Wet oxidation wastewater treatment system and method

Abstract

The invention discloses a wet oxidation wastewater treatment system and method. The system comprises a multi-stage centrifugal pump; the preheater is positioned at the downstream of the multi-stage centrifugal pump; the heater is positioned at the downstream of the preheater; and a reactor downstream of the heater. The rotating speed of the multi-stage centrifugal pump is far lower than 6600 rpm or above of a traditional high-speed pump, noise and vibration can be effectively reduced, meanwhile, loss of a motor bearing is delayed, and therefore the equipment maintenance cost is reduced, and the stability and efficiency of a wet oxidation method can be improved. And meanwhile, the tubular heat exchanger is adopted, so that the explosion risk is reduced, the temperature of the wastewater is increased, the steam consumption of a subsequent heater is greatly reduced, 2.4 tons of 3.2 MPa steam can be saved per hour per 20m < 3 > of wastewater according to actual operation, and huge economic benefits can be created every year. The Q235B and TA9 explosive composite board reactor is adopted, the comprehensive performance is better, and the long-term operation cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a wastewater treatment system and method by wet oxidation method. Background Art

[0002] At present, most of the high-pressure pumps used in the traditional wet oxidation wastewater process are high-speed pumps, and their rotational speeds are often above 6600 rpm. Because of the relatively high rotational speed, obvious noise and vibration will occur during the operation of the high-speed pump, and it will accelerate the wear rate of the motor bearings. Therefore, not only does the cost required for the maintenance of the high-speed pump equipment increase, but it will also have an adverse impact on the stability and efficiency of the process. Moreover, when the high-speed pump is used to handle wastewater media containing solid particles or high viscosity, the pumping effect is not good, and it is very easy to cause blockage or wear and other conditions. Therefore, for the traditional wet oxidation wastewater process, there is an urgent need to find a more efficient, stable and cost-reducing solution in the selection of high-pressure pumps.

[0003] A multistage centrifugal pump is a combination of two or more centrifugal pumps with the same function. In terms of the fluid passage structure, it is manifested that the medium pressure relief port of the first stage is communicated with the inlet of the second stage, and the medium pressure relief port of the second stage is communicated with the inlet of the third stage. Such a series connection mechanism forms a multistage centrifugal pump. A multistage centrifugal pump consists of multiple series-connected impellers, diffusers (or volutes), pump shafts, balance devices (such as balance disks / drums), sealing rings and pump casings (sectional or split). Each impeller is installed on the same shaft, and when the liquid flows through each stage of the impeller in turn, the energy is superimposed stage by stage. Summary of the Invention

[0004] To improve the above technical problems, the present invention provides a wastewater treatment system by wet oxidation method, which includes a multistage centrifugal pump;

[0005] A preheater located downstream of the multistage centrifugal pump;

[0006] A heater located downstream of the preheater;

[0007] And a reactor located downstream of the heater.

[0008] According to an embodiment of the present invention, the multistage centrifugal pump adopts 10-stage impellers.

[0009] In some embodiments, the motor of the multistage centrifugal pump is added with frequency conversion to adjust the rotational speed. For example, the rotational speed of the multistage centrifugal pump is 1400 - 2980 rpm, such as 1400 rpm, 1500 rpm, 1800 rpm, 2000 rpm, 2500 rpm or 2980 rpm.

[0010] In some embodiments, the multistage centrifugal pump includes a multistage impeller and a pump body. The pump body includes a suction section, a discharge section, and a pump shaft. Five impellers are installed inside each of the suction section and the discharge section, and the impellers are all installed on the pump shaft. Adjacent two impellers are fixed against loosening by screws. A partition is provided between two adjacent impellers of the suction section and the discharge section. And along the wastewater flow direction, the fifth-stage impeller of the suction section and the first-stage impeller of the discharge section are connected through a balance pipe.

[0011] In some embodiments, the impeller directions of the suction section and the discharge section are opposite.

