Galvanized wire annealing furnace flue gas denitration device

Abstract

The invention relates to a flue gas denitration device for a galvanized wire annealing furnace. The flue gas denitration device comprises an SCR (Selective Catalytic Reduction) catalytic reactor, a reducing agent storage system, a reducing agent injection system, a compressed air system, a flue gas monitoring system and an automatic control system, by adopting the in-situ online NOx sensor and the flow velocity type flow meter, the content and the flow of the nitric oxide in the flue gas can be accurately monitored in real time. The digital metering pump is used for accurately controlling the spraying amount of the reducing agent, the reducing agent mixed with the compressed air is atomized and sprayed into the flue gas through the sprayer, and the denitration reaction is effectively promoted. And the automatic control system automatically adjusts injection parameters according to flue gas monitoring data, so that the denitration efficiency is maximized, the consumption of a reducing agent is reduced, and the operation cost is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of flue gas denitrification, and in particular relates to a flue gas denitrification device for an annealing furnace of a galvanizing line. Background Art

[0002] At present, with the improvement of human ecological awareness and the increasingly stringent environmental protection regulations, the nitrogen oxide (NOx) content in the flue gas emitted by the annealing furnace of the galvanizing line of industrial equipment has become an important environmental protection indicator of human concern.

[0003] At present, the annealing process is the key process of the hot-dip galvanizing production line, and the annealing process directly determines the performance and quality of the galvanized sheet produced by the galvanizing production line. The maximum temperature in the annealing furnace of the galvanizing line can reach 900℃. The fuel generally uses natural gas or mixed coal gas, which is reasonably mixed with air and burned in the radiant tube burner and then discharged through the flue gas pipe.

[0004] The basic principle of the selective catalytic reduction (SCR) denitrification method is to introduce a reducing agent (usually urea solution, ammonia water or liquid ammonia) into the flue gas, and then reduce the NOx in the flue gas to harmless nitrogen (N2) and water vapor (H2O) under the action of a catalyst. SCR denitrification technology has been widely used in the field of power boilers due to its good effect, no "three wastes" emissions, stable and reliable operation, etc. However, this SCR denitrification technology is still in the initial stage of treatment in the field of flue gas treatment of annealing furnaces in galvanizing lines.

[0005] Compared with power plant boilers, the operation of the galvanizing line annealing furnace requires precise control of the annealing temperature and furnace atmosphere according to the different thicknesses and types of steel plates. Therefore, the flue gas flow and temperature fluctuate greatly during operation. When the SCR denitrification device widely used in power plants is directly applied to the denitrification of the galvanizing line annealing furnace, there are often phenomena such as nitrogen oxide detection signal lag, inaccurate flue gas flow detection, excessive fluctuations in the injection volume, and serious ammonia escape during operation, resulting in reduced denitrification efficiency and increased operating costs.

[0006] The control of nitrogen oxides (NOx) in the flue gas emitted by the annealing furnace of the galvanizing line has become particularly important. The application of selective catalytic reduction (SCR) technology in the annealing furnace of the galvanizing line faces problems such as large fluctuations in flue gas flow and temperature, delayed detection of nitrogen oxides, and inaccurate control of the injection amount of reducing agent, resulting in low denitrification efficiency and increased operating costs. Summary of the invention

[0007] The purpose of this application is to provide a flue gas denitrification device for a galvanizing line annealing furnace, which solves the problems in the prior art by improving the nitrogen oxide detection method, the flue gas flow detection method and introducing a digital metering pump, thereby improving the denitrification efficiency and reducing the operating cost.

[0008] One of the improvements is to use in-situ online detection technology instead of traditional sampling methods to achieve real-time monitoring of nitrogen oxides, avoid data lags, and improve detection sensitivity.

[0009] The second improvement is that by using a velocity type flow meter instead of a resistance type flow meter, the response speed and accuracy of the flue gas flow detection are improved, ensuring that the reducing agent injection amount is accurately adjusted according to the real-time flue gas flow.

[0010] The third improvement is to introduce a digital metering pump to replace the traditional mechanical flow pump to achieve precise control of the reducing agent flow. Its flow adjustment ratio can reach 1:1000, which effectively reduces the reducing agent consumption and reduces operating costs.

