Solar heat supply plastic liquefaction-gasification two-step hydrogen-electricity co-production system and method

Abstract

The invention relates to the technical field of waste plastic harmless treatment, and discloses a solar heat supply plastic liquefaction-gasification two-step hydrogen-electricity co-production system and method.The system comprises a solar fused salt heat storage system, a liquefaction reactor, a gasification reactor, an organic Rankine cycle power generation device, a gasification reaction system and a hydrogen separator; the input end of the gasification reactor is provided with branches, the input end of one branch is connected with the output end of the liquefaction reactor, and the input end of the other branch is connected with the input end of the solar fused salt heat storage system; the input end of the solar fused salt heat storage system is used for inputting liquid H2O; the input end of the gasification reaction system is provided with branches, the input end of one branch is connected with the output end of the gasification reactor, and the input end of the other branch is used for inputting supercritical H2O; efficient conversion from waste plastic to high-value hydrogen-rich synthesis gas is achieved, meanwhile, input of high-grade electric energy of the system can be effectively reduced through the solar photo-thermal fused salt energy storage technology, and the economical efficiency of the system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of harmless treatment of waste plastics, and in particular to a solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system and method. Background Art

[0002] Due to the good waterproof and corrosion-resistant properties of plastics, it takes decades or even hundreds of years for waste plastics abandoned in the natural environment to be completely degraded. These difficult-to-degrade waste plastics will be eaten by terrestrial animals such as birds, or enter rivers, lakes, urban groundwater networks, etc. and be eaten by aquatic animals, which not only causes serious environmental pollution, but also threatens human life through the food chain. Therefore, the development of clean and efficient waste plastic resource disposal technology is of great significance to winning the battle against plastic environmental pollution.

[0003] The current disposal methods of waste plastics mainly include landfill, incineration, sorting and reshaping, and thermochemical conversion. Among them, thermochemical conversion has become a hot topic in the research of waste plastic recycling technology in recent years due to its advantages of environmental friendliness, low fly ash rate, and high conversion efficiency. Subcritical water liquefaction and supercritical water gasification technology are two promising organic waste thermochemical conversion technologies developed in recent years. The former uses the fact that the ion product of water near the critical point (374℃, 22.1 MPa) is much higher than that of normal water, which can act as an acid-base catalyst, thereby effectively promoting the depolymerization and hydrolysis reactions of organic components, and can convert organic matter into liquid oil products without drying; while the latter uses the good physical and chemical properties of water above the critical point, such as high diffusivity, high reactivity, and high solubility, to form a homogeneous reaction system in a supercritical water environment, converting organic matter into high value-added synthesis gas.

[0004] However, for plastics, on the one hand, the existing subcritical water liquefaction technology generally has the problem that the liquefied oil product quality is not high, and it still needs to undergo complex and energy-intensive post-processing processes such as extraction and distillation to obtain bio-oil that meets the requirements, which reduces the technical and economic benefits; on the other hand, due to the high viscosity and low thermal conductivity of plastics after being heated and melted, the formation of a supercritical water gasification homogeneous reaction system is inhibited, and plastics are all polymers with a slow depolymerization rate, resulting in the common problems of low carbon gasification rate and easy coking in supercritical water direct gasification of plastics.

[0005] On the other hand, both the subcritical H2O liquefaction reaction process and the supercritical H2O gasification reaction process require a lot of additional heat input, mainly referring to the need to heat the liquid H2O at room temperature and high pressure to the subcritical or supercritical state. Currently, electric heating is usually used, which inevitably leads to the consumption of a large amount of high-quality electricity. Therefore, it is of great significance to explore how to use low-grade thermal energy instead of high-grade electrical energy to achieve efficient resource recovery of waste plastics. Summary of the invention

[0006] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system and method to solve the technical problems of high waste plastic treatment costs and poor liquefaction or gasification effects when subcritical water liquefaction or supercritical water gasification technology is used alone in the prior art.

