CN116692981A - A kind of resource treatment process and treatment system of nitrobenzene wastewater - Google Patents

Abstract

The invention discloses a recycling treatment process and a treatment system of nitrobenzene wastewater. The nitrobenzene wastewater to be treated exchanges heat with the materials extracted from the bottom of the removal tower through a first heat exchanger, the nitrobenzene wastewater after temperature rise enters the removal tower, and the materials at the bottom after temperature reduction enter the mill through a second heat exchanger. The gas phase material at the top of the removal tower enters a separating tank after being cooled by a cooler, the gas phase material discharged from the separating tank enters a waste gas treatment unit, and the discharged liquid phase material flows back into the removal tower. According to the invention, the nitrobenzene wastewater is efficiently utilized by definitely corroding the cause and removing the process measures, the unplanned shutdown risk is reduced, the cost expenditure of equipment updating and checking maintenance cost is reduced, the safe, stable and long-period operation of the coal gasification device is ensured, and the water resource saving and wastewater resource utilization capacity of enterprises is steadily improved.

Description

A kind of resource treatment process and treatment system of nitrobenzene wastewater

technical field

The invention relates to the technical field of wastewater treatment, in particular to a resource-based treatment process and a treatment system for nitrobenzene wastewater.

Background technique

Nitrobenzene is an important chemical synthesis intermediate, which is widely used in fine chemical, textile, printing and dyeing industries. Nitrobenzene is a toxic and suspected carcinogenic compound that can cause neurosis, anemia, liver disease, and cancer in humans and animals. Due to the above-mentioned hazards of nitrobenzene, the relevant departments of our country have formulated corresponding standards and strengthened the supervision of this substance.

Conventional treatment technologies for nitrobenzene wastewater include biochemical methods, electrolysis methods, reduction-oxidation methods, reduction methods, advanced oxidation methods, extraction methods, and adsorption methods. The biochemical method uses domesticated microorganisms or special microorganisms to degrade organic matter in a bioreactor. Electrolysis is a method of degrading organic matter by electrochemically generating atomic oxygen. The reduction-oxidation method is to first reduce the organic matter with a reducing agent, and then oxidize and degrade the organic matter with an oxidizing agent. Reduction method is the use of biological or chemical methods to reduce organic matter. Advanced oxidation is a method of decomposing organic matter using chemical oxidants. Extraction is the separation of contaminants by the selective partitioning of solutes between two immiscible solvents. The adsorption method is to use an adsorbent to adsorb pollutants on the adsorbent, thereby removing pollutants in wastewater. Commonly used adsorbents include activated carbon, fly ash, organic bentonite and resin.

However, the nitrobenzene wastewater produced in the production process has the characteristics of high microbial inhibition, high ammonia nitrogen, and high chroma, which leads to the unfavorable situation of high cost and low return for a long time in the existing conventional nitrobenzene wastewater treatment and disposal technology. The treatment of nitrobenzene wastewater has become one of the difficult problems in industrial wastewater treatment.

In recent years, with the continuous advancement of the concept of waste water resource utilization, the use of waste water instead of conventional water to prepare coal-water slurry, and the resource utilization of waste water through gasification have become universal, economical, and easy to operate. The high-efficiency technical means have shown positive significance in greatly reducing the cost and site of conventional wastewater treatment, and saving water resources. For the method of co-processing nitrobenzene wastewater with coal water slurry technology, please refer to reference 1:

Reference 1: Chinese patent document with patent publication number CN102417249A.

Reference 1 discloses a method for treating nitrobenzene wastewater. By using solution polymerization in the wastewater phase to prepare coal-water slurry additives, the pollution caused by the discharge of nitrobenzene wastewater to the environment is avoided, and nitrobenzene wastewater is realized. of reuse.

However, in the actual production process of co-processing nitrobenzene wastewater with coal-water slurry technology, due to the high salt content and complex composition of nitrobenzene wastewater, the corrosiveness of coal slurry increases, resulting in a series of corrosion-induced problems in mills and other equipment. Production problems, such as increased slurry leakage at the joints of cylinder bolts and increased equipment maintenance times, have seriously restricted the continuous and stable operation of the coal gasification plant.

