Wet catalytic oxidation treatment process for high-concentration organic wastewater

Abstract

The invention belongs to the technical field of environment-friendly treatment of high-concentration organic wastewater, and particularly relates to a wet catalytic oxidation treatment process for high-concentration organic wastewater. Wastewater in the wet catalytic oxidation treatment process for the high-concentration organic wastewater is formed by combining a plurality of streams of wastewater. In order to ensure the safety of the wet oxidation process, the combined wastewater is firstly subjected to steam stripping pretreatment to remove light component organic matters therein, then is pressurized and heated, enters a wet oxidation reaction section to remove most of COD therein, is cooled and depressurized after the reaction is finished, and is fed into the existing multi-effect evaporation section; the multi-effect evaporation concentrated solution is returned to the wet oxidation section to continuously remove organic matters, and condensate water enters a subsequent biochemical treatment section. The wet catalytic oxidation treatment process for the high-concentration organic wastewater is wide in application range, high in treatment efficiency, high in oxidation speed and low in secondary pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection treatment of high-concentration organic wastewater, and in particular relates to a wet catalytic oxidation treatment process for high-concentration organic wastewater. Background Art

[0002] The chemical and pharmaceutical industries produce high-concentration, difficult-to-degrade wastewater during production. Cr ≤100000mg / L, salt content: ≤10%, and other harmful components, complex components, large fluctuations, and poor biodegradability. In view of the characteristics of this wastewater, wet oxidation treatment technology is used, which has a high oxidation efficiency for most organic matter and can withstand fluctuations in a large range. Through the wet oxidation combined process, the COD of the wastewater is degraded by about 70%, and the effluent B / C ratio is increased to above 0.4, which can enter the subsequent treatment section.

[0003] Wet oxidation technology (WAO) refers to the oxidation of organic matter in wastewater into small molecules or CO2, H2O, inorganic salts, etc. under high temperature and high pressure conditions using air, oxygen-enriched or pure oxygen as oxidants. This process does not produce NO x , SO2, HCl, dioxins, furans, fly ash and other harmful substances. The wet oxidation process can utilize the heat generated by the reaction. For wastewater with COD exceeding 15000mg / L, the heat generated by the reaction can maintain the normal progress of the reaction without the need for additional energy input. Therefore, its operating cost can be greatly reduced compared with other treatment technologies. It also has the advantages of wide application range, high treatment efficiency, fast oxidation speed, low secondary pollution and small equipment footprint. Summary of the invention

[0004] In view of the above deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a high-concentration organic wastewater wet catalytic oxidation treatment process to solve the problems of low wastewater COD degradation rate, low effluent B / C ratio and high harmful substance generation rate in the existing wastewater treatment process.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A wet catalytic oxidation treatment process for high-concentration organic wastewater: comprising the following steps:

[0007] S1: pre-treating the combined wastewater with steam to remove light organic matter;

[0008] S2: The treated waste liquid is then pressurized and heated and then enters the wet oxidation reaction component section to remove most of the COD therein, and the temperature and pressure are lowered after the reaction is completed;

[0009] S3: sending the waste liquid treated in step S2 to the existing multiple-effect evaporation section, and returning the concentrated liquid from the multiple-effect evaporation section to the wet oxidation section to continue removing organic matter;

[0010] S4: The wastewater treated in step S3 is then sent to an ammonia nitrogen stripping tower, which uses steam for stripping. The ammonia nitrogen-containing vapor enters an ammonia condenser for condensation, enters an ammonia water tank for temporary storage, and is discharged in time.

[0011] Furthermore, in step S1, before the steam stripping pretreatment, the wastewater needs to be fed through a wastewater feed pump and a filter to remove particulate impurities and then sent to the wastewater stripping tower; at the same time, the wastewater stripping tower uses low-pressure steam to directly contact the wastewater to remove light organic matter in the wastewater.

[0012] Furthermore, the top steam of the wastewater stripping tower is condensed by a light component condenser and then temporarily stored in a light component storage tank, and is intermittently delivered through a light component delivery pump, wherein the non-condensable gas needs to be subjected to external tail gas treatment.

