D2.6 TECHNO-ECONOMIC MAP OF HEAT UPGRADE TECHNOLOGIES
Abstract
Industry must play a major role in the energy transition to meet climate neutrality targets. Increased energy efficiency by recovering and upgrading waste heat is the first step towards decarbonization in the industrial sector. The PUSH2HEAT project aims to push forward the market potential and business models of Heat Upgrade Technologies (HUTs) by full-scale demonstration of heat upgrade systems in relevant industrial sectors with high waste heat recovery and upgrading potential, with supply temperature in the range of 90 to 160 °C.This report provides a techno-economic map of the Heat Upgrade Technologies (HUTs) developed in the project. The objective of the report is to provide a complete overview of the most important techno-economic issues affecting these technologies to reach a wide public with the need or goal to understand how these systems work and can be integrated into the industry. Thus, this report can be useful for different stakeholders, such as industrial plant owners or energy managers, engineering companies, energy service companies, research entities, industrial associations, politicians, etc.In Section 2, a general description of the HUTs of PUSH2HEAT is provided. Those technologies include vapor compression heat pumps (electrically driven), with two different compression technologies, piston compressor and turbocompressor, and thermally driven heat pumps, with two different technologies, the absorption heat transformer and the thermochemical heat transformer.In Section 3, the energetic and environmental benefits of the HUTs are explained, supported by a theoretical comparison with common fossil-fuel-based heat generation technology in the industry.Section 4 goes into more detail regarding the technical characteristics of the HUTs, explaining the basic thermodynamics and operation of the systems and the specific characteristics of each one.Section 5 provides a table with the techno-economic characteristics of the HUTs from the manufacturers working in PUSH2HEAT.Section 6 presents an analysis of the potential feasibility of the HUTs in different countries, considering the different energy costs and their impact on the techno-economic feasibility of integration of the HUTs under different reference conditions.In Section 7, a description of the identified sectors and processes for the HUTs integration is provided. The waste heat sources usually available in the different sectors and the possible upgraded heat use in those sectors are discussed. Also, some possible integration schemes for the HUTs are provided in various processes of interest.Section 8 presents real-world application examples of the four HUTs in PUSH2HEAT. It describes the HUT integration and the most relevant KPIs for those specific case studies.
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Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 1 D2.6 TECHNO-ECONOMIC MAP OF HEAT UPGRADE TECHNOLOGIES V0.3 Grant agreement No: 101069689 From: Tecnalia Prepared by: Laura Alonso (TECNALIA), Jose Luis Corrales (TECNALIA), Mehdi Aminyavari (BONO), Tommaso Toppi (POLIMI), Icíar Bernal (CARTIF), Dalia Janicki (QPINCH), Tim Hamacher (SPH), Aldo Serafino (ENERTIME), Golnoosh Mir (ENERTIME), Jorge Payá (UPV), Gabriel Focht (BS NOVA), Cordin Arpagaus (OST) Date: 30/06/2024
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 2 DELIVERABLE Basic information on the deliverable Dissemination level Public Type Report Due date M20 June 2024 Task 2.6 Task leader TECNALIA Authors TECNALIA (Laura Alonso, Jose Luis Corrales) BS NOVA (Gabriel Focht) SPH (Tim Hamacher) QPINCH (Dalia Janicki) ENERTIME (Aldo Serafino, Golnoosh Mir) BONO (Mehdi Aminyavari) UPV (Jorge Payá) POLIMI (Tommaso Toppi) CARTIF (Icíar Bernal) OST (Cordin Arpagaus) VERSIONS No. Name Partner Contribution Date 01 Cordin Arpagaus OST Review of Version V0.1 29/05/2024 02 Laura Alonso TECNALIA Second review 17/06/2024 03 Maider Epelde TECNALIA Final review 30/06/2024
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 3 ABBREVIATIONS AHT: Absorption heat transformer CAPEX: Capital expenditure CC: Carbon capture CCU/S: CO2 capture and utilisation/storage COP: Coefficient of performance DHN: District heating network HP: Heat pump HTHP: High-temperature heat pump HUT: Heat upgrade technology IEA: International Energy Agency MVR: Mechanical vapor recompression PUSH2HEAT: Pushing forward the market potential and business models of waste heat valorisation by full-scale demonstration of next-gen heat upgrade technologies in various industrial contexts. QTHT: Qpinch thermochemical heat transformer ROI: Return on investment TDHP: Thermally driven heat pump THT: Thermochemical heat transformer VCHP: Vapor compression heat pump VHTHP: Very high-temperature heat pump
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 4 TABLE OF CONTENTS 1. Introduction ..................................................................................................................................7 2. General description of Heat Upgrade Technologies .........................................................8 2.1. Open Systems.................................................................................................................................................................... 9 2.2. Closed Systems ................................................................................................................................................................. 9 3. Energetic and environmental benefits of HUTs .............................................................. 11 4. Heat Upgrade Technologies in PUSH2HEAT .................................................................... 13 4.1. Vapor compression heat pumps............................................................................................................................. 13 4.2. Thermally driven heat pumps ................................................................................................................................. 21 4.2.1. Absorption heat pump .......................................................................................................................................... 21 4.2.2. Thermochemical heat transformer ................................................................................................................. 25 5. Technical specifications of HUTs in PUSH2HEAT ........................................................... 29 6. Techno-economic feasibility of HUTs in several countries .......................................... 31 7. Identified sectors and processes of interest for HUT integration ............................. 35 7.1. Paper sector..................................................................................................................................................................... 37 7.2. Chemical sector .............................................................................................................................................................. 39 7.3. Food & beverage sector .............................................................................................................................................. 42 7.4. Others ................................................................................................................................................................................. 44 7.4.1. District heating ......................................................................................................................................................... 44 7.4.2. CCU/S ............................................................................................................................................................................ 46 8. Real cases. Techno-economic assessment ........................................................................ 48 8.1. Vapor compression heat pumps............................................................................................................................. 48 8.1.1. HTHP integrated into the recycling industry .............................................................................................. 48 8.2. Absorption heat pumps .............................................................................................................................................. 52 8.2.1. AHT integrated in a refinery ............................................................................................................................... 52 8.3. Thermochemical heat pumps .................................................................................................................................. 54 8.3.1. THT integrated into the chemical industry .................................................................................................. 54 9. Reference List ............................................................................................................................ 56
