A cement kiln waste heat power generation assisted carbon capture system

Abstract

The application relates to a cement kiln waste heat power generation auxiliary carbon capture system, which comprises a cement kiln waste gas recovery system, the cement kiln waste gas recovery system comprising: a kiln tail boiler, a steam turbine, a first generator, a first condenser, a feed water pump and a carbon capture subsystem; a kiln tail waste gas outlet of a cement kiln is connected with an inlet of the kiln tail boiler, a steam outlet of the kiln tail boiler, the steam turbine and the first generator are sequentially connected, a steam exhaust outlet of the steam turbine, the first condenser and the feed water pump are sequentially connected, and the feed water pump is connected with the inlet of the kiln tail boiler; and a flue gas outlet of the kiln tail boiler is connected with the carbon capture subsystem. The application utilizes the waste heat of the kiln tail waste gas of the cement kiln through the kiln tail boiler, captures and recovers carbon dioxide in the kiln tail waste gas through the carbon capture subsystem, improves the utilization efficiency of the cement kiln waste gas, and reduces carbon emission.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-carbon energy saving and emission reduction, in particular to a cement kiln waste heat power generation auxiliary carbon capture system. BACKGROUND

[0002] In the past few decades, the global consumption of fossil fuels and other non-renewable energy is huge, and the environmental pollution and carbon dioxide emissions generated in the utilization process of fossil energy and some non-renewable energy are increasingly serious. Under the "double carbon" goal, the low-carbon energy saving and emission reduction energy utilization mode has attracted widespread attention at home and abroad. Through waste heat recovery and utilization of industrial processes or comprehensive utilization of waste heat of renewable resources, useful heat and electricity can be generated, achieving the effect of reducing energy cost, relieving environmental pressure and reducing carbon dioxide emissions.

[0003] The waste heat of the cement plant cyclone preheater exhaust gas and the grate cooler exhaust air is most easily recovered and utilized. Based on this, there is an urgent need for a system that can recover the waste heat of a cement plant and reduce carbon emissions. SUMMARY

[0004] The purpose of the present application is to provide a cement kiln waste heat power generation auxiliary carbon capture system, which can improve the utilization efficiency of cement kiln exhaust gas and reduce carbon emissions.

[0005] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0006] The present application provides a cement kiln waste heat power generation auxiliary carbon capture system, comprising: a cement kiln waste gas recovery system;

[0007] The cement kiln waste gas recovery system comprises: a kiln tail boiler, a steam turbine, a first generator, a first condenser, a feed water pump and a carbon capture subsystem;

[0008] The kiln tail exhaust gas outlet of the cement kiln is connected with the inlet of the kiln tail boiler, the steam outlet of the kiln tail boiler, the steam turbine and the first generator are connected in sequence, the exhaust steam outlet of the steam turbine, the first condenser and the feed water pump are connected in sequence, and the feed water pump is connected with the inlet of the kiln tail boiler; the flue gas outlet of the kiln tail boiler is connected with the carbon capture subsystem;

[0009] The cement kiln waste heat power generation auxiliary carbon capture system further comprises: a CO2 cycle power generation system; the CO2 cycle power generation system is a supercritical CO2 Brayton cycle power generation system; the heat source of the CO2 cycle power generation system comes from the flue gas heat in the cement kiln tail exhaust gas;

[0010] The system further comprises a solar thermal power generation system; the heat source of the CO2 cycle power generation system also comes from the heat transfer working medium heat in the solar heat collector of the solar thermal power generation system.

[0011] Optionally, the cement kiln waste gas recovery system further comprises a kiln head boiler.

[0012] The kiln head waste gas outlet of the cement kiln is connected with the inlet of the kiln head boiler, and the steam outlet of the kiln head boiler is connected with the steam turbine; and the feed water pump is further connected with the inlet of the kiln head boiler.

[0013] Optionally, the carbon capture subsystem comprises: a waste gas absorption tower, a CO2 resolution tower, a first heat exchanger, a reboiler, a first pump, a second pump and a CO2 condenser.

