Industrial Waste Heat Utilization Research Articles

Industrial Waste Heat Utilization in the European Union—An Engineering-Centric Review

The efficient utilization of waste heat from industrial processes can provide a significant source of energy savings for production plants, as well as be a driver of sustainable operations and the abatement of emissions. Industrial waste heat usually is contained in liquid or gaseous outlet streams. Although the possible ways to utilize waste heat are discussed in a wide variety of papers, these either provide only a general overview of utilization options and opportunities or focus on a narrow range of industrial processes. The aim of the present paper is to discuss the practical aspects of waste heat utilization in the European Union so that the reader can gain perspective on (i) the thermal classification of waste heat, (ii) liquid and gaseous waste streams and their typical temperatures for industrial use cases, (iii) the technical, economic, physical, and environmental aspects barring full utilization of the available waste heat, (iv) waste heat sources in various industries, and (v) standardized equipment and technologies applicable to industrial waste heat utilization, including their advantages, disadvantages, and weak points.

Research progress and applications of transcritical carbon dioxide heat pumps: A review

Heat pump technology is an energy-saving technology that can efficiently utilize low-grade energy. It has broad application prospects in building heating, industrial waste heat utilization, new energy and other fields. However, the refrigerants used in traditional heat pump systems have serious negative impacts on the environment, and there is an urgent need to find a safe, environmentally friendly, and efficient alternative refrigerant. As a natural refrigerant, CO2 has good physical and chemical properties and is very suitable as a working fluid in transcritical cycles, showing great advantages in the field of heat pump technology. At present, research on CO2 heat pumps has made certain progress, but there are few reviews of the research status and development trends of CO2 heat pumps in different applications. Therefore, this article systematically summarizes the latest research results of transcritical CO2 heat pumps in different application fields, pointing out the difficulties such as high pressure and low operating efficiency in system design and operation. It also summarizes the latest optimization research on system components, cycle structure, mixed refrigerants and control strategies. The results show that each optimization method can significantly improve system performance, among which mixed refrigerant is the simplest optimization method. Finally, the outlook for CO2 heat pump technology is put forward. With policy support and technological advancement, more comprehensive, energy-saving, and intelligent CO2 heat pump technology will continue to develop and innovate.

Off-design condition optimization of organic Rankine cycle based on genetic algorithm

Organic Rankine cycle (ORC) has been considered as one of the most promising technologies in industrial waste heat utilization and power generation. During the actual operation of ORC system, due to the fluctuation of cooling and heat sources, the system operates under off-design conditions in most cases. In this paper, thermodynamic model, heat transfer process description and power equipment model are established to evaluate the operating parameters of ORC for the off-design conditions. Evaporation temperature and condensation temperature are taken as independent parameters for the operation of ORC system. Genetic algorithm is adopted to optimize the independent parameters under the maximum net output power. The results show that the effect of optimizing independent parameters is to make the working fluid at the outlet of the preheater as close as possible to a saturated liquid state, and the working fluid at the inlet of the screw expander should be in a saturated gas state. With the optimal power output increasing by 19.1% for every 5 °C increase in hot water inlet temperature, 9.2% for every 20 kg/s increase in hot water mass flow rate, and 3.9% for every 1 °C decrease in cooling water temperature. The optimization method of off-design operating conditions has good system performance and good engineering application prospects.

Effect of the vacancy close to heat exchange wall on the heat transfer performance of the solid particles steam generator using waste heat in a methanol steam reforming hydrogen production system

