Cogeneration System Research Articles

Electricity and hydrogen production by integrating two kinds of fuel cells with copper chlorine thermo-chemical cycle

An innovative cogeneration system based on a solid oxide fuel cell (SOFC) and copper chlorine cycle is being investigated. Instead of directly making electricity by any thermodynamic cycle or thermoelectric generator, the waste heat from SOFC should be used to make hydrogen through the copper-chlorine cycle (Cu–Cl). A portable polymer exchange membrane fuel cell (PEMFC) has been suggested due to its compatibility with portable and non-portable applications. The obtained results reveal that increasing the current density of SOFC results in higher methane consumption, output power, overpotentials, and hydrogen production. Furthermore, temperature variation does not have as much influence on power generation and efficiency as current density, where the system efficiency, when operating at 0.7 A/cm2 and SOFC operating temperature of 900–1200 K, varies between 40.4 % and 46.3 %. Regarding the methane flow rate, as it increases, the output power increases as well, but the efficiency falls. The system's greatest power output is 677.5 kW and occurs at a methane flow rate of 2.13 mol/s, although the system efficiency is just 39.7 % at that point. Most importantly, SOFC generates nearly 65 % of the total power, while PEMFC generates around 35 %. Therefore, the percentage of additional power that PEMFC can produce is around 55 %.

Thermodynamic and optimization analysis of a fuel cell-based combined cooling, heating, and power system integrated with LNG-fueled chemical looping hydrogen generation

Chemical looping combustion technology is essential to achieve efficient decarbonized electricity generation for fossil-fueled power plants. However, the existing chemical looping hydrogen generation (CLHG)-driven cogeneration systems have complex refrigeration units and energy-consuming carbon capture. This study proposes a novel solid oxide fuel cell (SOFC)-based combined cooling, heating, and power (CCHP) system, which is integrated with the CLHG and fueled by a liquid natural gas (LNG) regasification process. The system is designed to enhance the overall performance by directly recovering LNG cold energy for cooling and liquefying the resulting CO2. The energy and exergy performance of the system under the baseline design case are evaluated. Subsequently, we discuss the impact of key design parameters on system performance and weigh between cooling/heating power and net power generation for the system dominated by the combined heat and power (CHP)/combined cooling and power (CCP) mode. Our findings reveal that the proposed system exhibits an electrical efficiency of 66.92 % and an exergy efficiency of 53.94 % under the baseline design case. The exergy loss ratio for condenser1 is identified as the highest among all components, accounting for 29.50 %. The constituent unit with the largest exergy loss contribution is the LNG regasification unit, followed by the SOFC unit, CLHG unit, transcritical CO2 cycle unit, and heating unit. More hydrogen needs to be replenished when fuel flow in the CLHG and fuel utilization in the SOFC are used to improve system performance. The optimal electrical and exergy efficiencies of the system predominantly designed in CCP mode surpass those in CHP mode by 4.27 % and 0.57 %, respectively. The results can guide potential applications of CLHG-based cogeneration systems.

Thermoeconomic Analysis of an Innovative Integrated System for Cogeneration of Liquid Hydrogen and Biomethane by a Cryogenic-Based Biogas Upgrading Cycle and Polymer Electrolyte Membrane Electrolysis

Thermoeconomic Analysis of an Innovative Integrated System for Cogeneration of Liquid Hydrogen and Biomethane by a Cryogenic-Based Biogas Upgrading Cycle and Polymer Electrolyte Membrane Electrolysis

3E analyses and multi-objective optimization of a liquid nitrogen wash based cogeneration system for electrical power and LNG production