[0012] The wastewater pressurized in the forward direction by the five-stage impeller of the suction section is transported through the balance pipe to the last-stage impeller of the discharge section for further pressurization (i.e., the pressurization method of the discharge section is opposite to the forward pressurization force of the suction section), and finally flows out from the fifth-stage impeller of the discharge section.

[0013] In some embodiments, the partition is provided with a reflux hole. There are reflux holes on the partitions between the discharge section and the suction section, and the reflux holes can be used to solve the problem that the equipment stops due to backpressure at the outlet of the discharge section (similar to a safety valve).

[0014] In some embodiments, the suction section is provided with a fluid inlet.

[0015] In some embodiments, the discharge section is provided with a fluid outlet.

[0016] In some embodiments, sealing members are respectively provided at both ends of the pump shaft.

[0017] During the use of existing multistage pumps, defects such as damage to the pump due to excessive flow rate are likely to occur. The multistage centrifugal pump of the present invention controls the output of the pump by adding a frequency converter to the motor.

[0018] According to the embodiments of the present invention, the preheater uses a shell-and-tube heat exchanger.

[0019] In some embodiments, the tube-side medium of the preheater is the wastewater pressurized by the multistage centrifugal pump. For example, the wastewater includes 20% brine, 4000 - 5000 ppm of organic matter, excessive oxygen, a catalyst (preferably a catalyst containing copper ions, exemplified by copper chloride), and hydrochloric acid, etc.

[0020] In some embodiments, the shell-side medium of the preheater comes from the water after the wet oxidation reaction of the reactor is completed. For example, it contains 20% brine, excessive oxygen, a catalyst (preferably a catalyst containing copper ions, exemplified by copper chloride), and hydrochloric acid, etc.

[0021] In some embodiments, the inlet of the tube-side medium of the preheater is located at the bottom of the tube bundle, and the outlet of the tube-side medium is located at the top of the tube bundle. By adopting the design of low inlet and high outlet, the buoyancy effect is utilized to promote the upward movement of oxygen with the fluid to discharge the tube side.

[0022] In some embodiments, the tube side of the preheater is a straight tube or a U-shaped tube. There are no dead ends, which helps the flow velocity of the tube-side medium in the tube bundle to be uniform (turbulent state) to inhibit the formation of carbon deposition.

[0023] According to the embodiments of the present invention, the reactor uses a Q235B and TA9 explosion composite plate.

[0024] Explosive Cladding is an advanced composite technology that uses the high-pressure shock wave generated by explosive explosion to cause plastic deformation of two or more metal plates instantaneously and achieve metallurgical bonding. Through the instantaneous high pressure (up to tens of thousands of megapascals) and high-speed impact (1000 - 3000 m / s) generated by explosive explosion, the clad metal (such as titanium, stainless steel) and the base metal (such as carbon steel) collide at high speed in an extremely short time (microsecond level). The metal at the collision interface generates heat due to severe plastic deformation (the local temperature can reach 30% - 50% of the melting point of the metal), forming a metallurgical bonding layer. The metal surface oxides and impurities are removed by the high-speed jet during the collision, forming a clean bonding surface. Under the action of the shock wave, a periodic waveform structure (the wavelength is usually 0.1 - 2 mm) is formed at the interface, increasing the bonding area and improving the shear resistance. Atomic diffusion and local micro-melting achieve metallurgical connection at the interface, and the bonding strength is close to that of the base material.

[0025] According to the embodiments of the present invention, the reactor further includes the components required for catalytic wet air oxidation reaction. The components include but are not limited to one or more selected from the intake unit, outlet unit, feed unit, discharge unit, and instrument unit. Those skilled in the art should understand that when the reactor is provided with the above components, the components should not affect the airtightness of the reactor. For this purpose, the components can be connected to the reactor by welding, flange, and / or pipeline methods. It should be understood that the structures and functions of the components are known in the art. For example, the intake unit and the outlet unit can be used to introduce oxygen and / or air to enable the catalytic wet air oxidation reaction to proceed. The feed unit can be used to introduce the wastewater to be treated, and the discharge unit can be used to discharge the reaction products or unwanted residues. The instrument unit can be used to display or monitor the process parameters of the reactor.

