Design and multi-objective optimization of ORC systems for multi-temperature waste heat recovery in petrochemical industry

Waste heat recovery in the energy intensive industry is one of the most important measures for the mitigation of climate change. The present study examines the integration of a packed bed thermal energy storage for waste heat recovery in the iron and steel industry. Along with the highly fluctuating availability of excess heat the main difficulty of waste heat recovery in industrial processes is the high amount of powder that is transported by the hot exhaust gases. Therefore, the experimental investigations in this study focus on the powder hold-up and pressure drop in a packed bed thermal energy storage that is operated with a gas-powder two phase exhaust gas as heat transfer fluid. The ultimate goal is, to assess its suitability and robustness under such challenging operational conditions. The results indicate, that 98% of the powder that is introduced into the system with the heat transfer fluid during charging accumulates in the packed bed. Remarkably, most of the powder hold-up in the packed bed is concentrated near the surface at which the heat transfer fluid enters the packed bed. When reversing the flow direction of the heat transfer fluid to discharge the storage with a clean single phase gas, this gas is not contaminated with the powder that has been accumulated in previous charging periods. The entirety of these findings reinforces the suitability of packed bed thermal energy storage systems for waste heat recovery in the energy intensive industry.

As the increase of the energy consumption and the deterioration of environment, a carbon tax will be imposed in China to reduce carbon emissions strictly and the industrial waste heat recovery has been getting more attention. The Organic Rankine Cycle (ORC) system has been proven to be a promising solution for the utilization of the low-grade heat sources. There are five waste heat sources from a 1.2 million ton reforming and extraction unit in Shijiazhuang Refining & Chemical Company of China. The temperatures of the waste heat sources are 98∼80°C, 104∼80°C, 147∼80°C, 205∼80°C and 205∼80°C, and the heat loads are 6.5MW, 11.5MW, 8.6MW, 3.8MW and 2.2MW, respectively. This paper studies the thermal design and performance optimization of a comprehensive utilization system for these waste heat sources, using ORC technology. The selection of suitable organic fluid is studied and the working parameters are designed and optimized with the application of the first law and the second law of thermodynamics. When the ORC systems are designed separately for the recovery of five waste heat sources, and the total power output is 3338.89kW with different organic working fluids. However this kind of designs leads to a very complex recovery system which needs large investment and space occupation. To reduce the overall system complexity, a single ORC system is proposed to recover all five heat sources, and the total amount of output power will only be 2813.02kW, due to the large exergy loss. With the above results shown, and for the purpose of simple system with large power output, this paper further studies the dual ORC systems heat recovery plan, with R245fa as the top cycle working fluid and R141b as the bottom cycle working fluid. The total amount of power output to 3353.27kW. The dual systems with single working fluid heat recovery plan is also studied, and with R141b as the working fluid for both the top cycle and the bottom cycle, the total amount of power output is 3325.03kW, and the heat recovery system is simple and compact, with good economical benefit.

Brayton cycles as waste heat recovery systems on series hybrid electric vehicles

The results of a study entitled, Applications of Thermal Energy Storage to Process Heat and Waste Heat Recovery in the Primary Aluminum Industry are presented. In this preliminary study, a system has been identified by which the large amounts of low-grade waste energy in the primary pollution control system gas stream can be utilized for comfort heating in nearby communities. Energy is stored in the form of hot water, contained in conventional, insulated steel tanks, enabling a more efficient utilization of the constant energy source by the cyclical energy demand. Less expensive energy storage means (heated ponds, aquifers), when they become fully characterized, will allow even more cost-competitive systems. Extensive design tradeoff studies have been performed. These tradeoff studies indicate that a heating demand equivalent to 12,000 single-family residences can be supplied by the energy from the Intalco plant. Using a 30-year payback criterion (consistent with utility planning practice), the average cost of energy supplied over the system useful life is predicted at one-third the average cost of fossil fuel. The study clearly shows that the utilization of waste energy from aluminum plants is both technically and economically attractive. The program included a detailed survey of all aluminum plants within the United States, allowing the site specific analyses to be extrapolated to a national basis. Should waste heat recovery systems be implemented by 1985, a national yearly savings of 6.5 million barrels of oil can be realized.