[0007] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system, comprising a solar molten salt heat storage system, a liquefaction reactor, a gasification reactor, an organic Rankine cycle power generation device, a gasification reaction system, and a hydrogen separator; The input end of the gasification reactor is provided with a branch line, wherein the input end of one branch line is connected to the output end of the liquefaction reactor, and the input end of the other branch line is connected to the input end of the solar molten salt thermal storage system; The input end of the solar molten salt thermal storage system is used to input liquid H2O; The input end of the gasification reaction system is provided with branched roads, wherein the input end of one branch is connected to the output end of the gasification reactor, and the input end of the other branch is used to input supercritical H2O; The output end of the gasification reaction system is divided into three branches, wherein the output end of one branch is connected to the input end of the liquefaction reactor, the output end of one branch is connected to the input end of the organic Rankine cycle power generation device, and the output end of one branch is connected to the input end of the hydrogen separator.

[0008] Preferably, the solar molten salt heat storage system comprises a tower collector, a hot molten salt storage tank, a first heat exchanger and a cold molten salt storage tank; The outlet of the tower collector is connected to the input end of the hot molten salt storage tank, the output port of the hot molten salt storage tank is connected to the hot side working medium inlet of the first heat exchanger, the hot side working medium outlet of the first heat exchanger is connected to the inlet of the cold molten salt storage tank; the outlet of the cold molten salt storage tank is connected to the inlet of the tower collector; The cold side working medium outlet of the first heat exchanger is connected to a branch input end of the gasification reactor; the cold side working medium inlet of the first heat exchanger is used to input liquid H2O.

[0009] Furthermore, a first ball valve and a first molten salt pump are provided in sequence between the output port of the hot molten salt storage tank and the hot side working medium inlet of the first heat exchanger.

[0010] Furthermore, a second molten salt pump and a second ball valve are provided in sequence between the hot side working medium outlet of the first heat exchanger and the inlet of the cold molten salt storage tank.

[0011] Preferably, the liquefaction reactor is also provided with a branch input end for inputting waste plastic slurry.

[0012] Preferably, the gasification reaction system comprises a second heat exchanger, a cooler, and a gas-liquid separator; The hot side working medium inlet of the second heat exchanger is connected to the output end of the gasification reactor, and the hot side working medium outlet of the second heat exchanger is connected to the hot side working medium inlet of the cooler; the hot side working medium outlet of the cooler is connected to the inlet of the gas-liquid separator; The cold side working medium inlet of the second heat exchanger is used to input liquid H2O, and the cold side working medium outlet of the second heat exchanger is connected to the input end of the liquefaction reactor; The inlet of the cooler is used to input the liquid organic working medium; the outlet of the cooler is connected to the input end of the organic Rankine cycle power generation device, and the output end of the organic Rankine cycle power generation device is used to output the liquid organic working medium; The outlet branch of the gas-liquid separator is arranged, one outlet of the branch is connected to the hydrogen separator, and the other outlet of the branch is used to output liquid H2O.

[0013] Furthermore, a back pressure valve is provided between the hot side working medium outlet of the cooler and the inlet of the gas-liquid separator.

[0014] In a second aspect, the present invention provides a two-step hydrogen-electricity cogeneration method for plastic liquefaction-gasification using solar heating, based on the above-mentioned two-step hydrogen-electricity cogeneration system for plastic liquefaction-gasification using solar heating, comprising the following process: Start the solar molten salt heat storage system to convert liquid H2O into supercritical H2O before entering the gasification reactor; The gasification reaction system is started, and the liquid H2O is preheated by the gasification reaction system to become subcritical H2O and enter the liquefaction reactor, and undergoes a liquefaction reaction with subcritical water in the liquefaction reactor to generate liquid oil organic matter; In the gasification reactor, supercritical H2O reacts with the liquid phase oil organic matter coming from the outlet of the liquefaction reactor to produce supercritical water gasification reaction, and the gasification reaction products obtained are H2, CO, CH4 and CO2, as well as unreacted H2O; The gasification reaction product flow at the outlet of the gasification reactor enters the gasification reaction system for the first heat release, and transfers the heat to the liquid H2O; the gasification reaction flow after the first heat release undergoes a second heat release and cooling in the gasification reaction system, and transfers the heat to the liquid organic working fluid, and uses the medium and low temperature waste heat to perform Rankine cycle power generation through an organic Rankine cycle power generation device; the gasification reaction flow after the two heat releases is depressurized and then subjected to gas-liquid separation to obtain a gas-phase mixed product with the components of H2, CO, CH4 and CO2 and a liquid-phase product H2O; the gas-phase product passes through a hydrogen separator to produce pure H2 and by-products of CO, CH4 and CO2.

