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The mixing behavior of light paper pellets in a sand fluidized bed is investigated for varying proportions of paper pellets (0–20 mass%) over a range of superficial air velocities (0–1.5 m/s) at ambient conditions. It is found that a fluidization number greater than 2 is essential to achieve good mixing as long as the proportion of paper pellets in the bed is up to about 10 mass%. For 20 mass% of paper pellets in the bed, mixing did not occur and paper pellets preferentially collected in layers. Bed voidage and minimum fluidization velocities for mixed beds of sand and paper pellets are reported. These studies provide the supporting data needed for the co-combustion of paper pellets in a hot-sand, fluidized bed.

Since the first oil crisis in the seventies, potentials for energy-efficiency improvements in the short and medium term have been studied extensively. Numerous analyses have indicated that energy-efficiency improvements of about 30–50% are technically feasible in industrialized countries over a period of one to two decades [ETSU, 1984; Maier, 1986; Lovins and Lovins, 1991; Beer et al., 1994].

The aim of this paper is to develop a novel method for the retrofit of Heat Exchanger Networks based on Bridge Retrofit analysis. The method identifies Retrofit Bridges that correspond to energy saving modifications using two new proposed tools: The Heat Surplus-Deficit Table and the Modified Energy Transfer Diagram. These tools both allow the identification and quantification of Retrofit Bridges. These tools have been developed following conventional Pinch Analysis tools such as the Composite Curve and Grand Composite Curve. The connection between the conventional Heat Exchanger Network synthesis tools and the proposed retrofit tools is established to improve understanding of the method and relate it to what is currently used in both literature and industry. The method is demonstrated with a simple illustrative example and a more detail paper mill case study. The paper mill incorporates a paper machine and paper recycling plant and is co-located with a Kraft pulp mill in New Zealand. Results from the retrofit method suggest a retrofit design that will achieve an annualised profit of NZD 570,000/y (USD 414,000/y) with a payback of 2.4 y.

The economic feasibility of producing ammonia through the gasification of three different feedstocks produced in pulp and paper mills is investigated in this paper. The first case uses black liquor, the main by-product of the kraft pulping process, as the feedstock, and in the other two cases pulp sludge (PS) and waste sludge (WS) are co-gasified with black liquor. For all three cases, a process model in which mass and energy balances were calculated was developed. The model results were used to estimate the equipment size and estimate costs. Techno-economic models were developed and ammonia production costs were calculated. A case study for Alberta, a western Canadian province, was conducted. The results indicated that for a 10% discount rate (or internal rate of return [IRR]), ammonia production in all three cases is cost competitive with current ammonia prices. The cost of production (COP) of ammonia for all three cases ranges from 743 to 748 $/t. Sensitivity and uncertainty analyses were conducted on the estimated COP, and the results show that the COP is the most sensitive to the capital cost, discount rate, electricity price and plant lifetime.

The integration of different conversion technologies can strongly contribute to the biomass potential exploitation. To this aim, the use of intermediate pyrolysis biochar is analyzed in this paper as an alternative co-substrate in anaerobic digestion. The specie Ampelodesmos mauritanicus has been specifically chosen in this case for its capacity to tolerate, accumulate and, in some cases, degrade organic and inorganic pollutants. The biochar, produced under intermediate pyrolysis conditions at 450 °C, 500 °C and 550 °C, has been here considered for a biomethane potential assessment. The intermediate pyrolysis process improves the herbaceous bioavailability and promotes the microbial activity by reducing the digestion lag phase. Three reactors, namely B450, B500 and B550, have been considered in this study. Acclimatized cow manure from food wastes digestion has been used as inoculum with 5 g of biochar. The reactors have been continuously monitored for 15 days keeping the temperature fixed at 37 °C. Excluding the inoculum contribution, an accumulated methane production of 465–540.4 ml CH4/g-VS has been measured with an LHV evaluated in the range 25.8–26.9 MJ/kg. The modified Gompertz equation has been then used to describe the influence of biochar production temperature on methane conversion. A lag phase of 1.8, 2.2 and 3.8 days respectively for B450, B500 and B550, has been estimated showing an inverse proportionality to the biochar production temperature. The biomass to biogas energy conversion analysis reveals a reduction in the efficiency with the biochar production temperature increase. This fact is attributed to the steep reduction in volatile solids occurring by increasing the pyrolysis process severity. As a whole, the paper present a novel approach to possibly combine phytoremediation and production of renewable energy by using Ampelodesmos mauritanicus.