[0014] The flue gas outlet of the kiln tail boiler is connected with the waste gas absorption tower, and the waste gas absorption tower, the second pump, the first heat exchanger, the CO2 resolution tower and the CO2 condenser are sequentially connected; the lean liquid outlet of the CO2 resolution tower is connected with the cold source inlet of the reboiler, and the heat source outlet of the reboiler, the first pump, the heat source inlet of the first heat exchanger, the cold source outlet of the first heat exchanger and the waste gas absorption tower are sequentially connected; and the waste gas absorption tower is used for absorbing CO2 of the flue gas outlet of the kiln tail boiler.

[0015] Optionally, the CO2 cycle power generation system comprises: a cooling tower, a compressor, a second heat exchanger, a turbine and a second generator.

[0016] The cooling tower, the compressor, the second heat exchanger, the turbine and the second generator are sequentially connected; the kiln tail waste gas outlet of the cement kiln is connected with the heat source inlet of the second heat exchanger, and the cold source outlet of the second heat exchanger is connected with the inlet of the kiln tail boiler.

[0017] Optionally, the exhaust outlet of the turbine is connected with the heat source inlet of the reboiler, and the cold source outlet of the reboiler is connected with the cooling tower.

[0018] The solar thermal power generation system comprises: the solar heat collector, a third heat exchanger, a fourth heat exchanger, a cold tank and a hot tank.

[0019] Optionally, the third heat exchanger and the fourth heat exchanger are both connected with the solar heat collector; the cold tank is connected with the cold source inlet of the fourth heat exchanger, the heat source outlet of the fourth heat exchanger is connected with the hot tank, the cold source inlet of the third heat exchanger is connected with the compressor, and the heat source outlet of the third heat exchanger is connected with the cold source inlet of the second heat exchanger.

[0020] According to the specific embodiments of the present application, the following technical effects are provided:

[0021] The application provides a cement kiln waste heat power generation auxiliary carbon capture system, which comprises a cement kiln waste gas recovery system, the cement kiln waste gas recovery system comprising: a kiln tail boiler, a steam turbine, a first generator, a first condenser, a feed water pump and a carbon capture subsystem; a kiln tail waste gas outlet of a cement kiln is connected with an inlet of the kiln tail boiler, a steam outlet of the kiln tail boiler, the steam turbine and the first generator are sequentially connected, a exhaust steam outlet of the steam turbine, the first condenser and the feed water pump are sequentially connected, and the feed water pump is connected with the inlet of the kiln tail boiler; and a flue gas outlet of the kiln tail boiler is connected with the carbon capture subsystem. The cement kiln waste heat power generation auxiliary carbon capture system utilizes the waste heat of the kiln tail waste gas of the cement kiln through the kiln tail boiler, captures and recovers carbon dioxide in the kiln tail waste gas through the carbon capture subsystem, improves the utilization efficiency of the cement kiln waste gas, and reduces carbon emission. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0023] Figure 1 The structural diagram of the cement kiln waste heat power generation auxiliary carbon capture system provided by the embodiments of the present application.

[0024] Symbol explanation:

[0025] 1-cement kiln waste gas recovery system; 2-CO2 circulating power generation system; 3-solar thermal power generation system; 11-kiln tail boiler; 12-steam turbine; 13-first generator; 14-first condenser; 15-feed water pump; 16-carbon capture subsystem; 17-kiln head boiler; 161-waste gas absorption tower; 162-CO2 desorption tower; 163-first heat exchanger; 164-reboiler; 165-first pump; 166-second pump; 167-CO2 condenser; 21-cooling tower; 22-compressor; 23-second heat exchanger; 24-turbine; 25-second generator; 31-solar heat collector; 32-third heat exchanger; 33-fourth heat exchanger; 34-cold tank; 35-hot tank. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] In the prior art, the waste heat utilization system of a cement plant usually adopts a steam Rankine cycle to generate power by heating feed water with waste heat contained in waste gas. In addition, other cycles such as an organic Rankine cycle, a Kalina cycle, etc. can also be implemented. The existing waste gas utilization of a cement kiln has problems such as low efficiency and serious carbon emission. Therefore, the waste gas recovery system of a cement kiln is integrated with a solar thermal power generation system and a supercritical carbon dioxide cycle, so as to realize comprehensive utilization of industrial waste heat and renewable resources and reduce carbon emission, thereby achieving the effect of low carbon, energy saving and emission reduction.

