Externally Fired Gas Turbine Research Articles

Exergoeconomic Analysis and Optimization of a Biomass Integrated Gasification Combined Cycle Based on Externally Fired Gas Turbine, Steam Rankine Cycle, Organic Rankine Cycle, and Absorption Refrigeration Cycle.

Adopting biomass energy as an alternative to fossil fuels for electricity production presents a viable strategy to address the prevailing energy deficits and environmental concerns, although it faces challenges related to suboptimal energy efficiency levels. This study introduces a novel combined cooling and power (CCP) system, incorporating an externally fired gas turbine (EFGT), steam Rankine cycle (SRC), absorption refrigeration cycle (ARC), and organic Rankine cycle (ORC), aimed at boosting the efficiency of biomass integrated gasification combined cycle systems. Through the development of mathematical models, this research evaluates the system's performance from both thermodynamic and exergoeconomic perspectives. Results show that the system could achieve the thermal efficiency, exergy efficiency, and levelized cost of exergy (LCOE) of 70.67%, 39.13%, and 11.67 USD/GJ, respectively. The analysis identifies the combustion chamber of the EFGT as the component with the highest rate of exergy destruction. Further analysis on parameters indicates that improvements in thermodynamic performance are achievable with increased air compressor pressure ratio and gas turbine inlet temperature, or reduced pinch point temperature difference, while the LCOE can be minimized through adjustments in these parameters. Optimized operation conditions demonstrate a potential 5.7% reduction in LCOE at the expense of a 2.5% decrease in exergy efficiency when compared to the baseline scenario.

Thermal performance enhancement of a red-hot air furnace for a micro-scale externally fired gas turbine system

Externally-fired gas turbine (EFGT) has been considered an option in variable combined heat and power energy systems. The key elements in such systems are the high-temperature heat exchangers (HTHE), in which the working fluid (typically air) is heated by flue gas. Since both flows are separated, the solution is considered advantageous for utilization of biomass featuring high levels of particulate matter emissions. An increased interest in these devices has therefore been observed along with the development of small-scale CHP units utilizing locally available biomass. The effectiveness of HTHE, along with the inlet turbine temperature, appears to be one of the main factors influencing the efficiency of EFGT-based systems. Numerous studies on the HTHE designs have been carried out, basically focusing on the use of high-temperature resistant materials to provide safe conditions for long-term operation under elevated temperatures. There is a lack of research considering other methods to improve the effectiveness of the HTHE. The paper presents the analysis of thermal performance of the laboratory-scale 20 kW red-hot air furnace to demonstrate the HTHE effectiveness enhancement by adding water to airflow. The experimental results showed a significant increase (by almost 45%) in the heat exchanger effectiveness for the case of ∼10%wt. water addition. This is due to the enhanced heat capacity of a cooling medium and its absorption properties that results from the steam content. The proposed method for effectiveness increment appears to be beneficial to compensate for the low effectiveness of air-to-fumes tube HTHE.

Multi-objective optimization of biomass gasification based combined heat and power system employing molten carbonate fuel cell and externally fired gas turbine

Bioenergy is expected to play a critical role in a Net-Zero 2050 scenario. India ranks second in the world in terms of rice production. By-product rice husk, which is produced in large quantities, is currently burned and discarded by farmers. The primary objective of the research is to use rice husk as a fuel in an energy system that would otherwise be wasted. The rice husk might be better utilised to produce hydrogen-rich syngas, which could subsequently be used to generate clean electricity in fuel cell-based systems. Here, a novel combined heat and power system consisting of a biomass gasifier, molten carbonate fuel cell (MCFC), an externally fired gas turbine (EFGT), and a water heating facility has been developed. The proposed cogeneration system has undergone extensive thermodynamic and economic analyses. In addition, response surface methodology (RSM) was used for multiobjective optimization. An extensive investigation was conducted to determine how design factors influence exergy efficiency and the levelized unit cost of energy of the system.The results suggest the optimal design parameters are found at current density = 1015.25 A/m2, cell temperature = 700 ℃, and pressure ratio = 1.69. The optimization analysis shows that the cogeneration system has the maximum exergy efficiency of 41.15% and the lowest levelized unit cost of energy of 0.044 $/kWh.

