CN110697821A - A seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system - Google Patents

Abstract

The invention discloses a seawater source transcritical carbon dioxide heat pump circulating multi-effect seawater desalination system, and the whole system is applied to the field of seawater desalination. The main equipment includes solar collector, multi-effect seawater distiller, expansion tank, heat transfer oil-seawater heat exchanger, molten salt-heat transfer oil heat exchanger, high temperature molten salt storage tank, low temperature molten salt storage tank, carbon dioxide evaporator, Carbon dioxide compressor unit, carbon dioxide expansion unit, condenser and other components. The invention overcomes the day and night intermittency of solar energy by setting the molten salt heat storage module, so that the system can work continuously; by setting the carbon dioxide heat pump unit, the compressor is used to compress the carbon dioxide to the supercritical carbon dioxide with high density, and the equipment volume of the heat pump cycle is small. ;Using seawater source transcritical carbon dioxide heat pump system to absorb seawater heat, and then multi-effect desalination of seawater through seawater distiller, so as to achieve high-efficiency seawater desalination.

Description

A seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system

technical field

The invention belongs to the fields of solar energy utilization and seawater desalination, relates to a heat pump seawater desalination technology, in particular to a solar-assisted seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system technology.

Background technique

Fresh water is one of the substances that humans come to survive and develop. The scarcity of freshwater resources has become increasingly serious and has become a global environmental problem. Nearly 97.5% of the total global water resources are salt water resources such as seawater. Research on efficient and environmentally friendly seawater desalination technology is of great significance for solving the problem of water scarcity. The existing technology for seawater desalination using solar energy is very mature. Compared with traditional power sources and heat sources, solar energy has many advantages such as safety, environmental protection, no consumption of conventional energy, no pollution, and high purity of the obtained fresh water. The combination of these systems is a sustainable desalination technology, which has great application potential in areas with scarce freshwater resources and high environmental protection requirements. Among the existing seawater desalination technologies, on the basis of solar energy, it is also common to couple and utilize wind energy, geothermal heat, industrial waste heat or other energy sources.

However, as far as the current state of solar desalination technology is concerned, the efficiency of pure solar desalination is low, and the cost of pure heat pump desalination is high. The organic working fluid used in traditional heat pumps will cause greenhouse effect and ozone layer hole. The current solar seawater desalination equipment is generally large in size, high in desalination energy consumption, easy to corrode equipment, and high in overall cost. In addition, the solar energy itself is unstable and intermittent between day and night, which leads to the discontinuous operation of the solar desalination system, which also affects the energy efficiency and water production ratio of the solar desalination system to a certain extent, and increases the cost of desalination.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings and deficiencies existing in the existing solar seawater desalination technology, the purpose of the present invention is to provide a solar-assisted seawater source transcritical carbon dioxide heat pump integrated energy system to achieve high-efficiency seawater desalination, and the system utilizes solar energy to preheat seawater. , combined with transcritical carbon dioxide heat pump cycle to reduce desalination costs.

In order to achieve the above object, the present invention adopts the following technical scheme to realize:

A seawater source transcritical carbon dioxide heat pump circulation multi-effect seawater desalination system, comprising a solar heat collection and heat storage unit, a transcritical carbon dioxide heat pump unit and a seawater desalination unit, characterized in that,

--The solar heat collection and heat storage unit includes at least a solar heat collector, a high temperature side of a heat transfer oil-carbon dioxide heat exchanger, and a heat transfer oil heat exchange side of a molten salt-heat transfer oil heat exchanger, wherein,

The solar heat collector, the high temperature side of the heat-conducting oil-carbon dioxide heat exchanger, and the heat-conducting oil heat-exchanging side of the molten salt-heat-conducting oil heat exchanger are connected in sequence through pipelines to form a closed heat-conducting oil circulation loop;

A bypass pipeline is arranged between the inlet and the outlet of the solar collector, a bypass valve is arranged on the bypass pipeline, and a main valve is arranged at the inlet of the solar collector;

One end opening of the molten salt heat exchange side of the molten salt-conducting oil heat exchanger is communicated with a low temperature molten salt storage tank through a pipeline, and the other end opening is communicated with a high temperature molten salt storage tank through a pipeline;

