A waste heat recovery and utilization system and method based on supercritical water combustion technology

Abstract

The present invention discloses a waste heat recovery and utilization system and method based on supercritical water combustion technology, which includes a reactor. The reactor includes a cylinder body, an upper end cover and a lower end cover. A multi-stage heat exchanger and a material preheater are arranged inside the cylinder body. A reaction product outlet is arranged at the upper part, and a salt discharge outlet is arranged at the lower part. A softened water tank, an oxidant unit and an alcohol additive unit are connected to the reaction chamber. The material preheater is connected to the softened water tank and the material unit. A water cooling jacket is arranged on the outer wall surface of the lower end cover. A demineralized water tank is connected to the water cooling jacket. The outlet of the water cooling jacket is connected to the inlet of the multi-stage heat exchanger. The outlet of the multi-stage heat exchanger is connected to a saturated steam collection unit. The saturated steam collection unit is connected to the demineralized water tank. In the reactor of the present invention, only a heat exchanger for single fluid needs to be arranged inside. At the same time, the separation of inorganic salts has been carried out before the reaction products pass through the subsequent heat exchangers, reducing the corrosion of the inorganic salts on the heat exchanger materials and significantly reducing the investment cost of the overall heat exchanger in the system.

Description

Technical Field

[0001] The present invention belongs to the technical fields of chemical engineering and environmental protection, and relates to a waste heat recovery and utilization system and method based on supercritical hydrothermal combustion technology. Background Art

[0002] With the continuous development of industry, the organic waste liquids generated in the industrial process increase year by year, especially from industries such as pesticides, pharmaceuticals, textile printing and dyeing, and coal chemical industry. The organic components in the generated waste liquids are complex, with high concentration, high inorganic salt content, strong toxicity, and poor biodegradability, and are difficult to degrade by conventional treatment methods. If the waste liquids that do not meet the treatment standards are directly discharged, the harmful substances therein will cause serious pollution to the land and water environment and endanger human health.

[0003] At present, the main treatment method for high-concentration and high-salt organic waste liquids is the biochemical method. However, for high-difficulty and refractory organic wastewater, its COD is too high, and it may also contain heavy metal substances and high-concentration inorganic salts. These substances are all biotoxic, resulting in difficulty in treating such wastewater by biological methods, thus unable to remove the nitrogen-containing organic substances in the wastewater and unable to meet the ammonia nitrogen emission index of the wastewater.

[0004] Supercritical hydrothermal combustion (SCHC) technology is a very promising technology for treating high-concentration and high-salt organic waste liquids. This technology utilizes the special properties of water in the supercritical state (temperature > 374.1 °C, pressure > 22.1 MPa), uses supercritical water as the reaction medium for organic substances and oxygen, adds a certain amount of alcohol additives, promotes the direct supercritical hydrothermal combustion reaction of high-concentration and high-salt organic waste liquids, quickly and thoroughly destroys refractory organic pollutants, and the C, H, and N elements in the organic substances are respectively converted into harmless CO2, H2O, and N2, and the heterocyclic atoms Cl, S, P, etc. are respectively converted into corresponding inorganic acids or salts, and the heavy metals are mineralized into stable solid phases and exist in the residues, realizing the harmless treatment of high-concentration and high-salt organic waste liquids.

[0005] However, when using supercritical hydrothermal combustion technology to treat high-concentration and high-salt organic waste liquids, there are still some problems: When the conventional supercritical hydrothermal combustion system for treating high-concentration and high-salt organic waste liquids operates, it is necessary to separately set a preheater and a regenerator in the material pretreatment unit and the subsequent product treatment unit. At present, the common forms of the separately set preheater and regenerator are mostly shell-and-tube heat exchangers. The fluids flowing through the inner and outer tubes of the shell-and-tube heat exchanger are mostly high-pressure salt-containing fluids, which have strong corrosiveness to the heat exchanger, which increases the wall thickness of the preheater and the regenerator, resulting in high investment costs for the heat exchanger, and there are also certain heat losses in the separately set heat exchanger. In addition, during the operation of the conventional system, salt crystallization deposition will also occur due to too high temperature inside the reactor, affecting the safe operation of the equipment and the system. Summary of the Invention

[0006] The object of the present invention is to solve the problems in the prior art that when a supercritical water thermal combustion system treats high-concentration and high-salt organic waste liquid, the investment costs of a separate preheater and a regenerator are high, the heat loss is large, and salt crystallization deposition easily occurs inside the reactor. A waste heat recovery and utilization system and method based on supercritical water thermal combustion technology are provided.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A waste heat recovery and utilization system based on supercritical water thermal combustion technology includes a supercritical water thermal combustion reactor. The supercritical water thermal combustion reactor includes a cylinder body, an upper end cover is arranged at the upper part of the cylinder body, and a lower end cover is arranged at the lower part; the inside of the cylinder body is a reaction chamber, and a multi-stage heat extractor and a material preheater are arranged; a reaction product outlet is opened on the upper end cover, and a salt discharge outlet is opened below the lower end cover; a soft water tank, an oxidant unit and an alcohol additive unit are connected to the reaction chamber; the material preheater is connected to the soft water tank and the material unit; a water cooling jacket is arranged on the outer wall surface of the lower end cover, a demineralized water tank is connected to the water cooling jacket, the outlet of the water cooling jacket is connected to the inlet of the multi-stage heat extractor, the outlet of the multi-stage heat extractor is connected to a saturated steam collection unit, and the saturated steam collection unit is connected to the demineralized water tank.

