The lack of access to electricity and clean water still affects a substantial proportion of rural areas worldwide, in particular the global south. This paper presents a sustainable polygeneration ...system that can provide electricity, heat, and drinking water by using agricultural residues in remote rural areas. This polygeneration system consists of a solid biomass-fueled Brayton-Stirling combined cycle system, a boiler, and an air-gap membrane distillation unit. Four different system operation modes were designed to examine the most ideal configurations for maximizing power output, overall efficiency, and/or clean water production, considering a polygeneration system designed for a rural village with daily demands of 13450 kWh electricity and 7.5 m3 drinking water. A thermodynamic analysis are employed to analyze and compare these modes, each operating under steady state conditions. The highest electricity output, up to 160 kW, while the highest clean water is up to 0.7 m3/h. The fuel consumption can reach 0.9 kWh/kg of solid fuel and provide up to 0.0045 m3 of freshwater. In addition, nonlinear multi-objective optimization is used to meet the power demands of typical day in rural areas by varying the polygeneration operation modes and turbine inlet temperature.
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•A solid bio-fuel based polygeneration system is developed for a rural village.•It consists of a Brayton-Stirling cycle, a boiler and a membrane distillation unit.•A thermodynamic study is conducted for comparing four designed operation modes.•Flexible operation can be achieved by combining the four operation modes.•The system can provide 1359 kWh electricity and 7.5 m3 clean water per day.
•A solid biomass based cogeneration system is developed for rural areas.•The system employs a Brayton-Stirling cycle, a boiler and a membrane distiller.•Four operation modes can be switched by ...controlling two three-way valves.•The system achieves up to 160 kW of electricity and 0.7 m3/h freshwater production.•The system can satisfy both rural power and water demands throughout the day.
Ensuring access to essential services, such as clean water and electricity, is a key challenge for achieving sustainable development goals in rural areas. This study proposes a novel Brayton-Stirling combined cycle-based cogeneration system for utilizing locally available biomass waste to generate both electricity and clean water. The system employs an externally fired gas turbine, a Stirling engine, and an air–gap membrane distiller. Four operation modes—parallel-powered, fully-fired, straightforward, and by-pass—were modeled for their efficiency and output. Four operation modes can be switched by two three-way valves. Sunflower husk, identified as the most effective biomass source, enabled the system to achieve up to 160 kW of electricity and 0.7 m3/h of freshwater. The electrical and exergy efficiencies of the system peaked in the parallel-power mode, offering a practical solution for enhancing rural sustainability. Moreover, the by-pass mode maximized water production, highlighting its effectiveness in addressing water scarcity along with energy generation. Through a case study, the cogeneration system has demonstrated its capability in satisfying both rural electricity and water demands throughout the day by controlling the combination of different operation modes and parameters. Therefore, it provides a promising solution for advancing rural electrification and water purification in rural areas.
The use of biomass as fuel might solve several technological and environmental issues and overcome certain challenges of sinter production. In particular, as revealed by comprehensive analyses, ...biomass can be used as fuel for iron ore sintering. In this study, we investigate the use of some raw and pyrolysis-processed biomass pellet types, namely wood, sunflower husks (SFH), and straw, for iron ore sintering. In the experiments, the pyrolysis temperature was set to 673, 873, 1073, and 1273 K, and the proportion of biomass in the fuel composition was set to 25%. It was established that the addition of biofuels to the sintering blend leads to an increase in the gas permeability of the sintered layer. The analysis of the complex characteristics of the sintering process and the sinter strength showed the high potential of wood and sunflower husk pellets pyrolyzed at 1073 and 873 K, respectively, for iron ore sintering. The analysis of the macrostructure of the sinter samples obtained using biomaterials revealed that with higher pyrolysis temperatures; the materials tend to have greater sizes and higher amounts of pores and cracks. The composition analyses of the resultant sinters revealed that with higher temperature, the FeO content of the sinters tends to increase.
