High-concentration nitrogen oxide treatment system

Abstract

The utility model relates to a high-concentration nitrogen oxide treatment system which comprises an oxidation tower, an absorption tower, a neutralizing tower, a heat exchanger, a first fan, a second fan and a third fan, the bottom of the oxidation tower is connected with a gas inlet pipe, the top of the oxidation tower is provided with a first gas supply pipe connected to the bottom of the absorption tower, and the heat exchanger and the first fan are arranged on the first gas supply pipe; a second air supply pipe connected to the bottom of the neutralizing tower is arranged at the top of the absorption tower, a second fan is arranged on the second air supply pipe, an exhaust pipe is arranged at the top of the neutralizing tower, and a third fan is arranged on the exhaust pipe. The method comprises the steps of oxidation, cooling, absorption and neutralization. According to the system, nitrogen oxides in waste gas are subjected to large-scale adsorption treatment by using fewer series tower structures, so that the treatment result of a multi-stage series tower structure is achieved, and the cost of the system is saved.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection technology, and in particular to a high-concentration nitrogen oxide treatment system. Background Technology

[0002] Nitrogen oxides (NO) x Common components in exhaust gases include nitric oxide (NO), nitrous oxide (N₂O), nitrogen dioxide (NO₂), nitrous oxide (N₂O₃), nitrous oxide (N₂O₄), and nitrous oxide (N₂O₅), which are common air pollutants. Nitric oxide and nitrogen dioxide are particularly prevalent. This type of exhaust gas has a complex composition and is one of the main causes of acid rain. Methods for treating nitrogen oxides include reduction, plasma activation, biochemical methods, adsorption, and liquid absorption. Liquid absorption uses water or aqueous solutions of acids, alkalis, or salts to absorb nitrogen oxides from the exhaust gas, thus purifying it. Currently, most nitrogen oxide exhaust gas treatment devices are large-scale, multi-stage alkaline spray scrubbing towers, which suffer from problems such as large equipment size, high operating costs, and poor mass transfer efficiency. Furthermore, because NaOH has limited absorption capacity for NO₂ and NO, the treated exhaust gas still contains nitrogen oxides and has an acidic odor, failing to achieve the desired treatment effect. The redox method uses reducing agents, and during the reaction and decomposition process, gases such as ammonia and hydrogen sulfide are inevitably produced, causing new pollution.

[0003] Chinese patent CN217829533U discloses a system for reducing nitrogen oxides in exhaust gas. This system uses an oxidation tower and a seven-stage alkali absorption tower, resulting in a complex pipeline structure and high cost. Furthermore, even in the optimal state described in the embodiment, a very high NO level cannot be guaranteed. x Absorption rate.

[0004] Therefore, it is necessary to develop a new system and process to solve the above problems. Utility Model Content

[0005] The main objective of this invention is to provide a high-concentration nitrogen oxide treatment system that can perform large-scale adsorption treatment of nitrogen oxides in waste gas using fewer series tower structures, and the system cost is low.

[0006] This utility model achieves the above-mentioned objective through the following technical solution: a high-concentration nitrogen oxide treatment system, comprising an oxidation tower, an absorption tower, a neutralization tower, a heat exchanger, a first fan, a second fan, and a third fan. The bottom of the oxidation tower is connected to an inlet pipe, and the top of the oxidation tower is provided with a first gas supply pipe connected to the bottom of the absorption tower. The heat exchanger and the first fan are mounted on the first gas supply pipe. The top of the absorption tower is provided with a second gas supply pipe connected to the bottom of the neutralization tower, and the second fan is mounted on the second gas supply pipe. The top of the neutralization tower is provided with an exhaust pipe, and the third fan is mounted on the exhaust pipe.

[0007] Specifically, the upper part of the oxidation tower is provided with a first spray port and a second spray port, and the lower part of the oxidation tower is provided with a first pH sensor and an ORP potentiometer. The first pH sensor obtains the pH value of the liquid in the tower and is used to control the opening and closing of the first spray port. The ORP potentiometer obtains the oxidation-reduction potential value of the liquid in the tower and is used to control the opening and closing of the second spray port. The oxidation tower is provided with a first circulation pipe connecting the top and the bottom, and the first circulation pipe is provided with a first circulation pump that pumps the liquid in the tower from the bottom to the top.

