CN102008882A - Fenton reagent for denitration of power plant smoke and denitration method by using the same - Google Patents

Abstract

The invention provides a Fenton reagent for denitrating flue gas of a power plant and a method for using the reagent to denitrify flue gas. The reagent is a mixed aqueous solution composed of H ₂ O ₂ and FeSO ₄ , wherein the concentration of H ₂ O ₂ is 0.5-1mol/L, and the concentration of FeSO ₄ is 0.02-0.05mol/L. The method for denitration of flue gas includes three steps of pretreatment of flue gas, denitrification of flue gas and demisting of flue gas. The invention proposes a Fenton reagent for denitration of flue gas in a power plant and a method for denitrification by using it. The equipment not only has a simple structure and occupies less land, but also can achieve higher flue gas removal efficiency. In addition, in the process of the denitrification reaction, the oxidizing substance is ·OH free radical, and Cl ^- will not be generated in the reaction process, and secondary pollution such as Cl ₂ will not be produced.

Description

Fenton reagent for denitrification of power plant flue gas and method for denitrification using it

technical field

The invention relates to a method for removing NOx in flue gas of a power plant, in particular to a Fenton reagent for denitrifying the flue gas of a power plant and a method for using it to denitrify.

Background technique

NOx is a major air pollutant, which can not only cause acid rain, but also cause photochemical smog and cause ozone layer depletion. According to statistics, the _NOx emitted by coal combustion accounts for more than 67% of the total _NOx emission, causing great harm to human beings and the ecological environment. With the improvement of environmental protection requirements, many coal-fired boilers are required to reduce NOx emissions at the same time, and my country will implement more stringent NOx emission standards during the "Twelfth Five-Year Plan" period.

在脱硝过程中的还原产物为Cl

，增大了脱硝废液的处理过程的繁琐性。因此，在此基础上，提出利用Fenton试剂来脱除烟气中NO的方法。At present, the removal of NOx is divided into removal during combustion and removal after combustion, typical selective catalytic reduction method and selective non-catalytic reduction method. For the low NOx combustion technology, the denitrification efficiency is generally low, and may cause corrosion in the furnace, slagging, and even reduce the combustion efficiency. For the selective catalytic reduction method and the selective non-catalytic reduction method, although they have higher removal efficiency, they will make The equipment occupies a large area, the investment and operation costs are high, and it may even cause secondary pollution. Therefore, exploring new denitrification technologies is still a top priority. "A method for denitrification of flue gas with bleaching wastewater" proposed by the inventor has the following disadvantages: in the process of denitrification, Cl may be generated and cause secondary pollution; ( ₂ ) ClO

The reduction product in the denitrification process is Cl

, increasing the complexity of the denitrification waste liquid treatment process. Therefore, on this basis, a method of using Fenton's reagent to remove NO from flue gas is proposed.

Contents of the invention

The purpose of the present invention proposes a Fenton reagent for denitrification of power plant flue gas and a method for denitrification using it in order to improve denitrification efficiency and avoid secondary pollution after denitrification.

Technical principle of the present invention

和

等，从而被浆液吸收。其脱硝工艺技术所涉及的化学反应为：The Fenton reagent containing H ₂ O ₂ and FeSO ₄ fully contacts with the flue gas to oxidize the insoluble NO into

and

etc., thereby being absorbed by the slurry. The chemical reactions involved in its denitrification process technology are:

  （1） 

(1)

          （2）

(2)

        （3）                                                

(3)

     （4）                                              

(4)

               （5）                                                 

(5)

       （6）

(6)

The Fenton reagent is used as the NOx absorbent, which has a simple structure, occupies less land, and has high denitrification efficiency.

Technical scheme of the present invention

A kind of Fenton reagent that flue gas is carried out denitrification, it is characterized in that by H ₂ O ₂ and FeSO ₄ The mixed

Mixed solution, wherein the concentration of H ₂ O ₂ is 0.5-1mol/L, and the concentration of FeSO ₄ is 0.02-0.05mol/L.