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 5 LIST OF TABLES Table 1: Properties of the main refrigerant for HTHP (Sources: [19], [20], [21]) ..................................... 19 Table 2 Push2heat HUT technologies specifications .............................................................................................. 30 Table 3: Costs refer to the status in 2024 for Germany, Italy, Belgium, and Spain .................................... 32 Table 4: Performance of HUTs for a thermal demand of 1 MW ......................................................................... 33 Table 5: Performance of HUTs for a thermal demand of 500 kW ..................................................................... 34 Table 6: Hot oil applications in plastics processing (Source: [37]) .................................................................. 40 Table 7. Boundary conditions and simulated performance data for hot water heat pump ................... 51 LIST OF FIGURES Figure 1: Potential waste heat flows at the industrial site level (Source: [1]) ............................................... 8 Figure 2: Types of heat upgrade technologies (open and closed systems) ..................................................... 9 Figure 3: Scheme of Push2heat heat upgrade technologies ................................................................................ 10 Figure 4. Comparison between an electrically driven heat pump and a thermally driven heat pump (heat transformer) ................................................................................................................................................................ 10 Figure 5. Simplified schemes comparing the performance of different HUTs ............................................. 12 Figure 6. Example T-s chart (temperature vs. entropy) (a) and cycle layout (b) of an indirect Rankine cycle working with R1233zd(E) ...................................................................................................................................... 14 Figure 7. Heat pump classification based on operating temperature range (Source: [10]) ................... 16 Figure 8. COP of commercial VHTHPs as a function of the temperature lift between the heat sink and source (Source: [13]) ........................................................................................................................................................... 18 Figure 9. Operating ranges of common refrigerants for HTHP (Source: [21]) ............................................ 20 Figure 10. Heat flows in an AHT: Recovery (Q1), revaluation (Q2) and dissipation (Q3) at their corresponding temperature levels. ................................................................................................................................ 21 Figure 11. Estimated maximum upgraded heat temperature levels (orange) in an AHT based on residual heat temperature (blue) for dissipation at ambient level. ................................................................. 22 Figure 12. The thermodynamic cycle of an AHT....................................................................................................... 23 Figure 13. Single-lift (left) and double-lift (right) AHT cycles are represented in a p-T diagram [24] ....................................................................................................................................................................................................... 24 Figure 14. QTHT energy flows.......................................................................................................................................... 25 Figure 15. Dimerization of phosphoric acid. .............................................................................................................. 26 Figure 16. Process scheme of the Qpinch thermochemical heat transformer. ........................................... 26 Figure 17. Chemical process scheme of the QTHT. .................................................................................................. 27
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 6 Figure 18. QTHT temperature jumps. ........................................................................................................................... 28 Figure 19. Heat consumption at two different temperature ranges per sector (Source: [28]) ............ 35 Figure 20. Processes in different industrial sectors structured by typical temperature ranges and Technology Readiness Level (TRL) of heat pumps in 2018 (Source: [10]) ................................................... 36 Figure 21. Sankey diagram of a paper machine (Source: [30]) .......................................................................... 37 Figure 22. Possible integration scheme of a HTHP in a paper machine (Source: [32]) ........................... 38 Figure 23. Scheme of integration of HTHPs into paper production process, including mechanical vapor recompression and thermal storage [33] ....................................................................................................... 39 Figure 24: Integration scheme of a HTHP in chemical industry (Source: [39]) .......................................... 41 Figure 25: Integration of HTHP system to recover waste heat in the dyeing industry (Source: [40]) ....................................................................................................................................................................................................... 41 Figure 26: Simplified scheme of the installation of HTHPs in the pharmaceutical industry (Source: [41]) ............................................................................................................................................................................................ 42 Figure 27: Schematic of a simple HTHP cycle for an industrial process working with waste heat (Source: [45]) .......................................................................................................................................................................... 43 Figure 28: Integration of a HTHP for steam generation recovering WH from the vented steam (legume industry) .................................................................................................................................................................................... 44 Figure 29: The district energy scheme. Red lines: distribution pipes with supply temperatures; Blue lines: pipes with return temperatures (Source: [47]) ............................................................................................ 45 Figure 30: Process schematic diagram after improvement (Source: [48]) ................................................... 46 Figure 31: A generic amine-based carbon capture process flow scheme (Mitsubishi Heavy Industries. (n.d.). CO2 capture technology: CO2 capture process (Source: [50]) ................................................................ 47 Figure 32. Thermal concept of the combination of cooling and heating circuits ........................................ 49 Figure 33. P&ID of the 2-circuit HTHP hot water system (Source: SPH) ....................................................... 49 Figure 34. CAD model of the HTHP hot water system (Source: SPH) .............................................................. 51 Figure 35. Schematic diagram of the AHT integrated in a refinery in Izmit (Turkey) (Source: [27]) 52 Figure 36. AHT developed in the Indus3Es project: design of the 3D model (left), and installation of the prototype at the Tüpras facilities (right). ............................................................................................................ 53 Figure 37. Integration of the QTHT at Borealis (the values in the scheme are given for one of several operating point). .................................................................................................................................................................... 55 Figure 38. Qpinch heat transformer at Borealis in Antwerp. .............................................................................. 55