In order to solve the above technical problems, the applicant proposed a solution, the specific content of which can be found in Reference 2:

Reference 2: Chinese Patent Document with Patent Publication No. CN114772794A.

Reference 2 discloses a method for co-processing nitrobenzene wastewater with coal-water slurry technology. The nitrobenzene wastewater is deoxidized, and then reacts with iron and nitrite in the nitrobenzene wastewater, and then the reacted Nitrobenzene wastewater, coal and additives are used to prepare coal water slurry. The technical solution proposes a method of corrosion control from the perspective of technology, eliminates the cause of corrosion, reduces unplanned shutdowns caused by corrosion problems, avoids excessive investment in material resources, manpower, financial resources and other costs of the enterprise, and ensures the safety and stability of the coal gasification device , Long-term operation, while steadily improving the ability of water resource conservation and waste water resource utilization.

However, in the above technical solution, iron-containing fillers need to be consumed during the pretreatment of nitrobenzene wastewater, which increases the cost of co-processing nitrobenzene wastewater with coal-water slurry technology.

Contents of the invention

The purpose of the present invention is to solve the problem of high operating cost of the co-processing of nitrobenzene wastewater by the coal water slurry technology in the prior art, and provide a resource-based treatment process and a treatment system for nitrobenzene wastewater.

In order to solve the deficiencies of the above-mentioned technical problems, the technical solution adopted by the present invention is: a resource-based treatment system for nitrobenzene wastewater, including a removal tower, a first heat exchanger, a cooler, a separation tank, a waste gas treatment unit, Second heat exchanger and mill;

The removal tower has a supersaturated steam inlet and a waste water inlet. The nitrobenzene waste water to be treated is exchanged with the material extracted from the bottom of the removal tower through the first heat exchanger, and the heated nitrobenzene waste water enters through the waste water inlet. In the removal tower, the cooled tower bottom material enters the mill through the second heat exchanger;

An acid injection unit is connected to the nitrobenzene wastewater feed pipe of the first heat exchanger, and an alkali injection unit is connected to the feed pipe of the mill;

The gas-phase material at the top of the removal tower enters the separation tank after being cooled by the cooler, the gas-phase material discharged from the separation tank enters the waste gas treatment unit, and the discharged liquid-phase material flows back into the removal tower.

As a further optimization of a resource treatment system for nitrobenzene wastewater in the present invention: the mill is a wet overflow mill, preferably a rod mill.

A process for resourceful treatment of nitrobenzene wastewater: the nitrobenzene wastewater to be treated enters the first heat exchanger after acid injection to adjust the pH value, and then exchanges heat with the material extracted from the bottom of the removal tower, and the nitrobenzene after heat exchange Wastewater enters the removal tower, and superheated steam is used in the removal tower to remove nitrite in the nitrobenzene wastewater. The top material of the removal tower enters the cooler and the separation tank in turn, and the gas phase material separated from the separation tank enters the waste gas treatment Unit, the liquid phase material separated from the separation tank is refluxed to the upper part of the removal tower, and the bottom material of the removal tower is heat-exchanged through the first heat exchanger and the second heat exchanger in turn, and the heat-exchanged material is regulated by the alkali injection unit After the pH level enters the mill.

As a further optimization of the nitrobenzene wastewater resource treatment process of the present invention: the nitrobenzene wastewater to be treated enters the first heat exchanger after being injected with acid to adjust the pH value to ≤3.

As a further optimization of the recycling process of nitrobenzene wastewater in the present invention: the acid used in the acid injection adjustment process is an inorganic acid containing H ⁺ , preferably sulfuric acid.

As a further optimization of the recycling process of nitrobenzene wastewater in the present invention: the temperature of the nitrobenzene wastewater in the removal tower is not lower than 90°C.

