Gas turbine steam injection and combined power cycles using fog inlet cooling and biomass fuel: A thermodynamic assessment

The results of energy and exergy analyses of two biomass integrated steam injection cycles and combined power cycles are reported. Fog cooling, steam injection and adding steam turbine cycles to gas turbine cycles can enhance the performance of power generation systems. Even with its lower heat value, biomass can be substituted for fossil fuels. The performances of the cycles are assessed under the same conditions. The assessments show that the combined cycle has a higher efficiency at lower values of compressor pressure ratio but the steam injection plant is advantageous at higher pressure ratio values. The steam injection plant has a higher net power under the same conditions, while the exergy loss rate is higher for the combined cycle at all pressure ratios. But the exergy destruction rate is higher for the steam injection cycle at lower compressor pressure ratios, and for the combined cycle at higher pressure ratios.     

The introduction and expansion of biomass use in Swedish district heating systems

District heating satisfies about 60% of the heat demand in Swedish buildings. Today, more than two thirds of the heat supply to the district heating systems is based on biomass and waste, and biomass alone accounts for about half of the heat supply. The purpose of this paper is to present the Swedish experiences of introducing and expanding the use of biomass in the district heating systems and to identify the main drivers behind this development. Our five research questions and the corresponding conclusions consider the driving forces from energy policy tools and local initiatives, the biomass prices, the established infrastructures in forestry and district heating, the technology paths for biomass conversion, and finally the future challenge of competing uses of biomass.     

Correlation for estimation of the chemical availability (exergy) from ultimate analysis of pyrolytic oils obtained from fast pyrolysis of biomass

The purpose of this study is to evaluate the chemical exergy (E^CH) of liquid products obtained from fast pyrolysis of biomass. I have calculated the chemical exergy values from a formula in literature and have developed a formula for estimating the chemical exergy of biomass from the higher heating value and their ultimate analysis values. The mean differences between these values range from –0.391% to 0.460%. The formula developed for estimating the chemical exergy of biomass from the higher heating value and their ultimate analyses had a correlation coefficient (R² = 0.9999), and the prediction of this formula is good. The goal is to identify desirable attributes that may serve as the basis for decision-making for future biofuel options. Studies on the pyrolytic oils showed that the oils obtained from chestnut cupulae and maple fruit can be used as a renewable fuel and chemical feedstock.     

Quality,productivity, energy and costs of woodchip produced by Cedrus deodara plantations: A case study in Italy

The main tree species planted for woodchips production for energy use are: poplar (Populus spp.), willow (Salix spp.), black locust (Robinia pseudoacacia L.) and eucalyptus (Eucalyptus spp.). Nevertheless, in the course of the years, other tree species were planted (i.e. Pinus strobus L.; Pauwlonia spp …). The scope of this study is the evaluation of energy and economic advantages, and quality of woodchip produced by a Cedrus deodara plantation situated in Italy.The plantation had a surface of 1.2 ha and trees were 14 years old.An amount of 363 t of fresh comminuted wood (about 300 t ha⁻¹) was produced by the plantation considered. A total time of 39.5 h (about 5 days) was required to transform all trees in woodchip. The moisture content of woodchip produced was 52%, while the average Low Heating Value (HHV) was 8.51 MJ kg⁻¹. In this study, economic (production cost = 93 € t⁻¹ DM) and energetic (output/input ratio = 74) evaluations of woodchip produced by Cedrus deodara plantations were positives. Nevertheless, the results obtained in this experimentation are close to the climate conditions and soil characteristics of Northwestern Italy.     

Physical properties of rice husk and bran briquettes under low pressure densification for rural applications

Agriculture generates large amount of by-products that could be used to produce energy and reduce the amount of fuelwood required to meet the daily cooking needs, especially in developing countries. Rice is a major crop grown in West Africa and rice husk is a by-product of the milling process. The goal of this study was to develop a low cost system to produce biomass briquettes from rice husks in the context of a rural village. A manual press generating a pressure of 4.2 MPa was developed and used. The influence of the briquette formulation (type of binder, binder content, water addition, and bran content) was studied. The binders investigated were cassava wastewater, rice dust, and okra stem gum. The physical properties (density, moisture content, calorific value, durability, and compressive strength) were tested to identify the briquettes with the highest quality, i.e. greatest physical integrity. The briquettes made with rice dust had the highest durability (91.9%) and compressive strength (2.54 kN), while the briquettes made with cassava starch wastewater had the greatest density (441.18 kg m⁻³). Water added to the rice husk before densification positively influenced the briquette quality while bran seemed to mostly increase the density, but not necessarily the briquette quality. The briquette formulation did not significantly influence the calorific value. With a higher heating value of 16.08 MJ kg⁻¹ dry basis, rice husk briquettes represent an interesting alternative to fuelwood.     