[0026] In some embodiments, the instrument unit includes a temperature sensor, a pressure sensor, a TOC on-line analyzer, an on-line pH meter, an on-line copper ion detector, and a liquid level sensor. Preferably, the temperature sensor, the pressure sensor, and the liquid level sensor are interlocked.

[0027] According to an embodiment of the present invention, the treatment system further includes a wastewater storage unit located upstream of the multistage centrifugal pump. For example, the wastewater storage unit is a wastewater tank.

[0028] According to an embodiment of the present invention, the treatment system further includes a steam delivery unit located upstream of the heater, and the steam delivery unit is connected to the heater.

[0029] According to an embodiment of the present invention, the treatment system further includes a flash tank located downstream of the heater, and the inlet of the flash tank is connected to the condensate outlet of the heater.

[0030] The present invention also provides a method for treating wastewater, including subjecting the wastewater to catalytic wet air oxidation reaction in the above treatment system to achieve wastewater purification.

[0031] According to an embodiment of the present invention, the wastewater is pressurized by a multistage centrifugal pump and then transported to a preheater. For example, the wastewater includes 20% brine, 4000 - 5000 ppm of organic matter, excess oxygen, a catalyst (preferably a catalyst containing copper ions, exemplified by copper chloride), and hydrochloric acid, etc.

[0032] According to an embodiment of the present invention, the rotational speed of the multistage centrifugal pump is 1400 - 2980 rpm, such as 1400 rpm, 1500 rpm, 1800 rpm, 2000 rpm, 2500 rpm, or 2980 rpm.

[0033] According to an embodiment of the present invention, the method includes pressurizing the wastewater in the wastewater storage unit by a multistage centrifugal pump and then transporting it to the preheater for preheating, then entering the heater for heating, and then entering the reactor for catalytic wet air oxidation reaction to achieve wastewater purification.

[0034] According to an embodiment of the present invention, the operating temperature of the reactor is between 150 - 300 °C, such as 150 °C, 180 °C, 200 °C, 220 °C, 240 °C, 270 °C, 280 °C, or 300 °C, and the pressure of the reactor is 4 - 7 MPa.

[0035] According to an embodiment of the present invention, during the catalytic wet air oxidation reaction, the pH value of the wastewater is between 0.8 - 1.4, exemplified by 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or 1.4.

[0036] According to an embodiment of the present invention, the catalyst used in the catalytic wet air oxidation reaction can be a catalyst used in the known catalytic wet air oxidation method in the art, preferably a catalyst containing copper ions. For example, the copper ion content is between 1000 - 3000 ppm.

[0037] Advantages of the present invention:

[0038] (1) The present invention applies a multistage centrifugal pump (preferably with 10 impellers and a rotational speed set at 1400 - 2980 rpm) to the wet oxidation process for wastewater treatment. The rotational speed of the multistage centrifugal pump in the present invention is much lower than the above 6600 rpm of traditional high-speed pumps. By reducing the rotational speed, noise and vibration can be effectively reduced, and at the same time, the wear of the motor bearings can be delayed, thereby reducing the equipment maintenance cost. The multistage centrifugal pump of the present invention can improve the stability and efficiency of the wet oxidation method. In practical applications, the multistage centrifugal pump of the present invention not only performs excellently in treating wastewater containing solid particles and high viscosity, but also maintains stable performance and low maintenance requirements during long-term operation. Compared with traditional high-speed pumps, the multistage centrifugal pump of the present invention has significant advantages in reducing energy consumption and extending service life.