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 7 1. Introduction Industry must play a major role in the energy transition to meet climate neutrality targets. Increased energy efficiency by recovering and upgrading waste heat is the first step towards decarbonization in the industrial sector. The PUSH2HEAT project aims to push forward the market potential and business models of Heat Upgrade Technologies (HUTs) by full-scale demonstration of heat upgrade systems in relevant industrial sectors with high waste heat recovery and upgrading potential, with supply temperature in the range of 90 to 160 °C. This report provides a techno-economic map of the Heat Upgrade Technologies (HUTs) developed in the project. The objective of the report is to provide a complete overview of the most important techno-economic issues affecting these technologies to reach a wide public with the need or goal to understand how these systems work and can be integrated into the industry. Thus, this report can be useful for different stakeholders, such as industrial plant owners or energy managers, engineering companies, energy service companies, research entities, industrial associations, politicians, etc. In Section 2, a general description of the HUTs of PUSH2HEAT is provided. Those technologies include vapor compression heat pumps (electrically driven), with two different compression technologies, piston compressor and turbocompressor, and thermally driven heat pumps, with two different technologies, the absorption heat transformer and the thermochemical heat transformer. In Section 3, the energetic and environmental benefits of the HUTs are explained, supported by a theoretical comparison with common fossil-fuel-based heat generation technology in the industry. Section 4 goes into more detail regarding the technical characteristics of the HUTs, explaining the basic thermodynamics and operation of the systems and the specific characteristics of each one. Section 5 provides a table with the techno-economic characteristics of the HUTs from the manufacturers working in PUSH2HEAT. Section 6 presents an analysis of the potential feasibility of the HUTs in different countries, considering the different energy costs and their impact on the techno-economic feasibility of integration of the HUTs under different reference conditions. In Section 7, a description of the identified sectors and processes for the HUTs integration is provided. The waste heat sources usually available in the different sectors and the possible upgraded heat use in those sectors are discussed. Also, some possible integration schemes for the HUTs are provided in various processes of interest. Section 8 presents real-world application examples of the four HUTs in PUSH2HEAT. It describes the HUT integration and the most relevant KPIs for those specific case studies.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 8 2. General description of Heat Upgrade Technologies Waste heat recovery is a beacon of sustainability within industrial operations, representing the harnessing and upgrading of thermal energy that would otherwise dissipate unused into the environment. As industries strive for greater efficiency and environmental responsibility, waste heat recovery emerges as a cornerstone for resource optimization and reduced carbon footprints. Through innovative technologies and strategic implementations, it minimizes energy wastage and unlocks opportunities for cost savings and enhanced operational performance. Figure 1: Potential waste heat flows at the industrial site level (Source: [1]) The initial waste heat assessment stage involves discerning internally and externally employable heat. Internally usable heat enhances on-site energy efficiency, and when upgraded with HUTs, it can also be utilized on-site or in other external processes. Subsequently, the second stage entails determining the portion of externally usable heat that couldn't be avoided or reclaimed for internal purposes. Significant amounts of low-grade or waste heat are generated within industrial processes, often below 100 °C, and are frequently overlooked as a valuable resource. This is where HUTs come into play, offering a sustainable solution to capture and utilize this waste heat, transforming it into a useful resource. They are designed to transfer heat from a low-temperature source to a higher-temperature heat sink. In industrial energy management, understanding the significance of waste heat recovery and the role of HUTs is pivotal. Two distinct approaches, open and closed systems, are viable solutions. Open systems utilize external heat sources or mechanical compression to upgrade low-grade heat streams. In contrast, closed systems rely on internal processes driven by electrical or thermal energy to upgrade heat without direct contact with external sources. By comprehending the fundamental differences between these systems, industries can optimize energy utilization and achieve operational excellence.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 9 Figure 2: Types of heat upgrade technologies (open and closed systems) 2.1. Open Systems Mechanical Vapor Recompression (MVR): utilizes a compressor to mechanically increase the pressure of a low-pressure vapor, raising its temperature. The high-pressure vapor then transfers its heat to the process requiring higher temperatures. This system is particularly suitable for applications involving low-temperature waste heat and moderate-temperature requirements. Thermal Vapor Recompression (TVR): employs a high-temperature motive fluid, like steam or hot water, to drive a jet ejector. This jet ejector compresses the low-pressure vapor from the waste heat source, elevating its temperature. Compared to MVR, TVR offers simpler equipment but might require a readily available high-temperature motive fluid source. 2.2. Closed Systems Electrically Driven Heat Pumps: This category facilitates the transformation of waste heat into usable energy forms through electrically driven compressors, contributing to overall efficiency gains and cost savings. These pumps offer versatility and precision control, making them suitable for various industrial applications. Thermally Driven Heat Pumps (or Heat Transformers): by harnessing thermal gradients and differential temperatures, these technologies convert waste heat into usable energy, exemplifying sustainable solutions for industrial energy management. Examples include absorption heat pumps, adsorption chillers, and thermochemical heat transformers. These technologies offer sustainable heat recovery and utilization solutions by exploiting natural temperature variations or waste heat streams.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 16 Figure 7. Heat pump classification based on operating temperature range (Source: [10]) System efficiency The performance of heat pumps is measured through the Coefficient of Performance (COP), calculated as the ratio between the heating capacity delivered to the heat sink (𝑄ℎ) and the work required for running the machine (𝑊), as expressed in the equation below. 𝐶𝑂𝑃ℎ𝑒𝑎𝑡𝑖𝑛𝑔 =𝑄ℎ 𝑊 The theoretically maximal performance of such a heat pump is given by the COP of the Carnot cycle operating between two reservoirs at constant temperature: 𝐶𝑂𝑃𝐶𝑎𝑟𝑛𝑜𝑡 =𝑇𝑠𝑖𝑛𝑘 𝑇𝑠𝑖𝑛𝑘 −𝑇𝑠𝑜𝑢𝑟𝑐𝑒 Where 𝑇𝑠𝑖𝑛𝑘 and 𝑇𝑠𝑜𝑢𝑟𝑐𝑒 are the temperatures (in Kelvin) of the heat sink and heat source, respectively. However, heat pumps normally operate between two reservoirs with temperature variation during the heat transfer processes. In this case, it is more appropriate to evaluate the theoretically maximum performance of the heat pump by Lorenz COP: 𝐶𝑂𝑃𝐿𝑜𝑟𝑒𝑛𝑧 =𝑇 𝑠𝑖𝑛𝑘 𝑇 𝑠𝑖𝑛𝑘 −𝑇 𝑠𝑜𝑢𝑟𝑐𝑒 Where 𝑇 is the entropic mean temperature. The entropic average temperature is used for calculating the average temperature of a medium-changing temperature between states 1 and 2. The entropic average temperature is defined as the ratio of the difference in specific enthalpy h, over the difference in specific entropy s.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 17 𝑇 =ℎ1−ℎ2 𝑠1−𝑠2 For applications without temperature glide in the heat source and the heat sink, the Lorenz cycle equals the Carnot cycle [11]. This definition can be applied to all streams, including the case of steam supply with a combination of condensation at constant temperature and subcooling at varying temperature. For streams with a constant capacity, the entropic mean temperature can be approximated by the logarithmic mean temperature: 𝑇 𝑠𝑖𝑛𝑘 =∆𝑇𝑠𝑖𝑛𝑘 𝑙𝑛(𝑇𝑠𝑖𝑛𝑘,𝑜𝑢𝑡 𝑇𝑠𝑖𝑛𝑘,𝑖𝑛 ) Lorenz efficiency is a measure used to evaluate a heat pump's performance compared to the maximum achievable performance when the heat pump interacts with reservoirs at variable temperatures. The efficiency of vapor compression machines based on the indirect Rankine cycle depends on several parameters, such as the cycle configuration [12], the heat exchangers dimensioning and the efficiency of the compressor. In particular: 1. Internal heat recovery can enhance the heat pump's performance. The most common heat recovery is obtained using a heat exchanger that sub-cools the refrigerant leaving the condenser while heating the vapor leaving the evaporator. 2. The size of the heat exchangers determines how close the refrigerant temperature gets to the temperature of the external fluid. Up to a certain dimension, larger heat exchangpfaers reduce the temperature differences and enhance efficiency at the expense of higher heat pump costs. 3. Compressor efficiency depends on the type of compressor, its capacity (larger compressors are usually more efficient), and the working conditions. In Figure 8, the COP values of different commercial VHTHPs are summarized in a chart depending on the temperature lift between the sink and source [13].