[0028] The present application provides a cement kiln waste heat power generation auxiliary carbon capture system, please refer to Figure 1 , comprising: a cement kiln waste gas recovery system 1. The cement kiln waste gas recovery system 1 comprises: a kiln tail boiler 11, a steam turbine 12, a first generator 13, a first condenser 14, a feed water pump 15 and a carbon capture subsystem 16.

[0029] The kiln tail waste gas outlet of the cement kiln is connected with the inlet of the kiln tail boiler 11, the steam outlet of the kiln tail boiler 11, the steam turbine 12 and the first generator 13 are connected in sequence, the exhaust steam outlet of the steam turbine 12, the first condenser 14 and the feed water pump 15 are connected in sequence, and the feed water pump 15 is connected with the inlet of the kiln tail boiler 11; the flue gas outlet of the kiln tail boiler 11 is connected with the carbon capture subsystem 16.

[0030] The kiln tail waste gas of the cement kiln enters the kiln tail boiler 11 to heat the feed water, so that the feed water becomes water vapor, the water vapor enters the steam turbine 12 to expand and do work, drives the first generator 13 to generate power, the exhaust steam of the steam turbine 12 is cooled by the condenser, then enters the feed water pump 15 to be heated, and then enters the kiln tail boiler 11 again for reuse.

[0031] As an optional implementation, the cement kiln waste gas recovery system 1 further comprises a kiln head boiler 17.

[0032] The kiln head waste gas outlet of the cement kiln is connected with the inlet of the kiln head boiler 17, and the steam outlet of the kiln head boiler 17 is connected with the steam turbine 12; the feed water pump 15 is also connected with the inlet of the kiln head boiler 17.

[0033] The kiln head waste gas of the cement kiln enters the kiln head boiler 17 to heat the feed water and become water vapor, the water vapor at the outlet of the kiln head boiler 17 and the water vapor at the outlet of the kiln tail boiler 11 flow in the same direction, and both enter the steam turbine 12 to expand and do work, drive the first generator 13 to generate power, the exhaust steam of the steam turbine 12 is cooled by the condenser, then enters the feed water pump 15 to be heated, and then enters the kiln head boiler 17 and the kiln tail boiler 11 respectively for reuse.

[0034] The kiln head exhaust gas and the kiln tail exhaust gas are treated separately because of different compositions, and the carbon dioxide in the kiln tail exhaust gas is recycled, so that the energy saving, low carbon and emission reduction effects of the cement kiln production process are realized.

[0035] As an optional embodiment, the carbon capture subsystem 16 comprises: an exhaust absorption tower 161, a CO2 desorption tower 162, a first heat exchanger 163, a reboiler 164, a first pump 165, a second pump 166 and a CO2 condenser 167.

[0036] The flue gas outlet of the kiln tail boiler 11 is connected with the exhaust absorption tower 161, the exhaust absorption tower 161, the second pump 166, the first heat exchanger 163, the CO2 desorption tower 162 and the CO2 condenser 167 are connected in sequence; the lean liquid outlet of the CO2 desorption tower 162 is connected with the cold source inlet of the reboiler 164, the heat source outlet of the reboiler 164, the first pump 165, the heat source inlet of the first heat exchanger 163, the cold source outlet of the first heat exchanger 163 and the exhaust absorption tower 161 are connected in sequence; the exhaust absorption tower 161 is used for absorbing CO2 of the flue gas outlet of the kiln tail boiler 11.

[0037] The outlet exhaust gas of the kiln tail boiler 11 is absorbed by the absorption tower to obtain rich liquid containing a large amount of carbon dioxide, and the rich liquid is pressurized by the second pump 166 and heated by the first heat exchanger 163, and then enters the CO2 desorption tower to separate the carbon dioxide, and the separated CO2 is condensed by the CO2 condenser 167.

[0038] The lean liquid at the bottom of the CO2 desorption tower 162 is heated by the reboiler 164, pressurized by the first pump 165 and used by the first heat exchanger 163, and then enters the absorption tower to realize recycling and reuse of the lean liquid.

