Methods of heat recovery using a high temperature heat pump with azeotropic mixtures

Abstract

According to the present disclosure, there is provided a method for waste heat recovery from a plant for polymerising olefins. The method comprising transferring heat from a stage of the polymerisation process to a working fluid of a heat pump, wherein the working fluid of the heat pump comprises an azeotrope comprising a first component and a second component, wherein the first component is an organic component, and wherein said azeotrope has a boiling point at 1 bara that is lower than the boiling point of said organic component in its pure form, at 1 bara, and a heat of evaporation that is greater than the heat of evaporation of said organic component in its pure form.

Description

[0001] METHODS OF HEAT RECOVERY USING A HIGH TEMPERATURE HEAT PUMP WITH AZEOTROPIC MIXTURES

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to a method for waste heat recovery from a plant for polymerising olefins.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] To efficiently perform polymerisation at an industrial scale there is a need to control the temperature of different stages of the process in an efficient and effective way. For example, polymerisation process streams may require cooling at various stages of the process. The polymerisation process itself is typically exothermic and performed on a large scale industrially, meaning there is a need to remove a significant amount of heat from the polymerisation reactors consistently and efficiently in order to maintain optimal operation, e.g. so as to maintain constant reaction temperature so that the polymerisation reaction delivers the expected results and is effective. Often olefin polymerisation plants operate using a multistage polymerisation process, where polymerisation occurs in different reactors, for example slurry reactors and gas phase reactors. Each of these reactors may operate under different reaction conditions (e.g. temperature, pressure, concentrations of monomer) and so may have different heat removal requirements. On the other hand typical the monomer recovery requires heat input to separate the hydrocarbons from the polymer and to purify the unreacted monomer, optional co-monomers and optional diluent from low molecular components e.g. heavies and light impurities and inert components.

[0006] Typical hot and cold utilities produced out-side the battery limits of the polyolefin production plant are applied to facilitate these heat transfer processes inside the battery limits of said polyolefin production plant. The production of said hot and cold utilities requires energy such as electricity and / or fuel, e.g. natural gas. Also waste heat is rejected to a sink, which is either open water or the atmosphere.

[0007] To improve energy efficiency and reduce the consumption of fuels such as natural gas processes are designed with heat integration and high temperature heat pumps.

[0008] Conventional heat pumps use a works fluid (for example CFCs (chlorofluorocarbons), HFCs (hydrofluorocarbons), pure hydrocarbons and water to lift the temperature of the waste heat and reject energy above the pinch temperature useful for the process or the production site.EP4269758A1 describes a method which employs a conventional high temperature heat pump for recovering energy in which heat is transferred to a first heat transfer fluid, the heated first heat transfer fluid is compressed and the compressed heat transfer fluid is used for vaporizing an aqueous condensate to steam, which can be used for heat recovery.

[0009] US20140131613A1 describes a refrigerant for use in a thermodynamic cycle of a system for a low temperature heat pump producing either heat or cold, said refrigerant being a binary azeotrope mixture comprising of a saturated hydrocarbon having carbon chain with 2 or 3 atoms of carbon and an aliphatic alcohol selected from a group including methanol and ethanol.

[0010] The objective of this invention is to lift the waste heat above the pinch temperature in an energy effective way by a novel works fluid, to obtain an energy efficient high temperature heat pump.

[0011] There is a need to provide improved methods for waste heat recovery from a plant for polymerising olefins.

[0012] Various aspects of the invention are described in further detail below.

[0013] BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a graph showing results from pinch analysis of a Borstar PE polymerisation process. This figure shows a composite curve with 6°C shift.

[0015] Figure 2 is a schematic drawing of an integration of a high temperature heat pump with a gas phase polymerisation reactor.

[0016] Figure 3 is a schematic drawing of an arrangement of a high temperature heat pump with a loop reactor for olefin polymerizations in slurry or bulk phase.

[0017] Figure 4 is a T-xy diagram of cyclo-pentane and ethanol.

[0018] Figure 5 is a T-xy diagram of n-pentane and ethanol.

[0019] Figure 6 is a T-xy diagram of 2,2-dimethylbutane and ethanol.SUMMARY OF THE INVENTION

[0020] According to the present disclosure, there is provided a method for waste heat recovery from a plant for polymerising olefins. The method comprises transferring heat from a stage of the polymerisation process to a working fluid of a heat pump, wherein the working fluid of the heat pump comprises an azeotrope comprising a first component and a second component, wherein the first component is an organic component, and wherein said azeotrope has a boiling point at 1 bara that is lower than the boiling point of said organic component in its pure form, at 1 bara, and a heat of evaporation that is greater than the heat of evaporation of said organic component in its pure form.

[0021] The organic component may be a hydrocarbon, preferably, a Cs to C12 hydrocarbon, more preferably a C5 to C9 hydrocarbon.

[0022] The preferred hydrocarbon is one chosen from the group consisting of an alkane, cycloalkane, alkene or cycloalkene, and iso-alkenes, or combinations thereof more preferably is one chosen from the group consisting of cyclopentane, pentane, hexane, isopentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, cyclohexane, n-hexane, n-heptane, 2-methylhexane, 3-methylhexane and octane or combinations thereof.

[0023] Preferably, the second component comprises an alcohol, more preferably ethanol.

[0024] Preferably, the second component azeotrope is an alcohol, more preferably ethanol. Suitably the azeotrope comprises an alcohol and a hydrocarbon. Suitably the azeotrope consists of an alcohol and a hydrocarbon. Suitably the boiling point of the azeotrope is lower relative to the boiling points of any of its constituent liquids. Suitably where the azeotrope comprises an alcohol and a hydrocarbon the boiling point of the azeotrope is lower than the boiling points of each of the alcohol and the hydrocarbon.

[0025] The azeotrope may comprise 3 to 80 weight % alcohol.

[0026] In certain embodiments the boiling point of the azeotrope at 1 bara is 30 to 80 °C and the heat of vaporisation of the azeotrope is 360 to 900 kJ / kg.

[0027] In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 127 °C, and / or wherein the heat of vaporisation of the organic component in its pure form is 295 to 410 kJ / kg. Suitably the boiling point of the organic component in its pure form in the azeotrope at 1 bara is 28 to 127 °C. Suitably the heat of vaporisation of the organiccomponent in its pure form is 295 to 410 kJ / kg. Preferably the boiling point of the organic component in its pure form in the azeotrope at 1 bara is 28 to 127 °C, and the heat of vaporisation of the organic component in its pure form is 295 to 410 kJ / kg.

[0028] Advantageously, the boiling point of the azeotrope may be lower than the boiling point of the pure organic component and lower than the boiling point of the second component in its pure form and / or the heat of vaporisation of the azeotrope may be at least 5% higher than that of the organic component in its pure form.

[0029] Preferably, the azeotrope is a binary mixture. Suitably the azeotrope is a ternary mixture.

[0030] The heat pump may be a high temperature heat pump.

[0031] Preferably, heat is transferred from a polymerisation reactor, more preferably a gas phase polymerisation reactor and / or a loop reactor.

[0032] Advantageously, the heat transferred to the working fluid may be used to evaporate the working fluid thereby providing a working fluid vapour. Heat may be removed from the working fluid vapour by an external water stream to condense the working fluid vapour and generate steam by evaporation of the external water stream. The steam generated may be used in another stage of the process.

[0033] In certain embodiments the heat pump has a coefficient of performance of at least 3.7.

[0034] Preferably, the method is a method for waste heat recovery from a plant for polymerising propylene and / or ethylene.

[0035] Disclosed herein is a multistage polymerisation process comprising polymerisation of olefins in a first reactor to produce a first polymer component and polymerisation of olefins in a second reactor, preferably a gas phase reactor, to produce a second polymer component in the presence of the first polymer component, and wherein heat from the first reactor and / or the second reactor is recovered in accordance with the heat recovery methods of the disclosure. Suitably the olefins in a first reactor may be selected from ethylene, propylene, 1-butene, 1 -hexene, 1 -octene. Suitably the method may be a multistage polymerisation process for ethylene polymerisation comprising polymerisation of ethylene optionally with one or at least one comonomer in a first reactor to produce a first polymer and polymerisation of ethylene and at least one comonomer in a second reactor. Suitably themethod may be a multistage polymerisation process for propylene polymerisation comprising polymerisation of propylene and optionally at least one comonomer in a first reactor to produce a first polymer and polymerisation of propylene and optionally at least one comonomer in a second reactor.

[0036] Existing high temperature heat pump systems (HTHP systems) can be associated with a number of disadvantages. HFOs may not be available in sufficient amounts to be used in olefin polymerisation plants. HFOs may also be relatively commercially expensive when compared with alternative heat pump media. Certain HFOs may also be toxic and may harm the local environment in the case of installation, accidental release e.g. by leaks, and / or ultimate disposal when the plant is upgraded / decommissioned. “Classical heat pump media”, for example, H2O, CO2 and NH3 may be less suitable for the application of waste heat recovery from a plant for polymerising olefins. This is because, inter alia, H2O shows a relatively low evaporation rates at the waste heat source temperatures of interest and so does not efficiently transfer heat, for example because the waste heat sources in a polymerisation plant are in general significantly below 100 °C. In order to use water as the working fluid the evaporation of the work fluid should be done at a vapour pressure below atmospheric pressure, so vacuum is needed, causing large volume flows and technical challenges e.g. arising from leakage of oxygen into the system which can result in pitting and stress assisted corrosion. Use of CO2, NH3 in a polymerisation plant may be relatively unsuitable because in order to operate at the waste heat sink temperatures present in such a plant, high pressures of operation are required meaning that the heat transfer process is less energetically efficient (e.g. due to the need for thick walls), and specialist and structurally complex heat pump equipment is required which can be operated at these high pressures. Further, the use of CO2 and NH3 in this context is associated with significant safety concerns due to their asphyxiation and toxicity risks respectively. Many conventional HTHP systems provide low elevations in temperature at the output, and so to achieve a useful steam utility often multistage compression is required, which is problematic as the equipment is complex and energy intensive.

[0037] Surprisingly the inventors have found that the working fluids of methods of the disclosure may be associated with the advantage of increased latent heats of evaporation in comparison to conventional working fluids. This may be beneficial for example because less working fluid is required per unit heat and so the methods can be performed with smaller compressors requiring less energy to run. Furthermore, without being bound by any theory, the method according to the present invention is found to result in a decrease in energyconsumption of the polymerisation plant when compared with methods using conventional HTHP.

