction, and changes in the calorific value were derived. Comparing experiments and simulations. We estimated the calorific value and optimal conditions according to the process temperature and time (200 °C at 40 min, 230 °C at 30 min, 250 °C at 20 min). This study provides preliminary findings for the effective utilization of biomass, a material that is usually discarded.