A biomass-based polygeneration system for a historical building: A techno-economic and environmental analysis

Combined cooling, heating, and power systems (CCHP) are considered one of the most efficient energy systems since they have a less detrimental environmental impact, and therefore sustainable energy savings, and eventually less CO2 emissions. An even higher advantage is possible when a renewable energy fuel source (e.g., Biomass) is used. The proposed study presents the energy modeling of a 169 kWe capacity, biomass-based CCHP system retrofitted to a historical building, located in Perugia, Italy. Two well-known simulation software’s, ASPEN Plus and TRNSYS, are purposely integrated. In the first phase of the study, a wood biomass combustion-based externally fired gas turbine (EFGT) along with an Organic Rankine Cycle (ORC) system is modeled in Aspen Plus. In the later phase, a historical building “Sant’ Apollinare” model, and the remaining CCHP system are developed in TRNSYS. The transient system is modeled such that it fulfills the peak thermal energy demands of the retrofitted building. The main components of the system are a heat exchanger (HE), storage tanks (TK), a single-stage LiBr-H2O absorption chiller (ACH), and balance of plant (BOP) components. A heat exchanger recovers heat from the gas cycle, which is then utilized for running an ORC, heating and cooling of the end-user building, biomass drying, and domestic hot water (DHW) supply. A storage tank supplies direct heat to the end-user in winter and drives the ACH in summer. The results of the model provide data on the performance parameters of different components of the CCHP system such as temperature, power consumption, and energy profiles that allow evaluating the overall energy performance of the CCHP system. Finally, a feasibility analysis of the system is carried out on the basis of economic indexes such as simple pay back (SPB) period, net present value (NPV) and profitability index (PI), for two different case scenarios assumed for fuel (e.g., biomass) supply cost. The SPB is 2.93 years, when biomass is obtained for free. Whereas, if biomass is purchased from the market the SPB becomes 7.15 years. From an environmental perspective, the plant ensures a decrease of 632 tons of CO2 emissions annually.

Generating electricity from palm waste by gasification technique coupled with externally fired gas turbine: a case study

ABSTRACT Recently, renewable energy sources have become an encouraging solution to the availability and environmental problems arising from using fossil fuels for energy production. The article’s goal is to provide a reliable and doable path toward producing electricity from biomass by using palm waste (fronds, empty fruit bunches, and trunks). The system is simulated using Cycle-Tempo software. Waste was gasified at 800°C using a downdraft fixed-bed reactor to produce syngas. After that, a producer gas flow of around is sent to an externally fired gas turbine (EFGT), where it is promptly burned at atmospheric pressure to produce electricity. According to the simulation’s outcomes, palm fronds are the waste that worked best as a feedstock, and an estimated 390 kW of electric power could be generated by the externally fired gas turbine with a 19% electrical efficiency. The producer gas had a good molecular composition (H2 15.02%, CO 18.1%, CH4 1.25%, CO2 10.79%, H2O 8.17%, and N2 46.08%), a low heating value of up to (4.16 MJ/kg), a gasification efficiency of 77%, and a CHP efficiency of 61%. A comparison of the findings with previously published literature revealed that the proposed technology allows for the production of syngas with a satisfactory composition from palm fronds.

A sustainable optimal biomass waste-driven CCHP system to boost the nearly zero energy building concept

The aim of this work is focused on design of a sustainable tri-generation system driven by a biomass (MSW: municipal solid waste) externally-fired gas turbine cycle and utilizing a double-effect absorption chiller/heater. A robust framework based on energy, eco-exergy, and environmental analyses is developed to access the reliability of this proposal. An innovative optimization approach is then applied to reach the optimal sizing and operating conditions of the designed system. The novel optimization procedure is based on the combination of an Artificial Neural Network and multi-criteria Salp Swarm Algorithm. To make the outputs of the study applicable, a case study building is selected and the developed models are applied for satisfying its electrical, heating, and cooling demands. The building simulation is done with detailed real data and assumptions using by powerful energy architecture software. The results illustrated that the mass flow rate of MSW is the most effective variable on the system performance followed by the compressor pressure ratio. The eco-exergy analysis revealed that almost 40% and 23% of system’s total cost is respectively related to gas turbine and gasifier. At the optimal operation, the system could produce 541 kW of electricity, 2052 kW of heat, and 2650 kW of cold. The levelized cost of electricity generation is obtained as 0.083 $/kWh with environmental factor of 1.33 kgCO₂/kWh.