[0038] The inventors have surprisingly found that the methods of the disclosure may be especially suited for cooling waste heat sources in olefin polymerisation plants. This is may be because the boiling points at atmospheric pressure of the working fluids of the disclosure may be sufficiently below the temperature ranges of the waste heat sources present in olefin polymerisation plants to enable efficient heat transfer. Advantageously methods of the invention may be more readily used in olefin polymerisation plants. Advantageously, methods of the disclosure may be less harmful to the environment. This may be because a more efficient heat transfer can be achieved (so the overall energy efficiency is higher) and because the use of harmful / toxic working fluids (e.g. HFOs) can be avoided. Advantageously the methods of the invention may reduce the initial set up cost of the olefin polymerisation plant. Advantageously the methods of the invention may reduce running cost of the olefin polymerisation plant. These advantages may be because the working fluids of the disclosure are inexpensive (e.g. less expensive per kg than HFOs), the methods are more energy efficient (e.g. requiring less energy than methods using “classical heat pump media” like H2O, CO2 and NH3) and less complex heat pump apparatus is required (for example less complex than the high pressure apparatus needed for CO2 and NH3). Advantageously fewer stages of compression required in order to achieve a steam utility and so the disadvantages of multistage compression are avoided. Advantageously methods of the invention may ensure that parts of the plant requiring cooling stay in a safe operation window, producing the desired product properties with high operability, (without fouling of reactors or producing lumps).

[0039] DETAILED DESCRIPTION OF THE DISCLOSURE

[0040] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

[0041] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0042] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to beunderstood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

[0043] Used herein liquid mixtures having an extremum (maximum or minimum) vapor pressure at constant temperature, as a function of composition, are called azeotropic mixtures, or simply azeotropes. By way of example, a mixture of liquid A and liquid B having a maximum vapour pressure at 25 °C when the mixture consists of 30 wt% of A and 70 wt% of B, and which has lower vapour pressures at 25 °C for any other weight % of A and B, would be considered an azeotrope.

[0044] Citation of

[0045] Wypych, George. (2024). Handbook of Solvents, Volume 1 - Properties (4th Edition). ChemTec Publishing. Retrieved from

[0046] https: / / app.knovel.com / hotlink / toc / id:kpHSEVP002 / handbook-solvents-volume / handbook-solvents-volume :

[0047] “ A mixture of 95.6% ethanol and 4.4% water has a constant boiling point of 78.2°C, as compared to the with the boiling points of ethanol and water 78.5°C and 100°C, respectively.”

[0048] “Hence, an ethanol / water mixture is an example of azeotropic mixture that has a boiling point lower than its constituents, and is called a minimum boiling azeotrope (or positive azeotrope). This is opposite to the mixture of HCI (35.6%) / water, which boils at 110°C when HCI boils at -85°C and water boils at 100°C.HCI / water is called maximum boiling azeotrope (or negative azeotrope).”

[0049] Mixtures that do not show a maximum or minimum are called zeotropic. Azeotropes in which the vapour pressure is a maximum are often called negative azeotropes, while vapour pressure-minimum azeotropes are called positive azeotropes. Preferably the azeotrope is a positive azeotrope. The coordinates of an azeotropic point are the azeotropic temperature Taz, pressure Paz, and liquid-phase composition, usually expressed as mole fractions. At the azeotropic point at equilibrium, the vapor-phase composition is substantially the same as the liquid-phase composition.

[0050] The present disclosure provides a method for waste heat recovery from a plant for polymerising olefins. The method comprises transferring heat from a stage of the polymerisation process to a working fluid of a heat pump, wherein the working fluid of the heat pump comprises an azeotrope comprising a first component and a second component, wherein the first component is an organic component, and wherein said azeotrope has aboiling point at 1 bara that is lower than the boiling point of said organic component in its pure form at 1 bara and a heat of evaporation that is greater than the heat of evaporation of said organic component in its pure form. Suitably the organic component is a non-alcoholic. Suitably the boiling point at 1 bara of the azeotrope is at least 0.5 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 1.0 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 1.5 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 2 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 3 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 4 °C lower than the boiling point at 1 bara of the pure organic component. Suitably the boiling point at 1 bara of the azeotrope is at least 5 °C lower than the boiling point at 1 bara of the pure organic component. Used herein the term “organic component” refers to an organic molecule which can be a liquid under the conditions of the working fluid when the heat pump is in operation. “Organic component” includes hydrocarbons and optionally substituted hydrocarbons, for example alcohols, ketones, amides, nitriles and amines. Used herein the term “in its pure form” refers to a substance in isolation, in the absence of other substances, for example cyclopentane in its pure form refers to cyclopentane alone, and not e.g. cyclopentane present within an azeotrope. The second component may be a fluid (preferably liquid) in its pure form under the conditions of the working fluid when the heat pump is in operation. The second component is capable of forming an azeotrope with the first component under the conditions of the working fluid when the heat pump is in operation. Suitably the second component may be organic.

[0051] The organic component may be a hydrocarbon, preferably, a Cs to C12 hydrocarbon, more preferably a C5 to C9 hydrocarbon. For example the hydrocarbon may be a C5 to Cs hydrocarbon. Suitably the hydrocarbon is an alkane. Suitably the hydrocarbon is an alkene. Suitably the hydrocarbon is an alkyne. Suitably the hydrocarbon is an arene. Suitably the hydrocarbon is an optionally substituted aromatic, for example and optionally substituted arene. Suitably the hydrocarbon is linear. Suitably the hydrocarbon is branched. Suitably the hydrocarbon is a cycloalkane. Suitably the hydrocarbon is a mixture.

[0052] Where the organic component is a hydrocarbon, the hydrocarbon may be selected from an alkane, cycloalkane, alkene or cycloalkene, or iso-alkenes, preferably cyclopentane, pentane, hexane, iso-pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, benzene, cyclohexane, n-hexane, toluene, n-heptane, 2-methylhexane, 3-methylhexane and octane. Preferably hydrocarbon is selected from cyclopentane, pentane, hexane, iso-pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, cyclohexane, n-hexane, toluene, n-heptane, 2-methylhexane and 3-methylhexane. Suitably the hydrocarbon is an alkane. Suitably the hydrocarbon is an isoalkane. Suitably the hydrocarbon is a cycloalkane. Suitably the hydrocarbon is an alkene. Suitably the hydrocarbon is an cycloalkene. Suitably the hydrocarbon is an optionally substituted cycloalkene. Suitably the hydrocarbon is an iso-alkene. Preferably the hydrocarbon is cyclopentane. Preferably the hydrocarbon is pentane. Preferably the hydrocarbon is hexane. Preferably the hydrocarbon is n-hexane. Preferably the hydrocarbon is iso-pentane. Preferably the hydrocarbon is 2,2-dimethylbutane. Preferably the hydrocarbon is 2,3-dimethylbutane. Preferably the hydrocarbon is 2-methylpentane.

[0053] Preferably the hydrocarbon is 3-methylpentane. Preferably the hydrocarbon is cyclohexane. Preferably the hydrocarbon is toluene. Preferably the hydrocarbon is n-heptane. Preferably the hydrocarbon is 2-methylhexane. Preferably the hydrocarbon is 3-methylhexane.

[0054] Preferably the hydrocarbon is octane. Preferably the hydrocarbon is n-octane.

[0055] In certain embodiments the second component comprises an alcohol, preferably ethanol. In certain embodiments the second component is an alcohol, preferably ethanol. Suitably the azeotrope comprises an alcohol and an organic component. Suitably the azeotrope comprises an alcohol and an organic component. Suitably the azeotrope comprises an alcohol and an organic component wherein the organic component is non-alcoholic. Used herein alcohol refers to an organic compound having at least one hydroxyl group. Suitably the alcohol may be a C1-C10 alcohol. More suitably the alcohol may be a Ci-Ce alcohol. Even more suitably a Ci-Ce alcohol. Suitably the alcohol may be selected from the group of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol and 3-pentanol. For example, the alcohol may be selected from the group of methanol, ethanol, 1-propanol, 2-propanol. Suitably the azeotrope may comprises one alcohol. Suitably the azeotrope may comprises two alcohols. Suitably the azeotrope may comprises three alcohols. Suitably the azeotrope may comprises more than one alcohol.

[0056] In some embodiments the azeotrope comprises 3 to 80 weight % alcohol. Suitably the azeotrope comprises up to 65 weight % alcohol, up to 68 weight % alcohol, up to 70 weight % alcohol, up to 72 weight % alcohol, up to 75 weight % alcohol or up to 78 weight % alcohol. Suitably the azeotrope comprises 3 to 65 weight % alcohol, 3 to 68 weight % alcohol, 3 to 70 weight % alcohol, 3 to 72 weight % alcohol, 3 to 75 weight % alcohol or 3 to 78 weight % alcohol. Suitably the azeotrope comprises greater than 4 weight % alcohol orgreater than 5 weight % alcohol. For example suitably the azeotrope comprises 4 to 80 weight % alcohol or 5 to 80 weight % alcohol. Suitably the azeotrope comprises up to 35 weight % alcohol, up to 40 weight % alcohol, up to 45 weight % alcohol, up to 50 weight % alcohol, up to 55 weight % alcohol or up to 60 weight % alcohol. Suitably the azeotrope comprises 3 to 35 weight % alcohol, 3 to 40 weight % alcohol, 3 to 45 weight % alcohol, 3 to 50 weight % alcohol, 3 to 55 weight % alcohol or 3 to 60 weight % alcohol.

[0057] In certain embodiments the boiling point of the azeotrope at 1 bara is 30 to 80 °C and the heat of vaporisation of the azeotrope if 360 to 900 kJ / kg. In certain embodiments the boiling point of the azeotrope at 1 bara is 30 to 80 °C. In certain embodiments the heat of vaporisation of the azeotrope if 360 to 900 kJ / kg, preferably 390 to 800 kJ / kg.

[0058] In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 127 °C, and / or the heat of vaporisation of the organic component in its pure form is 295 to 410 kJ / kg. In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 127 °C. In certain embodiments the heat of vaporisation of the organic component in its pure form is 295 to 410 kJ / kg. In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 120 °C. In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 115 °C. In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 110 °C. In certain embodiments the boiling point of the organic component in its pure form at 1 bara is 28 to 105 °C.

