Industrial Heat Recovery Research Articles

Determination of Pressure Drop Correlation for Air Flow through Packed Bed of Sinter Particles in Terms of Euler Number

In order to clearly understand the air flow resistance characteristics in vertical tanks for sinter waste heat recovery in the steel industry, experimental research on the air flow pressure drop (FPD) performance in a sinter bed layer (BL) was conducted. Based on a self-made experimental device, the measurement values of air FPD for different experimental conditions were determined firstly, and then the concept of Euler number (Eu) in heat exchangers was introduced into the study of air FPD in BL; the change rules of Eu under different particle diameters were analyzed. Finally, the air FPD correlation in sinter BL was obtained and described in the form of Eu, and the error analysis of obtained air FPD correlation was performed. The results show that, the air FPD increases as a second power relationship with the increase in air superficial velocity when the particle diameter is constant. The decrease amplitude of Eu gradually dwindles when increasing the Reynolds number (Re), and the decrease in the Eu shows a reciprocal relationship with the Re. As the bed geometry factor increases, the FPD coefficient, A, decreases as an exponential relationship, while the FPD coefficient, B, increases as a first power relationship. The obtained air FPD correlation in the form of Eu in the experiment is well compatible with the measurement values, and the mean deviation of obtained correlation is 4.67%, showing good originality.

Practice of Waste Heat Recovery in Iron and Steel Industry for Urban Central Heating

Practice of Waste Heat Recovery in Iron and Steel Industry for Urban Central Heating

Performance analysis of a novel double stage multifunctional open absorption heat pump system: An industrial moist flue gas heat recovery application

Rising industrial energy consumption and waste heat in moist flue gas exhausts are the key scientific issues. A potential hybrid system with efficient heat recovery technology can fulfill the industrial energy demand for dehumidification, heating and cooling applications by utilizing the waste latent heat. The main objective of this study is to present a multifunctional hybrid system for double stage open absorption cycle to recover the latent heat from the exhaust moist flue gas for heating and to dehumidify the ambient humid air for cooling applications by operating at low-grade heat source. The validated thermodynamic models for energy and exergy analysis are developed for its performance optimization and to conduct a comparison with single stage system. The operating inlet parameters are varied to analyze the performance of both systems. The parametric study results showed that the double stage system can operate for a wider moist gas humidity range such as 0.054–0.2 kg/kg at lower regeneration heat source of 96.3℃ with varying thermal performance of 1.24–2.39 as compared to the single stage system which operates for 0.118–0.2 kg/kg and at 112.3–153.8℃. Furthermore, this hybrid system is capable to provide heating effect of 280.1 kW at thermal performance of 1.73 and 9.85 kW cooling capacity while operating at 113.7℃ heat source temperature. The thermal performance of system is related to the operating pressure in low pressure generator and can be increased 8–11% when pressure is increased from 25 kPa to 35 kPa. However, the cooling capacity is found to be sensitive only to the absorbers and the dew point cooler. The exergy performance results indicate that the exergy efficiency of double stage system is 3–16% higher as compared to single stage with effect of regeneration temperature and varies from 46.2 to 58.63%. Moreover, the highest exergy destruction is found to be in regenerators which accounts for about 49–51% of overall destructed exergy.

Waste heat recovery in steel industry for steam production to feed carbon capture process

Waste heat recovery in steel industry for steam production to feed carbon capture process

Electricity Generation from Low and Medium Temperature Industrial Excess Heat in the Kraft Pulp and Paper Industry

The recovery and utilisation of industrial excess heat has been identified as an important contribution for energy efficiency by reducing primary energy demand. Previous works, based on top-down studies for a few sectors, or regional case studies estimated the overall availability of industrial excess heat. A more detailed analysis is required to allow the estimation of potentials for specific heat recovery technologies, particularly regarding excess heat temperature profiles. This work combines process integration methods and regression analysis to obtain cogeneration targets, detailed excess heat temperature profiles and estimations of electricity generation potentials from low and medium temperature excess heat. The work is based on the use of excess heat temperature (XHT) signatures for individual sites and regression analysis using publicly available data, obtaining estimations of the technical potential for electricity generation from low and medium temperature excess heat (60–140 °C) for the whole Swedish kraft pulp and paper industry. The results show a technical potential to increase the electricity production at kraft mills in Sweden by 10 to 13%, depending on the level of process integration considered, and a lower availability of excess heat than previously estimated in studies for the sector. The approach used could be adapted and applied in other sectors and regions, increasing the level of detail at which industrial excess heat estimations are obtained when compared to previous studies.

