Novel wet oxidation system and control method thereof

Abstract

The invention provides a novel wet oxidation system and a control method thereof, and belongs to the technical field of environmental protection. The system comprises a storage bin, a feeding pump, a wet oxidation reactor, a flash evaporation reactor, a preheating reactor, a cooling device, a treatment device, an air compressor and a waste gas treatment device. According to the invention, heat is generated through a wet oxidation reaction, heat is recovered by adopting a flash evaporation process, and secondary steam generated by a flash evaporation reaction is directly introduced into a material for preheating, so that the problem of organic solid scaling caused by an indirect heat exchanger is avoided; the flash evaporation reactor and the preheating reactor which are connected in parallel are arranged, and a corresponding control method is adopted, so that continuous operation of a wet oxidation process and efficient recycling of heat are realized; and external steam provides a heat source only when the system is started, stable operation can be realized without supplying heat subsequently, the system is suitable for treatment of high-content inherent pollutants, the equipment investment and energy consumption are reduced, and the system reliability is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection technology for treating organic pollutants, and particularly relates to a novel wet oxidation system and a control method thereof. BACKGROUND

[0002] The wet oxidation technology is a treatment method for oxidizing organic matter in organic pollutants (including high-COD wastewater, sludge, feces, garden waste, etc.) by using an oxidizing agent under high temperature and high pressure. The wet oxidation technology has the remarkable features of wide range of treated organic matter, good effect, short reaction time, small reactor volume, almost no secondary pollution, and recyclable useful substances and energy. Compared with the thermal hydrolysis technology, the wet oxidation technology has higher reaction temperature and pressure when treating high-solid-content organic pollutants such as sludge, and the heat release in the wet oxidation process is significant. Therefore, theoretically, the wet oxidation reaction can be maintained without additional energy if the waste heat is less. At present, the common wet oxidation process has the following problems: (1) Limited by the process and heat recovery conditions, few processes can achieve full heat recovery. Even if the process theoretically achieves full heat recovery, there are still various limitations in actual application. For example, due to the high viscosity and high organic solid content of high-solid-content materials such as sludge, they are easily attached to the heating surface when heated or cooled, and some organic pollutants can even coking, making the attachment stronger, resulting in a decrease in heat exchange efficiency, and even causing blockage. At this time, even flushing is difficult to flush these attachments.

[0003] (2) Limited by the heat exchange process, high-solid-content organic pollutants need to be diluted before entering the system for wet oxidation, which greatly reduces the system processing energy, and thus increases the investment and operating costs.

[0004] (3) Since the wet oxidation process needs to be reacted under high temperature and high pressure, and enough oxygen needs to be added before the reaction, the wet oxidation reaction process is discontinuous, which reduces the operating efficiency of the whole system.

[0005] For example, the paper “Production Test Research on SEUE-WAO Sludge Wet Oxidation Process” describes the development of a new sludge wet oxidation treatment process, i.e., the SEUE-WAO process. After stable operation, the process can realize the wet oxidation reaction of sludge without additional heat source for heating the sludge except for the electricity consumption of the equipment.

[0006] For example, the patent document with the publication number CN113511788A and the name of an organic solid waste wet oxidation treatment system and its treatment process also adopts a similar process to fully recover most of the heat in the process.

[0007] However, the processes of the above-mentioned paper and patent have the following limitations: 1) The sludge needs to be diluted with water before it can enter the subsequent reactor, which increases investment costs and energy consumption; 2) Although the sludge was diluted before the process adopted the through-mixing cyclone tube high-efficiency low-resistance wet oxidation reaction technology, making the sludge less prone to clogging and scaling, in actual operation, regardless of the type of indirect heat exchanger used, the organic solids of the original sludge will continue to adhere to the heating surface when heated, which will lead to clogging of the indirect heat exchanger and a decrease in heat exchange efficiency, resulting in heat loss and system collapse; at the same time, the other side of the heating surface is the same, and the high-temperature sludge continues to adhere to the heating surface when cooling, causing the same problem.

[0008] For example, patent document CN111517443A discloses a combined hot water hydrolysis-catalytic wet oxidation technology for treating excess sludge. This process uses both direct heat exchangers (where the steam generated by flash evaporation preheats the sludge storage tank) and indirect heat exchangers (second heat exchangers, third heat exchangers, etc.), achieving full energy recovery and utilization. However, this process is not only complex and difficult to control, but also suffers from the problem of organic solids continuously adhering to the heating surface due to the indirect heat exchangers, affecting heat exchange efficiency. Similarly, this process also requires sludge dilution, reducing system processing efficiency and increasing energy consumption.

