Flue gas treatment method and device

Abstract

The present application discloses a flue gas treatment method and device, which controls the temperature of the raw flue gas discharged from the lime shaft kiln within the range of 140°C to 150°C, so that the raw flue gas has a certain initial temperature, so that the raw flue gas still has a temperature of 130°C to 140°C after desulfurization and dust removal, thereby achieving low-temperature denitrification. The problem of difficulty in emission control when the lime shaft kiln is operated independently without the surrounding production line providing a heat source is avoided, and at the same time, there is no need to connect to gas to increase the raw flue gas temperature, thereby saving the engineering cost of connecting to the pipeline network and the cost of gas.

Description

Technical Field

[0001] The present invention relates to Flue gas treatment The technical field relates particularly to a flue gas treatment method and device. Background Art

[0002] Lime is mainly used in the construction or steel industry. The types and layouts of lime shaft kilns vary. Some are integrated with the steel production line, while others are independently arranged. The lime shaft kiln integrated with the steel production line can rely on the flue gas purification system of the steel production line to manage flue gas emissions. However, as a type of kiln with low energy consumption, the lime shaft kiln has a large number of independent operations in actual operation, which makes it difficult to effectively manage the original flue gas discharged from the lime shaft kiln. Summary of the invention

[0003] The present application provides a flue gas treatment method and device to solve the technical problem that the original flue gas discharged from a lime shaft kiln is difficult to effectively treat.

[0004] In view of the above problems, the present application is proposed to provide a flue gas treatment method and device that overcomes the above problems or at least partially solves the above problems.

[0005] In a first aspect, a flue gas treatment method is provided, which is applied to a lime shaft kiln. The flue gas treatment method comprises:

[0006] Control the temperature of the raw flue gas discharged from the lime shaft kiln to 140℃~150℃;

[0007] The original flue gas is desulfurized to obtain desulfurized flue gas, and the sulfur dioxide concentration in the desulfurized flue gas is less than 30mg / m 3 ;

[0008] Dedusting the desulfurized flue gas to obtain dedusted flue gas, wherein the dedusted flue gas has a temperature of 130° C. to 140° C.;

[0009] The dust-removed flue gas is denitrated to obtain purified flue gas.

[0010] Optionally, the lime shaft kiln comprises a cooling zone, a lower calcining zone, an upper calcining zone, and a preheating zone connected in sequence from bottom to top, and the raw flue gas is discharged from the lime shaft kiln through an outlet of the preheating zone;

[0011] Control the temperature of the raw flue gas discharged from the lime shaft kiln to 140℃~150℃, including:

[0012] The temperature of the preheating zone is controlled at 650°C to 700°C so that the temperature of the original flue gas is 140°C to 150°C.

[0013] Optionally, the dust-removed flue gas is subjected to denitrification to obtain purified flue gas, including:

[0014] The dust-removed flue gas is mixed with vaporized ammonia water and sent to the catalytic layer in the denitrification device, and the air velocity is controlled to be greater than or equal to 4500h -1 The working temperature is 120℃~130℃, and the purified flue gas is obtained, wherein the catalytic layer has a rare earth-based catalyst, and the nitrogen oxide concentration in the purified flue gas is less than 50mg / m 3 .

[0015] Optionally, the rare earth based catalyst includes iron, manganese, cerium, neodymium.

[0016] Optionally, the desulfurized flue gas is subjected to dust removal to obtain dust-removed flue gas, including:

[0017] The desulfurized flue gas is passed through the dust removal device for dust removal, and the dust removal resistance is controlled to be 1400Pa~1500Pa, so that the dust content of the dust-removed flue gas is less than 10mg / m 3 .

[0018] In a second aspect, a flue gas treatment device is provided, which is applied to a lime shaft kiln, wherein the temperature of the raw flue gas discharged from the lime shaft kiln is 140° C. to 150° C. The flue gas treatment device comprises:

[0019] The desulfurization device is used to desulfurize the original flue gas to obtain desulfurized flue gas. The sulfur dioxide concentration in the desulfurized flue gas is less than 30mg / m 3 in;

[0020] The dust removal device is used to remove dust from the desulfurized flue gas to obtain dust-removed flue gas, wherein the dust-removed flue gas has a temperature of 130° C. to 140° C.;

[0021] The denitrification device is used to denitrify the dust-removing flue gas to obtain purified flue gas.