Heat Integration for the Air-Conditioning Application using Waste Heat Recovery in the Cast Iron Industry

The energy demand in the cast iron industry has been increasing for the past decades. Besides this, there is also high-energy demand for air conditioning, especially in the hot climate of the United Arab Emirates (UAE). Process integration tools can identify and measures the potential of energy saving via Heat Integration. The current paper presented a case study for industrial buildings' cooling demand via absorption chiller utilizing waste heat from a cast iron industry located in the Emirates Industrial Area, Sharjah, UAE. The Heat Integration approach has been applied via Pinch Analysis and Problem Table Algorithm to identify the minimum hot and cold utilities. Hot streams consist of four high-temperature furnaces exit gases. The heat exchanger network has been designed to fulfill the energy requirement using ProSim Simulis Pinch software (version 2.0). The minimum hot and cold utilities were predicted at 8,793 W and 1,600 W. The Pinch Point was found at 30 (C with more than 80 % of energy recovery. Moreover, the current study can achieve the lowest fuel consumption with fewer emissions, reduced utility consumption, less cost, and superior performance. The paper also includes several recommendations for the improvement of the cast iron industry's overall efficiency.

Electromagnetic self-encapsulation strategy to develop Al-matrix composite phase change material for thermal energy storage

How to break through the corrosion rupture limit of eutectic Al-Si phase change material (PCM) in iron-based encapsulation container has been a major challenge for realizing the high temperature waste heat recovery in metallurgical industry. Herein, we proposed a self-encapsulation strategy of eutectic Al-Si PCM with no need of container via constructing the 3D-honeycomb-SiC reinforced Al matrix composite with Si-rich◎Si-poor cladding structure ([SiC&Si-rich]◎EAl-Si), which can fundamentally address the corrosion issue. Strikingly, such a structure feature delivers the excellent structural stability and superior energy storage capacity with a high thermal conductivity of 96 ~ 62 W·m−1·°C−1 at 75 ~ 550 °C (increased by ~ 10% after 1000 cycles), and giant discharge energy density of 490 J·g−1 (with the capacity retention of over 98.9% after 1000 cycles). Compared with the Al-Si@Al2O3 microcapsule with core–shell architecture, the discharge energy density of the [SiC&Si-rich]◎EAl-Si was enhanced by 19.3%~105.7%. In comparison with conventional iron-based container encapsulation, the [SiC&Si-rich]◎EAl-Si demonstrates a 10.7% and 16.2% improvement in efficiency of charge and discharge process. More importantly, this self-encapsulation strategy of eutectic Al-Si PCM can be further constructed continuously by the electromagnetic continuous separation technology, which can potentially pave the way to achieve the large scale production of the [SiC&Si-rich]◎EAl-Si, thus providing technological support for accelerating the application process of eutectic Al-Si PCM in metallurgical industry.

Comparison of Kalina cycles for heat recovery application in cement industry

The comparison of two Kalina cycles, KCS1 and KCS34 was performed for the cogeneration of electricity from waste heat recovery in the cement industry. Cement industries with clinker daily production capacities between 3,000 and 6,300 t/d were explored. Both Kalina cycles were thermodynamically modeled from mass, energy and entropy balances, heat transfer for the cycle heat exchangers, and equipment cost. The models were developed in Engineering Equations Solver and optimized with genetic algorithm. The objective functions of the optimization were the net power generated and the specific investment cost. The results of thermodynamic modeling showed which cycle parameters influence as independent variables the objective functions allowing to define their limits. It was also observed that a right definition of costs of the system goes through the proper selection of the turbine and the correct dimensioning of the cycle heat exchangers, especially those that make up the heat recovery steam generator. The comparison between the cycles was performed based on the optimization results and allowed us to conclude that the configuration of the Kalina cycle to be used should be analyzed in detail. Both, KCS1 and KCS34 can be used for waste heat recovery in cement industry but, from the point of view of the specific investment cost, the Kalina KSC1 cycle was more competitive. From the point of view of the net power generated this cycle is more promising for daily capacity equal to or greater than 5000 t/d, and the Kalina KCS34 cycle is more interesting for smaller capacities.

Waste Heat and Wastewater Recovery in Textile Processing Industry: A Case Study of Adopted Practices

Textile wet processes dispose of huge amounts of water and energy in the form of hot wastewater and exhaust gas emissions. A significant amount of water and energy can be conserved by adopting various waste heat and water recovery methods, such as the use of heat exchanger, recycling hot wastewater, steam condensate, and cooling water recovery and reuse. In this study, various waste energy and water conservation methods are summarized to highlight their importance for water and energy conservation. For practical consideration, a detailed assessment of such practiced methods was done in one textile processing industry. The obtained results revealed that a high amount of energy and water could be conserved by adopting various waste heat and water recovery methods, with the advantage of reducing environmental pollution while minimizing the consumption of energy and water.