Utilize a kind of above-mentioned method that flue gas is carried out denitrification Fenton reagent to carry out the method for denitrification, comprise the steps:

(1) Pretreatment of flue gas

The flue gas that needs to be denitrated is firstly pretreated by electrostatic precipitator to remove most of the solid particles in the flue gas;

(2) Denitrification of flue gas

Step (1) The flue gas after pre-dust removal is sent to the absorption tower 6 through the flue gas inlet 2 at the lower part of the flue gas absorption tower 6, and then the flue gas flows through the spray area 3 arranged staggeredly above the middle and upper part of the denitrification tower and is combined with the spray The Fenton reagent droplets sprayed from the spray layer in zone 3 are in countercurrent contact to complete denitrification; that is, the NO in it is oxidized by the Fenton reagent to easily soluble NO ₂ and then absorbed;

The oxidation temperature of the Fenton's reagent aqueous solution is 30-80°C, and the pH is 2-4;

(3) Demisting of flue gas

When the flue gas after denitrification in step (2) flows through the demister in the upper part of the absorption tower 6, the liquid droplets carried in the flue gas are removed, and the removed liquid drops fall into the bottom of the absorption tower 6 , is discharged from the overflow port 1 on the bottom side of the absorption tower 6, and the resulting clean flue gas is drawn from the flue gas outlet 5 at the top of the absorption tower 6 and discharged into the chimney.

The device used in the method of denitrification using the above-mentioned Fenton reagent for denitration of flue gas is a denitrification tower, which adopts a spray tower, including a denitrification tower body 6, an overflow port 1, a flue gas inlet 2, a Gas outlet 5, slurry spraying area 3, demisting area 4;

The overflow port is a U-shaped pipe. There are 3 or 4 staggered spray layers in the spray area, and depending on the denitrification effect, it may be considered to turn off part of the spray layers. The demisting area is used to remove the liquid droplets in the flue gas.

Beneficial effects of the present invention

OH自由基，在反应过程中不会生成Cl

，而且不会产生Cl₂等二次污染。吸收塔采用喷淋塔，能够让烟气与脱硝剂充分接触，达到较高的脱硝效率，在烟气进口处与水平面有一10-20°的角度，可是烟气进入脱硝塔后流程加长，减少对壁面的冲击，还可以延长气液接触时间，使得气液接触区域，气液两相流场分布更加均匀。The invention proposes a Fenton reagent for denitrification of flue gas and a method for denitrification by using it. Not only is the structure of the equipment simple and occupies less land, but it can also achieve high flue gas removal efficiency. In addition, in the process of the denitrification reaction, the oxidizing substance is

OH radicals, no Cl will be generated during the reaction

, and will not produce secondary pollution such as Cl ₂ . The absorption tower adopts a spray tower, which can fully contact the flue gas with the denitrification agent to achieve a high denitrification efficiency. There is an angle of 10-20° between the flue gas inlet and the horizontal plane, but the flow of the flue gas after entering the denitrification tower is lengthened and reduced. The impact on the wall can also prolong the gas-liquid contact time, making the gas-liquid two-phase flow field distribution more uniform in the gas-liquid contact area.

Description of drawings

Fig. 1, utilize the Fenton reagent of the present invention to carry out the structural representation of the device used in the method for power plant flue gas denitrification.

Detailed ways

The present invention will be further elaborated below by means of embodiments in conjunction with the accompanying drawings, but the present invention is not limited.

Fig. 1 is a structural schematic diagram of a device used in a method for denitrating power plant flue gas using the Fenton reagent of the present invention. According to the structural diagram shown in Figure 1, the denitrification tower includes an absorption tower 6, an overflow port 1, a flue gas inlet 2, a spray area 3, a demisting area 4 and a flue gas outlet 5;

The overflow port is a U-shaped liquid outlet channel;

There is an inclination angle of 10-20° between the flue gas inlet and the horizontal plane;

The spray area 3 is provided with 3 layers of staggeredly arranged Fenton reagent spray layers, and spray pipes and several nozzle pipes connected thereto are arranged in the spray layers;

The mist eliminator is on the upper part of the absorption tower to absorb the liquid droplets in the flue gas;

The flue gas outlet 5 is opened at the top of the absorption tower.

Example 1

Prepare mixed aqueous solutions with concentrations of H ₂ O ₂ and FeSO ₄ of 0.75mol/L and 0.05mol/L respectively, add them to the reactor, control the oxidation temperature of the Fenton reagent aqueous solution to 55°C, and adjust the pH to 3 to obtain the absorption solution .