With the massive consumption of fossil fuels and it resulted in significant carbon emissions, it is urgent to find an alternative clean energy source. Hydrogen has been regarded as one of the most promising energy candidates for the next generation. It is a great approach that methane steam reforming for hydrogen production by rational utilization of industrial waste heat, which significantly minimizes carbon emissions and develops methanol steam reforming technology. A solid particle steam generator based on the primary heat exchange method has been proposed, which can provide the heat and steam in the methanol steam reforming hydrogen production system. The quasi-two-dimensional packing heat transfer model of solid particles steam generator was set up. The effect of distance change between the vacancy and the cold wall and distance change between vacancies on heat transfer performance of the steam generator and hydrogen production capacity were studied. As the distance between the vacancy and the wall increases, the heat transfer performance of the steam generator gradually deteriorates, so the steam production of the steam generator decreases, and the system's hydrogen production capacity is reduced, the maximum of the heat flux and the minimum of the apparent thermal resistance are 34.67 kW/m2 and 12.02 K/W, respectively. As the distance between vacancies increases, the heat transfer performance of the steam generator is gradually optimized slightly. To maintain the hydrogen production capacity, vacancies should be avoided to appear 2 layers of particles away from the heat exchange wall in the particles steam generator. From the results of the study, the farther the distance between vacancies, the better the steam production and hydrogen production capacity.

Phytic acid as a biomass flame retardant for polyrotaxane based phase change materials

Petrochemical resources are facing depletion and human long-term survival needs sustainable development. In this era, it is very important to develop new sustainable phase change materials (PCMs), because it has shown great application value in the effective utilization of industrial waste heat, solar energy harvesting, and electronic heat treatment. In this work, we reported a biomass phytic acid (PA) modified polyrotaxane (PLR) as PCMs for thermal management. The tensile performances, fire safety, phase transition performances of the PCMs were investigated. It is found that all the tensile properties, char residual, and fire-safety of PLR can be enhanced remarkably by introduce of PA. Typically, the Young's modulus, yielding strength and tensile strength of the PLR were 826.7 MPa, 14.2 MPa and 14.2 MPa, respectively, and significantly increased to 1527.4 MPa, 22.1 MPa, and 24.0 MPa respectively, with the addition of 10 wt% of PA. Elongation (>783 %) for all modified PCMs was gradually increased with the increase of PA contents. Thermal analysis shows that the fire safety of PLR is significantly improved. Specifically, for the best sample PLR-PA30, the pHRR could decrease by 54.2 %, THR decreased by 34.0 %; and the LOI increased from 20.8 % to 28.2 %. The PCMs showed the perfect form stability and leakage-proof performance, enhanced thermal conductivity and outstanding cycle properties. Notably, its biomass source, and high flexibility, enhanced fire safety and completely green pathway may provide a practical way for the highly flexible and sustainable packaging of electronic devices for heat treatment.

Aluminum doping of mesoporous silica as a promising strategy for increasing the energy storage of shape stabilized phase change materials containing molten NaNO3: KNO3 eutectic mixture

Efficient thermal energy storage at high temperature is necessary for both industrial waste heat utilization and continuous solar power generation. Shape-stabilized phase change materials containing mesoporous aluminosilicates and eutectic NaNO3: KNO3 (1:1 mol) molten salt mixture were obtained at 90% wt. salt. The influence of aluminum doping was studied for the first time. All samples show thermal stability up to 550 °C and two distinct phase transitions corresponding to the melting/freezing of nanoconfined and interparticle salt phases. The radius and spherical shape of the nanoconfined phase were determined from the melting and freezing point depressions with respect to bulk. The enthalpy decrease was quantified in terms of surface tension and the contributions of a non-melting fraction of surface adsorbed ions. SBA-15 type aluminosilicates matrices yield composites with high latent heat storage of 76–77 Jg−1, of which 8 Jg−1 for the nanoconfined phase and good thermal reliability. Aluminum doping is a simple and promising strategy for obtaining high temperature, efficient thermal energy storage materials due to a lack of non-melting salt fraction. The resulting shape-stabilized PCMs have a higher operating temperature range and latent heat storage, offering a 36% increase in total heat capacity over the pristine salt.

Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Organic Rankine Cycle (ORC) is an effectively technology for the utilization of industrial waste heat and renewable energy. Zeotropic working fluids are more attractive than pure working fluids due to their lower exergy losses, higher cycle efficiencies and higher work outputs. The thermal stability is the major limitation factor for the selection of working fluid in the high temperature ORCs. This paper investigates the thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid by using ReaxFF reactive molecular dynamic simulations and density functional theory calculations. The thermal decomposition process, the effects of temperature and HFC-227ea to n-hexane ratio on the thermal decomposition of HFC-227ea/n-hexane zeotropic working fluid, and the interaction between HFC-227ea to n-hexane for the thermal stability of zeotropic working fluid were investigated. The results showed that the hydrogen bond formed between HFC-227ea and n-hexane in HFC-227ea/n-hexane zeotropic working fluid improved the thermal stability of n-hexane and weakened the thermal stability of HFC-227ea. Therefore, the thermal stability of the HFC-227ea/n-hexane zeotropic working fluid is better than that of pure n-hexane and weaker than that of pure HFC-227ea.

Modeling approach and simulation study to assess the utilization potential of industrial waste heat in district heating systems

Companies and nations are developing strategies to reduce CO2 emissions and achieve their climate goals. Due to their high share of final energy demand, heating and cooling supply systems are of crucial importance regarding emission reduction. Here, especially the industrial and building sector have a dominating influence, accounting for 34% and 33% of the global final energy demand. Aside from reducing the energy demand or integrating renewable energy sources, the utilization of industrial waste heat represents an effective approach to minimize CO2 emissions in heating supply systems. Here, the coupling of the building and industrial sector via district heating systems offers the potential to utilize industrial waste heat. As the utilization is highly dependent on temperature levels and temporal occurrence, modeling approaches to evaluate the site-specific CO2 emission reduction potential must be developed. To consider heterogeneous industrial heating and cooling supply systems as well as the dynamic occurrence of industrial waste heat and energy demands, we present a tailored modeling approach. The approach enables to model configurable industrial heating and cooling supply systems which can be coupled to district heating systems via an industrial heat transfer station. The simulation models consider different energy converters, temperature levels, as well as waste heat sources. Within our research, different configurations are tested through a simulation study and evaluated by an integrated environmental and economic evaluation module. The simulation study, based on industrial thermal load profiles, shows a maximum waste heat utilization of 66% and a corresponding CO2 emission reduction of 39%, with regard to the industrial site’s emissions. The coupling with a district heating system can reduce the industrial site’s operating expenses by up to 14 %. However, the allocation of the overall economic benefit is dependent on the assumed heat price.

Low-grade industrial waste heat utilization in urban district heating: Simulation-based performance assessment of a seasonal thermal energy storage system

In this study, a large-scale industrial waste heat heating system integrated with borehole thermal energy storage (BTES) and an absorption heat pump was proposed, designed, and assessed using long-term dynamic simulations. Simulations were performed with different reference combinations of storage volumes and circulation flow rates for the borehole heat exchanger, and a procedure for determining the optimal design parameters was demonstrated. The simulation results indicated that a large-scale BTES has significant potential for buffering short-term temperature variations in industrial waste heat recovery systems. The initial quasi-stable temperature of the BTES established itself gradually, and the energy input and output of the storage tended towards stability after 3–4 years of operations. The effect of increasing storage capacity tended to gradually decline with increasing circulation flow rate and storage volume after reaching a peak, becoming marginal at higher design parameter values. This result indicate that the storage volume and circulation flow rate of the system should be optimized according to an appropriate economic index, to maximize economic benefits. The simulation results emphasized the potential of large-scale seasonal BTES systems to be integrated with industrial waste heat recovery systems and district heating networks, to improve the stability of energy demand and efficiency.

Parametric analysis and system optimization of a novel steam production system by synthetic cascade utilization of industrial waste heat

A great deal of waste heat is released in many industrial procedures, resulting in not only serious energy waste but also heat pollution. To alleviate this phenomenon, in-depth analyses of a steam generation system, whose novelty lies in synthesis of mechanical vapor recompression and thermal power conversion processes for dealing with low-grade waste heat utilization, are performed. Determination of organic Rankine cycle (ORC) working fluid and thermal power conversion cycle are conducted in detail. Then, parameter analyses and optimization are investigated. The simulation results show that the ORC–based system performs well in efficiency improvement and cost reduction with 69.41% higher exergy efficiency and 9.66% lower cost per ton of steam than the transcritical carbon dioxide-based system. In addition, there is an optimum flow rate of ORC working fluid for thermodynamic performance. A lower steam compression ratio and a higher heat source temperature are beneficial to improve techno-economic performance. At last, according to optimized results, the steam production yield and exergy efficiency of the ORC–based system are 2.50% and 44.31% under the 100 °C heat source condition, as well as the cost per ton of recycled steam is 7.67 $/ton. The optimizations of the system, working fluid, and parameters provide valuable information for improving system performance.