Optimization next to environmental analysis of harvesting waste heat from a biomass-driven externally-fired gas turbine cycle for sub-zero cooling and production of hydrogen, freshwater, and hot water

This research attempts to present a polygeneration system with five various products to recover waste heat of an externally-fired gas turbine cycle driven by biomass fuel. First, the waste heat of the gas turbine cycle is utilized in a supercritical Brayton cycle for more power generation. Then, it is employed as a heat source in an organic Rankine cycle and a hot water unit. The power generated in the organic Rankine cycle is used to produce freshwater in a reverse osmosis desalination system. Finally, liquefied natural gas acts as a heat sink for the supercritical Brayton cycle and organic Rankine cycle. The subsystem based on the liquefied natural gas is responsible for the production of cooling and required electricity of an electrolysis unit for hydrogen production. The tri-objective optimization of the designed system, using four supercritical gases in the supercritical Brayton cycle, reveals that the system has the best performance by using nitrogen. The system exergy efficiency is improved by 7.8 % points due to the integration of the subsystems with the gas turbine cycle. The proposed system can generate electricity, heating, and cooling relatively equivalent to 8126 kW, 2023 kW, and 1305 kW, respectively. The rates of hydrogen and freshwater production are equal to 14.28 kgh-1 and 45.81 kgs-1, correspondingly. In the context of environmental analysis, sustainability index and exergoenvironmental index were calculated as 2.365 and 0.6354.

Low-carbon biomass-fueled integrated system for power, methane and methanol production

A novel near zero-CO2 emission system based on gasification of municipal solid waste (MSW) is proposed and analyzed for waste-to-power and power-to-fuel purposes. The integrated system includes an externally fired gas turbine (EFGT), a molten carbonate fuel cell (MCFC), a Rankine cycle and an organic Rankine cycle (ORC), methane and methanol synthesis units and proton exchange membrane electrolyzer (PEME). Three different scenarios for synthetic fuel production (methane-only, methanol-only and dual-production) are investigated considering different operating loads of PEME, as green hydrogen route. For the case that 10% of produced power is consumed by PEME to generate the required hydrogen for methane and methanol synthesis, overall energy and exergy efficiencies are obtained 41 and 36%, respectively. In this case, the system consumes 1012 ton/yr of CO2 to produce 179 ton/yr methane and 393 ton/yr methanol with sustainability index of 1.57. The exergy analysis revealed that the employed EFGT unit is the main source of irreversibility with gasifier as the most exergy destructive component. In addition, the results of sensitivity analysis showed that increasing gas turbine inlet temperature improves both thermodynamic performance of the system and rate of synthetic fuel.

Exergo-economic analysis and multi-objective multi-verse optimization of a solar/biomass-based trigeneration system using externally-fired gas turbine, organic Rankine cycle and absorption refrigeration cycle