Black soldier fly larvae containing high lipids had been considered an novel sustainable feedstock for lipid extraction to biofuels. The insect lipid was extracted with microwave assisted solvent extraction method. The energy consumption of this way was analyzed to determine the feasibility of the lipid extraction process. The comparison of the effects of different extraction conditions (dehydration methods, water content, extraction temperature, extraction time, equipment power, and solute-solvent ratio) on the energy consumption of lipid extraction from the energy insect was investigated systematically. The dewatering of the insect biomass was the most energy consuming step via a dry extraction method in this paper, constituting about 40–80% of the total energy consumption demand. Within the ranges of extraction factors values compared in this analysis, the microwave radiation powder and lipid extraction temperature had a pronounced effect on the total energy consumption in the ranges of investigated parameter. At last, the lipid extraction yield-dependent evolution of energy consumption for different extraction conditions was also investigated. Anyway, the economic and environmental aspects of lipid extraction from the energy insect needed to be further improved for its large scale implementation in the future.

This paper present the results of a batch study on thermal-acid pre-treated sugarcane bagasse (SB) and food waste (FW) as the substrate with waste activated sludge (WAS) as inoculum. Experiments were conducted in six different batch reactors under ambient condition. Each batch reactor was fed with varied substrate ratio (mixture of SB+FW) maintaining inoculum constant (225 mL) to investigate the highest methane generation. The thermal acid pre-treated sugarcane bagasse (SB) with food waste at mixture ratio (SB: FW∼ 35:65) had resulted the maximum biogas production of 7338 mL followed by (SB: FW ∼ 50:50) - 6747 mL and (SB: FW ∼ 100:0) - 4040 mL. The maximum reduction in Total Solids (TS) concentration was achieved 57% at mixture ratio of [SB: FW ∼ 65:35] followed by 44%from [SB: FW ∼ 85:15] and 41% from [SB: FW∼100:0]. Thermal acid pre-treated sugarcane bagasse produced 81% higher biogas generation at mixture ratio of [SB: FW ∼ 100:0], 63% at [SB: FW ∼ 50:50] and 22% at [SB: FW ∼ 35:65] and results obtained for biogas generation were modelled using Gompertz and logistic model and fitted well.

This paper analyses the improved energy and environmental performance of the biomethanation of a mixture of sheep manure (20% by weight) and cheese whey (80% by weight) in a reactor of 2 L capacity containing 2 g of charcoal in the form of a fixed bed with respect to the same process but without the charcoal in the reactor (control experiment). The results show an increased methane production of 27.05% and a reduction of the H2S content in the biogas of 34.7%, over those obtained in the control experiment. These marked improvements of the biomethanation process are attributable to the content of highly electropositive metals such as K and Ca in the charcoal which, because chemical reactions, can increase the pH of the medium and thus favour the processes of methanogenesis and sulphate reduction. Charcoal would act as a bacteriological adherent promoting the biomethanation of the organic waste materials used in the study.

This paper addresses the techno-economic, energetic and environmental assessment of the indirect and direct production of bioenergy using Pinus patula (PP) as raw material. Ethanol and synthesis gas are evaluated as main products through biochemical (fermentation) and thermochemical (gasification) routes, respectively. The complete characterization of the raw material was performed aiming to determine the chemical, proximate and elemental composition of the PP that is used as starting point for the simulation procedure. Mass and energy balances were obtained from the simulation of both processes using the software Aspen Plus v9.0. Different economic criteria such as Net Present Value (NPV) and Payback Period (PBP) were used to determine the profitability of both processes. The overall energy efficiency was calculated considering the relation between the energy content of the products and the energy content of the inputs (raw materials and utilities). The environmental assessment involves an attributional life-cycle assessment (LCA) of different systems such as seedlings production, PP cultivation, harvesting and collection, and the evaluated processes using a cradle-to-gate approach. As a result, the production of ethanol evidenced a low production cost (0.549 USD/L), higher energy efficiency (45.1%) and higher CO2 emissions (0.17 kg per MJ EtOH) in comparison to the biomass gasification.

