Energy storage application of phase change material in heating chemical production process

Abstract

Systems and methods for storing and releasing thermal energy for heating in a chemical plant process. Some such systems may include a phase change material (PCM) comprising a volume; and a heat exchange system configured to transfer thermal energy from the PCM to one or more of a chemical reactant, a chemical intermediate, or a chemical product; wherein the PCM is configured to transition from a first state to a second state of high enthalpy at a transition temperature equal to or higher than a process temperature of an associated chemical reactant, chemical intermediate or chemical product; and wherein the PCM requires at least 2 MWh to transition from the first state to the second state.

Description

Technical Field

[0001] The present disclosure relates generally to processes for producing chemicals, and more particularly, but not limited to, using phase change materials (PCMs) to store heating energy in chemical production processes. Background Art

[0002] As chemical plants shift from burning fossil fuels to meet daily energy needs to using electricity from the grid and / or from renewable energy, the availability and cost of electricity will change over time. For example, electricity from the grid is usually more expensive during peak hours. In addition, the generation of solar and wind energy varies with the time of day and weather conditions, for example, the night time and cloudy time period will reduce or interrupt the power generation of solar panels. Similarly, during periods of slow wind speed or no wind, the power generation of wind turbines will be reduced or interrupted. In addition, during peak hours when power production or grid capacity is tight, power companies may provide discounts to customers who can flexibly adjust consumption needs. Storing energy can avoid energy consumption from some external sources (such as the grid, solar energy, wind energy, etc.) during periods when energy is more expensive (such as peak hours) or periods when energy availability is limited (such as dark hours for solar energy or static hours for wind energy). Reducing external energy demand during peak hours of the grid also has the additional benefit of promoting grid stability. However, from a commercial perspective, it is usually very important for chemical plants to maintain consistent production, even during periods when external energy demand is reduced, that is, even when relatively less electricity is obtained from external sources. Summary of the invention

[0003] The systems and methods of the present invention utilize phase change materials (PCMs) to release thermal energy to operate or supplement heating cycles in chemical processes of chemical plants, such as in conjunction with evaporators or heaters powered by electricity rather than burning fossil fuels.

[0004] The PCM is "charged" by adding thermal energy from a heat source to transform the PCM from a first state (e.g., solid) to a second state (e.g., liquid) of higher enthalpy, and then the PCM can be "discharged" by releasing thermal energy to the heating cycle to reduce the instantaneous external energy (e.g., from electricity or combustion of fossil fuels) required for the heating cycle. For example, PCMs can be used to reduce external energy requirements during periods when electricity from renewable energy sources is less or unavailable (e.g., during periods of reduced sunlight from solar power sources, or reduced wind from wind power sources) or when electricity from the grid is more expensive or unavailable (e.g., during peak hours, when power companies require reduced electricity use to ensure grid stability, or during grid blackouts). For example, the systems and methods of the present invention can be configured to have a total mass / volume of PCM that is large enough to require at least 2MWh (e.g., greater than or between any two of the following: 2MWh, 5MWh, 10MWh, 20MWh, 25MWh, 50MWh, 100MWh, 150MWh, 200MWh, 500MWh) to transition from a first state to a second state. It is believed that such use of PCMs has never been previously used for heating chemical processes in chemical plants, at least in part because such chemical processes require large amounts of energy and primarily use fossil fuels, the large fluctuations in supply or cost of which are not as frequent as electricity (particularly electricity from renewable energy sources). Traditionally, the scale of such energy requirements has not only been cost-prohibitive, but has also been hindered by the technical challenges inherent in using PCMs to store such large amounts of energy.

[0005] Once heated and thus liquefied, the PCM can release thermal energy to the chemical process so that the process does not need to further operate the heater and / or evaporator to continue to drive the heating cycle of the chemical process. In this way, the initial addition of thermal energy to the PCM effectively "stores" the energy required to run the heating cycle of the chemical process during the period when the PCM is "discharging" by releasing thermal energy to the chemical process.

[0006] For example, when a chemical plant draws electricity from the grid, differences in electricity prices at different times of the day can be advantageous in drawing more energy from the grid to (a) operate the heater, heat pump, and / or evaporator in the heating cycle of the chemical process, and (b) charge the PCM during off-peak hours (when electricity prices are lower), and then release the thermal energy to the chemical process by using the PCM, instead of or in combination with using a heater, heat pump, and / or evaporator that can be used exclusively for the heating cycle during off-peak hours to draw less energy from the grid during peak hours (when electricity prices are more expensive). In some configurations, the heater, heat pump, and / or evaporator used in the heating cycle of the chemical process may be larger than required for the immediate operation of the chemical process, so that the heater, heat pump, and / or evaporator can be used for both the chemical process heating cycle and the PCM heating cycle to charge the PCM. In other configurations, one or more separate heaters, heat pumps, and / or evaporators can be used for different PCM heating cycles used when charging the PCM.

[0007] The methods and systems of the present invention can be used for any chemical process heating loop within the operating temperature range of a particular PCM. For example, the methods and systems of the present invention can be applied to distillation systems, particularly distillation systems with a narrow boiling point range (such as propylene / propane (C3) splitters, deethanizers, depropanizers, debutanizers, isobutylene / isobutane splitters, 1-butene fractionators, deisobutanizers, deisopentanizers, C5 splitters, C6 fractionators, naphtha splitters, benzene / toluene fractionators, process water degassers, and acid gas degassers) as well as process heaters, endothermic chemical reactions, equipment heat tracing in process operations above ambient conditions, boiling, solvent evaporation, and (process and / or effective) steam generation.

[0008] Although conventional fossil fuel energy sources can be used for heating, the external energy used in the systems and methods of the present invention is preferably or includes electricity from a renewable or non-CO2 emitting energy source. Examples include wind turbines, photovoltaics, solar thermal, hydroelectric, geothermal, nuclear, or any other non-CO2 emitting or reduced CO2 emitting energy source (reduced relative to conventional fossil fuel sources). The combination of energy sources can be achieved by actual connection or by constraints. For example, direct solar thermal energy can be used to replace an electric heater, and / or direct mechanical work input (e.g., shaft work from a turbine) can be used to replace an electric motor driven heat pump. In some embodiments of the system of the present invention for storing and releasing thermal energy for heating in a chemical plant process, the system includes: a phase change material (PCM) comprising a volume; a heat source configured to transfer thermal energy to the PCM; and a heat exchange system configured to transfer thermal energy from the PCM to the process; wherein the PCM is configured to transition from a first state (e.g., solid) to a high enthalpy second state (e.g., liquid) at a transition temperature equal to or greater than an effective temperature of the process; and wherein the PCM requires at least 2 MWh (e.g., greater than any of the following or between any two of the following: 2 MWh, 5 MWh, 10 MWh, 20 MWh, 25 MWh, 50 MWh, 100 MWh, 150 MWh, 200 MWh, 500 MWh) to transition from the first state to the second state.

[0009] In some systems of the present invention, the heat exchange system includes a heating loop configured to circulate a heat transfer fluid in thermal communication with the PCM such that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to the process.

[0010] In some systems of the present invention, the heat source comprises an electric heater. Some such systems are configured to alternate between a charging cycle, during which the electric heater provides thermal energy to the process, and a discharge cycle, during which the heat exchange system transfers thermal energy from the PCM to the process. In some such systems, during the charging cycle, the electric heater provides thermal energy to both the PCM and the process.

[0011] In some systems of the present invention, the heat source comprises a heat pump. In some such systems, the heat pump is configured to receive waste energy from the process or a different process in the chemical plant. Some such systems further comprise: an electric heater configured to provide thermal energy to the process, wherein the system is configured to alternate between a charging cycle during which the electric heater provides thermal energy to the process and a discharge cycle during which the heat exchange system transfers thermal energy from the PCM to the process.

[0012] In some systems of the present invention, the heat source configured to transfer thermal energy to the PCM is a first heat source, and the system further includes a second heat source configured to transfer thermal energy to the chemical process.