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 18 Figure 8. COP of commercial VHTHPs as a function of the temperature lift between the heat sink and source (Source: [13]) Working fluids Suitable working fluids for HTHPs are selected based on some preferable requirements: • Reasonable pressure (possibly above atmospheric pressure and not too high) at the typical evaporation and condensation temperatures. • Good heat transfer properties (low viscosity and high conductivity) and high latent heat of phase change. • Low specific volume at the compressor inlet conditions. • No flammability, zero ozone depletion potential, low global warming potential, safe and compatible with most materials. Since no fluid meets all these requirements, compromises are usually made based on the conditions. Safety issues can be handled better in industrial applications than in residential applications. At the same time, given the high number of yearly working hours, the characteristics enhancing efficiency are more relevant. The refrigerants currently used in HTHPs can be categorized as follows: HydroFluoroCarbons (HFC), such as R-245fa or R-365mfc are commonly used. However, their GWP is comparatively high, and given the prevention of global warming (F-gas regulation [14]), these working fluids will be restricted in the foreseeable future. Hydrofluoroolefins (HFO), such as R-1234ze and R-1336mzz(Z), are designed to replace HFCs thanks to their low GWPs. R-1336mzz(Z) [15] is particularly suitable for HTHP applications, offering high thermal stability and efficiency. HFOs provide similar performance as HFCs but with reduced environmental impact. Although slightly flammable (R-1234ze is safety class A2L), they require specific system designs to ensure safety. A major concern related to HFO is that, once released into
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 19 the atmosphere, they undergo photo-oxidation to form trifluoroacetic acid (TFA). TFA then descends with rainfall to the earth, primarily accumulating in water and posing a hazard to humans[16]. Consequently, the European Parliament has proposed phasing out these refrigerants by 2050, although the issue has not yet been resolved [17]. However, the present F-gas regulation (F-gas regulation [14]), already bans some of the HFOs for certain applications, such as air-to-water monoblock systems. Hydrochlorofluoroolefins (HCFO), such as R-1233zd and R-1224yd, are emerging as low-GWP alternatives for HTHP applications. R-1233zd is especially interesting for its performance in hightemperature applications, offering a good balance of efficiency, low flammability, and reduced environmental impact. Natural refrigerants are considered the alternative to synthetic working fluids thanks to the low GWP and good overall properties. Natural refrigerants suitable for HTHP applications are water (R-718), CO2 (R-744), ammonia (R-717), and hydrocarbons (HC in Table 1, e.g., R-600, R-601). Among those, water is suitable for high-temperature ranges, while it has the drawback of sub-atmospheric operation when the evaporation temperature is below 100 °C. On the other hand, using CO2 implies high pressures, which may limit certain applications, but some manufacturers produce units with working temperatures around 120-130 °C, even 150 °C [18]. The same stands for ammonia, which is more suitable for refrigeration applications. Among these options, hydrocarbons are the most suitable for properties at typical operating conditions. However, they are characterized by high flammability (safety group A3), which can represent an issue in some contexts, especially for heat pumps of high capacity, employing high quantities of fluid. [19]. In Table 1, the main refrigerants suitable for HTHP applications are summarized, together with their main properties, while in Figure 9, the operating ranges of some refrigerants are reported. Table 1: Properties of the main refrigerant for HTHP (Sources: [19], [20], [21]) Refrigerant Type TCRIT PCRIT ODP GWP safety class [°C] [bar] (R11=1) (CO2=1) R245fa HFC 154.0 36.5 0 858 B1 R1336mzz(Z) HFO 171.3 29.0 0 2 A1 R1234ze(Z) HFO 150.1 35.3 0 < 1 A2L R514A HFO 178.4 34.0 0 2 B1 R1233zd(E) HCFO 165.6 35.7 0.00034 1 A1 R1224yd(Z) HCFO 155.5 33.4 0.00012 < 1 A1 HC-601 (isopentane) HC 196.6 3.4 0 5 A3 HC-600 (butane) HC 152.0 3.8 0 4 A3 HC-600a (isobutane) HC 134.6 3.6 0 20 A3 R-718 (water) Natural 373.9 220.6 0 0 A1 R-717 (ammonia) Natural 132.3 113.3 0 0 B2L R-744 (CO2) Natural 31.0 73.8 0 0 A1
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 20 Figure 9. Operating ranges of common refrigerants for HTHP (Source: [21]) Compressor technologies Compressors are the key component for HTHPs due to the high temperatures at the compressor discharge. In addition to being able to deal with high discharge temperatures, compressors need to handle the required pressure ratio and refrigerant flow rate imposed by the given application. At the same time, the compressor must operate efficiently since it is the component with the largest impact on the performance difference between the Lorenz efficiency and the actual heat pump efficiency. The compressors technologies commonly used and their main characteristics are summarized below: • Screw Compressors: A screw compressor consists of two helical rotors that mesh to compress the refrigerant. They are known for their high efficiency and reliability, especially in industrial-scale applications, where large capacities and high temperatures are common requirements. Screw compressors offer good part-load performance and are less prone to issues related to liquid refrigerant carryover. • Centrifugal Compressors: A centrifugal compressor relies on the principle of centrifugal force to accelerate the refrigerant and increase its pressure. It is highly efficient and capable of handling large volumes of refrigerant gas. Centrifugal compressors are often used in HTHPs for industrial processes and large-scale HVAC systems. However, they require precise control systems to maintain stable operation across varying conditions. • Reciprocating Compressors (or Piston Compressors): A reciprocating compressor converts rotary motion into reciprocating motion, driving pistons to compress the refrigerant. They can deliver high pressures and are often used in HTHPs requiring high compression ratios. However, their efficiency can be affected by variations in load and speed. • Scroll Compressors: These compressors are characterized by their smooth and nearly continuous compression process, which helps minimize energy losses associated with pulsation. They are well-suited for HTHPs because they can effectively handle varying load conditions. Scroll compressors offer good energy efficiency and reliability, making them popular in residential and commercial applications.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 21 4.2. Thermally driven heat pumps The following subsections describe the two types of thermally driven heat pumps developed in the Push2heat project: absorption heat pumps (or heat transformers) and thermochemical heat pumps (or heat transformers). 4.2.1. Absorption heat pump An absorption heat transformer (or type 2 absorption heat pump) is a thermally driven heat pump [22] that works based on the concept introduced before. Its internal processes include the absorption and desorption of refrigerant in a sorbent. There are different working pairs of sorbent-refrigerant, but the technology developed in Push2heat works with water-lithium bromide salt (LiBr), the refrigerant. The heat transformer, from the point of view of external heat sources and sinks, which are used to activate and obtain the machine's useful effect and dissipate heat, works at three temperature levels. Figure 10 shows the temperature levels and thermal fluxes in the cycle. The three temperature levels at which an AHT works and the main components involved include: 4. The driving heat is introduced in the evaporator and generator at a temperature level T1. 5. The useful effect, the heat upgrade, occurs in the absorber due to the exothermic nature of the water absorption by the saline solution, and the driving heat is upgraded to a temperature level of T2. 6. Finally, the condenser dissipates part of the driving heat at a temperature level T0. Figure 10. Heat flows in an AHT: Recovery (Q1), revaluation (Q2) and dissipation (Q3) at their corresponding temperature levels. The temperature lift (ΔTlift) of the AHT is the temperature difference between the upgraded heat temperature level (T2) and the driving heat temperature level (T1). On the other hand, the temperature thrust (ΔTthrust) corresponds to the temperature difference between the driving heat temperature level (T1) and the rejection heat temperature level (T0). For a specific design of an AHT, the heat upgrade capacity decreases when the high-temperature level T2 increases. On the other hand, the heat upgrade capacity increases when the dissipation level T0 decreases or when the driving heat temperature level T1 increases. Finally, conditioned by the T2