[0008] Specifically, the top of the absorption tower is provided with a third spray port, and the absorption tower is provided with a second circulation pipe connecting the top and the bottom. The second circulation pipe is provided with a second circulation pump that pumps the liquid in the tower from the bottom to the top.

[0009] Specifically, the neutralization tower is provided with a fourth spray port at the top and a second pH sensor at the bottom. The second pH sensor acquires the pH value of the liquid in the tower and is used to control the opening and closing of the fourth spray port. The neutralization tower is provided with a third circulation pipe connecting the top and bottom, and a third circulation pump is provided on the third circulation pipe to pump the liquid in the tower from the bottom to the top.

[0010] The beneficial effects of this utility model's technical solution are:

[0011] This system uses fewer series tower structures to perform large-scale adsorption treatment of nitrogen oxides in waste gas, achieving the treatment results of a multi-stage series tower structure, thus saving system costs. Attached Figure Description

[0012] Figure 1 This is a piping diagram of a high-concentration nitrogen oxide treatment system as an example.

[0013] The numbers in the diagram represent:

[0014] 1a - Oxidation tower, 1b - Absorption tower, 1c - Neutralization tower;

[0015] 2-Heat exchanger;

[0016] 3a - First fan, 3b - Second fan, 3c - Third fan;

[0017] 4a - Intake pipe, 4b - First air supply pipe, 4c - Second air supply pipe, 4d - Exhaust pipe;

[0018] 5a - First spray nozzle, 5b - Second spray nozzle, 5c - Third spray nozzle, 5d - Fourth spray nozzle;

[0019] 6a - First pH sensor, 6b - Second pH sensor;

[0020] 7-ORP Potentiometer;

[0021] 8a - First circulation tube, 8b - Second circulation tube, 8c - Third circulation tube;

[0022] 9a - First circulation pump, 9b - Second circulation pump, 9c - Third circulation pump. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments.

[0024] Example:

[0025] like Figure 1 As shown, this utility model discloses a high-concentration nitrogen oxide treatment system, including an oxidation tower 1a, an absorption tower 1b, a neutralization tower 1c, a heat exchanger 2, a first fan 3a, a second fan 3b, and a third fan 3c. The bottom of the oxidation tower 1a is connected to an inlet pipe 4a, and the top of the oxidation tower 1a is provided with a first gas supply pipe 4b connected to the bottom of the absorption tower 1b. The heat exchanger 2 and the first fan 3a are mounted on the first gas supply pipe 4b. The top of the absorption tower 1b is provided with a second gas supply pipe 4c connected to the bottom of the neutralization tower 1c. The second fan 3b is mounted on the second gas supply pipe 4c. The top of the neutralization tower 1c is provided with an exhaust pipe 4d, and the third fan 3c is mounted on the exhaust pipe 4d.

[0026] Three fans are used to make the waste gas to be treated pass through oxidation tower 1a, heat exchanger 2, absorption tower 1b and neutralization tower 1c in sequence. The nitrogen oxides in the waste gas are oxidized into nitrogen dioxide in oxidation tower 1a, the temperature of nitrogen dioxide is reduced by heat exchanger 2, and then absorbed and converted into nitric oxide in absorption tower 1b. Finally, neutralization tower 1c absorbs nitric oxide and nitrogen dioxide into salt.

[0027] like Figure 1As shown, the upper part of the oxidation tower 1a is provided with a first spray port 5a and a second spray port 5b. The lower part of the oxidation tower 1a is provided with a first pH sensor 6a and an ORP potentiometer 7. The first pH sensor 6a obtains the pH value of the liquid in the tower and is used to control the opening and closing of the first spray port 5a. The ORP potentiometer 7 obtains the oxidation-reduction potential value of the liquid in the tower and is used to control the opening and closing of the second spray port 5b. The oxidation tower 1a is provided with a first circulation pipe 8a connecting the top and the bottom. The first circulation pipe 8a is provided with a first circulation pump 9a that pumps the liquid in the tower from the bottom to the top.