This work presents comparative study on the combustion of biomass pellets (BP) with Bituminous coal (BC), and Xiao longtan lignite (XL) using thermogravimetric (TG) analysis. The results show that ...the combustion process of BP:BC can be divided into the release and combustion of volatile compounds, oxidation of BP char and combustion of BC char. While there are two stages for the blend of XL and BP, which are the combustion of volatile compounds and the char burning of BP and XL. With increasing BP ratio, the maximum combustion rate and combustion index increase, while the burnout temperature decreases, indicating the combustion performance of coal can be improved. In addition, interactions between BP and XL are more significant than that of BP and BC. The maximum deviations are found to be 30% BP with BC and 10% BP with XL. Reaction mechanisms are analysed using Coats–Redfern method. The first order model is found to be suitable for the first stage of biomass burn (stage 1) and coal combustion of BC:BP blends. Diffusion controlled model D3 and D4 are the most effective for the second stage of biomass burn and XL combustion, respectively. The minimum activation energies of biomass blending is obtained with a BP ratio of 30% for BC and 10% for XL.
•Comparative combustion between biomass and different coal was performed.•High temperature promotes the interaction between coal and biomass pellet.•Suitable combustion models in different stages for BCBP are First order and 1D diffusion.•Controlled diffusion model D3 and D4 are suitable for XLBP combustion.
Torrefaction in partially oxidative atmospheres is a non-traditional approach to the thermal pre-treatment of biomass. Despite the potential benefits arising from this compared to traditional ...torrefaction undertaken under costly inert atmospheres, the literature lacks data on the combustion and kinetic analyses of densified biomass torrefied under partially oxidative conditions comparable to those of (reusing) combustion flue gases. This paper, therefore, investigates the effects of partially oxidative atmosphere on the chemical functionality, combustion kinetics and thermodynamics of densified (Australian) woody biomass. Torrefaction was conducted at 250, 275, 300 °C for 30min under both inert and partially oxidative atmosphere (O2: 5 vol%, N2 balance). The kinetic parameters were derived from iso-conversional method over the entire conversion range. Results show that solid biofuel torrefied under partially oxidative atmospheres has superior chemical functionality (e.g., less oxygenates and higher thermal stability), but comparable physical properties to inert atmospheres. In addition, improved thermodynamic features and lower combustion activation energy for partially oxidative torrefied biomass was observed. Overall, the results suggest that the use of partially oxidative atmospheres for torrefaction not only produce a high quality solid biofuel but can also improve process efficiency by using waste heat and flue gases from other combustion processes to thermally pre-treat biomass.
•The use of biomass is increasingly important for clean energy generation from renewable sources.•An analysis of the current situation of the production of pellets (mixed biomass types) is ...provided.•The main emphasis is on the review of different combustion processes.•The evaluation of each individual stage of the combustion process is very important.
The need to generate thermal and electrical energy, global warming caused by increased emissions of greenhouse gases, rising fossil fuel prices and demand for energy independence, have created a new industry focused on energy production through the use of renewable sources. Among the different options, biomass is the third most important source for obtaining electricity, and is the main source for the production of thermal energy. However, problems related to the low density of the different types of biomass, and the difficulty of transportation and storage, have led to the need to find solid fuels with higher density and greater hardness, known as pellets and briquettes. This paper seeks to develop an analysis of the current situation of the production of pellets, mainly with mixed biomass types, and the possible uses they have, with the main emphasis on the review of different combustion processes.
Long transport distances and extended storage of biomass pellets especially in humid environments provide a suitable setting for enhanced degradation in the form of moisture sorption, cracking and ...attrition. We developed an optically transparent, low-cost and environmentally friendly coating to reduce moisture sorption and storage degradation of pellets. The developed coating is a hybrid sol–gel, based on tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) precursors. We coated two types of untreated and one type of torrefied wood pellets and stored them in a climate chamber during 1 month simulating a ship's hold, at a constant condition of 40 °C and 85% relative humidity. After 1 month of storage, the mean water contact angle increased by a factor of two compared to the uncoated ones. The lower wettability of the sol-gel coated untreated pellets compared to the non-coated torrefied pellets might provide an alternative to torrefaction.