A liquid nitrogen wash based novel system is proposed for electricity generation and LNG production. This system utilizes cold energy of methane rectification for power generation, and realizes the LNG production through methane recovery from exhaust gas. Effects of operational parameters on net generation capacity (NEG) and energy efficiency are studied. Exergy destruction/efficiency and exergy cost are obtained. Advanced exergy/exergo-economic analyses are conducted to clarify the improvement potential and improvement strategy. Finally, the optimal solutions are obtained in multi-objective optimization. Results show that propane could be used as the organic working medium and the maximum NEG is 675.95 kW and the energy efficiency is 19.34 %. As 88.8 % of the system investment cost is for the equipment, reduction on exergy destruction cost of equipment should be considered. Advanced analysis indicates that 27.27 % of the exergy destruction, 30.02 % of the exergy cost and 7.20 % of the investment cost can be avoided. The thermodynamic optimization shows that the highest energy efficiency is 67.26 %, the highest exergy efficiency is 76.95 % and the lowest exergy cost per unit is 28.45 $/GJ. The economic optimization shows that exergy efficiency is improved by 2.83 % and NEG is improved by 47.95 % when increasing the investment cost for 6.13 %.

Research on Energy Efficiency and Carbon Emission Evaluation Methods of cogeneration Technology under the Background of Carbon Neutrality

This article delves into the energy efficiency evaluation methods and carbon emission evaluation methods of cogeneration technology. In terms of energy efficiency evaluation, the concept of energy efficiency and commonly used energy efficiency indicators of cogeneration systems were introduced, such as total energy efficiency, power efficiency, thermal energy efficiency, and fuel utilization efficiency. In terms of carbon emission evaluation, the concept of carbon emissions and commonly used carbon emission indicators for cogeneration systems were analyzed, such as carbon emissions per unit of power generation, carbon emissions per unit of thermal energy, and total carbon emissions. For these evaluation methods, different implementation steps and calculation formulas were introduced in detail, and their application scenarios and advantages and disadvantages were illustrated with examples. These evaluation methods help to evaluate the performance and environmental impact of cogeneration systems, providing scientific basis for relevant decision-making.

Experimental study on a solar-powered cogeneration system for freshwater and electricity production.

In this study, a photovoltaic/thermal (PVT) collector and a stepped solar still system were constructed and integrated. The PVT collector was used to improve the performance of a stepped solar still device. Saltwater enters into the PV-T system and the temperature of the solar panel declines, and then ultimately the efficiency of the PV-T collector increases. After leaving the PVT collector, the temperature of the saltwater increased and was used as a pre-heater for further evaporation in the solar still, which ultimately caused an increase in its efficiency. The more tremendous temperature difference generated between the stepped surface and the glass increases efficiency and produces more freshwater. A flow rate of 7.5 L/hour of saline water was used to study the efficiency of the solar still device and the PVT collector. The value of productivity of solar still system with photovoltaic/thermal collector was 0.76kg/m2 more than that of conventional solar still. Despite the PVT collector, the daily efficiency of the solar still system increased to 34.8%, which shows an increase of 13.9% compared to the passive solar still device. Also, by cooling the PV-T system, the average electrical efficiency has increased from 13.1 to 13.7%. Production power reached 72.46 W from 65.96 W in two consecutive days at 11:15.

Thermo-economic analysis of an innovative multi-generation system based on ammonia synthesis

In this study, an innovative cogeneration system is developed and investigated which aim is to produce electrical power, ammonia, and hydrogen. A Kalina cycle is designed for electricity supply. An ammonia synthesis reactor and an electrolyzer are utilized for production of ammonia and hydrogen. The projected system is examined from economic and technical viewpoints. The analysis reveals that the ammonia production rate growth has been primarily influenced by the hydrogen to nitrogen molar ratio and pressure of reaction. For the system, the efficiencies of energy and exergy as well as the products' total unit cost achieve 50.47 %, 51.41 % as well as 638.3 $/GJ, each. The outcomes underscore that the rate of the destructed exergy is 89.797 MW for the system. Furthermore, 6.528 kg/s of ammonia and 6.438 kg/h of hydrogen are achievable. From a purely economic point of view, the comprehensive sensitivity examination deduces that 3 factors, namely the reaction pressure, hydrogen to nitrogen molar rate, and input hydrogen molar rate, do exercise a positive impact on the products’ total unit cost lessening. Lastly, results of thermodynamic sensitivity evaluation confirm that the offered system technical inefficiencies are correlated to the reaction temperature changes.