[0011] Next, the technical improvements of this application are described in more detail:

[0012] (1) The core of the present application is to adopt in-situ online detection technology, by installing NOx sensors (corresponding to the pre-denitrification NOx sensor 5 and the post-denitrification NOx sensor 6 in some embodiments) in the flue gas emission pipeline, to achieve real-time monitoring of nitrogen oxides in the flue gas. This detection method avoids the hysteresis of the traditional sampling method and improves the real-time and accuracy of the detection.

[0013] (2) In terms of flue gas flow detection, the present application adopts a velocity flow meter (corresponding to the flue gas flow sensor 7 in some embodiments) instead of a traditional resistance flow meter. The velocity flow meter has a faster response speed and higher measurement accuracy, and can accurately monitor the flue gas flow in real time, providing accurate data support for the reductant injection system.

[0014] (3) The present application also introduces a digital metering pump (corresponding to the flow pump 8 in some embodiments) as the core component of the reducing agent injection system, which is used to control the flow of the reducing agent (urea solution, ammonia water or liquid ammonia). The introduction of the digital metering pump enables the adjustment ratio of the reducing agent flow to reach 1:1000, greatly improving the adjustment accuracy of the reducing agent flow, thereby reducing the consumption of the reducing agent and reducing the operating cost of the denitration device.

[0015] (4) The design of the reductant injection system (corresponding to the reductant injection system 3 in some embodiments) is also an important feature of the present application. The system consists of a digital metering pump (corresponding to the flow pump 8 in some embodiments), an injector (corresponding to the injector 9 in some embodiments) and its accessories. The injector is located upstream of the SCR catalytic reactor (corresponding to the SCR catalytic reactor 1 in some embodiments) and is responsible for mixing the reductant delivered by the digital metering pump with compressed air and atomizing it and then spraying it evenly into the flue gas. This design ensures the full mixing of the reductant and the flue gas, thereby improving the denitrification efficiency.

[0016] (5) A compressed air system (corresponding to the compressed air system 4 in some embodiments) provides power for the reducing agent injection system. The system consists of a compressed air storage tank, a compressed air pipeline and its accessories, and provides 0.4-0.6Mpa compressed air. The compressed air is not only used to atomize the reducing agent, but also helps to increase the contact area between the reducing agent and the flue gas, thereby improving the efficiency of the denitration reaction.

[0017] Next, the technical solution of this application is described in detail.

[0018] The present application provides a flue gas denitrification device for an annealing furnace of a galvanizing line, characterized in that it comprises an SCR catalytic reactor (1), a reducing agent storage system (2), a reducing agent injection system (3), a compressed air system (4), and a flue gas monitoring system and an automatic control system composed of sensors.

[0019] In certain embodiments, the flue gas monitoring system comprises a NOx sensor before denitrification (5), a NOx sensor after denitrification (6) and a flue gas flow sensor (7), wherein the NOx sensors before and after denitrification use an in-situ online detection method for nitrogen oxides.

[0020] In certain embodiments, it is characterized in that the reducing agent injection system (3) comprises a digital metering pump (8), an injector (9) and its accessories, wherein the digital metering pump is used to control the flow rate of the reducing agent. The accessories of the injector refer to components that can work together with the injector to ensure that the reducing agent is injected into the reactor in an appropriate manner and dosage, and common ones include but are not limited to: nozzles, pipes and joints, valves, filters, pressure gauges and flow meters, brackets and fixtures, etc.

[0021] In certain embodiments, the flow rate adjustment ratio of the digital metering pump is 1:1000.

[0022] In certain embodiments, the compressed air system (4) is used to provide compressed air with a pressure of 0.4-0.6 MPa to facilitate atomization and injection of the reducing agent.

[0023] In some embodiments, the flue gas flow sensor (7) adopts a velocity type flow meter to monitor the flue gas flow in real time and accurately, providing data support for the adjustment of the reducing agent injection amount.

[0024] In certain embodiments, the reductant storage system (2) is equipped with a container for storing urea solution, ammonia water or liquid ammonia and its accessories for supplying the reductant injection system.