[0009] The further improvement of the above system is as follows:

[0010] A supercritical water inlet, an oxidant inlet, an alcohol additive inlet and a material inlet are opened on the upper end cover; the outlet of the soft water tank is connected to a high-pressure soft water pump, and the outlet of the high-pressure soft water pump is respectively connected to a heating device and the inlet of the material preheater; the oxidant unit is connected to the oxidant inlet; the alcohol additive unit is connected to the alcohol additive inlet; the outlet of the material preheater is connected to the material inlet.

[0011] The reaction product outlet is connected to a product pressure reduction and separation module.

[0012] The multi-stage heat extractor includes a first-stage heat extractor, a second-stage heat extractor, a third-stage heat extractor and a fourth-stage heat extractor; the inlet of the third-stage heat extractor is connected to the outlet of the water cooling jacket, and the outlet is connected to the fourth-stage heat extractor; the outlet of the fourth-stage heat extractor is connected to an end cover cooler, and the end cover cooler is arranged inside the upper end cover; the outlet of the end cover cooler is connected to the second-stage heat extractor, the outlet of the second-stage heat extractor is connected to the first-stage heat extractor, and the outlet of the first-stage heat extractor is connected to the saturated steam collection unit.

[0013] The saturated steam collection unit includes a gas-liquid separator, the gas outlet of the gas-liquid separator is connected to a steam collection device, and the liquid outlet is connected to the demineralized water tank.

[0014] The outlet of the demineralized water tank is connected to the first low-pressure demineralized water pump and the second low-pressure demineralized water pump, and the outlets of the first low-pressure demineralized water pump and the second low-pressure demineralized water pump are both connected to the inlet of the water-cooled jacket.

[0015] The reaction chamber is divided into five sequentially connected reaction zones, and the inside of the lower end cover is an inorganic salt recovery chamber; the supercritical water inlet, oxidant inlet, alcohol additive inlet and material inlet are connected to the first reaction zone, and the first reaction zone is connected to the inorganic salt recovery chamber; a primary heat exchanger is arranged in the first reaction zone and the second reaction zone, a secondary heat exchanger is arranged in the third reaction zone, a material preheater is arranged in the fourth reaction zone, and a tertiary heat exchanger and a quaternary heat exchanger are arranged in the fifth reaction zone; the reaction product outlet is connected to the fifth reaction zone, and the salt discharge outlet is connected to the inorganic salt recovery chamber.

[0016] The flow direction of the cold fluid in the primary heat exchanger, secondary heat exchanger, material preheater, tertiary heat exchanger and quaternary heat exchanger is arranged countercurrently to the flow direction of the hot fluid of the reaction product inside the supercritical water thermal combustion reactor; the primary heat exchanger, secondary heat exchanger, material preheater, end cover cooler, tertiary heat exchanger and quaternary heat exchanger adopt a membrane wall heat exchanger, a coil heat exchanger, a serpentine tube heat exchanger or a spiral tube heat exchanger.

[0017] The first reaction zone is connected to the second reactor through an inorganic salt filtering device; the salt discharge outlet is connected to an inorganic salt recovery and utilization module.

[0018] A waste heat recovery and utilization method based on supercritical water thermal combustion technology includes the following steps:

[0019] Step 1, introducing cold material from the material unit into the material preheater, and interlocking the material preheating outlet temperature measuring point with the heating device, the first regulating valve, the second regulating valve and the high-pressure softened water pump;

[0020] When it is monitored that the temperature of the material preheating outlet temperature measuring point is lower than the low temperature threshold, turn on the high-pressure softened water pump, the first switching valve, the second switching valve and the heating device, inject supercritical water into the supercritical water thermal combustion reactor, and increase the frequency of the heating device; after the temperature of the supercritical water is raised to the preset temperature, increase the opening degree of the second regulating valve until the supercritical water thermal combustion reaction proceeds normally;

[0021] When it is detected that the temperature at the temperature measurement point of the material preheating outlet exceeds the high-temperature threshold, if supercritical water is injected into the supercritical hydrothermal combustion reactor at this time, the opening degree of the second regulating valve is reduced until the flow rate of the supercritical water drops to zero; if the temperature at the temperature measurement point of the material preheating outlet still exceeds the high-temperature threshold at this time, the opening degree of the first regulating valve is increased to inject cooling water into the material preheater until the temperature at the temperature measurement point of the material preheating outlet returns to the normal temperature; at the same time, if salt crystallization occurs in the material preheater, the opening degree of the first regulating valve and the frequency of the high-pressure soft water pump are increased to flush the material preheater until the supercritical hydrothermal combustion reaction proceeds normally;