--The transcritical carbon dioxide heat pump unit includes at least the cold side of the carbon dioxide evaporator, the carbon dioxide compressor unit, the carbon dioxide expansion unit, the heating pipeline in the first-effect seawater distiller, the cold side of the carbon dioxide evaporator, the carbon dioxide compression unit The unit, the heating pipeline in the first-effect seawater distiller, and the carbon dioxide expansion unit are connected in sequence through the pipeline to form a closed carbon dioxide circulation loop;

--The seawater desalination unit includes at least a first-effect seawater distiller, a second-effect seawater distiller, a condenser, a low temperature side of a heat transfer oil-carbon dioxide heat exchanger, a seawater diversion three-way regulating valve, and a seawater brine three-way mixing valve, which,

The inlet of the seawater diversion three-way regulating valve is formed as a new seawater inlet without desalination, and the first outlet of the seawater diversion three-way regulating valve sequentially passes through the low temperature side of the condenser, the heat transfer oil through the pipeline. - the low temperature side of the carbon dioxide heat exchanger is respectively connected with the new seawater inlets at the top of the first effect seawater distiller and the second effect seawater distiller, and the tops of the first effect seawater distiller and the second effect seawater distiller are respectively connected All new seawater inlet pipelines are equipped with pressure regulating valves;

The first-effect seawater distiller and the second-effect seawater distiller are all provided with a freshwater steam outlet at the top or near the top, and a concentrated salt water outlet at the bottom, and the freshwater steam outlet of the first-effect seawater distiller passes through a pipe. The road is communicated with the inlet of the heating pipeline arranged in the second effect seawater distiller, the outlet of the heating pipeline in the second effect seawater distiller and the fresh water steam outlet of the second effect seawater distiller are respectively It is communicated with the high temperature side inlet of the condenser through a pipeline, and the high temperature side outlet of the condenser is formed as a desalinated water outlet; the concentrated brine outlet of the first effect seawater distiller is connected to the In the second effect seawater distiller, the concentrated brine outlet of the second effect seawater distiller is divided into two branches, wherein the first branch directly discharges the concentrated brine, and a regulating valve is provided on the first branch, The second branch is communicated with the first inlet of the seawater brine three-way mixing valve, and the second inlet of the seawater brine three-way mixing valve is connected to the second outlet of the seawater diversion three-way regulating valve through a pipeline. The outlet of the seawater brine three-way mixing valve is communicated with the hot side inlet of the carbon dioxide evaporator through a pipeline, and the hot side outlet of the carbon dioxide evaporator is formed as a seawater discharge port.

Preferably, in the transcritical carbon dioxide heat pump unit, the carbon dioxide expansion unit expands the carbon dioxide introduced into it to a subcritical state, and the subcritical carbon dioxide is introduced into the cold side of the carbon dioxide evaporator to absorb heat, and then passes through the The compressor unit reaches a supercritical state after being compressed.

Preferably, the solar heat collection and storage unit further includes a heat transfer oil pump, which is arranged on the heat transfer oil circulation circuit to drive the heat transfer oil in the circulation circuit to circulate among the components.

Further, the heat transfer oil pump is arranged on the inlet pipeline and/or the outlet pipeline of the solar heat collector.

Preferably, an expansion tank is further provided in the heat-conducting oil circulation circuit, and the expansion tank is used to adapt to the heat-conducting oil being heated and increasing its volume and replenishing the heat-conducting oil when the heat-conducting oil is insufficient.

Further, the expansion tank is arranged on the communication pipeline between the solar heat collector and the high temperature side of the heat transfer oil-carbon dioxide heat exchanger.

Further, the expansion tank is also provided with a heat-conducting oil supplementary pipeline with a valve and a heat-conducting oil discharge pipeline with a valve. When the heat-conducting oil needs to be replaced, open the valve on the heat-conducting oil discharge pipeline and let go of the old heat-conducting oil. oil; when the heat transfer oil needs to be added, open the valve on the heat transfer oil supplementary pipeline.

Preferably, after the new seawater flows through the condenser and the heat transfer oil-carbon dioxide heat exchanger in sequence, the temperature rises, and then enters the first-effect seawater distiller and the second-effect seawater distiller for split-effect desalination, wherein the The working pressure in the first effect seawater distiller is higher than the second effect seawater distiller.

Preferably, the concentrated brine discharged from the second-effect seawater distiller and the new seawater shunted by the seawater three-way regulating valve are mixed in a certain proportion in the seawater-brine three-way mixing valve as the carbon dioxide evaporator The heat source increases the average endothermic temperature of the carbon dioxide heat pump unit.