This paper presents the overall performance, emission and combustion characteristics of the engine, when fuelled with biodiesel blends of Calophyllum Inophyllum methyl ester as injected fuel and babul wood chip derived producer gas as inducted fuel at constant injection timing (230bTDC), injection pressure (230 bar) and speed (1500 rpm). To improve overall performance, combustion and reduced emission characteristics of the engine, the combustion chamber was varied with 5 different geometries. Experimental results revealed that Toroidal re-entrant combustion chamber had higher Exhaust Gas Temperature and Brake Thermal Efficiency by 20.75% and 6.37% than that of HCC, while Brake Specific Fuel Consumption was reduced by 4.49% at optimal loading condition. However, engine overall performance of TrCC was found to be comparable with Hemi-spherical chamber and other designed combustion chambers. Similarly, comparing exhaust emissions, Oxide of Nitrogen and Carbon dioxide were on its higher side by 19.90% and 27.20% than normal HCC. On the contrary, carbon monoxide, Hydrocarbon and Smoke opacity for TrCC were found to be 76.12%, 33.71% and 38.67% lower than HCC. From the above study, it is finally concluded that converted renewable fuels with TrCC might be utilized as an alternative fuel without any exhaust related problems.

This paper presents a comprehensive approach for improved efficiency of a once-through Benson type coal boiler in a coal-fired power plant. In the method, petrographic properties, ultimate analysis and proximate analysis of coal feedstock is firstly determined. In addition, operational parameters, like O2 concentration, coal mass flow, air/fuel ratio and load were varied to establish their impact on both SO2 concentration and NOx reduction. The coal samples are led by inertinite in the range of 34.4 – 47.8 vol% afterward total vitrinite content in the range of 20.3 – 24.4 vol%. Liptinite content occurs in minor proportions of 1.8 – 4.3 vol% range. The optimum conditions for simultaneous reduction of NOx emission and SOx are achieved when the O2 concentration is 3.58% and coal mass flow of 288 tonnes/hr. Reducing coal mass flow from 331 to 288 Tonnes/hr caused high SO2 concentration to reduce from 3862 mg/Nm3 to 2232 mg/Nm3. Moreover, NOx concentration reduced from 350 mg/Nm3 to 310 mg/Nm3 when the air/fuel ratio varied from the lean side to the rich side. The optimum air/fuel ratio of 7.24 resulted in NOx reduction. The highest boiler efficiency of 90.97% was achieved at full load and the O2 concentration of 3.58%.

Spent tea waste (STW) is an organic waste that is disposed in open land after preparation of tea. Generally, it is disposed in an open land which increases anthropogenic gases. Converting it into useful energy or value added product may reduce disposal problem and anthropogenic activity. In this study, STW was co-digested with cow manure (CM) for obtaining biogas by anaerobic digestion. For this purpose, STW was mixed with CM at different proportions, namely 50:50, 40:60, 30:70, 20:80, and 0:100 percentages on a mass basis, the samples were used in five different anaerobic digesters. The samples were kept in different anaerobic digesters for the study. The effect of important input parameters like pH, Carbon to Nitrogen (C/N) ratio, and digestion time on the biogas production were studied. Further, the collected biogas from the digesters were characterised to ensure the suitability for use as a renewable fuel. Furthermore, the digested slurry was also analysed for its use in agriculture sector. The results are presented in this paper.

The increase in prices and our dependence on fossil fuels coupled with concerns about harmful emissions have motivated researchers to look for renewable and alternative fuels that have clean combustion and which can be produced locally. The fumigation of ethanol in diesel engines has been recognized as an effective alternative to improve efficiency and to reduce emissions. In this paper, the effects of a compression ignition engine using B7 and hydrous ethanol by fumigation method has been investigated. Hydrous ethanol was injected in the engine intake manifold by a port fuel injector, representing ethanol energy ratios from 11.5% to 52.3%. The results indicated a maximum decrease about 69% in smoke index, reduction in exhaust gas temperatures and reduction in both CO and CO2 emissions. The lowest CO emission found was 0,11% and CO2 emissions were 4.6% by volume. A maximum increase of 26.2% in thermal efficiency and 22.9% in exergy efficiency was observed. Nevertheless, an increase in HC emissions and specific fuel consumption was noted, achieving the maximum values of 121 ppm and 270.2 g/kWh, respectively. The results were satisfactory, confirming the potential to use ethanol fumigation method to improve thermal and exergy efficiency and reduce harmful gases.

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.