As a further optimization of the recycling process of nitrobenzene wastewater in the present invention: the residence time of nitrobenzene wastewater in the removal tower is ≥ 15 min, preferably ≥ 10 min.

As a further optimization of the recycling process of nitrobenzene wastewater in the present invention: the bottom material of the removal tower enters the mill after being injected with alkali to adjust the pH value to 7-10.

As a further optimization of the resource treatment process of a kind of nitrobenzene wastewater in the present invention: the alkali used in the alkali injection adjustment process is an inorganic alkali containing ^OH- .

As a further optimization of the recycling process of nitrobenzene wastewater in the present invention: the alkali used in the injection alkali adjustment process is one or more of caustic soda, quicklime or milk of lime and their solutions.

The present invention has the following beneficial effects: the present invention realizes the efficient utilization of nitrobenzene wastewater by clarifying the cause of corrosion and removing process measures, reduces the risk of unplanned shutdown, reduces the cost of equipment renewal and maintenance costs, and guarantees the safety of the coal gasification device. Safe, stable, and long-term operation, while steadily improving the company's water resource conservation and waste water resource utilization capabilities.

Description of drawings

Fig. 1 is the schematic flow sheet of the resource treatment system of nitrobenzene wastewater of the present invention;

Marked in the figure:

1. Removal tower;

2. The first heat exchanger;

3. Cooler;

4. Separation tank;

5. Exhaust gas treatment unit;

6. The second heat exchanger;

7. Mill.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Coal water slurry usually consists of 60-70% coal, 30-40% water and a small amount of additives. Since the preparation of coal-water slurry requires a large amount of water, based on the resource utilization of wastewater, nitrobenzene wastewater has been used instead of conventional water to prepare coal-water slurry. However, in the actual production process, due to the high salt content and complex components of nitrobenzene wastewater, the The corrosiveness of coal water slurry increases, resulting in corrosion of production equipment.

Nitrobenzene wastewater mainly refers to the wastewater generated during the neutralization, washing and rectification of crude nitrobenzene in alkaline solution. The applicant found that nitrite ions in nitrobenzene wastewater are the main cause of corrosion. When the content of nitrite ions in nitrobenzene wastewater decreases, the corrosion of equipment when coal water slurry technology co-treats nitrobenzene wastewater Sex is greatly reduced. In the previous technical scheme, the applicant used iron to react with nitrite in nitrobenzene wastewater, which can reduce the content of nitrite ions in nitrobenzene wastewater, especially when the content of nitrite in wastewater is reduced to ≤ When the concentration is 50 μg/g, the corrosion damage to equipment such as mills during the preparation of coal water slurry is greatly reduced.

As shown in Figure 1: a resource treatment system for nitrobenzene wastewater, including a removal tower 1, a first heat exchanger 2, a cooler 3, a separation tank 4, an exhaust gas treatment unit 5, and a second heat exchanger 6 and mill 7.

The removal tower 1 has a supersaturated steam inlet and a waste water inlet. The nitrobenzene wastewater to be treated is exchanged with the material extracted from the bottom of the removal tower 1 through the first heat exchanger 2. The heated nitrobenzene wastewater is passed through the waste water inlet. Enter the removal tower 1, and the cooled tower bottom material enters the mill 7 through the second heat exchanger 6.

The removal tower 1 can be a general tower with distribution pipes. The second heat exchanger is for heat exchange between materials and cooling water.

The nitrobenzene wastewater feed pipe of the first heat exchanger 2 is connected with an acid injection unit, and the feed pipe of the mill 7 is connected with an alkali injection unit.

The gas-phase material at the top of the removal tower 1 enters the separation tank 4 after being cooled by the cooler 3 , the gas-phase material discharged from the separation tank 4 enters the waste gas treatment unit 5 , and the discharged liquid-phase material flows back into the removal tower 1 .

Mill 7 is a wet overflow mill, and it is foreseeable that at least a rod mill may be used.

