A startup method for a supercritical water gasification system based on internal oxidation exothermicity

Abstract

The present invention discloses a startup method for a supercritical water gasification system based on internal oxidation heat release, comprising the following steps: releasing heat through an oxidation reaction in an oxidation reactor to preheat the oxidation reactor, and then returning the oxidized high-temperature fluid in reverse to the gasification reactor and simultaneously feeding it into a heat exchanger to achieve overall temperature increase of the supercritical water gasification system. This method can achieve rapid temperature increase of the supercritical water gasification system while avoiding the need to add external equipment or heat sources.

Description

Technical Field

[0001] The invention belongs to the field of supercritical water gasification technology utilization and relates to a startup method of a supercritical water gasification system based on internal oxidation heat release. Background Art

[0002] Supercritical water gasification technology is a clean and efficient technology for utilizing coal, biomass, organic fuels, and waste. It has the characteristics of fast reaction rate, mild temperature, and no high-temperature nitrogen, oxygen, nitrogen, and sulfur oxides. This is due to the use of supercritical water as the gasification reactant and homogeneous reaction environment. Supercritical water (temperature greater than 374°C, pressure greater than 22.1MPa) has excellent physical and chemical properties, such as high diffusivity and low dielectric constant, which can effectively accelerate the diffusion of reactants and products. The high solubility of organic matter forms a homogeneous reaction, greatly increasing the reaction rate. Supercritical water under high pressure has a high density, and the reforming reaction rate involving supercritical water is accelerated, which can promote the complete conversion of organic matter. Therefore, supercritical water gasification can achieve efficient and pollution-free conversion under relatively low temperature conditions.

[0003] Currently, supercritical water gasification technology still faces several difficulties, such as feeding, slag removal, and product separation under high-pressure conditions. The generation of supercritical water requires a large amount of heat absorption, and the startup of the supercritical water reaction system is a key step. Supercritical water is obtained by pressurizing and heating water. Water has a large specific volume, and the use of traditional boiler combustion and convection and radiation in heat exchange tubes requires a large heat transfer surface and equipment investment. Combustion generates pollution, which greatly hinders the clean characteristics of supercritical water gasification technology. Currently, laboratory-scale reactors mainly use electric heating to achieve supercritical water gasification conditions, and the startup process is lengthy and inefficient. Reported solutions use oxidation heat release within supercritical water to achieve self-heating of the system, but only consider the heat balance and heat transfer design after stable operation. Detailed research and solutions are currently lacking on how to achieve the transition from a cold system to an operating state during the startup process. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a startup method for a supercritical water gasification system based on internal oxidation heat release, which can achieve rapid heating of the supercritical water gasification system while avoiding the addition of external equipment or heat sources.

[0005] To achieve the above-mentioned objectives, the startup method of the supercritical water gasification system based on internal oxidation heat release described in the present invention includes the following steps: releasing heat through an oxidation reaction in an oxidation reactor to preheat the oxidation reactor, and then returning the oxidized high-temperature fluid to the gasification reactor and simultaneously sending it into a heat exchanger to achieve overall temperature increase of the supercritical water gasification system.

[0006] The supercritical water gasification system comprises a raw material tank, a high-pressure boosting pump, a gasification reactor, an oxidation reactor, a heat exchanger, a back pressure valve, a water tank, a high-pressure plunger pump, an oxidant storage tank, an oxidant boosting pump, a high-pressure gas cylinder, a gas boosting pump, a raw material control valve, a high-pressure water control valve, an oxidant control valve, a gas control valve, a first control valve and a second control valve; the outlet of the raw material tank is connected to the inlet of the gasification reactor via the high-pressure boosting pump and the raw material control valve, the outlet of the high-pressure gas cylinder is connected to the inlet of the oxidation reactor via the gas boosting pump and the gas control valve, the outlet of the oxidant storage tank is connected to the inlet of the oxidation reactor via the oxidant boosting pump and the gas control valve, and the outlet of the oxidant storage tank is connected to the inlet of the oxidation reactor via the oxidant boosting pump. The pressure pump and the oxidant control valve are connected to the inlet of the oxidation reactor, the top opening of the gasification reactor is connected to the top opening of the oxidation reactor, the bottom opening of the gasification reactor is connected to one end of the shell side of the heat exchanger, the other end of the shell side of the heat exchanger is connected to one end of the second control valve and one end of the high-pressure water control valve, the outlet of the water tank is connected to the other end of the high-pressure water control valve via the high-pressure plunger pump, the other end of the second control valve is connected to the back pressure valve, the bottom opening of the oxidation reactor is connected to the tube side inlet of the heat exchanger, and the tube side outlet of the heat exchanger is connected to the back pressure valve via the first control valve.