Preferably, the seawater desalination unit further comprises a seawater drainage pump, a concentrated brine pump and a desalination water pump, wherein the seawater drainage pump is arranged on the seawater discharge pipeline of the carbon dioxide evaporator, and the concentrated brine pump is arranged On the concentrated brine outlet pipeline of the second effect seawater distiller, the desalination water pump is arranged on the high temperature side outlet pipeline of the condenser.

Preferably, the system includes at least a heat storage and heat pump desalination mode, a heat release and heat pump desalination mode, a heat storage and flash desalination mode, and an exothermic and flash desalination mode.

Further, when the solar energy is sufficient, the heat storage and heat pump desalination mode is activated. At this time, the bypass valve in the solar heat collection and heat storage unit is closed, the main circuit valve is opened, and the heat transfer oil in the heat transfer oil circulation loop is transported. into the solar heat collector, the heated high-temperature heat-conducting oil is passed into the heat-conducting oil heat-exchanging side of the molten salt-heat-conducting oil heat exchanger, and the low-temperature molten salt in the low-temperature molten salt storage tank is transported to the After the molten salt heat exchange side of the molten salt-conducting oil heat exchanger is heated to the heat storage temperature by the high-temperature heat-conducting oil in the heat-conducting oil heat-exchanging side, it is passed into the high-temperature molten salt storage tank; In the desalination mode, in the carbon dioxide heat pump unit, the carbon dioxide passed into the cold side of the carbon dioxide evaporator absorbs heat to form a superheated gas of 10-20°C, and the superheated carbon dioxide is compressed by the carbon dioxide compressor unit to reach a supercritical state. , and the temperature reaches a high temperature of 100-120 ° C, then high-temperature supercritical carbon dioxide enters the heating pipeline of the first-effect seawater distiller to heat the seawater therein, and the carbon dioxide after exothermic is expanded through the carbon dioxide expansion unit. Then the energy is converted into mechanical energy, and becomes a low-temperature and low-pressure carbon dioxide gas-liquid mixture. Finally, the carbon dioxide gas-liquid mixture is passed into the cold side of the evaporator and then becomes carbon dioxide superheated gas again to complete the carbon dioxide working medium cycle; In the heat pump desalination mode, the new seawater introduced into the low temperature side of the heat transfer oil-carbon dioxide heat exchanger is heated to about 40°C and then transported to the first effect seawater distiller and the second effect seawater distiller, respectively. The seawater and the concentrated brine produced by the second effect seawater distiller are directly mixed in the seawater brine three-way mixing valve and then passed into the hot side of the carbon dioxide evaporator as a heat source of the carbon dioxide evaporator.

Further, when the solar energy is sufficient but the electric energy is insufficient, the heat release and heat pump desalination mode is activated, at this time, the main valve of the solar collector is closed, the bypass valve is opened, and the high temperature in the high temperature molten salt storage tank is Molten salt flows into the molten salt heat exchange side of the molten salt-conducting oil heat exchanger, heats the heat-conducting oil in the heat-conducting oil circulation circuit to reduce the temperature, and then passes into the low-temperature molten salt storage tank. The working process of the carbon dioxide heat pump circulation unit and the seawater desalination unit is the same as that in the heat storage and heat pump desalination mode.

Further, when the solar energy is sufficient, the heat storage and flash desalination mode is activated, and the working process of the solar heat collection and heat storage unit is the same as that in the heat storage and heat pump desalination mode; at this time, the carbon dioxide heat pump circulation unit stops. Work, the new seawater flows into the low temperature side of the condenser under the action of the seawater diversion three-way regulating valve, and then flows into the low temperature side of the heat transfer oil-seawater heat exchanger after the condensate is preheated, and is heated to Flash evaporation temperature; the pressure regulating valve at the top of the first effect seawater distiller is closed, the pressure regulating valve at the top of the second effect seawater distiller is opened, and the new seawater introduced into the second effect seawater still is under pressure Under the action of the regulating valve, the pressure is reduced to the flashing pressure, and the flashing is completed in the second effect seawater distiller. The flashed steam flows into the high temperature side of the condenser and is condensed. The concentrated brine produced in the seawater distiller is directly discharged.

