Heat pump

Abstract

A heat pump (200) for receiving a waste steam stream (201) and producing a process steam stream (202) in use, the heat pump (200) comprising, arranged in series in a closed loop (203): a waste steam condenser (204) fluidly connected to; a compressor (205) fluidly connected to; a process steam generator (206) fluidly connected to; an expansion valve (207) fluidly connected to the waste steam condenser (204); such that in use a refrigerant can circulate around the closed loop (203); wherein the compressor (205) is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use; the expansion valve (207) is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use; the waste steam condenser (204) is configured to receive a waste steam stream (201) and transfer heat from the waste steam stream (201) to the refrigerant in use; and the process steam generator (206) is configured to receive water (208) and transfer heat from the refrigerant to the water (208) to produce a process steam stream (202) in use.

Description

FIELD The present invention relates to heat pumps. More specifically the present invention relates to heat pumps for receiving waste steam. BACKGROUND Prior art closed loop heat pumps circulate a refrigerant around a closed loop to transfer heat from a heat source to a heat sink. The heat source can be a waste stream in an industrial process and the heat sink can be a process stream in the industrial process. The heat pump is therefore used to take heat from the waste stream of the industrial process and transfer the heat to a process stream in the industrial process. Throughout the following description the terms waste steam and process steam are used. These terms are firstly clarified. Waste steam typically refers to steam that has been used in an industrial or commercial process and therefore has a lower exergy level. In many industrial processes, steam is used fortasks such as heating, sterilisation, or mechanical work. After performing its intended function, the steam may become waste steam because it has given up its heat energy to the process. Waste steam is typically at a low temperature level (between 50 degree Celsius and 110 degrees Celsius). The waste steam has a lower exergy than the process steam. The waste steam may be low pressure or vacuum steam in some examples, which can be used only for more minor specific processes, such as pre-heating, rather than the main industrial process. Waste steam may still contain some residual heat, and efforts are often made to recover and reuse this heat energy rather than letting it dissipate into the environment. This process is known as steam condensate recovery. By capturing and utilising waste 2 steam heat, industries can improve energy efficiency and reduce overall energy consumption. In summary, waste steam is steam that can be challenging to use in an industrial process because of its low temperature. The waste steam may have been used in an industrial process and has released a significant amount of exergy, in such cases it is often considered as a by-product. Waste steam can either not be used anymore or be only used for pre-heating of processes due to its low temperature level. Typically, waste steam is condensed at the end of the process by use of a cooling tower such that the waste steam can be safely ejected to the atmosphere. Typically, the energy in the waste steam is not usefully captured. Efforts to recover and reuse the heat from waste steam are part of sustainable and energy-efficient practices in various industries. Waste steam may also be referred to as depleted steam or used steam. The waste steam need not always be polluted steam. It will become apparent to the person skilled in the art that the invention later described is particularly advantageous when the steam is polluted, but the invention later described functions equally well with entirely non-polluted or minimally polluted waste steam. Process steam refers to steam that is specifically generated and used in industrial processes. Many industries use steam as a heat transfer medium or for various applications such as heating, sterilisation, drying, and mechanical work. The term process steam distinguishes steam used in these industrial processes from other types of steam applications, such as power generation or space heating. In industrial settings, boilers are commonly used to generate process steam by heating water to its boiling point. The resulting steam is then transported to different parts of the facility to carry out specific tasks within the manufacturing or production 3 processes. The characteristics of the process steam, such as pressure and temperature, are often tailored to meet the requirements of the particular industrial application. Process steam is a crucial component in industries like chemical processing, food and beverage production, pharmaceuticals, paper and pulp manufacturing, and many others. The efficient generation and utilisation of process steam are key considerations for optimising industrial operations and ensuring the overall productivity of various manufacturing processes. Process steam may also be referred to as clean steam or non-contaminated steam. It will be understood by a person skilled in the art that process steam may still contain some minor pollutants or contaminants. In this regard, process steam need not be 100% clean steam which is entirely free of any pollutants or contaminants. Process steam typically has a higher temperature compared to the waste steam and is adjusted for the temperature required in the industrial process. Mechanical Vapor Recompression (MVR) is a known method to increase energy efficiency and to recycle heat in steam-based heat distribution systems in industrial processes such as manufacturing facilities. MVR works by taking waste steam and