[0039] (2) The present invention adopts a shell-and-tube heat exchanger. The tube-side medium is the wastewater pressurized by the multistage centrifugal pump, and the shell-side medium is the water after the wet oxidation reaction in the reactor is completed. The tube-side adopts a low-inlet (bottom) and high-outlet (top) layout, and uses the buoyancy effect to promote the oxygen to rise with the fluid and discharge from the tube-side. The tube-side is a straight tube / U-shaped tube, without dead ends, and the flow velocity is uniform (turbulent state). Therefore, carbon deposition formation can be inhibited. The preheater of the present invention reduces the explosion risk, increases the wastewater temperature and greatly reduces the steam consumption of the subsequent heater. According to actual operation, for every 20m 3 of wastewater, 2.4 tons of 3.2 MPa steam can be saved per hour, creating huge economic benefits every year.

[0040] (3) The present invention adopts a Q235B and TA9 explosion-clad plate reactor. Compared with the traditional loose-lined plate reactor, under the working conditions of 6.6 MPa and 280 °C, the pressure-resistant life of the explosion-clad plate of the present invention can be as high as 100,000 hours, the weld strength is high (the weld strength retention rate ≥ 90%), and the thermal fatigue resistance is strong (the interface strength is as high as 200 - 400 MPa (shear)), with better comprehensive performance and a significant reduction in long-term operation costs. Description of the drawings

[0041] Figure 1 is a schematic structural diagram of a wet oxidation method wastewater treatment system of the present invention;

[0042] Figure 2 is a schematic structural diagram of the multistage centrifugal pump;

[0043] In the figure: 1. Wastewater storage unit; 2. Multistage centrifugal pump; 201. Pump body; 202. Impeller; 203. Pump shaft; 204. Bearing box; 205. Seal; 206. Fluid inlet; 207. Fluid outlet; 208. Balance pipe; 209. Return hole; 3. Preheater; 4. Heater; 5. Reactor; 6. Steam delivery unit; 7. Flash tank. Detailed implementation mode

[0044] The technical solution of the present invention will be further described in detail below in combination with specific embodiments. It should be understood that the following embodiments are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0045] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0046] Embodiment 1

[0047] Refer to Figure 1 , a wet oxidation method wastewater treatment system, which includes a multistage centrifugal pump 2;

[0048] A preheater 3 located downstream of the multistage centrifugal pump 2;

[0049] A heater 4 located downstream of the preheater 3;

[0050] And a reactor 5 located downstream of the heater 4.

[0051]

Multistage centrifugal pump

[0052] The multistage centrifugal pump 2 adopts 10-stage impellers 202, and the motor of the multistage centrifugal pump 2 is equipped with variable frequency to adjust the speed. For example, the speed of the multistage centrifugal pump 2 is 2980 rpm.

[0053] The multistage centrifugal pump 2 includes multistage impellers 202 and a pump body 201. The pump body 201 includes: a suction section, a discharge section and a pump shaft 203. Five impellers 202 are installed inside each of the suction section and the discharge section. The impellers 202 are all installed on the pump shaft 203, and adjacent two impellers 202 are fixed and loosened by screws; a partition is provided between the two adjacent impellers 202 of the suction section and the discharge section, and a return hole 209 is provided on the partition; and along the wastewater flow direction, the fifth-stage impeller 202 of the suction section and the first-stage impeller 202 of the discharge section are connected through a balance pipe 208.

[0054] The directions of the impellers 202 of the suction section and the discharge section are opposite.

[0055] The wastewater pressurized in the forward direction by the 5-stage impeller 202 in the suction section is conveyed to the impeller at the end of the discharge section for further pressurization by using the balance pipe 208 (i.e., the pressurization method in the discharge section is opposite to the forward pressurization force in the suction section), and finally flows out from the fifth-stage impeller 202 in the discharge section. There are reflux holes 209 on the partition between the discharge section and the suction section, and the reflux holes 209 can be used to solve the problem that the equipment stops due to backpressure at the outlet in the discharge section (similar to a safety valve).

[0056] The suction section is provided with a fluid inlet 206, and the discharge section is provided with a fluid outlet 207.

[0057] Seals 205 are respectively provided at both ends of the pump shaft 203.