Optimal 4E evaluation of an innovative solar-wind cogeneration system for sustainable power and fresh water production based on integration of microbial desalination cell, humidification- dehumidification, and reverse osmosis desalination

Reliable freshwater production is vital for tackling two of the most critical challenges the world is facing today: climate change and sustainable development. Present work presents an innovative cogeneration system based on solar and wind energies for sustainable production of freshwater, power, and wastewater treatment. For freshwater production and wastewater treatment in this system, the integration of a microbial desalination cell with a humidification-dehumidification and reverse osmosis desalinations has been used. The mentioned systems provide their heat demand from solar energy, and when solar radiation is unable to provide this heat, a hydrogen internal combustion engine drive produces the required heat for the freshwater plant. Excess heat from the hydrogen internal combustion engine is fed into the organic Rankine cycle for more power generation in the whole system to reduce system waste heat and increase efficiency. PEM electrolyzer has been used to supply the hydrogen needed by the internal combustion engine, and this system uses wind turbines to supply the power demand. To evaluate the performance of the whole system, energy, exergy, exergeoeconomic, and exergoenvironmental (4E) analyses have been carried out. Finally, to improve the performance parameters of the system, multi-objective optimization using the Salp swarm algorithm has been used. Investigation of the results show that the proposed system can produce 720 kW of electricity and 5.36 m3/h of freshwater. The energy efficiency of the system is 22.09 %, and its overall cost rate and overall environmental impact rate are 540.33 $/hr and 17.37 Pt/h, respectively. Among the qualitative results obtained in this research, it is possible to mention the high exergy destruction, cost destruction, and environmental impact destruction of the internal combustion engine compared to other equipment used in the proposed system, and this point shows the need to improve this equipment, similar to previous researches. The five-objective optimization results of the proposed system showed that the performance parameters of the system, such as polygeneration energy efficiency, total cost rate, and total environmental impact rate, can be improved by 6.2 %, 1.44 %, and 0.52 %, respectively. The payback period of the proposed system in the optimal state is 6.95 years.

Thermodynamic Analysis of a Cogeneration System Combined with Heat, Cold, and Electricity Based on the Supercritical CO2 Power Cycle

The supercritical CO2 power cycle driven by solar as a new generation of solar thermal power generation technology has drawn significant attention worldwide. In this paper, a cogeneration system derived from a supercritical CO2 recompression Brayton cycle is proposed, by considering the recovery of waste heat from the turbine outlet. The absorption refrigeration cycle is powered by the medium-temperature waste heat from the turbine outlet, while the low-temperature waste heat is employed for heating, achieving the cascaded utilization of the heat from the turbine outlet. As for the proposed combined cooling, heating, and power (CCHP) system, a dynamic model was built and verified in MATLAB R2021b/Simulink. Under design conditions, values for the energy utilization factor (EUF) and exergy efficiency of the cogeneration system were obtained. Moreover, the thermodynamic performances of the system were investigated in variable cooling/heating load and irradiation conditions. Compared with the reference system, it is indicated that the energy utilization factor (EUF) and exergy efficiency are 84.7% and 64.8%, which are improved by 11.5% and 10.3%. The proposed supercritical CO2 CCHP system offers an effective solution for the efficient utilization of solar energy.