Further, when the solar energy is insufficient and the electric energy is also insufficient, the exothermic and flash desalination modes are activated. At this time, the main circuit valve of the solar collector is closed, the bypass valve is opened, and the high temperature molten salt storage tank is stored. The high-temperature molten salt flows into the molten salt heat exchange side of the molten salt-conducting oil heat exchanger, heats the heat-conducting oil in the heat-conducting oil circulation circuit and reduces the temperature, and then passes into the low-temperature molten salt storage tank. The working process of the desalination unit is the same as in the heat storage and flash desalination modes.

Preferably, when there is no electric power input to the carbon dioxide compressor unit, flash distillation to produce desalinated water is realized by adjusting the pressure regulating valve at the top of the second-effect seawater distiller.

Further, the system can also drive the carbon dioxide compressor unit with a wind turbine, and upgrade it to a wind-powered desalination water system, without obtaining electric power from the power grid, which is beneficial to the operation of the isolated island.

Compared with the prior art, the solar-assisted seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the present invention has significant technical advantages: (1) in the seawater desalination system, specifically in the solar energy collection heat storage system; The unit adds a molten salt heat storage module, which overcomes the intermittent characteristics of solar energy day and night, so that the seawater desalination system can work continuously; (2) In the seawater desalination system, a carbon dioxide heat pump unit is installed, and the carbon dioxide critical point temperature is close to the ambient temperature. The compressor compresses carbon dioxide to the more common supercritical carbon dioxide. Due to the high density of supercritical carbon dioxide, the heat pump cycle equipment is small in size, easy to manufacture and reduces costs; (3) Using negative pressure low temperature multi-effect seawater desalination technology, low temperature can effectively Reduce equipment corrosion, and negative pressure can reduce the temperature required for seawater distillation and reduce the energy consumption of desalination; (4) The system uses solar energy to preheat seawater, combined with transcritical carbon dioxide heat pump cycle to reduce the cost of seawater desalination.

Description of drawings

1 is a schematic diagram of a seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in Figure 1, the solar-assisted seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the present invention is composed of a seawater drainage pump 1, a carbon dioxide evaporator 2, a carbon dioxide compressor 3, a carbon dioxide expander 4, a first-effect seawater Distiller 5, second effect seawater distiller 6, concentrated brine pump 7, desalination water pump 8, condenser 9, solar collector 10, expansion tank 11, heat transfer oil-seawater heat exchanger 12, molten salt-heat transfer oil Heat exchanger 13, low temperature molten salt storage tank 14, high temperature molten salt storage tank 15, heat transfer oil pump 16, regulating valves V1, V2, V5, V6, V7, V8, V9, mixing valve V3, three-way regulating valve V4 and necessary The pipeline and other components are composed. Specifically, the solar-assisted seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the present invention includes a solar heat collection and heat storage unit, a transcritical carbon dioxide heat pump unit and a seawater desalination unit.

The solar heat collection and heat storage unit includes at least a solar heat collector 10 , a high temperature side of a heat transfer oil-carbon dioxide heat exchanger 12 , and a heat transfer oil heat exchange side of a molten salt-heat transfer oil heat exchanger 13 , wherein the solar heat collector 10 , the high temperature side of the heat-conducting oil-carbon dioxide heat exchanger 12, and the heat-conducting oil heat-exchanging side of the molten salt-heat-conducting oil heat exchanger 13 are sequentially connected through pipelines to form a closed heat-conducting oil circulation loop; A bypass pipeline is set between the outlets, a bypass valve V8 is set on the bypass pipeline, and a main valve V7 is set at the entrance of the solar collector 10; One end opening is communicated with a low temperature molten salt storage tank 14 through a pipeline, and the other end opening is communicated with a high temperature molten salt storage tank 15 through a pipeline. A heat transfer oil pump 16 is also provided in the heat transfer oil circulating circuit. Specifically, the heat transfer oil pump 16 can be arranged on the inlet pipeline and/or the outlet pipeline of the solar collector 10. The heat transfer oil pump 16 is used to drive the heat transfer oil in the heat transfer oil circulating circuit. Oil circulates between components. An expansion tank 11 is also arranged in the heat transfer oil circulation loop. Specifically, the expansion tank 11 can be arranged on the communication pipeline between the solar heat collector 10 and the high temperature side of the heat transfer oil-carbon dioxide heat exchanger 12. The expansion tank 11 is arranged in the middle, and its purpose is to adapt to the effect of the heat-conducting oil being heated to increase the volume and supplementing the heat-conducting oil when the heat-conducting oil is insufficient. Further, the expansion tank 11 is also provided with a heat-conducting oil replenishment pipeline with valve V5 and a heat-conducting oil discharge pipeline with valve V6. When the heat-conducting oil needs to be replaced, the valve V6 is opened, the old heat-conducting oil is released, and the new heat-conducting oil is released. Added from valve V5.

