Method and system for reducing concentration of oxynitride in flue gas of glass kiln

Abstract

The invention discloses a method and a system for reducing the concentration of oxynitride in flue gas of a glass kiln. The system comprises a urea injection unit, a smoke exhaust unit and a control unit, the smoke exhaust unit comprises a first flue and a second flue, the first flue is vertically arranged, and the second flue is horizontally arranged and provided with a catalyst module; the urea spraying unit comprises a urea container, a urea pump and a urea spraying gun which are sequentially connected through a pipeline, and a gun body of the urea spraying gun is vertically arranged in the first flue; the urea spraying unit further comprises a first adjusting valve, and the first adjusting valve is arranged between the urea spraying gun and the urea pump. SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) are combined, urea only needs to be sprayed in the vertical first flue to be decomposed into ammonia gas at high temperature to react with NOx, the rest ammonia gas can continue to be subjected to SCR reaction in the second flue, ammonia liquid does not need to be additionally supplemented, ammonia escape can be reduced, the urea utilization rate is increased, the content of nitric oxide in flue gas can be reduced to 60 mg / m < 3 > or below, and the SCR effect is improved. And the required emission standard is reached.

Description

Technical Field

[0001] This invention relates to the field of glass manufacturing, and in particular to a method and system for reducing the concentration of nitrogen oxides in the flue gas of glass furnaces. Background Technology

[0002] During the operation of pure oxygen glass furnaces, the generated flue gas contains a large amount of nitrogen oxides, causing serious environmental pollution. Therefore, denitrification treatment of the flue gas generated during the operation of pure oxygen glass furnaces is necessary. The main denitrification technologies for glass furnace flue gas are SCR and SNCR, with SCR being the most mature. Its reaction mechanism involves injecting ammonia or other reducing agents into the flue gas, utilizing an alkali metal catalyst to catalyze the removal of NO from the flue gas at 200–450℃. x It reacts with a reducing agent to convert to N2. However, due to the complex composition of flue gas, highly dispersed dust in the flue gas easily covers the catalyst surface, reducing its activity and decreasing the utilization rate of ammonia to some extent. SNCR technology uses ammonia or urea as a reducing agent, injecting the reducing agent into flue gas at 850-1100℃ to convert NO in the flue gas into N2. x It converts to N2 and water, but this technology has low denitrification efficiency, strict temperature requirements, and produces NO. x Low conversion rate.

[0003] Currently, there are reports of combining SNCR and SCR technologies in flue gas denitrification of coal-fired boilers in thermal power plants. For example, CN106178870A discloses an NCR-SCR combined flue gas denitrification system suitable for coal-fired boilers. The flue at the boiler outlet is a horizontal flue, and an ammonia injection grid is installed in this horizontal flue. The SNCR denitrification reaction then takes place in the horizontal flue. The flue gas then enters the main flue, where a high-temperature heat exchanger, a low-temperature heat exchanger, and an economizer are installed. Below the economizer, an SCR reactor and an air preheater are installed sequentially, and the SCR reaction then takes place in the vertical main flue. However, this denitrification system has high equipment costs and a high initial investment. This combined denitrification technology cannot meet the denitrification requirements of glass kiln flue gas. Summary of the Invention

[0004] In view of this, the present invention proposes a glass furnace flue gas denitrification system, which combines SNCR and SCR technologies for continuous denitrification, significantly improving the flue gas denitrification efficiency. The present invention also proposes a method for reducing the concentration of nitrogen oxides in glass furnace flue gas based on the glass furnace flue gas denitrification system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The glass kiln flue gas denitrification system of the present invention includes a urea injection unit and a flue gas exhaust unit connected to the flue gas outlet of the glass kiln, and also includes a control unit; the flue gas exhaust unit includes a first flue and a second flue connected to the flue gas outlet, the first flue is arranged vertically, the second flue is arranged horizontally and connected to the upper part or top of the first flue, and a catalyst module is arranged in the second flue. The urea injection unit includes a urea container, a urea pump, and a urea spray gun connected in sequence by pipelines. The spray gun body is vertically arranged in the first flue. The urea injection unit also includes a first regulating valve, which is arranged between the urea spray gun and the urea pump. The control unit includes a controller, a first sensor for detecting the temperature of flue gas upstream of the second flue, and a second sensor for detecting the concentration of nitrogen oxides in the second flue. The signal output terminals of the first and second sensors are connected to the signal input terminals of the controller, and the control output terminal of the controller is connected to the control input terminals of the first regulating valve and the urea pump.