[0013] In some configurations of the method of the present invention for storing and releasing thermal energy for heating a chemical plant process, the method includes: circulating a heat transfer fluid in thermal communication with a phase change material (PCM) during an energy release cycle so that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to the process; wherein the PCM is configured to transition from a first state (e.g., solid) to a high enthalpy second state (e.g., liquid) at a transition temperature that is higher than the maximum operating temperature of the process; and wherein the PCM is configured to transfer at least 2 MWh (e.g., greater than any of the following or between any two of the following: 2 MWh, 5 MWh, 10 MWh, 20 MWh, 25 MWh, 50 MWh, 100 MWh, 150 MWh, 200 MWh and / or 500 MWh) of energy to the heat transfer fluid during a single energy release cycle.

[0014] Some methods of the present invention further include: transferring thermal energy from a heat source to the heat transfer fluid during the charging cycle. In some such methods, a 24-hour period includes one or more energy release cycles lasting a total of 2-22 hours, and one or more recharging cycles lasting a total of 2-22 hours. In some such methods, the lengths of the charging cycle and the energy release cycle are adjusted or selected in response to a request from a grid operator to reduce electrical energy consumption. In some such methods, the lengths of the charging cycle and the energy release cycle are selected to reduce the total electricity cost of continuously running the process over a 24-hour period, taking into account changes in electricity prices over a 24-hour period. In some such methods, the initiation and length of the operation of the energy release cycle are determined in response to a temporary interruption of at least one power source for the process.

[0015] In certain embodiments, a system for storing and releasing thermal energy for heating in a process at a chemical plant may include: a phase change material (PCM) comprising a volume; and a heat exchange system configured to transfer thermal energy from the PCM to one or more of chemical reactants, chemical intermediates, or chemical products; wherein the PCM is configured to transition from a first state to a second state of high enthalpy at a transition temperature equal to or greater than the process temperature of the associated chemical reactants, chemical intermediates, or chemical products; and wherein the PCM requires at least 2 MWh to transition from the first state to the second state.

[0016] In certain embodiments, thermal energy may be transferred to the PCM from one or more of a chemical reactant, a chemical intermediate, or a chemical product stream. The heat exchange system may include a heating circuit configured to circulate a heat transfer fluid that is thermally connected to the PCM so that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to one or more of the chemical reactants, chemical intermediates, or chemical products. The heat source may include an electric heater. The system is configured to alternate between a charging cycle and a release cycle, during which the electric heater provides thermal energy to one or more of the chemical reactants, chemical intermediates, or chemical products, and during which the heat exchange system transfers thermal energy from the PCM to one or more of the chemical reactants, chemical intermediates, or chemical products. During the charging cycle, the electric heater may provide thermal energy to the PCM and one or more of the chemical reactants, chemical intermediates, and / or chemical products.

[0017] In certain embodiments, the heat source may include a heat pump, wherein the heat pump may be configured to receive waste energy from a process or a different process in a chemical plant.

[0018] In certain embodiments, the material production rate of the chemical plant can be maintained at a constant level regardless of whether the PCM is in the first state or the second state.

[0019] Certain embodiments may include an electric heater configured to provide thermal energy to a chemical process; wherein the system is configured to alternate between a charging cycle, during which the electric heater provides thermal energy to one or more of the chemical reactants, chemical intermediates, or chemical products, and a discharge cycle, during which the heat exchange system transfers thermal energy from the PCM to one or more of the chemical reactants, chemical intermediates, or chemical products.

[0020] In certain embodiments, the heat source that may be configured to transfer thermal energy to the PCM is a first heat source, and the system further includes a second heat source that is configured to transfer thermal energy to the chemical process.

[0021] Certain embodiments may include a method for storing and releasing thermal energy for heating in a chemical plant process, the method comprising: circulating a heat transfer fluid in thermal communication with a phase change material (PCM) during an energy release cycle, such that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to one or more of chemical reactants, chemical intermediates, or chemical products; wherein the PCM is configured to transition from a first state to a high enthalpy second state at a transition temperature that is higher than an associated process temperature, which in some cases may be the maximum operating temperature of one or more of the chemical reactants, chemical intermediates, or chemical products, and in other cases may be an effective temperature; and wherein the PCM is configured to transfer at least 2 MWh of energy to the heat transfer fluid during a single energy release cycle.

[0022] In certain embodiments, during the charging cycle, thermal energy is transferred from the heat source to the heat transfer fluid. A 24-hour period may include one or more energy release cycles lasting a total of 2-22 hours and one or more recharging cycles lasting a total of 2-22 hours. The lengths of the charging cycle and the energy release cycle may be adjusted or selected in response to a request from a grid operator to reduce electrical energy consumption. The lengths of the charging cycle and the energy release cycle may be selected to reduce the total electricity cost of continuously operating a chemical process at a stable material production rate over a 24-hour period, while taking into account price changes in electricity over a 24-hour period. The initiation and length of the operation of the energy release cycle may be determined in response to a temporary interruption of at least one power source for the process.

[0023] The term "coupled" is defined as connected, although not necessarily directly, and not necessarily mechanically; two items that are "coupled" may be unified with each other. Unless otherwise expressly required by the present disclosure, the terms "one" and "an" are defined as one or more. The term "substantially" is defined as most but not necessarily all of the content referred to (and includes the content referred to; for example, substantially 90 degrees includes 90 degrees, and substantially parallel includes parallel), as understood by one of ordinary skill in the art. In any embodiment of the apparatus, kits and methods of the present invention, the term "substantially" can be replaced with "within [percentage]" of the specified content, where the percentage includes 0.1%, 1%, 5% and / or 10%.

[0024] The terms "comprise" (and any form of "including", "have" (and any form of "having"), "include" (and any form of "including"), and "contain" (and any form of "containing") are open-ended linking verbs. Thus, a device or kit that "comprises," "has," "includes," or "contains" one or more elements has the one or more elements, but is not limited to having only these elements. Similarly, a method that "comprises," "has," "includes," or "contains" one or more steps has the one or more steps, but is not limited to having only the one or more steps.

[0025] Furthermore, a device, apparatus, or system that is configured in a certain way is configured in at least that way, but it may also be configured in ways other than those specifically described.

[0026] Any embodiment of any of the apparatus and methods of the present invention may consist of or consist essentially of, rather than include / comprise / contain / have: any of the described steps, elements and / or features. Thus, in any of the claims, the term "consisting of" or "consisting essentially of" may replace any of the above open-ended linking verbs to alter the scope of a given claim if the open-ended linking verbs were used.

[0027] Details related to the above-described embodiments and other embodiments are given below.

[0028] Some details related to aspects of the present disclosure are described above, and other details are described below. Other embodiments, advantages, and features of the present disclosure will become apparent after reviewing the entire application, including the brief description of the figures, detailed description, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following figures are provided for illustration only and are not intended to limit the present disclosure. For the sake of brevity and clarity, each feature of a given structure is not always labeled in each figure in which the structure appears. The same label or reference number does not necessarily represent the same structure. On the contrary, the same reference number can be used to indicate similar features or features with similar functions, as can different reference numbers. The drawings of specific dimensions are drawn to scale (unless otherwise specified), which means that the dimensions of the elements shown are accurate relative to each other, at least for the embodiments shown in the figures.

[0030] Figure 1 A flow chart showing an embodiment of the method of the present invention is shown.

[0031] Figure 2A and 2BThe conceptual block diagrams of the first embodiment of the PCM energy storage system combined with a chemical process of the present invention are shown during a charging cycle and a discharging cycle, respectively.

[0032] Figure 3A and 3B A conceptual block diagram of a second embodiment of the present invention in combination with a PCM energy storage system and a chemical process during a charging cycle and a discharging cycle is shown respectively.

[0033] Figure 4A and 4B A conceptual block diagram of a third embodiment of the present invention combining a PCM energy storage system and a chemical process during a charging cycle and a discharging cycle is shown respectively.

[0034] Figure 5A and 5B A conceptual block diagram of a third embodiment of the present invention combining a PCM energy storage system and a chemical process during a charging cycle and a discharging cycle is shown respectively.