[0015] Preferably, the liquefaction reaction temperature in the liquefaction reactor is 250-400° C., and the pressure is 23-28 MPa; the gasification reaction temperature in the gasification reactor is 500-650° C., and the pressure is 23-28 MPa.

[0016] Preferably, the melting point of the molten salt material used in the solar molten salt thermal storage system is less than 400°C, and the decomposition temperature is greater than 680°C, and the boiling point of the organic working fluid used in the organic Rankine cycle in the organic Rankine cycle power generation device is less than 20°C.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system with solar heating. By adopting the design of a solar molten salt heat storage system, a liquefaction reactor, a gasification reactor, a gasification reaction system, an organic Rankine cycle power generation system and a hydrogen separation system, and utilizing the synergistic technology of subcritical water liquefaction and supercritical water gasification, the system overcomes the technical problems of low liquefied oil quality and high post-processing cost in the traditional waste plastic subcritical water liquefaction oil production technology, as well as slow depolymerization rate and easy coking in the process of direct supercritical water gasification of waste plastics to produce synthesis gas, thereby achieving efficient conversion from waste plastics to high-value hydrogen-rich synthesis gas; at the same time, the solar thermal molten salt energy storage technology can effectively reduce the input of high-grade electric energy in the system and improve the economy of the system; in addition, the organic Rankine cycle power generation device can achieve more efficient and full recycling of lower temperature heat sources.

[0018] Furthermore, the solar molten salt heat storage system includes a tower collector, a hot molten salt storage tank, a first heat exchanger and a cold molten salt storage tank; the outlet of the tower collector is connected to the input end of the hot molten salt storage tank, the output port of the hot molten salt storage tank is connected to the hot side working fluid inlet of the first heat exchanger, and the hot side working fluid outlet of the first heat exchanger is connected to the inlet of the cold molten salt storage tank; the outlet of the cold molten salt storage tank is connected to the inlet of the tower collector; the cold side working fluid outlet of the first heat exchanger is connected to the branch input end of the gasification reactor; the cold side working fluid inlet of the first heat exchanger is used to input liquid H2O; the tower collector can effectively collect and convert solar energy. By focusing sunlight, a large amount of solar energy is converted into thermal energy and transferred to the molten salt in the hot molten salt storage tank. The hot molten salt storage tank can realize long-term storage and stable release of thermal energy, thereby improving the reliability and utilization rate of solar energy. As a key device for heat energy transfer, the first heat exchanger realizes efficient heat energy conversion through heat exchange between the hot side working fluid and the cold side working fluid.

[0019] Furthermore, a first ball valve and a first molten salt pump are provided in sequence between the output port of the hot molten salt storage tank and the hot side working fluid inlet of the first heat exchanger, and a second molten salt pump and a second ball valve are provided in sequence between the hot side working fluid outlet of the first heat exchanger and the inlet of the cold molten salt storage tank; the setting of the first ball valve and the second ball valve enables the system to accurately control the flow path of the molten salt. When necessary, the corresponding ball valve can be opened to allow the molten salt to flow into or out of the heat exchanger; when not needed, the ball valve can be closed to prevent the molten salt from continuing to flow, thereby achieving precise control of the operation of the system; the first molten salt pump and the second molten salt pump serve as power sources to ensure that the molten salt flows stably and continuously in the pipeline. By adjusting the speed and flow rate of the molten salt pump, the molten salt delivery speed can be accurately controlled to meet the needs of the system under different working conditions. At the same time, the setting of the two molten salt pumps also facilitates the switching of molten salt between the hot molten salt storage tank and the cold molten salt storage tank, improving the flexibility and adaptability of the system.