The usage of wasted energy in human‐made processes to reduce the need of more energy coming from raw materials has been recorded since the Industrial Revolution. Shipping, being the most energy‐efficient means of transportation, commonly uses waste heat recovery systems on board to further increase its operative efficiency. Waste heat is used to produce steam or electricity which is consumed on board. As main engines' thermal efficiencies start to plateau because they are close to the theoretical maximum efficiencies and as emission regulation becomes more stringent, it is important to look for alternative usages, processes, and designs of waste heat recovery systems. The purpose of this article is to give the reader a broad idea of how the energy on board a ship can be reutilized in order to increase the ship's fuel consumption, hence reducing the emission of noxious gases (e.g., CO 2 and NO x ) into the environment. Also, it explores traditional and alterative waste heat recovery processes, usages, and systems, which are installed on board nowadays or could be in the near future. This work focuses mainly on the use of the ship's prime mover waste heat, but this does not mean that the technologies and approaches described in this article cannot be applied to other systems such as auxiliary engines or electrical generators on board. This article starts with the history of waste recovery systems and then moves for a brief description of different marine CO 2 ‐mitigating strategies and where the available waste heat can be found on board. It then covers what a thermal machine is and how it can be used to produce heating, cooling, and mechanical and electrical power through different thermodynamic and electrical processes. Finally, it concludes that traditional and alternative waste heat recovery systems installed on board are important players in achieving more efficient shipping.

A numerical model was developed to simulate thermal conductivity and electrical energy transfer processes in a thermoelectric generator (TEG) designed for low-grade waste heat recovery in the sugar industry. In this study, the researchers selected four thermoelectric (TE) cooling modules of TEC1-12706 and TEC1-12710 and TE power modules of SP1848-27145 SA and TEG1-127-40-40-250 for testing of low-grade heat at a temperature of 200 °C. The test results indicated that an aluminium plate of 10 mm in thickness was most effective for creating heat exchange that is favourable for installation in a TEG system. The TEC1-12710 could generate a maximum power output of 126.15 W at a matched load of about 1.65 Ω. The thermoelectric power generation system can convert 11.5% of heat energy into electrical energy. Finally, the electrical energy costs for TEC1-12710 were estimated to be USD$ 0.22 per kWh, which is comparable to TEC1-12706, SP1848-27145 SA and TEG1-127-40-40-250. Therefore, the TE cooling module in the current work is an interesting and new alternative for power generation from waste heat in sugarcane industries.

In this study, a methodology for optimal sizing of waste heat recovery (WHR) systems is presented. It deals with dynamic engine conditions. This study focuses on Euro-VI truck applications with a mechanically coupled Organic Rankine Cycle-based WHR system. An alternating optimization architecture is developed for optimal system sizing and control of the WHR system. The sizing problem is formulated as a fuel consumption and system cost optimization problem using a newly developed, scalable WHR system model. Constraints related to safe WHR operation and system mass are included in this methodology. The components scaled in this study are the expander and the EGR and exhaust gas evaporators. The WHR system size is optimized over a hot World Harmonized Transient Cycle (WHTC), which consists of urban, rural and highway driving conditions. The optimal component sizes are found to vary for these different driving conditions. By implementing a switching model predictive control (MPC) strategy on the optimally sized WHR system, its performance is validated. The net fuel consumption is found to be reduced by 1.1% as compared to the originally sized WHR system over the total WHTC.

This paper presents results given by a waste heat recovery (WHR) system applied to a high-performance video card, as well as average energy generated per hour according to emulation of computer graphics requirements demanded by the user while the card is working. A WHR system includes three phases: (1) waste heat collection, (2) energy conversion and (3) signal conditioning. The analysis of the WHR system is presented. The emulation of waste heat has been generated using electrical resistors as if they were the main components that generate waste heat, mainly the GPU (graphics processing unit), and DDR3 memories. This WHR system has considered the MSI-R4850 video card as a reference, operation temperature of which has an overall range between 60°C- 90°C. Thermoelectric generator modules (TEG) are based on the Seebeck effect, and the thermoelectric array used is an important part of the WHR system, which has been constructed based on the locations of the main components to convert waste heat into electrical power. The waste heat recovery process has two treatments: First, once the operating conditions, per GPU and DDR3 memories have been emulated, the energy recovered is measured per component and whole WHR system; the second one measures energy recovered considering the output signal conditioning of the WHR system, which was converted to 5V output through a DC-DC boost converter, while the input voltage operates within a range (0.9V- 5V). The energy recovered may be applied to low-power electronic devices, which is a contribution to energy efficiency.