[0022] Step 2: The preheated material, oxidant, and alcohol additive are respectively introduced into the supercritical hydrothermal combustion reactor through the material inlet, oxidant inlet, and alcohol additive inlet for supercritical hydrothermal combustion reaction. The high-temperature and high-pressure reaction products generated by the reaction are filtered by the inorganic salt filtration device to separate the inorganic salt from the liquid-phase product. The inorganic salt enters the inorganic salt recovery chamber, and the liquid-phase product exchanges heat with the first-stage heat exchanger, second-stage heat exchanger, material preheater, third-stage heat exchanger, and fourth-stage heat exchanger in sequence, and finally enters the product pressure reduction and separation module through the reaction product outlet;

[0023] Step 3: While Step 2 is being carried out, the first low-pressure desalination water pump and the third switching valve are opened to inject cooling water into the water-cooled jacket outside the lower end cover, and then it enters the third-stage heat exchanger, fourth-stage heat exchanger, end cover cooler, second-stage heat exchanger, and first-stage heat exchanger in sequence to exchange heat with the reaction products;

[0024] During the progress of Step 2 and Step 3, if it is detected that the temperature at any one of the temperature measurement points of the first temperature measurement point, second temperature measurement point, third temperature measurement point, fourth temperature measurement point, fifth temperature measurement point, sixth temperature measurement point, or seventh temperature measurement point exceeds the high-temperature threshold, the operating frequency of the first low-pressure desalination water pump is increased until the monitored temperature point returns to the normal range; if, when the first low-pressure desalination water pump is operating at full load, the temperature at any one of the temperature measurement points exceeds the high-temperature threshold, the second low-pressure desalination water pump is started and the fourth switching valve is opened so that the two pumps operate in parallel and the operating frequency of the second low-pressure desalination water pump is increased until any one of the temperature measurement points returns to normal;

[0025] Step 4: The steam generated after the low-pressure cooling water and the high-temperature and high-pressure reaction products exchange heat step by step enters the gas-liquid separator; a pressure third regulating valve is provided on the outlet pipeline of the steam at the top of the gas-liquid separator, and the pressure of the outflowing steam is controlled by adjusting the opening degree of the pressure third regulating valve so that the steam finally passing through the pressure third regulating valve is saturated steam, and the final saturated steam flows out and enters the steam collection device for further utilization;

[0026] When the demineralized water inside the gas-liquid separator reaches the high liquid level set by the liquid level monitoring point, the fourth regulating valve on the outlet pipe at the bottom of the gas-liquid separator is opened to inject the demineralized water into the demineralized water tank until the liquid level monitoring point reaches the normal liquid level range.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In the present invention, the regenerator and the preheater are both concentrated inside the reactor. Only a heat exchanger for a single fluid needs to be arranged inside the reactor. At the same time, the inorganic salts have been separated before the reaction products pass through the subsequent heat exchangers, reducing the corrosion of the heat exchanger materials by the inorganic salts and significantly reducing the overall investment cost of the heat exchangers in the system. In the present invention, the high-temperature and high-pressure reaction products are directly cooled to low-temperature and high-pressure liquid-phase products inside the reactor. At the same time, the inorganic salts are separated from the reaction products immediately after the reaction is completed, reducing the demand for high-temperature and corrosion-resistant materials for the pressure-bearing wall of the reactor and significantly reducing the investment cost of the reactor. The present invention can, through the cascade control of the material preheating temperature, while ensuring that the high-concentration and high-salt organic waste liquid undergoes a supercritical water thermal combustion reaction to degrade organic matter smoothly, avoid the problem of salt crystal deposition in the material preheater inside the reactor online, and improve the reliability of the system operation. The present invention can realize the automatic control of the wall temperatures of each heat exchanger inside the reactor, the pressure-bearing wall surface temperature of the reactor, and the wall temperature of the reactor end cover, ensure that the reaction system does not overheat, and improve the safety and reliability of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic structural diagram of the reaction system of the present invention.

[0031] Among them, 1 - softened water tank, 2 - high-pressure softened water pump, 3 - heating device, 4 - oxidant unit, 5 - alcohol additive unit, 6 - material unit, 7 - supercritical hydrothermal combustion reactor, 8 - upper end cover, 9 - lower end cover, 10 - primary heat exchanger, 11 - secondary heat exchanger, 12 - end cover cooler, 13 - material preheater, 14 - tertiary heat exchanger, 15 - quaternary heat exchanger, 16 - inorganic salt filtration device, 17 - inorganic salt recovery chamber, 18 - water-cooled jacket, 19 - inorganic salt recovery and utilization module, 20 - demineralized water tank, 21 - first low-pressure demineralized water pump, 22 - second low-pressure demineralized water pump, 23 - product pressure reduction and separation module, 24 - gas-liquid separator, 25 - steam collection device, V1 - first on-off valve, V2 - second on-off valve, V3 - third on-off valve, V4 - fourth on-off valve, V5 - first regulating valve, V6 - second regulating valve, V7 - third regulating valve, V8 - fourth regulating valve, N1 - supercritical water inlet, N2 - oxidant inlet, N3 - alcohol additive inlet, N4 - material inlet, N5 - reaction product outlet, N6 - salt discharge outlet. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0035] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention. In addition, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0036] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0037] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "coupled" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0038] The following further describes the present invention in detail with reference to the drawings:

[0039] See Figure 1 , the embodiments of the present invention disclose a waste heat recovery and utilization system based on supercritical water combustion technology, including a softened water unit, a demineralized water unit, an oxidant unit, an alcohol additive unit, a material unit, a supercritical water combustion reactor, and a saturated steam collection unit.