[0007] Specifically, it includes the system pressure increase stage, the oxidation reactor temperature increase stage, the gasification reactor temperature increase stage and the heat exchanger temperature increase stage.

[0008] During the system pressure boosting stage, open the high-pressure water control valve, back-pressure valve and first control valve, and increase the system pressure to the supercritical operating pressure through the high-pressure plunger pump. Under the control of the back-pressure valve, after the pressure stabilizes, reduce the flow of the high-pressure plunger pump to zero, and then close the high-pressure water control valve.

[0009] During the heating stage of the oxidation reactor, the gas in the high-pressure gas cylinder enters the oxidation reactor through the gas pressure pump. At the same time, the oxidant in the oxidant storage tank is pressurized by the oxidant pressure pump and enters the oxidation reactor. In the oxidation reactor, the oxidant and the gas undergo an oxidation reaction to release heat, causing the temperature of the oxidation reactor to rise until it reaches the temperature of the gasification reactor during normal operation, completing the heating of the oxidation reactor. During this process, the oxidized high-temperature fluid pushes the original low-temperature fluid inside the oxidation reactor to the high-temperature side of the heat exchanger, and then flows out through the first control valve and the back-pressure valve. When the overall temperature of the oxidation reactor reaches stability, the gasification reactor enters the heating stage.

[0010] During the temperature rise phase of the gasification reactor, the first control valve is gradually closed and the second control valve is gradually opened. The oxidized high-temperature fluid pushes the original low-temperature fluid inside the gasification reactor to the low-temperature side of the heat exchanger, and then flows out of the system through the second control valve and the back-pressure valve. When the overall temperature of the gasification reactor reaches a stable state, the heat exchanger temperature rise phase begins.

[0011] During the heating stage of the heat exchanger, the opening of the second control valve is gradually reduced, and the opening of the first control valve is gradually increased. The high-temperature fluid after oxidation is used to push the heated high-temperature fluid inside the oxidation reactor and the gasification reactor into the heat exchanger simultaneously or alternately, and then flows out of the system through the first control valve, the second control valve and the back pressure valve. When the temperature distribution inside the heat exchanger reaches the temperature distribution during normal gasification, the heating stage of the heat exchanger ends.

[0012] The heat exchanger heating stage is followed by a flow regulation stage and an initial feeding stage.

[0013] Gradually close the second control valve and gradually fully open the first control valve, then open the high-pressure water control valve and the high-pressure plunger pump, adjust the high-pressure plunger pump to gradually increase the flow rate, and at the same time, adjust the oxidant booster pump and the gas booster pump to increase the flow rate of the oxidant and gas, and gradually increase the temperature of the oxidation reactor.

[0014] Initial feeding stage: When the temperature of each part of the system is stable, open the raw material control valve and the high-pressure boosting pump, and input the raw material in the raw material tank into the gasification reactor. The gasification products in the gasification reactor flow into the oxidation reactor to participate in the oxidation reaction. As the raw material input amount and the effective components in the gasification products increase, the flow rate of the gas boosting pump is gradually reduced, and the flow rate of the oxidant boosting pump is adjusted. According to the temperature of the oxidation reactor, the high-pressure gas flow rate is finally reduced to zero, and then the gas control valve is closed.

[0015] The present invention has the following beneficial effects:

[0016] The startup method for a supercritical water gasification system based on internal oxidation exothermicity, described herein, releases heat through the oxidation reaction. The oxidized, high-temperature fluid is then returned to the gasification reactor and simultaneously flows through a heat exchanger, achieving rapid temperature increases across the entire system. It should be noted that the internal oxidation exothermicity approach employed in this invention eliminates the need for external startup devices and heating pipes, enabling the system to be operated solely through valve control, simplifying the system and reducing investment costs.