channeling it through an MVR device, which typically comprises a centrifugal compressor or a piston compressor that is designed for this purpose, and specifically for steam (i.e. not a refrigeration compressor). MVR increases the temperature and steam pressure as the steam passes through the MVR system. In principle, this is classified as an “open-loop heat pump” system, meaning that the process medium (the steam) also acts as the working medium / working fluid within the heat pump / MVR. This type of configuration theoretically has the highest possible efficiency (requires no heat exchangers or phase changes, it acts directly on the waste steam). Due to the fact that MVR operates directly on the waste steam, the MVR input steam is also the MVR output steam. The person skilled in the art will be aware that this means that a contaminated input steam stream results in a contaminated output steam stream. Contaminated steam in industrial processes can lead to various problems and issues. Contaminants in steam can negatively impact the equipment used in the process and the final product. Contaminants in steam, such as impurities or solid particles, can cause damage to components of the MVR compressor. These particles can erode or corrode components, reducing the efficiency and lifespan of the equipment. This may lead to increased energy consumption and decreased overall system performance. In industries where steam comes into direct contact with products (such as in food, chemicals and pharmaceutical manufacturing), contaminants in the steam can lead to product contamination. This can result in quality issues, compliance concerns, and even health and safety risks. Contaminated steam can also lead to safety hazards, particularly if the contaminants are corrosive or toxic. This poses risks to both equipment and personnel working in the industrial facility. Dealing with the consequences of contaminated steam, such as equipment damage to components of the MVR compressor and / or increase the maintenance levels required to an unreasonable level. Due to this, MVR may either not be used at all because the steam is too polluted or the process requires an unfeasible level of maintenance. Excessive maintenance has clear implications on cost-efficiency of operating the system and down-time. In many manufacturing plants, process steam is typically generated by a traditional boiler system, e.g. using natural gas or oil, and then the steam is distributed throughout the respective plant to various heat sinks / consumers. At the “end of the line”, the temperature of the remaining steam is so low, or even condensed, that the steam cannot be used any further, and this is where a heat pump can be used to recycle some of the waste heat. However, in some manufacturing plants, steam is only used indirectly, for example to evaporate moisture of various products, for example the moisture in foods. In some cases, the evaporated moisture then mixes with surrounding air, and the air is then saturated with water in either steam or aerosol form. In other cases, there is no air in the system, and the evaporated moisture could be seen as more or less pure steam, save for some contaminants in some cases. Usually, this steam comes at a low pressure, either as vacuum steam, or atmospheric in the case where it is mixed with air, and in principal it could also come out as above-atmospheric if the system is arranged to contain the pressure. In the described systems waste steam is generated indirectly, as a result of using the source steam (or other heat source) to remove vapor from a product or raw material. Some examples of industrial processes that could produce such waste steam are food production in general, pulp & paper, as well as animal fodder production, certain chemical processes, Carbon Capture and Storage, Direct Air Capture and more. In general, this applies to processes wherein evaporation columns are used. One of the main problems to be solved is to usefully extract heat from waste steam when the waste steam has a low exergy and may be polluted. A major barrier to the implementation of a system to usefully extract heat from waste steam is the slow development of heat pumps with the ability to receive a heat source of above 50 degrees Celsus. For example, there has been slow development of heat pumps with the ability to handle a heat source of between 50 degrees Celsius and 110 degrees Celsius, between 50 degrees Celsius and 120 degrees Celsius and between 50 degrees Celsius and 130 degrees Celsius. Water is used as a heat transfer fluid in district heating systems. District heating systems use a centralised energy distribution system that provides heating (and sometimes cooling) to multiple buildings or residential areas from a common heat source. Throughout the present disclosure the terms subcritical, trans-critical and supercritical are used with reference to vapour compression cycles in heat pump processes. Such terms are given their normal meaning in the art. For clarity, the terms are now very briefly explained. In subcritical heat pump processes, the refrigerant changes phase with the addition and extraction of heat. In a supercritical heat pump process, the refrigerant does not change phase with the addition and extraction of heat. In trans-critical heat pump processes, the refrigerant undergoes both subcritical and supercritical heat exchange processes, for example a subcritical evaporation process and a supercritical cooling process in what would otherwise be a condensation process in a subcritical vapor compression cycle. Patent document WO2016002878A1 discloses a heat-pump-type steamgenerating device for recovering heat from warm water and generating steam, wherein blowdown water separated by a gas-liquid separator and discharged in order to suppress an increase in the