[0009] Therefore, for stable system operation, especially when the organic pollutant has a high solids content, it is necessary to completely solve the problem of scaling on the heat exchanger's heating surface. Indirect heat exchangers are therefore unsuitable for organic pollutants with high solids content. While direct heat exchange eliminates the need for heat exchange surfaces and avoids scaling-induced system instability, wet oxidation reactions generally require a batch reactor approach. Furthermore, the presence of the heat exchange system leads to multiple steps, often making it difficult to achieve full heat recovery and necessitating a large external heat source. Therefore, designing and developing a wet oxidation system with continuous operation capabilities and implementing a control method to ensure the smooth operation of each step is of great significance. Summary of the Invention

[0010] To address the aforementioned problems in the existing technology, the present invention aims to provide a novel wet oxidation system and its control method, which achieves efficient heat recovery and utilization. The external steam only provides a heat source during system startup, and stable operation can be achieved without subsequent heating. At the same time, this process is suitable for wet oxidation with high levels of inherent organic pollutants, reducing equipment investment and energy consumption, and improving system reliability.

[0011] The present invention provides the following technical solution: a novel wet oxidation system, comprising a wet oxidation reactor, wherein the material inlet of the wet oxidation reactor is connected to a storage silo and a feed pump for supplying material, and its material outlet is connected to a flash reactor, wherein the outlet of the flash reactor is connected in sequence to a cooling device and a treatment device via a discharge pump; the air inlet of the wet oxidation reactor is connected to an air compressor, and its exhaust outlet is connected to a waste gas treatment device; the exhaust outlet of the flash reactor is connected to the waste gas treatment device.

[0012] Furthermore, it also includes a high-temperature preheating reactor for preheating materials. The inlet of the high-temperature preheating reactor is connected to the storage silo via an organic pollutant feed pump, its outlet is connected to the inlet of the feed pump, and its exhaust port is connected to the waste gas treatment device. The exhaust port of the flash reactor is connected to the air inlet of the high-temperature preheating reactor via a waste gas inlet valve.

[0013] Furthermore, a wet oxidation reactor feed control valve is installed between the material inlet and the feed pump of the wet oxidation reactor; a wet oxidation reactor steam valve is connected to the steam inlet of the wet oxidation reactor; a wet oxidation reactor exhaust gas control valve is installed between the exhaust port and the exhaust gas treatment device of the wet oxidation reactor; a wet oxidation reactor pressurization valve is installed between the air inlet and the air compressor of the wet oxidation reactor; and a flash reaction control valve is installed between the material outlet of the wet oxidation reactor and the feed inlet of the flash reactor.

[0014] Furthermore, the flash reactor includes a first flash reactor and a second flash reactor arranged in parallel; the material outlet of the wet oxidation reactor is connected to the feed inlets of the first flash reactor and the second flash reactor respectively through a first flash reaction control valve and a second flash reaction control valve.

[0015] Furthermore, it also includes a low-temperature preheating reactor for preliminary preheating of materials, wherein the inlet of the low-temperature preheating reactor is connected to the storage silo via an organic pollutant feed pump, and its outlet is connected to the inlet of the high-temperature preheating reactor.

[0016] Furthermore, it also includes a third flash reactor and a fourth flash reactor; the outlets of the first flash reactor and the second flash reactor are respectively connected to the inlets of the third flash reactor and the fourth flash reactor through the first flash reactor outlet control valve and the second flash reactor outlet control valve, respectively; the outlets of the third flash reactor and the fourth flash reactor are respectively connected to the discharge pump through the third flash reactor outlet control valve and the fourth flash reactor outlet control valve, respectively.

[0017] Furthermore, a first flash reactor exhaust gas control valve is installed between the exhaust port of the first flash reactor and the inlet of the high-temperature preheating reactor; a second flash reactor exhaust gas control valve is installed between the exhaust port of the second flash reactor and the inlet of the high-temperature preheating reactor; a third flash reactor exhaust gas control valve is installed between the exhaust port of the third flash reactor and the inlet of the low-temperature preheating reactor; and a fourth flash reactor exhaust gas control valve is installed between the exhaust port of the fourth flash reactor and the inlet of the low-temperature preheating reactor.

[0018] Furthermore, a novel control method for a wet oxidation system includes the following steps: S1: Organic pollutants are transported to a wet oxidation reactor for heating and pressurization, so that the organic pollutants undergo a wet oxidation reaction at a set temperature, pressure and time. S2: After the wet oxidation reaction is completed, the material is introduced into the flash reactor for flash evaporation treatment; S3: Depressurize the flash reactor to allow the material to undergo a second flash reaction; S4: Discharge the flash-treated material and proceed with further processing.

[0019] Furthermore, a novel control method for a wet oxidation system includes the following steps: S1: After preheating, the organic pollutants are transported to a wet oxidation reactor for wet oxidation reaction; S2: After the wet oxidation reaction is completed, the material is alternately introduced into the first flash reactor and the second flash reactor; S3: Use the flash exhaust gas discharged from the first flash reactor and the second flash reactor to preheat the organic pollutants before they enter the wet oxidation reactor; S4: After the wet oxidation reactor completes the first flash evaporation, it undergoes oxygenation and pressure compensation. S5: By alternating the use of the first flash reactor and the second flash reactor, the wet oxidation reactor can be continuously fed and discharged.