[0017] Furthermore, the internal oxidation process during the startup process of the present invention can smoothly transition to the oxidation process during normal operation, thereby accelerating the stabilization of the system and shortening the time from startup to stable production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the principle of the present invention;

[0019] Among them, 1 is a raw material tank, 2 is a high-pressure booster pump, 3 is a gasification reactor, 4 is an oxidation reactor, 5 is a heat exchanger, 6 is a back pressure valve, 7 is a water tank, 8 is a high-pressure plunger pump, 9 is an oxidant storage tank, 10 is an oxidant booster pump, 11 is a high-pressure gas cylinder, 12 is a gas booster pump, 13 is a raw material control valve, 14 is a high-pressure water control valve, 15 is an oxidant control valve, 16 is a gas control valve, 17 is a first control valve, and 18 is a second control valve. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions 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 embodiments of a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0021] The accompanying drawings illustrate schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for the purpose of clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0022] refer to Figure 1The supercritical water gasification system includes a raw material tank 1, a high-pressure booster pump 2, a gasification reactor 3, an oxidation reactor 4, a heat exchanger 5, a back pressure valve 6, a water tank 7, a high-pressure plunger pump 8, an oxidant storage tank 9, an oxidant booster pump 10, a high-pressure gas cylinder 11, a gas booster pump 12, a raw material control valve 13, a high-pressure water control valve 14, an oxidant control valve 15, a gas control valve 16, a first control valve 17 and a second control valve 18; the outlet of the raw material tank 1 is connected to the inlet of the gasification reactor 3 through the high-pressure booster pump 2 and the raw material control valve 13, the outlet of the high-pressure gas cylinder 11 is connected to the inlet of the oxidation reactor 4 through the gas booster pump 12 and the gas control valve 16, the outlet of the oxidant storage tank 9 is connected to the inlet of the oxidation reactor 4, and the outlet of the oxidant storage tank 9 is connected to the inlet of the oxidation reactor 4. The outlet is connected to the inlet of the oxidation reactor 4 through the oxidant booster pump 10 and the oxidant control valve 15, the top opening of the gasification reactor 3 is connected to the top opening of the oxidation reactor 4, the bottom opening of the gasification reactor 3 is connected to one end of the shell side of the heat exchanger 5, the other end of the shell side of the heat exchanger 5 is connected to one end of the second control valve 18 and one end of the high-pressure water control valve 14, the outlet of the water tank 7 is connected to the other end of the high-pressure water control valve 14 through the high-pressure plunger pump 8, the other end of the second control valve 18 is connected to the back pressure valve 6, the bottom opening of the oxidation reactor 4 is connected to the tube side inlet of the heat exchanger 5, and the tube side outlet of the heat exchanger 5 is connected to the back pressure valve 6 through the first control valve 17.

[0023] It should be noted that the gasification reactor 3, the oxidation reactor 4 and the heat exchanger 5 can be one or more connected in parallel or in series. In the supercritical water gasification system, the flow direction of the fluid in the pipeline can be controlled by the first control valve 17 and the second control valve 18.

[0024] In order to achieve a smooth start-up of the supercritical water gasification system, refer to Figure 1 The startup method of the supercritical water gasification system based on internal oxidation heat release of the present invention comprises the following steps:

[0025] System pressure boost: Before starting, all valves are in the closed state. First, open the high-pressure water control valve 14, the back-pressure valve 6, and the first control valve 17. The high-pressure plunger pump 8 is used to increase the system pressure to the supercritical operating pressure. Under the control of the back-pressure valve 6, after the pressure stabilizes, the flow rate of the high-pressure plunger pump 8 is reduced to zero. Then, close the high-pressure water control valve 14, and the pressure boost is completed.

[0026] Temperature-raising stage of the oxidation reactor 4: the gas in the high-pressure gas cylinder 11 enters the oxidation reactor 4 through the gas booster pump 12. At the same time, the oxidant in the oxidant storage tank 9 is pressurized by the oxidant booster pump 10 and enters the oxidation reactor 4. In the oxidation reactor 4, the oxidant and the gas undergo an oxidation reaction to release heat, causing the temperature of the oxidation reactor 4 to rise to the temperature of the gasification reactor 3 during normal operation, completing the temperature-raising stage of the oxidation reactor 4. During this process, the oxidized high-temperature fluid pushes the original low-temperature fluid inside the oxidation reactor 4 to the high-temperature side of the heat exchanger 5, and then flows out through the first control valve 17 and the back-pressure valve 6. When the overall temperature of the oxidation reactor 4 reaches stability, the temperature-raising stage of the gasification reactor 3 is entered.