[0039] The cement kiln waste heat power generation auxiliary carbon capture system further comprises: a CO2 cycle power generation system 2; the CO2 cycle power generation system 2 is a supercritical CO2 Brayton cycle power generation system; the heat source of the CO2 cycle power generation system 2 comes from the flue gas heat in the cement kiln tail exhaust gas.

[0040] The carbon dioxide cycle system refers to a system for generating power by using a supercritical CO2 Brayton cycle. The system has advantages of high efficiency and environmental protection, and is considered as one of the most potential power generation technologies in the future. At present, the system is mainly applied in the fields of nuclear energy and solar energy, but is less applied in a conventional industrial waste heat utilization system. Supercritical carbon dioxide is an ideal cycle system working medium, which has low cost, is non-combustible, non-corrosive and chemically inert. When the cycle heat source is about 600 DEG C, the carbon dioxide cycle power generation efficiency can reach 40%. In a medium-temperature and medium-pressure environment, the efficiency of the supercritical carbon dioxide cycle is higher than that of the water vapor Rankine cycle. In addition, the supercritical carbon dioxide cycle has simple equipment and is easy to manufacture, so that the investment cost and operation cost of the supercritical carbon dioxide cycle power station are low. In addition, due to the large density of supercritical CO2, the corresponding turbine mechanical size is small, and the system structure is compact.

[0041] As an optional implementation, the CO2 cycle power generation system 2 comprises a cooling tower 21, a compressor 22, a second heat exchanger 23, a turbine 24 and a second generator 25.

[0042] The cooling tower 21, the compressor 22, the second heat exchanger 23, the turbine 24 and the second generator 25 are sequentially connected. The kiln tail exhaust gas outlet of the cement kiln is connected with the heat source inlet of the second heat exchanger 23, and the cold source outlet of the second heat exchanger 23 is connected with the inlet of the kiln tail boiler 11.

[0043] In order to improve the utilization rate of the cement kiln tail exhaust gas, before the cement kiln tail exhaust gas enters the kiln tail boiler 11, the cement kiln tail exhaust gas first passes through the second heat exchanger 23, which is used as a heat source of the CO2 cycle power generation system 2, that is, the CO2 cycle working medium of the CO2 cycle power generation system 2 is heated.

[0044] In the cement kiln exhaust gas recovery system 1, the kiln tail exhaust gas passes through the second heat exchanger 23 and the kiln tail boiler 11 to recover the waste heat in the flue gas, and then passes through the exhaust gas absorption tower 161 and the CO2 desorption tower to recover the carbon dioxide in the flue gas.

[0045] As an optional implementation, the exhaust gas outlet of the turbine 24 is connected with the heat source inlet of the reboiler 164, and the cold source outlet of the reboiler 164 is connected with the cooling tower 21.

[0046] In the CO2 cycle power generation system 2, the CO2 at normal temperature and low pressure from the outlet of the cooling tower 21 enters the compressor 22, is pressurized, and then enters the second heat exchanger 23 to heat the CO2 circulating medium from the outlet of the compressor 22 by using the kiln tail gas. The CO2 circulating medium from the outlet of the second heat exchanger 23 enters the turbine 24 to expand and do work, drives the second generator 25 to generate electricity, and the CO2 circulating medium from the outlet of the turbine 24 enters the reboiler 164 to heat the lean liquid and reduce the temperature of the CO2 circulating medium, and finally returns to the cooling tower 21.

[0047] The system further comprises a solar thermal power generation system 3. The heat source of the CO2 cycle power generation system 2 further comes from the heat of the heat transfer medium in the solar heat collector 31 of the solar thermal power generation system 3.

[0048] Solar energy is the most widely distributed and most abundant permanent renewable energy. The solar energy received by the earth's surface every year is 1.05×10 18 kWh, which is equivalent to 1.3×10 6 billion tons of standard coal, which is more than the total reserves of global fossil energy resources. Developing high-efficiency solar energy utilization technology is one of the effective ways to solve the energy problem of mankind. Solar energy resource utilization technology mainly includes solar thermal power generation technology and solar photovoltaic power generation technology. Photovoltaic power generation is a technology that directly converts radiant energy into electric energy by using the photovoltaic effect of semiconductors, while thermal power generation is a technology that uses a large number of reflectors to concentrate solar energy to heat the medium, and the high-temperature medium heats water into high-temperature steam through a heat exchange device, and then combines the process of a traditional steam turbine generator to achieve the purpose of power generation.