• A solar/biomass-based trigeneration system has been proposed. • The system comprises an EFGT, an ORC, and a LiBr/H 2 O absorbtion refrigeration cycle. • The system is studied from the energy, exergy, and exergo-economic perspective. • Solar thermal improves the thermodynamic efficiency of the system by about 10%. • MOMVO outperforms MOPSO and NSGA-II in solving multi-objective optimization problem. In the present work, an innovative configuration is proposed based on solar pre-heating concept and biomass direct-combustion for combined production of electricity, hot water and cooling load. The studied system consists of an externally fired gas turbine, a trans-critical organic Rankine cycle, and a Li-Br/H 2 O absorption refrigeration cycle. The proposed system is thoroughly analyzed from the energy, exergy, and exergo-economic viewpoint. The results of the exergo-economic analysis demonstrate that the energy and exergy efficiencies of the reference case are 55.56% and 20.38% and the product cost rate is 26.4 $/h. Comparing the thermodynamic results to the literature, it is proved that the proposed system generates a considerably higher amount of power, heating, and cooling load which results in an improvement of energy efficiency by about 10%. In further, the main design parameters of each cycle are parametrically assessed to gain a comprehensive understanding of the system behavior. Finally, a new multi-objective optimization algorithm called multi-objective multi-verse optimizer (MOMVO) is employed to maximize exergy efficiency and minimize the product cost rate of the system. Compared to the base case, TOPSIS implementation revealed that the optimal final solution of the Pareto-frontier found by the MOMVO has about 9% higher second law efficiency while the product cost rate is decreased by around 6%. This result proved the better performance of the MOMVO compared to other conventional evolutionary-based multi-objective optimzation algorithms.

Performance evaluation of a novel biomass-based hybrid energy system employing optimisation and multi-criteria decision-making techniques

This study proposes a novel hybrid system comprising four advanced technologies such as downdraft type biomass gasifier, solid oxide fuel cell (SOFC), externally fired gas turbine (EFGT), and Stirling engine (SE). The integrated system has been examined through exergetic, multi-objective optimisation and multi-criteria decision making (MCDM) techniques. Response surface methodology (RSM) has been applied to perform multi-objective optimisation of the proposed system. Regression models generated from the analysis of variance (ANOVA) tool are found to have a very high degree of accuracy for predicting net power, and exergy efficiency. Optimum values of the decision variables are selected from multi-objective optimisation. The optimum net power and the exergy efficiency of the system are estimated as 572.07 kW and 51.54%, respectively. Furthermore, MCDM analysis suggests that the rice husk as biomass fuel yields the best performances followed by wood and paper.

Thermo-economic assessment of a hybrid tri-generation system making simultaneous use of biomass and solar energy

In this work, a tri-generation system is proposed that relies on a biomass-gasification-based externally fired gas turbine (EFGT) generator and an array of solar flat-plate collectors. A LiBr-water-based absorption cooling (VAR) system utilizes the waste heat of a 100-kW power generator as well as solar thermal energy of a 200 sq. m. solar collector to run a vegetable cold store of 200 metric ton capacity. A domestic water-heating system is also integrated with the unit that recovers low-temperature thermal energy to produce 150 tons of hot water daily. The power generator shows its maximum electrical efficiency of 27.5% at 1100 °C turbine inlet temperature and 10 pressure ratio. The maximum efficiency of solar collector is found to be 48%. The overall energetic efficiency of the tri-generation system varies in the range of 59 to 76%, while the overall exergetic efficiency varies in the range of 19 to 26.5%. The components of EFGT generator show high exergetic efficiencies, about 93% for air compressor and about 90% for GT, whereas the solar thermal system shows the poor exergetic performance of about 17%. Based on economic analysis of the proposed plant, the effective price of electricity is estimated as 0.068 USD/kWh without any subsidy, but considering 50% capital subsidy the price is estimated as 0.04 USD/kWh. The discounted payback period is found to be 10.8 years without any capital subsidy, but when 50% subsidy is considered, the payback period is reduced to 5 years.

Design and Performance Analysis of a Biomass Fueled Mono-Tube Boiler for Humid Air Turbine Cycle

Externally fired gas turbine (EFGT) is one of the few power generation configurations capable of utilizing biomass in its solid form without any additional equipment to convert it to liquid or gas. Due to its high thermal output capability for drying applications, EFGT is one of the most suitable configurations for the off-grid rural areas in Malaysia with abundant biomass waste and high demand of heat for crops drying. The main downside of EFGT is the necessity for high temperature heat exchanger which compromises the system feasibility due to the high cost and other technical challenges. This can be eliminated by the addition of steam in a configuration known as humid air turbine (HAT), thus, limiting the required temperature and allowing for the use of common low-temperature heat exchanger types. Several mono-tube steam boiler designs were compared to fulfil the required steam flow rate of 2 kg/min for the available EFGT system. Counter-flow design was found to be more suitable with its higher efficiency. The boiler was characterized experimentally at output steam flow rate range of 0.4-2 kg/min using off-cut waste wood from furniture industry. Maximum achieved boiler efficiency and specific fuel consumption were 73% and 0.29 kg/kWh, respectively.

