Method for recovering industrial low-temperature heat energy and externally-hung heat pump system

Abstract

The present application belongs to the technical field of industrial production energy recovery. It relates to a method for recovering industrial low-temperature heat energy and an external heat pump system. An external heat pump system is arranged outside a process device. Process streams in the process device are transported to the external heat pump system and exchange heat with heat pump working medium arranged in the external heat pump system. The heat pump working medium after absorbing heat is transported to the process device to replace the original heating medium and provide heat for the process device. The external heat pump system comprises a process stream inlet, a process stream outlet, a heat pump working medium inlet, a heat pump working medium outlet, a partition wall heat exchanger and a pressure boosting device for boosting the pressure of the process stream or the heat pump working medium. In the present application, the external heat pump system and the process device are only connected by pipes without changing the original space arrangement and process flow. The waste heat in the process device is absorbed by the heat pump working medium, and the heat pump working medium replaces the original heating medium, thereby reducing the consumption of the original heating medium.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial production energy recovery, and relates to a method for recovering industrial low-temperature heat energy and an externally-mounted heat pump system. BACKGROUND

[0002] In a conventional industrial production device, a large amount of low-temperature heat energy is not recovered and reused for engineering heat supply, but is dissipated to the nature in a cooling manner, resulting in waste of energy resources. A typical example is a rectification process in chemical production: the vapor-phase material coming out of the top of the rectification tower is usually cooled and condensed by circulating water, without recovering and utilizing the condensation latent heat and cooling sensible heat of the material, and additionally consuming the operation energy and water resources of the cooling system.

[0003] In the technical innovations disclosed in recent years, heat pump technology has been integrated into the heat integration energy-saving scheme of industrial processes including the rectification process, and the process flow structure of the conventional technical scheme used by the industry has been innovatively changed, and the heat pump subsystem is embedded in the rectification process. This method is suitable for newly built production devices, but for the production devices built with the conventional technical scheme, due to the large size of the equipment in the heat pump subsystem, it is difficult to install it in the existing equipment spacing, and even the pipeline configuration will cause space collision and be difficult to solve.

[0004] At present, the status of process industry in China is that for most bulk products, the production capacity of the built devices can meet the demand of the domestic market and even the international market, and a large number of new devices will inevitably bring a huge surplus and waste of production capacity, which is not conducive to the stable development of social economy. Therefore, a key factor for China to realize green manufacturing and green development is to develop a technical scheme suitable for the existing devices with the conventional technical scheme without major engineering construction, and to utilize the heat pump technology to achieve energy saving and emission reduction to a large extent. It is inevitable trend to create an implementable method and device around this growth point for technological innovation. SUMMARY

[0005] Therefore, the present application aims to solve the problem that a large amount of low-temperature heat energy in the industrial production device is not recovered and utilized, and the existing heat energy recovery technology is not suitable for energy saving and emission reduction upgrading and reconstruction of the built process device, and the engineering implementation is difficult, and provides a method for recovering industrial low-temperature heat energy and an externally-mounted heat pump system.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] The application discloses a method for recycling industrial low-temperature heat energy, and the method comprises the following steps: arranging an external heat pump system with a heat pump working medium flow outside a process device; conveying a process flow carrying heat energy in the process device into the external heat pump system to exchange heat with the heat pump working medium flow; and conveying the heat pump working medium flow after absorbing heat energy into a heating device of the process device to replace original heating working medium in the process device and provide heat for the process device.

[0008] The application discloses a method for recycling industrial low-temperature heat energy, and the method comprises the following steps: arranging an external heat pump system with a heat pump working medium flow outside a process device; conveying a process flow carrying heat energy in the process device into the external heat pump system to exchange heat with the heat pump working medium flow; and conveying the heat pump working medium flow after absorbing heat energy into a heating device of the process device to replace original heating working medium in the process device and provide heat for the process device.

[0009] Further, the heat pump working medium flow is changed from liquid state to steam state after absorbing heat energy, and the steam state heat pump working medium flow is lifted in pressure or directly conveyed into the process device to exchange heat; the heat pump working medium flow after releasing heat energy is changed from steam state to liquid state, and the liquid state heat pump working medium flow is returned into the external heat pump system to circulate heat exchange, or the liquid state heat pump working medium flow is conveyed outside the external heat pump system and new liquid state heat pump working medium flow is introduced from outside the external heat pump system into the external heat pump system.