[0040] The softened water unit includes a softened water tank 1 and a high-pressure softened water pump 2 connected in sequence. The outlet of the high-pressure softened water pump 2 is divided into two paths. One path is connected to the inlet of a heating device 3, and the outlet of the heating device 3 is connected to the supercritical water inlet N1 of the supercritical water combustion reactor 7. The other path is connected to the inlet pipeline of a material preheater 13.

[0041] The outlet pipeline of the material preheater 13 is provided with a temperature monitoring point TIC101, which is interlocked with the first regulating valve V5, the second regulating valve V6, the high-pressure softened water pump 2, and the heating device 3 respectively. Temperature monitoring points TIC201, TIC202, TIC203, TIC204, TIC205, TIC206, and TIC207 are respectively provided on the pressure-bearing wall surface of the upper end cover 8, the inner side wall surface of the supercritical water thermal combustion reactor 7, the pressure-bearing wall surface of the lower end cover 9, the wall surface of the primary heat exchanger 10, the wall surface of the secondary heat exchanger 11, the wall surface of the material preheater 13, and the reaction product outlet N5 pipeline, and are respectively interlocked with the first low-pressure desalinated water pump 21 and the second low-pressure desalinated water pump 22. The liquid level monitoring point LIC101 of the gas-liquid separator 24 is interlocked with the fourth regulating valve V8, and the pressure monitoring point PIC101 of the gas-liquid separator 24 is interlocked with the third regulating valve V7.

[0042] The desalinated water unit includes a desalinated water tank 20, a first low-pressure desalinated water pump 21, and a second low-pressure desalinated water pump 22. The outlet of the desalinated water tank 20 is divided into two paths. One path is connected to the inlet of the first low-pressure desalinated water pump 21, and the outlet of the first low-pressure desalinated water pump 21 is connected to the inlet of the water-cooled jacket 18 of the supercritical water thermal combustion reactor 7. The other path is connected to the inlet of the second low-pressure desalinated water pump 22, and the outlet of the second low-pressure desalinated water pump 22 is connected to the outlet pipeline of the first low-pressure desalinated water pump 21.

[0043] The oxidant unit, the outlet of the oxidant unit 4 is connected to the oxidant inlet N2 of the supercritical water thermal combustion reactor 7.

[0044] The alcohol additive unit, the outlet of the alcohol additive unit 5 is connected to the alcohol additive inlet N3 of the supercritical water thermal combustion reactor 7. Alcohol additives include, but are not limited to, alcohols such as methanol, ethanol, ethylene glycol, and isopropanol.

[0045] The material unit, the outlet of the material unit 6 is connected to the inlet of the material preheater 13.

[0046] The supercritical water thermal combustion reactor, a end cover cooler 12 is provided inside the upper end cover 8 of the supercritical water thermal combustion reactor 7; a primary heat exchanger 10, a secondary heat exchanger 11, a material preheater 13, a tertiary heat exchanger 14, a quaternary heat exchanger 15, and an inorganic salt filtration device 16 are provided inside the reactor; a water-cooled jacket 18 is provided on the outer wall surface of the lower end cover 9. The outlet of the water-cooled jacket 18 is sequentially connected to the inlets and outlets of the tertiary heat exchanger 14, the quaternary heat exchanger 15, the end cover cooler 12, the secondary heat exchanger 11, and the primary heat exchanger 10. The outlet of the primary heat exchanger 10 is connected to the steam inlet of the gas-liquid separator 24.

[0047] The upper end cover 8 is provided with a supercritical water inlet N1, an oxidant inlet N2, an alcohol additive inlet N3, a material inlet N4, and a reaction product outlet N5. The reaction product outlet N5 of the supercritical water combustion reactor 7 is connected to the product pressure reduction and separation module 23. Inside the lower end cover 9 of the supercritical water combustion reactor 7 is an inorganic salt recovery chamber 17, and the salt discharge outlet N6 at the bottom is connected to the inorganic salt recovery and utilization module 19.

[0048] The flow directions of the cold fluids in the primary heat exchanger 10, secondary heat exchanger 11, material preheater 13, tertiary heat exchanger 14, and quaternary heat exchanger 15 are all arranged countercurrently to the hot fluid of the reaction product inside the reactor. Heat exchangers such as the primary heat exchanger 10, secondary heat exchanger 11, material preheater 13, end cover cooler 12, tertiary heat exchanger 14, and quaternary heat exchanger 15 include but are not limited to forms such as membrane walls, coil tubes, serpentine tubes, and spiral tubes.

[0049] The saturated steam collection unit includes a gas-liquid separator 24. The steam outlet of the gas-liquid separator 24 is connected to the steam collection device 25, and the bottom water outlet of the gas-liquid separator 24 is connected to the demineralized water inlet of the demineralized water storage tank 20.