The transcritical carbon dioxide heat pump unit includes at least the cold side of the carbon dioxide evaporator 2, the carbon dioxide compressor unit 3, the carbon dioxide expansion unit 4, the heating pipeline in the first-effect seawater distiller 5, the cold side of the carbon dioxide evaporator 2, and the carbon dioxide compressor unit. 3. The heating pipeline in the first-effect seawater distiller 5 and the carbon dioxide expansion unit 4 are connected in sequence through pipelines to form a closed carbon dioxide circulation loop. The transcritical carbon dioxide heat pump unit uses carbon dioxide as the circulating working medium. The carbon dioxide expansion unit 4 expands the carbon dioxide to a subcritical state. The subcritical carbon dioxide absorbs heat through the carbon dioxide evaporator 2, and is compressed by the carbon dioxide compressor unit 3 to reach the supercritical state.

The seawater desalination unit includes at least the first effect seawater distiller 5, the second effect seawater distiller 6, the condenser 9, the low temperature side of the heat transfer oil-carbon dioxide heat exchanger 12, the seawater diversion three-way regulating valve V4, and the seawater brine three. Through the mixing valve V3, the inlet of the seawater diversion three-way regulating valve V4 is formed as a new seawater inlet without desalination, and the first outlet of the seawater diversion three-way regulating valve V4 passes through the low temperature side of the condenser 9, The low temperature side of the heat transfer oil-carbon dioxide heat exchanger 12 is respectively connected with the new seawater inlet at the top of the first effect seawater distiller 5 and the second effect seawater distiller 6, and the first effect seawater distiller 5 and the second effect seawater distillation Pressure regulating valves V1 and V2 are respectively provided on the new seawater inlet pipeline at the top of the device 6; the first effect seawater distiller 5 and the second effect seawater distiller 6 are provided with fresh water steam outlets at the top or at positions close to the top, and the bottoms are provided with fresh water steam outlets. There is a strong brine outlet, and the fresh water vapor outlet of the first effect seawater distiller 5 is communicated with the inlet of the heating pipeline arranged in the second effect seawater distiller 6 through a pipeline, and the heating pipeline in the second effect seawater distiller 6 is connected. The outlet of the second effect seawater distiller 6 and the fresh water steam outlet of the second effect seawater distiller 6 are respectively communicated with the high temperature side inlet of the condenser 9 through pipelines, and the high temperature side outlet of the condenser 9 is formed as a desalinated water outlet; the first effect seawater distiller The concentrated brine outlet of 5 is led into the second effect seawater distiller 6 through pipelines, and the concentrated brine outlet of the second effect seawater distiller 6 is divided into two branches, wherein the first branch directly discharges the concentrated brine, and is in the second effect seawater distiller 6. The first branch is provided with a regulating valve V9, the second branch is communicated with the first inlet of the seawater-salt three-way mixing valve V3, and the second inlet of the seawater-salting three-way mixing valve V3 is connected to the seawater diversion three-way regulating valve through a pipeline The second outlet of V4, the outlet of the seawater brine three-way mixing valve V3 is connected to the hot side inlet of the carbon dioxide evaporator 2 through a pipeline, and the hot side outlet of the carbon dioxide evaporator 2 is formed as a seawater discharge port, and the concentrated brine and the new seawater are in the seawater. The brine three-way mixing valve V3 is mixed in a certain proportion as the heat source of the carbon dioxide evaporator 2, which increases the average endothermic temperature of the carbon dioxide heat pump unit.