[0010] Further, the process flow generated by the process device is in steam state, and the steam state process flow is lifted in pressure or directly conveyed into the external heat pump system to exchange heat with the heat pump working medium flow by wall heat exchange; the process flow after releasing heat energy is changed from steam state to liquid state, and the liquid state process flow is returned into the process device or conveyed outside the process device.

[0011] Further, the lifting in pressure process adopts single-stage or multi-stage series pressure lifting mode, and liquid spraying is performed after the pressure lifting.

[0012] The steam state heat pump working medium or steam state process flow is lifted in pressure to increase condensation temperature, so that the heat transfer temperature difference requirement of the heat exchange process is met, and liquid spraying is performed after the pressure lifting to reduce steam superheat degree.

[0013] Further, the heat pump working fluid stream is the same as the original heating working fluid composition in the process device, and the original heating device in the process device does not need to be changed, does not interfere with the original process flow of the process device, and can be conveniently selected whether to use the external heat pump system during operation of the process device, realizing non-stop switching and not reducing the operation reliability and safety of the process device.

[0014] Further, the number of the process streams and the heat pump working fluid streams is at least one, which can realize the extraction of process streams from multiple positions of the process device for simultaneous waste heat recovery.

[0015] Further, the number of the process devices and the external heat pump systems is at least one, which can concentrate the heat energy in multiple process devices for unified allocation.

[0016] An external heat pump system for recovering industrial low-temperature heat energy, comprising a partitioned heat exchanger, the partitioned heat exchanger comprising a cold fluid channel and a hot fluid channel, the external heat pump system further comprising a process stream inlet for introducing a process stream carrying heat energy in a process device, a heat pump working fluid inlet for introducing a heat pump working fluid stream absorbing heat energy in the process stream, and a process stream outlet and a heat pump working fluid outlet; the process stream inlet is connected to the hot fluid channel inlet through a pipeline; the process stream outlet is connected to the hot fluid channel outlet through a pipeline; the heat pump working fluid inlet is connected to the cold fluid channel inlet through a pipeline; the heat pump working fluid outlet is connected to the cold fluid channel outlet through a pipeline; a booster device is arranged on the pipeline between the cold fluid channel outlet and the heat pump working fluid outlet and / or on the pipeline between the hot fluid channel inlet and the process stream inlet.

[0017] Further, the booster device adopts a single-stage or multi-stage fluid jet booster or compressor; a spray tank for reducing steam superheat degree is arranged after the booster device, and the spray tank is connected to the booster device through a pipeline.

[0018] Further, the partitioned heat exchanger, the process stream inlet, the heat pump working fluid outlet, the process stream outlet, and the heat pump working fluid inlet each have a plurality of them.

[0019] Further, each of the hot fluid channel inlets is respectively connected to one process stream inlet, or multiple hot fluid channel inlets are connected to the same process stream inlet; each of the hot fluid channel outlets is respectively connected to one process stream outlet, or multiple hot fluid channel outlets are connected to the same process stream outlet; each of the cold fluid channel inlets is respectively connected to one heat pump working fluid inlet, or multiple cold fluid channel inlets are connected to the same heat pump working fluid inlet; and each of the cold fluid channel outlets is respectively connected to one heat pump working fluid outlet, or multiple cold fluid channel outlets are connected to the same heat pump working fluid outlet.

[0020] Further, an auxiliary device is arranged on the pipeline, and the auxiliary device is a tank, a groove, a pump or a valve.

[0021] The present application has the following advantages:

[0022] 1) The present application sets an external heat pump system outside the process device, and the process stream carrying heat energy in the process device exchanges heat with the heat pump working fluid stream through the external heat pump system, and then the heat pump working fluid stream after absorbing heat energy replaces the original heating working fluid in the process device to provide heat for the process device, and the low-temperature waste heat in the process stream is recycled and reused, reducing the consumption of the original heating working fluid.

[0023] 2) The external heat pump system in the present application is arranged outside the process device, and can be arranged in an independent space position, and only needs to be connected through a pipeline with the existing process device, without changing the original space arrangement of the process device and disturbing the original process flow of the process device, and whether to use the heat pump system can be conveniently selected in operation, realizing non-stop switching and not reducing the operation reliability and safety of the process device.

[0024] 3) In the present application, the pressure boosting equipment and connecting pipelines and equipment in the heat pump working fluid circulation only contact clean and non-corrosive heat pump working fluid streams, reducing the requirements for corrosion resistance and safety risks of the material.