[0050] The embodiment of the present invention also discloses a waste heat recovery method based on supercritical water combustion technology, including the following steps:

[0051] Step 1: During normal operation, first introduce the cold material from the material unit 6 into the material preheater 13. The material preheating outlet temperature measuring point TIC101 is interlocked with the heating device 3, the first regulating valve V5, the second regulating valve V6, and the high-pressure soft water pump 2.

[0052] When it is monitored that the material preheating temperature TIC101 is too low, turn on the high-pressure soft water pump 2, the first on-off valve V1, the second on-off valve V2, and the heating device 3 to inject supercritical water into the supercritical water combustion reactor 7, and gradually increase the frequency of the heating device 3 at a certain amplitude. After the temperature of the supercritical water rises to a certain level, gradually increase the opening degree of the second regulating valve V6 at a certain amplitude until the supercritical water combustion reaction proceeds normally.

[0053] When it is monitored that the preheating temperature TIC101 of the material is too high, if supercritical water is injected into the supercritical hydrothermal combustion reactor 7 at this time, the opening degree of the second regulating valve V6 is gradually reduced by a certain amplitude until the flow rate of the supercritical water drops to zero. If the preheating temperature TIC101 of the material is still too high at this time, the opening degree of the first regulating valve V5 is gradually increased by a certain amplitude, and cooling water is injected into the material preheater 13 until the preheating temperature TIC101 of the material returns to the normal temperature. At the same time, if salt crystallization occurs in the material preheater 13 due to too high temperature, the opening degree of the first regulating valve V5 and the frequency of the high-pressure softened water pump 2 can be further gradually increased to flush the material preheater 13 until the normal operation of the supercritical hydrothermal combustion reaction is maintained.

[0054] Step 2: The preheated material, oxidant, and alcohol additive are respectively introduced into the reactor through the material inlet N4, oxidant inlet N2, and alcohol additive inlet N3 for supercritical hydrothermal combustion reaction. The high-temperature and high-pressure reaction products generated by this reaction are filtered by the inorganic salt filtration device 16 to separate the inorganic salt from the liquid-phase product. The inorganic salt enters the inorganic salt recovery chamber 17, and the liquid-phase product exchanges heat with the primary heat exchanger, secondary heat exchanger, material preheater, tertiary heat exchanger, and quaternary heat exchanger in sequence, and finally enters the product pressure reduction and separation module 23 through the reaction product outlet N5.

[0055] Step 3: While step 2 is proceeding normally, the first low-pressure desalination water pump 21 and the third switching valve V3 are opened, and cooling water is injected into the water-cooled jacket 18 outside the lower end cover 9, and then enters the tertiary heat exchanger 14, quaternary heat exchanger 15, end cover cooler 12, secondary heat exchanger 11, and primary heat exchanger 10 in sequence to exchange heat with the reaction products.

[0056] During the progress of step 2 and step 3, if it is monitored that any of the temperature measurement points TIC201, TIC202, TIC203, TIC204, TIC205, TIC206, TIC207 is over-temperature, the operating frequency of the first low-pressure desalination water pump 21 is gradually increased by a certain amplitude until the monitored temperature point returns to the normal range; if any temperature monitoring point is still over-temperature when the first low-pressure desalination water pump 21 is operating at full load, the second low-pressure desalination water pump 22 is opened, and the fourth switching valve V4 is opened, so that the two pumps operate in parallel, and the operating frequency of the second low-pressure desalination water pump 22 is gradually increased by a certain amplitude until any temperature monitoring point returns to normal.

[0057] Step 4: Based on Step 3, the steam generated after the low-pressure cooling water and the high-temperature and high-pressure reaction products are heat-exchanged step by step enters the gas-liquid separator 24. A third pressure regulating valve V7 is provided on the outlet pipeline of the steam at the top of the gas-liquid separator 24. By adjusting the opening degree of the third pressure regulating valve V7, the pressure of the outflowing steam is controlled to ensure that the steam after finally passing through the third pressure regulating valve V7 is always saturated steam under a specific pressure. After the final saturated steam flows out, it enters the steam collection device 25 for further utilization.

[0058] When the desalted water inside the gas-liquid separator 24 reaches the high liquid level set by the liquid level monitoring point LIC101, the fourth regulating valve V8 on the bottom water outlet pipeline of the gas-liquid separator 24 is gradually opened by a certain amplitude to inject the desalted water into the desalted water tank 20 until the liquid level monitoring point LIC101 reaches the normal liquid level range.

[0059] Example:

[0060] In this example, the supercritical water combustion technology is used to treat high-concentration and high-salt organic waste liquid. Taking ethanol as the alcohol additive as an example, the waste heat recovery system and method based on the critical water combustion technology are described in detail:

[0061] (1) During the normal operation of the system, the self-heating of the high-concentration and high-salt organic waste liquid system can be fully realized, and no external heat source is required during the normal operation. The high-concentration and high-salt organic waste liquid first enters the material preheater 13 from the material unit 6. The high-temperature and high-pressure reaction products preheat it to 320 °C. At the same time, during the normal operation of the system, the temperature measuring point TIC101 at the outlet of the material preheating is interlocked with the electric heater 3, the first regulating valve V5, the second regulating valve V6, and the high-pressure soft water pump 2.