[0013] Furthermore, a catalyst tank is connected to the bottom of the wastewater stripping tower, in which a catalyst is arranged. The catalyst is discharged through a catalyst pump and mixed with the wastewater at the bottom of the wastewater stripping tower, and then the pressure is increased to 6-8MPaG by a wastewater booster pump and then sent to the wet oxidation reaction assembly.

[0014] Furthermore, the wet oxidation reaction component includes a wastewater storage tank, a wastewater pump, an air compressor, a heat exchanger, a reactor and a gas-liquid separator; wherein the wastewater storage tank is connected to the light component storage tank through the light component delivery pump, the wastewater is connected to the input end of the heat exchanger after passing through the heat exchanger, and is recycled to the heat exchanger after reaction in the reactor, and finally the treated wastewater is delivered to the gas-liquid separator for gas-liquid separation; the middle section of the wet oxidation reaction component in the wet oxidation reaction component is heated with heat transfer oil as a heat source, which is only put into use during startup, and the reaction heat is used to maintain system operation after the device runs smoothly.

[0015] Furthermore, the high-pressure wastewater output by the wastewater pump and the high-pressure air output by the air compressor undergo an oxidation reaction in a reactor, the reaction time is ≥2h, and the gas is separated after the reaction. The separated gas needs to be decompressed by a regulating valve and then enter the tail gas washing tower. After being purified and cooled by process water spraying, it is discharged into the off-site tail gas system.

[0016] Furthermore, in step S4, the salt-containing waste liquid is discharged from the bottom of the ammonia nitrogen stripping tower, and a part of it is returned to the wastewater stripping tower for circulation treatment after passing through the evaporation water pump, and the other part is sent to the multi-effect evaporation system for desalination after being filtered through the evaporation filter, and a part of the circulating condensate of the multi-effect evaporation system also needs to be returned to the wastewater stripping tower.

[0017] In summary, due to the adoption of the above technical solution, the beneficial technical effects of the invention are:

[0018] After oxidation treatment using a high-concentration organic wastewater wet catalytic oxidation treatment process, most organic matter has a high oxidation efficiency and can withstand a wide range of fluctuations. Through the wet oxidation combined process, the wastewater COD is degraded by about 70%, and the effluent B / C ratio is increased to above 0.4, which can enter the subsequent treatment section.

[0019] In addition, the wet oxidation process can utilize the heat generated by the reaction. For wastewater with COD exceeding 15000mg / L, the heat generated by the reaction can maintain the normal progress of the reaction without the need for additional energy input, so its operating cost can be greatly reduced compared with other treatment technologies. It also has a wide range of applications, high treatment efficiency, fast oxidation speed, low secondary pollution, and a small footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the present invention.

[0021] Figure 2 It is a schematic diagram of the connection relationship of the wet oxidation reaction components in the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in combination with the embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and are not used to limit the invention.

[0023] Example 1

[0024] In this embodiment, Figure 1-2 As shown, a high-concentration organic wastewater wet catalytic oxidation treatment process comprises the following steps:

[0025] S1: pre-treating the combined wastewater with steam to remove light organic matter;

[0026] S2: The treated waste liquid is then pressurized and heated and then enters the wet oxidation reaction component section to remove most of the COD therein, and the temperature and pressure are lowered after the reaction is completed;

[0027] S3: sending the waste liquid treated in step S2 to the existing multiple-effect evaporation section, and returning the concentrated liquid from the multiple-effect evaporation section to the wet oxidation section to continue removing organic matter;

[0028] S4: The wastewater treated in step S3 is then sent to an ammonia nitrogen stripping tower, which uses steam for stripping. The ammonia nitrogen-containing vapor enters an ammonia condenser for condensation, enters an ammonia water tank for temporary storage, and is discharged in time.