concentration of a scale-causing substance is merged with a warm-water feed channel, whereby heat energy held by the blowdown water is utilized as much as possible while scale buildup in a waste-heat recovery unit is prevented. Patent document WO 2015064347A1 discloses a vapor generation device and a vapor generation heat pump. A vapor generation device is configured such that the upper part of a gas-liquid separator and the upper part of an evaporator is connected by upper piping and the lower part of the gas-liquid separator and the lower part of the evaporator are connected by lower piping, to thereby form a thermo-siphon circuit. The thermo-siphon circuit supplies water within the gas-liquid separator to the evaporator through the lower piping, causes the water to be evaporated by the heat exchange between the water and a refrigerant flowing through the evaporator, supplies vapor generated by the evaporator to the gas-liquid separator through the upper piping, and delivers the vapor through the gas-liquid separator. The positional relationship between the evaporator and the gas-liquid separator is specified so that the position of the vapor 7 outlet of the evaporator is located below the surface of the water stored within the gasliquid separator. Patent document CN 102889573A discloses a process system for preparing deoxygenated water for a boiler by utilizing a high temperature heat pump system. The process system is formed by connecting three loops, i.e. a circulating water loop for a cooling chemical process or equipment, a high temperature heat pump mixed working medium circulating loop and a deoxygenated water loop, by pipelines. According to the invention, because the high temperature heat pump system is adopted and a high temperature mixed working medium is utilized, low temperature heat can be risen to about 100 DEG C; and the energy efficiency ratio of the heat pump system for recovering the waste heat can reach over 3.5. After being recovered by a high temperature heat pump, the industrial waste heat reaches a temperature (20 to 30 DEG C) required by the process and returns to the process system to be recycled, and therefore the heat pollution to the environment is reduced. When the condensation heat of circulating water is recovered by the heat pump system, high temperature hot water (the deoxygenated water) is prepared, so that water vapor utilized to prepare the deoxygenated water by a manufacturer is saved, the production cost of the manufacturer is reduced, and therefore the process system has double functions. Patent document CN 115289443A discloses an energy recycling process for wastewater in a printing and dyeing process, and belongs to the technical field of water, wastewater and sewage treatment by utilizing waste heat in other processes. Waste water in the printing and dyeing process is treated through a heat pump unit, the heat pump unit comprises a working medium tank, an evaporator, a compressor, a condenser and a transfer box, and heat released by a working medium at the condenser serves as a heat source to be recycled to the corresponding heating procedure of the printing and dyeing procedure. The method is applied to the field of printing and dyeing, and has the 8 advantages of power saving, energy saving, environmental protection, economy and the like. Patent document JP 2011245413A discloses a water treatment system including: a plurality of apparatuses; a plurality of piping zones connecting the plurality of apparatuses adjacent to each other; and a heat pump which absorbs heat from at least one piping zone as an endothermic piping zone and exhausts the heat absorbed from the piping zone to at least one other piping zone as an exhaust heat piping zone Patent document CN 107166479A discloses a system for recycling waste heat of a nuclear power plant. The system comprises a nuclear power plant steam condenser and further comprises a heat pump system and a heat use system. The cooling water output end of the steam condenser is connected with the input end of the evaporation side of the heat pump system, and the cooling water input end of the steam condenser is connected with the output end of the evaporation side of the heat pump system. The hot water supply input end of the heat use system is connected with the output end of the condensation side of the heat pump system, and the hot water supply output end of the heat use system is connected with the input end of the condensation side of the heat pump system. The heat pump system is directly connected with a cooling water way of the steam condenser, closed circulation of cooling water is achieved, on one hand, recycling of the heat is achieved, and on the other hand, output of the heat is reduced, and heat pollution to the environment is avoided. The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to the prior art. The object is achieved through features, which are specified in the description below and in the claims that follow. SUMMARY According to the first aspect of the invention, there is provided a heat pump for receiving a waste steam stream and producing a process steam stream in use, the heat pump comprising, arranged in series in a closed loop: a waste steam condenser fluidly connected to; a compressor fluidly connected to; a process steam generator fluidly connected to; an expansion valve fluidly connected to the waste steam condenser; such that in use a refrigerant can circulate around the closed loop; wherein the compressor is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use; the expansion valve is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use; the waste steam condenser is configured to receive a waste steam stream and transfer heat from the waste steam stream to the refrigerant in use; and the process steam generator is configured to receive