[0020] A novel control method for a wet oxidation system includes the following steps: S1: Organic pollutants are preheated sequentially in a low-temperature preheating reactor and a high-temperature preheating reactor before entering a wet oxidation reactor for wet oxidation reaction; S2: After the wet oxidation reaction is completed, the material first enters the first flash reactor for the first flash evaporation; S3: Open the exhaust gas control valve of the first flash reactor. The material undergoes a second flash in the first flash reactor. The high-temperature flash exhaust gas discharged during the flash is introduced into the high-temperature preheating reactor to preheat the organic pollutants therein. S4: The material discharged from the first flash reactor enters the third flash reactor, where a third flash occurs due to the pressure difference upon entry. S5: Depressurize the inside of the third flash reactor. The material undergoes a fourth flash in the third flash reactor. The generated low-temperature flash waste gas is introduced into the low-temperature preheating reactor to preheat the organic pollutants therein. The material after four flash treatments is then discharged from the system. S6: After completing step S2, the wet oxidation reactor is oxygenated and pressure compensated, and the material is sequentially introduced into the second flash reactor and the fourth flash reactor to complete four flashes and heat recovery in a process corresponding to steps S3-S5. S7: By alternating the use of the first and third flash reactors with the second and fourth flash reactors, continuous feeding and discharging of the wet oxidation reactor is achieved, and heat recovery is made more efficient.

[0021] By employing the above-described technology, the beneficial effects of the present invention compared to the prior art are as follows: (1) Achieve continuous operation through a relatively simple process. The main equipment in this invention consists only of a high-temperature preheating reactor, a wet oxidation reactor, and a flash reactor. Through control methods, these devices can operate continuously and repeatedly, with almost no idle waiting time for the main equipment. This solves the drawbacks of the conventional wet oxidation process's "sequential batch" reaction, thereby improving the process system's processing efficiency and reducing investment and operating costs.

[0022] (2) Improved system reliability This invention employs a flash evaporation process, utilizing the secondary steam generated by the flash evaporation reaction for heat recovery. The secondary steam is directly introduced into the material, eliminating the problem of organic solid scaling caused by indirect heat exchangers and improving system reliability.

[0023] (3) Maintain self-sustaining reaction through heat recovery processes and control methods. This invention employs a reasonable number of main equipment such as high-temperature preheating reactors, wet oxidation reactors, and flash reactors, and sets control valves between each piece of equipment. Through corresponding control methods, heat is transferred back and forth between the equipment, so that the heat generated during the wet oxidation of organic pollutants just meets the operating requirements of the entire process system, thereby realizing the self-sustaining reaction of the system. Attached Figure Description

[0024] Figure 1 This is a flowchart of the control method of the system in Embodiment 1 of the present invention; Figure 2 This is a flowchart of the control method of the system in Embodiment 2 of the present invention; Figure 3This is a flowchart of the control method of the system in Embodiment 3 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain relevant details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions. Example

[0027] like Figure 1 As shown, a novel wet oxidation system includes a storage silo 1, a feed pump 2, a wet oxidation reactor 3, a flash reactor 4, a discharge pump 5, a cooling device 6, a treatment device 7, an air compressor 8, and a waste gas treatment device 9. Organic pollutants are temporarily stored in the storage silo 1 and then pumped into the wet oxidation reactor 3 via the feed pump 2. The reactor is heated to a high temperature and pressure using steam, and the air compressor 8 increases the reaction pressure and injects oxygen, bringing the organic pollutants to the minimum conditions for wet oxidation and initiating the reaction. During this process, the temperature and pressure in the wet oxidation reactor 3 continuously increase, thoroughly altering the properties of the organic pollutants. After wet oxidation, the organic pollutants are released under pressure differential and enter the flash reactor 4 for a flash reaction, further altering their properties. After the flash reaction, the organic pollutants release pressure and are pumped to the cooling device 6 and the treatment device 7 via the discharge pump 5. The pollutants are cooled in the cooling device 6 and then processed in the treatment device 7 for further treatment. When the organic pollutants are high-concentration organic wastewater, treatment device 7 is a wastewater treatment device, and the wastewater is discharged after meeting the standards. When the organic pollutants are solid wastes such as sludge, treatment device 7 is a plate and frame filter press, which presses the wastewater into sludge cakes for resource recovery. The waste gas released during the depressurization process of wet oxidation reactor 3 and during the flash evaporation process of flash reactor 4 enters waste gas treatment device 9 for treatment, and is discharged after meeting the standards.