Environmental impacts analysis of Moroccan olive cake combustion in Stirling motor cogeneration system: Case study

Morocco is the world's 5th largest olive oil producer with 160,000 tons in 2020/2021 and the production of 1 L of olive oil generated approximately 5 kilos of waste olive cake, this type of waste is dangerous for the environment and especially for groundwater. To address this issue and take into account the thermal properties of olive waste, our project's goal is to produce power and heat by using solid olive waste in a Stirling cogeneration system. Therefore, the goal of this article is to examine by using CFD tools the environmental impacts of the Moroccan solid olive waste burning in a CHP (combined heat and power) unit. The idea is to integrate a smart renewable energy system based on olive cake and the Stirling motor to produce electricity in order to employ this electrical energy for water pumping in rural areas.The impact of the excessive air ratio on temperature profile and exhaust has been investigated and discussed. In addition, the pollutant species in air has been presented, and compared with guideline values given by some international organization for health and environment. Results show that the highest excess air ratio gives high temperatures with a homogeneous distribution around the Stirling motor hot heat exchanger, and minimum emissions of CO, CO2, NO, NO2 and NH3 that do not exceed the values set by WHO, OSHA, and NIOSH.

Thermoeconomic Modeling as a Tool for Internalizing Carbon Credits into Multiproduct System Analysis

In the context of emissions, carbon dioxide constitutes a predominant portion of greenhouse gases (GHGs), leading to the use of the term “carbon” interchangeably with these gases in climate-related discussions. The carbon market has emerged as a pivotal mechanism for emission regulation, allowing industries that struggle to meet emission reduction targets to acquire credits from those who have successfully curbed their emissions below stipulated levels. Thermoeconomics serves as a tool for analyzing multiproduct systems prevalent in diverse sectors, including sugarcane and alcohol mills, paper and pulp industries, steel mills, and cogeneration plants. These systems necessitate frameworks for equitable cost/emission allocation. This study is motivated by the need to expand the scope of thermoeconomic modeling to encompass expenses or revenues linked with the carbon market. By utilizing a cogeneration system as a representative case, this research aims to demonstrate how such modeling can facilitate the allocation of carbon market costs to final products. Moreover, it underscores the adaptability of this approach for internalizing other pertinent costs, encompassing expenses associated with environmental control devices, licenses, and permits. Although certain exergy disaggregation models depict an environmental component within diagrams, which is integral for addressing environmental burdens, even models without explicit environmental devices can effectively internalize carbon credits and allocate them to final products. The integration of carbon credits within thermoeconomic modeling introduces the capability to assess both the financial and environmental implications of emissions. This integration further incentivizes the reduction in GHGs and supports optimization endeavors concerning system design and operation. In summary, this study delves into the incorporation of carbon market dynamics into thermoeconomic modeling. It demonstrates the potential to allocate carbon-related costs, facilitates comprehensive cost analysis, encourages emission reduction, and provides a platform for enhancing system efficiency across industrial sectors.

Extended exergy analysis of a novel integrated absorptional cooling system design without utilization of generator for economical and robust provision of higher cooling demands

The focus of this study is on designing a novel system for the provision of high-capacity cooling and heating loads (4000 kW) with the utilization of absorption technology to increase economic viability and COP value of existing cooling plants via lower-grade waste heat sources (70 °C-90 °C). To achieve this aim, in the novel system, an integration including the LiBr-water solution based absorptional heat transformer (AHT), and absorptional cooling cycle (ACC), and flat plate solar collector (FPSC) systems was proposed. In the integration, the utilization of the generator in the cooling cycle was avoided with the interaction of the high-temperature LiBr-water solution (120 °C-150 °C) from the AHT system and ACC system evaporator. In this way, both the additional cost of the boiler and heat source and the enhancement of economic viability and COP value were achieved. Energy, economic, traditional, and extended exergy, sustainability, and environmental analyses were implemented in this novel system. The COP value for the cooling system was determined to be 3.10 from energy analysis. This result forms a significant indicator for achieving of the main focus of the current study with the proposed novel system. The annual heating and cooling duty generations with this novel system were computed as 52.37 GWh and 52.40 GWh, respectively. In the context of economically comparing the proposed system to other plants with similar scale that already exist, the initial overall expenditure, yearly operational expenses, and the time it takes to recover the investment for the proposed system were set at $4.56 million, $3.12 million, and 1.75 years, respectively. It is worth noting, though, that these figures fall within the range of $6–8 million, $5–7 million, and 5–10 years, respectively, for the currently operational plants. This result indicated that the proposed system provides a robust alternative to the existing cooling-heating cogeneration systems in terms of main output generation and is more economically viable. Also, the novel system gained annually US$3.89 million in energy costs. The conventional exergy analysis results were summarized by forming an exergy flow and loss diagram, namely, the Grassmann diagram. In addition, in this current study, the novel extended exergy flow diagram indicating extended exergy content components, energy carriers of the proposed system, and exergy product rate streams was also proposed and drawn for the proposed system.