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 22 properties of the aqueous LiBr solution, which is the working fluid mainly used in this kind of heat pump technology due to its absorption capacity, single-effect transformers can work up with a maximum heat upgrade temperature of up to approximately 160 °C. Still, the maximal value will depend on the conditions marked by the temperatures T1 and T0. Figure 11. Estimated maximum upgraded heat temperature levels (orange) in an AHT based on residual heat temperature (blue) for dissipation at ambient level. The AHT is the least known and used type of heat pump within the absorption technologies. Although the technology has been developed for a long time in universities, research institutes and companies, and although there are industrial facilities described in the bibliography, the system still needs to be discovered in the market and industry. The effect described on external streams is due to the exothermic absorption of water vapor by the commonly used aqueous solution of Lithium Bromide (LiBr). Single-effect AHTs can increase the temperature of about 50% of the residual energy by about 50 K. Still, this temperature lift depends strongly on the difference between driving heat and rejection heat temperature levels. The AHT can be considered an absorption chiller that works in reverse, and it includes the same main components: a condenser, an evaporator, an absorber, and a generator. The difference between the absorption chiller and the AHT is that in the latter, the absorber and evaporator operate at high pressure, and the condenser and generator at low pressure. Figure 12 shows a schematic of an AHT. T1
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 23 Figure 12. The thermodynamic cycle of an AHT The operation of a LiBr/H2O single-effect AHT has the following steps: 7. Driving heat activates the AHT cycle, separating the refrigerant water from the absorbent, an aqueous LiBr solution. This occurs in the generator. 8. The refrigerant vapor flows to the condenser, discharging its latent heat to a lowertemperature dissipation source, generally at ambient temperature. 9. The condensed refrigerant is pumped at a higher pressure and evaporated, with the driving heat from the heat source, as in the generator. 10. Finally, the refrigerant vapor is absorbed in the absorber by the concentrated LiBr solution from the generator. Due to the exothermic nature of the process, the absorption heat is released at a higher temperature, thus obtaining the revalued heat that is obtained from the AHT and will be delivered to the corresponding application. The single-effect AHT cycle has been described as the industry's most common type of AHT. A doublelift AHT, as presented on the right-end side of Figure 13, increases the complexity and investment cost by adding an additional evaporator and absorber at a higher temperature level but allows for larger temperature lifts of up to 80 K. However, the ratio between the driving and upgraded heat is reduced to 30 to 34 % instead of 50 %. Lubis et al. [23] reported steam generation at 170 °C using driving heat with temperatures between 80 and 90 °C and dissipation temperatures between 20 and 30 °C with a double-effect AHT. Cudok et al. [24] stated that only 5 out of 43 industrial applications reported by the authors of this review were double-lift AHTs.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 24 Figure 13. Single-lift (left) and double-lift (right) AHT cycles are represented in a p-T diagram [24] The main operational risk in AHTs is the crystallization of aqueous LiBr solution, which may lead to the blockage of pipes, heat exchangers or even pumps. However, commercial heat transformers include technical protection against crystallization, and modern-day AHTs include control strategies that avoid operating in points that could lead to crystallization. In addition, corrosion is one of the main risks for the operation of AHTs. The corrosive environment of the LiBr solution is particularly intense at high temperatures and with salt mass fractions higher than 60% [24]. However, safe and sustainable operation boosting heat up to 165 °C is demonstrated as state-of-the-art when the concentration of the corrosion inhibitor Li2MoO4 is properly maintained. Boosting to higher temperatures is possible, but a higher maintenance effort is needed. Another risk for AHT that can result in performance degradation is the presence of non-condensable gases within the vessels. Modern-day AHTs include the so-called purge systems that automatically or helped by maintenance can eliminate these gases. Modern-day AHTs include automatic controllers that ensure the safe and smooth operation of the units, efficient operation for changes in either the driving heat or the dissipation temperature levels, and constant upgrade heat temperature. Ayou et al. ([25] describe the main installations with AHT in recent years. For example, Thermax Ltd has developed equipment with a capacity of between 500 and 1000 kW, which can revalue up to a maximum temperature of 160 °C and have a COP of between 0.45 and 0.50. In the same way, Johnson Controls-Hitachi offers equipment between 150 and 2,475 kW, upgrading the residual currents to between 70 and 140 °C. Cudok et al. [24] published a review of documented facilities. 26 out of 43 are installed in the chemical industry, 9 in the food industry, and the rest in various sectors, such as water treatment, pulp and paper, steel and machinery. In the rest, neither the industry nor the AHT installation process is specified. Despite the lack of detail, the documented facilities are in intensive sectors and processes. Section 7 provides more information on specific sectors and processes for implementing AHT technology.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 25 4.2.2. Thermochemical heat transformer The general principle of THT The thermochemical heat transformer (THT) follows the same general working principle shown in Section 4.2. The heat recovery technology is activated and almost solely driven by wasted heat at low to intermediate temperatures (80°C-120°C). The internal process converts this residual heat into two heat streams: useful process heat at high and rejected heat at lower temperatures. A negligible amount of electrical energy is used to circulate the working fluid. These energy flows are depicted in Figure 14 for the THT of the Belgium-based company Qpinch. This is functionally equal to the Absorption Heat Transformer. Figure 14. QTHT energy flows. 1 The THT process exploits a reversible endoand exothermal chemical reaction, resulting in larger temperature lifts to high temperatures. The technology behind the thermochemical heat transformers was put into practice and developed for industrial application by Qpinch. The Qpinch THT (QTHT) was inspired by the highly efficient reversible biochemical ATP-ADP cycle, which is crucial to the energy metabolism of all living cells. The QTHT uses inorganic, food-grade phosphoric acid (H3PO4) as a medium, forming its dimer and water in an endothermic reaction (Figure 15 left to right). In the reverse reaction, the dimer is hydrolyzed, regenerating the monomer while setting free heat at high temperatures (right to left). [26] 1 ,2 This figure/graph is property of Qpinch BV and cannot be used, reproduced or distributed without Qpinch BV’s written consent. The Qpinch Thermochemical Heat Transformer (QTHT) is a mark of Qpinch BV.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 32 Table 3: Costs refer to the status in 2024 for Germany, Italy, Belgium, and Spain Gas price [€/kWh] Electricity price [€/kWh] Electricityto-gas cost ratio CO2 emission factor (gas) [tn CO2/kWh] CO2 emission factor (elec) [tn CO2/kWh] CO2 emission price [€/tn CO2] Germany 0.047 0.076 1.62 0.000202 0.000287 90.8 Italy 0.042 0.119 2.83 0.000234 0.000247 94.2 Belgium 0.03 0.07 2.33 0.0002 0.000178 150 Spain 0.052 0.109 2.10 0.000182 0.000217 90.74 Given the previous country-dependent parameters, Table 4 shows the minimum waste heat temperature each technology needs to reach 120 °C and 150 °C on the heat sink (process heat) for a thermal demand of 1 MW. From a technical point of view, some technologies can work with lower waste heat temperatures. Still, a maximum payback period of 4 years has been fixed to ensure shortterm investments, which are more likely to be introduced in the industry. The first row of each country corresponds to the minimum waste heat temperature to operate the VCHP with a return period of less than 4 years. A further restriction has been considered on the second row, as the minimum thermal COP in practical TDHPs is 0.4. Thus, this second row represents the minimum waste heat temperature to obtain a maximum payback period of 4 years and a minimum thermal COP of 0.4 with the TDHP. In all the scenarios, the electrical COP of the TDHP has been fixed at 25, so only the thermal COP is shown. This analysis has included different aspects: the operating temperatures, the industry location, and the size of each technology. The investment cost (CAPEX) was obtained from a correlation from IEA HPT Annex 58 [18] for VCHPs, and the characteristic equation method was used for the TDHPs [27]. The most relevant economic indicators are the return on investment (ROI) and the simple payback period.