[0028] The first spray nozzle 5a provides NaOH solution to remove acidic gases from the waste gas, maintaining a strongly alkaline reaction environment for the oxidant. The first pH sensor 6a detects whether the liquid inside the tower remains strongly alkaline, preventing NaClO from decomposing under acidic conditions. The second spray nozzle 5b provides NaClO as an oxidant, reducing nitrogen oxides to NO2 in an alkaline and weakly potential environment, thus ensuring a relatively homogeneous composition of the gas entering the absorption tower 1b. Because the reaction always occurs after the gas comes into contact with the solution, the concentration of substances in the solution gradually becomes uneven. The first circulating pump 9a causes the liquid in the oxidation tower 1a to flow up and down, mixing it evenly. This makes the first pH sensor 6a and the ORP potentiometer 7 sensitive to changes in the tower conditions, allowing for timely replenishment of reagents and promoting a more complete reaction of nitrogen oxides.

[0029] like Figure 1 As shown, the top of the absorption tower 1b is provided with a third spray port 5c, and the absorption tower 1b is provided with a second circulation pipe 8b connecting the top and bottom. The second circulation pipe 8b is provided with a second circulation pump 9b that pumps the liquid in the tower from the bottom to the top.

[0030] The nitrogen elements treated by oxidation tower 1a are primarily in the form of nitrogen dioxide. Absorption tower 1b allows nitrogen dioxide to react with water to produce dilute nitric acid and nitric oxide. The second circulation pump 9b mixes the solution in absorption tower 1b, ensuring sufficient contact between nitrogen dioxide and water and improving absorption efficiency.

[0031] like Figure 1 As shown, the neutralization tower 1c is provided with a fourth spray port 5d at the top and a second pH sensor 6b at the bottom. The second pH sensor 6b obtains the pH value of the liquid in the tower and is used to control the opening and closing of the fourth spray port 5d. The neutralization tower 1c is provided with a third circulation pipe 8c connecting the top and bottom. The third circulation pipe 8c is provided with a third circulation pump 9c that pumps the liquid in the tower from the bottom to the top.

[0032] Most of the nitrogen treated in absorption tower 1b remains in absorption tower 1b as nitric acid, while a small portion enters neutralization tower 1c in the form of nitric oxide and nitrogen dioxide. The sodium hydroxide in neutralization tower 1c reacts with these two substances to form sodium nitrate and sodium nitrite, thus more thoroughly removing nitrogen from the exhaust gas. The third circulation pump 9c mixes the solution in neutralization tower 1c, allowing the gas to fully contact the NaOH solution and improving absorption efficiency.

[0033] The steps for treating high concentrations of nitrogen oxides are as follows:

[0034] S1. Under room temperature conditions, NaOH solution is added into oxidation tower 1a through the first spray port 5a to control the pH in the tower to >10.5. At the same time, NaClO solution is added into oxidation tower 1a through the second spray port 5b to control the ORP in the tower to >300mV. The first fan 3a draws nitrogen oxides into oxidation tower 1a for oxidation treatment to obtain primary waste gas.

[0035] The main reaction occurring in oxidation tower 1a is: NaClO + NO → NO2 + NaCl.

[0036] This reaction oxidizes nitric oxide, which constitutes a large proportion of the waste gas, into nitrogen dioxide, which then reacts more readily with water to produce nitric acid. Because oxidation tower 1a has a relatively large processing capacity, the reaction conditions need to be controlled. Since nitrogen dioxide is an acidic gas, it will consume some sodium hydroxide; therefore, to ensure continuous treatment, the solution needs to be maintained at an alkaline level. The first pH sensor 6a monitors the pH of the solution in oxidation tower 1a in real time. When sodium hydroxide consumption causes the pH to drop below 10.5, the first spray port 5a will replenish the alkaline solution to bring the pH back above 10.5. Potential affects the oxidation efficiency of sodium hypochlorite, so it also needs to be maintained above 300mV. If the ORP (oxidation-reduction potential) is lower than this value, the second spray port 5b needs to replenish the sodium hypochlorite solution. This improves the stability of the reaction within oxidation tower 1a.

[0037] S2 and the second fan 3b draw the primary exhaust gas into the heat exchanger 2, reducing the temperature of the primary exhaust gas to 10-25℃ before it enters the absorption tower 1b.

[0038] Because the reaction between nitrogen dioxide and water is partially reversible, excessively high temperatures can cause the newly formed dilute nitric acid to decompose back into NO2, leading to a decrease in absorption efficiency. Therefore, heat exchanger 2 is needed to lower the temperature of the nitrogen dioxide, ensuring that the temperature of absorption tower 1b remains stable and at a safe level.