Multi-objective optimization and exergo-economic assessment of a solar-biomass multi-generation system based on externally-fired gas turbine, steam and organic Rankine cycle, absorption chiller and multi-effect desalination

In the present work, a novel multi-generation scheme based on solar energy and biomass direct-firing technology for simultaneous production of power, cooling, heating, and freshwater is proposed. The system comprises externally fired gas turbine, steam and organic Rankine cycle, single-effect absorption chiller, and multi-effect desalination. The proposed scheme also has the potential to burn natural gas as secondary fuel when biomass is not available. In further, a comprehensive study of the thermodynamic and economic behavior of the proposed system with consideration of both fuels (bagasse and natural gas) is performed. Based on energy and exergy analysis for the base case condition (Pratio = 4.84, T14 = 875 °c), the system with bagasse can achieve an exergy efficiency of 21.48% while total product cost rate is 77.31 $/h. Moreover, a parametric study is performed to achieve a better understanding of the system performance with respect to different cycle parameters. Finally, two different multi-objective optimization problems that maximize second law efficiency and net power output while minimizing total product cost rate are solved, and the Pareto fronts are illustrated. TOPSIS implementation reveals that the optimum solution has 0.2% higher exergy efficiency while total cost rate is lowered by 10% compared to the base case results.

Tri-generation biomass system based on externally fired gas turbine, organic rankine cycle and absorption chiller

This work focuses on the modelling of a tri-generation system for converting biomass into electrical, cooling and heat power. This target is achieved by direct burning of biomass using a combustor chamber, at atmospheric pressure, connected with an externally fired gas turbine (EFGT), an organic Rankine cycle (ORC) and absorption cooling system. The used feedstock is sugarcane bagasse which is available in various areas of Upper Egypt, especially in Qena and Aswan. For ORC system, several working fluids (cyclohexane, benzene, toluene, and R113) have been studied to analyze the optimum fluid that corresponds to the entire system. The selection of more suitable ORC working fluid is mainly depends on the temperature difference between the heat source and its boiling point. Based on the simulation results, toluene is the most appropriate working fluid for combined cooling, heat and power (CCHP) applications. The net electric power is 177.56 kW (142.92 kW from EFGT and 34.64 kW from ORC), net electrical efficiency is 24.2%, cooling capacity is 38.50 kW and CCHP efficiency is 43.50%. The biomass consumption at the optimal operating conditions is 144 kg/h.

Design optimization and experimental analysis of externally fired gas turbine system fuelled by biomass

Gas turbines provide large portion of the global power generation as well as the carbon footprint. Utilizing biomass in gas turbines in externally fired gas turbine (EFGT) configuration is a promising option for the reduction of greenhouse emissions. However, only few experimental EFGT studies have been reported due to the technical difficulties and high cost associated with the development of high temperature heat exchanger for the system. An experimental turbocharger-based EFGT test-rig was developed in previous study. However, the low turbine inlet temperature (TIT) below 700 °C provided by the heat exchanger was not adequate for the turbine start-up. In this study, the heat exchanger was redesigned using annular tube configuration and eight tube sizes were compared. The optimum heat exchanger design elevated TIT up to nearly 900 °C and the turbine was able to operate at self-sustaining mode in the pressure range of 0.2–0.25 bar.