"3E" Analysis and Working Fluid Selection for a Cogeneration System for Geothermal Large Temperature Difference Utilization.

Widespread utilization of geothermal energy as a clean energy source can reduce the use of fossil fuels and thereby protect the environment. Previous combined heat and power (CHP) systems using low-temperature geothermal heat as a heat source have limited utilization of geothermal heat. In this study, a cogeneration system based on organic Rankine cycle (ORC) and absorption heat exchanger (AHE) is designed. We analyzed the thermal efficiency, exergy efficiency, and economics of the proposed system utilizing 85 °C low-temperature geothermal heat, and the optimal operating fluid for this system is discussed. The results show that the optimal working fluid for the proposed system is R245fa. Using R245fa as the working fluid, the proposed system can achieve an exergy efficiency of 61.39%, when the heat source outlet temperature can be as low as 23 °C, while the proposed system can achieve the lowest LCOE of 0.082 ($/kW ·h) when using R22 as the working fluid.

Thermodynamic and techno-economic evaluation of a CAES based cogeneration system integrated with high-temperature thermal energy storage and ammonia absorption refrigeration

The development of compressed air energy storage (CAES) technology can ensure the safe and stable operation of the power system, promote the consumption of renewable energy and reduce carbon emissions. In order to improve the comprehensive performance of the CAES system and meet the diversified demand of energy, a cooling, heating and power cogeneration system based on compressed air energy storage with high temperature thermal energy storage and ammonia absorption refrigeration are developed in this study. The compression heat of the energy storage process and the exhaust waste heat of the energy release process are fully utilized in this system. Thermodynamic analysis, techno-economic evaluation and parametric analysis are conducted. The thermodynamic analysis results show that the proposed system achieve an ENE of 81.51 %, an EXE of 53.51% and an ESD of 7.08 kWh/m3 under the design condition. The economic analysis results indicate that the NPV, IRR and LCOE for a system life of 25 years are 489497 $, 32.1 % and 0.0953 $/kWh, with a DPP of 3.91 years. Sensitivity analysis results conclude that the outlet temperature of HTTES, and the maximum and minimum operating pressures are the key parameters affecting the system performance.

Techno-economic simulation and sensitivity analysis of modular cogeneration with organic rankine cycle and battery energy storage system for enhanced energy performance

This paper presents a comprehensive evaluation of the efficiency and cost implications of a modular cogeneration plant integrated with a Battery Energy Storage System (BESS) and an Organic Rankine Cycle (ORC) plant. The objective is to assess the performance of the system when waste heat recovery through the ORC cycle is added to the exhaust line and compare it with the original system. Techno-economic parameters were analyzed for two different configurations: one with the maximum BESS size and another with the maximum Primary Energy Savings (PES).The results demonstrate that the incorporation of the ORC plant yields several notable outcomes. While there is a slight increase in the Simple Payback Period (SPB) and Net Present Value (NPV) in both configurations, the magnitudes of these increases are relatively low. In contrast, the introduction of the ORC cycle leads to substantial reductions in carbon dioxide (CO2) emissions and significant improvements in Primary Energy Savings (PES). For the Max PES configuration, a remarkable 25% reduction in CO2 emissions and a substantial 22% improvement in PES were observed. To further investigate the system's response to varying economic conditions, a sensitivity analysis was performed. The analysis considered the effects of changes in the cost of battery, Combined Heat and Power (CHP) unit, ORC components, electricity, and fuel on the system's Simple Payback Period (SPB) and Net Present Value (NPV). The results revealed that the sensitivity of the Max PES configuration to economic parameters was higher compared to the Max BESS system.These findings highlight the considerable advantages of integrating an ORC plant into a cogeneration system with a BESS. The significant reduction in CO2 emissions and the noteworthy improvement in Primary Energy Savings (PES) outweigh the relatively minor negative impact on the Simple Payback Period (SPB) and Net Present Value (NPV). This integrated configuration demonstrates both environmental benefits and energy efficiency improvements. The results provide valuable insights for the design, optimization, and decision-making processes involved in the implementation of cogeneration systems with energy storage, promoting sustainable and cost-effective solutions.