[0035] Figure 6 A composite curve is shown which conceptually illustrates the waste heat from a chemical process that is available for upgrading.

[0036] Figure 7 A block diagram is shown that conceptually illustrates the use of a heat pump to upgrade waste heat from a chemical process.

[0037] Figure 8 A block diagram is shown that conceptually illustrates the use of a heat engine to utilize waste heat from a chemical process. Fig.9A and 9B Composite curves are shown separately, which conceptually illustrate the charging state and the de-energizing state of the PCM using high temperature process heat.

[0038] Fig. 10A and 10B An embodiment of a packaged PCM configuration is shown.

[0039] Fig.11 A process schematic diagram of one embodiment of a conventional C4 splitter distillation column is shown.

[0040] Fig.12 The conventional heat pump is shown. Fig.11 A process schematic diagram of another embodiment of a C4 splitter distillation column.

[0041] Fig.13 Shows the use of heat pump and PCM energy storage system to achieve Fig.12 A process schematic diagram of another embodiment of a C4 separator tower.

[0042] Fig.14A and 14BA process schematic diagram of another embodiment of the PCM system of the present invention is shown, which uses high-temperature process heat to charge the PCM, and shows the charging process and the energy release process respectively. DETAILED DESCRIPTION

[0043] Referring now to the drawings, and in particular to Figure 1 and Figures 2A to 2B , Figure 1 A flow chart showing an embodiment 10 of the method of the present invention for using phase change materials for heating cycles in chemical processes in chemical plants, and Figure 2A and 2B shows that in the charging cycle ( Figure 2A ) and energy release cycle (2B) during the PCM 104 such a PCM energy storage system 100 and the chemical process 108 in the chemical plant conceptual block diagram of an embodiment. In some embodiments, Figure 1 The method or process shown in is implemented by a digital controller such as a processor, which executes instructions from a memory to implement the following reference Figure 1 The steps described in Figure 2A and 2B In an embodiment, a common electric heater 112 (eg, one or more electric heaters with heat greater than that required by the chemical process alone) provides thermal energy to operate the chemical process 108 and to charge the PCM 104 .

[0044] In this article, "chemical plant" means a manufacturing process for producing desired molecular products. Non-limiting examples of chemicals may include, but are not limited to, ammonia, methanol, hydrogen, ethylene, propylene, high hydrocarbon chain length olefins, ethylene glycol, butadiene, MTBE, benzene, p-xylene, phenol, bisphenol A, ethanol and high carbon alcohols, acetic acid and high hydrocarbon acid (e.g., terephthalic acid) and polymers thereof. The output of a chemical plant may be a material product. A chemical plant is different from an energy production facility or an energy cooperative. Although chemical plants can produce a certain amount of energy, they also produce desired molecular products as described above. In this article, energy is not considered to be a "material product" or a "molecular product."

[0045] In order to optimize the profitability of a chemical plant, it is usually best to maximize the utilization of the core equipment of the plant itself by maintaining the maximum product output as much as possible, thereby maximizing the capital efficiency and economic benefits of the plant as a whole. Chemical plants may also have certain technical issues, such as operating windows of reactors, distillation columns and other unit operations, which limit the flexibility of adjusting the production rate or bring serious consequences due to deviations from the optimal design. For example, even after a short temporary shutdown, safety protocols and equipment protection procedures may require a day or more to restore the full operation of the plant. Therefore, an object of the present invention is to operate a chemical plant with a constant or substantially constant output (material production rate) under the condition of varying or selectable energy input. In contrast, power generation systems can utilize certain types of energy storage devices, but the purpose is to extend the duration of the energy system or to time-shift the output of the energy delivery system by modulating the total output over time. In these cases, the process output (e.g., electrical energy or thermal energy) is variable. However, in an embodiment of the present invention, the process material output can be maintained at a designed constant rate. For commercial chemical plants, the stored energy must be sufficient.

[0046] In an initial step 14, PCM 104 is "charged" by adding thermal energy to the PCM. In at least some embodiments, sufficient thermal energy is added to liquefy at least some of the PCM, e.g., to cause the PCM to transition from a solid state to a liquid state. Figure 2A As shown by the solid arrows in FIG. 1 , during PCM charging, a conventional electric heater 112 is used to add thermal energy to the PCM 104 and the chemical process 108 . Figure 2A The dashed arrows in represent an alternative mode in which thermal energy is transferred from the PCM 104 to the chemical process 108 when the PCM is charged.

[0047] At step 18, the method involves determining whether a release triggering event has occurred. Such a release triggering event may be or include, for example, reaching a time at which the PCM 104 is scheduled to "release" by releasing thermal energy to the chemical process 108, receiving a request from an operator of the power grid to reduce the power consumption of the power grid, observing a significant increase in the instantaneous cost of electrical energy supplied from the power grid, a predictive model indicating a significant increase in the cost of electrical energy in the future, or detecting an energy interruption from the power grid or from a local source (e.g., a renewable source or the combustion of fossil fuels). If the release triggering event has not occurred, the process may include determining whether the PCM is fully charged, and if not, returning to step 14 to continue charging the PCM. In some embodiments, the process includes adjusting the rate of charging of the PCM (i.e., the rate at which thermal energy is added to the PCM) based on the level of "charge" of the PCM. For example, the rate at which thermal energy is added to the PCM may be slowed as the PCM approaches a fully charged state. In some implementations, if the PCM is fully charged, the liquefied or “charged” state of the PCM is maintained by continuing to add thermal energy to the PCM at a rate close to the rate at which the PCM releases thermal energy to the environment (eg, due to inherent insulation limitations).

[0048] If, on the other hand, the discharge triggering event has occurred, the method proceeds to step 22 where the PCM is discharged via releasing thermal energy to the chemical process (e.g., via circulating a fluid in thermal communication with the chemical process and the PCM). Figure 2B As shown by the solid arrow in , thermal energy from the PCM in 104 is used for heating in the chemical process 108. In at least some examples or embodiments, the electric heater 112 can be completely turned off so that all heating for the chemical process is provided by releasing thermal energy to the chemical process via the PCM. In some embodiments, such thermal energy transfer from the PCM to the chemical process can be direct (e.g., placing a fluid of the chemical process in direct thermal communication with the PCM) or indirect (e.g., transferring the fluid of the chemical process by placing the fluid of the chemical process in thermal communication with a heat transfer fluid that is transferred in direct thermal communication with the PCM). In this context, "direct thermal communication" means that there is no intermediate heat transfer fluid, and does not exclude thermal communication through an intermediate physical structure (e.g., a conduit for directing the flow of a process or heat transfer fluid) or through the wall of a container in which the PCM is arranged.

[0049] At step 26, the method involves determining whether a recharge triggering event has occurred. Such a recharge triggering event may be or include, for example, reaching a time at which the PCM 104 is scheduled to be "recharged" by adding thermal energy to the PCM, receiving an indication from a grid operator that higher power consumption of the grid may be restored, or the end of a period during which the operator requires a reduction in power consumption, observing a significant reduction in the instantaneous cost of electrical energy supplied from the grid, predictive models indicating significant reductions in future electrical energy costs, or detecting a restoration of the availability of energy from the grid or a local source (e.g., a renewable source or the combustion of a fossil fuel). If the recharge triggering event has not occurred, the process may include determining whether the PCM is fully discharged, and if not, returning to step 22 to continue discharging the PCM. In some embodiments, when sufficient energy is available (even if at a higher price), the process includes operating the electric heater 112 at a reduced rate (relative to the full or expected rate when the chemical process is running at a full or expected rate and discharging the PCM) to discharge the PCM based on (as determined by Figure 2B Thermal energy is added to the chemical process 108, to the PCM 104, or to both the chemical process and the PCM, for example, based on the "discharge" level of the PCM and / or based on the amount or cost of energy available from the grid or other source. For example, as the PCM approaches a fully discharged state, the rate at which thermal energy is released from the PCM to the chemical process may be slowed. In some embodiments, if the PCM is fully charged and energy is available from other sources (even at a higher price), the heater 112 is operated only to run the chemical process without charging the PCM. If a charging trigger event has occurred and sufficient energy is available from the grid or other source, the method returns to step 14, where the PCM is charged at a full or desired charging rate; or, if the available energy is greater than the energy required to run the chemical process, but there is not enough energy to charge the PCM at a full or desired charging rate, the PCM is charged at a reduced rate (relative to the full or desired charging rate).

