Ignition method of supercritical water reactor

Abstract

The embodiment of the present invention discloses an ignition method of a supercritical water reactor. The ignition method comprises: performing initial exhaust of a supercritical water reaction system; injecting water or an alkaline aqueous solution into a supercritical water reactor in the supercritical water reaction system to increase the pressure in the supercritical water reactor to the working pressure; electrically heating the supercritical water reactor to reach the starting temperature in the supercritical water reactor; injecting oxygen into the supercritical water reactor; when the starting temperature is reached in the supercritical water reactor, injecting an internal preheating reaction raw material into the supercritical water reactor, wherein the internal preheating reaction raw material undergoes an oxidation reaction with the oxygen reaching the starting temperature and the water or alkaline aqueous solution and releases heat; until the temperature in the supercritical water reactor reaches the working temperature, injecting the organic waste to be treated into the supercritical water reactor.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of supercritical water oxidation, and in particular to an ignition method of a supercritical water reactor. Background Art

[0002] Supercritical water oxidation (SCWO) is a common organic waste treatment technology that can efficiently treat toxic, difficult-to-degrade organic waste. To ensure rapid and complete degradation of the organic waste, the supercritical water reaction requires an ignition process. This involves preheating the supercritical water reactor to the required pressure and temperature before introducing the waste into the reactor for treatment.

[0003] However, the ignition process of a supercritical water reactor generally involves introducing a low-calorific value organic solvent and an oxidant into the reactor to preheat the reaction. The instability of the reaction during this process often leads to sudden temperature changes and drastic pressure fluctuations in the supercritical reactor, posing a safety hazard to equipment and personnel. Summary of the Invention

[0004] An embodiment of the present invention provides an ignition method for a supercritical water reactor. The ignition method includes: performing initial exhaust on a supercritical water reaction system; injecting water or an alkaline aqueous solution into a supercritical water reactor in the supercritical water reaction system to increase the pressure in the supercritical water reactor to an operating pressure; electrically heating the supercritical water reactor to reach an initial temperature in the supercritical water reactor; injecting oxygen into the supercritical water reactor; when the supercritical water reactor reaches the initial temperature, injecting an internal preheating reaction raw material into the supercritical water reactor, wherein the internal preheating reaction raw material undergoes an oxidation reaction with the oxygen reaching the initial temperature and the water or alkaline aqueous solution and releases heat; until the temperature in the supercritical water reactor reaches the operating temperature, injecting organic waste to be processed into the supercritical water reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Other objects and advantages of the present invention will become apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, which will help to provide a comprehensive understanding of the present invention.

[0006] Figure 1 Schematic diagram of the structure of a supercritical water reaction system according to one embodiment of the present invention.

[0007] Figure 2 1 is a flow chart of an ignition method according to an embodiment of the present invention.

[0008] Figure 3 FIG. 4 is a flow chart of an ignition method according to another embodiment of the present invention.

[0009] Figure 4 FIG. 4 is a flow chart of an ignition method according to another embodiment of the present invention.

[0010] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding.

[0011] Description of reference numerals:

[0012] 10. Supercritical water reactor; 20. Reaction raw material box; 30. Organic material box; 40. Feed pump; 50. Oxygen pump; 60. Liquid oxygen storage container; 70. Water bath vaporizer; 80. Chiller; 91. Exhaust system; 92. Emission system. DETAILED DESCRIPTION

[0013] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of this application. Obviously, the described embodiment is only one embodiment of this application, not all embodiments. Based on the described embodiments of this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0014] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the usual meanings understood by persons of ordinary skill in the field to which this application belongs. If the full text involves descriptions such as "first" and "second", the "first" and "second" descriptions are only used to distinguish similar objects and should not be understood as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data described by "first" and "second" are interchangeable under appropriate circumstances. If "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes Solution A, Solution B, or solutions in which both A and B are satisfied. In addition, for ease of description, spatial relative terms such as "above", "below", "top", "bottom", etc. may be used here to describe the spatial positional relationship between a device or feature as shown in the figure and other devices or features, and should be understood to also include different orientations in use or operation other than the orientation shown in the figure.