water and transfer heat from the refrigerant to the water to produce a process steam stream in use. The waste steam condenser, the compressor, the process steam generator and the expansion valve may be arranged and / or configured to perform a vapour compression cycle. In some examples, the waste steam condenser, the compressor, the process steam generator and the expansion valve may be arranged and / or configured to perform a subcritical vapour compression cycle. The waste steam condenser may be configured to evaporate the refrigerant. The waste steam condenser may be configured to receive the waste steam stream and transfer heat from the waste steam stream to the refrigerant in use, thereby evaporating the refrigerant. The process steam generator may be configured to condense the refrigerant. The process steam generator may be configured to condense the refrigerant and transfer heat from the refrigerant to the water to produce the process steam stream. Advantageously, a subcritical vapour compression cycle may consume waste steam and produce process steam more efficiently than trans-critical or supercritical vapour compression cycles. In some examples, the heat pump may be arranged and / or configured to provide a trans-critical vapour compression cycle. The heat pump may be arranged and / or configured to provide a supercritical vapour compression cycle. Advantageously, the heat pump may provide the advantage of making a useful compromise between the MVR process and intermediate-loop-based systems. In intermediate loop based systems the heat is recovered from a low temperature water loop (typically a cooling tower loop with temperatures between 20-35 degrees Celsius). Intermediate-loop-based-systems ensures also separation of working medium and process medium, however due to the lower heat source temperature, the efficiency (coefficient of performance) is lower. In MVR has the highest efficiency but cannot be operated under all boundary condition or only with increased maintenance efforts. Advantageously, the heat source and heat sink remain separated. Advantageously, massflow and energy balances could be different. Advantageously, different qualities of steam flows (i.e. waste steam and process steam) are not mixed. Advantageously, although MVR is more compact than a comparable closed loop heat pump, because no heat exchanger piping etc. is needed, the compressor itself is, especially in vacuum applications, much bigger than the heat exchangers required in the described closed loop heat pump. Therefore, integration in existing plants using the presently described system may be easier than integrating an MVR system. In MVR systems the steam compressions always create superheated steam. If the application requires saturated steam then water has to be injected which increases the complexity of the system. However, advantageously, in the system described herein the closed loop heat pump generated saturated or superheated steam without additional water injection. The described closed-loop heat pump may be particularly advantageous in vacuum steam applications. Low pressure conditions require very high compression ratios. Pressure ratio with a closed loop heat pump can be selected due the choice of the working fluid. Low pressure conditions mean also high specific volumes which may result in very high-volume flows for the MVR. MVR is always a compromise between power output and temperature lift. Typical temperature lifts per stage are limited to 7-10 K in vacuum steam applications. Closed loop heat pumps require only a large heat exchanger on the heat source side and the massflow is not dependent on the pressure of the process medium. Temperature lifts of up 70 K per stage are possible in some examples. Since MVR uses the process medium as working medium, the MVR compressor has to deal with residuals directly which is challenging or even impossible depending on the contamination. The compressor of close loop heat pumps is always shielded towards the process steam. The compressor only comes into contact with the internal working fluid. Most prior art MVR compressors use oil as the lubricant. It can be very challenging to ensure no contamination at all of the process steam, (e.g. for clean steam applications in the pharma industry, food or chemical industries). The heat pump may be a high-temperature heat pump. The heat pump may comprise a receiver or receivers. The heat pump may comprise instrumentation. The heat pump may comprise an oil-separator or oil-separators. The heat pump may comprise a valve or valves. The heat pump may comprise a buffer tank or buffer tanks. The heat pump may comprise an internal heat exchanger or internal heat exchangers. The heat pump may further comprise a pressurisation device configured to pressurise water provided to the process steam generator such that the water provided to the process steam generator is maintained in the liquid phase until the water reaches the process steam generator in use. According to a second aspect of the invention, there is provided a heat pump system for receiving a waste steam stream and producing a process steam stream in use, the heat pump system comprising: a heat pump according to the first aspect of the invention; a refrigerant provided in the closed-loop; a waste steam stream provided to the waste steam condenser; and a water stream provided to the process steam generator. According to a third aspect of the invention, there is provided a heat pump for receiving a waste steam stream and heating a process liquid stream in use, the heat pump comprising, arranged in series in a closed loop: a waste steam condenser fluidly connected to; a compressor fluidly connected to; a process liquid heat exchanger fluidly connected to; an expansion valve fluidly connected to the waste steam condenser; such that