A resource treatment process for nitrobenzene wastewater. The process is based on the above-mentioned treatment system. The nitrobenzene wastewater to be treated enters the first heat exchanger to exchange heat with the material extracted from the bottom of the removal tower after being injected with acid to adjust the pH value. The heated nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower, and the top material of the removal tower enters the cooler and the separation tank in turn, and the separation tank separates The gaseous material in the gas phase enters the exhaust gas treatment unit, and the liquid phase material separated from the separation tank is refluxed to the upper part of the removal tower, and the bottom material of the removal tower is heat-exchanged through the first heat exchanger and the second heat exchanger in turn, and the heat exchanged The material enters the mill after adjusting the pH value through the alkali injection unit.

Nitrobenzene wastewater mainly refers to the wastewater generated during the neutralization, washing and rectification of crude nitrobenzene in alkaline solution.

The material at the bottom of the removal tower enters the mill after heat exchange and alkali injection, and the temperature after heat exchange is 50°C.

The first function of the superheated steam in the removal tower is heating, and the second function is to accelerate the removal of the gas phase.

The corrosion factor, that is, the process control index of nitrite is ≤50 μg/g, more preferably ≤40 μg/g.

The residence time of the nitrobenzene wastewater in the removal tower is ≥ 15 min, more preferably ≥ 10 min.

The nitrobenzene wastewater to be treated enters the first heat exchanger after being injected with acid to adjust the pH value to ≤3.

The acid used in the acid injection adjustment process is an inorganic acid containing H ⁺ , preferably sulfuric acid.

The temperature for removing nitrobenzene wastewater in the tower is not lower than 90°C.

The bottom material of the removal tower enters the mill after being injected with alkali to adjust the pH value to 7-10.

The base used in the base adjustment process is an inorganic base containing ^OH- .

Furthermore, the alkali used is one or more of caustic soda, quicklime or milk of lime and their solutions.

When nitrobenzene wastewater does not become coal slurry water, the core of nitrobenzene wastewater treatment technology (physical method, chemical method, biological method) is to remove nitrobenzene, so that the discharge of wastewater meets the requirements of environmental indicators, so nitrobenzene The amount of root content and the presence or absence of corrosion effects are not considered. When the nitrobenzene wastewater becomes coal slurry water, the corrosion problem of the mill equipment appears. After the research, we first proposed that the cause of the corrosion is nitrite, and then proposed the iron reduction method (reference document 2) to remove it by chemical method, but chemical The cost of the method is relatively high, so the acidizing boiling method is proposed.

The acidizing boiling method is only for nitrous acid, and it is the utilization of waste water resources, so as long as its corrosiveness can be reduced, other substances in the waste water do not need to be considered. The reason why this method is not applicable to all systems is that the starting point is different. For example, it is necessary to consider whether the target product is decomposed and reacted under acidification conditions. This requires not only the removal of nitrite, but also the removal of nitrite. The reduction of the target product avoids the loss outweighing the gain. In addition, nitrite is the cause of corrosion in the pulping process, which is not necessarily the case in another environment. It is specific to a certain extent. In other words, in a similar environment where it is determined that nitrite is the cause of corrosion, and Has a certain versatility.

Nitrite is unstable and easy to decompose under acidic conditions, but it takes time. In the actual continuous production process, it cannot be given enough time to slowly decompose. Therefore, those skilled in the art know that nitrite is unstable and easy to decompose under acidic conditions, but it is not easy to realize in production. It is not enough to consider acidification alone, and it must be combined with other methods, such as the boiling proposed in this patent.

3HNO ₂ =HNO ₃ +2NO+H ₂ O (acidification main reaction), partial removal can be seen.

2HNO ₂ =NO+NO ₂ +H ₂ O (the main reaction of acidification and heating), it can be seen that all of them are removed.

Heating and steaming are issues of enhanced efficiency and practicality.

