Ozone liquid caustic soda denitration smelting flue gas treatment system

Abstract

The utility model relates to an ozone liquid caustic soda denitration smelting flue gas treatment system which comprises a flue, a booster fan is installed on the flue and connected with a gas inlet of a first-stage tubular reactor through a pipeline, and a gas outlet of the first-stage tubular reactor is sequentially connected with a first-stage absorption tower, a second-stage tubular reactor, a second-stage absorption tower and a third-stage washing tower through pipelines. Gas inlets of the first-stage tubular reactor and the second-stage tubular reactor are connected with an ozone generator through pipelines; and the third-stage washing tower is sequentially connected with an electric demister and a chimney through pipelines. The system adopts an ozone oxidation and alkali liquor denitration process to perform denitration treatment on the smelting flue gas, firstly, NO in the flue gas is oxidized into NO2 and N2O5 which are easy to absorb by utilizing ozone, then the NO2 and the N2O5 are subjected to an absorption reaction by utilizing an alkali liquor absorption tower, the oxidation efficiency of the ozone on the NO reaches 75% or above, the desulfurization rate reaches 97% or above, the denitration rate reaches 90% or above, and the denitration rate reaches 90% or above. And the NOX content of the purified and discharged flue gas is lower than the ultralow emission standard.

Description

Technical Field

[0001] The utility model relates to the technical field of smelting flue gas treatment, in particular to an ozone liquid alkali denitrification smelting flue gas treatment system. Background Art

[0002] In the process of metal smelting, a large amount of NO is often produced. X Exhaust gas, if it is not treated and discharged directly, will cause environmental pollution, so it is necessary to denitrate the exhaust gas. The more mature denitrification technologies currently include SCR denitrification technology and SNCR denitrification technology. Among them, SCR denitrification technology, namely the selective catalytic reduction method, is to inject ammonia or other suitable reducing agents into the flue gas upstream of the catalyst, so as to reduce the NO in the flue gas. X The reaction generates non-toxic and non-polluting N 2 and H 2 O; SNCR denitrification technology is a selective non-catalytic reduction technology. It is a technology that does not use a catalyst. In the temperature range of 850-1100℃, an amino-containing reducing agent (such as ammonia water, urea solution, etc.) is sprayed into the furnace to reduce NO in the flue gas. X Clean denitrification technology that generates nitrogen and water through reduction and removal. There are different problems in the implementation of these two denitrification technologies: SNCR denitrification technology has strict temperature requirements because it does not have a catalyst. If the temperature is too low, NO X Low conversion rate, high temperature, NH 3 It is easily oxidized to NO X , offsetting the NH 3 The removal efficiency is low, which leads to an increase in the amount of reducing agent used. In addition, the leakage of SNCR ammonia is large, which will cause secondary pollution to the atmosphere. In addition, when burning sulfur-containing fuels, due to the presence of (NH 4 ) 2 SO 4 The formation of SNCR will clog the air preheater. Due to the limitation of reaction temperature and ammonia leakage, the denitrification efficiency of SNCR is generally 30%~50%. The denitrification efficiency of SCR is higher, reaching more than 80%, but the technology investment is large and the maintenance cost is high. The catalyst needs to be replaced every 3 years. In addition, the system lacks systematic technical specifications and the standards are difficult to coordinate, which can easily cause confusion.

[0003] As the new environmental protection policy further lowers the standard for nitrogen oxide content in flue gas, there is an urgent need to provide a smelting flue gas treatment system with high denitrification efficiency and good economy. Utility Model Content

[0004] The utility model provides an ozone liquid alkali denitrification smelting flue gas treatment system. The ozone oxidation + alkali liquid denitrification process is used to denitrify the smelting flue gas, and the NO in the flue gas is oxidized into easily absorbable NO by ozone. 2 and N2 O 5， Reuse alkali solution to absorb NO 2 and N 2 O 5 , thereby achieving the purpose of denitrification.

[0005] The specific technical scheme of the utility model is: an ozone liquid alkali denitrification smelting flue gas treatment system, comprising a flue, on which a booster fan is installed, the booster fan is connected to the air inlet of a first-stage tubular reactor through a pipeline, the air outlet of the first-stage tubular reactor is sequentially connected to a first-stage absorption tower, a second-stage tubular reactor, a second-stage absorption tower, and a third-stage washing tower through a pipeline, the air inlets of the first-stage tubular reactor and the second-stage tubular reactor are connected to an ozone generator through a pipeline, and the third-stage washing tower is sequentially connected to an electric demister and a chimney through a pipeline.