[0006] The beneficial effects are as follows: This invention changes the traditional glass furnace flue, vertically setting the first flue directly connected to the glass furnace. This slows down the flow velocity, thus reducing the impact on downstream catalysts, and promotes the SNCR reaction between nitrogen oxides and urea in the flue gas, improving denitrification efficiency. This invention combines SNCR and SCR technologies, requiring only urea injection in the first flue. The urea is converted into ammonia, which reacts with nitrogen oxides. The remaining ammonia can continue the SCR reaction in the second flue, eliminating the need for additional ammonia replenishment and reducing ammonia slip (which can be controlled below 5%). This improves urea utilization, reduces reducing agent usage, and thus lowers operating costs. Furthermore, this invention can reduce the nitrogen oxide content in the flue gas to 60 mg / m³. 3 Within the specified range, the required emission standards must be met.

[0007] Preferably, the urea spray gun is a pneumatic atomizing spray gun, and a second regulating valve is provided at its compressed air inlet. The control input terminal of the second regulating valve is connected to the control output terminal of the controller. In actual operation, the present invention utilizes the controller to control the second regulating valve, and the second regulating valve and the first regulating valve are controlled in a coordinated manner.

[0008] Preferably, the nozzle of the urea spray gun extends vertically into the first flue by 1m or more, so that the urea solution is atomized in the reaction area of ​​the first flue, thereby maximizing the denitrification efficiency.

[0009] Preferably, a cooling coil is also provided on the lower part of the outer wall of the first flue; a third sensor for detecting the flue gas temperature is provided on the lower inner side of the first flue, and the signal output terminal of the third sensor is connected to the signal input terminal of the controller. In actual operation, due to the high temperature inside the glass furnace, the temperature of the flue gas coming out of the glass furnace is relatively high. When it exceeds a certain temperature range, a cooling medium can be introduced into the cooling coil to control the temperature of the reaction zone of the first flue within a preset range.

[0010] Preferably, the first and third sensors are thermocouples. In actual installation, type K, type S, or type B thermocouples can be used to meet the temperature measurement requirements of the flue gas unit. The second sensor is preferably a nitrogen oxide detection sensor, used to detect the concentration of nitrogen oxides in front of the catalyst module.

[0011] Preferably, the glass furnace flue gas denitrification system of the present invention further includes an auxiliary heating device disposed upstream of the catalyst module. When the flue gas temperature upstream of the catalyst module is below 400°C, auxiliary heating is applied to the flue gas to ensure the SCR reaction temperature of the flue gas.

[0012] This invention also proposes a method for reducing the concentration of nitrogen oxides in glass furnace flue gas. This method employs the glass furnace flue gas denitrification system of this invention, comprising the following steps: spraying urea solution into the lower part of the first flue to form a urea spray, where an SNCR reaction occurs at the lower part of the first flue at a reaction temperature of 950℃-1100℃; when the flue gas in the first flue flows into the second flue, an SCR reaction occurs at the catalyst module, and the flue gas temperature at the catalyst module is controlled at 350℃-430℃.

[0013] Preferably, the flow rate of the urea solution is 1.0-5.0 L / h, and the concentration of the urea solution is 10%-30%.

[0014] Preferably, the flue gas velocity in the exhaust unit is 4-8 m / s.

[0015] Compared with the prior art, the present invention installs a vertical flue at the flue gas outlet of the glass furnace, which can directly perform SNCR denitrification treatment on the high-temperature flue gas, and then perform SCR denitrification treatment in the horizontal flue. No additional auxiliary denitrification equipment is required, which can improve the flue gas denitrification rate and reduce the initial investment.