[0028] Specifically, the system also includes a wet oxidation reactor feed control valve 11, a wet oxidation reactor steam valve 12, a flash reactor discharge control valve 13, a wet oxidation reactor exhaust gas control valve 14, a flash reactor exhaust gas control valve 15, a wet oxidation reactor pressurization valve 16, a flash reactor pressurization valve 17, a flash reaction control valve 18, and an exhaust gas main control valve 19.

[0029] Under PLC control, when organic pollutants are fed into the wet oxidation reactor 3 and reach the set liquid level under the control of the level gauge, the feed control valve 11 of the wet oxidation reactor is closed, and the steam valve 12 of the wet oxidation reactor is opened. At this time, all other valves connected to the wet oxidation reactor 3 are closed. The steam heats the organic pollutants in the wet oxidation reactor 3 to 200-240℃ (set according to the type of material). Then, the steam valve 12 of the wet oxidation reactor is closed, and the air compressor 8 and the pressurization valve 16 of the wet oxidation reactor are opened, so that the internal pressure of the wet oxidation reactor 3 rises to 2.5-3.5MPa (set according to the type of material). At this time, the air compressor 8 and the pressurization valve 16 of the wet oxidation reactor are closed and maintained for 45-90 minutes (set according to the type of material). During this time, oxygen continues to dissolve in the liquid, and the organic pollutants continue to undergo wet oxidation reaction, causing the temperature and pressure of the organic pollutants to continue to rise (the reaction temperature and pressure will vary depending on the material).

[0030] Due to the different characteristics of organic pollutants, the conditions for the oxidation of organic matter vary. In this embodiment, the design value for the organic matter oxidation rate is generally between 10% and 20%, and the corresponding reactor pressure design value also revolves around this range. When the organic matter oxidation rate exceeds the design value, the pressure of the wet oxidation reactor 3 will also exceed the set value (controlled by a pressure transmitter). At this time, by opening the exhaust gas control valve 14 and the main exhaust gas control valve 19 of the wet oxidation reactor, part of the pressure is released to control the pressure. After releasing the pressure to the set pressure of 2.5-3.5 MPa (set according to the type of material), the exhaust gas control valve 14 of the wet oxidation reactor is closed. During the wet oxidation reaction, the pressurization valve 17 of the flash reactor and the air compressor 8 are opened to pressurize the flash reactor 4 to 1-2 MPa and then closed to prevent the pressure difference between the wet oxidation reactor 3 and the flash reactor 4 from being too large and damaging the equipment during the flash reaction. After the wet oxidation reaction reaches the set time, the flash reaction control valve 18 is opened, and organic pollutants enter the flash reactor 4 from the wet oxidation reactor 3 under pressure differential, where a flash reaction occurs. Once the organic pollutants enter the flash reactor 4 and reach the set liquid level, the flash reaction control valve 18 is closed, and the flash reactor exhaust gas control valve 15 is opened, allowing further depressurization within the wet oxidation reactor 3 and flash reactor 4 to induce a second flash reaction. After the internal pressure drops to atmospheric pressure, the flash reactor exhaust gas control valve 15 is closed. Then, the flash reactor discharge control valve 13 is opened, and the discharge pump 5 is started to transport the organic pollutants to the cooling device 6 and the treatment device 7. Furthermore, because both the wet oxidation reactor 3 and the flash reactor 4 are under high temperature and high pressure, check valves are installed on the pipes directly connected to them to prevent backflow of organic pollutants.

[0031] Specifically, when organic pollutants undergo a flash reaction in flash reactor 4, the flash reactor exhaust gas control valve 15 and the wet oxidation reactor exhaust gas control valve 14 are opened, and the main exhaust gas valve 19 is closed. At this time, the flash exhaust gas enters the wet oxidation reactor 3 from flash reactor 4, preheating the organic pollutants to 120-180℃. This temperature is determined by the reaction temperature of the organic pollutants in the wet oxidation reactor 3. The higher the reaction temperature, the higher the heat energy of the exhaust gas generated after the second flash reaction in flash reactor 4, which in turn leads to a higher preheating temperature of the organic pollutants in the wet oxidation reactor 3. Through this control method, a large amount of heat released during the flash reaction is absorbed and reused by this process system, thereby reducing energy consumption.

[0032] The control method of the system in this embodiment is as follows: Step 1: The organic pollutants are fed into the wet oxidation reactor 3, heated to 200-240℃, and then oxygenated and pressurized to 2.5-3.5MPa to allow the organic pollutants to undergo a wet oxidation reaction for 45-90 minutes.

