Self-cascade high temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology

Abstract

The present invention discloses a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology, comprising a separator, a cascade heat exchanger, an economizer, a mixer, an evaporator, a first throttle valve, a second throttle valve, a third throttle valve, a first condenser, a second condenser, a third condenser, a fourth condenser, a first compressor, a second compressor, and a third compressor; the saturated liquid at the outlet of the separator of the present invention is throttled to an intermediate pressure and compressed to a condensation pressure by a first compressor, thereby avoiding unnecessary throttling losses, reducing the power consumption of the compressor, and improving system performance; and through two incomplete condensation processes in the second condenser and the fourth condenser, not only can two steams with different temperature levels be produced, but also can match the temperature difference of the steam, thereby reducing irreversible losses.

Description

Technical Field

[0001] The invention belongs to the field of high-temperature heat pumps, and in particular relates to a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology. Background Art

[0002] In high-energy-consuming industrial fields such as papermaking, cement and chemical industry, a large amount of industrial waste heat is generated during the production process, and there is a large demand for high-temperature steam. As an efficient and energy-saving device that makes full use of low-grade thermal energy, heat pumps can be used to recover industrial waste heat and use it to produce steam to increase the economic benefits of enterprises and reduce carbon emissions.

[0003] At present, the high-temperature heat pump technologies that achieve large temperature spans mainly include cascade cycles and self-cascade cycles. The cascade cycle couples two or more heat pump cycles (using different working fluids) together, which can reduce the compression ratio of each cycle to improve the overall temperature increase effect. However, the cascade heat pump contains more components and has the disadvantages of complex structure, high cost and complex control strategy. Compared with the cascade cycle, the self-cascade cycle is less complex and less expensive, because the self-cascade cycle can utilize the temperature glide and component separation characteristics of non-azeotropic mixed working fluids to achieve a larger temperature rise when using a single compressor. However, the traditional self-cascade cycle has large throttling losses, high pressure ratios, and low compressor efficiency. In addition, although the self-cascade cycle can match the temperature glide characteristics of non-azeotropic mixed working fluids well on the heat source side (industrial wastewater, explicit heat release, large temperature difference), it has poor temperature matching with steam on the heat sink side (steam, phase change evaporation, small temperature change), and the irreversible loss increases. Summary of the invention

[0004] The purpose of the present invention is to provide a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned object, the present invention provides a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology, comprising a separator, a cascade heat exchanger, an economizer, a mixer, an evaporator, a first throttle valve, a second throttle valve, a third throttle valve, a first condenser, a second condenser, a third condenser, a fourth condenser, a first compressor, a second compressor, and a third compressor;

[0006] The first throttle valve, the cascade heat exchanger, the first compressor, the second condenser, and the mixer are connected in sequence;

[0007] The cascade heat exchanger, the economizer, the third throttle valve, the evaporator, the second compressor, the third compressor, the first condenser, the third condenser, and the mixer are connected in sequence; the second throttle valve is connected to the economizer;

[0008] The mixer, the fourth condenser, and the separator are connected in sequence.

[0009] Optionally, the self-cascade high-temperature heat pump circulation system uses a mixed working fluid composed of two working fluids with different boiling points, and the separator is used to separate the mixed working fluid into saturated gas and saturated liquid, the saturated gas and the saturated liquid both include low-boiling point working fluid and high-boiling point working fluid, and the concentration of the low-boiling point working fluid in the saturated gas is higher than that of the high-boiling point working fluid, and the concentration of the high-boiling point working fluid in the saturated liquid is higher than that of the low-boiling point working fluid.

[0010] Optionally, the saturated gas directly enters the cascade heat exchanger, and the saturated liquid enters the cascade heat exchanger after being throttled by the first throttle valve, evaporates to form superheated steam after heat exchange with the saturated gas, and the saturated gas condenses to form saturated subcooled liquid.

[0011] Optionally, the superheated steam is compressed by the first compressor into high-temperature and high-pressure steam, and the high-temperature and high-pressure steam is condensed and releases heat in the second condenser to form a two-phase working medium.

[0012] Optionally, the saturated subcooled liquid is divided into a first saturated subcooled liquid and a second saturated subcooled liquid. The first saturated subcooled liquid is throttled by the second throttle valve and enters the economizer to evaporate and absorb heat to form steam; the second saturated subcooled liquid releases heat after entering the economizer to form a subcooled liquid.

[0013] Optionally, the subcooled liquid is throttled and reduced in pressure by the third throttle valve and then enters the evaporator to evaporate and absorb heat to form a superheated steam working medium. After the superheated steam working medium enters the second compressor for compression, it is mixed with the steam formed by the first saturated subcooled liquid and then compressed by the third compressor to form high-temperature and high-pressure steam.