[0006] Furthermore, preferably, the wastewater outlets of the primary absorption tower, the secondary absorption tower and the tertiary washing tower are connected to the wastewater treatment device through pipelines.

[0007] The beneficial effect of the utility model is that the system adopts ozone oxidation + alkali denitrification process to denitrify the smelting flue gas, firstly, ozone is used to oxidize NO in the flue gas into easily absorbable NO 2 and N 2 O 5 , and then use the alkali solution absorption tower to absorb NO 2 and N 2 O 5 The absorption reaction is carried out, and the oxidation efficiency of ozone to NO is more than 75%, the desulfurization rate is more than 97%, and the denitrification rate is more than 90%, purifying the exhaust gas NO X The content is lower than the ultra-low emission standard. The specific technical advantages are as follows:

[0008] (1) Ozone oxidation technology not only X It has a good removal effect and has a certain ability to remove other harmful pollutants in flue gas, such as heavy metal mercury. In addition, the oxidation reaction speed is fast, and NO can be oxidized into high-valent nitrogen oxides in a short time. Therefore, no special reaction equipment is required, and only a mixing space needs to be set up in the flue.

[0009] (2) The oxidation absorption process can be successfully completed under low temperature conditions, which is conducive to saving operating costs and reducing the difficulty of engineering construction. The investment is much lower than that of SCR denitrification technology, and the operating cost is comparable to that of SNCR denitrification technology, with good economic benefits;

[0010] (3) NO obtained by oxidation 2 With N 2 O 5The property of being easily soluble in water means that only a small amount of alkali solution is needed to completely absorb NO in the flue gas. X , which is beneficial to reduce the amount of spray liquid;

[0011] (4) The products of the alkaline solution absorption reaction can be crystallized and precipitated, which effectively realizes the solidification treatment of gaseous pollutants and avoids secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is an equipment association diagram of an ozone liquid alkali denitrification smelting flue gas treatment system of the utility model;

[0013] In the figure: 1-boosting fan, 2-ozone generator, 3-primary tubular reactor, 4-primary absorption tower, 5-secondary tubular reactor, 6-secondary absorption tower, 7-third-stage washing tower, 8-electric demister, 9-chimney, 10-wastewater treatment device. DETAILED DESCRIPTION

[0014] In order to make the technical problems and technical solutions solved by the utility model more clearly understood, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0015] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0016] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] Since more than 90% of NO in flue gas X NO is poorly soluble in water, has low reactivity, and is not easily absorbed. 2 O 5 It is easily soluble in water and easily absorbed. XThe present application proposes to utilize the strong oxidizing property of ozone to quickly and effectively oxidize NO into high-valent nitrogen oxides NO that are easily absorbed. 2 、N 2 O 5 Then, liquid alkali is used to absorb nitrogen oxides and convert them into water-soluble substances to achieve the purpose of denitrification. The specific process principle is as follows:

[0018] NO+O 3 =NO 2 +O 2

[0019] 2NO 2 +O 3 =N 2 O 5 +O 2

[0020] 2NO 2 +2NH 3 +H 2 O=NH 4 NO 2 +NH 4 NO 3

[0021] N 2 O 5 +2NH 3 +H 2 O =2NH 4 NO 3

[0022] Based on the above principles, Figure 1 As shown, the utility model provides an ozone liquid alkali denitrification smelting flue gas system, including a flue, on which a booster fan 1 is installed, the booster fan 1 is connected to the air inlet of the first-stage tubular reactor 3 through a pipeline, the air outlet of the first-stage tubular reactor 3 is connected to the first-stage absorption tower 4, the second-stage tubular reactor 5, the second-stage absorption tower 6, and the third-stage washing tower 7 in sequence through a pipeline, the air inlets of the first-stage tubular reactor 3 and the second-stage tubular reactor 5 are connected to the ozone generator 2 through a pipeline, the third-stage washing tower 7 is connected to the electric demister 8 and the chimney 9 in sequence through a pipeline, and the wastewater outlets of the first-stage absorption tower 4, the second-stage absorption tower 6 and the third-stage washing tower 7 are connected to the wastewater treatment device 10 through a pipeline.