[0022] Optionally, the lime shaft kiln includes a cooling zone, a lower calcining zone, an upper calcining zone, and a preheating zone which are sequentially connected from bottom to top, and the raw flue gas is discharged from the lime shaft kiln through the outlet of the preheating zone; the inlet of the desulfurization device is connected to the outlet of the preheating zone through a first pipe, the inlet of the dust removal device is connected to the outlet of the desulfurization device through a second pipe, and the inlet of the denitrification device is connected to the outlet of the dust removal device through a third pipe.

[0023] Optionally, the first pipe, the second pipe and the third pipe are covered with a thermal insulation layer.

[0024] Optionally, the inlet of the denitrification device is also connected to a vaporized ammonia source, and the denitrification device has a catalytic layer, which has a rare earth-based catalyst.

[0025] Optionally, the space velocity of the catalyst layer is greater than or equal to 4500h -1 The working temperature of the denitrification device is 120℃~130℃, so that the concentration of nitrogen oxides in the purified flue gas is less than 50mg / m3 .

[0026] The technical solution provided by this application has at least the following technical effects or advantages:

[0027] The flue gas treatment method and device provided in the present application controls the temperature of the raw flue gas discharged from the lime shaft kiln within the range of 140°C to 150°C, so that the raw flue gas has a certain initial temperature, so that the raw flue gas still has a temperature of 130°C to 140°C after desulfurization and dust removal, thereby achieving low-temperature denitrification. This avoids the problem that when the lime shaft kiln is independently operated without a heat source provided by the surrounding production line, it is difficult to obtain emission control, and at the same time, there is no need to connect to gas to increase the temperature of the raw flue gas, thereby saving the engineering cost of connecting to the pipeline network and the cost of gas.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0030] Figure 1 This is a flow chart of the flue gas treatment method in the embodiment of the present application;

[0031] Figure 2 This is a structural diagram of the flue gas treatment device in an embodiment of the present application. DETAILED DESCRIPTION

[0032] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0033] Various structural schematic diagrams according to embodiments of the present application are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0034] In order to better understand the above-mentioned technical scheme, the above-mentioned technical scheme will be described in detail below in combination with specific implementation methods. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical scheme of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0035] The steel industry's particulate matter, SO2, and NOx emissions account for 30.1%, 13.7%, and 15.7% of the national total, respectively, ranking first among the industries. Lime shaft kilns are major emitters and restrictive links of unorganized and organized emissions (particulate matter, SO2, and NOx) in the steel process, and usually have lower-level local emission standards that are higher than higher-level local standards.

[0036] For example, the emission standard for sulfur dioxide emission concentration from lime shaft kilns in Province A is 200 mg / Nm3. Based on environmental protection requirements, City B in Province A stipulates that the emission standard for sulfur dioxide emission concentration from lime shaft kilns is 100 mg / Nm3. Based on higher environmental protection requirements, County C in City B may stipulate that the emission standard for sulfur dioxide emission concentration from lime shaft kilns is 80 mg / Nm3.

[0037] Lime is mainly used in the construction or steel industry, so the types and layouts of lime shaft kilns vary. Some are integrated with steel production lines, while others are independently arranged. Among them, lime shaft kilns, as a type of kiln with low energy consumption, are operated independently in large quantities in actual operation. Under the background of national ecological civilization, meeting national and local pollutant emission standards has become a new issue for independently operated lime shaft kilns.

[0038] Taking the emission control of nitrogen oxides in vertical kiln flue gas as an example, the temperature of the raw flue gas discharged from the lime vertical kiln is usually only 90℃~100℃, while the existing denitrification technology requires an operating temperature of more than 180℃. It is necessary to connect gas far away from the factory to increase the raw flue gas temperature, which will lead to an increase in engineering expenses and costs.

[0039] On the other hand, there are differences in the quality and price of the gas connected. For example, if ordinary natural gas is used, although it can be connected from the nearby residential gas pipeline network and the engineering cost is low, the natural gas price is high, which may cause the company to fall into a loss for an independent lime shaft kiln with low profits. Other gases that can increase the temperature of the original flue gas may be cheaper, but the engineering cost of connecting to the pipeline network is higher.

[0040] The above problems will make it difficult for independently operated lime shaft kilns to survive. At the same time, as the local ecological and environmental departments implement online monitoring facilities for lime shaft kilns and upload monitoring data, ensuring that independent lime shaft kilns meet emission standards for flue gas pollutants has become a major environmental pain point for lime companies. At the same time, lime shaft kiln flue gas compliance management has also become a factor affecting the economic stability of other industries. Therefore, finding a control system that can achieve standard emission of flue gas from independent lime shaft kilns has become a technical problem that must be solved by independent lime shaft kilns at this stage.