[0015] Supercritical water refers to water in a special state at temperatures exceeding 374°C and pressures exceeding 22 MPa. In this supercritical water state, radioactive organic matter and oxygen are completely miscible in the supercritical water system and undergo a rapid oxidation reaction, oxidizing and decomposing the radioactive organic matter into carbon dioxide, water, and inorganic salts. When the supercritical water temperature exceeds 550°C, the solubility of inorganic salts in the supercritical water system reaches zero. This property of supercritical water can be used to separate radioactive elements from radioactive organic matter, for example, separating radioactive elements (present in inorganic salts) from carbon, nitrogen, and other elements. This supercritical water oxidation technology for separating radioactive elements offers advantages such as fast reaction rates, high oxidation efficiency, thorough oxidation of organic matter, complete separation of radioactive elements, direct discharge of effluent, and a simple reactor structure, making it suitable for industrialization.

[0016] Supercritical water oxidation technology is typically implemented using a supercritical water reactor. Before treating organic waste, the system must undergo an ignition process to bring the supercritical water reactor within the system to the required temperature and pressure for the oxidation reaction.

[0017] The embodiment of the present invention provides a method for igniting a supercritical water reactor. Figure 2 The ignition method in this embodiment specifically includes the following steps.

[0018] Step S20: performing initial exhaust on the supercritical water reaction system.

[0019] Step S30: injecting water or alkaline aqueous solution into the supercritical water reactor in the supercritical water reaction system to increase the pressure in the supercritical water reactor to the working pressure.

[0020] Step S40: electrically heating the supercritical water reactor to make the temperature inside the supercritical water reactor reach the initial temperature.

[0021] Step S60: injecting oxygen into the supercritical water reactor.

[0022] Step S70: When the supercritical water reactor reaches the starting temperature, internal preheating reaction raw materials are injected into the supercritical water reactor. The internal preheating reaction raw materials undergo an oxidation reaction with water and oxygen that have reached the starting temperature and release heat to preheat the supercritical water reactor internally.

[0023] Step S80: until the temperature in the supercritical water reactor reaches the operating temperature, inject the organic waste to be processed into the supercritical water reactor.

[0024] This embodiment ensures that no gas remains in the supercritical water reactor by performing an exhaust process before pressurizing the supercritical water reactor, thereby preventing the gas from affecting the subsequent oxidation reaction of the preheated reaction raw materials. Simultaneously, the exhaust process can also verify whether the supercritical water reactor is in good operating condition, and the supercritical water oxidation reaction of organic matter can be performed under the premise of ensuring that the supercritical water reactor is in good operating condition.

[0025] Moreover, by sequentially injecting water, oxygen, and internal preheating reaction raw materials into the supercritical water reactor, compared with the conventional method of simultaneously injecting oxygen and internal preheating reaction raw materials into the supercritical water reactor, the ignition method in this embodiment can control the supercritical water oxidation reaction, thereby preventing a sudden temperature change in the supercritical water reactor during the ignition process and causing a safety hazard.

[0026] The organic waste to be treated in the embodiment of the present invention can be an organic solvent evaporation residue, the main component of which is tributyl phosphate solution (TBP solution). By subjecting the organic solvent evaporation residue to supercritical water oxidation treatment, radioactive elements in the organic solvent evaporation residue can be separated.

[0027] In some embodiments, as Figure 1 As shown, the supercritical water reaction system includes a supercritical water reactor 10 and a water tank (not shown) connected to the supercritical water reactor, a reaction raw material box 20 and an organic material box 30. Among them, the water tank is used to store water, and a water pump and a peristaltic pump are provided between the supercritical water reactor and the water tank. The peristaltic pump can control the flow of water. The reaction raw material box 20 is used to store the internal preheated reaction raw materials, and the organic material box 30 is used to store the organic waste to be processed.