[0029] In step S1, before the steam stripping pretreatment, the wastewater needs to be fed through a wastewater feed pump and a filter to remove particulate impurities and then sent to the wastewater stripping tower; at the same time, the wastewater stripping tower uses low-pressure steam to directly contact the wastewater to remove light organic matter in the wastewater.

[0030] In step S4, the salt-containing waste liquid is discharged from the bottom of the ammonia nitrogen stripping tower, and a part of it is returned to the wastewater stripping tower for circulation treatment after passing through the evaporation water inlet pump, and the other part is sent to the multi-effect evaporation system for desalination after being filtered through the evaporation filter, and a part of the circulating condensate of the multi-effect evaporation system also needs to be returned to the wastewater stripping tower.

[0031] The top steam of the wastewater stripping tower is condensed by the light component condenser and then temporarily stored in the light component storage tank, and is intermittently delivered by the light component delivery pump, wherein the non-condensable gas needs to be treated with external tail gas. The bottom of the wastewater stripping tower is connected to a catalyst tank, in which a catalyst is arranged, and the catalyst is discharged through a catalyst pump and mixed with the wastewater at the bottom of the wastewater stripping tower, and then the pressure is increased to 6-8MPaG by a wastewater booster pump and then delivered to the wet oxidation reaction assembly.

[0032] like Figure 2 As shown, the wet oxidation reaction assembly includes a wastewater storage tank, a wastewater pump, an air compressor, a heat exchanger, a reactor and a gas-liquid separator; wherein the wastewater storage tank is connected to the light component storage tank through the light component delivery pump, the wastewater is connected to the input end of the heat exchanger after passing through the heat exchanger, and is recycled to the heat exchanger after reaction in the reactor, and finally the treated wastewater is delivered to the gas-liquid separator for gas-liquid separation; the middle section of the wet oxidation reaction assembly in the wet oxidation reaction assembly is heated by heat transfer oil as a heat source, which is only put into use when starting up, and the system is maintained to run with the reaction heat after the device runs smoothly. The high-pressure wastewater output by the wastewater pump and the high-pressure air output by the air compressor undergo oxidation reaction in the reactor, and the reaction time is ≥2h, and the gas is separated after the reaction. The separated gas needs to be decompressed by a regulating valve and then enters the tail gas water washing tower, and is purified and cooled by process water spraying before being discharged into the off-boundary tail gas system.

[0033] Operation preparation and precautions

[0034] 1. Driving preparation:

[0035] Confirm that the equipment is installed;

[0036] Confirm that water, electricity, and instrument air meet usage requirements.

[0037] Confirm that all instruments are in good condition.

[0038] Confirm that the workshop production line is operating normally.

[0039] The exhaust system valve in the device is open.

[0040] The catalyst system, thermal oil system and alkali solution system are ready.

[0041] 2. Driving and normal operation

[0042] Open the corresponding wastewater feed pump according to actual needs, and send the wastewater into the wastewater stripping tower after removing particulate matter through the water inlet filter until a certain liquid level is formed in the tower bottom (about 1 / 3 of the liquid level gauge).

[0043] Start the wastewater booster pump, open the circulation pipeline valve, establish self-circulation of the wastewater stripping tower, and control the circulation flow to be stable.

[0044] Open the circulating water inlet and outlet of the light component condenser and put the condensation system into use.

[0045] Open the steam valve of the wastewater stripping tower and start to introduce steam.

[0046] Adjust the water inlet and steam inlet so that the light components in the wastewater can be taken out by steam. The water inlet increases gradually from small to large and finally stabilizes at 0.8m 3 / h or so; the steam inlet volume needs to be determined by sampling and analyzing the wastewater entering the tower and the wastewater discharged from the bottom of the tower, and the amount of steam inlet volume is determined based on the light component removal rate.

[0047] The stripped light component is discharged timely through the light component transfer pump according to the liquid level of the light component storage tank.

[0048] After the tail gas washing tower is added with process water to establish a liquid level of about 50%, turn on the tail washing circulation pump for self-circulation.

[0049] Start the air compressor and booster to send high-pressure air into the reactor.