[0050] Figure 3A and 3B 1 and 1 are conceptual block diagrams of an alternative configuration 100a of the PCM energy storage system combined with a chemical process of the present invention during a charging cycle and a discharging cycle, respectively. The operation of configuration 100a is substantially similar to the operation of configuration 100 ( Figures 2A to 2B ), the main difference is that configuration 100a includes an additional PCM electric heater 116, which has its own heater or heaters. Figure 1 At step 14 of the illustrated method, when implemented by configuration 100a, heater 112a adds thermal energy to chemical process 108, and PCM heater 116 adds thermal energy to PCM 104 to charge the PCM. Figure 1At step 22 of the method shown, the PCM releases energy by releasing heat energy from the PCM to the chemical process 108, such as Figure 3B Additional process heat may optionally be provided by a process heater 112a, such as Figure 3B In at least some embodiments or implementations, the process heater 112a and the PCM heater 116 can be completely turned off so that all heat energy for the chemical process is provided by the PCM releasing heat energy to the chemical process, and so that heat energy is not added to the PCM at the same time. Figure 2A-2B In configuration 100, in some embodiments, such thermal energy transfer from the PCM to the chemical process can be direct (e.g., by directly thermally connecting the fluid of the chemical process to the PCM) or indirect (e.g., by directly thermally connecting the fluid of the chemical process to the PCM, which in turn is thermally connected to the fluid of the chemical process).

[0051] As mentioned above Figure 2A-2B In the configuration 100 of 100a, in some embodiments, when sufficient energy is available (even if more expensive), the method includes operating the process heater 112 at a reduced rate (relative to the full or expected rate when the chemical process is operated with only the electrical heater) to add thermal energy to the chemical process 108, operating the PCM heater 116 at a reduced rate (relative to the full or expected rate when the PCM is charged at the full or expected rate) to add thermal energy to the PCM 104, and / or operating the process heater at a reduced rate and operating the PCM heater at a reduced rate (such as Figure 3B In some embodiments, if the PCM is fully charged and energy is available from another source (even if more expensive), only the process heater 112 is operated to run the chemical process, and the PCM heater 116 is not operated to charge the PCM.

[0052] Figure 4A and 4B 1 and 10 show a conceptual block diagram of an alternative configuration 100b of the PCM energy storage system combined with a chemical process of the present invention during a charging cycle and a discharging cycle, respectively. The operation of configuration 100b is substantially similar to the operation of configuration 100 ( Figures 2A to 2B ), the main difference is that configuration 100b uses an electric heat pump 120 instead of an electric heater. Figure 1 At step 14 of the illustrated method, when implemented by configuration 100b, the heat pump 120 adds thermal energy to the chemical process 108 and adds thermal energy to the PCM 104 to charge the PCM. Figure 1 At step 22 of the method shown, the PCM releases energy by releasing heat energy from the PCM to the chemical process 108, such as Figure 4BDuring the PCM release by the heat pump 120, additional process heat may optionally be provided, such as Figure 4B 108. During the discharge of PCM 104, in at least some embodiments or implementations, heat pump 120 may be completely shut down so that all heating for the chemical process is provided by the PCM releasing heat energy to the chemical process and so that heat energy is not simultaneously added to the chemical process by the heat pump. Figure 2A-2B In the configuration 100, in some embodiments, such thermal energy transfer from the PCM to the chemical process can be direct (e.g., by placing the fluid of the chemical process in direct thermal communication with the PCM) or indirect (e.g., by placing the fluid of the chemical process in direct thermal communication with the PCM, and a heat transfer fluid in turn in thermal communication with the fluid of the chemical process). Figure 4A As shown by the arrows in (and Figure 4B As shown by the corresponding dotted arrow in FIG, the heat pump 120 can receive waste heat (excess heat energy with a temperature too low to be directly reused) from a chemical process or other sources other than a chemical process, and upgrade the waste heat to a temperature at which the corresponding heat energy can be used to charge the PCM.

[0053] Using a heat pump to upgrade waste heat to a temperature that can be used to provide thermal energy to a chemical process and charge the PCM can be operated with lower power requirements than electric heaters due to the coefficient of performance of the heat pump. For example, the heat pump can be graded at different temperature levels to account for the difference in temperature required to heat the process versus heating the PCM, each of which requires a temperature higher than the chemical process to transfer thermal energy to the process, and a temperature higher than the PCM when adding thermal energy to the PCM.

[0054] Figure 5A and 5B 1 and 10. The conceptual block diagram of an alternative configuration 100c of the PCM energy storage system combined with a chemical process of the present invention is shown during a charging cycle and a discharging cycle, respectively. The operation of configuration 100c is substantially similar to that of configuration 100a ( Figures 3A to 3B ), the main difference is that configuration 100c uses an electric heat pump 120b to charge the PCM instead of an electric heater. Figure 1 At step 14 of the illustrated method, when implemented by configuration 100c, heater 112b adds thermal energy to chemical process 108, and PCM heat pump 120b adds thermal energy to PCM 104 to charge the PCM. As indicated by the arrow pointing to heat pump 120b, heat pump 120b can receive waste heat (excess heat that is too low to be directly reused) from a chemical process or other source other than a chemical process, and upgrade the waste heat to a temperature at which the corresponding thermal energy can be used to charge the PCM.

[0055] Likewise, in Figure 1At step 22 of the method shown, the PCM releases energy by releasing heat energy from the PCM to the chemical process 108, such as Figure 5B Additional process heat may optionally be provided by a process heater 112b, such as Figure 3B 108 is shown by the dashed line from the heater 112b to the chemical process 108. In at least some embodiments or implementations, the process heater 112b and the heat pump 120b can be completely shut down so that all thermal energy for the chemical process is provided by the PCM releasing thermal energy to the chemical process, and so that thermal energy is not simultaneously added to the PCM. In some embodiments, the use of the electric process heater 112b and the PCM electric heat pump 120b can be interchanged or swapped so that the heat pump (rather than the electric heater) is primarily used to heat the chemical process, and the electric heater (rather than the heat pump) is primarily used to charge the PCM. The choice of configuration will depend on the amount of waste heat and its temperature level relative to the process energy requirements, as well as the expected energy availability and electricity pricing profile. As described above Figure 2A-2B In the configuration 100 in, in some embodiments, such heat energy transfer from the PCM to the chemical process can be direct (e.g., placing the fluid of the chemical process in direct thermal communication with the PCM) or indirect (e.g., transferring the fluid of the chemical process by placing the fluid of the chemical process in thermal communication with a heat transfer fluid that is directly thermally connected to the PCM). As shown by the dashed arrow pointing to the heat pump 120b, the heat pump 120b can also optionally receive waste heat from the chemical process or other sources other than the chemical process during the discharge of the PCM, and upgrade the waste heat to a temperature at which the corresponding thermal energy can be used to charge the PCM. The waste heat may come from the chemical process, or from an external process, not shown in the figure.

[0056] Although Figure 1 Process Examples and Figures 2A to 2B , 3A to 3B, 4A to 4B, and 5A to 5B use a single PCM, but the methods and systems of the present invention may include multiple PCMs (e.g., at different temperatures), such as two PCMs with different freezing temperatures, or three PCMs with three different freezing temperatures, for example, to provide graded heating for different process services. Although Figures 2 to 5 show a single arrow for the transfer of process heat (thermal energy) from the PCM 104 to a single chemical process 108, process heat may be transferred from the PCM to multiple chemical processes and / or other heat uses. For example, process heat may be supplied to different processes or uses at more than one location in a plant, even at different use temperatures (within the limits of the PCM heat supply, electric heater supply, or heat pump supply). In addition, the thermal energy stored in the PCM may also be exported outside the boundaries of the chemical plant to other energy consumers, such as other chemical plants located nearby. Although Figures 4A to 4B and Figures 5A to 5BThe system embodiments show a single heat pump, but each may include cascaded heat pumps to raise different portions of the upgraded heat to different temperature levels, or multiple heat pumps to raise heat from multiple input temperatures to multiple output temperature levels to match supply heat availability and process heating requirements.