in use a refrigerant can circulate around the closed loop; wherein the compressor is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use; the expansion valve is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use; the waste steam condenser is configured to receive a waste steam stream and transfer heat from the waste steam stream to the refrigerant in use; and the process liquid heat exchanger is 13 configured to heat a process liquid stream by transferring heat from the refrigerant to the process liquid stream in use. The process liquid heat exchanger may be configured to heat a process liquid stream comprising water. The process liquid heat exchanger may be configured to heat a process liquid stream comprising thermal oil or condensate from an industrial process. The heat pump may be a high-temperature heat pump. The heat pump may comprise a receiver or receivers. The heat pump may comprise instrumentation. The heat pump may comprise an oil-separator or oil-separators. The heat pump may comprise a valve or valves. The heat pump may comprise a buffer tank or buffer tanks. The heat pump may comprise an internal heat exchanger or internal heat exchangers. The heat pump may further comprise a pressurisation device configured to pressurise the process liquid stream to keep the process liquid stream in the liquid phase in use. Advantageously, the waste steam condenser, the compressor, the process liquid heat exchanger and the expansion valve may be arranged and / or configured to perform a vapour compression cycle. In some examples, the waste steam condenser, the compressor, the process liquid heat exchanger and the expansion valve may be arranged and / or configured to perform a subcritical vapour compression cycle. The waste steam condenser may be configured to evaporate the 14 refrigerant. The waste steam condenser may be configured to receive the waste steam stream and transfer heat from the waste steam stream to the refrigerant in use, thereby evaporating the refrigerant. The process liquid heat exchanger may be configured to condense the refrigerant. The process liquid heat exchanger may be configured to condense the refrigerant and transfer heat from the refrigerant to the process liquid stream to heat the process liquid stream. Advantageously, a subcritical vapour compression cycle may consume waste steam and heat a process liquid stream more efficiently than trans-critical or supercritical vapour compression cycles. The heat pump may be arranged and / or configured to provide a trans-critical vapour compression cycle. The heat pump may be arranged and / or configured to provide a supercritical vapour compression cycle. According to a fourth aspect of the invention, there is provided a heat pump system for receiving a waste steam stream and heating a process liquid stream in use, the heat pump system comprising: a heat pump according to the third aspect of the invention; a refrigerant provided in the closed-loop; a waste steam stream provided to the waste steam condenser; and a process liquid stream provided to the process liquid heat exchanger. According to a fifth aspect of the invention, there is provided a method of operating a steam-steam heat pump, the method comprising the steps of: providing a heat pump system according to the second aspect of the invention; and operating the heat pump to produce a process steam stream. The step of operating the heat pump may comprise circulating a refrigerant around the closed loop. The step of operating the heat pump may further comprise: transferring heat from the waste steam stream to the refrigerant using the waste steam condenser; increasing the pressure of the refrigerant using the compressor, thereby increasing the temperature of the refrigerant; and transferring heat from the refrigerant to the water to produce process steam. The step of transferring heat from the waste steam stream to the refrigerant using the waste steam condenser may comprise evaporating the refrigerant. The step of transferring heat from the refrigerant to the water to produce process steam may comprise condensing the refrigerant. The step of operating the heat pump may further comprise decreasing the pressure of the refrigerant to decrease the temperature of the refrigerant. According to a sixth aspect of the invention, there is provided a method of operating a steam-liquid heat pump, the method comprising the steps of: providing a heat pump system according to the fourth aspect of the invention; and operating the heat pump to heat the process liquid stream. The step of operating the heat pump may comprise circulating a refrigerant around the closed loop. The step of operating the heat pump may further comprise: transferring heat from the waste steam stream to the refrigerant using the waste steam condenser; increasing the pressure of the refrigerant using the compressor, thereby increasing the temperature of the refrigerant; and transferring heat from the refrigerant to the process liquid stream. Transferring heat from the waste steam stream to the refrigerant using the waste steam condenser may comprise evaporating the refrigerant. Transferring heat from the refrigerant to the process liquid stream may comprise condensing the refrigerant. The step of operating the heat pump may further comprise decreasing the pressure of the refrigerant to decrease the temperature of the refrigerant. The step of operating the heat pump may further comprise pressurising the process liquid stream to keep the process liquid stream in the liquid phase. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a prior art Mechanical Vapour Recompression system; Figure 2 shows an example of a closed-loop steam-steam heat pump in accordance with the first aspect of the invention; and Figure 3 shows an example of a closed-loop steam-liquid heat pump in accordance with the second aspect of the invention. For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted. DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 shows a prior art Mechanical Vapour Recompression (MVR) system 100. The MVR system comprises an open loop heat pump 110 in the form of a compressor configured to receive waste steam at a heat sink in 120 and deliver superheated steam at a heat sink out 130. Figure 2 shows a heat pump 200 for receiving a waste steam stream 201 and producing a process steam stream 202 in use, as will now be explained. The heat pump 200 comprises a closed loop 203. Within the closed loop 203 there is, arranged in series, a waste steam condenser 204 fluidly connected to a 17 compressor 205 fluidly connected to a process steam generator 206 fluidly connected to an expansion valve 207 fluidly connected to the waste steam condenser 204. In use a refrigerant (not shown) can circulate around the closed loop 203. In the closed loop 203, the waste steam condenser 204, compressor 205, process steam generator 206 and expansion valve 207 are configured to perform a vapour compression cycle. The compressor 205 is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use. The expansion valve 207 is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use. The waste steam condenser 204 is configured to receive the waste steam stream 201 and transfer heat from the waste steam stream 201 to the refrigerant in use. The process steam generator 206 is configured to receive water 208 and transfer heat from the refrigerant to the water 208 to produce the process steam stream 202 in use. The presently described arrangement allows for the provision of an isenthalpic process in use, i.e. a process in which enthalpy of the system remains constant. For this reason, the expansion valve 207 is provided to allow a pressure drop with virtually constant enthalpy. The skilled person will be aware of the distinction between the presently described expansion valve 207 and another apparatus which does not maintain constant enthalpy, for example an expander in the form of a turbine expander. Still referring to Figure 2, the waste steam stream 201 is delivered to the waste steam condenser 204 by a first pump 209. It will be understood by a person skilled in the art that the first pump 209 shown is not essential and that the waste steam stream 201 can be delivered to the waste steam condenser 204 in myriad different ways, such as but not limited to, providing a suction fan to suck the waste steam stream 201 to the waste steam condenser 204. After the waste steam stream 201 is passed through the waste steam condenser 204, a stream of waste condensate 210 is delivered from the waste steam condenser 204. The water 208 is delivered to the process steam generator 206 by a second pump 211. It will be understood by a person skilled in the art that the second pump 211 shown is not essential and that the water 208 can be delivered to the process steam generator 206 in myriad different ways. The heat pump 200 may in some examples be a high-temperature heat pump. The heat pump 200 acts simultaneously as a steam condenser on one end (i.e. on the waste steam side) and a steam generator on another end (i.e. on the process steam side), thereby eliminating the need for an intermediate heat exchange processes other than between the heat pump’s 200 internal process and the external steam source / sink. The heat pump 200 may comprise further components not described herein in the interest of brevity and clarity. Non-limiting examples of such further components are for example: receiver(s) and / or instrumentation and / or oil-separator(s) and / or valve(s) and / or buffer tank(s) and / or internal heat exchanger(s), such as but not limited to, recuperator(s). In some examples, the heat pump 200 may further comprise a pressurisation device (not shown) configured to pressurise the water provided to the process steam generator such that the water provided to the process steam generator is maintained in the liquid phase until the water reaches the process steam generator in use. Figure 3 shows a heat pump 200’ for receiving a waste steam stream 201’ and heating a process liquid stream 208’ in use, as will now be explained. The process liquid stream 208’ in the presently described example is water. In some examples, the process liquid stream 208’ is thermal oil. In some examples, the process liquid stream 208’ is condensate from the industrial process in which the heat pump 200’ is installed. Similarly to the heat pump 200 described with reference to Figure 2, the heat pump 200’ comprises a closed loop 203’. Within the closed loop 203’ there is, arranged in series, a waste steam condenser 204’ fluidly connected to a compressor 205’ fluidly connected to a process liquid heat exchanger 206’ fluidly connected to an expansion valve 207’ fluidly connected to the waste steam condenser 204’. In use a refrigerant (not shown) can circulate around the closed loop 203’. The compressor 205’ is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use. The expansion valve 207’ is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use. The waste steam condenser 204’ is configured to receive the waste steam stream 201’ and transfer heat from the waste steam stream 201’ to the refrigerant in use. The process liquid heat exchanger 206’ is configured to receive the process liquid stream 208’, which is water in the presently described example, and transfer heat from the refrigerant to the process liquid stream 208’ to produce a heated process liquid stream 202’ in use. Still referring to Figure 3, the waste steam stream 201’ is delivered to the waste steam condenser 204’ by a first pump 209’. It will be understood by a person skilled in the art that the first pump 209’ shown is not essential