[0020] Furthermore, the gasification reaction system includes a second heat exchanger, a cooler, and a gas-liquid separator; the hot side working medium inlet of the second heat exchanger is connected to the output end of the gasification reactor, and the hot side working medium outlet of the second heat exchanger is connected to the hot side working medium inlet of the cooler; the hot side working medium outlet of the cooler is connected to the inlet of the gas-liquid separator; the cold side working medium inlet of the second heat exchanger is used to input liquid H2O, and the cold side working medium outlet of the second heat exchanger is connected to the input end of the liquefaction reactor; the inlet of the cooler is used to input liquid organic working medium; the outlet of the cooler is connected to the input end of the organic Rankine cycle power generation device, and the output end of the organic Rankine cycle power generation device is used to output liquid organic working medium; the outlet branch of the gas-liquid separator is set, one branch outlet is connected to the hydrogen separator, and the other branch outlet is used to output liquid H2O; by graded utilization of the thermal energy of the reaction products at the outlet of the gasification reactor, the system can effectively extract energy in different temperature ranges, reduce energy waste, and improve the overall energy conversion efficiency of the system.

[0021] The present invention also provides a two-step hydrogen-electricity cogeneration method of plastic liquefaction-gasification with solar heating, which effectively overcomes the shortcomings of the current waste plastics single subcritical water liquefaction or supercritical water gasification technology, adopts the subcritical water / supercritical water liquefaction-gasification two-step treatment idea, and the mixed plastics are first decomposed and liquefied into liquid products by subcritical water, and then gasified by supercritical water to generate high-value synthesis gas. The two-step technical route can reduce the requirements for the oil products of plastic liquefaction products while using liquid organic matter to form a homogeneous reaction system in supercritical water, overcome the shortcomings of plastic direct supercritical water gasification, such as slow depolymerization rate and difficulty in forming a homogeneous reaction system, which leads to easy coking, and open up a new path for plastic resource utilization.

[0022] Furthermore, through the solar molten salt thermal storage system, solar energy is converted into thermal energy and stored in molten salt, realizing efficient conversion and storage of solar energy. Not only does it improve the utilization rate of solar energy, but it also enables the system to continue to operate during periods without sunlight, ensuring the continuity of energy supply. Liquid H2O undergoes two heat release processes in the gasification reaction system, transferring heat to liquid H2O and liquid organic working fluid respectively. This cascade utilization of thermal energy improves the utilization efficiency of thermal energy and reduces energy waste. This method combines renewable / waste resources such as solar energy and plastics, and realizes the conversion and storage of chemical energy through the sub- / supercritical water liquefaction-gasification process. This not only reduces dependence on fossil energy, but also promotes the integrated utilization of renewable energy and chemical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of a plastic sub- / supercritical water liquefaction-gasification hydrogen-electricity cogeneration system using solar energy for heating in an embodiment of the present invention; In the figure: 1. Tower collector; 2. Hot molten salt storage tank; 3. First ball valve; 4. First molten salt pump; 5. First heat exchanger; 6. Second molten salt pump; 7. Second ball valve; 8. Cold molten salt storage tank; 9. Liquefaction reactor; 10. Gasification reactor; 11. Second heat exchanger; 12. Cooler; 13. Organic Rankine cycle power generation device; 14. Back pressure valve; 15. Gas-liquid separator; 16. Hydrogen separator. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] The purpose of the present invention is to provide a solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system and method, which adopts a subcritical / supercritical water liquefaction-gasification two-step treatment idea: mixed plastics are first decomposed and liquefied into liquid products by subcritical water, and then gasified by supercritical water to generate high-value synthesis gas, so as to solve the technical problems of high waste plastic treatment cost and poor liquefaction or gasification effect when subcritical water liquefaction or supercritical water gasification technology is used alone in the prior art.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings: Example 1 See also Figure 1In one embodiment of the present invention, a two-step hydrogen-electricity cogeneration system of plastic liquefaction-gasification with solar heating is provided, comprising a solar molten salt heat storage system, a liquefaction reactor 9, a gasification reactor 10, an organic Rankine cycle power generation device 13, a gasification reaction system and a hydrogen separator 16; a branch road is set at the input end of the gasification reactor 10, wherein the input end of one branch road is connected to the output end of the liquefaction reactor 9, and the input end of another branch road is connected to the input end of the solar molten salt heat storage system; the input end of the solar molten salt heat storage system is used to input liquid H2O; a branch road is set at the input end of the gasification reaction system, wherein the input end of one branch road is connected to the output end of the gasification reactor 10, and the input end of another branch road is used to input supercritical H2O; the output end of the gasification reaction system is divided into three branches, wherein the output end of one branch road is connected to the input end of the liquefaction reactor 9, the output end of one branch road is connected to the input end of the organic Rankine cycle power generation device 13, and the output end of one branch road is connected to the input end of the hydrogen separator 16.