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 33 Table 4: Performance of HUTs for a thermal demand of 1 MW 1000kW process heat production Twasteheat [C] to reach 120C VCHP TDHP CAPEX [k€] ROI [%] Payback [years] COP CAPEX [k€] ROI [%] Payback [years] COPt VCHP TDHP Germany 47.5 - 796.1 27.6 4 2.44 - - - - - 75 796.1 41.8 2.57 3.93 1,021.1 46.8 2.28 0.40 Italy 69.3 - 796.1 27.7 4 3.49 - - - - - 75 796.1 31.8 3.44 3.93 1,021.1 45.1 2.37 0.40 Belgium 54 - 796.1 27.7 4 2.68 - - - - - 75 796.1 38.1 2.84 3.93 1,021.1 43.1 2.49 0.40 Spain 57.3 - 796.1 27.7 4 2.82 - - - - - 75 796.1 39.2 2.75 3.93 1,021.1 48.8 2.18 0.4 Twasteheat [C] to reach 150C VCHP TDHP CAPEX [k€] ROI [%] Payback [years] COP CAPEX [k€] ROI [%] Payback [years] COPt VCHP TDH P Germany 72 - 796.1 27.6 4 2.44 - - - - - 89 796.1 35.9 3.03 3.12 1,016.6 47.1 2.27 0.40 Italy 95.5 - 796.1 27.7 4 3.49 729.9 63.2 1.66 0.46 - 89 796.1 23.2 4.82 3.12 1,016.6 45.3 2.36 0.40 Belgium 79 - 796.1 27.8 4 2.68 - - - - - 89 796.1 32.4 3.38 3.12 1,016.6 43.3 2.48 0.40 Spain 85.5 - 796.1 27.7 4 2.82 - - - - - 89 796.1 31.7 3.46 3.12 1,016.6 49.0 2.17 0.4 For temperature lifts above 50 K, VCHPs have a wider operating range and can perform better. For instance, in Germany, a waste heat temperature of 47.5 C is enough for a VCHP to reach 120 C, whereas 75 °C is required with a TDHP. However, if the waste heat temperature is high enough to reach a reasonable performance with TDHPs (COPt > 0.40), shorter payback periods and higher ROI values can be achieved compared to VCHPs. However, TDHPs also require heat dissipation to the ambient and higher amounts of waste heat.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 34 Table 5: Performance of HUTs for a thermal demand of 500 kW 500 kW heat production Twasteheat [C] to reach 120C VCHP TDHP CAPEX [k€] ROI [%] Payback [years] COP CAPEX [k€] ROI [%] Payback [years] COPt VCHP TDHP Germany 54.2 - 447.8 27.7% 4 2.69 - - - - - 75 447.8 37.3% 2.91 3.93 766.2 31.0% 3.54 0.40 Italy 74 - 447.8 27.7% 4 3.85 837.0 27.2% 4.07 0.37 - 75 447.8 28.3% 3.91 3.93 766.2 29.8% 3.69 0.40 Belgium 61 - 447.8 27.7% 4 3.00 - - - - - 75 447.8 33.9% 3.22 3.93 766.2 28.5% 3.88 0.40 Spain 62.5 - 447.8 27.6% 4.01 3.08 - - - - - 75 447.8 34.9% 3.12 3.93 766.2 32.3% 3.39 0.40 Twasteheat [C] to reach 150C VCHP TDHP CAPEX [k€] ROI [%] Payback [years] COP CAPEX [k€] ROI [%] Payback [years] COPt VCHP TDHP Germany 79 - 447.8 27.6% 4.01 2.68 - - - - - 89 447.8 31.9% 3.44 763.2 31.1% 3.53 0.40 Italy 100.5 - 447.8 27.6% 4.01 3.85 521.3 44.2% 2.43 0.48 - 89 447.8 20.4% 5.48 3.12 763.2 29.9% 3.68 0.40 Belgium 86.5 - 447.8 27.7% 4 3.00 1,089.7 19.3% 5.8 0.30 - 89 447.8 28.8% 3.84 3.12 763.2 28.6% 3.86 0.40 Spain 88 - 447.8 27.6% 4.01 3.07 842.0 29.3% 3.76 0.37 - 89 447.8 28.1% 3.93 3.12 763.2 32.4% 3.37 0.40
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 35 Table 5 shows similar results, although for a smaller scale of 500 kW upgraded heat with the HUTs. Like before, VCHPs show a wider operating temperature range, except for Italy (due to the high electricity-to-gas cost ratio). As the capacity decreases, the specific CAPEX of both technologies increases. This aspect is more marked in TDHPs. In countries with a lower electricity-to-gas cost ratio, the payback is always better with VCHPs, and the opposite is that if the cost ratio is high, the payback is better with TDHPs. The economic feasibility is very dependent on the energy costs, and for this reason, the results should be treated with caution and analyzed case-by-case for other industries. 7. Identified sectors and processes of interest for HUT integration The principal processes in which the PUSH2HEAT heat upgrade technologies work are within those considered low-temperature processes. According to the classification by Arpagaus et al. (2018) [10], VHTHPs (compression heat pumps) provide heat until 160 °C. In recent years, research has been done on ever-higher temperature levels for revalued heat, but the focus in this section will be mainly on the objective temperature range of the PUSH2HEAT project: 90 °C to 160 °C. Regarding thermally driven heat pumps, the absorption heat transformer can upgrade heat until approximately 160 °C and the thermochemical heat transformer until 210 °C. Figure 19 shows the heat consumption in two different temperature ranges per industrial sector in the EU. Focusing on the objective temperature range of Push2heat, the major heat consumption comes from the Food and Tobacco, Non-metallic minerals, Iron and steel and Chemical sectors. Figure 19. Heat consumption at two different temperature ranges per sector (Source: [28]) Heat upgrade technologies in the range of 90 to 160 °C are of interest, especially in industries like the following ones: • Chemical and pharmaceutical; • Pulp and paper; • Food and drinks;
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 36 • Refineries; • Non-metallic mineral; • Iron and Steel; • Non-ferrous sectors. Figure 20 lists processes in different sectors where HTHPs can be implemented. The processes are classified according to their temperature range. Figure 20. Processes in different industrial sectors structured by typical temperature ranges and Technology Readiness Level (TRL) of heat pumps in 2018 (Source: [10])
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 37 7.1. Paper sector As previously described, the pulp &paper sector is among those considered to have major potential for HUT integration. There are many pulp & paper plants in Europe with a significant annual excess of heat discharged into the atmosphere as water vapor. The analysis of this industrial sector is of great importance, in addition to the fact that some of the main companies in the industry are located in Europe. Below are the possible waste heat sources, processes of upgraded heat injection, and possible integration options. Waste heat sources The most energy-intensive process steps in the pulp & paper sector are the production of pulp and the further processing of this semi-finished product to the paper web. As steam is widely used in the paper industry, many waste heat recovery opportunities come from this heat carrier. For instance, steam from the cyclones could be used to separate the pulp from the vapor during the pulping process. Another important waste heat carrier is the exhaust air from the paper machine. As can be observed in the Sankey diagram of Figure 21, a large proportion of energy comes out of the paper machine in the form of hot exhaust air. This energy is normally recovered to heat the supply air to the drying machine, process water, or space heating [29]. Still, extra waste heat can be used to feed HUTs to reevaluate another process stream. Figure 21. Sankey diagram of a paper machine (Source: [30]) Possibilities for upgraded heat injection Different possibilities exist for the upgraded heat that HUTs can produce. Steam generation by HUTs is considered one of the best options for the paper industry. The steam needs in the sector are described in D2.5 (Public Report in Push2Heat project, [31]). Some of the processes requiring steam in the pulp & paper sector are:
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 38 • Steam for cooking the pulp in chemical pulping processes (temperature: 130 to 150 C). • Heating with steam is used to recover the chemical content of the pulping process. • Pulp drying with steam in non-integrated pulp mills. • Heating of the pulp with steam in the bleaching process. • Thermal drying with steam in the paper machine. HUTs can produce low-pressure steam and, if needed, recompress it to a higher pressure using thermocompressors or mechanical vapor recompression (MVR). Thermocompressors are often used in the paper drying process, and they can be integrated to use exhaust vapor from separators [30]. Other opportunities apart from steam generation include heating water streams in processes and drying wet fuels or sludge. Possible integration schemes After analyzing the possible waste heat sources and upgraded heat injection opportunities, some options for integrating HUTs into the pulp & paper sector are described below. Heat pump integrated into the drying machine of a paper plant Figure 22 shows a possible integration scheme of a HTHP in the drying machine of a paper plant. The HTHP uses the exhaust air after preheating, producing steam which, after recompressing, is fed into the cylinders of the paper machine. Figure 22. Possible integration scheme of a HTHP in a paper machine (Source: [32]) Another scheme for integration of HUTs into the paper production process is shown in Figure 23 [33], including different pressure levels and the integration of thermal storage. The joint paper between CEPI and EHPA considers the inclusion of different types of thermal storage (hot water buffer tank, steam accumulator) into these kind of systems, in order to cope with the flexibility needed by the process.