CN116789316A - Novel wet oxidation wastewater treatment system - Google Patents

Abstract

The invention discloses a new type of wet oxidation wastewater treatment system. The system includes a waste alkali tank, a booster pump, and an adjustable NaOH solution adder. The outlet of the gas-liquid separator is provided with a device for real-time monitoring of the pH of the effluent. pH online analyzer of value; the outlet pipe of the boost pump is connected to the preheater, the back end of the preheater is connected to the air mixer and reactor in turn, the air mixer is connected to an external air compressor, and the preheater is also connected to the cooler , the cooler is connected to the gas-liquid separator, and there are two pipelines connected to the back of the gas-liquid separator; the liquid part is sent to the neutralization device, and by adjusting the pH value of the solution, the pH value discharged into the sewage pool is controlled to be after 6-9 emission. Using this solution can solve the preheater clogging problem, meet the hydroxide concentration in the reaction, and control the pH in real time to reduce safety issues caused by reverse reactions. It can reduce energy consumption, reduce reaction pressure, lower reaction temperature, and reduce equipment investment.

Description

A new type of wet oxidation wastewater treatment system

Technical field

The invention belongs to the field of organic wastewater treatment, and specifically relates to a new type of wet oxidation wastewater treatment system.

Background technique

Industrial organic wastewater mainly comes from medicine, chemical industry, textile, printing and dyeing, etc. This type of wastewater usually has high salt concentration and organic matter concentration, making it difficult to directly use biochemical processes to treat it. This kind of wastewater is usually pretreated using physical and chemical methods to reduce its COD concentration and improve its biochemical properties before biochemical treatment.

Most wastewater treatments typically use catalytic wet oxidation to pretreat wastewater. Wet oxidation is a method for treating medium to high concentration organic wastewater. Its characteristic is to keep the waste alkali liquid in a liquid state under high temperature (125~320℃) and high pressure (0.5~20MPa) conditions, and use oxygen in the air to oxidize the inorganic sulfides and various organic sulfides in it. It generates sulfate and at the same time oxidizes and decomposes other organic substances such as phenols, hydrocarbons and other pollutants into carbon dioxide and water. It is a green, energy-saving and environmentally friendly organic wastewater treatment method.

The main reaction principles are as follows:

1. Na2S oxidation

2S ^2- +2O ₂ +H ₂ O→S ₂ O ₃ ^2- +2OH ^-

S ₂ O ₃ ^2- +2O ₂ +2OH ^- →2SO ₄ ^2- +H ₂ O

2. NaHS oxidation:

HS ^- +2O ₂ →HSO ₄ ^-

HSO ^4- +OH ^- →SO ₄ ^2- +H ₂ O

3. Oxidation of organic matter, such as oxidation of hydrocarbons:

C _x H _y +(x+y/4)O ₂ →xCO ₂ +(x+y/2)H ₂ O

In actual use, we found that the following situation exists: first, the reaction product flow is discharged through the outlet at the top of the reactor, enters the preheater, and exchanges heat with the gas-liquid mixture before the reaction, and due to the air injection, the preheating In the front section of the reactor, this process causes the waste alkali stock solution to react in the preheater in advance, causing the preheater to be clogged. However, in the disclosed prior art, the compressed air is still installed at the front end of the reactor and placed in the exchanger. The front end of the heat exchanger, and the back end of the heat exchanger is connected to the reactor, as disclosed in the patent number; CN114057276A "A method and system for wet oxidation". The patent applied for in 2020 still cannot avoid this problem. Therefore, the present invention proposes a new solution based on this technical problem;

Secondly, since the oxidation reaction of Na ₂ S and NaHS requires the consumption of hydroxyl radicals, the alkali content in the waste alkali solution is not enough to meet the hydroxide radical concentration. Therefore, the effluent before the booster pump operation shows acidity, and the COD and sulfide in the effluent The content of these substances is all unqualified. Therefore, we propose a new solution based on this technical problem;

Third, after the reaction in the liquid separation tank, the method of directly discharging the liquid into the sewage tank does not control the acid-base neutralization degree of the solution, and the discharged sewage will have certain effects without treatment. Therefore, this method is proposed based on this technical problem. New solutions.

Contents of the invention

In order to solve the technical problems mentioned in the background art, the purpose of the present invention is to provide a new wet oxidation wastewater treatment system and a preparation method thereof.