and that the waste steam stream 201’ can be delivered to the waste steam condenser 204’ in myriad different ways, such as but not limited to, providing a suction fan to suck the waste steam stream 201’ to the waste steam condenser 204’. After the waste steam stream 201’ is passed through the waste steam condenser 204’, a stream of waste condensate 210’ is delivered from the waste steam condenser 204’. The process liquid stream 208’, i.e. water in the presently described example, is delivered to the process liquid heat exchanger 206’ by a second pump 21T. It will be understood by a person skilled in the art that the second pump 211’ shown is not essential and that the process liquid 208’ can be delivered to the process liquid heat exchanger 206’ in myriad different ways. The heat pump 200’ may in some examples be a high-temperature heat pump. The heat pump 200’ acts simultaneously as a steam condenser on one end (i.e. on the waste steam side) and a process liquid heater on another end (i.e. on the process liquid side), thereby eliminating the need for an intermediate heat exchange processes other than between the heat pump’s 200’ internal process and the external steam source I liquid sink. The heat pump 200’ may comprise further components not described herein in the interest of brevity and clarity. Non-limiting examples of such further components are for example: receiver(s) and / or instrumentation and / or oil-separator(s) and / or valve(s) and / or buffer tank(s) and / or internal heat exchanger(s), such as but not limited to, recuperator(s). In the presently described example, the process liquid stream 208’ is water, therefore the heated process liquid stream 202’ is heated water. The term “heated water” is intended to mean water at a temperature higher than the temperature of the water delivered to the process liquid heat exchanger 206’. It will be understood that in an alternative example where the process liquid stream 208’ is thermal oil then the heated process liquid stream 202’ is heated thermal oil. The term “heated thermal oil” is intended to mean thermal oil at a temperature higher than the temperature of the thermal oil delivered to the process liquid heat exchanger 206’. It will be understood that in an alternative example where the process liquid stream 208’ is condensate from the industrial process then the heated process liquid stream 202’ is heated condensate. The term “heated condensate” is intended to 21 mean condensate at a temperature higher than the temperature of the condensate delivered to the process liquid heat exchanger 206’. In some examples, the heat pump 200’ may further comprise a pressurisation device (not shown) configured to pressurise the process liquid stream 202’ and / or the heated process liquid stream 208’ such that the process liquid stream and / or the heated process liquid stream 208’ is / are maintained in the liquid phase in use. In the above-described heat pumps 200, 200’ shown in Figures 2 and 3, the closed loops 203, 203’ may be arranged and / or configured to provide a subcritical vapour compression cycle or a trans-critical vapour compression cycle or a supercritical vapour compression cycle. In examples wherein the above-described heat pumps 200, 200’ are arranged and / or configured to provide a subcritical vapour compression cycle, the waste steam condensers 204, 204’ evaporate the refrigerant. That is to say, when employing a subcritical vapour compression cycle, the waste steam condensers 204, 204’ receive the waste steam stream 201,201’ and transfer heat from the waste steam stream 201, 201’ to the refrigerant in use, thereby evaporating the refrigerant. Furthermore, in such examples wherein the above-described heat pumps 200, 200’ are arranged and / or configured to provide a subcritical vapour compression cycle, the process steam generator 206 in Figure 2 and process liquid heat exchanger 206’ in Figure 3 condense the refrigerant. That is to say, when employing a subcritical vapour compression cycle, the process steam generator 206 in Figure 2 and process liquid heat exchanger 206’ in Figure 3 condense the refrigerant thereby transferring heat from the refrigerant to the water 208 in Figure 2 to produce the process steam stream 202 and to the process liquid stream 208’ in Figure 3 to produce the heated process liquid stream 202’. As will be appreciated by a person skilled in the art, the terms refrigerant and working fluid may be used interchangeably when referring to the closed loop heat pump cycle. In any of the above-mentioned examples, the refrigerant may be a synthetic refrigerant. Non-limiting examples of suitable synthetic refrigerants include hydrofluoroolefins (HFOs) such as R1234ze(E), R1234ze(Z), R1336mzz(Z) and R1336mzz(E), and hydrochlorofluoroolefins (HCFOs) such as R1233zd(E) and R1224yd(Z). Further non-limiting examples of suitable synthetic refrigerants include hydrofluorocarbons (HFCs), for example R245fa and R134a. Blends of any of the above-mentioned refrigerants may also produce suitable refrigerants, such as, as a non-limiting example R515B, which consists of an HFO in combination with an HFC. In any of the above-mentioned examples, the refrigerant may be a natural refrigerant. Non-limiting examples of natural refrigerants include hydrocarbons (HCs) such as propane, propene, butane, isobutane, n-pentane, isopentane, neopentane, n-hexane and cyclopentane. Blends of various hydrocarbons could be used as a suitable refrigerant in any of the above-mentioned examples. Blends of different classes of refrigerants could be used to produce a suitable refrigerant for use in any of the above-mentioned examples. Further non-limiting examples of natural refrigerants include water, ammonia, carbon dioxide and various ethers, as well as different blends of any of the abovementioned fluids.