[0059] In certain embodiments the boiling point of the azeotrope is lower than the boiling point of the second component in its pure form and / or the heat of vaporisation of the azeotrope is at least 5% higher than that of the organic component in its pure form. Suitably the boiling point of the azeotrope is at least 0.5 °C lower than the lower boiling point of the pure organic component and the pure second component. Suitably the boiling point of the azeotrope is at least 1.0 °C lower, at least 1.5 °C lower, at least 2 °C lower, at least 3 °C lower, at least 4 °C lower or at least 5 °C lower than the lower boiling point of the pure organic component and the pure second component. Suitably the heat of vaporisation of the azeotrope is at least 5% higher than that of the organic component in its pure form. Suitably the heat of vaporisation of the azeotrope is at least 6% higher, at least 7% higher, at least 8% higher, at least 10% higher, at least 12% higher, at least 15% higher, at least 18% higher or at least 20% higher than that of the organic component in its pure form. Suitably the heat of vaporisation of the azeotrope is at least 5% higher than that of the second component in its pure form. Suitably the heat of vaporisation of the azeotrope is at least 6% higher, at least 7% higher, at least8% higher, at least 10% higher, at least 12% higher, at least 15% higher, at least 18% higher or at least 20% higher than that of the second component in its pure form.

[0060] In certain embodiments the azeotrope is a binary mixture. Used herein the term binary mixture may refer to a mixture consisting of two different chemical components. An example of a binary mixture would be a mixture consisting of cyclopentane and ethanol. For the purposes of assessing what constitutes different chemical components in a binary mixture, it may be appropriate to consider structurally distinct molecules which have similar physical properties, for example isotopologues like the all protium form of propane and the partially deuterated forms of propane. Compounds having different chemical structures but the same or very similar physical properties (e.g. enantiomers and isotopologues) may be considered as a single chemical component for the purposes of assessment of whether an azeotrope is a binary mixture.

[0061] In certain embodiments the heat pump is a high temperature heat pump. The high temperature heat pump may provide an outflow of heat above the pinch temperature. The high temperature heat pump may provide an outflow of heat in the region using heat at a temperature in the range of 80 °C to 275 °C, 90 °C to 190 °C, 100°C to 180 °C, or 110 °C to 175 °C.

[0062] In certain embodiments heat is transferred from a polymerisation reactor. Preferably heat is transferred from a gas phase polymerisation reactor and / or a loop reactor. More preferably heat is transferred from a gas phase polymerisation reactor. Even more preferably heat is transferred from a gas phase polymerisation reactor and a loop reactor. In certain embodiments heat is transferred from more than one polymerisation reactors, preferably at least one gas phase polymerisation reactor and / or at least one loop reactor. More preferably heat is transferred from at least one gas phase polymerisation reactor. Even more preferably heat is transferred from at least one gas phase polymerisation reactor and at least one loop reactor.

[0063] In certain embodiments the heat transferred to the working fluid is used to evaporate the working fluid thereby providing a working fluid vapour, and wherein heat is removed from the working fluid vapour by an external water stream to condense the working fluid vapour and generate steam by evaporation of the external water stream for use in the process. The steam may be used to as an energy source for heating within the polymerisation plant.Suitably the steam is low pressure steam. Used herein the term low pressure steam refers to steam of pressure up to 10 bara, for example 2.5 bara to 6 bara, typically 5.0 to 5.5 bara.

[0064] In certain embodiments the heat pump has a coefficient of performance of at least 3.7.

[0065] Suitably the heat pump has a coefficient of performance of at least 4.0, for example at least 4.3.

[0066] In certain embodiments the method is a method for waste heat recovery from a plant for polymerising propylene and / or ethylene. In certain embodiments the method is a method for waste heat recovery from a plant for polymerising propylene. In certain embodiments the method is a method for waste heat recovery from a plant for polymerising ethylene. In certain embodiments the method is a method for waste heat recovery from a plant for polymerising propylene and ethylene. In certain embodiments the method is a method for waste heat recovery from a plant for polymerising propylene in the presence of one or more comonomer selected from ethylene and / or a C4-C10 alpha olefins. In certain embodiments the method is a method for waste heat recovery from a plant for polymerising ethylene in the presence of one or more comonomer selected from a C3-C10 alpha olefins.

[0067] Disclosed herein is a method that is a multistage polymerisation process comprising polymerisation of olefins in a first reactor to produce a first polymer component and polymerisation of olefins in a second reactor, preferably a gas phase reactor, to produce a second polymer component in the presence of the first polymer component, and wherein heat from the first reactor and / or the second reactor is recovered in accordance with the method for waste heat recovery described herein.. Preferably heat is transferred from the first reactor. More preferably heat is transferred from the second reactor. Heat may be transferred from the first reactor and the second reactor.

[0068] Suitably the azeotrope is a mixture of trichloromethane and water. Suitably the azeotrope is a mixture of formic acid and water. Suitably the azeotrope is a mixture of nitromethane and water. Suitably the azeotrope is a mixture of carbon disulfide and water. Suitably the azeotrope is a mixture of acetonitrile and water. Suitably the azeotrope is a mixture of nitroethane and water. Suitably the azeotrope is a mixture of ethyl acetate and water.

[0069] Suitably the azeotrope is a mixture of 1 -butanol and water. Suitably the azeotrope is a mixture of 2-butanol and water. Suitably the azeotrope is a mixture of ethanol and water. Suitably the azeotrope is a mixture of pyridine and water. Suitably the azeotrope is a mixture of piperidine and water. Suitably the azeotrope is a mixture of pentane and water. Suitably the azeotrope is a mixture of chlorobenzene and water. Suitably the azeotrope is a mixtureof benzene and water. Suitably the azeotrope is a mixture of phenol and water. Suitably the azeotrope is a mixture of cyclohexene and water. Suitably the azeotrope is a mixture of cyclohexane and water. Suitably the azeotrope is a mixture of hexane and water. Suitably the azeotrope is a mixture of toluene and water. Suitably the azeotrope is a mixture of heptane and water. Suitably the azeotrope is a mixture of 1,3-dimethylbenzene and water. Suitably the azeotrope is a mixture of ethylbenzene and water. Suitably the azeotrope is a mixture of octane and water. Suitably the azeotrope is a mixture of nonane and water.

[0070] Suitably the azeotrope is a mixture of dibutyl ether and water. Suitably the azeotrope is a mixture of tributylamine and water. Suitably the azeotrope is a mixture of formic acid and carbon disulfide. Suitably the azeotrope is a mixture of nitromethane and carbon disulfide. Suitably the azeotrope is a mixture of methanol and acetone. Suitably the azeotrope is a mixture of methanol and methyl acetate. Suitably the azeotrope is a mixture of methanol and cyclopentane. Suitably the azeotrope is a mixture of methanol and pentane. Suitably the azeotrope is a mixture of methanol and tert-butyl methyl ether. Suitably the azeotrope is a mixture of methanol and benzene. Suitably the azeotrope is a mixture of methanol and cyclohexane. Suitably the azeotrope is a mixture of methanol and toluene. Suitably the azeotrope is a mixture of methanol and heptane. Suitably the azeotrope is a mixture of methanol and octane. Suitably the azeotrope is a mixture of methanol and nonane. Suitably the azeotrope is a mixture of carbon disulfide and ethanol. Suitably the azeotrope is a mixture of carbon disulfide and acetone. Suitably the azeotrope is a mixture of carbon disulfide and 1 -propanol. Suitably the azeotrope is a mixture of carbon disulfide and ethyl acetate. Suitably the azeotrope is a mixture of acetonitrile and ethanol. Suitably the azeotrope is a mixture of acetonitrile and toluene. Suitably the azeotrope is a mixture of acetic acid and 1,4-dioxane. Suitably the azeotrope is a mixture of acetic acid and pyridine. Suitably the azeotrope is a mixture of acetic acid and benzene. Suitably the azeotrope is a mixture of acetic acid and cyclohexane. Suitably the azeotrope is a mixture of acetic acid and hexane. Suitably the azeotrope is a mixture of acetic acid and triethylamine. Suitably the azeotrope is a mixture of acetic acid and toluene. Suitably the azeotrope is a mixture of acetic acid and heptane. Suitably the azeotrope is a mixture of acetic acid and ethylbenzene. Suitably the azeotrope is a mixture of acetic acid and octane. Suitably the azeotrope is a mixture of acetic acid and nonane. Suitably the azeotrope is a mixture of iodoethane and hexane. Suitably the azeotrope is a mixture of acetic acid and heptane. Suitably the azeotrope is a mixture of ethanol and pentane. Suitably the azeotrope is a mixture of ethanol and benzene. Suitably the azeotrope is a mixture of ethanol and cyclohexane. Suitably the azeotrope is a mixture of ethanol and hexane. Suitably the azeotrope is a mixture of ethanol and octane. Suitably the azeotrope is a mixture of ethanol and toluene. Suitably the azeotrope is a mixture of ethylene glycol and toluene. Suitably the azeotrope is a mixture ofethylene glycol and heptane. Suitably the azeotrope is a mixture of ethylene glycol and dibutyl ether. Suitably the azeotrope is a mixture of ethylene glycol and decane. Suitably the azeotrope is a mixture of dimethyl sulfide and pentane. Suitably the azeotrope is a mixture of 1,2-ethylanediamine and toluene. Suitably the azeotrope is a mixture of propane nitrile and hexane. Suitably the azeotrope is a mixture of acetone and methyl acetate. Suitably the azeotrope is a mixture of acetone and cyclopentane. Suitably the azeotrope is a mixture of acetone and cyclohexane. Suitably the azeotrope is a mixture of ethyl formate and pentane. Suitably the azeotrope is a mixture of methyl acetate and cyclohexane. Suitably the azeotrope is a mixture of methyl acetate and hexane. Suitably the azeotrope is a mixture of propanoic acid and pyridine. Suitably the azeotrope is a mixture of propanoic acid and heptane. Suitably the azeotrope is a mixture of propanoic acid and propylbenzene. Suitably the azeotrope is a mixture of 1 -nitropropane and 1-propanol. Suitably the azeotrope is a mixture of 1 -nitropropane and heptane. Suitably the azeotrope is a mixture of 1-propanol and 1,4-dioxane. Suitably the azeotrope is a mixture of 1-propanol and benzene. Suitably the azeotrope is a mixture of 1-propanol and cyclohexane. Suitably the azeotrope is a mixture of 1-propanol and heptane. Suitably the azeotrope is a mixture of 2-propanol and butylamine. Suitably the azeotrope is a mixture of 2-propanol and butylamine. Suitably the azeotrope is a mixture of 2-propanol and pentane. Suitably the azeotrope is a mixture of 2-propanol and cyclohexane. Suitably the azeotrope is a mixture of 2-propanol and toluene. Suitably the azeotrope is a mixture of ethyl methyl sulfide and methylcyclopentane. Suitably the azeotrope is a mixture of ethyl methyl sulfide and 2,2-dimethylpentane. Suitably the azeotrope is a mixture of 1 -propanethiol and cyclohexane. Suitably the azeotrope is a mixture of 1 -propanethiol and hexane. Suitably the azeotrope is a mixture of 1 -propanethiol and diisopropyl ether. Suitably the azeotrope is a mixture of thiophene and cyclohexane. Suitably the azeotrope is a mixture of thiophene and hexane. Suitably the azeotrope is a mixture of butanal and hexane. Suitably the azeotrope is a mixture of 2-butanone and 1-chlorobutane. Suitably the azeotrope is a mixture of 2-butanone and butylamine. Suitably the azeotrope is a mixture of 2-butanone and benzene. Suitably the azeotrope is a mixture of 2-butanone and cyclohexane. Suitably the azeotrope is a mixture of 2-butanone and heptane. Suitably the azeotrope is a mixture of butanoic acid and pyridine. Suitably the azeotrope is a mixture of butanoic acid and chlorobenzene. Suitably the azeotrope is a mixture of butanoic acid and 1,2-dimethylbenzene. Suitably the azeotrope is a mixture of 1,4-dioxane and 1-bromobutane. Suitably the azeotrope is a mixture of ethyl acetate and hexane. Suitably the azeotrope is a mixture of methyl propanoate and 1 -chlorobutane. Suitably the azeotrope is a mixture of propyl formate and 1 -chlorobutane. Suitably the azeotrope is a mixture of propyl formate and benzene. Suitably the azeotrope is a mixture of propyl formate andcyclohexane. Suitably the azeotrope is a mixture of 1 -butanol and pyridine. Suitably the azeotrope is a mixture of 1 -butanol and chlorobenzene. Suitably the azeotrope is a mixture of 1 -butanol and cyclohexene. Suitably the azeotrope is a mixture of 1 -butanol and toluene. Suitably the azeotrope is a mixture of 1 -butanol and heptane. Suitably the azeotrope is a mixture of 1 -butanol and 1,2-dimethylbenzene. Suitably the azeotrope is a mixture of 1-butanol and dibutyl ether. Suitably the azeotrope is a mixture of 2-butanol and benzene. Suitably the azeotrope is a mixture of 2-butanol and heptane. Suitably the azeotrope is a mixture of diethyl ether and pentane. Suitably the azeotrope is a mixture of tert-butyl alcohol and benzene. Suitably the azeotrope is a mixture of tert-butyl alcohol and heptane. Suitably the azeotrope is a mixture of methyl propyl ether and pentane. Suitably the azeotrope is a mixture of 2-ethoxyethanol and heptane. Suitably the azeotrope is a mixture of 2-ethoxyethanol and propylbenzene. Suitably the azeotrope is a mixture of 2-furaldehyde and heptane. Suitably the azeotrope is a mixture of 2-furaldehyde and propylbenzene. Suitably the azeotrope is a mixture of pyridine and toluene. Suitably the azeotrope is a mixture of benzene and cyclohexene. Suitably the azeotrope is a mixture of benzene and cyclohexane. Suitably the azeotrope is a mixture of phenol and 2-methylpyridine. Suitably the azeotrope is a mixture of phenol and 2,4-dimethylpyridine. Suitably the azeotrope is a mixture of phenol and 1 ,3,5-trimethylpyridine. Suitably the azeotrope is a mixture of phenol and decane.