Thermoeconomic analysis of a novel cogeneration system for cascade recovery of waste heat from exhaust flue gases

In low-grade waste heat recovery scenarios, an absorption refrigeration cycle (ARC) or organic Rankine cycle (ORC) can be used because of its widespread acceptance in combined cooling and power applications. This paper introduces a cogeneration configuration employing a cascade waste-heat recovery architecture (including an ARC, ORC, and intermediate heating loop) to harness waste heat from the flue gas of a gas turbine (GT). The results demonstrated that the first-law efficiency and total power generation were largely influenced by the ARC, whereas the second-law efficiency and total available energy were primarily affected by the ORC. When the ARC generation temperature difference and ORC evaporation temperature were adjusted, the first- and second-law efficiencies exhibited divergent trends, suggesting the absence of a unified strategy to enhance both efficiencies simultaneously in the current system. The system achieved its highest first-law efficiency of 54.84 % and maximum total power generation of 1866.10 kW at an ORC evaporation temperature of 145 °C and a heat-source inlet temperature of 160 °C. Furthermore, at an ORC evaporation temperature of 150 °C and a heat-source inlet temperature of 200 °C, the system reached its highest second-law efficiency of 34.57 % and maximum total available energy of 1233.3 kW. The case study revealed that the GT system (including air compressor, air preheater, combustion chamber, and gas turbine) accounted for the highest level of irreversibility, comprising 74 % of the overall system. Specifically, the combustion chamber in the GT system produced a significant irreversibility due to chemical reactions. Compared with traditional combined cooling and power systems, the proposed system can increase the first-law efficiency and lower the unit energy cost of the output.

Chemical looping combustion-driven cooling and power cogeneration system with LNG cold energy utilization: Exergoeconomic analysis and three-objective optimization

This study conducts thermodynamic and exergoeconomic analyses for a novel chemical looping combustion-driven cooling and power cogeneration system consisting of a supercritical carbon dioxide cycle, an air cycle, an organic Rankine cycle, and a liquid natural gas regasification process. Comprehensive parametric analyses are performed to investigate the impact of design variables on the proposed system's performance metrics, including electrical efficiency (ηel), exergy efficiency (ηex), and total product unit cost (cp,tot). A three-objective optimization is implemented to obtain the optimal system performance. The results underscore that the two reactors exhibit the highest exergy destruction of 17.29 MW, followed by the condenser's exergy destruction of 6.50 MW. The two reactors, expander, gas turbine, and condenser are the most important components within the system, and evaporator 1 and condenser need to be given more attention from exergoeconomic aspects. An optimum split ratio exists to maximize system performance by optimizing the conditions of the recycled stream into the fuel reactor. Optimization results reveal that ηel, ηex, and cp,tot cannot be simultaneously optimal and are 52.68%, 40.72%, and 27.43 $/GJ, respectively, after weighing. Moreover, the weighed performance of the proposed system outperforms those of similar systems despite employing components with lower design efficiencies.