Systematic Comparison of ORC and s-CO2 Combined Heat and Power Plants for Energy Harvesting in Industrial Gas Turbines

Gas turbine power plants are widely employed with constrained efficiency in the industrial field, where they often work under variable load conditions caused by variations in demand, leading to fluctuating exhaust gas temperatures. Suitable energy harvesting solutions can be identified in bottoming cycles, such as the conventional Organic Rankine Cycles (ORC) or the innovative supercritical CO2 (s-CO2) systems. This paper presents a detailed comparison of the potential of ORC and s-CO2 as bottomers of industrial gas turbines in a Combined Heat and Power (CHP) configuration. Different gas turbine models, covering the typical industrial size range, are taken into account and both full- and part-load operations are considered. Performance, component dimensions, and operating costs are investigated, considering ORC and s-CO2 systems specifics in line with the current state-of-the-art products, experience, and technological limits. Results of the study show that the s-CO2 could be more appropriate for CHP applications. Both the electric and thermal efficiency of s-CO2 bottoming cycle show higher values compared with ORC, also due to the fact that in the examined s-CO2 solution, the cycle pressure ratio is not affected by the thermal user temperature. At part-load operation, the gas turbine regulation strategy affects the energy harvesting performance in a CHP arrangement. The estimated total plant investment cost results to be higher for the s-CO2, caused by the higher size of the heat recovery heat exchanger but also by the high specific investment cost still associated to this component. This point seems to make the s-CO2 not profitable as the ORC solution for industrial gas turbine heat recovery applications. Nevertheless, a crucial parameter determining the feasibility of the investment is the prospective carbon tax application.

Estimating the Steam Quality in Power-Generating Boilers from Electrical Conductivity and pH Measurements

The quality of steam produced by boilers is strictly standardized and must be maintained whatever the quality of makeup water and whatever the composition of the boiler unit’s thermal cycle equipment. Under the conditions of constantly improved instruments for chemical monitoring, it becomes possible to develop measurement systems using which the main standardized and diagnostic steam quality indicators can be monitored by measuring the electric conductivity and pH of cooled samples. Unlike boilers operating at a pressure of 13.8 MPa and higher, steam boilers for steam pressures equal to 9.8 and 3.9 MPa—and also industrial heat recovery steam generators—operate with steam that has a higher content of salts and carbon dioxide; in addition, it contains ammonia, which enters into steam from boiler water. Steam quality is often estimated using the two-quadrant nomographic chart of Mostofin, who proposed it more than 50 years ago. In using certain computation algorithms, it is possible to calculate the standardized and diagnostic steam quality indicators, such as concentrations of sodium, chlorides, ammonia, carbon dioxide, and salt content. The article presents an algorithm for estimating the concentrations of the above-mentioned impurities for cooled live steam samples of power-generating boilers operating at pressures below 10.0 MPa, and boilers for superhigh and supercritical pressures, and industrial heat recovery steam generators, including the combined-cycle power plant units. Examples of using the calculation procedure for analyzing the steam quality in industrial boilers are given.

Decision Support System of Innovative High-Temperature Latent Heat Storage for Waste Heat Recovery in the Energy-Intensive Industry

Reductions in energy consumption, carbon footprint, equipment size, and cost are key objectives for the forthcoming energy-intensive industries roadmaps. In this sense, solutions such as waste heat recovery, which can be replicated into different sectors (e.g., ceramics, concrete, glass, steel, aluminium, pulp, and paper) are highly promoted. In this line, latent heat thermal energy storage (TES) contributes as an innovative technology solution to improve the overall system efficiency by recovering and storing industrial waste heat. To this end, phase-change material (PCM) selection is assisted through a decision-support system (DSS). A simplified tool based on the MATLAB® model, based on correlations among the most relevant system parameters, was developed to prove the feasibility of a cross-sectorial approach. The research work conducted a parametric analysis to assess the techno-economic performance of the PCM-TES solution under different working conditions and sectors. Additionally, a multicriteria assessment was performed comparing the tool outputs from metal alloys and inorganic hydrated PCM salts. Overall, the inorganic PCMs presented higher net economic and energy savings (up to 25,000 €/yr; 480 MWh/yr), while metal alloys involved promising results, shorter cycles, and competitive economic ratios; its commercial development is still limited.