[0062] (2) When it is monitored that the material preheating temperature TIC101 is much lower than 320 °C, the high-pressure soft water pump 2, the first switching valve V1, the second switching valve V2, and the heating device 3 are turned on. Supercritical water is injected into the reactor through the supercritical water inlet N1 on the upper end cover 8, and the frequency of the heating device 3 is gradually increased by 5%. The temperature of the injected supercritical water is increased. After the temperature of the supercritical water is increased to above 600 °C, the opening degree of the second regulating valve V6 is gradually increased by 5% to increase the amount of the injected supercritical water until the supercritical water combustion reaction proceeds normally.

[0063] (3) When it is monitored that the preheated material temperature TIC101 is higher than 320 °C, if supercritical water is injected into the supercritical hydrothermal combustion reactor (7) at this time, the opening of the second regulating valve V6 is gradually reduced by 5% to reduce the amount of injected supercritical water until the flow rate of the supercritical water drops to zero. If the preheated material temperature TIC101 is still too high at this time, the opening of the first regulating valve V5 is gradually increased by 5% to inject cooling water at 20 °C and 25 MPa into the inlet pipeline of the material preheater 13 to cool the high-concentration and high-salt organic waste liquid until the preheated material temperature TIC101 returns to 320 °C. At the same time, if salt crystallization occurs in the material preheater 13 due to the too high preheated material temperature TIC101, the opening of the first regulating valve V5 and the frequency of the high-pressure softened water pump 2 can be further gradually increased to flush the material preheater 13 until the normal operation of the supercritical hydrothermal combustion reaction is maintained.

[0064] (4) The preheated high-concentration and high-salt organic waste, oxidant, and ethanol at 320 °C are respectively introduced into the reactor through the material inlet N4, oxidant inlet N2, and alcohol additive inlet N3 to carry out supercritical hydrothermal combustion reaction. The high-temperature and high-pressure reaction products generated by this reaction are filtered by the inorganic salt filtration device 16 to separate the inorganic salts from the liquid-phase products. The inorganic salts enter the inorganic salt recovery chamber 17, and the liquid-phase products are successively heat-exchanged with the primary heat exchanger, secondary heat exchanger, material preheater, tertiary heat exchanger, and quaternary heat exchanger, and finally cooled to 20 °C and enter the product pressure reduction and separation module 23 through the reaction product outlet N5.

[0065] (5) While the reaction is proceeding normally, the first low-pressure desalination water pump 21 and the third switching valve V3 need to be opened to inject cooling water at 20 °C and 0.8 MPa into the water-cooled jacket 18 outside the lower end cover 9, and then successively enter the tertiary heat exchanger 14, quaternary heat exchanger 15, end cover cooler 12, secondary heat exchanger 11, and primary heat exchanger 10 to carry out heat exchange with the reaction products.

[0066] (6) During the normal operation of the system, if it is monitored that any of the temperature measurement points TIC201, TIC202, TIC203, TIC204, TIC205, TIC206, TIC207 exceeds 320 °C, the operating frequency of the first low-pressure desalination water pump 21 is gradually increased by 5% until the monitored temperature point returns to the normal range; if any temperature monitoring point is still over-temperature when the first low-pressure desalination water pump 21 is operating at full load, the second low-pressure desalination water pump 22 is opened and the fourth switching valve V4 is opened to make the two pumps operate in parallel, and the operating frequency of the second low-pressure desalination water pump 22 is gradually increased by 5% until any temperature monitoring point returns to normal.

[0067] (7) After the cooling water and the reaction products are heat-exchanged step by step, saturated steam at 0.8 MPa and 170 °C is generated and enters the gas-liquid separator 24 from the outlet of the first-stage heat extractor 10 for steam-water separation. A third pressure regulating valve V7 is provided on the outlet pipeline of the steam at the top of the gas-liquid separator 24. The third pressure regulating valve V7 is interlocked with the pressure measuring point PIC101 on the gas-liquid separator 24. After the steam flows out of the outlet of the gas-liquid separator 24, the pressure of the outflowing steam is controlled by adjusting the opening of the third pressure regulating valve V7 to ensure that the steam finally passing through the third pressure regulating valve V7 is always saturated steam at 0.8 MPa and flows into the steam collection device 25 for further utilization.