[0058]

Preheater

[0059] The preheater 3 uses a shell-and-tube heat exchanger (double-tube-pass double-shell-pass fixed-tube-sheet heat exchanger) produced by Morimatsu (Jiangsu) Heavy Industry Co., Ltd.

[0060] The tube-side medium of the preheater 3 is the wastewater pressurized by the multistage centrifugal pump 2. For example, the wastewater includes 20% brine, 4000 - 5000 ppm of organic matter, excessive oxygen, a catalyst (preferably a catalyst containing copper ions, exemplified by copper chloride), and hydrochloric acid, etc.

[0061] The shell-side medium of the preheater 3 comes from the water after the wet oxidation reaction in the reactor. For example, it contains 20% brine, excessive oxygen, a catalyst (preferably a catalyst containing copper ions, exemplified by copper chloride), and hydrochloric acid, etc.

[0062] The inlet of the tube-side medium of the preheater 3 is located at the bottom of the tubes, and the outlet of the tube-side medium is located at the top of the tubes. By adopting the design of low inlet and high outlet, the buoyancy effect is used to promote the rise of oxygen with the fluid and discharge it from the tube side.

[0063] The tube side of the preheater 3 is a straight tube or a U-shaped tube. There are no dead ends, which helps the tube-side medium to flow uniformly in the tubes (in a turbulent state) to inhibit carbon deposition.

[0064]

Reactor

[0065] The reactor 5 uses an explosion composite plate made of Q235B and TA9 and manufactured by Morimatsu (Jiangsu) Heavy Industry Co., Ltd.

[0066] The reactor 5 also includes the components required for the catalytic wet oxidation reaction. The components include but are not limited to one or more selected from the intake unit, outlet unit, feed unit, discharge unit, and instrument unit. When the reactor is provided with the above components, the components can be connected to the reactor by welding, flange, and / or pipeline methods. It should be understood that the structures and functions of the components are known in the art.

[0067] The intake unit and the outlet unit can be used to introduce oxygen and / or air to enable the catalytic wet oxidation reaction to proceed.

[0068] The feed unit can be used to introduce the wastewater to be treated, and the discharge unit can be used to discharge the reaction products or unwanted residues.

[0069] The instrument unit can be used to display or monitor the process parameters of the reactor.

[0070]

Instrument Unit

[0071] The instrument unit includes a temperature sensor, a pressure sensor, an on-line TOC analyzer, an on-line pH meter, an on-line copper ion detector, and a liquid level sensor. Preferably, the temperature sensor, the pressure sensor, and the liquid level sensor are interlocked.

[0072] The treatment system further includes a wastewater storage unit 1 located upstream of the multistage centrifugal pump 3. For example, the wastewater storage unit 1 is a wastewater tank.

[0073] The treatment system further includes a steam delivery unit 6 located upstream of the heater 4, and the steam delivery unit 6 is connected to the heater 4.

[0074] The treatment system further includes a flash tank 7 located downstream of the heater 4, and the inlet of the flash tank 7 is connected to the condensate outlet of the heater 4. The condensate of the heater 4 enters the flash tank 7, and the flash tank 7 produces 0.2 MPa steam.

[0075] Example 2

[0076] A method for treating wastewater includes, in the treatment system of Example 1, pressurizing the wastewater (including 20% brine, 4000 - 5000 ppm of organic matter, excess oxygen, copper chloride catalyst, hydrochloric acid, etc.) by a multistage centrifugal pump 2 (with 10-stage impeller and the rotational speed set at 2980 rpm) and then transporting it to a preheater 3 (the heat exchange tubes of the preheater are straight tubes, 19.05 mm × 2.11 mm × 8500 mm) at a flow rate of 24 t / h for preheating to 180°C, then entering a heater 4 to be heated to a temperature of 210°C, and entering a reactor 5 (manufactured by Morimatsu (Jiangsu) Heavy Industry Co., Ltd., with the material being an explosion composite plate of Q235B and TA9, reaction temperature of 260°C, reaction time of 4 h, and pressure of 4.3 MPa) for catalytic wet oxidation reaction to achieve wastewater purification.