[0028] Optionally, the internal preheating reaction raw materials in the present embodiment can be injected into the supercritical water reactor through an organic matter delivery system. Wherein, the reaction raw material box 20 is connected to the reaction raw material peristaltic pump through a delivery pipe, and the reaction raw material peristaltic pump is used to control the flow rate of the internal preheating reaction raw materials. The organic material box 30 is connected to the organic feed liquid peristaltic pump through another delivery pipe, and the organic feed liquid peristaltic pump is used to transport the organic waste to be processed. At the same time, the supercritical water reactor 10 is connected to the outlet of the feed pump 40 through a feed pipe, and the inlet of the feed pump 40 is connected to the reaction raw material peristaltic pump and the organic feed liquid peristaltic pump respectively through two delivery pipes, thereby transporting the internal preheating reaction raw materials or the organic waste to be processed through the feed pump 40.

[0029] In this embodiment, an external peristaltic pump is used to accurately control the flow of the internal preheating reaction raw materials and the organic waste to be processed, thereby achieving control of the oxidation reaction of the internal preheating reaction raw materials and oxygen.

[0030] In step S20 , the supercritical water reaction system may be degased by injecting water or alkaline aqueous solution into the system.

[0031] Specifically, the supercritical water reactor can be filled with water to perform exhaust treatment on the supercritical water reactor. Wherein, a drain valve is provided on the top of the supercritical water reactor. When the supercritical water reactor is started, the drain valve is opened and water or alkaline aqueous solution is continuously injected into the supercritical water reaction system. When no gas is discharged from the drain valve on the top of the supercritical water reactor and the no gas discharge state is maintained for a period of time, it is determined that the supercritical water reactor is filled with liquid, ensuring that the gas in the supercritical water reactor is emptied, and the drain valve can be closed at this time.

[0032] In addition, the water pump, peristaltic pump, feed pump, peristaltic pump for reaction raw materials, feed pipe, and delivery pipe can be filled with water or alkaline aqueous solution to degas them. The above pumps are started to evacuate the gas in the water pump, peristaltic pump, feed pump, peristaltic pump for reaction raw materials, feed pipe, and delivery pipe.

[0033] In step S30, after the gas in the supercritical water reaction system is emptied, the supercritical water reactor can be pressurized. Specifically, after starting a water pump, a peristaltic pump, a feed pump, and a reaction raw material peristaltic pump in an exhaust process, the flow of each of the above-mentioned pumps can be set to a predetermined target value, so as to inject liquid (water or alkaline aqueous solution) into the supercritical water reactor. The back pressure valve on the outlet pipe of the supercritical water reactor is then regulated, so that the pressure in the supercritical water reactor is increased to required operating pressure under an unheated state, so that the pressure condition required for oxidation reaction of treated organic waste in the supercritical water reactor is met.

[0034] In this embodiment, the operating pressure of the supercritical water reactor can be 20 MPa. Under this operating pressure, the injection of oxygen and the organic waste to be processed (for example, the residual liquid of the organic solvent) can allow the oxygen and the organic waste to be processed to quickly complete the oxidation reaction in the supercritical water system.

[0035] In this embodiment, the alkaline aqueous solution used for exhaust treatment and pressurization can be a sodium hydroxide solution to keep the supercritical water reactor in alkaline conditions, so as to prevent corrosion to the equipment when the TBP liquid is subsequently introduced to wait for the treatment of organic waste.

[0036] In step S40, when the working pressure is reached in the supercritical water reactor, the supercritical water reactor is electrically heated to make the water or alkaline aqueous solution in the supercritical water reactor reach the starting temperature. At this starting temperature, the subsequently injected oxygen and the internal preheated reaction raw materials can undergo an oxidation reaction.

[0037] In some embodiments, an electric heater is provided outside the supercritical water reactor. When the electric heater is activated, the outer wall of the supercritical water reactor can be electrically heated, thereby causing the internal temperature of the supercritical water reactor to reach the starting temperature.