[0041] In view of this, the present application provides a flue gas treatment method, which is applied to a lime shaft kiln, please refer to Figure 1 , Figure 1 This is a flow chart of the flue gas treatment method in the embodiment of the present application, including:

[0042] S101, controlling the temperature of the raw flue gas discharged from the lime shaft kiln to be 140°C to 150°C.

[0043] S102, desulfurize the original flue gas to obtain desulfurized flue gas, the sulfur dioxide concentration in the desulfurized flue gas is less than 30mg / m 3 .

[0044] S103, removing dust from the desulfurized flue gas to obtain dust-removed flue gas, wherein the dust-removed flue gas has a temperature of 130°C to 140°C.

[0045] S104, denitrifying the dust-removed flue gas to obtain purified flue gas.

[0046] The flue gas treatment method provided in the embodiment of the present application controls the temperature of the raw flue gas discharged from the lime shaft kiln within the range of 140°C to 150°C, so that the raw flue gas has a certain temperature, so that the raw flue gas still has a temperature of 130°C to 140°C after desulfurization and dust removal, thereby achieving low-temperature denitrification. This avoids the problem that when the lime shaft kiln is independently operated without a heat source provided by the surrounding production line, it is difficult to obtain emission control, and at the same time, there is no need to connect to gas to increase the temperature of the raw flue gas, thereby saving the engineering cost of connecting to the pipeline network and the cost of gas.

[0047] The lime shaft kiln includes a cooling zone, a lower calcining zone, an upper calcining zone, and a preheating zone connected in sequence from bottom to top, and the raw flue gas is discharged from the lime shaft kiln through the outlet of the preheating zone. In some optional embodiments, the operation of performing S101 is specifically: controlling the temperature of the preheating zone to 650°C to 700°C so that the temperature of the raw flue gas is 140°C to 150°C.

[0048] The temperature of the raw flue gas can be increased by controlling the operating temperature of the lime shaft kiln. This can be achieved in the following ways:

[0049] The first is to adjust the technical conditions of solid fuel in the lime shaft kiln, as shown in the following table:

[0050]

[0051] When the lime shaft kiln is in operation, the raw materials that need to be added are solid fuel and dolomite, which are burned in the lime shaft kiln to produce lime. Among them, the solid fuel uses smokeless carbon blocks, with a volatile content of less than or equal to 10%, an ash content of less than or equal to 4%, a moisture content of less than or equal to 0.4%, a sulfur content of less than or equal to 0.4, a calorific value of greater than or equal to 29.27MJ / kg, and a particle size range of 20 to 40mm. In this way, by controlling the composition of the solid fuel, the operating temperature of the lime shaft kiln preheat zone is controlled to be 650℃ to 700℃.

[0052] The second method is to control the coal ratio to 1:11.43~16.0, that is, the ratio of smokeless carbon blocks to dolomite, and control the working temperature of the lime shaft kiln preheating zone to 650℃~700℃ to control the temperature of the original flue gas to 140℃~150℃.

[0053] The third method is to control the material surface height in the lime shaft kiln to 3.6±0.3m. When the raw flue gas temperature is lower than 140℃, the material surface height is appropriately lowered to increase the raw flue gas temperature.

[0054] Fourthly, the combustion fan of the lime shaft kiln operates at 30±1HZ by default. When the flue gas temperature is lower than 140℃, the frequency of the combustion fan is increased. When the flue gas temperature is higher than 150℃, the frequency of the combustion fan is reduced. The frequency increases or decreases by 1HZ each time.

[0055] In the actual production process, the lime shaft kiln is usually equipped with furnace top equipment for cooling. In order to ensure the stable operation of the furnace top equipment after the flue gas temperature of the lime shaft kiln is increased, the furnace top equipment of the lime shaft kiln that mainly contacts the high-temperature flue gas can adopt a hot water tank structure. While ensuring the cooling of the furnace top equipment, heat exchange can generate a certain amount of hot water for the daily use of production line workers.

[0056] In some optional implementations, the operation of S102 may be performed by a dry desulfurization method, and the desulfurization agent may have the following indexes:

[0057]

[0058] In some optional implementations, the operation of S103 may be performed by using a bag dust removal method, and the resistance of the bag dust collector may be automatically controlled. The resistance of the bag dust collector may be 1400pa-1500pa, and the dust content of the flue gas may be less than 10mg / m 3 Perform system control.