Optimization of Pipeline Network Layout for Multiple Heat Sources Distributed Energy Systems Considering Reliability Evaluation

Due to the target of carbon neutrality, energy saving has become more important than ever. At the same time, the widespread use of distributed energy systems and the regional utilization of industrial waste heat leads to the existence of multiple heat sources in an area. Therefore, how to design an economical and reliable pipeline network to meet energy-saving demand under multiple heat source conditions becomes a problem. In this work, an optimization method is established to determine the optimal pipeline network topology with minimum total annual cost. In this optimization method, Star tree algorithm, Kruskal algorithm and GeoSteiner algorithm are combined with a linear programming model to establish a distributed energy pipeline network for multiple heat sources. The model incorporates Euclidean Steiner Minimum Tree and Rectilinear Steiner Minimum Tree in the consideration of the topology optimization of Distributed Energy System pipeline networks. Four pipeline network topologies, STAR, Minimum Spanning Tree, Euclidean Steiner Minimum Tree and Rectilinear Steiner Minimum Tree, are evaluated in this paper from economic and reliability perspectives. A case extracted from a real industrial park where steam is the medium is used to prove the validity of the model. The optimization results show that a Euclidean Steiner Minimum Tree pipeline network has a lower total annual cost than three other types of pipeline network and ranks second in reliability. Considering the comprehensive economy and reliability, ESMT is the optimal pipeline network type of distributed energy system with steam as the medium.

Thermal energy storage sizing for industrial waste-heat utilization in district heating: A model predictive control approach

Thermal energy storage (TES) is a key technology for enabling increased utilization of industrial waste heat in district heating. The ability of TES to equalize offsets in demand and supply depends strongly on the sizing, control and integration in a heating plant. We consider the problem of sizing TES in heating plants utilizing a varying waste-heat source. To this end, we propose a combined dynamic simulation and model predictive control approach that accounts for the dynamics and optimal control of the heating plant with TES. A case study has been carried out on a district-heating plant located in Norway, with 90% of its annual heat production being heat recovered from the off-gas from a ferrosilicon plant. We evaluate the effective peak-heating reduction with different TES sizes and the energy-to-heat-flow-ratio for the TES discharging periods as performance metrics. For the case study, our results suggest that a modest TES tank volume of 1500 m3 is sufficient to achieve a half-year peak-heating reduction of 12% and comparable performance with larger volumes. The proposed methodology constitutes a numerically tractable means of incorporating the impact of model predictive control on the sizing of TES for heating plants with time-varying waste-heat supply and demand.

A review of the potential of district heating system in Northern China

In Northern China, coal-fired power plants play a key role in electricity and heat generation, significantly intensifying air pollution. Meanwhile, a large percentage of wind power is curtailed every year owing to its conflict with heat supplies during the winter period, leading to a huge amount of energy waste. The flexibility of district heating systems has the potential to solve this problem and has attracted considerable attention from electric power system operators, thermal power plant owners, and policy makers. In this paper, a comprehensive survey on the potential of district heating systems in accommodating fluctuating heat supply and demand is proposed. The work first provides an overview of district heating systems in Northern China and how to quantify the flexibility of district heating systems. Next, the flexibility requirements and enhancement strategies of the district heating systems in northern China are thoroughly reviewed. The survey indicates that there is still great potential for the development of a flexible heating system. Moreover, state-of-the-art topics are addressed, including the challenges to be overcome and the status quo of clean heating provision, wind curtailment mitigation, and industrial waste heat utilization. Finally, this paper discusses future directions for deploying the flexibility of district heating systems in northern China, including new heat sources, digitalization, demand-side management, heat market deregulation, and energy policy reform.