[0049] As an optional implementation, the solar thermal power generation system 3 comprises a solar heat collector 31, a third heat exchanger 32, a fourth heat exchanger 33, a cold tank 34, and a hot tank 35.

[0050] The third heat exchanger 32 and the fourth heat exchanger 33 are connected with the solar heat collector 31; the cold tank 34 is connected with the cold source inlet of the fourth heat exchanger 33, the hot source outlet of the fourth heat exchanger 33 is connected with the hot tank 35; the cold source inlet of the third heat exchanger 32 is connected with the compressor 22, and the hot source outlet of the third heat exchanger 32 is connected with the cold source inlet of the second heat exchanger 23.

[0051] The solar energy collector 31 collects sunlight into the heat collecting pipe, thereby heating the working medium in the heat collecting pipe, and during heat absorption, the fluid is directly stored in the hot tank 35. During the heat absorption stage, the heat storage material from the cold tank 34 flows into the fourth heat exchanger 33 for indirect heating and is stored in the hot tank 35, and the working medium of the photo-thermal system preliminarily heats the carbon dioxide compressed by the compressor 22 in the supercritical carbon dioxide cycle through the third heat exchanger 32.

[0052] It should be noted that the second heat exchanger 23 and the third heat exchanger 32 are both used for heating the CO2 cycle working medium, that is, as a high-temperature heat source of the CO2 cycle power generation system 2; the lean liquid at the outlet of the CO2 stripping tower 162 is used for cooling the CO2 cycle working medium in the reboiler 164, that is, as part of the cold source of the CO2 cycle power generation system 2.

[0053] Solar thermal power generation can adapt to the intermittent characteristics of solar energy, more reasonably utilize solar energy in different time periods, the solar photo-thermal power station can store solar energy in the form of heat energy when not generating electricity, release the stored heat and generate electricity when the solar radiation is low, can bear part of the peak shaving pressure, and enables the power system to continuously and stably operate.

[0054] The heat in the solar energy collector 31 in the solar photo-thermal power generation system 3 can be used to heat the CO2 cycle working medium of the carbon dioxide cycle system, or the heat can be stored in the hot tank 35 through the fourth heat exchanger 33, so that the system peak shaving effect can be achieved.

[0055] The working medium temperature at the outlet of the solar energy collector 31 is about 300 DEG C, the cement kiln tail gas temperature is about 400 DEG C, according to the principle of “temperature matching and cascade utilization”, the CO2 cycle working medium in the CO2 cycle system is sequentially heated through the second heat exchanger 23 and the third heat exchanger 32.

[0056] The cement kiln waste heat power generation auxiliary carbon capture system coupled with the photo-thermal system and the CO2 cycle provided by the application is a system integration of the solar photo-thermal power generation system 3, the CO2 cycle power generation system 2 and the cement kiln waste gas recovery system 1. The integrated system has a total power generation capacity greater than the sum of the original cement kiln waste heat power generation system and the photo-thermal power generation system under the condition that the illumination condition and the cement kiln outlet exhaust gas amount are unchanged, and the kiln tail gas collects and stores carbon dioxide through the carbon capture subsystem 16, so that the system can realize energy saving, low carbon and emission reduction operation.

[0057] The application is directed to a cement kiln waste heat power generation auxiliary carbon capture system coupled with a photo-thermal system and a CO2 cycle, a modification and change of an existing unit are proposed, and the scheme has less safety influence, solves the problems that industrial waste heat cannot be utilized and renewable resource power generation efficiency is low, meanwhile, reduces the investment and operation and maintenance cost of the system equipment, reduces the occupied area, and provides a more efficient and economic idea for how to rationally utilize the cement kiln waste heat and efficiently utilize the renewable resources.

[0058] The principles and implementation manners of the application are described by using specific examples in the present article, and the above examples are only used for helping to understand the method of the application and its core idea; meanwhile, according to the idea of the application, the specific implementation manners and application ranges will be changed by the general technical personnel in the field. In summary, the content of the present description should not be understood as the limitation of the application.