[0025] 4) The external heat pump system in the present application has strong universality and can be applied to various types of process devices, especially to a large extent for energy saving and emission reduction in industrial distillation processes.

[0026] 5) By using the method and external heat pump system in the present application, the waste heat is recovered while reducing the consumption of the original heating working fluid, and compared with the original process, energy saving and emission reduction is more than 30%.

[0027] Other advantages, objects and features of the present application will be explained in the following description, and to some extent, will be obvious to those skilled in the art based on the following study, or can be taught from the practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the following description. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the preferred detailed description of the present application will be made below in combination with the drawings, in which:

[0029] Figure 1 The flow chart of the method for recovering industrial low-temperature heat energy in the present application is shown in the figure;

[0030] Figure 2An optional structure schematic diagram of the external heat pump system in the present application;

[0031] Figure 3 Another optional structure schematic diagram of the external heat pump system in the present application;

[0032] Figure 4 A whole schematic diagram of a traditional process device;

[0033] Figure 5 A whole schematic diagram of the external heat pump system in the embodiment 1 of the present application;

[0034] Figure 6 A whole schematic diagram of the external heat pump system in the embodiment 2 of the present application.

[0035] The figure mark: 1, process stream import; 2, process stream export; 3, heat pump working medium export; 4, heat pump working medium import; 5, partition heat exchanger; 6, compressor; 1-1, pre-distillation column; 1-2, pressurized column; 1-3, atmospheric column; 1-4, recovery column; 1-5, crude methanol pre-heater; 1-6, pre-distillation column first stage condenser; 1-7, pre-distillation column reflux tank; 1-8, pre-distillation column second stage condenser; 1-9, non-condensable gas separator; 1-10, pre-distillation column reboiler; 1-11, intermediate pre-heater; 1-12, pressurized column reboiler; 1-13, atmospheric column reboiler; 1-14, pressurized column reflux tank; 1-15, first refined methanol cooler; 1-16, atmospheric column condenser; 1-17, atmospheric column reflux tank; 1-18, second refined methanol cooler; 1-19, recovery column condenser; 1-20, recovery column reflux tank; 1-21, recovery column reboiler; LS, live steam pipeline; LC, steam condensate pipeline; 2-1, first heat pump compressor; 2-2, first partition heat exchanger; 2-3, second partition heat exchanger; 2-4, second heat pump compressor; 2-5, first process stream import; 2-6, first process stream export; 2-7, second process stream import; 2-8, second process stream export. DETAILED DESCRIPTION

[0036] The present application is described herein with reference to particular non-limiting embodiments. Variations to those embodiments can be understood and effected within the framework of the application as described in the location of the appended claims, the drawings and the specification. The examples below are provided to illustrate the present application and should not be construed as limiting the scope of the application. The drawings are not to scale and are provided merely to clarify the present application. The features of the examples described below can be combined with each other, if not contradictory.

[0037] The drawings are only used for exemplary illustration, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the present application; in order to better illustrate the embodiments of the present application, some components of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0038] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back" and the like are based on the orientations or positional relationships shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary illustration, and cannot be understood as a limitation on the present application, for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0039] Please refer to Figure 1 , the process flow diagram of the method for recovering industrial low-temperature heat energy in the present application, an external heat pump system provided with a heat pump working medium stream inside is installed outside the process device, the process stream carrying heat energy in the process device is transported to the external heat pump system, and the heat energy is transferred to the heat pump working medium stream through the external heat pump system; the heat pump working medium stream after absorbing heat energy is transported to the heating device of the process device to replace the original heating working medium, thereby supplying heat to the process device; wherein the heat pump working medium stream is converted from liquid state to vapor state after absorbing heat energy, the vapor state heat pump working medium stream is raised in pressure or directly transported to the process device for heat exchange; the heat pump working medium stream after releasing heat energy is converted from vapor state to liquid state, the liquid state heat pump working medium stream is returned to the external heat pump system for cyclic heat exchange, or the liquid state heat pump working medium stream is transported outside the external heat pump system and new liquid state heat pump working medium stream is introduced from outside the external heat pump system into the external heat pump system; wherein the process stream generated by the process device is in vapor state, the vapor state process stream is raised in pressure or directly transported to the external heat pump system for wall-type heat exchange with the heat pump working medium stream; the process stream after releasing heat energy is converted from vapor state to liquid state, the liquid state process stream is returned to the process device or the liquid state process stream is transported outside the process device.