[0050] Put the catalyst system and heat transfer oil system into use; open the valve from the wastewater booster pump to the reactor to send the wastewater to the reactor. When the reaction is stable and the temperature of the reaction system is >220℃, switch the wastewater to enter the reactor through the bypass and cut off the heat transfer oil system.

[0051] The pressure of the reaction system is automatically controlled at 6-8 MPaG by the regulating valve on the exhaust pipe at the top of the reactor; the liquid level in the reactor is automatically controlled at about 1 / 3 by the regulating valve on the discharge pipe at the upper part of the reactor.

[0052] Open the circulating water inlet and outlet of the ammonia condenser and put the condensation system into use.

[0053] When the liquid level in the ammonia nitrogen stripping tower reaches about 1 / 3 of the liquid level gauge, start the evaporation feed pump, open the circulation pipeline valve, and establish the self-circulation of the ammonia nitrogen stripping tower. At the same time, put the alkali solution system into use to control the pH of the wastewater entering the tower to 9-10.

[0054] After the ammonia nitrogen stripping tower circulation is stable, open the steam valve and start to let steam in. By sampling and analyzing the wastewater entering the tower and the wastewater discharged from the bottom of the tower, the amount of steam inlet is determined based on the ammonia nitrogen removal rate.

[0055] Drain ammonia in a timely manner according to the liquid level in the ammonia tank.

[0056] When the liquid level in the kettle of the ammonia nitrogen stripping tower rises to 60%, open the valve of the evaporation water inlet pump to the multiple-effect evaporation system, remove particulate impurities through the evaporation filter, and then send the water into the multiple-effect evaporation system. Intermittently return the wastewater from the ammonia nitrogen stripping tower and the condensate produced by the multiple-effect evaporation to the wastewater stripping tower.

[0057] When the liquid level in the tail gas water washing tower rises to 80%, open the external discharge valve to discharge the water to the biochemical system for further treatment.

[0058] 3. Parking

[0059] After confirming the shutdown for 10 minutes, stop the device. The specific steps are as follows:

[0060] Stop the wastewater feed pump;

[0061] Cut off steam from the wastewater stripper;

[0062] When the liquid level in the wastewater stripping tower drops to 0, stop the catalyst system and the wastewater booster pump.

[0063] When the pressure and temperature of the reactor decrease and the liquid level of the separator continues to decrease, cut off the air intake and stop the booster and air compressor;

[0064] When the liquid level at the top of the reactor drops to close to 0, the alkali solution system is stopped and the steam in the ammonia nitrogen stripping tower is cut off.

[0065] All the wastewater in the ammonia nitrogen stripping tower is sent to the multi-effect evaporation system through the evaporation water inlet pump. When the liquid level in the ammonia nitrogen stripping tower drops to close to 0, the evaporation water inlet pump is stopped.

[0066] Close the circulation loop of the tail suction circulation pump and send all the liquid phase in the tail gas water washing tower to the biochemical system; stop the pump when the tower liquid level is 0.

[0067] Shut off the circulating water of all condensers; drain the remaining liquid in the equipment through the drain pipe.

[0068] Flush and dry the system, clean or replace the filter screen as needed, and prepare for the next drive.

[0069] 4. Notes

[0070] Some of the above operations can be performed simultaneously to improve efficiency. The specific operation is subject to actual needs.

[0071] During initial start-up, the composition of wastewater from each stripping tower can be checked regularly, and the ratio of water intake to steam intake can be adjusted accordingly; after the operating conditions stabilize, the frequency of inspection can be appropriately reduced.

[0072] During operation, the valve on the reactor sewage pipeline is opened regularly to discharge sewage to prevent blockage at the bottom of the reactor.

[0073] Check the pipeline filter and drainage pipeline regularly to prevent blockage by debris.

[0074] Pay attention to the liquid level in the stripping tower, water washing tower and separator. If the liquid level is too high, it should be discharged in time or the water intake should be reduced.

[0075] If leakage occurs, timely maintenance shall be carried out.