[0027] The oxidant is generally pure oxygen, oxygen-rich gas or hydrogen peroxide solution, and the high-pressure gas is generally a combustible gas such as methane. Other easily reactive liquid fuels may also be used.

[0028] Gasification reactor 3 temperature rise stage: gradually close the first control valve 17, and gradually open the second control valve 18 at the same time. The oxidized high-temperature fluid pushes the original low-temperature fluid inside the gasification reactor 3 to the low-temperature side of the heat exchanger 5, and then flows out of the system through the second control valve 18 and the back pressure valve 6. When the overall temperature of the gasification reactor 3 reaches a stable state, the heat exchanger 5 temperature rise stage begins.

[0029] Heat exchanger 5 temperature rise stage: gradually reduce the opening of the second control valve 18, and gradually increase the opening of the first control valve 17. The oxidized high-temperature fluid pushes the heated high-temperature fluid inside the oxidation reactor 4 and the gasification reactor 3 to the heat exchanger 5 simultaneously or alternately, and then flows out of the system through the first control valve 17, the second control valve 18 and the back pressure valve 6. When the temperature distribution inside the heat exchanger 5 reaches a temperature distribution similar to that during normal gasification, the flow regulation stage begins.

[0030] Flow regulation stage: gradually close the second control valve 18, and gradually fully open the first control valve 17, then open the high-pressure water control valve 14 and the high-pressure plunger pump 8, adjust the high-pressure plunger pump 8 to gradually increase the flow rate, and at the same time, adjust the oxidant pressure pump 10 and the gas pressure pump 12 to increase the flow rate of the oxidant and gas, gradually increase the temperature of the oxidation reactor 4, and adjust the temperature by monitoring the temperature at various locations, and finally reach parameters close to the design working conditions;

[0031] Initial feeding stage: When the temperature of each part of the system is stable, open the raw material control valve 13 and the high-pressure boosting pump 2, and input the raw material in the raw material tank 1 into the gasification reactor 3. The gasification product in the gasification reactor 3 flows into the oxidation reactor 4 to participate in the oxidation reaction. As the raw material input amount and the effective components in the gasification product increase, the flow rate of the gas boosting pump 12 is gradually reduced, and the flow rate of the oxidant boosting pump 10 is adjusted. According to the temperature of the oxidation reactor 4, the high-pressure gas flow rate is eventually reduced to zero, and then the gas control valve 16 is closed. At this time, the parameters of each part of the system gradually stabilize and enter normal operating conditions, and the startup process is completed.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A startup method for a supercritical water gasification system based on internal oxidation heat release, characterized in that: The following steps are involved: Heat is released by the oxidation reaction in the oxidation reactor (4), thereby preheating the oxidation reactor (4). The oxidized high-temperature fluid is then returned to the gasification reactor (3) and simultaneously fed into the heat exchanger (5), thereby increasing the temperature of the entire supercritical water gasification system.

2. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 1, characterized in that: The supercritical water gasification system comprises a raw material tank (1), a high-pressure boosting pump (2), a gasification reactor (3), an oxidation reactor (4), a heat exchanger (5), a back pressure valve (6), a water tank (7), a high-pressure plunger pump (8), an oxidant storage tank (9), an oxidant boosting pump (10), a high-pressure gas cylinder (11), a gas boosting pump (12), a raw material control valve (13), a high-pressure water control valve (14), an oxidant control valve (15), a gas control valve (16), a first control valve (17) and a second control valve (18); the outlet of the raw material tank (1) is connected to the inlet of the gasification reactor (3) via the high-pressure boosting pump (2) and the raw material control valve (13), the outlet of the high-pressure gas cylinder (11) is connected to the inlet of the oxidation reactor (4) via the gas boosting pump (12) and the gas control valve (16), the oxidant storage tank (9), an oxidant boosting pump (10), a high-pressure gas cylinder (11), a gas boosting pump (12), a raw material control valve (13), a high-pressure water control valve (14), an oxidant control valve (15), a gas control valve (16), a first control valve (17) and a second control valve (18); The outlet of the storage tank (9) is connected to the inlet of the oxidation reactor (4) via the oxidant booster pump (10) and the oxidant control valve (15); the top opening of the gasification reactor (3) is connected to the top opening of the oxidation reactor (4); the bottom opening of the gasification reactor (3) is connected to one end of the shell side of the heat exchanger (5); the other end of the shell side of the heat exchanger (5) is connected to one end of the second control valve (18) and one end of the high-pressure water control valve (14); the outlet of the water tank (7) is connected to the other end of the high-pressure water control valve (14) via the high-pressure plunger pump (8); the other end of the second control valve (18) is connected to the back pressure valve (6); the bottom opening of the oxidation reactor (4) is connected to the tube side inlet of the heat exchanger (5); and the tube side outlet of the heat exchanger (5) is connected to the back pressure valve (6) via the first control valve (17).

3. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 2, characterized in that: Specifically, it includes a system pressure increasing stage, an oxidation reactor (4) temperature increasing stage, a gasification reactor (3) temperature increasing stage and a heat exchanger (5) temperature increasing stage.

4. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 3, characterized in that: During the system pressure-raising stage, the high-pressure water control valve (14), the back-pressure valve (6) and the first control valve (17) are opened, and the system pressure is raised to the supercritical operating pressure by the high-pressure plunger pump (8). Under the control of the back-pressure valve (6), after the pressure operation is stabilized, the flow rate of the high-pressure plunger pump (8) is reduced to zero, and then the high-pressure water control valve (14) is closed.

5. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 3, characterized in that: During the temperature rise phase of the oxidation reactor (4), the gas in the high-pressure gas cylinder (11) enters the oxidation reactor (4) through the gas pressure pump (12). At the same time, the oxidant in the oxidant storage tank (9) is pressurized by the oxidant pressure pump (10) and enters the oxidation reactor (4). In the oxidation reactor (4), the oxidant and the gas undergo an oxidation reaction to release heat, causing the temperature of the oxidation reactor (4) to rise until it reaches the temperature of the gasification reactor (3) during normal operation, completing the temperature rise of the oxidation reactor (4). During this process, the oxidized high-temperature fluid pushes the original low-temperature fluid inside the oxidation reactor (4) to the high-temperature side of the heat exchanger (5), and then flows out through the first control valve (17) and the back pressure valve (6). When the overall temperature of the oxidation reactor (4) reaches stability, the gasification reactor (3) enters the temperature rise phase.

6. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 3, characterized in that: During the temperature rise phase of the gasification reactor (3), the first control valve (17) is gradually closed, while the second control valve (18) is gradually opened. The oxidized high-temperature fluid pushes the original low-temperature fluid inside the gasification reactor (3) to the low-temperature side of the heat exchanger (5), and then flows out of the system through the second control valve (18) and the back pressure valve (6). When the overall temperature of the gasification reactor (3) reaches stability, the heat exchanger (5) enters the temperature rise phase.

7. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 3, characterized in that: During the temperature rise phase of the heat exchanger (5), the opening of the second control valve (18) is gradually reduced, and the opening of the first control valve (17) is gradually increased. The high-temperature fluid after oxidation is pushed simultaneously or alternately into the heat exchanger (5) by the high-temperature fluid after oxidation, and then flows out of the system through the first control valve (17), the second control valve (18) and the back pressure valve (6). When the temperature distribution inside the heat exchanger (5) reaches the temperature distribution during normal gasification, the temperature rise phase of the heat exchanger (5) ends.

8. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 3, characterized in that: The heat exchanger (5) temperature rising stage also includes a flow regulating stage and an initial feeding stage.

9. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 8, characterized in that: The second control valve (18) is gradually closed, and the first control valve (17) is gradually fully opened. Then, the high-pressure water control valve (14) and the high-pressure plunger pump (8) are opened, and the high-pressure plunger pump (8) is adjusted to gradually increase the flow rate. At the same time, the oxidant pressure pump (10) and the gas pressure pump (12) are adjusted to increase the flow rate of the oxidant and the gas, and gradually increase the temperature of the oxidation reactor (4).

10. The startup method of a supercritical water gasification system based on internal oxidation heat release according to claim 8, characterized in that: Initial feeding stage: After the temperature of the system is stabilized, the raw material control valve (13) and the high-pressure boosting pump (2) are opened, and the raw material in the raw material tank (1) is input into the gasification reactor (3). The gasification product in the gasification reactor (3) flows into the oxidation reactor (4) to participate in the oxidation reaction. As the raw material input amount and the effective components in the gasification product increase, the flow rate of the gas boosting pump (12) is gradually reduced, and the flow rate of the oxidant boosting pump (10) is adjusted. According to the temperature of the oxidation reactor (4), the high-pressure gas flow rate is finally reduced to zero, and then the gas control valve (16) is closed.

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