Fixed bed gasification of corn stover biomass fuel: Egypt as a case study

AbstractThis paper focuses on the optimal performance of a small tri‐generation power, heat, and cooling plant, which uses corn stover as the feedstock. First, 100 kg h−1 of the corn stover is converted into syngas by the gasification process, using a downdraft fixed‐bed reactor at gasification temperatures reaching 995 °C and with an oxidant–fuel ratio of 1.65. About 243.18 kg h−1 of product gas mass flow with 4.766 MJ kg−1 of calorific value is supplied to an externally fired gas turbine (EFGT) to convert this fuel to electrical power. It is estimated that the EFGT is capable of producing 70.57 kW of electrical power with a high‐temperature heat exchanger efficiency of 75% and a pressure ratio of 4.84 at a turbine inlet temperature of 875 °C. The absorption refrigeration system is used for the cooling process. The cooling power (ℚ eva ) of the absorption cooling system is 130.92 kW with a cooling tower temperature of 15 °C and a system performance coefficient (PC) of 0.6. The recovered heat flow to the generator ( ℚ gen ) and the refrigerating heat flow are 82.62 kWth and 48.83 kWref , respectively, with a circulation ratio of 4.07. For the whole system (gasifier, EFGT, and absorption cooling), the gross electrical efficiency (ηnetEL ) is 21.78% and the net thermal efficiency (ηth ) is 47.43% with a system cooling‐to‐power ratio (CPR) of 1.88. The simulation of this system was conducted using Cycle‐Tempo software. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

A Distributed Generation Hybrid System for Electric Energy Boosting Fueled with Olive Industry Wastes

This paper presents the theoretical model and the simulation of a cutting edge hybrid power system composed of an externally-fired gas turbine (EFGT) coupled with an organic Rankine cycle (ORC) as a bottoming unit for the maximization of electrical power. The power plant is fed with different biomass sources from olive industry wastes (pruning, dry pomace, stones, leaves and twigs), providing more than 550 kW of electric power and a net electrical efficiency of 26.0%. These wastes were burnt directly at atmospheric pressure in an EFGT, producing 400 kW of electric power and exhaust gases at 300 °C. Ten suitable ORC working fluids have been studied to maximize the electric power generation: cyclohexane, isohexane, pentane, isopentane, neopentane, R113, R245fa, R365mfc, R1233zd and methanol. The best fluid was R1233zd, reaching 152.4 kW and 22.1% of ORC thermal efficiency; as drawback, however, R1233zd was not suitable for Combined Heat and Power CHP applications due its lower condensation temperature. Thus, despite R113 gave minor electricity production (137.5 kW) this allowed to generate additional thermal power (506.8 kW) in the way of hot water at 45 °C.

Hybrid solar-biomass combined Brayton/organic Rankine-cycle plants integrated with thermal storage: Techno-economic feasibility in selected Mediterranean areas

This paper presents a thermodynamic analysis and techno-economic assessment of a novel hybrid solar-biomass power-generation system configuration composed of an externally fired gas-turbine (EFGT) fuelled by biomass (wood chips) and a bottoming organic Rankine cycle (ORC) plant. The main novelty is related to the heat recovery from the exhaust gases of the EFGT via thermal energy storage (TES), and integration of heat from a parabolic-trough collectors (PTCs) field with molten salts as a heat-transfer fluid (HTF). The presence of a TES between the topping and bottoming cycles facilitates the flexible operation of the system, allows the system to compensate for solar energy input fluctuations, and increases capacity factor and dispatchability. A TES with two molten salt tanks (one cold at 200 °C and one hot at 370 °C) is chosen. The selected bottoming ORC is a superheated recuperative cycle suitable for heat conversion in the operating temperature range of the TES. The whole system is modelled by means of a Python-based software code, and three locations in the Mediterranean area are assumed in order to perform energy-yield analyses: Marseille in France, Priolo Gargallo in Italy and Rabat in Morocco. In each case, the thermal storage that minimizes the levelized cost of energy (LCE) is selected on the basis of the estimated solar radiation and CSP size. The results of the thermodynamic simulations, capital and operational costs assessments and subsidies (feed-in tariffs for biomass and solar electricity available in the Italian framework), allow estimating the global energy conversion efficiency and the investment profitability in the three locations. Sensitivity analyses of the biomass costs, size of PTCs, feed-in tariff and share of cogenerated heat delivered to the load are also performed. The results show that the high investment costs of the CSP section in the proposed size range and hybridization configuration allow investment profitability only in the presence of a dedicated subsidy framework such as the one available in the Italian energy market. In particular, the LCE of the proposed system is around 140 Eur/MWh (with the option to discharge the cogenerated heat) and the IRR is around 15%, based on the Italian electricity subsidy tariffs. The recovery of otherwise discharged heat to match thermal energy demand can significantly increase the investment profitability and compensate the high investment costs of the proposed technology.