Claims

1. A cement kiln waste heat power generation auxiliary carbon capture system, characterized in that, The system comprises: a cement kiln waste gas recovery system, which comprises: a kiln tail boiler, a steam turbine, a first generator, a first condenser, a feed water pump and a carbon capture subsystem; a kiln tail waste gas outlet of a cement kiln is connected with an inlet of the kiln tail boiler, a steam outlet of the kiln tail boiler, the steam turbine and the first generator are sequentially connected, a exhaust steam outlet of the steam turbine, the first condenser and the feed water pump are sequentially connected, the feed water pump is connected with the inlet of the kiln tail boiler; a flue gas outlet of the kiln tail boiler is connected with the carbon capture subsystem; the cement kiln waste heat power generation auxiliary carbon capture system further comprises: a CO2 cycle power generation system; the CO2 cycle power generation system is a supercritical CO2 Brayton cycle power generation system; a heat source of the CO2 cycle power generation system comes from flue gas heat in the cement kiln tail waste gas; the system further comprises a solar thermal power generation system; a heat source of the CO2 cycle power generation system also comes from heat transfer working medium heat in a solar heat collector of the solar thermal power generation system; wherein the solar heat collector collects sunlight into a heat collection pipe, thereby heating the working medium in the heat collection pipe; during heat absorption, the fluid is directly stored in a hot tank; during the heat absorption stage, the heat storage material from the cold tank flows into the fourth heat exchanger for indirect heating and is stored in the hot tank; the working medium of the solar thermal system preliminarily heats the carbon dioxide after compression in the supercritical carbon dioxide cycle through the third heat exchanger; the second heat exchanger and the third heat exchanger are both used for heating the CO2 cycle working medium, i.e., as a high-temperature heat source of the CO2 cycle power generation system; the CO2 cycle power generation system comprises: a cooling tower, a compressor, a second heat exchanger, a turbine and a second generator; the cooling tower, the compressor, the second heat exchanger, the turbine and the second generator are sequentially connected; a kiln tail waste gas outlet of the cement kiln is connected with a heat source inlet of the second heat exchanger, and a cold source outlet of the second heat exchanger is connected with an inlet of the kiln tail boiler; the cement kiln tail waste gas first passes through the second heat exchanger as a heat source of the CO2 cycle power generation system, and then enters the kiln tail boiler; the carbon capture subsystem comprises: a waste gas absorption tower, a CO2 desorption tower, a first heat exchanger, a reboiler, a first pump, a second pump and a CO2 condenser; an exhaust gas outlet of the turbine is connected with a heat source inlet of the reboiler, and a cold source outlet of the reboiler is connected with the cooling tower.

2. The system of claim 1, wherein, the cement kiln waste gas recovery system further comprises a kiln head boiler; a kiln head waste gas outlet of the cement kiln is connected with an inlet of the kiln head boiler, and a steam outlet of the kiln head boiler is connected with the steam turbine; the feed water pump is further connected with the inlet of the kiln head boiler.

3. The system according to claim 2, wherein The flue gas outlet of the kiln tail boiler is connected with the waste gas absorption tower, the waste gas absorption tower, the second pump, the first heat exchanger, the CO2 resolution tower and the CO2 condenser are connected in sequence; the lean liquid outlet of the CO2 resolution tower is connected with the cold source inlet of the reboiler, the heat source outlet of the reboiler, the first pump, the heat source inlet of the first heat exchanger, the cold source outlet of the first heat exchanger and the waste gas absorption tower are connected in sequence; the waste gas absorption tower is used for absorbing CO2 of the flue gas outlet of the kiln tail boiler.

4. The system of claim 1, wherein, The solar thermal power generation system comprises the solar heat collector, a third heat exchanger, a fourth heat exchanger, a cold tank and a hot tank. The third heat exchanger and the fourth heat exchanger are connected with the solar heat collector; the cold tank is connected with the cold source inlet of the fourth heat exchanger, and the heat source outlet of the fourth heat exchanger is connected with the hot tank; the cold source inlet of the third heat exchanger is connected with the compressor, and the heat source outlet of the third heat exchanger is connected with the cold source inlet of the second heat exchanger.

Images