Techno-economic analysis of a sCO2 power plant for waste heat recovery in steel industry

Industrial facilities release a large amount of heat as a by-product of their processes. To improve environmental performance and increase process profitability, a portion of the waste heat can be recovered and employed for power generation by recovery systems. Supercritical carbon dioxide (sCO2) plants are emerging as potential alternatives to the well-established technologies for waste heat recovery (WHR) power generation in heavy industry. This paper offers a preliminary techno-economic analysis of a waste heat-to-power system based on a sCO2 closed-loop for a heavy-industrial process.By conducting a parametric investigation on the WHR sCO2 system’s key design parameters, a number of preferable configurations from a thermodynamic perspective were initially identified; they were subsequently analyzed from the economic point of view in terms of net present value (NPV) and pay-back period (PBP). The privileged WHR system configuration achieved an overall efficiency of 30.4% and a power output of 21.6 kWe, providing an NPV of almost US k$ 376 with a PBP of approximately 4.5 years.

Thermoelectric heat recovery in a real industry: From laboratory optimization to reality

Thermoelectricity, in the form of thermoelectric generators, holds a great potential in waste heat recovery, this potential has been studied and proved in several laboratory and theoretical works. By the means of a thermoelectric generator, part of the energy that normally is wasted in a manufacturing process, can be transformed into electricity, however, implementing this technology in real industries still remains a challenge and on-site tests need to be performed in order to prove the real capabilities of this technology. In this work, a computational model to simulate the behaviour of a thermoelectric generator that harvest waste heat from hot fumes is developed. Using the computational model an optimal configuration for a thermoelectric generator is obtained, also an experimental study of the performance of different heat pipes working as cold side heat exchangers is carried out in order to optimize the performance of the whole thermoelectric generator, thermal resistances of under 0,25 K/W are obtained. The optimized configuration of the thermoelectric generator has been built, installed and tested under real conditions at a rockwool manufacturing plant and experimental data has been obtained during the 30 days field test period. Results show that 4.6 W of average electrical power are produced during the testing period with an efficiency of 2.38%. Moreover, the computational model is validated using this experimental data. Furthermore, the full harvesting potential of an optimized designed that takes advantage of the whole pipe is calculated using the validated computational model, resulting in 30.8 MWh of energy harvested during a sample year which could meet the demand of 8.34 Spanish average households.

Prospects for Novel Pinch Analysis Application Domains in the 21st Century

Pinch Analysis was originally developed as a thermodynamically-based methodology for targeting and design of industrial heat recovery systems. Subsequent extensions of pinch analysis have since been developed; for example, mass pinch analysis is derived directly from analogies between heat and mass transfer, and has led to application for the efficient use of mass separating agents (MSAs) in process plants. More recent literature shows Pinch extensions for numerous applications, including energy sector planning using diverse quality measures. Other Pinch techniques have also been developed using time as the quality index, for applications such as production planning, financial analysis, supply chain management, isolated energy system design, batch process scheduling, carbon dioxide sequestration, and human resource allocation. These applications demonstrate how common problem structures allow an elegant solution approach to be developed for seemingly diverse applications. In this paper, past applications of Pinch Analysis are reviewed, and its further prospective extensions that may be developed, based on similar analogies, for non-conventional problem domains are discussed.

Evaluation of the efficiency of a heat recovery steam generator via computational simulations of off-design operation

This work investigates the flow and heat transfer on the gas side of a heat recovery steam generator. During the operation of a power plant, off-design conditions that significantly impact the steam generator efficiency, caused by variations in the gas flow, corrosion and fouling of tube walls, may be encountered. In addition, passages around the heat exchanger modules develop along the equipment lifetime, allowing the bypass of flowing gas into zones of the boiler of low heat transfer effectiveness. These issues are here addressed via computational simulations, using a commercial software application for solving the mass, momentum, and energy conservation equations. The boiler geometry and the boundary conditions for the simulations are taken from a real, typical industrial heat recovery steam generator fed by gas turbines exhaust gases. Flow turbulence is modeled using the k- $${\epsilon}$$ model, and heat exchanger modules are considered as porous media, through which the exhaust gases flow while supplying heat to the water. The water flow properties are specified from process data. Numerical results for thirteen realistic off-design conditions are compared to those for the boiler normal operation point. It is found that the cases considering deviation of gas to the trapdoors and lateral passages have the greatest impact on the boiler efficiency. Results indicate an efficiency drop from 86% for the base case to 48% for the case with gas deviations. In addition, a reduction in the gas flow or the plugging of the low-pressure economizer tubes may decrease the boiler efficiency by more than 10% points.