[0039] S3. Add water to the absorption tower 1b through the third spray port 5c, so that the primary waste gas reacts with the water to produce dilute nitric acid and secondary waste gas.

[0040] The main reaction occurring inside absorption tower 1b is: 3NO2 + H2O → 2HNO3 + NO.

[0041] The solution in absorption tower 1b is continuously circulated and comes into contact with nitrogen dioxide. Nitrogen in the nitrogen dioxide undergoes a disproportionation reaction, with two-thirds of the nitrogen being transferred to nitric acid and remaining in absorption tower 1b. The remaining one-third of the nitrogen is reduced to nitric oxide, which is then further adsorbed in neutralization tower 1c. Nitric acid accumulates in absorption tower 1b to a certain amount and is then discharged as dilute nitric acid for recycling, a simple process.

[0042] S4. Under room temperature conditions, NaOH solution is added into neutralization tower 1c through the fourth spray port 5d to control the pH in the tower to >10.5. The third fan 3c draws the secondary waste gas into neutralization tower 1c. After passing through the NaOH solution, the exhaust gas is obtained and discharged into the atmosphere.

[0043] The main reaction occurring in neutralization tower 1c is: NO + NO2 + 2NaOH → 2NaNO2 + H2O.

[0044] Nitrogen dioxide is slightly in excess, but it will still participate in the reaction. The product, sodium nitrite, is soluble in water and can be easily collected and treated. Theoretically, there should be no nitrogen oxide residue in this step, and the nitrogen content in the exhaust gas will be less than 100 ppm, which can directly meet the national emission standards.

[0045] In this embodiment, the concentration of NaOH solution is 30–50 wt%, and the concentration of NaClO solution is 10–13 wt%. The reagents are readily available, and concentration control is simple.

[0046] This system uses fewer series-connected tower structures to perform large-scale adsorption treatment of nitrogen oxides in waste gas, achieving the treatment results of multi-stage series-connected tower structures while saving system costs. The treatment method can remove nitrogen oxides while reducing the introduction of other elements and recovering dilute nitric acid, thus saving energy and reducing emissions.

[0047] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. A high concentration nitrogen oxides treatment system characterized by: The application relates to a device for treating waste gas, which comprises an oxidation tower, an absorption tower, a neutralization tower, a heat exchanger, a first fan, a second fan and a third fan, the bottom of the oxidation tower is connected with an air inlet pipe, the top of the oxidation tower is provided with a first air supply pipe connected with the bottom of the absorption tower, the heat exchanger and the first fan are arranged on the first air supply pipe, the top of the absorption tower is provided with a second air supply pipe connected with the bottom of the neutralization tower, the second fan is arranged on the second air supply pipe, the top of the neutralization tower is provided with an air exhaust pipe, and the third fan is arranged on the air exhaust pipe.

2. The high concentration nitric oxide treatment system of claim 1, wherein: The upper part of the oxidation tower is provided with a first spraying opening and a second spraying opening, the lower part of the oxidation tower is provided with a first pH sensor and an ORP potential instrument, the first pH sensor acquires the pH value of liquid in the tower and is used for controlling the switch of the first spraying opening, the ORP potential instrument acquires the oxidation-reduction potential value of liquid in the tower and is used for controlling the switch of the second spraying opening, the oxidation tower is provided with a first circulation pipe connected with the top and the bottom, and the first circulation pipe is provided with a first circulation pump for pumping liquid in the tower from the bottom to the top.

3. The high concentration nitric oxide treatment system of claim 1, wherein: The top of the absorption tower is provided with a third spraying opening, the absorption tower is provided with a second circulation pipe connected with the top and the bottom, and the second circulation pipe is provided with a second circulation pump for pumping liquid in the tower from the bottom to the top.

4. The high concentration nitric oxide treatment system of claim 1, wherein: The top of the neutralization tower is provided with a fourth spraying opening, the bottom of the neutralization tower is provided with a second pH sensor, the second pH sensor acquires the pH value of liquid in the tower and is used for controlling the switch of the fourth spraying opening, the neutralization tower is provided with a third circulation pipe connected with the top and the bottom, and the third circulation pipe is provided with a third circulation pump for pumping liquid in the tower from the bottom to the top.

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