In the seawater desalination unit, the new seawater flows through the condenser 9 and the heat-conducting oil-carbon dioxide heat exchanger 12 in turn and the temperature rises, and then enters the first-effect seawater distiller 5 and the second-effect seawater distiller 6 for split-effect desalination. . The pressure in the first effect seawater distiller 5 is higher than that in the second effect seawater distiller 6 . Preferably, the concentrated brine outlet of the first effect seawater distiller 5 leads to the bottom of the second effect seawater distiller 6 through a pipeline. Further, the seawater desalination unit also includes a seawater drainage pump 1, a concentrated brine pump 7 and a desalination water pump 8, wherein the seawater drainage pump 1 is arranged on the seawater discharge pipeline of the carbon dioxide evaporator 2, and the concentrated brine pump 7 is arranged on the No. On the concentrated brine outlet pipeline of the two-effect seawater distiller 6 , the desalination water pump 8 is arranged on the high temperature side outlet pipeline of the condenser 9 .

The solar-assisted seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the present invention at least includes heat storage and heat pump desalination modes, heat release and heat pump desalination modes, heat storage and flash desalination modes, and heat release and flash desalination modes and other four desalination modes.

When the solar energy is sufficient, the heat storage and heat pump desalination mode is activated. At this time, the bypass valve V8 in the solar heat collection and heat storage unit is closed, and the main circuit valve V7 is opened. The heat transfer oil in the heat transfer oil circulation loop is driven by the heat transfer oil pump 16. Entering into the solar collector 10, the heated high-temperature heat-conducting oil flows into the high-temperature side of the molten salt-conducting oil heat exchanger 13, and the low-temperature molten salt in the low-temperature molten salt storage tank 14 is transported to the molten salt-conducting oil heat exchanger After the molten salt heat exchange side of 13 is heated to the heat storage temperature by the high-temperature heat transfer oil, it is passed into the high-temperature molten salt storage tank 15 .

Continuing to refer to FIG. 1 , in the heat storage and heat pump desalination mode, the temperature of the carbon dioxide superheated gas in the carbon dioxide heat pump unit after passing through the cold side of the carbon dioxide evaporator 2 to absorb heat is 10-20°C. After the superheated carbon dioxide gas is compressed by the carbon dioxide compressor unit 3, it reaches a supercritical state, and the temperature can reach a high temperature of 100-120 °C. The high-temperature supercritical carbon dioxide enters the heating pipeline of the first-effect seawater distiller 5 to heat the seawater therein. After exothermic carbon dioxide, the energy in the carbon dioxide expansion unit 4 is recovered and converted into mechanical energy, which becomes a low-temperature and low-pressure carbon dioxide gas-liquid mixture. Finally, the carbon dioxide gas-liquid mixture passes through the cold side of the evaporator 2 and becomes carbon dioxide superheated gas again to complete the carbon dioxide working medium cycle.

Continuing to refer to Figure 1, in the heat storage and heat pump desalination mode, the new seawater in the seawater desalination circuit is divided into two branches, of which the first new seawater branch flows through the low temperature side of the condenser 9, the heat transfer oil-carbon dioxide in turn The low temperature side of the heat exchanger 12 absorbs heat and then enters the first effect seawater distiller 5 to reduce irreversible heat transfer losses in the first effect seawater distiller 5 . The second new seawater branch and the concentrated brine produced by the second effect seawater distiller 6 are directly mixed at the mixing valve V3 and then passed into the hot side of the carbon dioxide evaporator 2 as the heat source of the carbon dioxide evaporator 2 . The fresh water steam and the concentrated brine gradually flow into the second effect seawater distiller 6 to heat the lower pressure seawater, and finally the fresh water steam of the first effect seawater distiller 5 and the second effect seawater distiller 6 is obtained in the condenser 9 Liquefaction, and the concentrated brine is discharged from the bottom of the second effect seawater distiller 6 and mixed with the new seawater of the second branch at the mixing valve V3.

Referring to FIG. 1 , when the solar energy is sufficient but the electric energy is insufficient, the heat release and heat pump desalination mode is activated. At this time, the main circuit valve V7 of the solar collector 10 is closed, and the bypass valve V8 thereof is opened. The high-temperature molten salt in the high-temperature molten salt storage tank 15 flows into the molten salt heat exchange side of the molten salt-conducting oil heat exchanger 13, and after the heat-conducting oil in the heat-conducting oil circulation circuit is heated and the temperature is lowered, the low-temperature molten salt is introduced Tank 14. At this time, the working process of the carbon dioxide heat pump circulation unit and the seawater desalination unit is the same as that in the heat storage and heat pump desalination modes.