[0033] Step 2: After the wet oxidation reaction is completed, the organic pollutants enter the flash reactor 4 under the action of pressure difference and undergo a flash reaction; Step 3: Depressurize flash reactor 4 to allow the material to undergo a second flash reaction; Step 4: Discharge the flash-treated material and proceed with further processing. Example

[0034] like Figure 2 As shown, to improve reaction efficiency and reduce energy consumption, a novel wet oxidation system, compared to Example 1, adds an organic pollutant feed pump 20, a high-temperature preheating reactor 21, a preheating reactor steam valve 22, a high-temperature preheating reactor exhaust gas outlet valve 23, and a high-temperature preheating reactor exhaust gas inlet valve 24. Simultaneously, all flash reaction-related equipment is provided in two sets, including two flash reactors (first flash reactor 41 and second flash reactor 42), two flash reactor discharge control valves (first flash reactor discharge control valve 131 and second flash reactor discharge control valve 132), two flash reactor exhaust gas control valves (first flash reactor exhaust gas control valve 151 and second flash reactor exhaust gas control valve 152), two flash reactor pressurization valves (first flash reactor pressurization valve 171 and second flash reactor pressurization valve 172), and two flash reaction control valves (first flash reaction control valve 181 and second flash reaction control valve 182).

[0035] The control method of the system in this embodiment is as follows: In the first step, the organic pollutants are preheated by entering the high-temperature preheating reactor 21 through the organic pollutant feed pump 20. The feed rate is controlled by the level gauge of the high-temperature preheating reactor 21.

[0036] The second step involves opening the preheating reactor steam valve 22 during system startup to preheat the reactor using steam. During normal system operation, the residual heat from the wet oxidation reactor 3 and the two flash reactors is used for preheating. The preheating temperature is between 100-160℃ (determined by the reaction temperature of the organic pollutants in the wet oxidation reactor 3; the higher the reaction temperature, the higher the preheating temperature).

[0037] The third step involves feeding the material into the wet oxidation reactor 3 via the feed pump 2. The control method in the wet oxidation reactor 3 is similar to that in Example 1. The control method for this process step is a time of 45-90 minutes (set according to the type of material).

[0038] In this process, the use of steam to heat the organic pollutants in the wet oxidation reactor 3 is only during the system startup phase. Once the system is running stably, it can maintain a self-sustaining reaction and does not require steam to heat the organic pollutants again.

[0039] Fourth step: After the organic pollutants have completed the wet oxidation reaction process, the first flash reaction control valve 181 is opened, and the organic pollutants are allowed to enter the first flash reactor 41 under the action of pressure difference. The control method for this process step is the liquid level of the first flash reactor 41. After this process step is completed, the first flash reaction control valve 181 is closed.

[0040] Meanwhile, in order to ensure the continuous operation of the new wet oxidation process, the temperature of organic pollutants in the wet oxidation reactor 3 also needs to be controlled. The set value is 10-20°C higher than the minimum condition for wet oxidation reaction, so as to prevent newly introduced organic pollutants from failing to undergo wet oxidation, which would require the system to be supplemented with steam to maintain normal operation.

[0041] Fifth step, open the exhaust gas inlet valve 24 of the high temperature preheating reactor and the exhaust gas control valve 151 of the first flash reactor to make the first flash reactor 41 undergo a second flash reaction, and the flash exhaust gas is discharged into the high temperature preheating reactor 21 to preheat the organic pollutants.

[0042] Step 6: After the first flash reactor 41 completes the second flash reaction, the exhaust gas control valve 151 of the first flash reactor is closed, and the discharge control valve 131 and discharge pump 5 of the first flash reactor are opened to transport the organic pollutants to the cooling device 6 and the treatment device 7.

[0043] Step seven occurs after step four and begins simultaneously with step five. Due to the continuous discharge during step four, the pressure in wet oxidation reactor 3 decreases. At this point, air compressor 8 and the wet oxidation reactor pressurization valve 16 are opened to quickly replenish the pressure in wet oxidation reactor 3. The control method for this step is to pressurize the wet oxidation reactor 3 once the set lower pressure limit is reached. This step takes only 1-5 minutes and does not affect the continuous operation of the entire process.

[0044] Step 8: Open the air compressor 8 and the flash reactor pressurization valve 172 to pre-pressurize the second flash reactor 42 to prevent equipment damage during feeding. The control method for this process step is to stop pressurizing once the pressure of the second flash reactor 42 reaches the set pressure.

[0045] Step 9: Close the pressurization valve 16 of the wet oxidation reactor and the pressurization valve 172 of the flash reactor (close them after reaching the set pressure). After both control valves are closed, turn off the air compressor 8.

[0046] Step 10: Open the first flash reaction control valve 182 to allow organic pollutants to enter the second flash reactor 42 under the action of pressure difference. The control method for this process step is the liquid level of the second flash reactor 42. After this process step is completed, close the first flash reaction control valve 182.

[0047] In the above process steps, by designing the volume of each reactor and matching it with the reaction time, the total time of steps five and six is ​​made comparable to the total time of steps seven and ten, so that the whole new wet oxidation process has the best reaction sequence and efficiency.