Claims

1. A heat pump (200) for receiving a waste steam stream (201) and producing a process steam stream (202) in use, the heat pump (200) comprising, arranged in series in a closed loop (203):a waste steam condenser (204) fluidly connected to;a compressor (205) fluidly connected to;a process steam generator (206) fluidly connected to;an expansion valve (207) fluidly connected to the waste steam condenser (204);such that in use a refrigerant can circulate around the closed loop (203);wherein the compressor (205) is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use;the expansion valve (207) is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use;the waste steam condenser (204) is configured to receive a waste steam stream (201) and transfer heat from the waste steam stream (201) to the refrigerant in use; andthe process steam generator (206) is configured to receive water (208) and transfer heat from the refrigerant to the water (208) to produce a process steam stream (202) in use.

2. The heat pump (200) according to claim 1, wherein the heat pump (200) is a high-temperature heat pump.

3. The heat pump (200) according to claim 1 or 2, wherein the heat pump (200) further comprises one or more of the following: one or more receiver(s); instrumentation; oil-separator(s); valve(s); buffer tank(s); internal heat exchanger(s); recuperator(s).

4. The heat pump (200) according to any preceding claim, further comprising a pressurisation device (211) configured to pressurise water (208) provided to the process steam generator (206) such that the water (208) provided to the process steam generator (206) is maintained in the liquid phase until the water (208) reaches the process steam generator (206) in use.

5. A heat pump system for receiving a waste steam stream (201) and producing a process steam stream (202) in use, the heat pump system comprising:a heat pump (200) according to any of claims 1 to 4;a refrigerant provided in the closed loop (203);a waste steam stream (201) provided to the waste steam condenser (204); anda water stream (208) provided to the process steam generator (206).

6. A heat pump (200’) for receiving a waste steam stream (20T) and heating a process liquid stream (208’) in use, the heat pump (200’) comprising, arranged in series in a closed loop (203’):a waste steam condenser (204’) fluidly connected to;a compressor (205’) fluidly connected to;a process liquid heat exchanger (206’) fluidly connected to;an expansion valve (207’) fluidly connected to the waste steam condenser (204’);such that in use a refrigerant can circulate around the closed loop (203’);wherein the compressor (205’) is configured to increase the pressure of the refrigerant to increase the temperature of the refrigerant in use;the expansion valve (207’) is configured to decrease the pressure of the refrigerant to decrease the temperature of the refrigerant in use;the waste steam condenser (204’) is configured to receive a waste steam stream (20T) and transfer heat from the waste steam stream (201’) to the refrigerant in use; andthe process liquid heat exchanger (206’) is configured to heat a process liquid stream (208’) by transferring heat from the refrigerant to the process liquid stream (208’) in use.

7. The heat pump (200’) according to claim 6, wherein the process liquid heat exchanger (206’) is configured to heat a process liquid stream (208’) comprising water.

8. The heat pump (200’) according to claim 6, wherein the process liquid heat exchanger (206’) is configured to heat a process liquid stream (208’) comprising thermal oil or condensate from an industrial process.

9. The heat pump (200’) according to any of claims 6 to 8, wherein the heat pump (200’) is a high-temperature heat pump.

10. The heat pump (200’) according to any of claims 6 to 9, wherein the heat pump (200’) further comprises one or more of the following: one or more receiver(s); instrumentation; oil-separator(s); valve(s); buffer tank(s); internal heat exchanger(s); recuperator(s).11 .The heat pump (200’) according to any of claims 6 to 10, further comprising a pressurisation device (21T) configured to pressurise the process liquid stream (208’) to keep the process liquid stream (208’) in the liquid phase in use.

12. A heat pump system for receiving a waste steam stream (20T) and heating a process liquid stream (208’) in use, the heat pump system comprising:a heat pump (200’) according to any of claims 6 to 11;a refrigerant provided in the closed-loop (203’);a waste steam stream (20T) provided to the waste steam condenser (204’) ; anda process liquid stream (208’) provided to the process liquid heat exchanger (206’).

13. A method of operating a steam-steam heat pump (200), the method comprising the steps of:a. providing a heat pump system according to claim 5; andb. operating the heat pump (200) to produce a process steam stream (202).

14. The method according to claim 13, wherein the step of operating the heat pump (200) comprises circulating a refrigerant around the closed loop (203).

15. The method according to claim 14, wherein the step of operating the heat pump (200) further comprises:transferring heat from the waste steam stream (201) to the refrigerant using the waste steam condenser (204);increasing the pressure of the refrigerant using the compressor (205), thereby increasing the temperature of the refrigerant; andtransferring heat from the refrigerant to the water to produce process steam (202).

16. The method of claim 15, wherein the step of operating the heat pump (200) further comprises decreasing the pressure of the refrigerant to decrease the temperature of the refrigerant.

17. A method of operating a steam-liquid heat pump (200’), the method comprising the steps of:a. providing a heat pump system according to claim 12; andb. operating the heat pump (200’) to heat the process liquid stream (208’).

18. The method according to claim 17, wherein the step of operating the heat pump (200’) comprises circulating a refrigerant around the closed loop (203’).

19. The method according to claim 18, wherein the step of operating the heat pump (200’) further comprises:transferring heat from the waste steam stream (20T) to the refrigerant using the waste steam condenser (204’);increasing the pressure of the refrigerant using the compressor (205’), thereby increasing the temperature of the refrigerant; and transferring heat from the refrigerant to the process liquid stream (208’).5       20. The method of claim 19, wherein the step of operating the heat pump (200’)further comprises decreasing the pressure of the refrigerant to decrease the temperature of the refrigerant.

21. The method of claim 20, wherein the step of operating the heat pump (200’)10          further comprises pressurising the process liquid stream (208’) to keep theprocess liquid stream (208’) in the liquid phase.

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