[0059] In some optional embodiments, the operation of S104 may be performed by using an ultra-low temperature denitration method, where the dust-removed flue gas is mixed with vaporized ammonia water and then sent to the catalytic layer in the denitration device to obtain purified flue gas. The catalytic layer uses a rare earth-based catalyst containing iron, manganese, cerium, and neodymium as main components, and the space velocity of the catalytic layer is not less than 4500h -1 Since the original flue gas temperature is 140℃~150℃, it still maintains a temperature of 130℃~140℃ after sulfurization and dust removal. During denitrification, the working temperature can be guaranteed to be 120℃~130℃, reaching the working temperature of the rare earth-based catalyst.

[0060] Vaporized ammonia water is obtained by heating and vaporizing ammonia water. The quality requirements of ammonia water are shown in the following table:

[0061] project Main Ingredients <![CDATA[NH3·H2O]]> concentration 20％±1％ Residue content, mg / L <300 Chloride ion content, mg / L <300 Chroma number <80 Appearance indicators Colorless, transparent or slightly yellowish liquid

[0062] After the ammonia water is heated and vaporized by an electric heater, it is sent to the flue gas duct at the inlet of the warm denitrification device through a fan. The ammonia water appears as a colorless, transparent or slightly yellowish liquid with a concentration of 20±1%, a residue content of less than 300mg / L, a chloride ion content of less than 300mg / L, a chromaticity number of less than 80, and the temperature of the ammonia gas after heating and vaporization is controlled at 160℃~180℃.

[0063] The nitrogen oxide content of the original flue gas is about 250mg / m 3 After the above denitrification operation, the nitrogen oxide content is less than 50mg / m 3 Under such circumstances, the amount of ammonia water can be adjusted according to the flue gas volume and the nitrogen oxide content after denitrification, for example, according to 0.027±0.002ml / m 3 Indicators for control.

[0064] Based on the same inventive concept, the present application also provides a flue gas treatment device, please refer to Figure 2 , Figure 2 This is a schematic diagram of a flue gas treatment device in an embodiment of the present application. The flue gas treatment device 200 includes:

[0065] The desulfurization device 201 is used to desulfurize the original flue gas to obtain desulfurized flue gas, and the sulfur dioxide concentration in the desulfurized flue gas is less than 30 mg / m 3 in.

[0066] The dust removal device 202 is used to remove dust from the desulfurized flue gas to obtain dust-removed flue gas, wherein the dust-removed flue gas has a temperature of 130°C to 140°C.

[0067] The denitrification device 203 is used to denitrify the dust-removed flue gas to obtain purified flue gas.

[0068] The flue gas treatment device 200 is applied to the lime shaft kiln 204, and performs the operations of S101 to S104 in the above embodiment. By controlling the temperature of the raw flue gas discharged from the lime shaft kiln within the range of 140°C to 150°C, the raw flue gas has a certain initial temperature, so that the raw flue gas still has a temperature of 130°C to 140°C after desulfurization and dust removal, thereby achieving low-temperature denitrification. The problem of difficulty in emission control when the lime shaft kiln is independently operated without the surrounding production line providing a heat source is avoided, and at the same time, there is no need to connect to gas to increase the raw flue gas temperature, thereby saving the engineering cost of connecting to the pipeline network and the cost of gas.

[0069] In some optional embodiments, Figure 2 As shown, the lime shaft kiln 204 includes a cooling zone 2041, a lower calcining zone 2042, an upper calcining zone 2043, and a preheating zone 2044 which are sequentially connected from bottom to top, and the raw flue gas is discharged from the lime shaft kiln through the outlet of the preheating zone 2044; the inlet of the desulfurization device 201 is connected to the outlet of the preheating zone 2044 through a first pipeline, the inlet of the dust removal device 202 is connected to the outlet of the desulfurization device 201 through a second pipeline, and the inlet of the denitrification device 203 is connected to the outlet of the dust removal device 202 through a third pipeline.

[0070] The original flue gas at 140°C to 150°C enters the desulfurization device 201 from the preheating zone 2044 through the first pipeline for desulfurization, then enters the dust removal device 202 for dust removal through the second pipeline, and finally enters the denitrification device 203 for denitrification through the third pipeline. Finally, the purified flue gas can be directly discharged.

[0071] In some optional embodiments, the first pipe, the second pipe and the third pipe are covered with an insulation layer to ensure that the original flue gas still has a temperature above 130° C. after desulfurization and dust removal, thereby ensuring denitrification.

[0072] In some optional embodiments, the inlet of the denitrification device is also connected to a vaporized ammonia source, the denitrification device has a catalytic layer, the catalytic layer has a rare earth-based catalyst, the dust removal flue gas is mixed with the vaporized ammonia and then sent to the catalytic layer in the denitrification device, and the air velocity is controlled to be greater than or equal to 4500h -1 The working temperature is 120℃~130℃, and the purified flue gas is obtained. The concentration of nitrogen oxides in the purified flue gas is less than 50mg / m 3； Illustratively, the rare earth based catalyst includes iron, manganese, cerium, neodymium.