External use of industrial waste heat - An analysis of existing implementations in Austria

Utilization of industrial waste heat within the company is a rather common practice, whereas the external use, outside the company, is less common and in the focus of this paper. The aim of the paper is to provide the first comprehensive overview of all implementations of external use of industrial waste heat in Austria. Thus the paper is the first to describe key energy figures, e.g. the share of industrial waste heat in district heating. Moreover, three hypotheses are tested: H1 industrial waste heat originates from heat recovery, H2 external provision prefers space heating as sink, and H3 implementations are only realized if they are highly profitable. In order to gather details on all Austrian external waste heat implementations a literature and internet survey was conducted. Forty-five implementations were identified. They have a capacity of 600 MW and deliver 1.75 TWh/a. Two thirds of the projects were implemented after 2010, implying that awareness and/or technoeconomic feasibility are improving. The amounts observed imply: 2% of industrial energy end-use are reused; this provides 2.5% of the end-use for space heating or 7.3% of district heating energy. Fifty percent of the cases base on combustion (H1 rejected); three implementations provide process heat (H2 verified); data on profitability is insufficient (H3 remains unanswered).

Synthesis and thermoelectric properties of tungstentelluride nanobelts

Energy shortage and environmental pollution are getting worse today, researching on renewable energy conversion technology is necessary to reduce greenhouse gas emissions and improve energy efficiency. Thermoelectric materials are a class of green, non-polluting energy conversion materials, which jn ln will play an important role in the utilization of industrial waste heat and solar thermal composite power generation, so they have attracted more and more attention. In this paper, tungsten telluride (WTe2) nanobelts (NBs) were synthesized by chemical vapor deposition (CVD) for study of their thermoelectric transport properties. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) respectively confirm that large-scale WTe2 NBs grown on Si substrates have high quality belt-like nanostructures. Selected area electron diffraction (SAED) shows that WTe2 NBs have a single crystal phase. The thermoelectric transport properties of NBs samples after annealing samples are measured at the temperature range from ~300 to ~652 K. The results proved that the best electrical conductivity is about 9.55×104 S/m and the maximum Seebeck coefficient is about 90 µV K−1. Especially, the maximum power factor of the NBs samples after annealing are nearly twice that of the conventional powders (CPs) samples. The one-dimensional single crystal nanobelt structure has fewer defects, and higher carrier mobility result in higher conductivity, The CPs samples have more defects, small forbidden band width result in low excitation energy, the number of carriers generated in the range of unit temperature variation is large, which result in a low Seebeck coefficient. So WTe2 NBs may be suggested as excellent materials for fabrication of thermoelectric nanodevices with inexpensive and environment friendly.

Thermal conductivity enhanced polyethylene glycol/expanded perlite shape-stabilized composite phase change materials with Cu powder for thermal energy storage

Phase change materials (PCMs) have been widely investigated for thermal energy storage due to their excellent heat storage densities and narrow operating temperature. However, their poor thermal conductivity and shape stability during utilization always restrict their further application. In this paper, polyethylene glycol/expanded perlite phase change materials with Cu powder phase-change materials (PEG-Cu/EP PCMs) are prepared by vacuum impregnation to overcome these problems. The results indicated that Cu particles are well dispersed in PEG and uniformly enwrapped inside the pores and surfaces of EP due to their excellent physical interactions by capillary force and surface tension. Thus the as-prepared composites exhibit superior shape stability around the working temperature around 253 °C. Furthermore, when 9.35% Cu powders are added into PEG, its thermal conductivity of corresponding composite is significantly enhanced by 129.9%, with a nearly invariable phase change enthalpy at the same time. Therefore, the PEG-Cu/EP PCMs are confirmed to be promising energy storage materials for applications in solar energy generation, building energy conservation, and industrial waste heat utilization.