[0076] Pay attention to observe whether there is pressure buildup and cross-pressure during the absorption process to ensure that the system is in a smooth and stable state.

[0077] The above description is a preferred embodiment of the invention and is not intended to limit the invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the invention should be included in the protection scope of the invention.

Claims

1. A wet catalytic oxidation treatment process for high-concentration organic wastewater: characterized by: The following steps are involved: S1: pre-treating the combined wastewater with steam to remove light organic matter; S2: The treated waste liquid is then pressurized and heated and then enters the wet oxidation reaction component section to remove most of the COD therein, and the temperature and pressure are lowered after the reaction is completed; S3: sending the waste liquid treated in step S2 to the existing multiple-effect evaporation section, and returning the concentrated liquid from the multiple-effect evaporation section to the wet oxidation section to continue removing organic matter; S4: The wastewater treated in step S3 is then sent to an ammonia nitrogen stripping tower, which uses steam for stripping. The ammonia nitrogen-containing vapor enters an ammonia condenser for condensation, enters an ammonia water tank for temporary storage, and is discharged in time.

2. A high-concentration organic wastewater wet catalytic oxidation treatment process according to claim 1, characterized in that: In step S1, before the steam stripping pretreatment, the wastewater needs to be fed through a wastewater feed pump and a filter to remove particulate impurities and then sent to the wastewater stripping tower; at the same time, the wastewater stripping tower uses low-pressure steam to directly contact the wastewater to remove light organic matter in the wastewater.

3. A high-concentration organic wastewater wet catalytic oxidation treatment process according to claim 1, characterized in that: The top steam of the wastewater stripping tower is condensed by the light component condenser and then temporarily stored in the light component storage tank, and is intermittently delivered through the light component delivery pump, wherein the non-condensable gas needs to be subjected to external tail gas treatment.

4. A wet catalytic oxidation treatment process for high-concentration organic wastewater according to claim 1, characterized in that: The bottom of the wastewater stripping tower is connected to a catalyst tank, in which a catalyst is arranged. The catalyst is discharged through a catalyst pump and mixed with the wastewater at the bottom of the wastewater stripping tower, and then the pressure is increased to 6-8 MPaG by a wastewater booster pump and then sent to the wet oxidation reaction component.

5. A wet catalytic oxidation treatment process for high-concentration organic wastewater according to claim 1, characterized in that: The wet oxidation reaction component includes a wastewater storage tank, a wastewater pump, an air compressor, a heat exchanger, a reactor and a gas-liquid separator; wherein the wastewater storage tank is connected to the light component storage tank through the light component delivery pump, the wastewater is connected to the input end of the heat exchanger after passing through the heat exchanger, and is recycled to the heat exchanger after reaction in the reactor, and finally the treated wastewater is delivered to the gas-liquid separator for gas-liquid separation; the middle section of the wet oxidation reaction component in the wet oxidation reaction component is heated with heat transfer oil as a heat source, and is only put into use when starting up, and the reaction heat is used to maintain the system operation after the device runs smoothly.

6. A wet catalytic oxidation treatment process for high-concentration organic wastewater according to claim 5, characterized in that: The high-pressure wastewater output by the wastewater pump and the high-pressure air output by the air compressor undergo an oxidation reaction in the reactor, the reaction time is ≥2h, and the gas is separated after the reaction. The separated gas needs to be decompressed by a regulating valve and then enter the tail gas washing tower. After being purified and cooled by process water spraying, it is discharged into the off-site tail gas system.

7. A wet catalytic oxidation treatment process for high-concentration organic wastewater according to claim 1, characterized in that: In step S4, the salt-containing waste liquid is discharged from the bottom of the ammonia nitrogen stripping tower, and a part of it is returned to the wastewater stripping tower for circulation treatment after passing through the evaporation water inlet pump, and the other part is sent to the multi-effect evaporation system for desalination after being filtered through the evaporation filter, and a part of the circulating condensate of the multi-effect evaporation system also needs to be returned to the wastewater stripping tower.

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