[0071] Suitably the azeotrope is a mixture of aniline and 1 ,3,5-trimethylpyridine. Suitably the azeotrope is a mixture of aniline and dipentyl ether. Suitably the azeotrope is a mixture of aniline and dodecane. Suitably the azeotrope is a mixture of 2-methylpyridine and octane. Suitably the azeotrope is a mixture of cyclohexanol and 1,2-dimethylbenzene. Preferably the azeotrope is a mixture comprising ethanol.

[0072] Optionally, the azeotrope is a mixture comprising ethanol and one of pentane, cyclopentane and 2,2-dimethylbutane.

[0073] Optionally, the azeotrope is a mixture selected from a mixture of pentane and ethanol.

[0074] Optionally the azeotrope is a mixture of cyclopentane and ethanol. Optionally the azeotrope is a mixture of 2,2-dimethylbutane and ethanol.

[0075] Preferably the azeotrope is a mixture of cyclopentane. More preferably the azeotrope is a mixture of ethanol and water. More preferably the azeotrope is a mixture of ethanol and cyclopentane.Used herein the term “bara” refers to absolute pressures measured in bar, so for example, a pressure quoted as 2 bara means an absolute pressure of 2 bars. This is distinct from the term “barg” which refers to gauge pressures measured in bar.

[0076] Used herein the terms “working fluid” and “heat pump media” are synonymous. Used herein the term “working fluid” refers to the substance which undergoes a phase change in a refrigerator system or heat pump system (preferably heat pump), and this phase change transfers heat in the refrigerator system or heat pump system (preferably heat pump). For example, a working fluid may evaporate from a liquid to a vapour in the region of the heat pump in contact with the heat source, subsequently be compressed by a compressor, condense from a vapour to a liquid giving rise to an outflow of heat in the region using heat, and then the liquid pass back into the region of the heat pump in contact with the heat source by passing over an expansion valve. Commonly refrigerants are used as working fluids.

[0077] Used herein the term “non-alcoholic” refers to a substance which is not an alcohol, i.e. a chemical compound not having a hydroxyl moiety, or does not contain an alcohol.

[0078] In general, ethylene polymerization processes are high exothermic processes, for example it has been calculated that for a Borstar® PE process, i.e. a process proprietary to Borealis for manufacturing polyethylene, running a commercial scale plant the release of reaction enthalpy is about 0.91 MWh per ton of produced polymer, a value which corresponds to approximately 67 % of total energy consumption of the plant. The applied operation temperatures during polymerization are relative mild (for example 80-110 °C), so that waste heat recovery with respect to heat integration measures turn out to be extremely difficulty to implement. Waste heat sources within Borstar® processes are characterised by huge heat capacities but at low temperature level with limited theoretical heat integration potential. This difficulty in useful recovery of the waste heat can be seen from the small overlap of the hot and cold composite curves in the pinch analysis shown in figure 1. There is a large quantity of heat produced by these olefin polymerization processes (e.g. polyethylene polymerization processes) which is difficult to capture for useful work as it is produced at temperatures elevated by a relatively small amount compared to the ambient temperature. Prior to this disclosure, high economically costly energy carriers, such as electricity (340 kWh / ton PE) or steam ( about 126 kWh / ton PE), are necessary to operate the plant (for example to power the motor drives, extruders and process steps requiring heating) and they were primarily provided externally. As such a large amount of waste heat is not used productively and there is a need to improve the overall energy efficiency of the process. Further, as the waste heatneeds to be removed from the polymerization process, the overall cooling water demand for the operation of a polymerisation plant is remarkably high. The present disclosure overcomes these problems.

[0079] The inventors have found that for a Borstar® PE plant, there are a number of different possible waste heat sources, which are summarised in the table below. The combination of relatively high energy output and high temperatures mean that the 2ndloop reactor and the gas phase reactor are the most promising sources of waste heat.

[0080] Waste heat source Where the waste Energy in waste Temperature of heat could be heat (MWh / ton) waste heat source captured (°C)

[0081] 1stLoop reactor Jacket water Around 0.23 50-551

[0082] 2ndLoop reactor Jacket water Around 0.23 61-652

[0083] Gas phase reactor Circulation gas Around 0.46 82-903Extrusion Pellet water Around 0.23 50-854

[0084] Other steps Individual hot Around 0.17-0.23 Varies a lot5including column streams or cooling

[0085] condensers and water

[0086] conveying gas

[0087] coolers

[0088]

[0089] 1- Low value heat as low temperature

[0090] 2- Potential water heat source for some heat pump applications

[0091] 317 - 30 % of the waste heat available above 70 °C depending on the product produced so desirable waste heat source

[0092] 4- temperature varies a lot with different products and plants, so low value heat for some cases and desirable in other cases

[0093] 5- difficult to utilise economically as multiple small waste heat sources

[0094] Used herein COP and COPHP refer to the coefficient of performance of the heat pump. The COP can be calculated using the following formula:

[0095] Q Q p > QsiNK > 1 _|_ QSOURCE

[0096]

[0097] Where Qsource refers to the energy transferred from the waste heat source, P refers to the electrical energy consumption of the heat pump compressor.One of the main ways of optimising the energy efficiency of a heat pump (HP) is to concentrate the waste heat in the working fluid whilst lowering the mass stream to the uplifting device (e.g., compressor). With a lower mass flow rate a higher COP can be achieved. Qsource correlates with the latent heat of evaporation (AHevap) of the HP-media, thus COP is dominated by the HTHP-media in all HTHP processes. The inventors have found that broadening the 2-phase area by optimal selection of HP-media can result in an increase in COP. Azeotropes of the disclosure can therefore be used to increase the COP.

[0098] Typically the latent heats of conventional HP-media are in the magnitude of 200-400 kJ / kg. “Classical” HP-media, such as water (2,500 kJ / kg, Pcrit= 221 bar, Tcrit = 374 °C) or ammonia (1,330 kJ / kg, Pcrit = 113 bar, Tcrit = 132 °C) show indeed significantly higher heat of evaporation values AHevap, but for NH3 and CO2 operation pressures at the envisaged heat sink in a polyolefin polymerisation process such as Borstar PE would have to be extremely high (trans-critical operation) which is undesirable and difficult to achieve owing to the specialist equipment required. Thus, NH3 and CO2 do not represent meaningful alternatives to generate low pressure steam in polyolefin polymerisation plant applications.

[0099] Another important characteristic property for the selection of HP-media under process conditions is the volumetric heat capacity (VHC) of the generated vapours in the evaporator unit. VHC is a measure of the ability of the medium to evaporate with high heat / energy density. This property is especially important at the temperature level of the waste heat sources present in a polyolefin polymerisation plant as they are relatively low, and so could lead to very high mass transfer within the HP should a low VHC medium be used, which would be very inefficient. Conventional heat pump media show VHC-values between 1,500-3,500 kJ / m3in operation at typically application process conditions at the heat sink (ca. 70-90 °C).