[0077] This wastewater treatment system was put into use in November 2021. In June 2022, an internal inspection of the reactor 5 was carried out, and no abnormalities were found, and it was in good use. In May 2023, an internal inspection of the reactor 5 was carried out again, and still no abnormalities were found, and it was in good use. As of May 2025, no weld tearing or other abnormal problems have occurred in the reactor 5 of this treatment system.

[0078] Comparative Example 1

[0079] A method for wastewater treatment, which is different from Example 2 only in that: the multistage centrifugal pump 2 is replaced by a vertical two-stage high-speed pump with a head of 485 m and a flow rate of 27 m 3 , the motor power is 120 kw, and the rated speed is 8076 rpm.

[0080] The rest is the same as Example 2.

[0081] Comparative Example 2

[0082] A method for wastewater treatment, which is different from Example 2 only in that: the shell-and-tube preheater 3 is replaced by a plate-and-shell heat exchanger produced by Valmet of Finland. Among them:

[0083] The design pressure is 6.6 MPa and the temperature is 270 °C.

[0084] Structure type:

[0085] The medium on the plate side is the wastewater pressurized by the multistage centrifugal pump (20% brine, 4000 - 5000 ppm organic matter, excessive oxygen, copper chloride, hydrochloric acid, etc.); the medium on the shell side is the water after the reaction in the oxidation reactor (20% brine, excessive oxygen, copper chloride, hydrochloric acid, etc.).

[0086] The rest is the same as Example 2.

[0087] In this comparative example, the medium on the plate side is wastewater containing organic matter. When high-pressure pure oxygen is introduced, it is easy to cause an explosion risk due to the local accumulation of oxygen and the reaction with organic matter. And because the flow channels of the plate-and-shell heat exchanger are complex and the corrugated structure of the plate forms multiple dead ends, oxygen is easy to accumulate in local areas (such as the edge of the plate or the bottom of the corrugation), forming an explosive mixture gas. At the same time, due to the uneven distribution of the flow velocity on the plate side, the oxygen concentration in the low-flow velocity area can reach 10 - 15% (the lower explosion limit is usually 5 - 8%). The high-temperature decomposition of organic matter causes carbon deposition and blockage on the plate side. Since the plates are fully welded to each other, mechanical cleaning cannot be carried out, thus seriously affecting the heat transfer efficiency. In addition, after blockage, the steam volume needs to be increased. According to the actual operation data, the temperature rise of the heat exchanger after blockage drops from 110 °C at the initial stage of the equipment to 40 °C. Therefore, for the subsequent heater to ensure the wastewater treatment effect, only by increasing the steam of the heater can the wastewater treatment be satisfied. Therefore, 2.4 tons of 3.2 MPa steam need to be consumed additionally per hour (calculated based on the wastewater treatment volume of 24 tons / h).

[0088] Comparative Example 3

[0089] A method for wastewater treatment, which is different from Example 2 only in that: the Q235B and TA9 explosion composite plate (produced by Morimatsu (Jiangsu) Heavy Industry Co., Ltd.) of the reactor 5 is replaced with a loose lining plate (loose lining structure (Q235B + TA9)).

[0090] The rest are the same as Example 2.

[0091] During the operation from April 2017 to April 2021, the problems of the oxidation reactor of the treatment system are shown in the following table:

[0092] Time Problem description of oxidation reactor April 2017 During the first hydrostatic test, the weld at the conical angle of the upper head tore June 2017 During the second hydrostatic test, the weld at the conical angle of the upper head tore November 2018 During the first hot test, there was a dot leak at the T-shaped weld of the upper head December 2018 During the second hot test, there was a strip leak at the butt weld of the upper head September 2019 One week after the formal feeding operation, the longitudinal weld in the middle tore February 2020 A through crack was found at the fillet weld between the support of the fourth tray and the cylinder June 1, 2020 A total of 15 cracks were detected at the weld, including 2 through cracks September 8, 2020 There were 4 defects at the weld, including 2 through cracks November 2020 A total of 12 cracks were detected at the weld, including 8 through cracks April 2021 A total of 9 cracks were detected at the weld, including 3 through cracks

[0093] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wet oxidation wastewater treatment system, characterized in that, It includes a multistage centrifugal pump; A preheater located downstream of the multistage centrifugal pump; A heater located downstream of the preheater; And a reactor located downstream of the heater.