[0040] Please refer to Figures 2-3Fig. 1 is a schematic diagram of the external heat pump system of the present application, which comprises a process stream inlet 1, a process stream outlet 2, a heat pump working medium inlet 4, a heat pump working medium outlet 3, and a partition wall heat exchanger 5. The process stream inlet 1 and the process stream outlet 2 are in communication with the hot fluid passage of the partition wall heat exchanger 5, and the heat pump working medium inlet 4 and the heat pump working medium outlet 3 are in communication with the cold fluid passage of the partition wall heat exchanger 5. A compressor 6 is installed on the pipeline between the cold fluid passage outlet and the heat pump working medium outlet 3 and / or on the pipeline between the hot fluid passage inlet and the process stream inlet 1.

[0041] Comparative Example

[0042] Referring to Fig. 1 Figure 4 The present example is a conventional four-column double-effect distillation process device for synthesizing methanol, which is used to refine crude methanol into refined methanol. The process device comprises a pre-distillation column 1-1, a pressurized column 1-2, an atmospheric column 1-3, a recovery column 1-4, a crude methanol pre-heater 1-5, a pre-distillation column first condenser 1-6, a pre-distillation column reflux tank 1-7, a pre-distillation column second condenser 1-8, a non-condensable gas separator 1-9, a pre-distillation column reboiler 1-10, an intermediate pre-heater 1-11, a pressurized column reboiler 1-12, an atmospheric column reboiler 1-13, a pressurized column reflux tank 1-14, a first refined methanol cooler 1-15, an atmospheric column condenser 1-16, an atmospheric column reflux tank 1-17, a second refined methanol cooler 1-18, a recovery column condenser 1-19, a recovery column reflux tank 1-20, a recovery column reboiler 1-21, a live steam pipeline LS, and a steam condensate pipeline LC. The atmospheric column reboiler 1-13 is heated by refined methanol steam from the top of the pressurized column 1-2. The pre-distillation column reboiler 1-10, the pressurized column reboiler 1-12, and the recovery column reboiler 1-21 all need to be heated by live steam, which consumes a large amount of live steam.

[0043] Example 1

[0044] Referring to Fig. 1 Figure 5 The present example is based on the comparative example, and an external heat pump system is additionally installed outside the process device. In the present example, the process stream is refined methanol, the heat pump working medium is water, and the pressure boosting device is a compressor.

[0045] The refined methanol vapor is introduced from the pipeline between the top of the atmospheric column 1-3 and the atmospheric column condenser 1-16, introduced into the external heat pump system through the first process stream inlet 2-5, the first process stream inlet 2-5 is communicated with the first heat pump compressor 2-1, the refined methanol vapor is compressed by the first heat pump compressor 2-1, enters the first partition wall heat exchanger 2-2, exchanges heat with the liquid water, transfers the heat energy to the water, and returns to the process device from the first process stream outlet 2-6, enters the original subsequent treatment process; the liquid water is changed into water vapor after absorbing heat in the first partition wall heat exchanger 2-2, the water vapor is compressed by the second heat pump compressor 2-4, is transported to the process device through the heat pump working medium outlet 3 to replace the original heating medium, that is, live steam, enters the pressurized column reboiler 1-12 through the live steam pipeline LS to supply heat for the pressurized column reboiler 1-12, the water vapor is changed into liquid water after heat exchange, is introduced from the steam condensate pipeline LC of the pressurized column reboiler 1-12, returns to the external heat pump system through the heat pump working medium inlet 4, and enters the first partition wall heat exchanger 2-2 to exchange heat and circulate.

[0046] The first heat pump compressor 2-1 and the second heat pump compressor 2-4 are both multi-stage compression, and spraying is performed between stages to reduce the superheat degree of the steam.

[0047] Example 2

[0048] Please refer to Figure 6 , this embodiment is further optimized on the basis of example 1, the difference lies in that the external heat pump system is additionally provided with the second partition wall heat exchanger 2-3, the second process stream inlet 2-7 and the second process stream outlet 2-8; wherein the first partition wall heat exchanger 2-2 and the second partition wall heat exchanger 2-3 are connected in parallel, the heat pump working medium inlet 4 is communicated with the first partition wall heat exchanger 2-2 and the second partition wall heat exchanger 2-3 respectively, the liquid water introduced from the heat pump working medium inlet 4 exchanges heat in the first partition wall heat exchanger 2-2 and the second partition wall heat exchanger 2-3 respectively, and is changed into water vapor, the two streams of water vapor are combined and then enter the second heat pump compressor 2-4 to be compressed and pressurized, and then are transported to the process device through the heat pump working medium outlet 3 to supply heat for the process device.