[0100] Azeotropic mixtures of the disclosure as working fluids

[0101] This disclosure provides azeotropic mixtures suitable for use within High Temperature Heat Pumps. Specifically, these azeotropic mixtures show low boiling points at 1 bara at the temperature level of the waste heat source and higher latent heats than prior art heat pump media. The advantages of heat pump media of the disclosure can be seen from the table below. Pure cyclopentane has a AHevap= 411 kJ / kg, whereas the cyclopentane / ethanol azeotrope has a AHevap= 449 kJ / kg, i.e. the azeotrope has an increased latent heat meaning there can be energy savings when this is used as the working fluid. Thus, both the fullevaporation (maximal recoverable waste heat amount) at atmospheric or small over pressure and with high Volumetric Heat Capacities of the released vapours are present. High VHC-values reduce the flow charge on the following compressor and thus 1 -stage or 2-stage configurations with higher COP-values. Owing to the increased latent heat, smaller compressor sizes become feasible, which is overall more energetically efficient and more economical to run. Suitable azeotropic mixtures of the disclosure are provided in the table below.

[0102] Azeotropic mixtures formed with Ethanol (component 1)

[0103] Component Formula Boiling point of Amount of Heat of evaporation 2 azeotrope at 1 bara Ethanol, X1 azeotrope

[0104] (°C) (wt.%) (kJ / kg) Cyclopentan C5H10 44.7 7.5 449

[0105] e

[0106] Pentane C5H12 34.3 5.0 395

[0107] Benzene C6H667.9 31.7 587

[0108] Cyclohexane CeHi2 64.8 29.2 547

[0109] Hexane CeHi4 58.7 21 478

[0110] Toluene CyHs 76.7 68.1 754

[0111] Octane C8Hl8 77 78.0 796

[0112]

[0113] Prepolymerisation

[0114] Optionally the catalyst is pre-polymerised before entering the first reactor.

[0115] Producing the first polymer component

[0116] As discussed above, the process of the present disclosure comprises polymerising, in a reactor, first olefin monomer, optionally in the presence of at least one alpha olefin comonomer, in the presence of a polymerisation catalyst to produce a first polymer component. The first polymer component may be referred to as component (A).

[0117] Preferably, the first olefin monomer is propylene or ethylene, preferably ethylene.

[0118] The first olefin monomer may be polymerised to form a homopolymer as the first polymer component. Alternatively, the first olefin monomer may be polymerised to form a copolymerof the first olefin monomer and the at least one alpha olefin comonomer as the first polymer component.

[0119] For example, ethylene is polymerised in the first reactor to produce ethylene homopolymer as the first polymer component. Alternatively, ethylene may be co-polymerised with at least one alpha olefin comonomer to produce ethylene copolymer as the first polymer component. Examples of suitable alpha olefin comonomer include 1 -butene or 1 -hexene.

[0120] In one embodiment, propylene may be polymerised in the first reactor to produce propylene homopolymer as the first polymer component. Alternatively, propylene may be copolymerised with at least one alpha olefin comonomer to produce a propylene random copolymer as the first polymer component.

[0121] Where at least one alpha olefin comonomer is used, the at least one alpha olefin comonomer may be selected from a C2 to C10 alkene. For the avoidance of doubt, the alpha olefin comonomer is different from the first olefin monomer polymerised in the upstream reactor. Suitable alpha olefin comonomers include ethylene, propylene, 1 -butene, 1-pentene, 1 -hexene, 1 -heptene, 1 -hexene, 1 -octene, 1 -nonene and 1 -decene. Preferably, the alpha olefin comonomer is selected from at least one of ethylene, propylene, 1 -butene, 1-hexene, and 1 -octene. Where the first olefin monomer is propylene, the alpha olefin comonomer may be ethylene, 1 -butene, 1 -hexene and / or 1 -octene. Where the first olefin monomer is ethylene, the alpha olefin comonomer may be propylene, 1 -butene and / or 1-hexene. Where an alpha olefin comonomer is used, one or more alpha comonomers may be employed. Preferably, one or two alpha comonomers are employed.

[0122] Where the first polymer component is a polyethylene, the alpha olefin comonomer content may be 0 to 10 mol%, preferably 0 to 8 mol%, more preferably 0 to 6 mol%.

[0123] The upstream (first) polymerisation may take place in any suitable reactor or series of reactors. The upstream polymerisation step may take place in one or more slurry polymerisation reactor(s) or in a gas phase polymerisation reactor, or a combination thereof. In other words, the first polymer component may be formed by slurry polymerisation, preferably in slurry loop reactors.

[0124] Preferably the upstream polymerisation step may takes place in one or more slurry polymerisation reactor(s), more preferably in at least two (e.g., two) or at least three (e.g. three) slurry phase reactors.Slurry ethylene polymerisation may take place in an inert diluent, typically a hydrocarbon diluent such as, propane, n-butane, isobutane, pentanes, hexanes, heptanes, octanes etc., or their mixtures. Preferably the diluent is a low-boiling hydrocarbon having from 3 to 4 carbon atoms or a mixture of such hydrocarbons. An especially preferred diluent is propane. In bulk propylene polymerization, propylene is liquid and acts as monomer and is also the continuous liquid phase to facilitate mixing and heat transfer of the discrete polymerizing particles and reactants (monomer, co-monomer, chain transfer agent, catalyst components).

[0125] The temperature in the first polymerisation reactor may be from 20 to 115 °C, preferably from 25 to 110 °C and in particular from 30 to 100 °C.

[0126] Where the first polymerisation is carried out by slurry polymerisation, the slurry polymerisation may be conducted in any known reactor used for slurry polymerisation. Such reactors include a continuous stirred tank reactor and a loop reactor. It is especially preferred to conduct the polymerisation in loop reactor. In such reactors the slurry is circulated with a high velocity along a closed pipe by using a circulation pump. Loop reactors are generally known in the art and examples are given, for instance, in USA-4582816, US-A-3405109, US-A-3324093, EP-A-479186, and US-A-5391654. The slurry may be withdrawn from the reactor either continuously or intermittently. A preferred way of intermittent withdrawal is the use of settling legs where slurry is allowed to concentrate before withdrawing a batch of the concentrated slurry from the reactor. The use of settling legs is disclosed, among others, in US-A-3374211 , US-A-3242150 and EP- A-1310295. Continuous withdrawal is disclosed, among others, in EP-A-891990, EP-A- 1415999, EP-A-1591460 and WO-A-2007 / 025640. The continuous withdrawal is advantageously combined with a suitable concentration method, as disclosed in EP-A- 1310295, EP-A-1591460, and EP3178853B1.

[0127] Hydrogen may be fed into the reactor to control the molecular weight of the polymer as known in the art. Furthermore, one or more alpha-olefin comonomers may be added into the reactor to control the density of the polymer product. The actual amount of such hydrogen and comonomer feeds depends on the catalyst that is used and the desired melt index (or molecular weight) and density (or comonomer content) of the resulting polymer.

[0128] Second reactor

[0129] The first polymer component may be transferred to a second reactor, preferably a gas phase reactor.As mentioned above, polymerisation in the gas phase reactor involves polymerising a second olefin monomer and optionally at least one alpha olefin comonomer in the presence of the first polymer component.

[0130] As discussed above, the second olefin monomer is preferably the same as the first olefin monomer. For example, the first and second olefin monomers may be propylene.

[0131] Alternatively, the first and second olefin monomers may be ethylene.

[0132] The second olefin monomer may be polymerised in the downstream gas phase reactor to form a homopolymer as the second polymer component (also referred to as component B). Alternatively, the second olefin monomer may be polymerised to form a copolymer of the second olefin monomer and the at least one alpha olefin comonomer as the second polymer component.

[0133] For example, propylene may be polymerised in the downstream gas phase reactor to produce propylene homopolymer as the second polymer component. Alternatively, propylene may be co-polymerised with at least one alpha olefin comonomer to produce a propylene copolymer as the second polymer component.

[0134] Preferably, ethylene may be co-polymerised with at least one alpha olefin comonomer to produce ethylene copolymer as the second polymer component.

[0135] Where an alpha olefin comonomer is used, the alpha olefin comonomer may be selected from a C2 to C10 alkene. For the avoidance of doubt, the alpha olefin comonomer is different from the first olefin monomer polymerised in the upstream reactor. Suitable alpha olefin comonomers include ethylene, propylene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, , 1-octene, 1 -nonene and 1 -decene. Preferably, the alpha olefin comonomer is selected from at least one of ethylene, propylene, 1 -butene, 1 -hexene and 1 -octene. Where the first olefin monomer is propylene, the alpha olefin comonomer may be ethylene, 1 -butene, 1 -hexene and / or 1 -octene. Where the first olefin monomer is ethylene, the alpha olefin comonomer may be propylene, 1 -butene, 1 -hexene, and / or 1 -octene. Where an alpha olefin comonomer is used, one or more alpha comonomers may be employed. Preferably, one or two alpha comonomers are employed.

[0136] The same or different alpha olefin comonomer may bs used to form the first polymer component and second polymer component. Alternatively either or both of the first polymer component and second polymer components is a homopolymer.The downstream polymerisation may take place in one or more gas phase polymerisation reactor(s) to produce the second polymer component.

[0137] The gas phase polymerisation may be conducted in any known reactor used for gas phase polymerisation. Such reactors include a fluidized bed reactor and a fast fluidized bed reactor or in any combination of these. When a combination of reactors is used then the polymer is transferred from one polymerisation reactor to another. Furthermore, a part or whole of the polymer from a polymerisation stage may be returned into a prior polymerisation stage.

[0138] The temperature in the gas phase polymerisation may be from 50 to 100 °C, preferably from 65 to 95 °C.

[0139] The operating pressure in the gas phase polymerisation may be from 5 to 30 barg. For example, 5 to 29 barg. Preferably, the operating pressure may be 10 to 27 barg, yet more preferably 15 to 22 barg. Where the second olefin monomer is propylene, the operating pressure may be 5 to 30 barg, more preferably 10 to 27 barg, yet more preferably 15 to 25 barg, most preferably 15 to 22 barg.

[0140] The gas phase polymerisation is preferably conducted in a gas-solids fluidized bed(s).