[0027] Specifically, the solar molten salt heat storage system includes a tower collector 1, a hot molten salt storage tank 2, a first heat exchanger 5 and a cold molten salt storage tank 8; the outlet of the tower collector 1 is connected to the input end of the hot molten salt storage tank 2, the output port of the hot molten salt storage tank 2 is connected to the hot side working fluid inlet of the first heat exchanger 5, and the hot side working fluid outlet of the first heat exchanger 5 is connected to the inlet of the cold molten salt storage tank 8; the outlet of the cold molten salt storage tank 8 is connected to the inlet of the tower collector 1; the cold side working fluid outlet of the first heat exchanger 5 is connected to a branch input end of the gasification reactor 10; the cold side working fluid inlet of the first heat exchanger 5 is used to input liquid H2O.

[0028] Among them, a first ball valve 3 and a first molten salt pump 4 are sequentially arranged between the output port of the hot molten salt storage tank 2 and the hot side working medium inlet of the first heat exchanger 5 .

[0029] Among them, a second molten salt pump 6 and a second ball valve 7 are arranged in sequence between the hot side working medium outlet of the first heat exchanger 5 and the inlet of the cold molten salt storage tank 8.

[0030] The structural principle in this embodiment is as follows: The tower collector 1 is the heat collection part of the system. The tower collector 1 focuses sunlight into a small area to generate a high-temperature heat source, which is used to heat the molten salt flowing through its outlet.

[0031] The hot molten salt storage tank 2 is used to store the high-temperature molten salt heated by the tower collector 1. Molten salt is a good heat storage medium that can stably store heat at high temperatures.

[0032] The first heat exchanger 5 is used to transfer the heat in the hot molten salt to the liquid H2O, so that the liquid H2O is converted into water vapor or other desired states after being heated.

[0033] The cold molten salt storage tank 8 stores the low-temperature molten salt after releasing heat through the first heat exchanger 5. The molten salt will be sent to the tower collector 1 again for heating to form a cycle.

[0034] The sunlight is captured and focused by the tower collector 1, generating a high-temperature heat source. The high-temperature heat source heats the molten salt flowing through the tower collector 1, raising its temperature. The heated molten salt is sent to the hot molten salt storage tank 2 for storage. When the stored heat is needed, the high-temperature molten salt flows out of the hot molten salt storage tank 2, and enters the hot side of the first heat exchanger 5 after being regulated by the first ball valve 3 and the first molten salt pump 4. In the first heat exchanger 5, the high-temperature molten salt transfers heat to liquid H2O. After being heated, the liquid H2O is converted into water vapor or enters other required states, providing raw materials for subsequent gasification reactions. After releasing heat, the temperature of the molten salt decreases, and after being regulated by the second molten salt pump 6 and the second ball valve 7, it enters the cold molten salt storage tank 8 for storage.

[0035] Specifically, the liquefaction reactor 9 is also provided with a branch input end for inputting waste plastic slurry.