In order to solve the above technical problems, the object of the present invention can be achieved through the following technical solutions:

The invention of this application provides a new type of wet oxidation wastewater treatment system, including a waste alkali tank. The organic waste liquid in the waste alkali tank is collected from different pipelines in the factory, and the organic waste liquid flows centrally to the waste alkali liquid. In the tank, the end of the outlet pipe of the waste alkali tank is connected to the booster pump. The waste alkali liquid and desalted water are mixed in the pipeline mixer. At the same time, an adjustable NaOH is provided in the pipeline section connecting the waste alkali tank and the booster pump. A solution adder is provided at the outlet of the gas-liquid separator with a pH online analyzer for real-time monitoring of the pH value of the effluent to control the output solution to be alkaline;

The outlet pipe of the boost pump is connected to a preheater, and the rear end of the preheater is connected to an air mixer and a reactor in sequence. The air mixer is connected to an external air compressor, and the reactor converts the reacted gas It flows back to the preheater through the pipeline. The valve controls whether the gas-liquid mixture in the preheater enters the reactor section again for reaction or is discharged to the cooler, where it exchanges heat with the cooling water in the cooler to lower the temperature of the gas-liquid mixture. ;

There are two pipelines connected to the back of the gas-liquid separator. The gas part is introduced into the exhaust tank, and is discharged into the atmosphere after passing the test. The liquid part is sent to the neutralization device, and the pH value of the solution is adjusted to control the discharge into the sewage pool. The pH value of the solution is between 6-9.

Preferably, a filter is provided between the waste alkali liquid tank and the booster pump, and the waste alkali liquid is pressurized to 6.0 MPa by the booster pump and then sent to the preheater.

Preferably, the waste alkali liquid and air undergo an oxidation reaction in the reactor. The pressure at the top of the reactor is controlled to be 2.7-3.0Mpa and the temperature is 190°C-240°C. The reacted material is discharged through the outlet at the top of the reactor. The return pipe enters the preheater, mixes with the material before reaction and exchanges heat, and the temperature drops to 190°C.

Preferably, the temperature of the material discharged from the preheater to the cooler is lowered to 55°C after exchanging heat with cooling water, and is discharged into the gas-liquid separator. The gas phase passes through the top outlet of the gas-liquid separator, and passes through the pressure control valve and orifice plate. After decompression, discharge to the atmosphere, and then discharge to the atmosphere through the vent pipe on the top of the vent tank. The liquid phase is discharged through the liquid level control valve at the bottom outlet of the gas-liquid separator.

Preferably, during the startup phase, the set pressure of the exhaust line pressure control valve at the top of the gas-liquid separator is 2.0 MPa, which is lower than the steam pressure value at the bottom of the reactor by 0.1 MPa. The liquid level control value of the liquid phase outlet liquid level control valve is 50%; during the heating stage, the liquid level of the gas-liquid separator reaches 50%, and after the liquid level control is stable, open the steam inlet valve at the bottom of the reactor, and remotely gradually Open the steam flow regulating valve and control the temperature rising rate indicated by the temperature indicator at the top of the reactor to be lower than 50°C/h; during the boost reaction stage, the pressure settings of the gas-liquid separator and the pressure control valve on the exhaust pipeline The fixed range is 2.7-3.0MPaG.

Preferably, during the startup phase, the compressed air flow regulating valve in the air compressor increases the pressure of the air mixer and the system in the reactor, the pressure increase rate is controlled at 0.2MPa/min, and the pressure is stabilized at 2.0MPa.

Preferably, in the boosting reaction stage, 10% NaOH solution is added to the connection section between the spent alkali tank and the boosting pump by controlling the NaOH solution adder, controlling the compressed air flow rate of the air compressor to 500Nm ³ /h, and controlling the reactor The bottom temperature is 195°C.

Preferably, during the pressurization reaction stage, the pH value of the solution discharged from the gas-liquid separation tank is controlled to be greater than 11.

Preferably, the neutralization device includes a neutralization tank, an acid injection pump and an alkali injection pump for regulating the solution in the neutralization tank. The acid injection pump is connected to a 50% sulfuric acid tank and controls the pH of the solution in the neutralization tank. value; the alkali injection pump is connected to the 10% alkali tank and controls the pH value of the solution in the neutralization tank. The neutralization device is also provided with a circulation pump for circulating the solution.

Preferably, the neutralization tank is provided with a liquid level contact point. When the liquid level in the neutralization tank is at the low liquid level contact point, the circulation pump stops; when the liquid level in the neutralization tank is at the intermediate liquid level contact point, the circulation pump starts; When the pH value of the neutralization tank is greater than or equal to 9.0, the acid injection pump starts, and when the pH value is less than or equal to 8.5, the acid injection pump stops; when the pH value of the neutralization tank is less than or equal to 6.5, the alkali pump starts, and when the pH value is 7.0, the alkali pump stops.

