Analysis and Prospect of Waste Heat Utilization from Blast Furnace Slag Flushing

Estimating the residual heat of blast furnace slag flushing in China,classifying and introducing the current proposed methods of slag flushing waste heat utilization,and listing existing cases.In order to better save energy and water in the slag flushing process of blast furnaces,an ideal comprehensive cascade utilization system scheme for annual recovery of waste heat is proposed.Based on the measured waste heat data of a steel plant,design calculations are carried out to further analyze the economic feasibility of the new scheme and provide reference for its promotion and application.

Diesel generator exhaust heat recovery fully-coupled with intake air heating for off-grid mining operations:An experimental,numerical,and analytical evaluation

The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation.This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine.An integrative approach comprising analytical,numerical,and experimental assessment has been adapted.The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system.The effect of working fluid variation has been examined by the numerical analysis and the possible improvement has been identified.Experimental investigations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed.Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient,and sustainable mining practices through nearly 70%reduction in fossil fuel consumption for heating intentions.

A Comprehensive Study of a Low-Grade Heat-Driven Cooling and Power System Based on Heat Current Method

Combined cooling and power(CCP)system driven by low-grade heat is promising for improving energy efficiency.This work proposes a CCP system that integrates a regenerative organic Rankine cycle(RORC)and an absorption chiller on both driving and cooling fluid sides.The system is modeled by using the heat current method to fully consider nonlinear heat transfer and heat-work conversion constraints and resolve its behavior accurately.The off-design system simulation is performed next,showing that the fluid inlet temperatures and flow rates of cooling water as well as RORC working fluid strongly affect system performance.The off-design operation even becomes infeasible when parameters deviate from nominal values largely due to limited heat transfer capability of components,highlighting the importance of considering heat transfer constraints via heat current method.Design optimization aiming to minimize the total thermal conductance is also conducted.RORC efficiency increases by 7.9%and decreases by 12.4%after optimization,with the hot fluid inlet temperature increase from 373.15 to 403.15 K and mass flow rate ranges from 10 to 30 kg/s,emphasizing the necessity of balancing system cost and performance.

The Pressure Gradient Elastic Wave： Energy Transfer Process for Compressible Fluids with Pressure Gradient

The temperature separation was discovered inside the short vortex chamber （H/D = 0.18）. Experiments revealed that the highest temperature of the periphery was 465 ℃, and the lowest temperature of the central zone was -45 ℃ （the compressed air was pumped into the chamber at room temperature）. The objective of this paper is to proof that this temperature separation effect cannot be explained by conventional heat transfer processes. To explain this phenomenon, the concept of PGEW （Pressure Gradient Elastic Waves） is proposed. PGEW are kind of elastic waves, which operate in compressible fluids with pressure gradients and density fluctuations. The result of PGEW propagation is a heat transfer from area of low pressure to high pressure zone. The physical model of a gas in a strong field of mass forces is proposed to substantiate the PGEW existence. This physical model is intended for the construction of a theory of PGEW. Understanding the processes associated with the PGEW permits the possibility of creating new devices for energy saving and low potential heat utilization, which have unique properties.

Performance Analysis of a Combined Absorption Refrigeration-Liquid Desiccant Dehumidification THIC System Driven by Low-Grade Heat Source

Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas,and it is difficult to achieve simultaneous control of temperature and humidity.A combined absorption refrigeration(AR)and liquid desiccant dehumidification(LDD)air-conditioning system based on cascade utilization of low-grade heat source is proposed.The system can realize independent control of temperature and humidity and carry out profound recovery of low-grade heat sources.Under the design conditions,the heat utilization rate C reaches 21.05%,which is 2.73 times that of the conventional absorption refrigeration reference system.A parametric sensitivity analysis is performed to optimize the system.The C increases from 9.79%to 18.55%and the coefficient of performance C O P t increases from 0.33 to 0.35 with an increase in chilled water temperature from 7°C to 15°C.With an increase in regenerant solution temperature from 60°C to 70°C,the C achieves the optimal value of 21.05%at 68°C.C decreases from 21.05%to 15.05%as the concentration of the regenerant solution increases from 36%to 40%.Under variable environmental temperature and humidity,the C the proposed system changes within a small range and stays much higher than that of the reference system with the same quality heat source,which indicates that the proposed system has a better adaptability to changing environmental parameters.

Performance Analysis of an Integrated Supercritical CO_(2) Recompression/Absorption Refrigeration/Kalina Cycle Driven by Medium-Temperature Waste Heat

A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).

Comprehensive review of models and methods used for heat recovery from composting process

The large amount of heat produced from solid waste composting has stimulated great interest in heat recovery and utilization.This paper reviews the advances in composting heat recovery researches in the last decade.Some experimental results and theoretical studies on composting heat utilization are summarized.The results indicate a great potential for utilization of heat produced by the composting process.Common problems experienced by current methods are how to realize the maximum heat recovery without negatively impacting compost quality and the economics of heat recovery methods.Further advancement of these methods is currently receiving comprehensive interests,both academically and commercially.

A simultaneous approach for integration of thermal energy storages in industrial processes using multiperiod heat integration

In times of increasing global warming,enormous efforts are required to rapidly reduce greenhouse gas(GHG)emissions.Due to the EU’s target of climate neutrality by 2050 and the even more ambitious goal of becoming climate-neutral in Germany by 2045,it is necessary to systematically increase energy efficiency and decarbonize the industrial heat sector.The methods of heat integration can be used to exploit existing potentials for waste heat utilization and to integrate renewable technologies for heating and cooling.By using a non-stationary,multiperiod approach,additional energy savings can be achieved by integrating a thermal energy storage(TES)that enables heat transportation over time.This paper presents a simultaneous approach for thermal energy storage integration into multiperiod heat integration problems.The approach can be used to minimize energy demand,costs and CO 2 emissions and is demonstrated in two case studies.In case study 1,it is shown that the presented approach is capable of integrating a TES properly into a simple multiperiod heat integration problem with two periods.In case study 2,a simplified example from a cosmetics manufactory is investigated.The total utility demand can be reduced by up to 44.3%due to TES integration and the energetic optimal storage size can be determined as 125 m 3.The savings are strongly dependent on the constellation of heat flows between the periods,on the temperature levels and on the storage size.Significant reductions of energy demand,costs and CO 2 emissions can be achieved with TES being properly integrated into a suitable operating environment.

Nanofluidic osmotic power generation from CO_(2) with cellulose membranes

The diffusion of chemical species down concentration gradient is a ubiquitous phenomenon that releases Gibbs free energy.Nanofluidic materials have shown great promise in harvesting the energy from ionic diffusion via the reverse electrodialysis process.In principle,any chemicals that can be converted to ions can be used for nanofluidic power generation.In this work,we demonstrate the power generation from the diffusion of CO_(2) into air using nanofluidic cellulose membranes.By dissolving CO_(2) in water,a power density of 87 mW/m^(2) can be achieved.Using monoethanolamine solutions to dissolve CO_(2),the power density can be increased to 2.6 W/m^(2).We further demonstrate that the waste heat released in industrial and carbon capture processes,can be simultaneously harvested with our nanofluidic membranes,increasing the power density up to 16 W/m^(2) under a temperature difference of 30°C.Therefore,our work should expand the application scope of nanofluidic osmotic power generation and contribute to carbon utilization and capture technologies.