Assessment of the optimum operation conditions of a plate heat exchanger for waste heat recovery in textile industry

This paper explores the potential of Waste Heat Recovery (WHR) systems to enhance sustainability and energy savings in cement production. The cement industry is energy-intensive, with significant waste heat generated from kiln operation and clinker cooling processes. By recovering and utilizing this waste heat, WHR systems can generate electricity, reduce grid energy consumption, and mitigate CO₂ emissions. This study focuses on implementing a WHR system at the Cement Plant. Using data from the plant, including flue gas temperatures of 368°C and hot air from the clinker cooler at 244°C, a comprehensive model was developed in Aspen plus V12 to simulate the WHR system integrated with the plant's operations. The WHR system was designed around an Organic Rankine Cycle (ORC) with carefully selected working fluids optimized for low- to medium-temperature heat recovery. The techno-economic analysis reveals that the system could generate 27.5 GWh of electricity annually, reducing grid electricity consumption by 25%. This corresponds to approximately 16,967.5 tons of CO₂ emission reductions annually, given a high electricity emission factor of 0.617 kg CO₂/kWh. The financial analysis indicates that the levelized cost of clinker production with the WHR system is $2.54 per ton, with a payback period of 9 years. This demonstrates the economic viability of the system, alongside its environmental benefits. The study highlights WHR systems as a practical solution for improving energy efficiency and sustainability in cement production, particularly in regions with high carbon-intensive electricity grids. The findings provide a strong case for the broader adoption of WHR technology in the cement industry.

This paper presents potential application of waste heat recovery (WHR) systems in high-temperature reactors technology. WHR systems have attracted the attention of many researchers over the past two decades, as using waste heat improves the system overall efficiency, notwithstanding the additional cost to upgrade the plant efficiency. WHR systems require specially designed heat recovery equipment, and as such the high-temperature gas-cooled reactor used and/or spent fuel tanks (SFTs) were considered by the way of example. An appropriately scaled system was designed and modelled to demonstrate the functioning of such a system, by the way of a cooling process of the used and/or SFT. Two separate and independent cooling lines, using a natural circulation flow in a particular form of heat pipes called thermosyphon loops were used to ensure that the fuel tank (FT) is cooled when the power conversion unit has to be switched off for maintenance, or if it fails. Assuming a one-dimensional flow model, a quasi-static and incompressible flow of both liquid and vapour, a theoretical model that simulates the heat transfer process in the as-designed WHR system is developed in this paper.

Volumetric expanders for low grade heat and waste heat recovery applications

A novel cascade organic Rankine cycle (ORC) system for waste heat recovery of truck diesel engines

Locomotive engines are emitting high levels of exhaust gas emissions and substantial amount of particulates which is thought to have significant global warming potential. In the past years locomotive regulations have been implemented in the United States to control the emission in this application. Also it can be observed that engine emitted carbon dioxides (CO2) will be limited soon for all on-road engine categories to meet the Green House Gases (GHG) norms. Tier 4 standards apply to locomotives since the beginning of 2015 for newly built or remanufactured engines. NOx and particulate limits have been reduced by around 70% compared to the Tier 3 standards requiring significant advancements in engine technology and / or exhaust aftertreatment solutions. EGR technology is an option to reduce NOx emissions to Tier 4 locomotive standards indeed of its impact on engine fuel consumption as well as the emitted CO2 gas, which may be controlled either by future CO2 or fuel consumption standards. To cope with this challenge, new engine technology concepts need to be developed. A waste heat recovery system is a beneficial solution to recover the wasted energies from different heat sources in the engine. Especially the considerable amount of exergy in the exhaust gas (EGR and tailpipe), which results from its high temperature and mass flow, has significant recovery potential. By utilizing a waste heat recovery system a portion of this exergy can be converted into a usable form of power, which then will increase the effective power output of the engine system. A major challenge is to recover the wasted exhaust energy with the maximum possible system efficiency. In a Tier 4 locomotive engine, heat from the EGR system as well as the tailpipe waste heat can be recovered by using an Organic Rankine Cycle (ORC) waste heat recovery system. This paper will discuss the results of a waste heat recovery (ORC) system evaluation for locomotive applications. With the help of thermodynamic calculations the incremental power from ORC system as well as the fuel economy benefit will be evaluated and discussed. Additionally, a reasonable working fluid and the system layout, which are considered for thermodynamic calculations, will be reviewed.

Exergy based model predictive control of an integrated dual fuel engine and a waste heat recovery system