Development and multi-objective optimization of a newly proposed industrial heat recovery based cascaded hydrogen and ammonia synthesis system

The industrial flue gas emitted to the atmosphere is considered not only harmful to the environment but also a waste of plentiful resources of thermal energy. The thermal energy extracted from the industrial flue gas can be employed for multiple purposes. This study proposes a new configuration to integrate the thermal management of industrial flue gas for thermochemical copper-chlorine (Cu-Cl) cycle based ammonia synthesis. A reverse osmosis desalination unit is employed to supply the freshwater required by the thermochemical Cu-Cl cycle. To recover the heat from high-temperature oxygen stream, thermoelectric generators (TEGs) and organic Rankine cycle (ORC) are integrated with the proposed configuration to utilize the low-grade waste heat for power production. A portion of produced hydrogen through the thermochemical Cu-Cl cycle is supplied to the cascaded system for ammonia production. A double-stage cascaded ammonia synthesis system is integrated with the proposed configuration to achieve high fractional conversion. A multi-objective optimization using genetic algorithm is implemented to the proposed system using the MATLAB to investigate and determine the best-operating temperatures and pressures for the ammonia synthesis system. The proposed configuration produces 518.4 kmol/day of hydrogen and 226.8 kmol/day of ammonia. The overall exergetic and energetic efficiencies are found to be 28.7% and 40.8%. Moreover, the results obtained from the comprehensive sensitivity analyses are presented and discussed.

A computational tool for guiding retrofit projects of industrial heat recovery systems subject to variation in operating conditions

Heat exchanger networks (HEN) in industrial heat recovery systems often consist of large and complex subsystems. Usually, such HENs are subject to variation in operating conditions, such as varying inlet conditions or changing heat capacity flow rates. Additionally, complexities such as stream splits and recycle loops are commonly present in industrial HENs. Therefore, extensive modelling and/or analytical calculations may be necessary when analyzing different retrofit proposals. Furthermore, retrofit opportunities in industrial heat recovery systems are often constrained by operability considerations, i.e. retrofit actions are supposed to have as little impact as possible on the production process to maintain the quality of the core product. In this work, a computational analysis tool is proposed for effective screening of HEN retrofit design proposals at an early stage in the design process. The proposed tool enables fast evaluation of the network’s response, i.e. temperatures and heat loads, when operating conditions change and/or operational settings are manipulated, and it is applicable for a wide range of HEN structures. The practical use of the analysis tool is demonstrated in a case study on the HENs of a large modern Kraft pulp mill.

Willingness-to-Pay for District Heating from Renewables of Private Households in Germany

Recent discussion about future energy production promotes the recovery of industrial heat as a potential solution to reduce carbon emissions. Experts call for an expansion of central heating by renewable energy systems to ensure a decarbonization of energy systems. In this context, district heating could play a significant role in city and district planning. Nonetheless, for private households, environmental aspects are only one factor amongst others as, e.g., capital costs, comfort and security. In this study, we focus on private household preferences and willingness-to-pay for district heating and district heating from renewables compared to gas condensing boilers and heat pumps. For the study, we decided to apply a discrete-choice experiment and collected data on attitudes towards sustainability, economic aspects and demands for providers of heat supply as dimensions for a factor and cluster analysis in order to apply a market segmentation. The results show that district heating by renewables is the most preferred heating option for households followed by district heating from fossil fuels, heat pumps and gas boilers. Furthermore, the study offers more profound insight into the willingness-to-pay for each heating option and reports interaction effects for the different market segments that could be identified in the analysis.

A Framework for Flexible and Cost-Efficient Retrofit Measures of Heat Exchanger Networks

Retrofitting of industrial heat recovery systems can contribute significantly to meeting energy efficiency targets for industrial plants. One issue to consider when screening retrofit design proposals is that industrial heat recovery systems must be able to handle variations, e.g., in inlet temperatures or heat capacity flow rates, in such a way that operational targets are reached. Consequently, there is a need for systematic retrofitting methodologies that are applicable to multi-period heat exchanger networks (HENs). In this study, a framework was developed to achieve flexible and cost-efficient retrofit measures of (industrial) HENs. The main idea is to split the retrofitting processes into several sub-steps. This splitting allows well-proven (single period) retrofit methodologies to be used to generate different design proposals, which are collected in a superstructure. By means of structural feasibility assessment, structurally infeasible design proposals can be discarded from further analysis, yielding a reduced superstructure. Additionally, critical point analysis is applied to identify those operating points within the uncertainty span that determine necessary overdesign of heat exchangers. In the final step, the most cost-efficient design proposal within the reduced superstructure is identified. The proposed framework was applied to a HEN retrofit case study to illustrate the proposed framework.