[0036] Specifically, the gasification reaction system includes a second heat exchanger 11, a cooler 12, and a gas-liquid separator 15; the hot side working medium inlet of the second heat exchanger 11 is connected to the output end of the gasification reactor 10, and the hot side working medium outlet of the second heat exchanger 11 is connected to the hot side working medium inlet of the cooler 12; the hot side working medium outlet of the cooler 12 is connected to the inlet of the gas-liquid separator 15; the cold side working medium inlet of the second heat exchanger 11 is used to input liquid H2O, and the cold side working medium outlet of the second heat exchanger 11 is connected to the input end of the liquefaction reactor 9; the inlet of the cooler 12 is used to input liquid organic working medium; the outlet of the cooler 12 is connected to the input end of the organic Rankine cycle power generation device 13, and the output end of the organic Rankine cycle power generation device 13 is used to output liquid organic working medium; the outlet branch of the gas-liquid separator 15 is set, one branch outlet is connected to the hydrogen separator 16, and the other branch outlet is used to output liquid H2O.

[0037] A back pressure valve 14 is provided between the hot side working medium outlet of the cooler 12 and the inlet of the gas-liquid separator 15 .

[0038] The structural principle in this embodiment is as follows: The gasification reactor 10 is used to perform a gasification reaction on the input fuel under high temperature and high pressure conditions to generate a synthesis gas containing components such as H2, CO, CH4, CO2 and unreacted H2O.

[0039] The second heat exchanger 11 is used as a heat exchange device to transfer the heat in the high-temperature synthesis gas output by the gasification reactor 10 to the input liquid H2O. The liquid H2O is preheated and converted into subcritical water, and enters the liquefaction reactor 9 for subsequent reactions. At the same time, the temperature of the synthesis gas is reduced to prepare for subsequent cooling and separation.

[0040] The cooler 12 further cools the synthesis gas coming out of the second heat exchanger 11 to reduce its temperature to a range suitable for gas-liquid separation. During the cooling process, some components in the synthesis gas may condense into liquid.

[0041] The gas-liquid separator 15 separates the cooled synthesis gas into gas and liquid to obtain gas phase and liquid phase products. The gas phase mainly contains gases such as H2, CO, CH4, CO2, etc., and the liquid phase mainly contains incompletely reacted H2O and other possible liquid products.

[0042] In summary, the present embodiment provides a solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system, which adopts a solar molten salt heat storage system, a subcritical H2O liquefaction system, a supercritical H2O gasification system, an organic Rankine cycle power generation system and an H2 separation system. On the one hand, by utilizing the synergistic technology of subcritical water liquefaction and supercritical water gasification, it overcomes the shortcomings of low liquefied oil quality and high post-processing cost in the traditional waste plastic subcritical water liquefaction oil production technology, as well as slow depolymerization rate and easy coking in the process of direct supercritical water gasification of waste plastics to produce synthesis gas, thereby realizing efficient conversion from waste plastics to high-value hydrogen-rich synthesis gas; on the other hand, the solar thermal molten salt energy storage technology can effectively reduce the input of high-grade electricity in the system and improve the economy of the system; in addition, the organic Rankine cycle power generation device 13 can also realize more efficient and full recycling of lower temperature heat sources.

[0043] Example 2 according to Figure 1 As shown, the present invention also provides a two-step hydrogen-electricity cogeneration method for plastic liquefaction-gasification using solar energy heating. Based on the above-mentioned two-step hydrogen-electricity cogeneration system for plastic liquefaction-gasification using solar energy heating, the method includes the following process: 1) Start the solar molten salt heat storage system, and heat the liquid H2O at room temperature and high pressure through the first heat exchanger 5 to a supercritical state and then enter the gasification reactor 10; 2) Start the second heat exchanger 11, and the liquid H2O at room temperature and high pressure is heated by the second heat exchanger 11 to become subcritical H2O and enter the liquefaction reactor 9, and undergoes a subcritical water liquefaction reaction with the waste plastic slurry to generate liquid oil organic matter; 3) In the gasification reactor 10, supercritical H2O reacts with the oil organic matter from the outlet of the liquefaction reactor 9 to produce a supercritical water gasification reaction, and the gasification reaction products obtained are H2, CO, CH4 and CO2, as well as unreacted H2O; 4) The gasification reaction product flow at the outlet of the gasification reactor 10 first enters the second heat exchanger 11 for the first heat release, and transfers the heat to the liquid H2O at room temperature and high pressure; the gasification reaction flow after the first heat release is further cooled by the cooler 12, and the heat is transferred to the organic working fluid, and the medium and low temperature waste heat is used to perform Rankine cycle power generation through the organic Rankine cycle power generation device 13; the gasification reaction flow after the two heat releases is depressurized by the back pressure valve 14, and then separated into gas and liquid by the gas-liquid separator 15 to obtain a gas phase mixed product with the components of H2, CO, CH4 and CO2 and a liquid phase product H2O; the gas phase product passes through the hydrogen separator 16 to produce pure H2 and by-products (CO, CH4 and CO2).