The development of metal hydrides using as concentrating solar thermal storage materials

Metal hydrides high temperature thermal heat storage technique has great promising future prospects in solar power generation, industrial waste heat utilization and peak load regulating of power system. This article introduces basic principle of metal hydrides for thermal storage, and summarizes developments in advanced metal hydrides high-temperature thermal storage materials, numerical simulation and thermodynamic calculation in thermal storage systems, and metal hydrides thermal storage prototypes. Finally, the future metal hydrides high temperature thermal heat storage technique is been looked ahead.

Key issues and solutions in a district heating system using low-grade industrial waste heat

Industrial waste heat is increasingly being recognized as an important source of heat for DH (district heating) systems in cold regions to fill shortfalls in heating requirements, while consuming less fossil energy than with conventional heating sources. Most existing cases of industrial waste heat utilization for heating merely focus on heat recovery from a single waste heat source for heating either in the factory in which the heat is generated or other buildings in the vicinity. The purpose of this paper is to discuss the key issues related to a DH system using two or more kinds of low-grade industrial waste heat, at a temperature between 20 °C and 90 °C, for users a long distance away from the heat sources, including the collection and integration of multiple-grade waste heat sources, long-distance delivery of waste heat, and peak shaving of the system. Solutions to these three issues are proposed to increase the efficiency of the system and for further and better promotion of such a system: 1) “Tangency technology” is designed and applied to find the optimal method of collecting heat from multiple waste heat sources. 2) Lowering the temperature of the return water on the primary side has been proven to be crucial to the collection and long-distance delivery of industrial waste heat. 3) Systems integrating both industrial waste heat and fossil-fuel heat are depicted. Industrial waste heat always provides the base load for the DH system, while the fossil-fuel heat acts as the peak shaver. Lastly, a case study undertaken in Chifeng in northern China demonstrates how these solutions act in a first-ever DH demonstration project using multiple sources of waste heat from a copper smelter. In all, 390,000 GJ of waste heat was recovered, 35,000 t of CO2 emission was reduced, and over 150,000 t of water was saved.

Discussion on Approach to Renovation of Industrial Coal-Fired Boilers in China

This paper analyzed the present status of industrial coal-fired boilers and relevant policies and standard requirements, and had in-depth discussion on alternative ways of industrial coal-fired boilers, pollution control and management optimization for energy saving. It pointed out that options for elimination and replacement of industrial coal-fired boilers are new energy high efficiency boilers, industrial waste heat utilization, heat pump, new energy and renewable energy. For pollutant control, it provided feasible technologies on controlling dust, sulfur dioxide and nitrogen oxides respectively. Energy conservation measures including evenly hierarchical coal feeding technology, low nitrogen high efficiency combustion technology and etc. are stated as well. It ends up with brief analysis of relevant necessary supporting measures for the whole renovation scheme.

Evaluation of a Thermosyphon Heat Pipe Operation and Application in a Waste Heat Recovery System

Efficient and economical utilization of industrial waste heat would result in reduced energy use and thereby contribute to reduction of greenhouse gas emissions to the atmosphere. Two-phase thermosyphon technology has demonstrated the potential capability for waste heat recovery, but it has not been yet utilized in large-scale industrial applications. As a part of an industrial project, various types of thermosyphon heat pipes have been designed and tested for extraction of waste heat and process control in aluminum industry. This article presents the heat and mass transfer model, developed to provide a fast and accurate simulation tool for industrial application of thermosyphon heat pipe technology for waste heat utilization. The mathematical model considers the energy, momentum, and mass transfer equations, in their one-dimensional form, to predict output parameters of the thermosyphon and enable parametric and sensitivity analysis. The mathematical model structure is set up in a way that the least numerical cost and time is spent while the model accuracy is kept at acceptable level for the defined application. To provide experimental data for validation of the simulation model, the proposed thermosyphon was tested experimentally using a test set-up instrumented for this purpose. The simulation results are found to be in good agreement with the experimental data. The developed model and code are viable to be used as a simple and fast tool for modeling, design, and optimization of the thermosyphon as an element in a heat recovery module.