[0025] The accessories of the container for aqueous ammonia or liquid ammonia refer to the accessories that can ensure the safe storage, stable supply and safety of aqueous ammonia or liquid ammonia during use. Common accessories include but are not limited to: safety valves, pressure gauges, liquid level gauges, thermometers, leak detectors, feed pumps or delivery pumps, pipes and valves, etc.

[0026] In certain embodiments, the automatic control system can automatically adjust the operating parameters of the digital metering pump and the injection frequency and amount of the injector according to the real-time data provided by the flue gas monitoring system to achieve the optimal denitrification effect.

[0027] In certain embodiments, the SCR catalytic reactor (1) is equipped with a high-efficiency catalyst module for catalyzing the reaction between the reducing agent and NOx in the flue gas to generate harmless nitrogen and water vapor.

[0028] The present application also provides a method for using a galvanizing line annealing furnace flue gas denitrification device, which is characterized by comprising the following steps:

[0029] a) Use an in-situ online NOx sensor to monitor the nitrogen oxide content in the flue gas in real time;

[0030] b) Real-time monitoring of flue gas flow rate through a velocity flow meter;

[0031] c) According to the monitored nitrogen oxide content and flue gas flow data, the automatic control system adjusts the operating parameters of the digital metering pump to accurately control the injection amount of the reducing agent;

[0032] d) Mixing the reducing agent with compressed air and spraying it into the flue gas through an injector;

[0033] e) In the SCR catalytic reactor, the atomized reducing agent reacts with the NOx in the flue gas to generate harmless nitrogen (N2) and water vapor (H2O), thereby achieving the purpose of denitrification.

[0034] It is hereby declared that the existing mature technologies can be adopted for the parts outside the present invention, such as denitrification catalysts, pipeline valves, etc., which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : Schematic diagram of the structure of the flue gas denitrification device of the annealing furnace of the galvanizing line. DETAILED DESCRIPTION

[0036] Attached Figure 1 Shown is a schematic diagram of a novel galvanizing line annealing furnace flue gas denitrification device according to the present invention.

[0037] The denitration device mainly includes an SCR catalytic reactor (1), a reducing agent storage system (2), a reducing agent injection system (3), a compressed air system (4), a flue gas monitoring system composed of sensors, and an automatic control system. The SCR catalytic reactor contains a denitration catalyst module (1); the reducing agent storage system consists of a urea solution tank and its accessories (2); the reducing agent injection system consists of a flow pump (8), an injector (9), a reducing agent pipeline and its accessories (3); the compressed air system consists of a compressed air storage tank and a compressed air pipeline and its accessories (4); the flue gas monitoring system consists of a NOx sensor before denitration (5), a NOx sensor after denitration (6), a flue gas flow sensor (7), etc., and the monitoring data is transmitted to the automatic control system.

[0038] Example 1: This example uses urea solution as a reducing agent, monitors the nitrogen oxide content in the flue gas through an in-situ online NOx sensor, monitors the flue gas flow rate in real time through a velocity flow meter, and accurately controls the injection amount of the urea solution through a digital metering pump. The urea solution is atomized by an injector under the action of compressed air and then sprayed into the flue gas, reacts with NOx in the SCR catalytic reactor, and is effectively converted into nitrogen and water vapor, thereby achieving the purpose of denitrification.

[0039] Example 2: Based on Example 1, this example uses ammonia water as a reducing agent. The storage and injection system of ammonia water is the same as that of urea solution, but considering the physical properties of ammonia water, the design of the injector is adjusted accordingly to ensure that ammonia water can be effectively atomized and fully mixed with the flue gas. Similarly, through the monitoring of the in-situ online NOx sensor and the flow rate flow meter, the digital metering pump accurately controls the injection amount of ammonia water to achieve efficient denitrification.

[0040] Example 3: This example uses liquid ammonia as a reducing agent. Since the storage and use conditions of liquid ammonia are different from those of urea solution and ammonia water, the reducing agent storage system and injection system are specially designed. Liquid ammonia is transported to the injection system through a dedicated safety pipeline. Also under the precise control of a digital metering pump, it is mixed with compressed air and sprayed into the flue gas through an injector. The monitoring of the in-situ online NOx sensor and the velocity flow meter ensures the high efficiency and safety of the denitrification process.