[0044] The liquefaction reaction temperature in the liquefaction reactor 9 is 250-400° C., and the pressure is 23-28 MPa; the gasification reaction temperature in the gasification reactor 10 is 500-650° C., and the pressure is 23-28 MPa.

[0045] Among them, the melting point temperature of the molten salt material used in the solar molten salt thermal storage system is less than 400°C, and the decomposition temperature is greater than 680°C, and the boiling point temperature of the organic working fluid used in the organic Rankine cycle in the organic Rankine cycle power generation device 13 is less than 20°C.

[0046] In summary, the two-step hydrogen-electricity cogeneration method of plastic liquefaction-gasification with solar heating provided in this embodiment converts solar energy into thermal energy and stores it in molten salt through a solar molten salt thermal storage system, thereby realizing efficient conversion and storage of solar energy. It not only improves the utilization rate of solar energy, but also enables the system to continue to operate during the period without sunlight, ensuring the continuity of energy supply. Liquid H2O undergoes two heat release processes in the gasification reaction system, and transfers heat to liquid H2O and liquid organic working fluid respectively. This cascade utilization method of thermal energy improves the utilization efficiency of thermal energy and reduces energy waste. This method combines renewable / waste resources such as solar energy and plastics, and realizes the conversion and storage of chemical energy through the sub- / supercritical water liquefaction-gasification process. This not only reduces dependence on fossil energy, but also promotes the integrated utilization of renewable energy and chemical energy.

[0047] In addition to outputting high-grade electric energy, the present invention can also obtain high-value-added synthesis gas fuel by-product, which can be used in industrial scenarios such as combustion heating and chemical raw materials.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system, characterized in that: It comprises a solar molten salt heat storage system, a liquefaction reactor (9), a gasification reactor (10), an organic Rankine cycle power generation device (13), a gasification reaction system and a hydrogen separator (16); The input end of the gasification reactor (10) is provided with a branch line, wherein the input end of one branch line is connected to the output end of the liquefaction reactor (9), and the input end of the other branch line is connected to the input end of the solar molten salt heat storage system; The input end of the solar molten salt thermal storage system is used to input liquid H2O; The gasification reaction system is provided with a branch line at the input end, wherein the input end of one branch line is connected to the output end of the gasification reactor (10), and the input end of the other branch line is used to input supercritical H2O; The output end of the gasification reaction system is divided into three branches, wherein the output end of one branch is connected to the input end of the liquefaction reactor (9), the output end of one branch is connected to the input end of the organic Rankine cycle power generation device (13), and the output end of one branch is connected to the input end of the hydrogen separator (16).

2. A solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 1, characterized in that: The solar molten salt heat storage system comprises a tower collector (1), a hot molten salt storage tank (2), a first heat exchanger (5) and a cold molten salt storage tank (8); The outlet of the tower collector (1) is connected to the input end of the hot molten salt storage tank (2), the output port of the hot molten salt storage tank (2) is connected to the hot side working medium inlet of the first heat exchanger (5), the hot side working medium outlet of the first heat exchanger (5) is connected to the inlet of the cold molten salt storage tank (8); the outlet of the cold molten salt storage tank (8) is connected to the inlet of the tower collector (1); The cold side working medium outlet of the first heat exchanger (5) is connected to a branch input end of the gasification reactor (10); and the cold side working medium inlet of the first heat exchanger (5) is used to input liquid H2O.

3. A solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 2, characterized in that: A first ball valve (3) and a first molten salt pump (4) are provided in sequence between the output port of the hot molten salt storage tank (2) and the hot side working medium inlet of the first heat exchanger (5).