[0057] Figure 6 and 7 It is helpful to illustrate the operation of a heat pump in the systems and methods of the present invention. Figure 6 shows a large composite curve conceptually illustrating the waste heat from chemical processes available for upgrading, and Figure 7 A block diagram is shown that conceptually illustrates the use of a heat pump to upgrade waste heat from a chemical process. Specifically, Figure 6 A large composite process heating and cooling curve is shown, which represents the net amount of heat input into the process and at what temperature the heat is required. As shown, such processes typically have a "pinch temperature" whose value is unique to the process and depends on the reasonable limit of heat transfer that occurs in the process (i.e., the lowest temperature driving force for heat transfer). At the pinch temperature, the net heating and cooling demand is zero. Just above the pinch temperature, all heat from the "hot stream" (the object that needs to release heat energy or be cooled in the process) can be completely absorbed by the "cold stream" (the object that needs to absorb heat energy or be heated). Further, above the pinch temperature, additional heat or thermal energy is required to meet the total heating demand of the process. Below the pinch temperature, there is excess heat or thermal energy that needs to be removed from the hot stream that exceeds the amount absorbed by the cold stream, and therefore, a net cooling effective temperature demand is required below the pinch temperature. The heat energy removed below the pinch temperature is at too low a temperature to be used at a pinch temperature above where there is a net heating demand. The heat or thermal energy removed below the pinch temperature may be referred to in the art as "waste heat" because it cannot be used directly in the process. Therefore, if this waste heat is to be used, it is usually exported to an adjacent chemical plant or process for use. Most commonly, in prior art systems, the waste heat has been rejected to the environment.

[0058] Figure 6 An example includes 15 MW of waste heat from a pinch temperature below 155°C; if a heat pump is used to upgrade this waste heat to above 200°C, the net effective demand of the process can be offset by 15 MW. Figure 7The conceptual heat pump shown can make the utilization of waste heat within a process feasible. Heat pumps are known in the art and can be based on vapor compression, thermoelectricity, pressure sensitive chemical reactions, etc. The effect of the functional energy input into the heat pump is to upgrade the waste heat to a temperature high enough for use by the process. Specifically, the heat pump effectively upgrades the waste heat from below the pinch point temperature to above the pinch point temperature. In the systems and methods of the present invention utilizing PCM, the waste heat is upgraded to a sufficiently high temperature so that it can be transferred to a PCM thermal storage system and subsequently transferred to the process. In addition, the storage device provided by the PCM effectively separates the time of using the upgraded waste heat from the act of upgrading the waste heat, which means that the waste heat can be upgraded and the PCM can be optionally recharged when electricity is cheaper.

[0059] In practice, the energy input to the heat pump is also usually available at a usable (upgraded) temperature, and therefore can also be used to provide thermal energy for the process. Examples of waste heat sources in chemical processes include cooling water cooling in ethylene plants, overhead condensers in distillation towers, circulating gas coolers in polyolefin plants, excess or discharged steam in user-constrained steam systems (usually with thermal power integration), product process coolers, low-temperature reactor coolers in BPA, oxygen alcohol processes, and methyl tertiary butyl ether (MTBE) processes, etc. In addition, such waste heat can come from a single stream or gather from multiple waste heat sources. The waste heat utilized by a heat pump can originate from the same chemical process or another process.

[0060] Figure 8 A block diagram is shown that conceptually illustrates the use of a heat engine to utilize waste heat from a chemical process. In some configurations of the systems and methods of the present invention, such a heat engine can be used in conjunction with a PCM and a heat pump. For example, a heat pump can supply thermal energy to charge the PCM depending on whether the source of the heat is above or below the process pinch temperature. A heat engine can be included to generate energy using thermal energy flowing to or from a PCM, where the direction of flow depends on whether a given temperature is above or below the process pinch temperature. Another way in which the systems and methods of the present invention can be implemented is to charge the PCM using high temperature heat generated by processes within the plant above the freezing point of the PCM (e.g., from an exothermic chemical reaction (e.g., ethylene oxidation, oxidized butane dehydration, or other oxidation reactions), a high temperature reactor outlet water cooler, or cooling furnace flue gas). When charging the PCM, low temperature auxiliary heating (a heat pump or an electric heater) provides heat to the chemical process driven by the PCM during the discharge of the PCM. When the PCM is discharged, the available high temperature process heat can be applied to lower temperature applications in the process; for example, as Fig. 9B As shown, high temperature process heat as well as thermal energy from deenergizing the PCM can be transferred simultaneously to the target chemical process. Fig.9A (Charge Mode) and Fig. 9BThe total composite curve shown in (Energy Release Mode) illustrates this conceptually. The advantage of this type of implementation is that the natural temperature gradient of the chemical process can be used. One benefit is that the effective heat supply (e.g., electric heater) can be rated at a lower temperature than what would be required to charge the PCM. At some temperatures, such as at medium voltage (3000V to 7000V) heaters are challenging, and it is necessary to use lower voltages (e.g., 1000V or less) to prevent arcing within the system, which can save equipment costs. Low voltage equipment requires more current to meet the same energy demand, so wiring and power supply items (such as additional transformers) increase costs.

[0061] Phase Change Materials (PCM)

[0062] Phase change materials are generally capable of absorbing or releasing (preferably large amounts) of heat at a specific target temperature, and, at least for some embodiments of the systems and methods of the present invention, preferably with minimal volume change. Typically, physical phase changes of condensed phase materials exhibit this type of behavior. The transition from a solid phase to a liquid phase is a typical transition that meets this criterion. However, other transitions may also be utilized in certain embodiments of the systems and methods of the present invention. For example, under the operating conditions (e.g., temperature) of certain embodiments, some PCMs may change from a solid state to a liquid state. By further example, some PCMs may exhibit other types of phase transitions in which enthalpy changes nonlinearly at a specific temperature (or within a specific temperature range), such as from one solid state to another solid state (e.g., changes in crystal structure due to molecular reorganization), from an amorphous state to a solid state, from a gel state to a solid state, from a liquid state to a gel state, or from an amorphous state to a different amorphous state. In a multi-component mixture, there may or may not be some component transfer between one state and another, such as a liquid solution of a solvent and a solute forming a 2:1 solvent and solute compound in a solid phase. To describe this generally, without enumerating all of the specific phases of the many possible systems, a PCM can be described as transitioning from a first state to a second state of higher enthalpy when heat is added to the PCM, and from the second state to the first state of lower enthalpy when heat is removed from the PCM.