[0016] Furthermore, this invention uses urea as a reducing agent. Under high-temperature conditions, urea is converted into ammonia and reacts with nitrogen oxides. The remaining ammonia can continue to undergo SCR reaction in the second flue, eliminating the need for additional ammonia replenishment, reducing ammonia slip (which can be controlled within 5%), improving urea utilization, and thus reducing operating costs. It can also reduce the nitrogen oxide content in the flue gas to 60 mg / m³.3 Within the specified range, the required emission standards must be met. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Figure 2 This is an enlarged view of the urea injection unit. Detailed Implementation

[0019] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0020] It should be noted that, in the description of this invention, relational terms such as “first” and “second” are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] like Figure 1-2As shown, the glass furnace flue gas denitrification system of the present invention includes a urea injection unit, a flue gas exhaust unit connected to the flue gas outlet of the glass furnace F, and a control unit. The flue gas exhaust unit includes a first flue 1 and a second flue 2 connected to the flue gas outlet. The first flue 1 is vertically arranged, and the second flue 2 is horizontally arranged and connected to the upper part or top of the first flue 1. A catalyst module 3 is arranged inside the second flue 2. The catalyst filled in the catalyst module 3 is a commonly used SCR catalyst, such as a catalyst with anatase TiO2 as the carrier and V2O5 as the active ingredient. The filling form of the catalyst module 3 is preferably honeycomb filling, that is, the catalyst module adopts a honeycomb catalyst module 3. When the cross-section of the second flue 2 is square, the catalyst module 3 is correspondingly square, such as a common standard module of 150 mm × 150 mm. When the cross-section of the second flue 2 is circular, the catalyst module 3 is correspondingly circular. In actual installation, the catalyst module 3 is preferably installed in the second flue 2 near the first flue 1. The number of catalyst modules 3 can be flexibly determined according to the size of the second flue 2 and the SCR reaction requirements, such as one per layer, one layer, two layers or three layers. The urea injection unit includes a urea container 4a, a urea pump 4b, and a urea spray gun 4c connected in sequence via urea pipelines. The spray gun 4c is vertically positioned inside the first flue 1, and its length is preferably 1m or more. The spray gun 4c is preferably inserted vertically upwards into the first flue 1 from the bottom (bottom sealed). The urea pump 4b provides a certain pressure to the urea spray gun 4c, causing the urea solution to atomize in the first flue 1 for better decomposition or hydrolysis into ammonia, which then reacts better with nitrogen oxides, improving the SNCR conversion rate. The urea injection unit also includes a first regulating valve 4d, which is located on the pipeline between the urea spray gun 4c and the urea pump 4b, preferably installed at the urea inlet of the urea spray gun 4c.

[0023] In actual installation, the urea spray gun 4c can be a mechanical atomizing spray gun or a pneumatic atomizing spray gun (such as a pneumatic internal mixing spray gun or a pneumatic external mixing spray gun). In this invention, the urea spray gun 4c is preferably a pneumatic atomizing spray gun, which is equipped with a second regulating valve 4e at its compressed air inlet. The compressed air inlet of the pneumatic internal mixing spray gun is connected to an air compressor or a compressed air source through an air pipe. The compressed air source can be a high-pressure compressed air cylinder to provide compressed air to the urea spray gun 4c. The high-speed air and urea solution undergo violent turbulent collisions, finally forming fine droplets with a size of 50-100 micrometers, which promotes the decomposition or hydrolysis of the urea solution to obtain ammonia, and further promotes the reaction between ammonia and nitrogen oxides in the flue gas, ensuring the denitrification effect.