[0048] Step 11 begins the same way as step 5, except that in step 5 the second flash reaction occurs in the first flash reactor 41, while in this process step the second flash reaction occurs in the second flash reactor 42.

[0049] Therefore, the method in this embodiment enables the continuous operation of the entire wet oxidation process and achieves efficient heat recovery and utilization. The external steam only provides heat when the system is started up, and stable operation can be achieved without subsequent heating. At the same time, this process is suitable for wet oxidation with high content of organic pollutants (10%-20% solids content), which reduces equipment investment and energy consumption and improves system reliability. Example

[0050] When the heat generated by organic pollutants during the wet oxidation reaction is low, this invention provides a more refined heat recovery process. According to the balance formula "Heat generated by wet oxidation = Heat discharged from organic pollutants + Heat discharged from preheating reactor exhaust gas + Small amount of system heat dissipation," when the heat generated by wet oxidation decreases, it is necessary to reduce the heat discharged from organic pollutants and the heat discharged from preheating reactor exhaust gas. Therefore, this invention provides a process and control method to improve heat recovery efficiency, which will be described in detail below.

[0051] like Figure 3 As shown, compared to Example 2, the following are added: a low-temperature preheating reactor 31, a preheating organic pollutant transfer pump 32, two secondary flash reactors (a third flash reactor 43 and a fourth flash reactor 44), a low-temperature preheating reactor exhaust valve 33, a low-temperature preheating reactor steam valve 34, two secondary flash reactor discharge control valves (a third flash reactor discharge control valve 133 and a fourth flash reactor discharge control valve 134), two secondary flash reactor exhaust control valves (a third flash reactor exhaust control valve 153 and a fourth flash reactor exhaust control valve 154), and two secondary flash reaction control valves (a third flash reaction control valve 183 and a fourth flash reaction control valve 184).

[0052] The control method of the system in this embodiment is as follows: In the first step, organic pollutants are fed into the low-temperature preheating reactor 31 via the organic pollutant feed pump 20, and the feed rate is controlled by the level gauge of the low-temperature preheating reactor 31.

[0053] The second step involves opening the steam valve 34 of the low-temperature preheating reactor during system startup to preheat it with steam until the set temperature is reached, at which point the valve is closed. During normal system operation, the residual heat from the secondary flash reactor is used for preheating; in this case, the steam valve 34 remains closed. The preheating temperature is between 80-100℃. Insoluble waste gas is discharged through the waste gas valve 33 of the low-temperature preheating reactor to the waste gas treatment device 9 for treatment.

[0054] Step 3: Turn on the preheating organic pollutant transfer pump 32 to transport the preheated organic pollutants to the high-temperature preheating reactor 21. The feed rate is controlled by the level gauge of the high-temperature preheating reactor 21.

[0055] Step 4: When starting the entire system, open the steam valve 22 of the preheating reactor to preheat the organic pollutants in the high-temperature preheating reactor 21 with steam. Close the valve after preheating to the set temperature. When the system is running normally, preheat it using the waste heat from the primary flash reactor. During this time, the steam valve 22 of the preheating reactor remains closed. The preheating temperature is 100-160℃. Insoluble waste gas is discharged to the waste gas treatment device 9 through the waste gas outlet valve 23 of the high-temperature preheating reactor for treatment.

[0056] Step 5: Open the feed pump 2 and the wet oxidation reactor feed control valve 11 to transport the preheated organic pollutants to the wet oxidation reactor 3.

[0057] Step 6: When starting the entire system, open the steam valve 12 of the wet oxidation reactor to heat the organic pollutants in the wet oxidation reactor 3 with steam. At the same time, open the pressurization valve 16 of the wet oxidation reactor and the air compressor 8 to introduce air into the wet oxidation reactor 3. The wet oxidation reaction is carried out under high temperature and high pressure conditions. The reaction temperature is 200-240℃, the reaction pressure is 2.5-3.5MPa, and the reaction time is 45-90 minutes.

[0058] In this process, the steam heating of organic pollutants in the wet oxidation reactor 3 is only used during the system startup phase. When the system is running stably, it can maintain a self-sustaining reaction and does not need to use steam to heat the organic pollutants. At this time, the steam valve 12 of the wet oxidation reactor is always closed.

[0059] Step 7: After the wet oxidation reaction is completed, open the first flash reaction control valve 181 to transport the reacted material to the first flash reactor 41. The material immediately undergoes its first flash evaporation due to the pressure difference. After the first flash reaction is completed, close the first flash reaction control valve 181 and open the first flash reactor exhaust gas control valve 151 and the high-temperature preheating reactor exhaust gas inlet valve 24 to allow the material to undergo a second flash reaction. The flash exhaust gas enters the high-temperature preheating reactor 21 to preheat the organic pollutants, as detailed in Step 4.