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 39 Figure 23. Scheme of integration of HTHPs into paper production process, including mechanical vapor recompression and thermal storage [33] 7.2. Chemical sector Within the industrial sector, the biggest energy consumers in the EU in 2021 [34] were the chemical and petrochemical industry, the non-metallic minerals industry and the paper, pulp and printing industry. The three sectors with the highest final energy consumption were the chemical and petrochemical industry (2,159 PJ or 21.5 % [35] of the total final energy consumption in industry in 2021 in the EU) This makes the need for change in the sector even more critical than in others. Greater resource use, especially when dealing with large quantities of energy, represents significant savings, enough to invest in innovation methods. Integrating the technologies described in this document is a promising and effective solution to taking the first steps in this change. Waste heat sources • Distillation and vulcanization processes in the rubber and plastic industry. • Recovery of the sensible and latent (according to the temperatures) heat in the flue gases will heat a fluid (water) for the heat pump on the evaporator side in the plastic industry. • Cooling compressors waste heat. • Heat recovery from chillers for air conditioning. Possibilities for upgraded heat injection • Drying flows of process fluids. Industrial drying processes can be employed to produce highquality steam. • Steam generation for pharmaceutical companies [36]
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 40 • Heat the diathermic oil in the plastic industry. In this sector, hot oils (also known as thermal fluids, heat transfer fluids and diathermic liquids) are mainly used for the following applications and purposes (see Table 6) Table 6: Hot oil applications in plastics processing (Source: [37]) APPLICATION PURPOSE Blow molding Barrel Cooling Injection molding Mold temperature control Extrusion Barrel Screw Heating and Cooling Lamination (Composites) Coating, Drying PET Crystallization Drying Rubber Drying and Curing Possible integration schemes In the rubber and plastic industry, there are processes where heat can be recovered using the HUTs of the Push2Heat project. One such process involves recovering both sensible and latent heat, depending on the temperatures available in the flue gases [38]. This recovered heat can be utilized to heat a fluid, typically water, on the evaporator side of a heat pump in the rubber/plastic industry. For instance, this waste heat could be employed in the diathermic oil heating process. The integration of the HUT can replace additional equipment, such as a secondary boiler. In this industry, diathermic oil is used as the primary heat source. It is usually used to produce steam required for certain processes, provide hot water for heating systems during startup phases, and space heating and domestic hot water. A prior heat recovery setup (waste heat recovery as depicted in the diagram) enables the retrieval of sensible and latent heat from the flue gases, preheating the process water before it enters the HTHP.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 41 Figure 24: Integration scheme of a HTHP in chemical industry (Source: [39]) Figure 11 shows another possible integration scheme: a heat pump system is integrated to recover waste heat in the dyeing industry. The HTHP elevates the temperature of the dyeing liquid, thereby substituting the oil-fired heater used for heating crude oil. This concept can be replicated in chemical fertilizer waste sources. Figure 25: Integration of HTHP system to recover waste heat in the dyeing industry (Source: [40]) The last example presented is steam generation for pharmaceutical companies. The cold heat source is a heat recovery circuit that is transferred indirectly to the heat pumps. The heat pump uses this
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 48 that the flue gas will be further cooled to 45 °C in the flue gas cooling section of the amine CC plant. 3. From the cooling of amines before entering the absorption tower (number 3 in Figure 31). This heat is usually around 50 °C. Possibilities for upgraded heat injection The major heat consumer is the separation step in which CO2 (number 4 in Figure 30) is thermally removed from the amines. This heat sink operates at a temperature of 136 °C. It accounts for almost all energy required per ton of CO2 captured. Therefore, it is crucial that a carbon-neutral source provides this heat. This is an opportunity for HUTs. By using one or several of the three waste heat sources mentioned above as input, the upgraded heat could be used in the reboiler (number 4 in Figure 31). 8. Real cases. Techno-economic assessment 8.1. Vapor compression heat pumps 8.1.1. HTHP integrated into the recycling industry Recycling of used materials and raw materials is becoming increasingly important. More and more new processes for recycling waste are being developed and implemented on an industrial scale. In the following process, conventional household waste is converted into a high-quality thermoplastic composite material. For this purpose, household waste, previously considered non-recyclable, is split into its basic components of lignin, cellulose, fibers, and sugar in a complex process and then reassembled into a new matrix, the thermoplastic composite material. This will be used in various applications in the future, e.g., vehicle interiors. One process step in the production is drying the material. This requires temperatures of around 130 °C. Boundaries This project involves constructing the first industrial application to produce the new thermoplastic composite material. Fossil fuel was decided not to be an alternative, so a comprehensive heat utilization concept was developed to bundle various waste heat streams and use them as a source for an HTHP. The integration concept includes multiple cooling and heating circuits at different temperature levels, all of which are interconnected. Integration The HTHP is the last link in a series of heat pumps providing thermal energy at different temperature levels. The schematic in Figure 31 shows only a very rough concept focusing on the different heat pumps. In addition to these heat pumps are several other thermal exchangers, such as process heat exchangers or dry coolers for winter relief (delivering cooling water from cold outside temperatures instead of using the chiller) or even buffer storage. The circuit with the lowest temperature operates
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 49 at 8 °C and is used to cool various process steps. This temperature is generated by a chiller, which condensing heat is used in a water circuit at about 35 °C. This level is used for cooling or heat recovery from warm material and exhaust air streams and preheating material streams. It then serves as a source for a medium-temperature heat pump that raises the temperature level to about 75 to 80 °C. This level, in turn, serves as a source for various process steps and a source for the HTHP. This then provides 130 °C hot water for the drying processes. Approximately 1.5 MW of heating power is required for drying. Two heat pump systems, each with two independent refrigeration circuits, are used here, each with a thermal output of approx. 1 MW, so that only three of the installed refrigeration circuits are in operation at any one time, and one circuit serves as redundancy or can cover power peaks in certain situations. Figure 32. Thermal concept of the combination of cooling and heating circuits High-temperature heat pump system Since this application does not use steam as a heat transfer medium but hot water, the setup differs from the system shown in the previous application. Figure 33 shows the circuit diagram for the systems used. Figure 33. P&ID of the 2-circuit HTHP hot water system (Source: SPH)