[0024] Combination Figure 1-2It is understood that the control unit includes a controller, a first sensor 6 for detecting the temperature of the flue gas upstream of the second flue duct 2, and a second sensor 7 (i.e., a nitrogen oxide concentration sensor) for detecting the concentration of nitrogen oxides in the second flue duct 2. The signal output terminals of the first sensor 6 and the second sensor 7 are connected to the signal input terminals of the controller, and the control output terminal of the controller is connected to the control input terminals of the first regulating valve 4d, the urea pump 4b, and the second regulating valve 4e. The first regulating valve 4d, the second regulating valve 4e, and the second sensor 7 are linked for control. The second sensor 7 is used to detect the concentration of nitrogen oxides in the flue gas upstream of the catalyst module 3 in the second flue duct 2. Based on the detected real-time concentration feedback, the flow rates of urea solution and compressed air are dynamically adjusted. This not only avoids excessive urea and reduces ammonia escape but also avoids insufficient urea, ensuring the denitrification rate of the flue gas.

[0025] It should be noted that the controller in this invention can be a PLC, a PID controller, or an industrial control computer with computer attributes and characteristics. Furthermore, the controller also includes a wireless communication module to connect with a remote terminal, receive control commands from the remote terminal, and provide real-time operating status feedback.

[0026] This invention alters the traditional flue structure of glass furnaces by vertically positioning the first flue 1, which connects to the glass furnace F. This design slows the flow velocity, reducing its impact on downstream catalysts, and promotes the non-linear catalytic reduction (SNCR) reaction between nitrogen oxides and urea in the flue gas, thus improving denitrification efficiency. This invention combines SNCR and SCR technologies, requiring only urea injection into the first flue 1. The urea is converted into ammonia, which reacts with nitrogen oxides. The remaining ammonia can continue the SCR reaction in the second flue 2, eliminating the need for additional ammonia replenishment and reducing ammonia slip (which can be controlled below 5%). This improves urea utilization, reduces reducing agent usage, and lowers operating costs. Furthermore, this invention can reduce the nitrogen oxide content in the flue gas to 100 mg / m³. 3 (It can even be reduced to 60 mg / m²) 3 Within a certain range, the required emission standards are met. Furthermore, in this invention, the catalyst module 3 is directly installed in the second flue duct 2 for SCR reaction, eliminating the need for a reactor; compared with an independent SCR flue gas treatment system, the amount of catalyst used in this invention is only 1 / 5 of that in the SCR flue gas treatment system, significantly reducing the amount of catalyst used and thus reducing the operating cost of flue gas denitrification.

[0027] In a preferred embodiment of the present invention, the temperature inside the glass furnace F is typically around 1600°C, and the temperature of the flue gas produced is often quite high. To maintain the temperature of the reaction zone at the bottom of the first flue duct 1 at 950°C-1100°C, a cooling coil 5a is installed at the lower part of the outside of the first flue duct 1. The cooling medium in the cooling coil 5a can be room temperature soft water. When the temperature of the flue gas exiting the glass furnace F is too high, room temperature soft water is used to absorb part of the heat from the flue gas, thereby controlling the temperature of the flue gas in the first flue duct 1 within a reasonable range and ensuring the SNCR reaction temperature. In addition, the cooling coil 5a can be connected to a heat exchanger 5b to form a recovery circulation loop, and the heat exchanger 5b can be connected to a hot water storage tank 5c to form an energy storage circulation loop, thereby recovering part of the waste heat from the flue gas absorbed by the room temperature soft water and storing it in the form of hot water, thus saving energy and reducing emissions. To ensure the independent operation of the recycling loop and the energy storage loop, each loop is equipped with a water pump and a control valve. The controller controls each loop individually by controlling the water pump and the control valve. When the flue gas temperature in the first flue duct 1 is too high, the water pump and control valve on both loops are started simultaneously to cool down the flue gas inside the first flue duct 1.

[0028] In a preferred embodiment of the present invention, in order to ensure accurate control of the temperature at the lower part of the first flue 1, a third sensor for detecting the flue gas temperature is installed on the lower inner side of the first flue 1. The signal output terminal of the third sensor is connected to the signal input terminal of the controller. The third sensor provides real-time feedback on the flue gas temperature in the first flue 1. When the flue gas temperature exceeds the set upper limit, the first flue 1 is cooled by cooling coil 5a and soft water until it is cooled to the preset range.