Example 2

The above-mentioned absorption tower is used for denitrification with Fenton reagent. The flue gas discharged from the boiler has a flow rate of 6785m ³ /h after passing through the electrostatic precipitator, and the NO concentration is 1339ppm. The flue gas enters the absorption tower through the flue gas inlet 2 of the absorption tower 6, flows from bottom to top through the staggered spraying area 4, and reacts with the denitration agent in reverse contact to remove NO therein. The denitration agent containing Fenton's reagent is continuously transported to the spray area at a flow rate of 67.85m ³ /h, and sprayed out from the nozzle. The flue gas finally flows out from the flue gas outlet 5 and enters the chimney. The denitrification waste liquid flows out through the overflow port and enters the wastewater treatment device, thereby completing the denitrification process. At the flue gas outlet 5, use the Testo 350XL flue gas analyzer to measure the NOx concentration at the outlet, and the denitrification efficiency can be calculated to be 75.2%.

Example 3

Prepare mixed aqueous solutions with concentrations of H ₂ O ₂ and FeSO ₄ of 0.5mol/L and 0.02mol/L respectively, add them to the reactor, control the oxidation temperature of the Fenton reagent aqueous solution to 55°C, and adjust the pH to 3 to obtain an absorption solution. Other conditions are the same as in Example 2, and the calculated denitrification efficiency is 61.3%.

Example 4

Prepare a mixed aqueous solution with the concentrations of H ₂ O ₂ and FeSO ₄ at 1mol/L and 0.05mol/L respectively, add it to the reactor, control the oxidation temperature of the Fenton reagent aqueous solution to 55°C, adjust the pH to 3 to obtain the absorption solution, and others The conditions are the same as in Example 2, and the calculated denitrification efficiency is 70.5%.

On the premise of not departing from the process route and essence of the present invention, various modifications and changes can be made to the present invention, and these modifications and changes all belong to the scope of the appended claims.

Claims (7)

1. A Fenton reagent for denitrification of flue gas from a power plant, characterized in that it is a mixed aqueous solution composed of H ₂ O ₂ and FeSO ₄ , wherein the concentration of H ₂ O ₂ is 0.5-1mol/L, and the concentration of FeSO ₄ is 0.02-0.05 mol/L. 2. utilize the method for carrying out denitrification by the Fenton reagent that power plant flue gas is carried out denitrification as claimed in claim 1, it is characterized in that comprising the steps: (1) Pretreatment of flue gas The flue gas that needs to be denitrated is firstly pretreated by electrostatic precipitator to remove most of the solid particles in the flue gas; (2) Denitrification of flue gas Step (1) The flue gas after the pre-dust removal treatment is sent to the absorption tower (6) through the flue gas inlet (2) at the lower part of the flue gas absorption tower (6), and then the flue gas flows through the staggered spraying in the upper part of the denitrification tower area (3) and countercurrent contact with the Fenton reagent droplets sprayed from the spray layer of the spray area (3) to complete the denitrification; (3) Demisting of flue gas When the flue gas after denitrification in step (2) flows through the demister in the upper part of the absorption tower (6) and the demister area (4), the liquid droplets carried in the flue gas are removed, and the denitrated liquid drops fall into the absorption The bottom of the tower (6) is discharged from the overflow port (1) on the bottom side of the absorption tower (6), and the resulting clean flue gas is drawn from the flue gas outlet (5) at the top of the absorption tower (6) and discharged into the chimney. 3. The method for denitrification using Fenton reagent for denitrification of flue gas from power plants as claimed in claim 2, characterized in that the oxidation temperature of the Fenton reagent aqueous solution described in step (2) is 30-80°C, and the pH is 2 -4. 4. The method for denitrification by using Fenton reagent for denitrification of power plant flue gas as claimed in claim 3, characterized in that the oxidation temperature of the Fenton reagent aqueous solution used in step (2) is 55°C and the pH is 3. 5. The method for denitrification by using the Fenton reagent for denitrification of power plant flue gas as claimed in claim 2, 3 or ₄ , characterized in that the concentration of _H2O2 and _FeSO4 in the Fenton reagent used in step (2) They are 0.75mol/L and 0.05mol/L respectively. 6. As claimed in claim 3 or ₄ , the method for denitrification by using the Fenton reagent for denitrification of flue gas from a power plant is characterized in that the concentrations of _H2O2 and _FeSO4 in the Fenton reagent used in step (2) are respectively 0.5mol/L, 0.02mol/L. 7. The method for denitrification by using the Fenton reagent for denitrification of power plant flue gas as claimed in claim 2, 3 or ₄ , characterized in that the concentration of _H2O2 and _FeSO4 in the Fenton reagent used in step (2) They are 1mol/L and 0.05mol/L respectively.

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