[0023] The ozone generator 2 is used to produce ozone, and the ozone is arranged to enter the primary tubular reactor 3 and the secondary tubular reactor 5 to undergo oxidation reaction with the flue gas therein, and oxygen is provided to the ozone generator 2 when in use. The primary absorption tower 4 and the secondary absorption tower 6 are used to absorb nitrogen oxides and sulfur dioxide in the flue gas and convert them into water-soluble substances. XOxidized, control the reaction time, high oxidation state NO after the reaction X (x ≥ 1) It is easily soluble in water and absorbed by water to form nitric acid or nitrous acid. When in use, alkali solution (NaOH) needs to be added to the primary absorption tower 4 and the secondary absorption tower 6. A neutralization reaction occurs in the subsequent alkali absorption tower. At this time, the sulfur dioxide in the flue gas also reacts to form dilute sulfuric acid, which eventually reacts with caustic soda to form nitrates, nitrites, sulfites, etc. After absorption, the wet flue gas is further purified and cleaned by the electrostatic precipitator before being discharged. In order to maintain the balance of water in the absorption tower and control the salt content, regular water replenishment and drainage are required. The tertiary scrubber 7 is used to remove the remaining ozone. When in use, a reducing agent (carbon tetrachloride) is added to it. CCl 4 ).

[0024] During flue gas treatment, the wet flue gas at 50-70℃ treated by the Kaldo furnace and the rotary top-blown furnace is combined, and the combined flue gas air volume is 30,000 m 3 / h(NO X Content is 590~1400mg / m 3 , SO 2 Maximum 38 mg / m 3 , smoke dust maximum 5.5mg / m 3 ) is sucked into the primary tubular reactor 3 through the booster fan 1. At the same time, the ozone generator 2 arranges the produced ozone into the primary tubular reactor 3. Under the strong oxidizing effect of ozone, 75% or more of the NO in the flue gas is oxidized into high-valent nitrogen oxides, and then enters the primary absorption tower 4 to be absorbed by the added alkali solution and converted into water-soluble substances. The outlet of the primary absorption tower 4 is NO X The content is 235mg / m 3 ~580 mg / m 3 In order to further remove the remaining NO, the flue gas at the outlet of the primary absorption tower 4 continues to enter the secondary tubular reactor 5 and the secondary absorption tower 6, and undergoes oxidation and absorption processes again. X The content dropped to 2.50 mg / m 3 (much lower than 50mg / Nm 3 Ultra-low emission standards below), SO 2 The content was reduced to 0.95 mg / m 3 , the smoke content is reduced to 0.33mg / m 3 The flue gas that has completed denitrification then enters the tertiary scrubber 7 and the electrostatic precipitator 8 in sequence. The reducing agent added to the tertiary scrubber 7 will absorb and remove the remaining ozone from the reaction to avoid secondary pollution. The electrostatic precipitator 8 will intercept the acidic liquid mixed in the flue gas to complete gas-liquid separation. The purified gas is discharged through the chimney 9.

[0025] During the treatment process, the primary absorption tower 4, the secondary absorption tower 6, and the tertiary washing tower 7 need to maintain the balance of water in the tower and control the salt content. The pH value in the primary absorption tower 4 and the secondary absorption tower 6 needs to be controlled at about 9, so regular water replenishment and drainage are required. Generally, water replenishment controls the liquid level in the primary absorption tower 4 and the secondary absorption tower 6 to 1.6-2.2m according to the volatilization situation, and the external wastewater is drained and replenished according to the concentration of sodium nitrate in the solution is lower than 150g / L. Finally, the washing wastewater is collected and centralized for treatment in the factory wastewater treatment process.

[0026] After the smelting flue gas is treated by two-stage oxidation and two-stage absorption, the NO X The content dropped to 2.50 mg / m 3 、SO 2 The content was reduced to 0.95 mg / m 3 , the smoke content is reduced to 0.33mg / m 3 The ozone oxidation efficiency of NO is over 75%, the desulfurization rate is over 97%, the denitrification rate is over 90%, and the emission of flue gas NO is purified. X The content is lower than the ultra-low emission standard (50mg / Nm 3 the following).

[0027] The present invention is described in detail above through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the embodiments described above, and any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ozone liquid caustic soda denitrification smelting flue gas treatment system, comprising a flue, characterized in that: A booster fan (1) is installed on the flue. The booster fan (1) is connected to the air inlet of the first-stage tubular reactor (3) through a pipeline. The air outlet of the first-stage tubular reactor (3) is connected to the first-stage absorption tower (4), the second-stage tubular reactor (5), the second-stage absorption tower (6), and the third-stage washing tower (7) in sequence through a pipeline. The air inlets of the first-stage tubular reactor (3) and the second-stage tubular reactor (5) are connected to the ozone generator (2) through a pipeline. The third-stage washing tower (7) is connected to the electric demister (8) and the chimney (9) in sequence through a pipeline.

2. The ozone liquid caustic soda denitrification smelting flue gas treatment system according to claim 1 is characterized by: The wastewater outlets of the primary absorption tower (4), the secondary absorption tower (6) and the tertiary washing tower (7) are connected to the wastewater treatment device (10) via pipelines.

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