N2 explosive decompression pretreatment of biomass for lignocellulosic ethanol production

This paper presents a novel biomass pretreatment method that uses high pressured N₂ and temperature to break the hemicellulose and lignin seal around the cellulose macro fibrils in the cell walls of the lignocellulosic biomass in order to open up the biomass structure for more efficient enzymatic hydrolysis. In this method the biomass is exposed to a high pressure using N₂ gas, and temperature. Under pressure, cells of the lignocellulosic biomass are filled with a solution saturated with nitrogen. When the pressure is then suddenly released, the feedstock is exposed to an explosive decompression and the dissolved nitrogen is released from the solution. Sudden change in the volume breaks the cell walls and opens the biomass structure resulting in increased surface area of the substrate for enzymatic hydrolysis. No catalysts or chemicals were added in the process thereby, making it economically and environmentally attractive. In this research, a range of different pressures (1–60 bar) and temperatures (25–175 °C) were applied to barley straw to evaluate the efficiency of the pretreatment. The pretreatment was followed by enzymatic hydrolysis and fermentation. Resulting glucose and ethanol concentrations were measured and the yields were considered as an estimate for the most suitable set of pretreatment conditions. The results indicate that the highest glucose yield and hydrolysis efficiency were gained at 150 °C and 10–30 bars. The fermentation efficiency was lower at higher temperatures. Nonetheless, the highest ethanol yield was still gained at the same conditions.     

Biomass boiler conversion potential in the eastern United States

The U.S. is the world's leading consumer of primary energy. A large fraction of this energy is used in boiler installations to generate steam and hot water for heating applications. It is estimated there are total 163,000 industrial and commercial boilers in use in the United States of all sizes.This paper characterizes the commercial and industrial boilers in the 37 states of the Midwest, Northeast, and Southern regions of the U.S. in term of number of units, unit capacity, aggregate capacity, and fuel type. A methodology is developed for evaluating and ranking the potential for converting from existing fossil-fuel boilers to biomass boilers in these states.In total, 3495 oil and coal boiler units in industrial and commercial buildings, and 1067 major wood energy facilities in the 37 eastern states were identified. These represent a subset of existing and potential conversions from fossil fuels to woody biomass. Based on this sample and energy consumption data from the Energy Information Administration (EIA), we estimate that there are currently 31,776 oil, coal, and propane boiler units over 0.5 MMBtus/hour capacity in these 37 states, representing a total energy consumption of 1.7 quadrillion Btus, or roughly the equivalent of 287 million barrels of oil. Were these units all converted to woody biomass fuel, they would consume a total of 121 million dry tons of wood per year, about three times the most recent US DOE estimates of woody biomass availability in those regions. Since only the most economical conversions typically occur, the reality of woody biomass market availability combined with thermal fossil-fuel consumption patterns suggests that roughly one-third of all potential projects could be achieved under sustainable utilization of existing biomass feedstocks in the three regions.Analysis of the results indicates that a targeted response to wood-conversion initiatives will yield the most successful program of fossil-fuel replacement in thermal applications. A ranking index developed in this study through analysis of existing boiler installations and availability of wood feedstocks suggests that the top ten states in the eastern United States on which to focus future messaging, feasibility studies, and policy development for potential woody biomass conversions are:1. Maine, 2. Texas, 3. New York, 4. Florida, 5. Georgia, 6. Alabama, 7. South Carolina, 8. North Carolina, 9. Arkansas, 10. Pennsylvania.     

An overview of empty fruit bunch from oil palm as feedstock for bio-oil production

Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed.     

The role of biomass in US industrial interfuel substitution

The role of biomass in US industrial interfuel substitution in the industrial sector has typically been analyzed using data for the four traditional fuels of coal, oil, electricity and natural gas. However, the use of biomass as an industrial fuel in the US has grown, and now exceeds that of coal. Using data from 1960 to 2011, interfuel substitution in the US industrial sector is modeled with a dynamic linear logit model which includes biomass alongside the other four traditional fuels. Adding biomass to the model reduces somewhat the estimated own-price and cross-price elasticities for the other four fuels, while revealing that biomass and natural gas are substitute fuels. This implies that previous studies excluding biomass may have overestimated the potential for interfuel substitution, giving policy makers an inaccurate impression of the ability of carbon taxes or other environmental regulation to reduce greenhouse gas (GHG) emissions.     

Moving bed syngas conditioning: Modelling

This paper presents a modelling approach for simulating tars and particulate (dust) removal in a moving bed heat exchange filter (MBHEF) in order to satisfy gas requirements of end-use syngas applications: engines and turbines. The two-dimension, adiabatic, steady-state proposed model accounts for two-phase (gas and solid) and neglects conduction and mass diffusion. Tars condensation is modelled through representative tar class lumps: phenol (class 2), naphthalene (class 4), pyrene (class 5). The model also considers tar concentration influence on the tar dew point. The filtration model is taken from literature. A sensitivity analysis is performed varying the particle size and the superficial gas velocity. Maps of temperature and tars abatement efficiency are presented. The simulation results indicate the feasibility of the use a MBHEF as tars removal equipment benefiting its advantages against others gas-cleaning methods with acceptable pollutant removal efficiencies, ranging 88–94% for ranges studied. Results also point out low gas velocities (0.5-1 m/s) and high particle size (400–700 μm) for reducing operational costs in MBHEFs with compact size.