[0073] The flue gas treatment device provided in the embodiment of the present application is applied to an independently operated lime shaft kiln to solve the problem of flue gas emission compliance of a lime shaft kiln without surrounding gas source and heat source, realize economical emission compliance of flue gas from the lime shaft kiln, and promote the stable development of the lime industry.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0075] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Claims

1. A flue gas treatment method, characterized in that: Applied to a lime shaft kiln, the flue gas treatment method comprises: Control the temperature of the raw flue gas discharged from the lime shaft kiln to 140℃~150℃; The original flue gas is desulfurized to obtain desulfurized flue gas, wherein the sulfur dioxide concentration in the desulfurized flue gas is lower than 30 mg / m 3 ; Dedusting the desulfurized flue gas to obtain dedusted flue gas, wherein the dedusted flue gas has a temperature of 130° C. to 140° C.; The dust-removed flue gas is subjected to denitration to obtain purified flue gas.

2. The flue gas treatment method according to claim 1, characterized in that: The lime shaft kiln comprises a cooling zone, a lower calcining zone, an upper calcining zone, and a preheating zone connected in sequence from bottom to top, and the raw flue gas is discharged from the lime shaft kiln through the outlet of the preheating zone; The method of controlling the temperature of the raw flue gas discharged from the lime shaft kiln to be 140° C. to 150° C. comprises: The temperature of the preheating zone is controlled to be 650°C to 700°C, so that the temperature of the original flue gas is 140°C to 150°C.

3. The flue gas treatment method according to claim 1, characterized in that: The step of denitrifying the dust-removed flue gas to obtain purified flue gas comprises: The dust-removed flue gas is mixed with vaporized ammonia water and sent to the catalytic layer in the denitration device, and the air velocity is controlled to be greater than or equal to 4500h -1 , the working temperature is 120℃~130℃, the purified flue gas is obtained, wherein the catalytic layer has a rare earth-based catalyst, and the nitrogen oxide concentration in the purified flue gas is less than 50mg / m 3 .

4. The flue gas treatment method according to claim 1, characterized in that: The rare earth-based catalyst includes iron, manganese, cerium and neodymium.

5. The flue gas treatment method according to claim 1, characterized in that: The step of removing dust from the desulfurized flue gas to obtain the dust-removed flue gas comprises: The desulfurized flue gas is passed through a dust removal device to remove dust, and the dust removal resistance is controlled to be 1400Pa-1500Pa, so that the dust content of the dust-removed flue gas is less than 10mg / m 3 .

6. A flue gas treatment device, characterized in that: Applied to a lime shaft kiln, the temperature of the raw flue gas discharged from the lime shaft kiln is 140°C to 150°C, and the flue gas treatment device comprises: A desulfurization device is used to desulfurize the raw flue gas to obtain desulfurized flue gas, wherein the sulfur dioxide concentration in the desulfurized flue gas is less than 30 mg / m 3 in; A dust removal device is used to remove dust from the desulfurized flue gas to obtain dust-removed flue gas, wherein the dust-removed flue gas has a temperature of 130° C. to 140° C., and the dust-removed flue gas contains: The denitrification device is used to denitrify the dust-removing flue gas to obtain purified flue gas.

7. The flue gas treatment device according to claim 6, characterized in that: The lime shaft kiln comprises a cooling zone, a lower calcining zone, an upper calcining zone, and a preheating zone which are sequentially connected from bottom to top. The raw flue gas is discharged from the lime shaft kiln through the outlet of the preheating zone. The inlet of the desulfurization device is connected to the outlet of the preheating zone through a first pipeline, the inlet of the dust removal device is connected to the outlet of the desulfurization device through a second pipeline, and the inlet of the denitrification device is connected to the outlet of the dust removal device through a third pipeline.

8. The flue gas treatment device according to claim 7, characterized in that: The first pipe, the second pipe and the third pipe are covered with a thermal insulation layer.

9. The flue gas treatment device according to claim 6, characterized in that: The inlet of the denitration device is also connected to a vaporized ammonia source. The denitration device has a catalytic layer, and the catalytic layer has a rare earth-based catalyst.

10. The flue gas treatment device according to claim 9, characterized in that: The space velocity of the catalyst layer is greater than or equal to 4500 h -1 The operating temperature of the denitrification device is 120℃~130℃, so that the concentration of nitrogen oxides in the purified flue gas is lower than 50mg / m 3 .

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