[0029] In a preferred embodiment of the present invention, since the temperature inside the first flue 1 is relatively high, the third sensor is preferably a high-temperature resistant thermocouple, such as a K-type, S-type, or B-type thermocouple, to meet the temperature measurement requirements of the high-temperature flue gas inside the first flue 1. Alternatively, the third sensor can be a distributed optical fiber, pre-embedded in the side wall of the first flue 1. The temperature of the flue gas inside the first flue 1 is obtained using the distributed optical fiber, and the temperature is dynamically fed back. Combined with the cooling coil 5a, precise control of the flue gas temperature inside the first flue 1 can be achieved.

[0030] In a preferred embodiment of the present invention, the first sensor 6 is preferably a thermocouple, such as a K-type, S-type or B-type thermocouple, to meet the temperature measurement requirements of the flue gas on the upstream side of the catalyst module 3 in the second flue 2. In addition, the flue gas denitration system of the glass furnace of the present invention further includes an auxiliary heating device 8 (such as an electric heater) provided on the upstream side of the catalyst module 3. The first sensor 6 dynamically monitors the temperature of the flue gas upstream of the catalyst module 3. When the temperature of the flue gas here is lower than a certain temperature, the auxiliary heating device 8 is started to assist in heating the passing flue gas, and the temperature of the flue gas at the catalyst module 3 is controlled at 350°C to 430°C, promoting the conversion of nitrogen oxides and reducing ammonia escape. It should be noted that, in actual installation, the first sensor 6 is located at the upstream end of the auxiliary heating device 8, and the first sensor 6 and the auxiliary heating device 8 are linked for control.

[0031] During operation, a blower is connected to the end of the second flue 2. The blower provides a certain wind pressure for the flue gas, so that the high-temperature flue gas in the glass furnace F sequentially passes through the first flue 1 and the second flue 2 and then enters the subsequent desulfurization process.

[0032] The present invention also proposes a method for reducing the concentration of nitrogen oxides in the flue gas of a glass furnace. This method uses the above-mentioned flue gas denitration system of the glass furnace and includes the following content: During the operation of the glass furnace F, the flue gas denitration system supporting the glass furnace F operates synchronously. The controller controls the urea pump 4b, the first regulating valve 4d and the second regulating valve 4e to start, and sprays the urea solution at the lower part of the first flue 1. The urea solution undergoes violent turbulent collision under the action of high-speed air flow, and finally forms fine droplets with a size within 100 microns, so that the urea decomposes or hydrolyzes at 950°C - 1100°C to generate ammonia, and the ammonia reacts with the nitrogen oxides in the flue gas to convert the nitrogen oxides into N2; In the above process, the controller obtains the temperature signal monitored by the third sensor and converts it into a temperature value. When the temperature of the flue gas at the lower part of the first flue 1 is higher than 1100°C, normal temperature soft water is used to cool the lower part of the first flue 1. By cooling the first flue 1, the temperature of its flue gas is reduced, and then the temperature of the flue gas at the lower part of the first flue 1 is controlled within 1100°C to avoid excessive temperature leading to ammonia escape and protecting the urea spray gun 4c; When the flue gas flows to the upper part of the first flue 1, the first sensor transmits the monitored temperature signal to the controller. The controller obtains the temperature of the flue gas at the upper part of the first flue 1. When the temperature of the flue gas at this position is lower than 350°C, the auxiliary heating device is started to assist in heating the flue gas to ensure the flue gas temperature; When the flue gas flows to the catalyst module 3, the nitrogen oxides and ammonia undergo a reduction reaction under the action of the catalyst, realizing a secondary denitration reaction, and then controlling the nitrogen oxides in the flue gas within the emission requirements.

[0033] In the above-mentioned denitrification process, the flow rate of urea solution is preferably controlled at 1.0-5.0 L / h, the concentration of urea solution is 10%-30%, and the flue gas velocity is 4-8 m / s. During this process, since the first flue duct 1 is vertically arranged and the flue gas velocity is relatively low, dust can settle, thereby reducing the impact on the catalyst in the catalyst module 3, extending the service life of the catalyst module 3, and reducing the catalyst replacement cost.