Beneficial effects of the present invention:

1. In the present invention, the existing air compressor presses the air before the preheater is changed to the step of injecting the air into the preheater, and an air mixer is added, and the air mixer is used to centrally discharge the gas into the reactor. Reaction, avoid direct reaction in the preheater, which may cause blockage of the preheater;

2. The present invention overcomes the problem that the alkali content in the waste alkali liquid is not enough to meet the hydroxide concentration, which is not conducive to the operation of the subsequent oxidation reaction. For this reason, it is designed to install a PH online analyzer at the outlet of the gas-liquid separator to ensure the wet oxidation reaction. The process is carried out in an environment with excessive hydroxyl radicals. Try to control the amount of alkali injected to ensure the safety of the oxidation reaction, prevent the reverse reaction from generating hydrogen sulfide, reduce the occurrence of safety hazards, and ensure that the COD of the wet oxidation effluent is less than 500 mg/L, and the sulfide Less than 1mg/L, pH greater than 11.

3. The present invention adds a neutralization system to ensure that the pH value of the water discharged into the sewage pool is between 6 and 9, thereby reducing the impact of the discharged sewage on the environment.

4. The solution of the present invention can operate at a reaction pressure of 2.7-3.0MPa and an inlet temperature of 190-240°C, which can reduce energy consumption, reaction pressure, reaction temperature, and equipment investment.

Description of the drawings

Figure 1 is a schematic diagram of the system of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example 1

The organic waste liquid in the waste alkali tank is collected from different pipelines in the factory. The waste alkali liquid flows from the waste alkali tank into the treatment system. The waste alkali liquid and desalted water are mixed in the pipeline mixer, and the COD is reduced to about 77692mg/ L, an adjustable NaOH solution adder is provided at the connection section between the waste alkali tank and the booster pump to regulate the pH value entering the reactor to be alkaline, thereby facilitating the back-end oxidation reaction. After being diluted in the pipeline The waste alkali liquid is filtered through the filter, pressurized to 6.0MPa by a booster pump, and the material is sent to the preheater. After the material passes through the preheater, it is transported to the air mixer at the rear end. The compressed air from the air compressor is introduced into the air mixer at the same time. Then the gas and liquid react in the reactor, and then the material in the reactor flows back to the preheater. , exchange heat with the reacted stream in the preheater, and be heated to 176°C. In this plan, by adjusting the order of air entry, the waste alkali liquid reacts in the preheater in advance, causing problems such as blockage of the preheater, and extends the service life of the preheater. The waste alkali liquid and air in the reactor are An oxidation reaction occurs. The specific principle of the oxidation reaction is: 2S ^2- +2O ₂ +H ₂ O→S ₂ O ₃ ^2- +2OH ^- , S ₂ O ₃ ^2- +2O ₂ +2OH ^- →2SO ₄ ^2- +H ₂ O, HS-+2O ₂ →HSO ₄ ^- , HSO ₄ ^- +OH ^- →SO ₄ ^2- +H ₂ O, C _x H _y +(x+y/4)O ₂ →xCO ₂ +(x+ y/2)H ₂ O.

The pressure and temperature at the top of the reactor are controlled at 2.7-3.0MPaG and 190℃-240℃. The reacted stream is discharged through the outlet at the top of the reactor, enters the preheater, and exchanges heat with the gas-liquid mixture before the reaction, and the temperature drops to about 190°C. Then it exchanges heat with cooling water in the cooler, and the temperature drops to 55°C. During the startup phase, 1. Open the cooling water inlet valve of the cooler, open the exhaust valve at the top of the cooler until cooling water overflows from the exhaust valve, close the exhaust valve, and open the cooling water outlet valve (opening 50%) ; 2. Set the set pressure of the exhaust pipeline pressure control valve at the top of the gas-liquid separator to 2.0Mpa. Before doing this, check the local pressure value of the steam at the bottom of the reactor to ensure that the set value is lower than the steam The pressure is 0.1MPa, and the liquid level control value of the liquid phase outlet liquid level control valve of the gas-liquid separator is set to 50%: 3. Start the air compressor (hereinafter also referred to as air compressor), and slowly open the compressed air flow regulating valve for the system Boost the pressure. The pressure increase speed is controlled at 0.2MPa/min and the pressure is stable at 2.0MPa. When the flow reaches 450Nm3/h, switch to automatic control; 4. Start the booster pump on site and adjust the pump outlet flow to ^0.5m3 /h. .