[0063] Various materials and mixtures can be used for PCM, such as, for example, polyaromatic hydrocarbons, organic acids, alcohols with aromatic rings, or inorganic mixtures, anthracene (melting point of 216°C, heat of fusion of about 30 kJ / mol or 168 kJ / kg), benzoic acid (melting point of 122°C, heat of fusion of about 18 kJ / mol or 147 kJ / kg), hexamethylbenzene (165°C, 20.6 kJ / mol, 127 kJ / kg), tetraphenylmethane (1,1',1",1"'-methanetetraethyltetraphenyl) (281°C, 48.3 kJ / mol, 150 kJ / kg), triacontan (melting point of 66°C, heat of fusion of 68.8 kJ / mol or 136 kJ / kg), and paraffin (usually melts between 46°C and 68°C). Various salts may be used in the molten salt solution, such as, for example, potassium nitrate (KNO3), sodium nitrate (NaNO3), sodium nitrite (NaNO2), other Group I and Group II metal halides, Group I and Group II metal nitrates, Group I and Group II metal carbonates, Group I and Group II metal sulfates, and mixtures thereof, eutectic salt mixtures, such as LiNO3 / NaCl (melting point 208°C, heat of fusion of about 369 kJ / kg), various commercially available eutectic salt solutions (e.g., HITEC, from Coastal Chemical, melting point 142°C), and combinations thereof. In addition, certain configurations of the present PCM may include one or more metals because of their good volumetric heat storage density. For example, zinc (which has a melting point of 420°C, heat of fusion of 112 kJ / kg, and a solid density of 7140 kg / m 3 ) has 0.22MWh / m 3 The thermal energy storage density of PCM is similar to that of NiMH batteries and slightly higher than that of Ni-Cd batteries. By further example, the melting temperature of magnesium is 650°C and the heat of fusion is 349 kJ / kg; the melting temperature of bismuth is 272°C and the heat of fusion is 54 kJ / kg; and the melting temperature of tin is 232°C and the heat of fusion is 59 kJ / kg. In addition, different PCM components can be mixed in proportion to achieve the desired freezing point for a given heating application. In general, for binary mixtures, when one substance is added to mix with another pure substance, its freezing point is lowered. Eutectic mixtures, coincident melting point mixtures, and mixtures with solid compounds are convenient to use because their composition does not change when the mixture is thawed and frozen. Aqueous mixtures can be used. The magnesium nitrate salt solution can be used in the form of hexahydrate (melting point around 90°C), Mg(NO3)2 and its dihydrate eutectic (melting point 129°C) or dihydrate and hexahydrate eutectic (melting at 50°C). The sodium hydroxide water eutectic mixture freezes at 62°C. When the amount of solubility depends strongly on the temperature, aqueous organic solutions are more preferred. An example is an aqueous mixture of terephthalic acid and water. When pressure is applied, the water is prevented from evaporating and the mixture can be used up to 300°C.

[0064] There are several options for including the PCM in the systems and methods of the present invention. First, the PCM can be disposed in one or more insulated containers through which heat exchange conduits define a flow path for the fluid. Conduits (e.g., tubes, shells, fins, or connectors) disposed within the containers allow heat transfer between the working heat transfer fluid within the conduits or heat exchangers and the PCM within a given container (outside the conduits). In at least some configurations, the PCM is stirred or agitated within the container to prevent temperature gradients and improve heat transfer. In the first option, the volume of the PCM will generally exceed the minimum requirement to achieve the required heat capacity because a consistent liquid phase is generally required to promote stirring or agitation during the "energy release" of the PCM to promote consistent transfer of heat energy from the PCM. For example, the PCM can be suspended in a liquid (i.e., a suspension in which the PCM is in solid form). The relative proportions of liquid and solid can be designed according to the needs of the system. For example, a relatively large passive storage system may have continuous and somewhat separated solid and liquid phases. The stirring or agitation system can be configured to control the PCM in a suspension of smaller particles that are easily pumped and transferred to the heat transfer equipment, or simply suspended by fluid circulation to homogenize the system with heat storage capacity. In some embodiments, for example, the PCM can be in the form of small encapsulated beads containing the PCM in its two utilized states (e.g., liquid and solid) so that the beads can be suspended in a liquid with a freezing point lower than the PCM. When the PCM is suspended in solution as a suspension or as an emulsion (e.g., in a diphenyl oxide / biphenyl mixture, or other commercial heat transfer fluids), the PCM is not encapsulated and a nucleating agent can be added to the liquid to promote nucleation in the solution during freezing rather than nucleation on the heat transfer surfaces, where nucleation would interfere with or inhibit the transfer of thermal energy through those surfaces. Some such systems and methods may include subcooling or cryogenic cooling before nucleation / crystallization occurs, in which case the temperature of the PCM must be additionally above the process temperature by the amount of subcooling to maintain the heat transfer temperature driving force. Nucleating agents help reduce the cryogenic cooling required before freezing begins. Another way to avoid the operability problems associated with cryogenic cooling is to maintain enough solid PCM in the system so that when energy is released there is surface area for crystal growth.

[0065] A second option involves containing the PCM in a large number of relatively small thermally conductive containers (e.g., containers made of HDPE or aluminum or stainless steel). These containers can be molded individually or in combination with other such containers to shape the contours of the conduit to improve heat transfer between the chemical process stream or heat transfer fluid to be heated and the PCM. For example, for a conduit having a circular cross-section like a typical pipe, the container can include circular channels or semi-circular indentations to contact the conduit. By further example, the conduit can be molded to have a relatively flat rectangular cross-section that is sized to fit within the planar wall of the container.

[0066] In a third option, the PCM may be contained in multiple plastic or metal housings whose geometry is selected so that the housings are stacked or suspended (e.g., in parallel) within an insulated container so that the fluid to be heated or heat transfer fluid (when a secondary loop system is employed) can pass between (and / or through) the individual containers and contact a single container to transfer thermal energy between the PCM and the fluid to be heated or heat transfer fluid through the container walls. This approach provides a large surface area for the transfer of thermal energy. Fig. 10A An example of such a container is shown, which is formed from a polymer and is substantially rigid to allow multiple containers to be stacked. Fig. 10A The container defines a plurality of grooves to maximize the surface area available for transferring thermal energy between the PCM within the container and a process or heat transfer fluid outside the container. Fig. 10B Another example of such a container is shown, which is formed of a polymer and is flexible (such as a plastic kitchen bag). As shown in the figure, Fig. 10B The container also defines a plurality of grooves along which two sides of the bag structure are connected to define elongated zigzag channels to maximize the heat transfer surface area, provide ease of bagging, and promote uniform distribution of the PCM within the bag structure when the bag structure is suspended in a vessel through which a process fluid or heat transfer fluid is circulated.

[0067] The first of the three PCM containment options offers the advantages of smaller overall vessel size, simpler construction, and higher heat transfer rates. The second of the three PCM containment options offers lower corrosion rates by completely containing the process or heat transfer fluid within the pipes and the PCM within a single vessel. The third of the three PCM options offers the advantages of large heat exchange area in a form factor that is convenient to handle.

[0068] Working fluid in heat pumps

[0069] Various fluids, steam or gases can be used to upgrade waste heat to useful heat for chemical process heating and / or PCM charging and releasing energy. Examples of such fluids suitable for certain embodiments of the method and system of the present invention include ethylene, propylene, ethane, propane, butane, ammonia, hydrocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, water, hydrogen, nitrogen, helium, argon, air and mixtures thereof. The heat pump cycle can be a known thermodynamic type, such as a Rankine cycle or a Stirling cycle (moving heat by running in a direction using input process work). A heat pump based on the operation of a reversible chemical reaction principle, i.e. a chemical heat pump, can also be used. The fluid can also be a solid or a polymer, such as a chemical heat pump material in some cases.

[0070] Heat transfer fluid

[0071] For configurations where the heat transfer fluid indirectly transfers thermal energy between the PCM and the fluid of a given chemical heating cycle, the heat transfer fluid may include one or more of any of the known components of such heat transfer fluids. Suitable heat transfer fluids are maintained in the liquid phase under the conditions of the relevant portion of the heating cycle and under the conditions under which heat transfer occurs between the heat transfer fluid and the PCM. Examples are numerous, but some common examples are eutectic mixtures of water, diphenyl oxide and biphenyl (e.g., Dowtherm A), mixtures with well-known trade names such as Dowtherm G and Therminol 66 heat transfer oils, and materials already available in chemical processes. When using a heat transfer fluid, the system may have several processes and tools interconnected to provide the energy required for the entire process. The heat transfer fluid may be heated by a combination of electric heaters, heat pumps, conventional combustion heaters, and process heat recovery. The heat transfer fluid may then be used as a general heating tool within the plant for one or more heating applications.