[0141] An example of a suitable downstream gas phase polymerisation reactor may comprise three zones: a) a bottom zone where fluidization gas is introduced into the reactor; b) a middle zone, which may have a generally cylindrical shape, where olefin monomer(s) present in the fluidization gas are polymerised to form the polymer particles; and c) a top zone, where fluidization gas is withdrawn from the reactor. A fluidization grid (also named distribution plate) may be employed to separate the bottom zone from the middle zone. The top zone may also act as a disengaging zone or freeboard in which, due to its expanding diameter compared to the middle zone, the fluidization gas velocity reduces and so to disengage polyolefin powder from the fluidization gas to minimise entrainment

[0142] Prior to being reintroduced into the gas phase reactor as or as part of the fluidisation gas, the withdrawn stream may be compressed in a compressor and cooled. Additional olefin monomer(s), eventual comonomer(s), hydrogen and inert gas are suitably introduced into the circulation gas line. It is preferred to analyse the composition of the circulation gas, for instance, by using on-line gas chromatography and adjust the addition of the gas components so that their contents are maintained at desired levels.Preferably the fluidisation gas is cooled in at least one heat exchanger. More preferably the fluidisation gas is cooled by at least two heat exchangers, the first heat exchanger is preferably cooling the fluidisation gas by cooling water and the second heat exchanger cools the fluidisation gas by the working fluid.

[0143] Preferably the first heat exchanger is located between the second heat exchanger and the bottom zone of the gas phase reactor. More preferably the compressor is located between the top zone of the reactor and the first heat exchanger.

[0144] Polymer products of this invention may be high-density polyethylene (HDPE) or linear-low-density polyethylene (LLDPE) or polyethylene with any density in between (MDPE) where ethylene is used as the olefin monomer. Polymer products of this invention may be homopolypropylene, random-polypropylene-copolymer, heterophasic polypropylene copolymer or random-heterophasic polypropylene copolymer where propylene is used as the olefin monomer.

[0145] Polymerization catalyst

[0146] The polymerization in the multi-stage olefin polymerization reactors is conducted in the presence of an olefin polymerization catalyst. The catalyst may be any catalyst which is capable of producing the desired olefin polymer. Suitable catalysts are, among others, Ziegler - Natta catalysts based on a transition metal, such as titanium, zirconium and / or vanadium catalysts. Especially Ziegler-Natta catalysts are useful as they can produce olefin polymers within a wide range of molecular weight with a high productivity.

[0147] Suitable Ziegler-Natta catalysts preferably contain a magnesium compound, an aluminium compound and a titanium compound supported on a particulate support.

[0148] The particulate support can be an inorganic oxide support, such as silica, alumina, titania, silica-alumina and silica-titania. In some embodiments, magnesium chloride may also be employed.

[0149] The average particle size of the silica support can be typically from 6 to 100 pm. However, it has turned out that special advantages can be obtained if the support has median particle size from 6 to 90 pm, preferably from 10 to 70 pm.

[0150] The magnesium compound may be a reaction product of a magnesium dialkyl and an alcohol. The alcohol is a linear or branched aliphatic mono-alcohol. Preferably, the alcohol has from 6 to 16 carbon atoms. Branched alcohols are especially preferred, and 2-ethyl-1 -hexanol is one example of the preferred alcohols. The magnesium dialkyl may be any compound of magnesium bonding to two alkyl groups, which may be the same or different. Butyl-octyl magnesium is one example of the preferred magnesium dialkyls.

[0151] The aluminium compound may be chlorine containing aluminium alkyl. Especially preferred compounds are aluminium alkyl dichlorides and aluminium alkyl sesquichlorides.

[0152] The titanium compound may be a halogen containing titanium compound, preferably chlorine containing titanium compound. Especially preferred titanium compound is titanium tetrachloride.

[0153] The catalyst can be prepared by sequentially contacting the carrier with the above mentioned compounds, as described in EP-A-688794 or WO-A-99 / 51646 . Alternatively, it can be prepared by first preparing a solution from the components and then contacting the solution with a carrier, as described in WO-A-01 / 55230 .

[0154] Another group of suitable Ziegler-Natta catalysts contains a titanium compound together with a magnesium halide compound acting as a support. Thus, the catalyst contains a titanium compound on a magnesium dihalide, like magnesium dichloride. Such catalysts are disclosed, for instance, in WO-A-2005 / 118655 and EP-A-810235 .

[0155] Still a further type of Ziegler-Natta catalysts are catalysts prepared by a method, wherein an emulsion is formed, wherein the active components form a dispersed, i.e. a discontinuous phase in the emulsion of at least two liquid phases. The dispersed phase, in the form of droplets, is solidified from the emulsion, wherein catalyst in the form of solid particles is formed. The principles of preparation of these types of catalysts are given in WO-A-2003 / 106510 of Borealis.

[0156] The Ziegler-Natta catalyst can be used together with an activator. Suitable activators are metal alkyl compounds and especially aluminium alkyl compounds. These compounds include alkyl aluminium halides, such as ethylaluminium dichloride, diethylaluminium chloride, ethylaluminium sesquichloride, dimethylaluminium chloride and the like. They also include trialkylaluminium compounds, such as trimethylaluminium, triethylaluminium, triisobutylaluminium, trihexylaluminium and tri-n-octylaluminium. Furthermore they include alkylaluminium oxy-compounds, such as methylaluminiumoxane (MAO), hexaisobutylaluminiumoxane (HIBAO) and tetraisobutylaluminiumoxane (TIBAO). Other aluminium alkyl compounds, such as isoprenylaluminium, may also be used. Especiallypreferred activators are trialkylaluminiums, of which triethylaluminium, trimethylaluminium and tri-isobutylaluminium are particularly used. If needed the activator may also include an external electron donor. Suitable electron donor compounds are disclosed in WO-A-95 / 32994 , US-A-4107414 , US-A-4186107 , US-A-4226963 , US-A-4347160 , US-A-4382019 , US-A-4435550 , US-A-4465782 , US 4472524 , US-A-4473660 , US-A-4522930 , US-A-4530912 , US-A-4532313 , US-A-4560671 and US-A-4657882 . Also electron donors consisting of organosilane compounds, containing Si-OCOR, Si-OR, and / or Si-NR2 bonds, having silicon as the central atom, and R is an alkyl, alkenyl, aryl, arylalkyl or cycloalkyl with 1-20 carbon atoms are known in the art. Such compounds are described in US-A-4472524 , US-A-4522930 , US-A-4560671 , US-A-4581342 , US-A-4657882 , EP-A-45976 , EP-A-45977 and EP-A-1538167 .

[0157] The amount in which the activator is used depends on the specific catalyst and activator.

[0158] Typically triethylaluminium is used in such amount that the molar ratio of aluminium to the transition metal, like Al / Ti, is from 1 to 1000, preferably from 3 to 100 and in particular from about 5 to about 30 mol / mol.

[0159] Metallocene catalysts may also be used. Metallocene catalysts comprise a transition metal compound which contains a cyclopentadienyl, indenyl or fluorenyl ligand. Preferably the catalyst contains two cyclopentadienyl, indenyl or fluorenyl ligands, which may be bridged by a group preferably containing silicon and / or carbon atom(s). Further, the ligands may have substituents, such as alkyl groups, aryl groups, arylalkyl groups, alkylaryl groups, silyl groups, siloxy groups, alkoxy groups or other heteroatom groups or the like. Suitable metallocene catalysts are known in the art and are disclosed, among others, in WO-A-95 / 12622 , WO-A-96 / 32423 , WO-A-97 / 28170 , WO-A-98 / 32776 , WO-A-99 / 61489 , WO-A-03 / 010208 , WO-A-03 / 051934 , WO-A-03 / 051514 , WO-A-2004 / 085499 , EP-A-1752462 and EP-A-1739103 .

[0160] Figures

[0161] These and other aspects of the present disclosure will now be described, by way of example, with reference to the accompanying drawings. Figure 1 is a graph showing results from pinch analysis of a Borstar PE polymerisation process.

[0162] Figure 1 depicts a lumped composite curve for a Borstar polyethylene plant, the energy needed is normalised per ton produced polyethylene. The composite curves for both hot streams and cold streams have been shifted by 6°C, this gives a minimum temperaturel ' l

[0163] difference of 12°C. The hot streams are all process streams lumped per temperature interval which need to be cooled, and are not necessarily having a high temperature, e.g. the heat removal of the reactors, condensers in the recovery section. Cold streams are all process streams lumped per temperature interval which would require heating, e.g. reboilers in the recovery, heaters and evaporators. The pinch temperature is where the hot and cold curves meet each other, where the temperature difference is at a minimum. Figure 1 clearly shows that heat integration is limited within the process and most energy is available below the pinch temperature, while some cold streams need to be heated to temperatures much higher than is available. A high temperature heat pump shall lift the energy from below the pinch to a temperature above the pinch to be able to utilize the energy efficient. Hence all hot streams above the pinch can easily be used for heat integration by cross heat exchangers to heat up cold streams to desired temperature.

[0164] Figure 2 shows a possible integration of a high temperature heat pump with a gas phase polymerisation reactor.

[0165] 1 Gas phase reactor

[0166] 2 circulation gas compressor

[0167] 3 first heat exchanger

[0168] 4 second heat exchanger

[0169] 5 inter heat exchanger of working fluid

[0170] 6 heat pump compressor

[0171] 7 heat sink

[0172] 8 optional after cooler

[0173] 9 optional condensed work fluid vessel

[0174] 10 feed stream to the reactor

[0175] 11 feed stream to gas circulation stream

[0176] 12 reactor effluent, hence product outlet

[0177] 13 gas circulation stream out of reactor

[0178] 14 compressed gas circulation stream

[0179] 15 pre-cooled gas circulation stream

[0180] 16 gas circulation stream to reactor inlet

[0181] 17 (partly) condensed working fluid stream fed to the heat exchanger

[0182] 18 evaporated working fluid

[0183] 19 superheated working fluid vapour

[0184] 20 compressed working fluid vapour21 condensed working fluid

[0185] 22 cooled working fluid

[0186] 23 optional sub cooled working fluid

[0187] 24 stream feeding to heat sink

[0188] 25 stream removing from heat sink

[0189] Figure 3 shows an arrangement of a high temperature heat pump with a loop reactor for olefin polymerizations in slurry or bulk phase.

[0190] 30 Loop reactor

[0191] 31 jacket water pump

[0192] 32 first jacket water heat exchanger

[0193] 33 second jacket water heat exchanger

[0194] 34 reactor feed streams

[0195] 35 effluent stream from reactor

[0196] 36 cooled jacket water feed to the loop reactor jacket(s)

[0197] 37 jacket water connection from jacket of leg 1 to jacket of leg 2

[0198] 38 jacket water outlet stream

[0199] 39 pre-cooled jacket water

[0200] 40 cooled jacket water

[0201] The other equipment and streams are similar to figure 2 and have identical numbers as figure 2.