Referring to Figure 1, when the solar energy is sufficient, the heat storage and flash desalination mode is activated, and the working process of the solar heat collection and heat storage unit at this time is the same as that in the heat storage and heat pump desalination mode. At this time, the carbon dioxide heat pump circulation unit stops working, and the new seawater flows into the low temperature side of the condenser 9 under the action of the seawater diversion three-way regulating valve V4, and then flows into the heat transfer oil-seawater heat exchanger 12 after the condensate is preheated. Low temperature side, heated to flash temperature. The throttle valve V1 is closed, the pressure of the seawater is reduced to the flashing pressure under the action of the throttle valve V2, and the flashing is completed in the second effect seawater distiller 6. The flashed steam flows into the high temperature side of the condenser 9 and is condensed, the concentrated brine produced in the second effect seawater distiller 6 is directly discharged through the valve V9, and the mixing valve V3 is closed.

Referring to FIG. 1 , when the solar energy is insufficient and the electric energy is also insufficient, the exothermic and flash desalination modes are activated. At this time, the main circuit valve V7 of the solar collector 10 is closed, and the bypass valve V8 thereof is opened. The high-temperature molten salt in the high-temperature molten salt storage tank 15 flows into the molten salt heat exchange side of the molten salt-conducting oil heat exchanger 13, heats the heat-conducting oil in the heat-conducting oil circulation circuit to reduce the temperature, and then flows into the low-temperature molten salt storage tank 14. At this time, the working process of the seawater desalination unit is the same as that in the heat storage and flash desalination modes.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the present invention. within.

Claims (10)

1. A seawater source trans-critical carbon dioxide heat pump circulation multi-effect seawater desalination system comprises a solar heat collection and storage unit, a trans-critical carbon dioxide heat pump unit and a seawater desalination unit, and is characterized in that,

-the solar heat collection and storage unit comprises at least a solar heat collector, a high temperature side of a heat transfer oil-carbon dioxide heat exchanger, and a heat transfer oil heat exchange side of a molten salt-heat transfer oil heat exchanger, wherein,

the solar heat collector, the high-temperature side of the heat conducting oil-carbon dioxide heat exchanger and the heat conducting oil heat exchanging side of the molten salt-heat conducting oil heat exchanger are sequentially communicated through a pipeline to form a closed heat conducting oil circulation loop;

a bypass pipeline is arranged between an inlet and an outlet of the solar heat collector, a bypass valve is arranged on the bypass pipeline, and a main path valve is arranged at the inlet of the solar heat collector;

one end opening of a fused salt heat exchange side of the fused salt-heat conducting oil heat exchanger is communicated with a low-temperature fused salt storage tank through a pipeline, and the other end opening of the fused salt-heat conducting oil heat exchanger is communicated with a high-temperature fused salt storage tank through a pipeline;

the transcritical carbon dioxide heat pump unit at least comprises a cold side of a carbon dioxide evaporator, a carbon dioxide compressor unit, a carbon dioxide expansion unit and a heating pipeline in the first-effect seawater distiller, wherein the cold side of the carbon dioxide evaporator, the carbon dioxide compressor unit, the heating pipeline in the first-effect seawater distiller and the carbon dioxide expansion unit are sequentially communicated through pipelines to form a closed carbon dioxide circulation loop;

the seawater desalination unit at least comprises a first effect seawater distiller, a second effect seawater distiller, a condenser, a low-temperature side of a heat transfer oil-carbon dioxide heat exchanger, a seawater shunt three-way regulating valve and a seawater and brine three-way mixing valve, wherein,

the inlet of the seawater shunt three-way regulating valve is formed into a fresh seawater inlet which is not desalted, the first outlet of the seawater shunt three-way regulating valve sequentially passes through the low-temperature side of the condenser and the low-temperature side of the heat conduction oil-carbon dioxide heat exchanger through pipelines and then is respectively communicated with the fresh seawater inlets at the tops of the first effect seawater distiller and the second effect seawater distiller, and pressure regulating valves are respectively arranged on the fresh seawater inlet pipelines at the tops of the first effect seawater distiller and the second effect seawater distiller;