Design, modelling, environmental, economic and performance analysis of parabolic trough solar collector (PTC) based cogeneration systems assisted by thermoelectric generators (TEGs)

Concentrating solar power systems (CSP) is a very efficient technology for clean and renewable energy production. It basically works on the principle of focusing the sun's rays with the help of a reflective surface. There are two types of CSP systems: point-focused and line-focused. Point-focused ones are parabolic dish collectors and solar towers. Line-focused ones are parabolic trough collectors (PTCs) and linear Fresnel reflectors. It is possible to reach focus temperatures over 1000 °C with point-focused CSPs. Line-focused CSP systems are used to obtain thermal and electrical energy at temperatures below 500 °C. Among CSP technologies, PTCs are widely preferred. While it can be used alone, it can also be used in combination with other power generation systems by creating hybrid systems. In this regard, hybrid PTC/TEG energy systems created with thermoelectric generators (TEGs) come to the fore. These systems have higher electrical and thermal efficiency values compared to traditional PTCs. In this study, CSP systems, PTCs, TEGs and hybrid solar energy systems-based PTCs were examined in detail. It is concluded from the study that the total thermal efficiency of PTC-TEG hybrid systems can be enhanced by up to %70 with respect to PTC systems.

Energy, exergy and exergo-economic analysis of a novel HT-PEMFC based cogeneration system integrated with plasma gasification of food waste

Landfill and incineration of food waste would result in a significant waste of resources. Plasma gasification, as a novel solid waste treatment technology with cleaner product, is suitable for this perishable kitchen waste with high water and oil content. In present research, a food waste plasma gasification driven HT-PEMFC cogeneration system is proposed. Based on the established models, a comprehensive study is conducted from the perspective of energy, exergy and exergo-economy. Effects of key operational parameters on critical performance indicators are investigated. Results show that current density imposes an obvious effect on the cogeneration efficiency, this efficiency is obtained as 0.523–0.457 at low current density varying from 0.1 to 0.4 A/cm2. Exergy analysis results indicate that the plasma gasifier and the stack have the largest exergy destructions, accounting for 62.1 % and 32.2 % of the total, respectively. Gasification temperature has a great effect on the system exergy efficiency which is 0.603–0.384 when this temperature increases from 1000 K to 1300 K. Current density also has an obvious effect on the exergo-economic performance, the exergy cost per unit is obtained as 46.1–51.8 $/GJ when current density varies from 0.2 to 0.4 A/cm2. The optimization results are obtained as cogeneration efficiency of 0.4636, exergy efficiency of 0.6125 and exergy cost per unit of 24.58 $/GJ. This research provides a novel solution for substantial treatment of food waste, and guidelines for sustainable development of efficient and clean utilization technology of municipal solid waste.

Evaluation of by-product-gas utilization options for carbon reduction at an integrated iron and steel mill

The comprehensive utilization of steel mill by-product gases is an important method for achieving climate goals. In this study, a comprehensive model is proposed for analyzing carbon-emission reduction strategies of by-product gases comprehensive utilization system at an integrated iron and steel mill. The model is used to explore carbon-emission reduction performance applying blast furnace with top-gas recycling (TGR-BF) and carbon capture and storage (CCS) applications, as well as consequent influence on steam and power cogeneration system (SPCS) operation. Carbon-emission intensity, total emission reduction and unit reduction cost are used to evaluate the carbon reduction result of by-product gases comprehensive utilization system. The results of the study indicate that the upgrade of SPCS can achieve an emission reduction of 311,200 tCO2, and the carbon-emission intensity of the power and heat supply can be reduced by 0.14 tCO2/104 kWh and 0.02 tCO2/GJ, respectively. After TGR-BF technology is applied, the total emission reduction peaks at the top-gas recovery rate of 6%, which is 85,100 tCO2. The unit reduction cost is also minimized at the top-gas recovery rate of 6%. Sensitivity analysis indicates that the reduction of power price significantly reduces the unit reduction cost.