<Example 1>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 2, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 30min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 2>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 30min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 3>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite radical in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 90°C. The removal time is 30min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 4>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 30min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 5>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 10min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 6>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 15min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Example 7>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 20min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Embodiment 8>

A nitrobenzene wastewater resource treatment process: the nitrobenzene wastewater to be treated is injected with acid to adjust the pH value, so that the pH value of the nitrobenzene wastewater is 3, and then enters the first heat exchanger and the bottom of the removal tower to extract the material After heat exchange, the nitrobenzene wastewater enters the removal tower, and the nitrite in the nitrobenzene wastewater is removed by heating with superheated steam in the removal tower. In the removal tower, the temperature at the bottom of the tower needs to be controlled at 100°C. The removal time is 30min (the residence time of nitrobenzene wastewater in the removal tower);

The top material of the removal tower enters the cooler and the separation tank in turn, the gas phase material separated from the separation tank enters the waste gas treatment unit, the liquid phase material separated from the separation tank flows back to the upper part of the removal tower, and the bottom material of the removal tower is sequentially After heat exchange between the first heat exchanger and the second heat exchanger, the material after heat exchange enters the mill after the pH value is adjusted by the alkali injection unit (pH control index is 7-10).

<Comparative Examples 1-3>

The treatment process of Comparative Example 1-3 is basically the same as the treatment process of <Example 1>, except that the pH values of the nitrobenzene wastewater in Comparative Example 1-3 after acid injection adjustment are 4, 5 and 4 respectively. 6.

<Comparative Examples 4-6>

The treatment process of Comparative Example 4-6 is basically the same as that of <Example 3>, except that the bottom temperature of the removal tower in Comparative Example 4-6 is controlled at 60°C, 70°C and 80°C.

<Comparative example 7>

The treatment process of Comparative Example 7 is basically the same as that of <Example 5>, except that the treatment time of the removal tower in Comparative Example 7 is 5 minutes.

<Example 1, 2> and <Comparative Example 1-3> pretreated wastewater is detected, and the sulfite content data obtained are shown in the table below:

group Nitrite concentration (μg/g) untreated wastewater 400 Example 1 (pH=2) 35 Example 2 (pH=3) 48 Comparative example 1 (pH=4) 303 Comparative example 2 (pH=5) 323 Comparative example 3 (pH=6) 327

It can be seen from the above table that when the nitrobenzene wastewater is acidified to a pH value ≤ 3, the removal effect of sulfite is better. And when the pH value of nitrobenzene wastewater after acidification treatment is greater than 3, the removal effect of sulfite becomes significantly worse. It can be seen that when acidifying nitrobenzene wastewater, the pH value needs to be limited within 3.

<Example 3, 4> and <Comparative Example 4-6> pretreated wastewater are detected, and the sulfite content data obtained are shown in the table below:

group Nitrite concentration (μg/g) untreated wastewater 400 Example 3 (90°C) 50 Example 4 (100°C) 40 Comparative example 4 (60°C) 174.9 Comparative example 5 (70°C) 172.6 Comparative example 6 (80°C) 150.6

It can be seen from the above table that when the nitrobenzene wastewater is heated and evaporated, when the temperature of the nitrobenzene wastewater is ≥90°C, the removal effect of sulfite is better. And when nitrobenzene waste is in the process of heating and steaming out, when the temperature of nitrobenzene wastewater is lower than 90°C, the removal effect of sulfite becomes significantly worse. It can be seen that, in the process of heating and steaming out of nitrobenzene wastewater, The temperature of nitrobenzene wastewater needs to be controlled above 90°C.

<Example 5-8> and <Comparative Example 7> pretreated waste water is detected, and the obtained sulfite content data are shown in the table below:

group Nitrite concentration (μg/g) untreated wastewater 415 Example 5 (10min) 48.1 Example 6 (15min) 35.4 Example 7 (20min) 32.1 Example 8 (30min) 31.8 Comparative example 7 (5min) 128

It can be seen from the above table that when the nitrobenzene wastewater is heated and evaporated for more than 10 minutes, the removal effect of sulfite is better. And when the nitrobenzene wastewater is heated and evaporated for less than 5 minutes, the removal effect of sulfite becomes significantly worse. It can be seen that the removal time should not be less than 10 minutes during the heating and steaming process of nitrobenzene wastewater.