[0014] Optionally, after the high-temperature and high-pressure steam passes through the first condenser and the third condenser in sequence, it merges with the superheated steam formed by the saturated liquid in the cascade heat exchanger and continues to release heat.

[0015] Optionally, the second condenser and the fourth condenser are used to form low-boiling-point working fluids of different concentrations, the low-boiling-point working fluids in the second condenser and the fourth condenser are not completely condensed, and the concentration of the low-boiling-point working fluid formed in the second condenser is lower than that of the low-boiling-point working fluid in the fourth condenser.

[0016] The technical effects of the present invention are:

[0017] (1) In the traditional self-cascade cycle, the saturated liquid at the separator outlet is throttled to the same pressure as that at the evaporator, resulting in large throttling irreversible losses. In fact, it only needs to be throttled to the intermediate pressure (P 12 >P 10 ) can meet the requirements. In this invention, the saturated liquid at the separator outlet is throttled to the intermediate pressure and compressed to the condensing pressure by the first compressor. Since unnecessary throttling losses are avoided, the power consumption of the compressor is reduced and the system performance is improved.

[0018] (2) To achieve a large temperature rise, it is necessary to increase the compression ratio of the compressor, which reduces the efficiency of the compressor. The present invention adopts the technology of jet enthalpy increase. On the one hand, it can supercool the working fluid in the main circuit before throttling, increase the enthalpy difference, and increase the heat absorption of the evaporator; on the other hand, it can make the compressor compress in two stages, and add air in the middle to reduce the superheat of the steam and improve the efficiency of the compressor.

[0019] (3) The self-cascade system uses a non-azeotropic mixed working fluid with a large temperature glide to achieve good temperature matching on the heat source side and improve the utilization rate of the heat source. However, on the heat sink side, in order to produce steam, a large temperature glide will inevitably cause a large temperature difference irreversible loss. The present invention can produce two steams with different temperature levels through two incomplete condensation processes (the second condenser and the fourth condenser), and can also match the temperature difference of the steam to reduce irreversible losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 Schematic diagram of a self-cascade high-temperature heat pump circulation system in an embodiment of the present invention;

[0022] Figure 2 It is a schematic diagram of an alternative scheme of the self-cascade high-temperature heat pump circulation system in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0025] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0026] Embodiment 1

[0027] like Figure 1-2 As shown, in this embodiment, a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology is provided, comprising:

[0028] The present invention is improved on the basis of the traditional self-cascade cycle, and its cycle process is as follows: Figure 1 The heat source side (C1-C2) is industrial wastewater or other waste heat, usually at a temperature of 60-70°C. Since there is no heat extraction restriction, the lower the temperature of the wastewater outlet, the better, in order to improve the utilization rate of the heat source.

[0029] The self-cascade cycle uses a mixed working fluid composed of two working fluids with different boiling points (such as low boiling point working fluid R1234yf / high boiling point working fluid R601).

[0030] The working fluid of basic concentration (point 1) is separated into saturated gas (point 2) and saturated liquid (point 3) in the gas-liquid separator. The concentration of low-boiling-point working fluid is high in saturated gas, while the concentration of high-boiling-point working fluid is high in saturated liquid. The high-temperature and high-pressure saturated liquid (point 3) enters the cascade heat exchanger after being throttled in the throttle valve 1, where it exchanges heat with the saturated gas and evaporates to become superheated vapor (point 13). At the same time, the saturated gas condenses into saturated or subcooled liquid (point 4). The superheated vapor at point 13 is compressed by compressor 1 into high-temperature and high-pressure vapor (point 14). The high-temperature and high-pressure vapor condenses and releases heat in condenser 2 to become a two-phase working fluid (incomplete condensation), which is used to heat saturated water to produce steam 1. The liquid at point 4 is divided into two streams, one of which enters the economizer after throttling to evaporate and absorb heat to become vapor (point 7), and the other enters the economizer to release heat to become a subcooled liquid (point 9). The supercooled liquid at 9 o'clock enters the throttle valve 3 to throttle and reduce the pressure. The working fluid after reducing the pressure (10 o'clock) enters the evaporator to absorb heat and absorb heat from the industrial wastewater. The working fluid (11 o'clock) that absorbs heat and becomes superheated steam enters the compressor and is compressed to the intermediate pressure (16 o'clock). After mixing with the steam from 7 o'clock, it is further compressed into high-temperature and high-pressure steam (18 o'clock). The steam at 18 o'clock passes through condenser 1 and condenser 3 in turn to preheat the water (heat the room temperature water to the saturated state). The steam at 15 o'clock and 20 o'clock continue to release heat after merging, and enter condenser 4 to produce steam 2.