•GPTMS/TEOS sol-gel is compatible with the heterogenous composition of biomass pellets.•The coating offers a sealing function reducing the mean apparent depth of the cracks.•After 1 month of storage, the coated pellets retained their hydrophobic behavior.
In Portugal, some species are now considered invasive by law and have proliferated in recent years. Among these, Acacia dealbata stands out. This work investigated the behavior of this species, in ...order to characterize and evaluate its potential as raw material for biomass pellets production, while controlling its proliferation. It was found that A. dealbata has a large capacity for raw material supply, as cutting 2 ha resulted in about 140 tons of biomass. Thus, the attribution of a market value for this material could result in a reduction in the area occupied by the invasive species, once the demand for it increases, causing a pressure over the resource. This pressure on the species must be duly followed by other control measures, such as reducing the population and mitigating its proliferation. Laboratory tests have shown that both the raw material and the finished product are similar to those obtained with other species normally used for biomass pellet production, such as Pinus pinaster and Eucalyptus globulus. Thus, it can be concluded that there is a high potential for this species in the production of biomass pellets for energy, and that this may be an important contribution to controlling the proliferation of this invasive species.
The torrefaction of biomass is a thermochemical process based on the de composition of hemicellulose, which is the dominant reaction, while the cellulose and lignin fractions remain almost ...unaffected. Torrefaction of biomass improves its physical properties like grindability, particle shape, size, and distribution, pelletability, and composition properties like moisture, carbon and hydrogen contents, and calorific value. The already higher energy density can be increased further by a pelletizing step after torrefaction. These improved properties make torrefied biomass particularly suitable for co-firing in power plants. Co-firing biomass with fossil fuels is one of the solutions to reduce the greenhouse gas emissions of existing power plants. Several studies on torrefaction of biomass for heat and power applications have been documented in the literature, which need to be reviewed and analyzed for further actions in the field, because significant gaps remain in the understanding of the biomass torrefaction process, which necessitate further study, mainly concerning the characterization of the torrefaction chemical reactions, investigation of equipment performance and design, and elucidation of supply chain impacts. This is the main objective of the present review study, which consists in three parts. The first part focuses on the mechanism of biomass torrefaction. It is followed by a review of biomass co-firing with coal. Finally, market opportunities for the process are discussed.
This study investigates the potential of cow dung, an animal manure, as a binder to enhance the physicochemical properties of the base pellet (a mixture of wheat straw and rice husk). In the first ...step, preliminary experiments were performed to select the best composition of wheat straw and rice husk for the base pellet. The selection was based on calorific value. Subsequently, the effect of operating parameters such as varying compositions of cow dung (0–100%), molasses concentration (0–100%) and drying time (12–48 h) was investigated. Thus, Central Composite Design using Response Surface Methodology was used to investigate the proximate analysis, calorific value, bulk density and durability of biomass pellets. The experimental results suggested that the addition of cow dung into the base pellet resulted in the increase of volatile matter, ash content, bulk density and durability of the base pellet. As a result, the maximum calorific value of 14.98 MJ/kg, moisture content of 3.37%, volatile matter of 45.49%, ash content of 31.38%, bulk density of 108990 kg/m3 and durability of 95% were obtained. However, optimization of operating parameters was performed to optimize the ash percentage. With the pellet composition of 8.5% (base pellet composition of 90% wheat straw and 10% rice husk), molasses concentration of 50% and drying time of 12 h, 52% reduction in ash content and 2.3% increase in calorific value were obtained at the cost of 38% reduction in the bulk density and insignificant reduction in durability of the produced pellet. Therefore, the use of waste material like cow dung as a binder can be considered as a sustainable approach to improve the physicochemical properties especially durability of biomass pellets. Thus, it can effectively be used to fulfill the energy and heating requirement of rural areas.
•Utilization of cow dung as binder in pellets composed of wheat straw and rice husk.•Production of pellets with maximum calorific value of 19.13 MJ/kg and 98% durability.•52% reduction of ash content by optimizing the % composition of rice husk.
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