[0038] In step S60, after the supercritical water reactor is electrically heated, oxygen may be injected into the supercritical water reactor.

[0039] Specifically, the supercritical water reactor is connected to an oxygen pump 50 via an oxygen supply pipeline, which is in turn connected to a liquid oxygen storage container 60. A water bath vaporizer 70 is connected between the oxygen pump 50 and the liquid oxygen storage container 60. Turning on the oxygen pump 50 continuously injects oxygen into the supercritical water reactor via the oxygen supply pipeline. Furthermore, a metering pump is provided on the oxygen supply pipeline. During the oxygen injection process, the metering pump can be frequency-controlled to adjust the oxygen flow rate. Furthermore, the oxygen flow rate can be adjusted based on preset flow parameters.

[0040] like Figure 3 As shown, after the supercritical water reaction system reaches the working pressure and before oxygen is injected into the supercritical water reactor, step S50 is further included. In step S50, the supercritical water reaction system can be exhausted again to ensure that the supercritical water reactor operates well again.

[0041] In some embodiments, the supercritical water reactor may be vented again using the same method used for initial venting.

[0042] In some embodiments, the top of the supercritical water reactor is provided with a drain valve, and the oxygen supply pipeline is also provided with a drain valve. When exhausting again, the drain valve at the top of the supercritical water reactor and the drain valve on the oxygen supply pipeline can be opened to ensure that the supercritical water reactor, the water bath vaporizer 70 and the oxygen supply pipeline are filled with liquid (water or alkaline aqueous solution), that is, the gas has been evacuated. Specifically, when the drain valve remains in a state of no gas discharge, it can be determined that the gas has been evacuated.

[0043] The embodiments of the present invention can ensure that the supercritical water reaction system operates well and that there is no gas in the system by performing primary exhaust before water injection and secondary exhaust before oxygen injection, thereby making the subsequent oxidation reaction controllable.

[0044] In this embodiment, an excess amount of oxygen relative to the internal preheating reaction raw materials can be injected into the supercritical water reactor to ensure that oxygen is always in excess during the subsequent oxidation reaction process of the internal preheating reaction raw materials and oxygen.

[0045] On the basis of ensuring that excess oxygen is introduced into the supercritical water reaction, the oxidation reaction rate can be controlled by adjusting the input amount of the internal preheating reaction raw material, thereby achieving rate control of the oxidation reaction, preventing the oxidation reaction from being too fast, resulting in excessive temperature increase in the supercritical water reactor. Specifically, the rate of the oxidation reaction can be slowed down by reducing the input amount of the internal preheating reaction raw material to slow down the temperature increase rate in the supercritical water reactor. By increasing the input amount of the internal preheating reaction raw material, the rate of the oxidation reaction can be accelerated, causing the supercritical water reactor to heat up rapidly.

[0046] Further, when using the supercritical water reaction system to process the organic solvent evaporation residue that main component is TBP, because the organic solvent evaporation residue has higher calorific value, therefore before processing the organic solvent evaporation residue, it is necessary to preheat the supercritical water reactor inside.In the present embodiment, use this alternative solution of interior preheating reaction raw material to carry out the preheating of supercritical water reactor inside, by the oxidation reaction exothermicity of interior preheating reaction raw material and oxygen in supercritical water system, realize inside preheating, thus verify running state and the safety of supercritical water reactor.

[0047] In this embodiment, the internal preheating reaction raw materials injected into the supercritical water reactor undergo an oxidation reaction with water and oxygen reaching the initial temperature in the supercritical water reactor. The heat released by the oxidation reaction of the internal preheating reaction raw materials is used to increase the overall temperature in the supercritical water reactor to the operating temperature required by the supercritical water reactor, thereby meeting the temperature conditions required for the oxidation reaction of the organic waste to be treated in the supercritical water reactor.