[0060] Step 8: Close the exhaust gas control valve 151 of the first flash reactor, open the discharge control valve 131 of the first flash reactor and the third flash reaction control valve 183, and transport the material to the third flash reactor 43; when the material enters, a third flash occurs due to the pressure difference.

[0061] Step 9: Close the discharge control valve 131 of the first flash reactor and the control valve 183 of the third flash reaction, and open the exhaust gas control valve 153 of the third flash reactor to allow the material to undergo a fourth flash reaction in the third flash reactor 43. The flash exhaust gas is discharged into the low-temperature preheating reactor 31 to preheat the organic pollutants. See Step 2 for details.

[0062] Step 10: After the third flash reactor 43 completes the fourth flash reaction, the exhaust gas control valve 153 of the third flash reactor is closed, and the discharge control valve 133 and discharge pump 5 of the third flash reactor are opened to transport the organic pollutants to the cooling device 6 and the treatment device 7.

[0063] Step 11: After completing step 7, turn on the air compressor 8 and the wet oxidation reactor pressurization valve 16 to compensate for the pressure in the wet oxidation reactor 3. This step takes 1-5 minutes to complete.

[0064] Step 12: Close the pressure valve, and the material newly entering the wet oxidation reactor 3 will undergo a wet oxidation reaction.

[0065] Step 13: After the wet oxidation reaction is completed, the material enters the second flash reactor 42 for the first flash evaporation.

[0066] Step 14: Open the exhaust gas control valve 152 of the second flash reactor and the exhaust gas inlet valve 24 of the high-temperature preheating reactor to make the second flash reactor 42 undergo a second flash, and the exhaust gas is discharged into the high-temperature preheating reactor 21 (corresponding to step 7).

[0067] Step 15: After completing the second flash evaporation, close the exhaust gas control valve 152 of the second flash reactor, open the discharge control valve 132 of the second flash reactor and the fourth flash reaction control valve 184, and transport the material to the fourth flash reactor 44 for the third flash evaporation (corresponding to step 8).

[0068] Step 16: Close the discharge control valve 132 of the second flash reactor and the control valve 184 of the fourth flash reaction, and open the exhaust gas control valve 154 of the fourth flash reactor to allow the material to undergo the fourth flash reaction in the fourth flash reactor 44. The flash exhaust gas is discharged into the low-temperature preheating reactor 31 to preheat the organic pollutants (corresponding to step 9).

[0069] Step seventeen: Close the exhaust gas control valve 154 of the fourth flash reactor, and open the discharge control valve 134 and discharge pump 5 of the fourth flash reactor to transport the organic pollutants to the cooling device 6 and the treatment device 7. This completes a full alternating cycle and realizes the continuous treatment of organic pollutants and the continuous operation of the wet oxidation process.

[0070] Therefore, through this embodiment, on the basis of achieving continuous operation of the entire wet oxidation process, for organic pollutants with lower heat, by increasing the number of heat recovery stages and assisting with more refined control methods, the efficient recovery and utilization of heat is also achieved. The external steam only provides a heat source when the system is started, and stable operation can be achieved without subsequent heating.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel wet oxidation system, characterized in that, The wet oxidation reactor (3) is connected to a material storage silo (1) and a feed pump (2) at its material inlet and to a flash reactor (4) at its material outlet. The outlet of the flash reactor (4) is connected to a cooling device (6) and a treatment device (7) in sequence via a discharge pump (5). The air inlet of the wet oxidation reactor (3) is connected to an air compressor (8) and the exhaust outlet is connected to a waste gas treatment device (9). The exhaust outlet of the flash reactor (4) is connected to the waste gas treatment device (9).

2. The novel wet oxidation system according to claim 1, characterized in that, It also includes a high-temperature preheating reactor (21) for preheating materials. The inlet of the high-temperature preheating reactor (21) is connected to the storage silo (1) through an organic pollutant feed pump (20), its outlet is connected to the inlet of the feed pump (2), and its exhaust port is connected to the waste gas treatment device (9). The exhaust port of the flash reactor (4) is connected to the air inlet of the high-temperature preheating reactor (21) through the high-temperature preheating reactor waste gas inlet valve (24).

3. The novel wet oxidation system according to claim 1, characterized in that, A wet oxidation reactor feed control valve (11) is provided between the material inlet of the wet oxidation reactor (3) and the feed pump (2); a wet oxidation reactor steam valve (12) is connected to the steam inlet of the wet oxidation reactor (3); a wet oxidation reactor exhaust control valve (14) is provided between the exhaust port of the wet oxidation reactor (3) and the exhaust gas treatment device (9); a wet oxidation reactor pressurization valve (16) is provided between the air inlet of the wet oxidation reactor (3) and the air compressor (8); a flash reaction control valve (18) is provided between the material outlet of the wet oxidation reactor (3) and the feed inlet of the flash reactor (4).