[0031] The heat pump produces two streams of steam, namely steam 1 and steam 2, with steam 1 having a higher temperature. Steam 1 is first preheated in condenser 1 (H1-H2), and then evaporates and absorbs heat in condenser 2 (H2-H3); steam 2 is preheated in condenser 3 (H4-H5), and evaporates and absorbs heat in condenser 4 (H5-H6). Since the concentration of the low-boiling-point working fluid in condenser 2 is lower than that in condenser 1, it has a higher temperature at the same condensation pressure, so condenser 2 can produce steam with a higher temperature. The working fluid in condenser 2 and condenser 4 is an incomplete condensation process (the dryness at points 15 and 1 is 0.4-0.6), so the temperature change is small, which can match the evaporation phase change process on the heat sink side and reduce irreversible losses.

[0032] The jet enthalpy increase technology used in the present invention can be replaced by using a separator in addition to the economizer. The principle is as follows: Figure 2 As shown. After the liquid at point 4 is throttled to the intermediate pressure by the throttle valve, it enters the separator for gas-liquid separation, and is separated into saturated gas (point 7) and saturated liquid (point 9). The saturated gas merges with the steam at the outlet of compressor 2, and enters the next stage of compression after reducing its superheat. After the saturated liquid is throttled by the throttle valve 3, it enters the evaporator.

[0033] Compared with the structure using the economizer, after using separator 2, the concentration of the low-boiling-point working fluid at 9 o'clock is lower. At the same evaporation temperature, the pressure is lower, which reduces the pressure at the inlet of compressor 2, increases the pressure ratio, and increases the power consumption of compressors 2 and 3, thereby reducing the performance of the heat pump.

[0034] Although it can be replaced by a separator structure, analysis shows that the performance is reduced, so this embodiment is more inclined to use an economizer structure.

[0035] The present invention proposes a self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase technology, which can recover industrial waste heat for steam production. Compared with the traditional self-cascade cycle, the performance coefficient of the system is improved, and the heat exchange matching between the non-azeotropic mixed working fluid and steam is improved.

[0036] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase process, characterized in that: It includes a separator, a cascade heat exchanger, an economizer, a mixer, an evaporator, a first throttle valve, a second throttle valve, a third throttle valve, a first condenser, a second condenser, a third condenser, a fourth condenser, a first compressor, a second compressor, and a third compressor; The first throttle valve, the cascade heat exchanger, the first compressor, the second condenser, and the mixer are connected in sequence; The cascade heat exchanger, the economizer, the third throttle valve, the evaporator, the second compressor, the third compressor, the first condenser, the third condenser, and the mixer are connected in sequence; the second throttle valve is connected to the economizer; The mixer, the fourth condenser, and the separator are connected in sequence; The self-cascade high-temperature heat pump circulation system uses a mixed working fluid composed of two working fluids with different boiling points, and the separator is used to separate the mixed working fluid into a saturated gas and a saturated liquid, wherein the saturated gas and the saturated liquid both include a low-boiling-point working fluid and a high-boiling-point working fluid, and the concentration of the low-boiling-point working fluid in the saturated gas is higher than that of the high-boiling-point working fluid, and the concentration of the high-boiling-point working fluid in the saturated liquid is higher than that of the low-boiling-point working fluid; The saturated gas directly enters the cascade heat exchanger, the saturated liquid enters the cascade heat exchanger after being throttled by the first throttle valve, evaporates to form superheated steam after heat exchange with the saturated gas, and the saturated gas condenses to form saturated subcooled liquid; The superheated steam is compressed into high-temperature and high-pressure steam by the first compressor, and the high-temperature and high-pressure steam is condensed and releases heat in the second condenser to form a two-phase working medium.

2. The self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase process according to claim 1 is characterized in that: The saturated supercooled liquid is divided into a first saturated supercooled liquid and a second saturated supercooled liquid. The first saturated supercooled liquid enters the economizer after being throttled by the second throttle valve to evaporate and absorb heat to form steam; the second saturated supercooled liquid releases heat after entering the economizer to form a supercooled liquid.

3. The self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase process according to claim 2 is characterized in that: The supercooled liquid enters the evaporator after throttling and reducing the pressure through the third throttle valve to evaporate and absorb heat, thereby forming a superheated steam working medium. The superheated steam working medium enters the second compressor for compression, and then is mixed with the vapor formed by the first saturated supercooled liquid, and then is compressed by the third compressor to form high-temperature and high-pressure steam.

4. The self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase process according to claim 3 is characterized in that: After the high-temperature and high-pressure steam passes through the first condenser and the third condenser in sequence, it merges with the superheated steam formed by the saturated liquid in the cascade heat exchanger and continues to release heat.

5. The self-cascade high-temperature heat pump circulation system based on parallel compression and jet enthalpy increase process according to claim 1 is characterized in that: The second condenser and the fourth condenser are used to form low-boiling-point working fluids of different concentrations. The low-boiling-point working fluids in the second condenser and the fourth condenser are not completely condensed, and the concentration of the low-boiling-point working fluid formed in the second condenser is lower than that in the fourth condenser.

Images