2. The processing system according to claim 1, wherein The multistage centrifugal pump adopts a 10-stage impeller; And / or, the motor of the multistage centrifugal pump is equipped with variable frequency to adjust the speed; And / or, the speed of the multistage centrifugal pump is 1400 - 2980 rpm; And / or, the multistage centrifugal pump includes multistage impellers and a pump body. The pump body includes: a suction section, a discharge section, and a pump shaft. Five impellers are installed inside each of the suction section and the discharge section. The impellers are all installed on the pump shaft, and adjacent two impellers are fixed against loosening by screws; a partition is provided between two adjacent impellers in the suction section and the discharge section; and along the wastewater flow direction, the fifth-stage impeller in the suction section and the first-stage impeller in the discharge section are connected through a balance pipe; And / or, the impeller directions in the suction section and the discharge section are opposite; And / or, the partition is provided with a reflux hole; And / or, the suction section is provided with a fluid inlet; And / or, the discharge section is provided with a fluid outlet; And / or, sealing elements are respectively provided at both ends of the pump shaft.

3. The processing system according to claim 1, characterized in that, The tube-side medium of the preheater is the wastewater pressurized by the multistage centrifugal pump; The shell-side medium of the preheater comes from the water after the wet oxidation reaction in the reactor is completed. For example, it contains 20% brine, excessive oxygen, a catalyst (preferably a copper ion-containing catalyst, exemplarily copper chloride), hydrochloric acid, etc.; And / or, the inlet of the tube-side medium of the preheater is located at the bottom of the tube bundle, and the outlet of the tube-side medium is located at the top of the tube bundle; And / or, the tube side of the preheater is a straight tube or a U-shaped tube.

4. The processing system according to any one of claims 1-3, characterized in that, The reactor adopts a Q235B and TA9 explosion composite plate; And / or, the reactor further includes elements required for the catalytic wet oxidation reaction; the elements include but are not limited to one or more selected from an air inlet unit, an air outlet unit, a feed unit, a discharge unit, and an instrument unit.

5. The processing system according to any one of claims 1-4, characterized in that, The treatment system further includes a wastewater storage unit located upstream of the multistage centrifugal pump.

6. The processing system according to any one of claims 1-5, characterized in that, The treatment system further includes a steam delivery unit located upstream of the heater, and the steam delivery unit is connected to the heater.

7. The processing system according to any one of claims 1-6, characterized in that, The treatment system further includes a flash tank located downstream of the heater, and the inlet of the flash tank is connected to the condensate outlet of the heater.

8. A method for wastewater treatment, characterized in that, Including in the treatment system according to any one of claims 1 - 7, making the wastewater undergo a catalytic wet oxidation reaction to achieve wastewater purification.

9. The method according to claim 8, wherein The wastewater is pressurized by the multistage centrifugal pump and then transported to the preheater; And / or, the speed of the multistage centrifugal pump is 1400 - 2980 rpm.

10. The method according to claim 8 or 9, characterized in that The method includes pressurizing the wastewater in the wastewater storage unit by the multistage centrifugal pump and then transporting it to the preheater for preheating, then entering the heater for heating, and then entering the reactor for catalytic wet oxidation reaction to achieve wastewater purification; And / or, the operating temperature of the reactor is between 150 - 300 °C, and the pressure of the reactor is 4 - 7 MPa; And / or, during the catalytic wet oxidation reaction, the pH value of the wastewater is between 0.8 - 1.4; And / or, the catalyst used in the catalytic wet oxidation reaction is a copper ion-containing catalyst, and the copper ion content is between 1000 - 3000 ppm.

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