4. A novel wet oxidation system according to claim 2 or 3, characterized in that, The flash reactor (4) includes a first flash reactor (41) and a second flash reactor (42) arranged in parallel; the material outlet of the wet oxidation reactor (3) is connected to the feed inlets of the first flash reactor (41) and the second flash reactor (42) through the first flash reaction control valve (181) and the second flash reaction control valve (182), respectively.

5. A novel wet oxidation system according to claim 4, characterized in that, It also includes a low-temperature preheating reactor (31) for preliminary preheating of materials. The inlet of the low-temperature preheating reactor (31) is connected to the storage silo (1) via an organic pollutant feed pump (20), and its outlet is connected to the inlet of the high-temperature preheating reactor (21).

6. A novel wet oxidation system according to claim 5, characterized in that, It also includes a third flash reactor (43) and a fourth flash reactor (44); the outlets of the first flash reactor (41) and the second flash reactor (42) are connected to the inlets of the third flash reactor (43) and the fourth flash reactor (44) respectively through the first flash reactor discharge control valve (131) and the second flash reactor discharge control valve (132); the outlets of the third flash reactor (43) and the fourth flash reactor (44) are connected to the discharge pump (5) respectively through the third flash reactor discharge control valve (133) and the fourth flash reactor discharge control valve (134).

7. A novel wet oxidation system according to claim 6, characterized in that, A first flash reactor exhaust gas control valve (151) is provided between the exhaust port of the first flash reactor (41) and the air inlet of the high-temperature preheating reactor (21); a second flash reactor exhaust gas control valve (152) is provided between the exhaust port of the second flash reactor (42) and the air inlet of the high-temperature preheating reactor (21); a third flash reactor exhaust gas control valve (153) is provided between the exhaust port of the third flash reactor (43) and the air inlet of the low-temperature preheating reactor (31); and a fourth flash reactor exhaust gas control valve (154) is provided between the exhaust port of the fourth flash reactor (44) and the air inlet of the low-temperature preheating reactor (31).

8. The control method for a novel wet oxidation system according to claim 1, characterized in that, Includes the following steps: S1: The organic pollutants are transported to the wet oxidation reactor (3) for heating and oxygenation and pressurization, so that the organic pollutants undergo wet oxidation reaction at a set temperature, pressure and time. S2: After the wet oxidation reaction is completed, the material is introduced into the flash reactor (4) for flash treatment; S3: Depressurize the flash reactor (4) to allow the material to undergo a second flash reaction; S4: Discharge the flash-treated material and proceed with further processing.

9. The control method for a novel wet oxidation system according to claim 5, characterized in that, Includes the following steps: S1: After preheating, the organic pollutants are transported to the wet oxidation reactor (3) for wet oxidation reaction; S2: After the wet oxidation reaction is completed, the material is alternately introduced into the first flash reactor (41) and the second flash reactor (42); S3: The flash exhaust gas discharged from the first flash reactor (41) and the second flash reactor (42) is used to preheat the organic pollutants before they enter the wet oxidation reactor (3); S4: After the first flash evaporation is completed, the wet oxidation reactor (3) is oxygenated and pressure compensated; S5: By alternating the use of the first flash reactor (41) and the second flash reactor (42), the wet oxidation reactor (3) can be continuously fed and discharged.

10. The control method for a novel wet oxidation system according to claim 7, characterized in that, Includes the following steps: S1: Organic pollutants are preheated sequentially by a low-temperature preheating reactor (31) and a high-temperature preheating reactor (21) before entering a wet oxidation reactor (3) for wet oxidation reaction; S2: After the wet oxidation reaction is completed, the material first enters the first flash reactor (41) for the first flash evaporation; S3: Open the exhaust gas control valve (151) of the first flash reactor. The material undergoes a second flash in the first flash reactor (41). The high-temperature flash exhaust gas discharged during the flash is introduced into the high-temperature preheating reactor (21) to preheat the organic pollutants therein. S4: The material discharged from the first flash reactor (41) enters the third flash reactor (43), and a third flash occurs due to the pressure difference when the material enters; S5: Depressurize the inside of the third flash reactor (43), and the material undergoes a fourth flash in the third flash reactor (43). The generated low-temperature flash waste gas is introduced into the low-temperature preheating reactor (31) to preheat the organic pollutants therein. Then the material after four flash treatments is discharged from the system. S6: After completing step S2, the wet oxidation reactor (3) is oxygenated and pressure compensated, and the material is sequentially introduced into the second flash reactor (42) and the fourth flash reactor (44) to complete four flashes and heat recovery in accordance with the process corresponding to steps S3-S5. S7: By alternating the use of the first and third flash reactors with the second and fourth flash reactors, continuous feeding and discharging of the wet oxidation reactor (3) are achieved, and heat is recovered more efficiently.

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