[0202] Figure 4 presents a T-xy diagram of cyclopentane and ethanol at 1 bar absolute pressure in molar fraction. The vapour-liquid equilibria show that the at the azeotropic point the boiling point of the azeotrope is lower than the boiling point of the pure components and other mixtures of cyclopentane and ethanol. Cyclopentane relative amount is on the x-axis, hence a 0 mol fraction means 1 mol fraction of ethanol.

[0203] The T-xy diagrams included herein (Figures 4-6) present the temperature versus liquid (x) and vapor (y) composition for isobaric Vapour-Liquid Equilibrium (VLE) data.

[0204] The temperature is plotted on the vertical axis versus the mole fraction in liquid (x) and vapour (y) on the horizontal axis. As such the T-xy diagrams are phase diagrams is obtained for particular binary mixtures. By way of example, in Figure 4 the cyclopentane concentration in liquid is x with ethanol mole fraction is 1-x. Above the line y the mixture is in vapour phase, the boiling curve. Below the line x the mixture is in liquid phase, condensation curve.

[0205] Between the x and y lines vapour and liquid are both present and the mixture can be separated by distillation. The point where the mixture in the Txy diagram are having asimilar vapour and liquid composition is the azeotropic point. Note in figure 4 at x=0 this means pure ethanol and x=1 pure cyclopentane. As shown in Figure 4, for the binary mixture of cyclo-pentane and ethanol the azeotropic point at 0 barg is around x=0.9 mol fraction.

[0206] Figure 5 presents a T-xy diagram of n-pentane and ethanol at atmospheric pressure (0 barg) in molar fraction. The vapour-liquid equilibria show that the at the azeotropic point the boiling point of the azeotrope is lower than the boiling point of the pure components and other mixtures of n-pentane and ethanol. n-Pentane molar fraction is on the x-axis.

[0207] Figure 6 presents a T-xy diagram of 2,2-dimethylbutane and ethanol at 1 bar absolute pressure in molar fraction. The vapour-liquid equilibria show that the at the azeotropic point the boiling point of the azeotrope is lower than the boiling point of the pure components and other mixtures of 2,2-dimethylbutane and ethanol. 2,2-Dimethylbutane relative amount is on the x-axis in molar fraction.

[0208] Examples

[0209] The Examples below demonstrate a number of benefits of the methods of the disclosure, including but not limited to:

[0210] Very high valorisation of waste heat from Gas Phase Reactor gas circulation cooling is feasible

[0211] An overall decrease in further decrease in energy consumption of the polymerisation plant using the methods of the disclosure when compared with conventional HTHP using water as a working fluid.

[0212] Reduction in effective energy consumption of HTHP-systems

[0213] Reduction of compressor work versus known HTHP-systems by decreasing the gas flow charges, besides further reduction effects, e.g., isentropic coefficient K = ca. 1,13 versus 1 ,33 for water.

[0214] The methods of the disclosure can be applied to different polymerisation plants, for example polyethylene and polypropylene plants (e.g. Borstar PE and Borstar PP). The technical concept can be applied to any production plant, especially to those having a 1st GPR gas circulation cooler and / or 2nd GPR gas circulation cooler, optionally also to Polymerisation Loop reactors that may be present in such plants.

[0215] A schematic illustration of the closed cycle HTHP-configuration design is shown in Figure 2. The second heat exchanger (4) may evaporate the working fluid with the waste heat of the Gas Phase Reactor while cooling the circulation gas,. Condensation in the compressors can be avoided by an inter heat exchanger (5), this cross heat exchanger superheats theworking fluid vapour and on the ‘hot’ side of the heat exchanger the condensed working fluid is cooled a bit before the pressure of the working fluid is lowered.. The working fluid vapour is compressed by a compressor (6) and the heat from the vapour working fluid is transferred in the examples to low pressure condensate resulting in a low pressure steam. The heat sink (7) in the examples described is an evaporator and evaporates low pressure condensate and forms so low pressure steam, which can be utilised within the process to heat the ‘gold’ streams (reference figure 1).

[0216] The vapour liquid phase diagram of the azeotropic mixtures utilised in the examples are presented in figure 4, 5 and 6 as Txy diagrams at atmospheric pressure. Typical the heat pump operates at an elevated pressure in both the second heat exchanger and at the sink. Furthermore, pure cyclopentane has been already theoretical investigated by the inventors, where the HTHP was found to have a COP ~ 3.2.

[0217] All examples have been simulated by using Aspen HYSYS V14. Used herein the term LPS refers to low pressure steam. Heat pumps require optimisation in order to function most efficiently, for example too high temperature in the compressor inlet can lead to inefficient compression. The skilled person would be aware how to optimise heat pumps. In the following comparative examples and inventive examples, each heat pump has been optimised in order to prevent condensation in the compressor and to minimize electrical duty for the compressor and obtain the desired amount of low pressure steam .

[0218] All examples are based on a arrangement as presented in figure 2. The optional after cooler (8) has not been used in the examples, hence the duty of this heat exchanger is in all inventive and comparative examples zero.

[0219] Comparative example 1A

[0220] The process according to figure 2 was used. The working fluid in CE1A is pure cyclopentane.

[0221] For a production of about 12.7 ton / h low pressure steam at 5.3 bara 5.5 MW of heat is removed from the gas circulation by the working fluid with a flow of about 72 ton / h. The working fluid evaporates at about 1.85 bara in the second heat exchanger (4) and the vapour is compressed (6) to 14 bara. The electrical energy is calculated about 2.6 MW (excluding losses). The energy delivered at the sink (7) is 8.1 MW The low pressure condensate is fed to the steam evaporator (7) at 105°C. The vapour is pre-heated in the inter heat exchanger (5) upstream of the heat pump compressor to about 107°C. Note this is an optimisation to improve the heat pump performance and maximise the energy delivered at the sink. The COP is about 3.11.Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction (- ) 1 1 1 0.27 1 1 1 0 0 0.27 0 1 Temperature (°C) 85.0 90.2 79.1 68.9 68.9 107.0 180.6 140.0 116.1 68.9 105.0 154.2 Pressure (Bara) 20.6 22.4 22.35 1.85 1.85 1.85 14 14 14 1.85 5.3 5.3 Mass flow (ton

[0222] / h) 1039 1039 1039 72 72 72 72 72 72 72 12.7 12.7 Water (wt

[0223] fraction) 0 0 0 0 0 0 0 0 0 0 1 1 Cyclopentane (wt

[0224] fraction) 0 0 0 1 1 1 1 1 1 1 0 0 Monomer 1 (wt

[0225] fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0 Comonomer 1

[0226]

[0227] (wt fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

[0228] Inventive example 1

[0229] The process according to figure 2 was used. The working fluid in IE1 is a mixture of cyclopentane and ethanol at an azeotropic composition. The ethanol mass fraction is 7.51 wt% and the cyclopentane mass fraction 92.49 wt%. For a production of about 12 ton / h LPS 5.5 MW heat is removed from the Gas circulation by the working fluid with a flow of about 65 ton / h. The working medium is evaporated in the second heat exchanger (4) at about 2.2

[0230] bara and compressed to a pressure of about 18.5 bara by the heat pump compressor (6).

[0231] The electrical duty is about 2.3 MW The energy delivered at the sink (7) is about 7.8 MW

[0232] The evaporator (7) produces about 12.2 ton / h low pressure steam at 5.3 bara from a condensate at a temperature of about 105°C. The inter heat exchanger (5) is pre-heating the vapour to about 107.7°C. The calculated COP is 3.41. The higher COP of this example relative to CE1A and CE1B demonstrates that, for a comparative heat transfer process, the use of an azeotrope as the working fluid is associated with a more efficient heat pump than a pure single component working fluid.

[0233] Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour

[0234] fraction (-) 1 1 1 0.26 1 1 1 0 0 0.26 0 1 Temperature

[0235] (°C) 85.0 90.2 79.1 68.0 71.4 107.7 178.9 140.0 118.1 68.0 105.0 154.1 Pressure

[0236] (Bara) 20.6 22.4 22.35 2.2 2.2 2.2 18.5 18.5 18.5 2.2 5.3 5.3 Mass flow

[0237] (ton / h) 1039 1039 1039 65 65 65 65 65 65 65 12.2 12.2 Water (wt

[0238] fraction) 0 0 0 0 0 0 0 0 0 0 1 1 Ethanol (wt

[0239] fraction) 0 0 0 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0 0 Cyclopentane

[0240]

[0241] (wt fraction) 0 0 0 0.925 0.925 0.925 0.925 0.925 0.925 0.925 0 0Monomer 1

[0242] (wt fraction) 0.048 0.048 0.048 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Comonomer

[0243]

[0244] 1 (wt fraction) 0.008 0.008 0.008 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

[0245] Comparative example 1 B

[0246] The process according to figure 2 was used. The working fluid in CE1 B is pure

[0247] cyclopentane.

[0248] The steam production in CE1 A can be reduced to produce the same amount of steam as in IE1 by increasing the set point of the gas temperature to 79.55°C downstream the second heat exchanger (4). The working fluid mass flow is reduced to 69 ton / h and removing only

[0249] 5.3 MW via the second heat exchanger from the gas circulation flow (stream 14 figure 2).

[0250] The compressor (6) duty is 2.5 MW and the heat rejected at the sink (7) is 7.8 MW resulting in 12.2 ton / h low pressure steam exact the same energy is delivered as in IE1. The COP is however still 3.11.

[0251] Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction

[0252] (-) 1 1 1 0.27 1 1 1 0 0 0.27 0 1 Temperature

[0253] (°C) 85.0 90.2 79.5 68.9 68.9 107.0 180.6 140.0 116.1 68.9 105.0 154.1

[0254] Pressure (Bara) 20.6 22.4 22.35 1.85 1.85 1.85 14 14 14 1.85 5.3 5.3 Mass flow (ton

[0255] / h) 1039 1039 1039 69 69 69 69 69 69 69 12.2 12.2 Water (wt

[0256] fraction) 0 0 0 0 0 0 0 0 0 0 1 1 Cyclopentane

[0257] (wt fraction) 0 0 0 1 1 1 1 1 1 1 0 0 Monomer 1 (wt

[0258] fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0 Comonomer 1

[0259]

[0260] (wt fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

[0261] Comparative example 2

[0262] The process according to figure 2 was used. The working fluid in CE2 is pure n-pentane.For a production of about 12.2 ton / h low pressure steam at 5.3 bara 4.9 MW of heat is removed from the gas circulation by the working fluid with a flow of about 86 ton / h. The

[0263] working fluid evaporates at about 2.45 bara in the second heat exchanger (4) and the

[0264] vapour is compressed to 17.8 bara by the heat pump compressor (6). The electrical energy required by the compressor (6) is calculated to be about 3.0 MW (excluding losses). The

[0265] energy delivered at the sink is about 7.8 MW The low pressure condensate is fed to the

[0266] steam evaporator at 105°C. The vapour is pre-heated in the inter heat exchanger (5)

[0267] upstream of the heat pump compressor to about 115°C. Note this is an optimisation to

[0268] improve the heat pump performance and maximise the energy delivered at the sink. The

[0269] COP is about 2.65.