[0072] Example

[0073] Example 1: C4 Splitter with Electric Heater and PCM

[0074] An embodiment was modeled for the following: The PCM energy storage system and method of the present invention is used in the heating cycle of a C4 splitter that originally used an electric heater. Fig.11An example 200 of such a C4 splitter is shown, where a distillation column is used to separate a mixture of 60% isobutylene (-11.7°C normal boiling point) and 40% n-butane (-1°C normal boiling point), which is modeled in Aspen Plus software using an approximate thermodynamic model (Peng-Robinson equation of state with Aspen database parameters). As described above, the PCM storage device is "charged" by transferring thermal energy to the PCM, thereby melting at least a portion of the PCM, and the PCM storage device is "released" by transferring thermal energy from the PCM to a chemical process (reboiler) to freeze at least a portion of the PCM into a solid state. For example, the PCM of these modeled embodiments assumes that the compound undergoes a liquid-to-solid phase transition at a single temperature.

[0075] As shown in Table 1 below, the process is modeled using a "symmetric" cycle, where the "charging" cycle is equal in length to the PCM "discharging" cycle, and an "asymmetric" cycle, where the charging cycle is longer than the discharging cycle. Specifically, in the symmetric embodiment, the PCM is "charged" for 12 hours and "discharged" for 12 hours during each 24-hour period; and in the asymmetric embodiment, the PCM is charged for 16 hours and discharged for 8 hours during each 24-hour period. Thermal energy absorption from external (e.g., ambient) sources is not considered (assumed to be zero). In the design of real-world systems, such external thermal energy can be accommodated by enlarging the PCM volume and the thermal capacity of the heater and / or heat pump, given a specific insulation value. These models assume that the PCM is directly dispersed in a suspension or encapsulated in small spheres in a suspension.

[0076] As shown in the modeling, the feed stream 204 of the mixture is delivered to the distillation column 208 at a mass flow rate of 40 tons per hour, wherein the duty of the reboiler 212 is 18.9 MW. The separated fraction of n-butane leaves the column 208 at a mass flow rate of 16 tons per hour to the stream 216. The separated fraction of isobutylene leaves the column 208 and is concentrated to the stream 224 via the condenser 220 at a mass flow rate of 24 tons per hour.

[0077] For according to Fig.11 For the system of the configuration shown, the required electric heater size and PCM material mass / volume were calculated for two different (symmetric and asymmetric) charging and discharging cycles and are included in Table 1. Both were modeled assuming that during the PCM charging period, an electric heater with 95% efficiency was used to provide heat to meet the reboiler load, while during the PCM discharging period, the entire reboiler load was met by heat from the PCM. The modeling assumed that the phase change material was X70 PCM, available from Phase Change Material Products Ltd., with a melting point of 70°C and a density of 1.085 tons / m 3, latent heat is 0.16GJ / ton or 0.044MWh / ton. The model assumes a maximum solid content of 35% and a minimum residence time of 0.5 hours during operation. The heating cost calculation results are given for the following cases: 60$ / MWh during normal electricity consumption period and 90$ / MWh during peak electricity consumption period, where the charging time is during normal electricity consumption period and the discharging time is during peak electricity consumption period.

[0078] Table 1: Energy input and output of the electric heater PCM system

[0079]

[0080]

[0081] If a heat pump is used for the PCM system instead of a heater, the efficiency achieved will depend on the temperature of the available waste heat and the heat transfer temperature difference achieved, which will also depend on how closely the PCM freezing / melting temperatures match the process temperatures. Different heat pump configurations can be employed, such as using the process fluid or using an external working fluid. The source of the waste heat is related to the unit requiring the heat input, or it can also come from another part of the process.

[0082] Example 2 and Example 3: C4 Splitter with Electric Heater and PCM

[0083] An example was also modeled for the following: the PCM energy storage system and method of the present invention was used to run a heating cycle of a C4 splitter that originally used an electric heat pump. The C4 splitter conditions were the same as those in Example 1.

[0084] Example 2 simulates the use of a conventional heat pump in the system, and Example 3 simulates the use of a heat pump in combination with a PCM storage device, both for the case where the ratio of waste heat (from the final condenser as shown in the modeling) to heat input matches the peak / off-peak electrical load. Fig.12 shows the simulation results of Example 2, and Fig.13 Simulation results for a PCR heat pump are shown.

[0085] like Fig.11 and Fig.12 As shown in the modeling of , the mixed feed stream 204 is delivered to the distillation column 208 at a mass flow rate of 40 tons per hour, wherein the duty of the reboiler 212 is 18.9 MW. The separated fraction of n-butane leaves the column 208 to the stream 216 at a mass flow rate of 16 tons per hour.

[0086] like Fig.12As shown in the modeling of , in system 200a, the fraction of separated isobutylene (overhead vapor) leaves tower 208 along with additional fluids in the system and enters separator 228, where the stream is divided into a first stream 232 with a mass flow rate of 20 tons per hour and a second stream 236 with a mass flow rate of 226 tons per hour. Stream 236 enters compressor 240, where the temperature of the vapor is increased from 38°C to 63°C, and the vapor then enters heat exchanger 244, where the heat energy (18.2MW) is redirected (as shown by stream S6) to meet the duty of reboiler 212. The extraction of heat energy condenses the fluid stream from vapor to liquid and reduces its temperature from 63°C to 61°C, as shown at stream 248. Stream 248 then rejoins stream 232 at mixer 252, after which heat energy is extracted by heat exchanger 256 to completely condense the fluid to a full liquid stream. Then, pump 260 increases the pressure of the liquid stream from 5 bar to 8 bar, as shown, at which pressure the liquid stream reaches separator 264. At separator 264, the first liquid fraction of isobutylene is redirected to output stream 224 at a mass flow rate of 24 tons per hour, and the second liquid fraction is redirected to distillation column 208 at a mass flow rate of 222 tons per hour to mix with the feed stream in the distillation column.

[0087] Fig.13 system and Fig.12 The system is similar, but Fig.13 The system 200b includes an additional compressor stage to upgrade at least some of the waste heat from the overhead steam of the distillation column to a sufficiently high level so that the heat energy can be used to charge the PCM 202 before the overhead steam is condensed. More specifically, as Fig.13As shown in the modeling of , in system 200b, the separated fraction of isobutylene (overhead vapor) leaves column 208 along with the additional fluids in the system and enters compressor 240a, where the temperature of the vapor is increased from 38°C to 63°C, and the vapor then enters heat exchanger 244, where the heat energy (18.2MW) is redirected (as shown by stream S6) to meet the duty of reboiler 212. The extraction of heat energy condenses the fluid stream from vapor to liquid and reduces its temperature from 63°C to 61°C, as shown at stream 248a. Stream 248a is then directed to flasher 268, where the vapor portion of stream 248a is directed to second compressor 272, where the temperature of the vapor is increased from 61°C to 75°C, and then heat energy is extracted via heat exchanger 276 to completely condense the vapor into liquid stream 280, where the extracted heat energy is used to charge PCM 202. At the same time, pump 284 increases the temperature and pressure of liquid stream 288 from flasher 268 from 61° C. to 62° C. and from 9 bar to 13 bar, respectively. Stream 288 then rejoins stream 280 at mixer 252a, and the combined stream 292 then enters separator 264a, from which a first liquid fraction of isobutylene is removed to stream 224 at a mass flow rate of 24 tons per hour, and a second liquid fraction is redirected to distillation column 208 at a mass flow rate of 289 tons per hour to mix with the feed stream in the distillation column.