[0034] Experiments have shown that this invention, through the combined use of SNCR and SCR technologies, significantly reduces the concentration of nitrogen oxides in flue gas, decreases ammonia escape, and improves ammonia utilization, controlling the ammonia escape rate to below 5%. Taking high-nitrogen-oxide-concentration flue gas from a glass furnace exhaust outlet as an example, the initial concentration of nitrogen oxides in the exhaust gas from the glass furnace was 440 mg / m³. 3 Using the technical solution of this invention, after SNCR reaction in the first flue 1, the concentration of nitrogen oxides can be reduced from 440 mg / m³. 3 Reduced to 180 mg / m 3 Without additional ammonia or increased urea dosage, the concentration of nitrogen oxides in the flue gas can be reduced from 180 mg / m³ after passing through catalyst module 3. 3 Reduced to 60 mg / m 3 Within the required emission standards.

[0035] Finally, it should be emphasized that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A glass furnace flue gas denitrification system, comprising a urea injection unit and a flue gas exhaust unit connected to the flue gas outlet of the glass furnace, characterized in that: It also includes a control unit; the exhaust unit includes a first flue and a second flue connected to the exhaust port, the first flue is vertically arranged, the second flue is horizontally arranged and connected to the upper part or top of the first flue, and a catalyst module is provided in the second flue; The urea injection unit includes a urea container, a urea pump, and a urea spray gun connected in sequence by pipelines. The spray gun body is vertically arranged in the first flue. The urea injection unit also includes a first regulating valve, which is arranged between the urea spray gun and the urea pump. The control unit includes a controller, a first sensor for detecting the temperature of flue gas upstream of the second flue, and a second sensor for detecting the concentration of nitrogen oxides in the second flue. The signal output terminals of the first and second sensors are connected to the signal input terminals of the controller, and the control output terminal of the controller is connected to the control input terminals of the first regulating valve and the urea pump.

2. The glass furnace flue gas denitrification system according to claim 1, characterized in that: The urea spray gun is a pneumatic atomizing spray gun, and a second regulating valve is provided at its compressed air inlet. The control input terminal of the second regulating valve is connected to the control output terminal of the controller.

3. The glass furnace flue gas denitrification system according to claim 1 or 2, characterized in that: The nozzle of the urea spray gun extends vertically into the first flue by 1 meter or more.

4. The glass furnace flue gas denitrification system according to claim 1, characterized in that: A cooling coil is also provided on the lower part of the outer wall of the first flue; a third sensor for detecting flue gas temperature is provided on the lower inner side of the first flue, and the signal output terminal of the third sensor is connected to the signal input terminal of the controller.

5. The glass furnace flue gas denitrification system according to claim 4, characterized in that: The first and third sensors are thermocouples, and the second sensor is a through-hole sensor.

6. The glass furnace flue gas denitrification system according to claim 1, characterized in that: It also includes an auxiliary heating device located upstream of the catalyst module.

7. A method for reducing the concentration of nitrogen oxides in flue gas from a glass furnace, characterized in that: The method employs the glass furnace flue gas denitrification system according to any one of claims 1-6, comprising the following: spraying urea solution into the lower part of the first flue to form a urea spray, and conducting an SNCR reaction in the lower part of the first flue at a reaction temperature of 950℃-1100℃; when the flue gas in the first flue flows into the second flue, an SCR reaction occurs at the catalyst module, and the flue gas temperature at the catalyst module is controlled at 350℃-430℃.

8. The method for reducing the concentration of nitrogen oxides in glass furnace flue gas according to claim 7, characterized in that: The flow rate of the urea solution is 1.0-5.0 L / h, and the concentration of the urea solution is 10%-30%.

9. The method for reducing the concentration of nitrogen oxides in glass furnace flue gas according to claim 7, characterized in that: The flue gas velocity in the exhaust unit is 4-8 m / s.

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