[0270] Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction (-) 1 1 1 0.39 1 1 1 0 0 0.39 0 1 Temperature (°C) 85.0 90.2 80.3 64.8 64.8 115.0 171.8 146.0 113.7 64.8 105.0 154.2 Pressure (Bara) 20.6 22.4 22.35 2.45 2.45 2.45 17.8 17.8 17.8 2.45 5.3 5.3 Mass flow (ton / h) 1039 1039 1039 85.7 85.7 85.7 85.7 85.7 85.7 85.7 12.3 12.3 Water (wt fraction) 0 0 0 0 0 0 0 0 0 0 1.00 1.00 Ethanol (wt fraction) 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0 0 n-pentane (wt fraction) 0 0 0 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0 0 Monomer 1 (wt fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0 Comonomer 1 (wt

[0271]

[0272] fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

[0273] Inventive example 2

[0274] The process according to figure 2 was used. The working fluid in IE2 is a mixture of

[0275] n-pentane and ethanol at an azeotropic composition. The ethanol mass fraction is about

[0276] 4.25 wt% and the n-pentane mass fraction is about 95.75 wt%. Figure 5 shows the Txy

[0277] diagram for n-pentane and ethanol at atmospheric pressure. For a production of about 12

[0278] ton / h LPS 5.0 MW heat is removed from the Gas circulation by the working fluid with a flow of about 80 ton / h. The working medium is evaporated in the second heat exchanger (4) at about 2.6 bara and compressed to a pressure of about 19.5 bara by the heat pump

[0279] compressor (6). The electrical duty is about 2.9 MW The energy delivered at the sink is

[0280] about 7.8 MW The evaporator (7) produces about 12.2 ton / h low pressure steam at 5.3 bara from a condensate at a temperature of about 105°C. The inter heat exchanger (5) is preheating the vapour to about 114.5°C. The calculated COP is 2.71. The higher COP of this example relative to CE2 demonstrates that, for a comparative heat transfer process, the use of an azeotrope as the working fluid is associated with a more efficient heat pump than a

[0281] pure single component working fluid.Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction (-) 1 1 1 0.38 1 1 1 0 0 0.38 0 1 Temperature (°C) 85.0 90.2 80.2 65.4 65.7 114.5 174.0 146.0 115.3 65.4 105.0 154.3 Pressure (Bara) 20.6 22.4 22.35 2.6 2.6 2.6 19.5 19.5 19.5 2.6 5.3 5.3 Mass flow (ton / h) 1039 1039 1039 80.2 80.2 80.2 80.2 80.2 80.2 80.2 12.3 12.3 Water (wt fraction) 0 0 0 0 0 0 0 0 0 0 1.00 1.00 Ethanol (wt

[0282] fraction) 0 0 0 0.0425 0.0425 0.0425 0.0425 0.0425 0.0425 0.0425 0 0 n-pentane (wt

[0283] fraction) 0 0 0 0.9575 0.9575 0.9575 0.9575 0.9575 0.9575 0.9575 0 0 Monomer 1 (wt

[0284] fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0 Comonomer 1 (wt

[0285]

[0286] fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

[0287] Inventive example 3

[0288] The process according to figure 2 was used. An azeotropic mixture is used of 2,2-dimethylbutane and ethanol with about 7 wt% ethanol and 93 wt% 2,2-dimethylbutane.

[0289] For the production of 12 ton / h low pressure steam, about 5.6 MW heat is removed from the gas circulation flow in the second heat exchanger (4) by a working fluid flow of about 83

[0290] ton / h. The working medium is vaporising at 1.8 bara and compressed after inter heat

[0291] exchanger to 18.4 bara. The inter heat exchanger (5) is superheating the vapor to about

[0292] 115°C. The calculated duty of the compressor (6) is 2.1 MW

[0293] The heat delivered at the heat sink is 7.7 MW Condensate fed to evaporator (7) is at same conditions as in example 1.

[0294] The Coefficient of performance is calculated and is for this case 3.6. The higher COP of this example relative to CE3 demonstrates that, for a comparative heat transfer process, the use of an azeotrope as the working fluid is associated with a more efficient heat pump than a

[0295] pure single component working fluid.

[0296] Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction (-) 1 1 1 0.31 1 1 0.97036 0 0 0.31 0 1 Temperature (°C) 85.0 90.2 78.9 62.2 64.9 115.1 171.8 146.0 113.1 62.2 105.0 156.6 Pressure (Bara) 20.6 22.4 22.35 1.8 1.8 1.8 18.4 18.4 18.4 1.8 5.3 5.3 Mass flow (ton Zh) 1039 1039 1039 83.3 83.3 83.3 83.3 83.3 83.3 83.3 12.0 12.0 Water (wt fraction) 0 0 0 0 0 0 0 0 0 0 1.00 1.00 Ethanol (wt fraction) 0 0 0 0.071 0.071 0.071 0.071 0.071 0.071 0.071 0 0 2,2 dimethylbutane

[0297] (wt fraction) 0 0 0 0.929 0.929 0.929 0.929 0.929 0.929 0.929 0 0 Monomer 1 (wt

[0298] fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0 Comonomer 1 (wt

[0299]

[0300] fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

[0301] Comparative example 3

[0302] The process according to figure 2 was used. The working fluid in CE3 is pure 2,2-dimethylbutane.For a production of about 12 ton / h low pressure steam at 5.3 bara 5.1 MW of heat is removed from the gas circulation by the working fluid with a flow of about 88 ton / h. The

[0303] working fluid evaporates at about 1.55 bara in the second heat exchanger (4) and the

[0304] vapour is compressed to 12.4 bara by the heat pump compressor (6). The electrical energy is calculated about 2.7 MW (excluding losses). The energy delivered at the sink is about 7.7 MW The low pressure condensate is fed to the steam evaporator (7) at 105°C. The working fluid vapour is pre-heated in the inter heat exchanger (5) upstream of the heat pump compressor (6) to about 111 °C. Note this is an optimisation to improve the heat pump performance and maximise the energy delivered at the sink. The COP is about 2.9.

[0305] Stream 13 14 15 17 18 19 20 21 22 23 24 25 Vapour fraction (-) 1 1 1 0.34 1 1 1 0 0 0.34 0 1 Temperature (°C) 85.0 90.2 80.0 63.5 63.5 111.5 173.2 145.0 112.2 63.5 105.0 154.2 Pressure (Bara) 20.6 22.4 22.35 1.55 1.55 1.55 12.4 12.4 12.4 1.55 5.3 5.3 Mass flow (ton / h) 1039 1039 1039 87.8 87.8 87.8 87.8 87.8 87.8 87.8 12.1 12.1 Water (wt fraction) 0 0 0 0 0 0 0 0 0 0 1.00 1.00 Ethanol (wt fraction) 0 0 0 0 0 0 0 0 0 0 0 0 2,2 dimethylbutane (wt

[0306] fraction) 0 0 0 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0 0 Monomer 1 (wt fraction) 0.048 0.048 0.048 0 0 0 0 0 0 0 0 0

[0307]

[0308] Comonomer 1 (wt fraction) 0.008 0.008 0.008 0 0 0 0 0 0 0 0 0

Claims

Claims1. A method for waste heat recovery from a plant for polymerising olefins, the method comprising transferring heat from a stage of the polymerisation process to a working fluid of a heat pump, wherein the working fluid of the heat pump comprises an azeotrope comprising a first component and a second component, wherein the first component is an organic component, and wherein said azeotrope has a boiling point at 1 bara that is lower than the boiling point of said organic component in its pure form, at 1 bara, and a heat of evaporation that is greater than the heat of evaporation of said organic component in its pure form.

2. A method of claim 1, wherein the organic component is a hydrocarbon, preferably, a Cs to C12 hydrocarbon, more preferably a C5 to C9 hydrocarbon.

3. A method as claimed in claim 2, wherein the hydrocarbon is selected from alkanes, cycloalkanes, alkenes, cycloalkenes, and iso-alkenes, preferably cyclopentane, pentane, hexane, iso-pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2- methylpentane, 3-methylpentane, cyclohexane, n-hexane, n-heptane, 2- methylhexane, 3-methylhexane and octane.

4. A method as claimed in any one of the preceding claims, wherein the second component is an alcohol, preferably ethanol.

5. A method as claimed in claim 4, wherein the azeotrope comprises 3 to 80 weight % alcohol.

6. A method as claimed in any one of the preceding claims, wherein the boiling point of the azeotrope at 1 bara is 30 to 80 °C and the heat of vaporisation of the azeotrope if 360 to 900 kJ / kg.

7. A method as claimed in any one of the preceding claims, wherein the boiling point of the organic component in its pure form at 1 bara is 28 to 127 °C, and / or wherein the heat of vaporisation of the organic component in its pure form is 295 to 410 kJ / kg.

8. A method as claimed in any one of the preceding claims, wherein the boiling point of the azeotrope is lower than the boiling point of the second component in its pure form and / or the heat of vaporisation of the azeotrope is at least 5% higher than that of the organic component in its pure form.

9. A method as claimed in any one of the preceding claims, wherein the azeotrope is a binary mixture.

10. A method as claimed in any one of the preceding claims, wherein the heat pump is a high temperature heat pump.

11. A method as claimed in any one of the preceding claims, wherein heat is transferred from a polymerisation reactor, preferably a gas phase polymerisation reactor and / or a loop reactor.

12. A method as claimed in any one of the preceding claims, wherein the heat transferred to the working fluid is used to evaporate the working fluid thereby providing a working fluid vapour, and wherein heat is removed from the working fluid vapour by an external water stream to condense the working fluid vapour and generate steam, by evaporation of the external water stream, for use in the process.

13. A method as claimed in any one of the preceding claims, which is a method for waste heat recovery from a plant for polymerising propylene and / or ethylene.

14. A multistage polymerisation process comprising polymerisation of olefins in a first reactor to produce a first polymer component and polymerisation of olefins in a second reactor, preferably a gas phase reactor, to produce a second polymer component in the presence of the first polymer component, and wherein heat from the first reactorand / or the second reactor is recovered in accordance with the method according to any one of claims 1-13.

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