[0049] In this embodiment, there are two process streams carrying heat energy, one of which is refined methanol liquid, introduced from the pipeline between the pressurized column reflux tank 1-14 and the first refined methanol cooler 1-15, introduced into the second process stream inlet 2-7, and returned to the process device from the second process stream outlet 2-8 after heat exchange; the other is refined methanol vapor, introduced from the pipeline between the top of the atmospheric column 1-3 and the atmospheric column condenser 1-16, introduced into the first process stream inlet 2-5, and returned to the process device from the first process stream outlet 2-6 after compression, pressurization and heat exchange.

[0050] In the embodiment, the water vapor is introduced into the pre-fractionation column reboiler 1-10, the pressurized column reboiler 1-12 and the recovery column reboiler 1-21 in the process device through the heat pump working medium outlet 3 after being compressed and boosted, and provides heat for the column reboilers, and is condensed into liquid water after heat exchange, and is returned to the external heat pump system through the heat pump working medium inlet 4, so as to realize heat energy recycling.

[0051] Finally, the energy consumption of the comparative example, example 1 and example 2 is counted, and the specific energy consumption comparison is shown in Table 1.

[0052] Table 1 Energy consumption comparison

[0053]

[0054] As shown in Table 1, the energy saving of the traditional process device using the external heat pump system of the present application is 32.5% and 41.8% respectively.

[0055] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. An external heat pump system for recovering industrial low-temperature heat energy, comprising a partition heat exchanger, wherein the partition heat exchanger includes a cold fluid channel and a hot fluid channel, characterized in that: The external heat pump system also includes a process stream inlet for introducing the process stream carrying heat energy in the process unit, a heat pump working fluid inlet for introducing the heat pump working fluid stream that absorbs heat energy in the process stream, as well as a process stream outlet and a heat pump working fluid outlet. The process flow inlet is connected to the hot fluid channel inlet via a pipeline; the process flow outlet is connected to the hot fluid channel outlet via a pipeline; the heat pump working fluid inlet is connected to the cold fluid channel inlet via a pipeline; the heat pump working fluid outlet is connected to the cold fluid channel outlet via a pipeline; a pressure boosting device is provided on the pipeline between the cold fluid channel outlet and the heat pump working fluid outlet and / or on the pipeline between the hot fluid channel inlet and the process flow inlet; the pressure boosting device is a single-stage or multi-stage fluid jet booster or compressor; a spray tank for reducing steam superheat is provided after the pressure boosting device, and the spray tank is connected to the pressure boosting device via a pipeline; The indirect heat exchanger has two inlet and two outlets for the process stream, namely, a first indirect heat exchanger, a second indirect heat exchanger, a first process stream inlet, a second process stream inlet, a first process stream outlet, and a second process stream outlet. The first wall-mounted heat exchanger and the second wall-mounted heat exchanger are connected in parallel. The inlet of the heat pump working fluid is connected to the inlet of the cold fluid channel of the first wall-mounted heat exchanger and the second wall-mounted heat exchanger, respectively. The outlet of the cold fluid channel of the first wall-mounted heat exchanger and the outlet of the cold fluid channel of the second wall-mounted heat exchanger are merged and connected to the outlet of the heat pump working fluid through the second heat pump compressor. The inlet of the first process stream is connected to the inlet of the hot fluid channel of the first indirect heat exchanger via the first heat pump compressor, and the outlet of the hot fluid channel of the first indirect heat exchanger is connected to the outlet of the first process stream; the inlet of the second process stream is connected to the inlet of the hot fluid channel of the second indirect heat exchanger, and the outlet of the hot fluid channel of the second indirect heat exchanger is connected to the outlet of the second process stream.

2. The external heat pump system for recovering industrial low-temperature heat energy according to claim 1, characterized in that: The pipeline is equipped with auxiliary equipment, which may be a tank, trough, pump, or valve.

3. A method for recovering industrial low-temperature heat energy, characterized in that: An external heat pump system as described in any one of claims 1 to 2 is installed outside the process unit to transport the process flow carrying heat energy in the process unit to the external heat pump system, and to transfer the heat energy to the heat pump working fluid flow through the external heat pump system. The heat pump working fluid, after absorbing heat energy, is transported to the heating device of the process unit to replace the original heating working fluid in the process unit and provide heat to the process unit.

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