[0088] Table 2 lists some comparative results of Example 2 and Example 3. The ratio of peak to normal electricity cost required to make the heat pump-PCM system (Example 3) more attractive than the conventional heat pump (Example 2) is higher than the heater-PCM system of Example 1. However, the total amount of electrical energy required to be input in the Example 3 system is significantly less than the electric heater PCM embodiment, and the heat pump-PCM system has the additional benefit that the heat pump can be operated even during periods when the compressor of the heat pump cannot operate. Fig.12 (Example 2) and Fig.13 (Example 3) The size of the electric heat pump and the mass / volume of PCM material required were calculated and included in Table 2. Both were modeled assuming that during PCM charging, the motor efficiency was 95%, using the heat pump to provide heat to meet the reboiler load, and during PCM discharge, the heat from the PCM met the entire reboiler load. The modeling assumed that the phase change material was X70 PCM, available from PhaseChange Material Products Ltd., with a melting point of 70°C and a density of 1.085 tons / m 3, latent heat is 0.16GJ / ton or 0.044MWh / ton. The models assume a maximum solid content of 35% and a minimum residence time of 0.5 hours during operation. The heating cost calculation results are given for the following cases: 60$ / MWh during normal electricity consumption period and 90$ / MWh during peak electricity consumption period, where the charging time is during normal electricity consumption period and the discharging time is during peak electricity consumption period.

[0089] Table 2: Energy input and output of heat pump PCM system

[0090]

[0091]

[0092] In addition to Examples 1 to 3, other simpler PCM systems may be used. For example, the heat pump may be configured to always operate at the overhead pressure required for the PCM, and therefore only require a single stage compressor. Many processes include unused waste heat, so that one or more heat pumps can upgrade waste heat from other streams in the main process or other process streams within the plant. Additionally or alternatively, an electric heat pump may be used to supply all of the reboiler duty, so that all of the thermal energy extracted from the overhead steam may be directed to the heat pump to charge the PCM. Likewise, the electric heater may be configured to supply a portion of the reboiler duty depending on power availability and peak power prices.

[0093] Embodiment 4:

[0094] Example 4 illustrates the use of high temperature process heat to charge the PCM. Fig.14A and 14B A process schematic diagram of another embodiment of the PCM system of the present invention is shown, in which high temperature process heat is used to charge the PCM, wherein Fig.14A A system for charging the PCM 302 is shown, and Fig. 14B A system for releasing energy for the PCM is shown. In this embodiment, the chemical process feed is preheated at heat exchanger 304 and fed to a chemical reactor 308. The reactor effluent is cooled while heat is recovered from the reactor effluent at 312. The recovered heat is used partly elsewhere in the process and partly in the process flow that includes the PCM 302.

[0095] During the PCM charging portion of the cycle ( Fig.14A ), an electric heater is used to preheat the feed to the reactor. In this embodiment, the electric heater heats the intermediate heat transfer fluid, which is then circulated through the heat exchanger at 304 to preheat the process feed. During charging, the PCM portion of the heat recovered at 312 is used to charge the PCM 302.

[0096] In the PCM energy release phase of the cycle ( Fig. 14B ), the electric heater can be turned off or redirected, and the heat from PCM 302 and the PCM portion of the heat recovered at 312 are used to heat the heat transfer fluid that preheats the process feed at 304. The process thus maintains continuous heating of the process feed throughout the cycle, including hours when the electric heater is turned off (e.g., when electricity is not available or is only available at high cost). The combination of 300MWh PCM thermal storage and 25MW process heat recovery covers the 50MW of process heat required during this period.

[0097] The above description and examples provide a complete description of the structure and use of exemplary embodiments. Although certain embodiments have been described above with some degree of particularity or with reference to one or more separate embodiments, those skilled in the art may make many changes to the disclosed embodiments without departing from the scope of the invention. Therefore, the various illustrative embodiments of the present invention are not intended to be limited to the specific forms disclosed. On the contrary, they include all modifications and substitutions that fall within the scope of the claims, and embodiments other than the illustrated embodiments may include some or all of the features of the illustrated embodiments. For example, components may be combined into a single structure, and / or connections may be replaced. In addition, where appropriate, aspects of any of the above embodiments may be combined with aspects of any other described embodiments to form other embodiments having comparable or different properties and solving the same or different problems. Similarly, it should be understood that the above benefits and advantages may relate to one embodiment or to several embodiments.

[0098] The claims are not intended to include, nor should they be interpreted as including, method-plus-function or step-plus-function limitations, unless such limitations are explicitly recited in a given claim using the phrases "a method for" or "a step for," respectively.

Claims

1. A system for heating and releasing thermal energy for storage in a chemical plant process, characterized in that The system comprises: Phase change materials (PCMs) including volume; a heat exchange system configured to transfer thermal energy from the PCM to one or more of a chemical reactant, a chemical intermediate, or a chemical product; wherein the PCM is configured to transition from a first state to a high enthalpy second state at a transition temperature equal to or greater than a process temperature of an associated chemical reactant, chemical intermediate, or chemical product; and Wherein the PCM requires at least 2 MWh to transition from the first state to the second state.

2. The system according to claim 1, characterized in that Wherein thermal energy is transferred to the PCM from one or more of the chemical reactants, chemical intermediates, or chemical product streams.

3. The system according to any one of claims 1 to 2, characterized in that wherein the heat exchange system comprises a heating circuit configured to circulate a heat transfer fluid in thermal communication with the PCM such that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to one or more of the chemical reactants, the chemical intermediates, or the chemical products.

4. The system according to any one of claims 1 to 3, characterized in that Wherein the heat source comprises an electric heater.

5. The system according to claim 4, characterized in that The system is configured to alternate between a charging cycle and an energy release cycle, during which the electric heater provides thermal energy to one or more of the chemical reactants, the chemical intermediates or the chemical products, and during the energy release cycle, the heat exchange system transfers thermal energy from the PCM to one or more of the chemical reactants, the chemical intermediates or the chemical products, wherein during the charging cycle, the electric heater provides thermal energy to the PCM and one or more of the chemical reactants, chemical intermediates and / or chemical products.

6. The system according to any one of claims 1 to 3, characterized in that Wherein the heat source comprises a heat pump, wherein the heat pump is configured to receive waste energy from the process or a different process in the chemical plant.

7. The system according to any one of claims 1 to 6, characterized in that Wherein the material production rate of the chemical plant is maintained at a constant level regardless of whether the PCM is in the first state or the second state.

8. The system according to any one of claims 6 to 7, characterized in that The system further comprises: an electric heater configured to provide thermal energy to the chemical process; The system is configured to alternate between a charging cycle and an energy release cycle, during which the electric heater provides thermal energy to one or more of the chemical reactants, the chemical intermediates, or the chemical products, and during which the heat exchange system transfers thermal energy from the PCM to one or more of the chemical reactants, the chemical intermediates, or the chemical products.

9. The system according to any one of claims 4 or 6, characterized in that Wherein the heat source configured to transfer thermal energy to the PCM is a first heat source, and the system further includes a second heat source configured to transfer thermal energy to the chemical process.

10. A method for storing and releasing thermal energy for heating in a chemical plant process, characterized in that The method comprises: During an energy release cycle, circulating a heat transfer fluid in thermal communication with a phase change material (PCM) such that the heat transfer fluid absorbs thermal energy from the PCM and transfers at least a portion of the absorbed thermal energy to one or more of a chemical reactant, a chemical intermediate, or a chemical product; wherein the PCM is configured to transition from a first state to a high enthalpy second state at a transition temperature that is above a process temperature associated with one or more of the chemical reactants, the chemical intermediates, or the chemical products; and The PCM is configured to transfer at least 2 MWh of energy to the heat transfer fluid during a single energy release cycle.

11. The method according to claim 10, characterized in that The method further comprises: During a charging cycle, thermal energy is transferred from a heat source to the heat transfer fluid.

12. The method according to claim 11, characterized in that The 24-hour period includes one or more energy release cycles lasting a total of 2-22 hours, and one or more energy recharge cycles lasting a total of 2-22 hours.

13. The method according to claim 12, characterized in that The lengths of the charging cycle and the discharging cycle are adjusted or selected in response to a request from a grid operator to reduce electrical energy consumption.

14. The method according to claim 13, characterized in that The lengths of the charging cycle and the discharging cycle are selected to reduce the total electricity cost of continuously operating the chemical process at a steady material production rate over the 24 hour period, taking into account changes in electricity prices over the 24 hour period.

15. The method according to claim 13, characterized in that Wherein initiation and length of operation of the energy discharge cycle is determined in response to a temporary interruption of at least one source of electrical power for the process.

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