4. A solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 2, characterized in that: A second molten salt pump (6) and a second ball valve (7) are provided in sequence between the hot side working medium outlet of the first heat exchanger (5) and the inlet of the cold molten salt storage tank (8).

5. The solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 1, characterized in that: The liquefaction reactor (9) is also provided with a branch input end for inputting waste plastic slurry.

6. The solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 1, characterized in that: The gasification reaction system comprises a second heat exchanger (11), a cooler (12), and a gas-liquid separator (15); The hot side working medium inlet of the second heat exchanger (11) is connected to the output end of the gasification reactor (10), and the hot side working medium outlet of the second heat exchanger (11) is connected to the hot side working medium inlet of the cooler (12); the hot side working medium outlet of the cooler (12) is connected to the inlet of the gas-liquid separator (15); The cold side working medium inlet of the second heat exchanger (11) is used to input liquid H2O, and the cold side working medium outlet of the second heat exchanger (11) is connected to the input end of the liquefaction reactor (9); The inlet of the cooler (12) is used to input a liquid-phase organic working medium; the outlet of the cooler (12) is connected to the input end of an organic Rankine cycle power generation device (13); and the output end of the organic Rankine cycle power generation device (13) is used to output the liquid-phase organic working medium; The gas-liquid separator (15) is provided with an outlet branch, wherein one outlet is connected to the hydrogen separator (16), and the other outlet is used to output liquid H2O.

7. A solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration system according to claim 6, characterized in that: A back pressure valve (14) is provided between the hot side working medium outlet of the cooler (12) and the inlet of the gas-liquid separator (15).

8. A two-step hydrogen-electricity cogeneration method of plastic liquefaction-gasification using solar heating, characterized in that: A two-step hydrogen-electricity cogeneration system for plastic liquefaction and gasification using solar energy heating according to any one of claims 1 to 7, comprising the following process: The solar molten salt heat storage system is started to convert liquid H2O into supercritical H2O and then enter the gasification reactor (10); The gasification reaction system is started, and the liquid H2O is preheated by the gasification reaction system to become subcritical H2O and enter the liquefaction reactor (9), and undergoes a liquefaction reaction with subcritical water in the liquefaction reactor (9) to generate liquid oil organic matter; In the gasification reactor (10), supercritical H2O and the liquid phase oil organic matter from the outlet of the liquefaction reactor (9) undergo a supercritical water gasification reaction, and the obtained gasification reaction products are H2, CO, CH4 and CO2, as well as unreacted H2O; The gasification reaction product flow at the outlet of the gasification reactor (10) enters the gasification reaction system for the first heat release and transfers the heat to the liquid H2O; After the first heat release, the gasification reaction flow undergoes a second heat release and cooling in the gasification reaction system, and transfers heat to the liquid organic working fluid, and utilizes the medium and low temperature waste heat to perform Rankine cycle power generation through an organic Rankine cycle power generation device (13); after the gasification reaction flow undergoes two heat releases, the pressure is reduced and gas-liquid separation is performed to obtain a gas phase mixed product with components of H2, CO, CH4 and CO2 and a liquid phase product H2O; after the gas phase product passes through a hydrogen separator (16), pure H2 and by-products of CO, CH4 and CO2 are produced.

9. A two-step hydrogen-electricity cogeneration method of plastic liquefaction-gasification using solar heating according to claim 8, characterized in that: The liquefaction reaction temperature in the liquefaction reactor (9) is 250-400°C, and the pressure is 23-28 MPa; the gasification reaction temperature in the gasification reactor (10) is 500-650°C, and the pressure is 23-28 MPa.

10. The method of solar-heated plastic liquefaction-gasification two-step hydrogen-electricity cogeneration according to claim 8, characterized in that: The melting point temperature of the molten salt material used in the solar molten salt thermal storage system is less than 400°C, and the decomposition temperature is greater than 680°C. The boiling point temperature of the organic working fluid used in the organic Rankine cycle in the organic Rankine cycle power generation device (13) is less than 20°C.

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