The advantages of the nitrobenzene waste water resource treatment process of the present invention are:

1) The process further broadens its utilization by eliminating the corrosiveness of nitrobenzene wastewater;

2) It can effectively solve or slow down the corrosion problem of coal slurry equipment, reduce the risk of unplanned shutdown, and reduce the cost of inspection and maintenance;

3) This process ensures the continuous use of nitrobenzene wastewater, which is conducive to steadily improving the water-saving efficiency of enterprises.

4) The treatment process of this process is efficient, easy to implement, and low in cost, and is suitable for other limited use of wastewater caused by the same corrosion reasons.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. A nitrobenzene wastewater recycling treatment system is characterized in that: comprises a removal tower (1), a first heat exchanger (2), a cooler (3), a separation tank (4), an exhaust gas treatment unit (5), a second heat exchanger (6) and a mill (7);

the removing tower (1) is provided with a supersaturated steam inlet and a wastewater inlet, nitrobenzene wastewater to be treated exchanges heat with materials extracted from the tower bottom of the removing tower (1) through the first heat exchanger (2), the nitrobenzene wastewater after temperature rise enters the removing tower (1) through the wastewater inlet, and the tower bottom materials after temperature reduction enter the mill (7) through the second heat exchanger (6);

an acid injection unit is connected to a nitrobenzene wastewater feed pipe of the first heat exchanger (2), and an alkali injection unit is connected to a feed pipe of the mill (7);

the gas phase material at the top of the removal tower (1) enters a separation tank (4) after being cooled by a cooler (3), the gas phase material discharged from the separation tank (4) enters a waste gas treatment unit (5), and the discharged liquid phase material flows back into the removal tower (1).

2. The recycling treatment system of nitrobenzene wastewater according to claim 1, which is characterized in that: the mill (7) is a wet overflow mill (7), preferably a rod mill.

3. A recycling treatment process of nitrobenzene wastewater is characterized in that: the method is based on the processing system of claim 1 or 2, in particular: the method comprises the steps that nitrobenzene wastewater to be treated enters a first heat exchanger to exchange heat with materials extracted from the bottom of a removal tower after pH value adjustment through acid injection, the nitrobenzene wastewater after heat exchange enters the removal tower, nitrite in the nitrobenzene wastewater is removed by utilizing superheated steam heating in the removal tower, the materials at the top of the removal tower sequentially enter a cooler and a separating tank, gas-phase materials separated by the separating tank enter a waste gas treatment unit, liquid-phase materials separated by the separating tank flow back to the upper part of the removal tower, the materials at the bottom of the removal tower sequentially exchange heat through the first heat exchanger and a second heat exchanger, and the materials after heat exchange enter a mill after pH value adjustment through an alkali injection unit.

4. The recycling process of nitrobenzene wastewater, which is characterized in that: and the nitrobenzene wastewater to be treated enters a first heat exchanger after pH value is regulated to be less than or equal to 3 by acid injection.

5. The recycling process of nitrobenzene wastewater, which is characterized in that: the acid used in the process of regulating the acid injection contains H ⁺ Preferably sulfuric acid.

6. The recycling process of nitrobenzene wastewater, which is characterized in that: the temperature of nitrobenzene wastewater in the removal tower is not lower than 90 ℃.

7. The recycling process of nitrobenzene wastewater, which is characterized in that: the residence time of the nitrobenzene wastewater in the removal tower is more than or equal to 10min, preferably more than or equal to 15min.

8. The recycling process of nitrobenzene wastewater, which is characterized in that: and (3) regulating the pH value of the tower bottom material of the removal tower to 7-10 by alkali injection, and then entering the mill.

9. The recycling process of nitrobenzene wastewater, which is characterized in that: the alkali used in the alkali injection regulating process contains OH ^- Is an inorganic base of (a).

10. The recycling process of nitrobenzene wastewater, which is characterized in that: the alkali used in the alkali injection regulating process is one or more of caustic soda flakes, quicklime or lime milk and a solution thereof.