During the heating stage: 1. After the liquid level of the gas-liquid separator reaches 50% and the liquid level control is stable, open the steam inlet valve at the bottom of the reactor, remotely and gradually open the steam flow regulating valve, and control the temperature indicator at the top of the reactor. The temperature rise rate is lower than 50℃/h, and pay attention to the vibration of pipelines and equipment and the cooling water outlet temperature of the cooler; 2. When the indicated value of the thermometer on the top of the reactor reaches 200℃, keep the steam inlet valve of the reactor open .

During the pressure boosting reaction stage: after the liquid phase is discharged through the liquid level control valve at the bottom outlet of the gas-liquid separator, 1. The pressure setting value of the pressure control valve on the exhaust pipeline at the top of the gas-liquid separator is changed to 2.8Mpa (value Adjust according to actual conditions to ensure that the reactor outlet pressure reaches the operating pressure of the wet oxidation device (2.7-3.0MPaG); 2. Open the inlet valve of the waste alkali liquid to allow the waste alkali liquid to enter the system, and cut the desalted water into 10% NaOH liquid (also Other alkali solutions can be selected under the same circumstances); 3. Increase the compressed air flow to 500Nm ³ /h; 4. Control the temperature at the bottom of the reactor to 195°C by adjusting the steam volume; 5. Adjust the 10% alkali solution pump injection amount, Ensure that the pH value of the effluent is always greater than 11; 6. Sampling the solution after the reaction in the reactor. When the COD value of the sample taken at the solution sampling point is lower than 500mg/L and the sulfide value is lower than 1mg/L, switch the valve and enter the cooler. Then it goes through the gas-liquid separator to the neutralization device for neutralization treatment. The processing process is: 1. Open the outlet valve of the metering pump (acid injection pump, alkali injection pump); 2. Open the inlet valve of the metering pump (acid injection pump, alkali injection pump), and the outlet valves of the sulfuric acid tank, alkali tank, and neutralization tank. ; 3. Adjust the stroke of the metering pump (acid injection pump, alkali injection pump) to the appropriate position (about 20%); 4. Select the operating mode (manual, automatic, remote control), and operate manually on the spot; 5. Open the circulation pump inlet Hand valve, open the outlet hand valve 1/4, start the circulation pump; 6. Remote control operation: The operation panel selector switch is manually switched to automatic mode, the device operates automatically, and the acid pump or alkali pump is automatically started according to the pH setting value. At this time, you need to pay attention to the following states: (1) Start and stop of the circulation pump: when the liquid level of the neutralization tank is at the low level contact, the circulation pump stops; when the liquid level of the neutralization tank is at the middle liquid level contact, the circulation pump starts ; (2) Start and stop of acid and alkali pumps: ① When the liquid level of the acid and alkali tanks reaches the low level contact point, the low liquid level chain does not allow the acid and alkali injection pumps to be started; ② The acid injection pump starts when the pH value is greater than or equal to 9.0 , the acid injection pump stops when the pH value is less than or equal to 8.5; ③ The alkali injection pump starts when the pH value is less than or equal to 6.5, and the alkali injection pump stops when the pH value is 7.0. When the circulation pump is stopped, the acid and alkali pumps do not operate. When pH>9 or pH<7, the solution re-enters the circulation neutralization state; when 7<pH<9, the solution can be discharged into the sewage pool.

The gas phase separated by the gas-liquid separator passes through the top outlet of the gas-liquid separator, is decompressed by the pressure control valve and the orifice plate, and then discharged to the atmosphere, and then discharged to the atmosphere through the vent pipe on the top of the vent tank.

Finally, it should also be noted that the above examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many modifications are possible. All modifications that a person of ordinary skill in the art can directly derive or associate from the disclosure of the present invention should be considered to be within the protection scope of the present invention.

Claims (10)

1. The novel wet oxidation wastewater treatment system is characterized by comprising a waste alkali liquid tank, wherein organic waste liquid in the waste alkali liquid tank is collected from different pipelines in a factory, the organic waste liquid is concentrated and flows into the waste alkali liquid tank, the tail end of a liquid outlet pipe of the waste alkali liquid tank is connected with a booster pump, waste alkali liquid and desalted water are mixed in a pipeline mixer, an adjustable NaOH solution adder is arranged at the connecting pipeline section of the waste alkali liquid tank and the booster pump, a pH online analyzer for monitoring the pH value of effluent in real time is arranged at the outlet of a gas-liquid separator, and the output solution is controlled to be alkaline;

the outlet pipeline of the booster pump is connected with the preheater, the rear end of the preheater is sequentially connected with the air mixer and the reactor, the air mixer is externally connected with the air compressor, the reactor returns the reacted gas to the preheater through the pipeline, and whether the gas-liquid mixture in the preheater enters the reactor section again for reaction or is discharged to the cooler is controlled through the valve, and the gas-liquid mixture exchanges heat with cooling water in the cooler to reduce the temperature of the gas-liquid mixture;

the gas-liquid separator is connected with two pipelines backwards, and a gas part is introduced into the exhaust tank and is discharged into the atmosphere after being detected to be qualified; the liquid part is sent into a neutralization device, and the pH value of the solution discharged into a sewage pool is controlled to be between 6 and 9 by regulating and controlling the pH value of the solution.