[0048] After the working pressure and the starting temperature are reached in the supercritical water reactor, the organic waste to be treated can be controlled to start being injected into the supercritical water reactor, and the flow rate of the organic waste to be treated can be gradually increased until the organic waste to be treated reaches the expected flow rate.

[0049] In some embodiments, the internal preheating reaction raw material may be a sucrose solution. Using a sucrose solution as the internal preheating reaction raw material makes the oxidation reaction safe and controllable, enabling verification of the operating status and safety of the supercritical water reactor under controllable conditions. Furthermore, both the reactants and products are readily soluble in water. Furthermore, the sucrose solution is inexpensive and low in cost.

[0050] Furthermore, the operating temperature of the supercritical water reactor in this embodiment is 500-550° C., and the starting temperature is above 280° C. At this starting temperature, the heat released by the oxidation reaction of the internal preheating reaction raw materials and oxygen can quickly increase the temperature inside the supercritical water reactor to the operating temperature of 500-550° C.

[0051] In this embodiment, a sucrose solution of appropriate concentration can be selected according to actual needs. By adjusting the concentration and flow rate of the sucrose solution, the heating rate of the supercritical water reactor can be controlled. For example, when the supercritical water reactor meets the conditions of a starting temperature of 280°C or above, a sucrose solution concentration of 50wt% and a flow rate exceeding 8L / h, the overall temperature of the supercritical water reactor can be quickly and stably increased to 500-550°C.

[0052] like Figure 1 As shown, the supercritical reaction system in this embodiment also includes a chiller 80, which can produce cold water. The produced cold water can be used in a heat exchanger to exchange heat with the reaction products after the preheated reaction raw materials or the oxidation reaction of the organic waste to be processed in the supercritical water reactor 10, thereby cooling the reaction products. In addition, the top of the supercritical water reactor 10 is also connected to an exhaust system 91, and the bottom is connected to an exhaust system 92, so that the gas and liquid in the supercritical water reaction system are discharged.

[0053] like Figure 4 As shown, in some embodiments, the ignition method further includes step S10. In step S10, before the supercritical water reactor is initially vented, the interior of the supercritical water reactor and the interior of the pipeline are cleaned to ensure that no organic matter remains in the supercritical water reactor and the pipeline to avoid unexpected oxidation reactions during the ignition process.

[0054] Specifically, deionized water can be injected into the supercritical water reactor and the pipeline to clean the organic matter remaining in the supercritical water reactor and the pipeline. After cleaning, the deionized water in the supercritical water reactor and the pipeline is discharged, so that the remaining organic matter flows out with the deionized water.

[0055] In this embodiment, the deionized water can be deionized water. Using deionized water can not only clean the organic matter remaining in the supercritical water reactor and pipelines, but also will not introduce excess impurities into the supercritical water reactor and pipelines, thereby preventing equipment corrosion.

[0056] The organic matter remaining in the supercritical water reactor and pipeline includes the internal preheating reaction raw materials remaining therein when the supercritical water reaction system was last run and the organic waste in the organic waste to be processed.

[0057] To clean the residual internal preheating reaction raw materials, fill the water tank and the reaction raw material box with deionized water. Fill the water pump, peristaltic pump body, reaction raw material peristaltic pump, and the pipeline between the water tank, reaction raw material box, and supercritical water reactor with deionized water. Simultaneously, deionized water can be used for exhaust. Start the peristaltic pump, water pump, and reaction raw material peristaltic pump to inject deionized water into the supercritical water reactor for cleaning, thereby ensuring that no internal preheating reaction raw materials remain in the supercritical water reactor and the pipeline.

[0058] To clean any remaining organic waste, the organic tank can be filled with deionized water, and the pipe between the organic tank and the supercritical water reactor is filled with deionized water and then vented. The feed pump is then started to allow the deionized water in the organic tank to flow into the supercritical water reactor, ensuring that no organic waste remains in the supercritical water reactor or the pipe.