Electricity generation from pyrolysis gas produced in charcoal manufacture: Technical and economic analysis

Abstract Brazilian steel industry based on charcoal is unique in the world, making Brazil the largest world charcoal producer and the only one that produces green pig iron in large scale, a low-carbon and economic option to the traditional pig iron produced from coal coke. The renewable charcoal originates from the slow pyrolysis of eucalyptus wood produced in high productivity reforestation farms thought traditional batch reactors. Unfortunately, the state-of-the-art of charcoal making in Brazil do not comprise the pyrolysis gases utilization, wasting more than 30% of wood energy decreasing air quality and producing environmental and social impacts. Therefore, in this sense, the goal of this work is to evaluate the possibility to recovery this energy to produce electricity, and issues the topics related to the use of a very lean fuel, with flammability problems, which varies its composition over time, and the lack of water to be used as cooling mean for the thermodynamic cycles in the eucalyptus farms. The gases Lower Flammability Limit (LFL) was analyzed by the Calculated Adiabatic Flame Temperature (CAFT) method showing that in the first half of pyrolysis, the gases are generally under the LFL line, what could be solved by the gases pre-heating or mixing with richer fuel produced by kilns in advanced carbonization stage. Results showed an average gas Lower Heating Value (LHV) of 1323 kJ/kg. To overcome gas production instability a cluster system of 120 rectangular carbonization kilns working in synchrony was accessed through a computational tool, where it was found a minimum thermal power available of 57.5 MWth or 25.6% of initial wood energy content. Three energy conversion technologies were evaluated: the Steam Rankine Cycle (SRC), the Externally Fired Gas Turbine (EFGT) and the Organic Rankine Cycle (ORC). In this work, it was found that the efficiency of the SRC, EFGT and ORC conversion technologies are 24.0%, 19.3% and 23.7%, respectively. An economic analysis indicated the SRC as the most viable technology with a potential to generate 0.93 MWhel per ton of charcoal produced. Brazil has as estimated energy loss of 2.5 Mtoe (million tonne of oil equivalent) annually in the form of carbonization gases, which could be used to produce up to 5644 GWhel of electricity and reduce the Greenhouse Gases (GHG) emissions up to 15 Mton CO2–eq.

Biomass gasification coupled to an EFGT-ORC combined system to maximize the electrical energy generation: A case applied to the olive oil industry

This research presents the modelling and simulation of an innovative small-scale power system composed of a downdraft gasifier, an externally fired gas turbine (EFGT) and an Organic Rankine Cycle (ORC) as a bottoming unit for increasing the electrical energy generation. Olive tree pruning (217 kg/h) was the biomass used, producing more than 200 kWe and an electrical efficiency of 20.7%. The producer gas achieved suitable mole composition (H2: 14.8%, CO: 19.5%, CH4: 2.2%, CO2: 9.3%, H2O: 12.0% and N2: 41.5%), lower calorific value (4.53 MJ/kg) and gasification efficiency (89%). The hot producer gas was burnt directly at atmospheric pressure in an EFGT, producing 150 kWe and exhaust gases at 290 °C. Five ORC working fluids were studied to maximize the electricity generation: isopentane, benzene, cyclohexane, R113, R245fa. Isopentane was the most suitable fluid, reaching 57.1 kWe and 20.45% of ORC thermal efficiency. On the other hand, despite R113 gave minor electricity production (49.1 kWe), this allowed to generate thermal power for CHP applications.