[0068] (8) When the desalted water inside the gas-liquid separator 24 reaches the high liquid level set by the liquid level monitoring point LIC101, the fourth regulating valve V8 on the bottom water outlet pipeline of the gas-liquid separator 24 is gradually opened by 5% to inject the desalted water into the desalted water tank 20 until the liquid level monitoring point LIC101 reaches the normal liquid level range.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A waste heat recovery and utilization system based on supercritical water combustion technology, characterized in that It includes a supercritical hydrothermal combustion reactor (7), and the supercritical hydrothermal combustion reactor (7) includes a cylinder body, with an upper end cover (8) arranged at the upper part of the cylinder body and a lower end cover (9) arranged at the lower part; the inside of the cylinder body is a reaction chamber, and a multi-stage heat extractor and a material preheater (13) are arranged; a reaction product outlet (N5) is opened on the upper end cover (8), and a salt discharge outlet (N6) is opened at the lower part of the lower end cover (9); a softened water tank (1), an oxidant unit (4) and an alcohol additive unit (5) are connected to the reaction chamber; the material preheater (13) is connected to the softened water tank (1) and a material unit (6); a water-cooled jacket (18) is arranged on the outer wall surface of the lower end cover (9), a demineralized water tank (20) is connected to the water-cooled jacket (18), the outlet of the water-cooled jacket (18) is connected to the inlet of the multi-stage heat extractor, and the outlet of the multi-stage heat extractor is connected to a saturated steam collection unit, and the saturated steam collection unit is connected to the demineralized water tank (20); A supercritical water inlet (N1), an oxidant inlet (N2), an alcohol additive inlet (N3) and a material inlet (N4) are opened on the upper end cover (8); the outlet of the softened water tank (1) is connected to a high-pressure softened water pump (2), and the outlet of the high-pressure softened water pump (2) is respectively connected to the inlets of a heating device (3) and the material preheater (13), and a first switching valve (V1) and a second switching valve (V2) are arranged between the high-pressure softened water pump (2) and the heating device (3); the oxidant unit (4) is connected to the oxidant inlet (N2); the alcohol additive unit (5) is connected to the alcohol additive inlet (N3); the outlet of the material preheater (13) is connected to the material inlet (N4); The multi-stage heat extractor includes a first-stage heat extractor (10), a second-stage heat extractor (11), a third-stage heat extractor (14) and a fourth-stage heat extractor (15); the reaction chamber is divided into five sequentially connected reaction zones, and the inside of the lower end cover (9) is an inorganic salt recovery chamber (17); the supercritical water inlet (N1), the oxidant inlet (N2), the alcohol additive inlet (N3) and the material inlet (N4) are communicated with the first reaction zone, and the first reaction zone is communicated with the inorganic salt recovery chamber (17); the first-stage heat extractor (10) is arranged in the first reaction zone and the second reaction zone, the second-stage heat extractor (11) is arranged in the third reaction zone, the material preheater (13) is arranged in the fourth reaction zone, and the third-stage heat extractor (14) and the fourth-stage heat extractor (15) are arranged in the fifth reaction zone; the reaction product outlet (N5) is connected to the fifth reaction zone, and the salt discharge outlet (N6) is connected to the inorganic salt recovery chamber (17); The flow direction of the cold fluid in the first-stage heat extractor (10), the second-stage heat extractor (11), the material preheater (13), the third-stage heat extractor (14) and the fourth-stage heat extractor (15) is arranged in a countercurrent manner to the flow direction of the hot fluid of the reaction product inside the supercritical hydrothermal combustion reactor (7); The first reaction zone is communicated with the second reaction zone through an inorganic salt filtering device (16).

2. The waste heat recovery and utilization system based on the supercritical water combustion technology according to claim 1, wherein The reaction product outlet (N5) is connected to a product pressure reduction and separation module (23).

3. The waste heat recovery and utilization system based on supercritical water combustion technology according to claim 2, characterized in that The inlet of the tertiary heat extractor (14) is connected to the outlet of the water-cooling jacket (18), and the outlet is connected to the quaternary heat extractor (15); the outlet of the quaternary heat extractor (15) is connected to the end cover cooler (12), and the end cover cooler (12) is arranged in the upper end cover (8); the outlet of the end cover cooler (12) is connected to the secondary heat extractor (11), the outlet of the secondary heat extractor (11) is connected to the primary heat extractor (10), and the outlet of the primary heat extractor (10) is connected to the saturated steam collection unit.

4. The waste heat recovery and utilization system based on supercritical water combustion technology according to claim 3, characterized in that The saturated steam collection unit includes a gas-liquid separator (24), the gas outlet of the gas-liquid separator (24) is connected to the steam collection device (25), and the liquid outlet is connected to the demineralized water tank (20).

5. The waste heat recovery and utilization system based on supercritical water combustion technology according to claim 4, characterized in that, The outlet of the demineralized water tank (20) is connected to the first low-pressure demineralized water pump (21) and the second low-pressure demineralized water pump (22), and the outlets of the first low-pressure demineralized water pump (21) and the second low-pressure demineralized water pump (22) are both connected to the inlet of the water-cooling jacket (18).

6. The waste heat recovery and utilization system based on supercritical water combustion technology according to claim 5, wherein The primary heat extractor (10), secondary heat extractor (11), material preheater (13), end cover cooler (12), tertiary heat extractor (14), and quaternary heat extractor (15) adopt a membrane wall heat exchanger, a coil heat exchanger, a serpentine tube heat exchanger, or a spiral tube heat exchanger.

7. The waste heat recovery and utilization system based on supercritical water combustion technology according to claim 6, characterized in that, The salt discharge outlet (N6) is connected to the inorganic salt recycling module (19).