[0059] In this embodiment, after the supercritical water reactor is cleaned, the feed pump is stopped and the water pump is kept running, and then the back pressure valve on the outlet pipe of the supercritical water reactor is slowly opened, and the pressure difference between the inside of the supercritical water reactor and the downstream of the outlet pipe is utilized to discharge the deionized water in the supercritical water reactor to the outside of the supercritical water reaction system, until all the deionized water is discharged, and then the water pump is stopped. Wherein, during the discharge period of the deionized water, the supercritical water reactor is in a process of gradually reducing the pressure.

[0060] In addition, the supercritical water reaction system in an embodiment of the present invention also includes an evaporation tank, and the ignition method in this embodiment also includes cleaning the evaporation tank. Specifically, desalted water can be injected into the evaporation tank, and the desalted water can be used to flush the evaporation tank. After flushing, the desalted water can be discharged from the supercritical water reaction system. In some embodiments, a flushing pipeline is provided at the bottom of the evaporation tank, and a valve is provided on the flushing pipeline. By opening the valve on the flushing pipeline, the desalted water can be injected into the evaporation tank. In some embodiments, a stop valve is also provided on the outlet pipeline of the evaporation tank. After flushing, the stop valve is opened to discharge the desalted water.

[0061] In some embodiments, before the supercritical water reactor is initially vented, the status of each pipeline and instrument in the supercritical water reaction system needs to be checked to ensure that the supercritical water reaction system can operate normally.

[0062] The ignition method in this embodiment can control the oxidation reaction rate, thereby ensuring a smooth ignition process of the supercritical water reactor, so that the supercritical water reactor reaches the pressure and temperature required for the supercritical water oxidation reaction of the organic waste to be treated, avoiding the safety hazards caused by sudden changes in the calorific value of the reactants.

[0063] Regarding the embodiments of the present invention, it should also be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0064] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for igniting a supercritical water reactor, characterized in that: include: Perform initial exhaust of the supercritical water reaction system; Injecting water or alkaline aqueous solution into the supercritical water reactor in the supercritical water reaction system to increase the pressure in the supercritical water reactor to the working pressure; Electrically heating the supercritical water reactor to make the supercritical water reactor reach a starting temperature; injecting oxygen into the supercritical water reactor; When the supercritical water reactor reaches the starting temperature, injecting an internal preheating reaction raw material into the supercritical water reactor, wherein the internal preheating reaction raw material undergoes an oxidation reaction with oxygen reaching the starting temperature and water or an alkaline aqueous solution and releases heat; until the temperature in the supercritical water reactor reaches the operating temperature, injecting the organic waste to be treated into the supercritical water reactor; Before injecting oxygen into the supercritical water reactor, exhausting the supercritical water reaction system again; Injecting an excess amount of oxygen relative to the internal preheated reaction raw materials into the supercritical water reactor; The input amount of the internal preheating reaction raw materials is adjusted to control the oxidation reaction rate.

2. The ignition method according to claim 1, characterized in that: The alkaline aqueous solution is a sodium hydroxide solution.

3. The ignition method according to claim 1, characterized in that: The internal preheating reaction raw material is sucrose solution.

4. The ignition method according to claim 1, characterized in that: Before the supercritical water reactor is initially vented, the interior of the supercritical water reactor and the interior of the pipeline are cleaned.

5. The ignition method according to claim 4, characterized in that: The cleaning of the interior of the supercritical water reactor and the interior of the pipeline comprises: Injecting deionized water into the supercritical water reactor and the pipeline to clean the organic matter remaining in the supercritical water reactor and the pipeline; After cleaning is completed, the desalted water in the supercritical water reactor and the pipeline is discharged.

6. The ignition method according to claim 5, characterized in that: The supercritical water reaction system further comprises an organic material box and a pipeline and a feed pump arranged between the organic material box and the supercritical water reactor; the method further comprises: The desalted water is filled into the organic feed box, and the feed pump is started to clean the organic waste remaining in the supercritical water reactor and the pipeline.

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