the top or the position close to the top of the first-effect seawater distiller and the second-effect seawater distiller is provided with a fresh water steam outlet, the bottom of the first-effect seawater distiller is provided with a strong brine outlet, the fresh water steam outlet of the first-effect seawater distiller is communicated with the inlet of a heating pipeline arranged in the second-effect seawater distiller through a pipeline, the outlet of the heating pipeline in the second-effect seawater distiller and the fresh water steam outlet of the second-effect seawater distiller are respectively communicated with the high-temperature side inlet of the condenser through pipelines, and the high-temperature side outlet of the condenser is formed as a desalted water outlet; the strong brine outlet of the first effect seawater distiller is led in through a pipeline in the second effect seawater distiller, the strong brine outlet of the second effect seawater distiller is divided into two branches, wherein the strong brine is directly discharged through the first branch, a regulating valve is arranged on the first branch, the second branch is communicated with the first inlet of the seawater brine tee-joint mixing valve, the second inlet of the seawater brine tee-joint mixing valve is communicated with the second outlet of the seawater shunting tee-joint regulating valve through a pipeline, the outlet of the seawater brine tee-joint mixing valve is communicated with the hot side inlet of the carbon dioxide evaporator through a pipeline, and the hot side outlet of the carbon dioxide evaporator is formed into a seawater outlet.

2. The seawater source trans-critical carbon dioxide heat pump cycle multi-effect seawater desalination system of the above claims, wherein in the trans-critical carbon dioxide heat pump unit, the carbon dioxide expansion unit expands the introduced carbon dioxide to a subcritical state, the subcritical carbon dioxide is introduced to the cold side of the carbon dioxide evaporator to absorb heat, and the supercritical state is achieved after the subcritical carbon dioxide is compressed by the compressor unit.

3. The seawater source trans-critical carbon dioxide heat pump cycle multi-effect seawater desalination system of the above claims, wherein the solar heat collection and storage unit further comprises a heat conduction oil pump, and the heat conduction oil pump is arranged on the heat conduction oil circulation loop and used for driving the heat conduction oil in the circulation loop to circularly flow among all the components.

4. The seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the above claims, wherein the heat transfer oil pump is arranged on the inlet pipeline and/or the outlet pipeline of the solar heat collector.

5. The seawater source trans-critical carbon dioxide heat pump cycle multi-effect seawater desalination system of the preceding claims, wherein an expansion tank is further arranged in the heat transfer oil circulation loop, and the expansion tank is used for adapting to volume increase caused by heating of heat transfer oil and supplementing when the heat transfer oil is insufficient.

6. The seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the above claims, wherein the expansion tank is arranged on a communicating pipe between the solar heat collector and the high temperature side of the heat transfer oil-carbon dioxide heat exchanger.

7. The seawater source trans-critical carbon dioxide heat pump cycle multi-effect seawater desalination system of the preceding claims, wherein the expansion tank is further provided with a heat conduction oil supply pipeline with a valve and a heat conduction oil discharge pipeline with a valve, and when heat conduction oil needs to be replaced, the valve on the heat conduction oil discharge pipeline is opened to discharge old heat conduction oil; and opening a valve on the heat-conducting oil supply pipeline when heat-conducting oil needs to be added.

8. The seawater source trans-critical carbon dioxide heat pump cycle multi-effect seawater desalination system of the preceding claims, wherein the temperature of fresh seawater sequentially passes through the condenser and the heat transfer oil-carbon dioxide heat exchanger, then rises, and enters the first-effect seawater distiller and the second-effect seawater distiller for fractional desalination, wherein the working pressure in the first-effect seawater distiller is higher than that in the second-effect seawater distiller.

9. The seawater source transcritical carbon dioxide heat pump cycle multi-effect seawater desalination system of the above claims, wherein the concentrated brine discharged from the second effect seawater distiller and the fresh seawater branched by the seawater branched three-way regulating valve are mixed in a certain proportion in the seawater branched three-way mixing valve to be used as the heat source of the carbon dioxide evaporator, so that the average heat absorption temperature of the carbon dioxide heat pump unit is increased.

10. The seawater source transcritical carbon dioxide heat pump cycle multiple-effect seawater desalination system as claimed in the above claims, wherein the seawater desalination unit further comprises a seawater drain pump, a concentrated brine pump and a desalination water pump, wherein the seawater drain pump is disposed on the seawater discharge pipeline of the carbon dioxide evaporator, the concentrated brine pump is disposed on the concentrated brine outlet pipeline of the second-effect seawater distiller, and the desalination water pump is disposed on the high temperature side outlet pipeline of the condenser.

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