[0041] Embodiment 4: Based on the previous three embodiments, this embodiment further optimizes the automatic control system. The system can receive data from the NOx sensor and flue gas flow sensor before and after denitration in real time, and automatically adjust the operating parameters of the digital metering pump, as well as the injection frequency and injection amount of the injector through advanced algorithms to ensure that the optimal denitration effect can be achieved even when the flue gas flow and NOx concentration fluctuate. In addition, the automatic control system also has fault diagnosis and alarm functions, which can promptly detect abnormal conditions in the system operation and prompt the operator to handle them through the control interface, thereby improving the stability and safety of the system.

[0042] Beneficial Effects

[0043] (1) Effectively improve denitrification efficiency: By adopting in-situ online detection technology and a velocity flow meter, the present application can accurately monitor the NOx content and flow in the flue gas in real time, and combine with a digital metering pump to accurately control the amount of reducing agent injection, ensuring the full progress of the denitrification reaction, thereby significantly improving the denitrification efficiency.

[0044] (2) Significantly reduce operating costs: The introduction of digital metering pumps allows the injection amount of reducing agent to be precisely controlled, avoiding excessive use of reducing agent, thereby reducing material consumption and reducing operating costs. At the same time, improving denitrification efficiency also means reducing environmental fines that may be incurred due to failure to meet denitrification standards.

[0045] (3) Maintaining environmental friendliness: This application reduces ammonia escape and avoids secondary pollution to the environment by optimizing the denitration process. At the same time, the efficient denitration process reduces the emission of nitrogen oxides, helps improve air quality, and has positive significance for environmental protection. In addition, by precisely controlling the use of reducing agents, the consumption of chemical substances is reduced, further reducing the impact on the environment.

[0046] (4) Wide applicability: This application has broad application prospects and important practical value in the field of industrial flue gas treatment.

[0047] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

[0048] It should be noted that, in this article, relational terms such as first and second, etc. are only used 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. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A galvanizing line annealing furnace flue gas denitrification device, characterized in that: The invention comprises a flue gas monitoring system and an automatic control system composed of an SCR catalytic reactor (1), a reducing agent storage system (2), a reducing agent injection system (3), a compressed air system (4) and sensors.

2. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The flue gas monitoring system comprises a NOx sensor before denitration (5), a NOx sensor after denitration (6) and a flue gas flow sensor (7), wherein the NOx sensors before and after denitration use an in-situ online detection method for nitrogen oxides.

3. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The reducing agent injection system (3) comprises a digital metering pump (8), an injector (9) and its accessory parts, wherein the digital metering pump is used to control the flow rate of the reducing agent.

4. The galvanizing line annealing furnace flue gas denitrification device according to claim 3, characterized in that: The flow rate adjustment ratio of the digital metering pump is 1:1000.

5. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The compressed air system (4) is used to provide compressed air with a pressure of 0.4-0.6Mpa.

6. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The flue gas flow sensor (7) is a velocity type flow meter.

7. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The reducing agent storage system (2) is equipped with a container for storing urea solution, ammonia water or liquid ammonia and its auxiliary accessories.

8. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The automatic control system can automatically adjust the operating parameters of the digital metering pump and the injection frequency and amount of the injector according to the real-time data provided by the smoke monitoring system.

9. The galvanizing line annealing furnace flue gas denitrification device according to claim 1, characterized in that: The SCR catalytic reactor (1) is equipped with a high-efficiency catalyst module.

10. A method for using a galvanizing line annealing furnace flue gas denitrification device, characterized in that The following steps are involved: a) Use an in-situ online NOx sensor to monitor the nitrogen oxide content in the flue gas in real time; b) Real-time monitoring of flue gas flow rate through a velocity flow meter; c) According to the monitored nitrogen oxide content and flue gas flow data, the automatic control system adjusts the operating parameters of the digital metering pump to accurately control the injection amount of the reducing agent; d) Mixing the reducing agent with compressed air and spraying it into the flue gas through an injector; e) In the SCR catalytic reactor, the atomized reducing agent reacts with the NOx in the flue gas to generate harmless nitrogen (N2) and water vapor (H2O), thereby achieving the purpose of denitrification.

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