2. The novel wet oxidation wastewater treatment system according to claim 1, wherein a filter is further arranged between the spent caustic solution tank and the booster pump, and the spent caustic solution is pressurized to 6.0MPa by the booster pump and then conveyed to the preheater.

3. The novel wet oxidation wastewater treatment system as set forth in claim 1, wherein the waste lye and air undergo oxidation reaction in a reactor, the top control pressure of the reactor is 2.7-3.0Mpa, the temperature is 190-240 ℃, the reacted materials are discharged from the outlet at the top of the reactor, enter the preheater through a return pipeline, and are mixed and heat exchanged with the materials before the reaction, and the temperature is reduced to 190 ℃.

4. The novel wet oxidation wastewater treatment system according to claim 1, wherein the temperature of the material discharged from the preheater to the cooler is reduced to 55 ℃ after heat exchange with cooling water, the material is discharged into the gas-liquid separator, and the gas phase is discharged to the atmosphere after being decompressed through the pressure control valve and the pore plate through the top outlet of the gas-liquid separator and then discharged to the atmosphere through the top blow-down pipe of the blow-down tank. The liquid phase passes through a liquid level control valve discharge device at the bottom outlet of the gas-liquid separator.

5. A novel wet oxidation wastewater treatment system according to claim 1, wherein during the start-up phase, the set pressure of the gas-liquid separator top exhaust line pressure control valve is 2.0Mpa, which is lower than the steam pressure value at the bottom of the reactor by 0.1Mpa, and the liquid level control value of the gas-liquid separator liquid phase outlet liquid level control valve is 50%; in the temperature rising stage, after the liquid level of the gas-liquid separator reaches 50%, and the liquid level is controlled to be stable, a steam inlet valve at the bottom of the reactor is opened, a steam flow regulating valve is opened remotely and gradually, and the temperature rising speed indicated by a temperature indicating instrument at the top of the reactor is controlled to be lower than 50 ℃/h; in the step-up reaction stage, the pressure setting range of the pressure control valve on the exhaust pipeline of the gas-liquid separator is 2.7-3.0MPaG.

6. The novel wet oxidation wastewater treatment system according to claim 5, wherein in the starting stage, the compressed air flow regulating valve in the air compressor is used for boosting the pressure of the air mixer and the system in the reactor, the pressure boosting speed is controlled at 0.2MPa/min, and the pressure is stabilized at 2.0MPa.

7. The novel wet oxidation wastewater treatment system according to claim 6, wherein in the step-up reaction stage, 10% NaOH solution is added into the connection section of the spent caustic solution tank and the step-up pump by controlling the NaOH solution adder, and the compressed air flow of the air compressor is controlled to 500Nm ³ And/h, controlling the bottom temperature of the reactor to be 195 ℃.

8. A novel wet oxidation wastewater treatment system according to claim 7 and wherein during said step-up reaction stage, the pH of the solution exiting said gas-liquid separation tank is controlled to be greater than 11.

9. The novel wet oxidation wastewater treatment system according to claim 8, wherein the neutralization device comprises a neutralization tank, an acid injection pump and an alkali injection pump for regulating and controlling the solution in the neutralization tank, wherein the acid injection pump is connected with a 50% sulfuric acid tank and controls the pH value of the solution in the neutralization tank; the alkali injection pump is connected with a 10% alkali liquor tank and controls the pH value of the solution in the neutralization tank, and a circulating pump for circulating the solution is further arranged in the neutralization device.

10. The novel wet oxidation wastewater treatment system according to claim 9, wherein the neutralization tank is provided with a liquid level contact, and the circulating pump is stopped when the liquid level of the neutralization tank is at a low liquid level contact; when the liquid level of the neutralization tank is at the intermediate liquid level contact point, the circulating pump is started; when the pH value of the neutralization tank is more than or equal to 9.0, starting an acid injection pump, and stopping the acid injection pump with the pH value less than or equal to 8.5; when the pH value of the neutralization tank is less than or equal to 6.5, the alkali pump is started, and the pH value of 7.0 is stopped.