8. A method for waste heat recovery and utilization based on supercritical water combustion technology using the system described in claim 7, characterized in that, It includes the following steps: Step 1, introduce the cold material from the material unit (6) into the material preheater (13). There is a material preheating outlet temperature measuring point (TIC101) on the outlet pipeline of the material preheater. The material preheating outlet temperature measuring point (TIC101) is interlocked with the heating device (3), the first regulating valve (V5), the second regulating valve (V6), and the high-pressure softened water pump (2). When it is monitored that the temperature of the material preheating outlet temperature measuring point (TIC101) is lower than the low temperature threshold, turn on the high-pressure softened water pump (2), the first switching valve (V1), the second switching valve (V2), and the heating device (3), inject supercritical water into the supercritical water thermal combustion reactor (7), and increase the frequency of the heating device (3); after the temperature of the supercritical water rises to the preset temperature, increase the opening of the second regulating valve (V6) adjacent to the heating device until the supercritical water thermal combustion reaction proceeds normally. When it is monitored that the temperature of the material preheating outlet temperature measuring point (TIC101) exceeds the high temperature threshold, if there is supercritical water injection in the supercritical water thermal combustion reactor (7) at this time, reduce the opening of the second regulating valve (V6) until the flow rate of the supercritical water drops to zero; if the temperature of the material preheating outlet temperature measuring point (TIC101) still exceeds the high temperature threshold at this time, increase the opening of the first regulating valve (V5) and inject cooling water into the material preheater (13) until the temperature of the material preheating outlet temperature measuring point (TIC101) returns to the normal temperature; meanwhile, if salt crystallization occurs in the material preheater (13), increase the opening of the first regulating valve (V5) adjacent to the high-pressure softened water pump and the frequency of the high-pressure softened water pump (2) to flush the material preheater (13) until the supercritical water thermal combustion reaction proceeds normally. Step 2: Feed the preheated material, oxidant, and alcohol additive into the supercritical hydrothermal combustion reactor (7) through the material inlet (N4), oxidant inlet (N2), and alcohol additive inlet (N3) respectively to carry out supercritical hydrothermal combustion reaction. The high-temperature and high-pressure reaction products generated by the reaction are filtered by the inorganic salt filtration device (16) to separate the inorganic salts from the liquid-phase products. The inorganic salts enter the inorganic salt recovery chamber (17), and the liquid-phase products are successively heat-exchanged with the first heat exchanger (10), second heat exchanger (11), material preheater (13), third heat exchanger (14), and fourth heat exchanger (15), and finally enter the product pressure-reducing and separation module (23) through the reaction product outlet (N5). Step 3: While Step 2 is in progress, start the first low-pressure desalination water pump (21) and the third switching valve (V3) connected thereto, inject cooling water into the water-cooled jacket (18) outside the lower end cover (9), and then successively enter the third heat exchanger (14), fourth heat exchanger (15), end cover cooler (12), second heat exchanger (11), and first heat exchanger (10) to carry out heat exchange with the reaction products. During the progress of Step 2 and Step 3, if it is monitored that the temperature of any one of the first temperature measurement point (TIC201), second temperature measurement point (TIC202), third temperature measurement point (TIC203), fourth temperature measurement point (TIC204), fifth temperature measurement point (TIC205), sixth temperature measurement point (TIC206), or seventh temperature measurement point (TIC207) exceeds the high-temperature threshold, increase the operating frequency of the first low-pressure desalination water pump (21) until the monitored temperature point returns to the normal range. If the temperature of any one of the temperature measurement points exceeds the high-temperature threshold when the first low-pressure desalination water pump (21) is operating at full load, start the second low-pressure desalination water pump (22), open the fourth switching valve (V4) connected thereto, so that the two pumps operate in parallel, and increase the operating frequency of the second low-pressure desalination water pump (22) until any one of the temperature measurement points returns to normal. The pressure-bearing wall surface of the upper end cover (8), the inner side wall surface of the supercritical hydrothermal combustion reactor (7), the pressure-bearing wall surface of the lower end cover (9), the wall surface of the first heat exchanger (10), the wall surface of the second heat exchanger (11), the wall surface of the material preheater (13), and the pipeline of the reaction product outlet (N5) are respectively provided with the first temperature measurement point (TIC201), second temperature measurement point (TIC202), third temperature measurement point (TIC203), fourth temperature measurement point (TIC204), fifth temperature measurement point (TIC205), sixth temperature measurement point (TIC206), and seventh temperature measurement point (TIC207), and are respectively interlocked with the first low-pressure desalination water pump (21) and the second low-pressure desalination water pump (22). Step 4: The steam generated after the low-pressure cooling water and the high-temperature and high-pressure reaction products exchange heat step by step enters the gas-liquid separator (24); a third pressure regulating valve (V7) is provided on the outlet pipeline of the steam at the top of the gas-liquid separator (24), and the opening of the third pressure regulating valve (V7) is adjusted to control the pressure of the outflowing steam, so that the steam finally passing through the third pressure regulating valve (V7) is saturated steam, and the final saturated steam flows out and enters the steam collection device (25) for further utilization; When the desalted water inside the gas-liquid separator (24) reaches the high liquid level set by the liquid level monitoring point (LIC101), open the fourth regulating valve (V8) on the bottom water outlet pipeline of the gas-liquid separator (24), and inject the desalted water into the desalted water tank (20) until the liquid level monitoring point (LIC101) reaches the normal liquid level range.

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