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 50 The CAD model in Figure 33 shows the compact design with the two compressors on the outside and condensers and subcoolers placed in between. The evaporators are connected in series, and the internal heat exchangers are at the other end. The design data applicable to this application can be found in Table 4. Because of the series-connected evaporators, the two refrigeration circuits operate at different evaporating pressure levels. In the first circuit, the evaporating temperature is about 67 °C; in the second, it is about 62 °C. The condensing temperature, in turn, is very similar in both circuits at about 129 °C. To make optimum use of the large spread in the heat sink, a subcooler was placed downstream of the condenser in each case to subcool the refrigerant further and extract thermal energy. Due to the different evaporation temperatures, the two refrigeration circuits don’t have identical power outputs. To reach 130 °C sink water temperature at the condenser outlet in each refrigeration circuit, different heat sink water mass flows are needed. For this purpose, a distribution valve is integrated into the heat sink water circuit to distribute the water between the two refrigeration circuits. An additional distribution valve in each subpart of the water circuit helps to speed up the warm-up process if the complete water circuit is cold. In this case, only a small part of the flow goes through the subcooler and condenser to reach higher refrigerant temperatures in the condenser. This helps in the warm-up process due to higher temperatures on the high-pressure side of the internal heat exchangers, leading to higher superheat before the compressor and the possibility of higher evaporation temperatures earlier. In the case of water as a heat sink, the Lorenz COP (2) is often used instead of the Carnot COP to assess the system's efficiency. Here, no individual process temperatures are used as a reference, but the entropic mean temperatures are used. 𝐶𝑂𝑃𝐿𝑜𝑟𝑒𝑛𝑧 =𝑇 𝐻 𝑇 𝐻−𝑇 𝐿 (2) The entropic mean temperatures are defined as follows. 𝑇 𝐻=∆𝑇𝐻 ln(𝑇𝐻,𝑜 𝑇𝐻,𝑖) 𝑇 𝐶=∆𝑇𝐶 ln(𝑇𝐶,𝑖 𝑇𝐶,𝑜) (3) With TH, the temperatures are on the heat sink side, and TC is the temperatures on the heat source side. In this application, the Lorenz COP is 9.6. With a designed and simulated COP of 4,4 for the hightemperature lift from 75 to 130 K, this means a Lorenz quality of approximately 46%. The system has been installed in the first half of 2023.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 51 Table 7. Boundary conditions and simulated performance data for hot water heat pump Parameter Value Heat Source Inlet 75 °C Heat Source Outlet 65 °C Heat Sink Inlet 90 °C Heat Sink Outlet 130 °C Thermal Output 1,017 kW Cooling Power 809 kW Electrical Consumption 229 kW COP 4,4 Refrigerant R1233zd(E) Figure 34. CAD model of the HTHP hot water system (Source: SPH) Environmental impact With a planned annual service life of approx. 8,000h, about 10.8 GWh of thermal process energy will be produced in the future. This corresponds to approx. 1.25 Mm³ of natural gas, which will not be required using the heat pump. As the user consequently follows the principle of sustainability, only CO2-neutral produced electricity is used in this project, so that approx. Compared to a natural gasfired process heat production, 2,400 t CO2 per year is avoided yearly.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 52 8.2. Absorption heat pumps 8.2.1. AHT integrated in a refinery Within the Indus3Es project [51], a successful demonstration of an AHT integrated into the petrochemical industry was developed. During the project, completed in 2020, an AHT was designed and installed at the Tüpras plant in Izmit (Turkey). All high-security requirements from the refinery, especially for explosive atmospheres (ATEX requirements), had to be considered for its installation. The Izmit plant demonstrator uses steam from a condensate tank at approximately 100 °C as a waste heat source. This heat is transferred to a closed circuit, which feeds and activates the AHT at approximately 95 °C and is returned at 90 °C to the exchanger, closing the waste heat recovery circuit. On the other hand, the temperature of the stream to be revalued, demineralized supply water, is considered constant throughout the year and equal to 65 °C. Part of the waste heat source is used to preheat the demineralized water from the supply head from approximately 65 °C to 95 °C, to then raise it to 135 °C with the heat supplied by the absorber of the AHT. Figure 35. Schematic diagram of the AHT integrated in a refinery in Izmit (Turkey) (Source: [27]) The AHT demonstrated in the Izmit refinery has several innovations: • Implementation of two adiabatic absorption modes of operation. The equipment consists of a spray distribution system combined with a drip distribution system with an open tray to promote the adiabatic absorption of water vapor by the saline solution. Laboratoryscale measurements showed that these modes increase the revaluation temperature in the absorber. For demonstration and research purposes, the atomization mode can be turned on or off.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 53 • Innovative non-condensable gas purge system: The presence of non-condensable gases drastically reduces the absorption process, which is critical for the AHT behavior. The system developed in the Indus3Es project collects non-condensable gases in a tank through continuous adiabatic absorption. These gases are periodically and automatically discharged into the environment. This solution, which can be considered simple and economical, optimizes the operation of the equipment and reduces maintenance efforts. • Automatic control based on the "Characteristic Equation": The control system has been designed especially considering the "Characteristic Equation Method" approach. In addition to procedures for automatic adjustment of optimal operation, new anticrystallization modes have been considered, which are potentially riskier when compared to absorption chillers. The equipment was monitored working in the two possible operating modes: non-adiabatic and adiabatic modes. Under nominal conditions, the AHT can revalue up to 198 kW during adiabatic mode, while the complete system, considering preheating, contributes approximately 268 kW. By using the adiabatic distributor, the capacity of the AHT is increased to about 214 kW. The thermal efficiency (thermal COP) of the AHT was approximately 50%. Figure 36. AHT developed in the Indus3Es project: design of the 3D model (left), and installation of the prototype at the Tüpras facilities (right). Calculation of the relevant KPIs during a 20-year use phase leads to the following results: • Saved fossil fuel consumption: 49,821,624 kWh • Primary energy savings in fossil fuels: 51,844,382 kWh of primary energy • Economic savings in fuel consumption: 1,634,221 € • Savings in CO2 emissions: 11,957 tons of CO2
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 54 The total consumption and the costs related to the operation are: • Electricity consumption: 3,321,442 kWh • Primary energy consumption: 6,551,544 kWh of primary energy • CO2 emissions: 1,451 tons of CO2 • Electrical costs: 201,756 € • Maintenance expenses: 356,840 € With these results, net consumption and economic savings would be: • Total primary energy savings: 45,292,838 kWh of primary energy • Total savings in CO2 emissions: 10,506 tons of CO2 • Total financial savings: 1,752,047 € 8.3. Thermochemical heat pumps 8.3.1. THT integrated into the chemical industry A commercial example of the Qpinch thermochemical heat transformer (QTHT) is located in the port of Antwerp area at Borealis. In this case, the QTHT transforms low-temperature heat from an exothermic ethylene polymerization (LDPE) reactor and a low-pressure steam vent into valuable medium and high-pressure steam (MPS & HPS). The LDPE reactor produces over 40 recipes and requires different heat input levels, emitting highly fluctuating residual heat temperatures. To harvest all available waste heat and stably produce MPS or HPS, the QTHT thus has to show great flexibility, reliability and ease of operation. Three different residual heat sources are combined via an intermediate hot water loop to use as a heat source for the QTHT. This heat is lifted to steam at 3 to 10 bar(g) with an output capacity between 400 kW and 1.3 MW. The unit is installed as an add-on to the reactor setup with minimal integration efforts. This way, close to 50% of the waste heat offered to the unit can be revalued. The integration scheme is shown in Figure 37 below. Transforming waste heat via the QTHT brings value to Borealis in the following ways: 1. There is a significant direct energy cost saving on MPS and HPS since QTHT steam has marginal OpEx. 2. The CO2 emissions of the site directly decrease since the steam boilers need to produce less MPS and HPS. 3. The QTHT adds to the cooling capacity of the site.
Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. 55 Figure 37. Integration of the QTHT at Borealis (the values in the scheme are given for one of several operating point). 6 The QTHT unit is installed at the Zwijndrecht site of Borealis with a footprint of 4 x 6 m and a height of 15 m. It can easily be switched on and off without affecting the LDPE reactor operations. The Borealis QTHT is depicted in Figure 38. Figure 38. Qpinch heat transformer at Borealis in Antwerp. 7 6 This figure/graph is property of Qpinch BV and cannot be used, reproduced or distributed without Qpinch BV’s written consent. The Qpinch Thermochemical Heat Transformer (QTHT) is a mark of Qpinch BV. 7 This figure/graph is property of Qpinch BV and cannot be used, reproduced or distributed without Qpinch BV’s written consent. The Qpinch Thermochemical Heat Transformer (QTHT) is a mark of Qpinch BV.
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