Catalytic purification system for tail gas CO of steel sintering machine

Abstract

The utility model relates to a steel sintering machine tail gas CO catalytic purification system which comprises an exhaust pipeline, and a front-stage purification unit and a rear-stage catalysis unit are sequentially installed in the exhaust pipeline. The front-stage purification unit is of a wall flow type honeycomb ceramic structure and comprises a front-stage ceramic shell. According to the CO catalytic purification system for the tail gas of the steel sintering machine disclosed by the utility model, impurities such as ash, carbon black, SO2 and halogen in the tail gas of the sintering machine are effectively intercepted by arranging the pre-stage purification unit with a wall-flow honeycomb ceramic structure, so that the tail gas is purified to a certain extent; the poisoning influence of the impurities on a CO catalytic oxidation active coating in a rear-stage catalytic unit is avoided, and the long-term efficient catalytic oxidation activity of the catalytic unit on CO is guaranteed. Meanwhile, the utility model further designs an in-situ regeneration control system of the preceding-stage purification unit, so that the exhaust back pressure increase of the preceding-stage purification unit is effectively controlled, and the long-term stable operation of the whole catalytic purification system is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of waste gas purification and relates to a CO catalytic purification system for the tail gas of an iron and steel sintering machine. Background Art

[0002] Pollutants generated by the iron and steel industry mainly include NO x , SO 2 , particulate matter, CO, halogen compounds, etc. For particulate matter, NO x , SO 2 , the country already has strict emission limit standards. However, the emission of CO is difficult to control. CO emission sources include sintering machine tail gas, steelmaking primary tail gas, coke oven tail gas for coking, and dry quenching coke waste gas. Among them, the CO emission in the sintering machine tail gas is the most serious. The sintering machine tail gas has a large discharge volume and a relatively low tail gas temperature, generally not exceeding 250 °C. The CO volume fraction is between 0.5% and 2%. It is suitable for removal by catalytic oxidation method. The heat released during the removal process can heat the tail gas and be used for the subsequent SCR denitrification process.

[0003] The composition of the sintering machine tail gas is relatively complex. Although there are previous dust removal and desulfurization treatment processes, there are still certain amounts of SO 2 , ash, carbon black, halogen and other impurity substances in the tail gas. The continuous action of the above impurity substances on the catalytic system will significantly affect the catalytic activity of the CO oxidation catalyst in the system, manifested as a rapid decline in the CO conversion rate in a very short time, and then unable to meet the CO emission target requirements. Therefore, at present, it is urgent to improve the design of the catalytic purification system. Summary of the Invention

[0004] The purpose of the utility model is to provide a CO catalytic purification system for the tail gas of an iron and steel sintering machine, which can solve the above problems and ensure the long-term stable operation of the whole catalytic purification system.

[0005] According to the technical scheme provided by the utility model: a CO catalytic purification system for the tail gas of an iron and steel sintering machine includes an exhaust pipe, and a pre-stage purification unit and a post-stage catalytic unit are sequentially installed in the exhaust pipe; the pre-stage purification unit is of a wall-flow honeycomb ceramic structure, including a pre-stage ceramic shell, and pre-stage flow holes are arrayed in the pre-stage ceramic shell. A plug is installed at the front end or the rear end of the pre-stage flow hole, and the plugs in adjacent pre-stage flow holes are located at different ends; the post-stage catalytic unit is of a straight-through honeycomb ceramic structure, including a post-stage ceramic shell, and post-stage flow holes are arrayed in the post-stage ceramic shell, and a CO catalytic oxidation active coating is coated in the post-stage flow holes.

[0006] As a further improvement of the utility model, a CO catalytic oxidation active coating is coated in the pre-stage flow holes of the pre-stage purification unit.

[0007] As a further improvement of the present utility model, the air porosity of the pre-stage flow holes in the pre-stage purification unit structure is 50 - 60%, and the median pore diameter is 12 - 20 μm.

[0008] As a further improvement of the present utility model, a heating wire mesh is arranged between the pre-stage purification unit and the post-stage catalytic unit, and a blower is also arranged in the exhaust duct behind the post-stage catalytic unit.

[0009] As a further improvement of the present utility model, the heating wire mesh can be heated to above 200°C.

[0010] As a further improvement of the present utility model, differential pressure sensors are installed at the inlet and outlet ends of the pre-stage purification unit.

[0011] The positive and progressive effects of this application are as follows:

[0012] For the tail gas CO catalytic purification system of the iron and steel sintering machine of the present utility model, by setting a pre-stage purification unit with a wall-flow honeycomb ceramic structure, ash, carbon black, SO 2 impurities such as and halogens are effectively intercepted, the tail gas is purified to a certain extent, and the poisoning effect of the above impurities on the CO catalytic oxidation active coating in the post-stage catalytic unit is avoided, ensuring the long-term and efficient catalytic oxidation activity of the catalytic unit for CO. At the same time, the present utility model also designs an in-situ regeneration control system for the pre-stage purification unit, effectively controlling the increase in the exhaust back pressure of the pre-stage purification unit, and ensuring the long-term stable operation of the entire catalytic purification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of the present utility model.

[0014] Figure 2 It is a partial side view screenshot of the pre-stage purification unit of the present utility model.

[0015] Figure 3 It is a partial front view screenshot of the pre-stage purification unit of the present utility model.

[0016] Figure 4 It is a partial side view screenshot of the post-stage catalytic unit of the present utility model.

[0017] Figure 5 It is a partial front view screenshot of the post-stage catalytic unit of the present utility model.

[0018] Figure 6 It is a schematic structural diagram of the present utility model with a regeneration device installed. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other. The present utility model will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0020] In order to enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present utility model.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present utility model and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to implement the embodiments of the present utility model described herein. In addition, similar terms such as "including" and "having" mean that in addition to the content already listed in "including" and "having", other content not yet listed can also be "included" and "had"; for example, a process, method, system, product or device that can include a series of steps or units does not necessarily have to be limited to those steps or units that have been clearly listed, but can include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0022] Due to the problem of the drawing angle, some components may not be drawn, but their positions and connection relationships can be understood according to the text description part.

[0023] As Figure 1 shown, the present utility model is a CO catalytic purification system for the tail gas of an iron and steel sintering machine, which includes an exhaust pipe 3, and a pre-stage purification unit 1 and a post-stage catalytic unit 2 are sequentially installed in the exhaust pipe 3. The pre-stage purification unit 1 is of a wall-flow honeycomb ceramic structure, including a pre-stage ceramic housing 11. Pre-stage flow holes are arrayed in the pre-stage ceramic housing 11, and a plug 12 is installed at the front end or the rear end of the pre-stage flow holes. The plugs 12 in adjacent pre-stage flow holes are located at different ends. Due to the function of the plug 12, when the air flow enters the pre-stage purification unit 1, it will pass through the pre-stage flow holes and flow out from the adjacent channels. The ash and carbon black in the air flow are intercepted by the pre-stage flow holes, and at the same time, impurities such as SO 2 and halogens will also be partially adsorbed on the ash and carbon black along with them, so that the impurities in the tail gas are purified, and the influence on the activity of the catalyst in the post-stage catalytic unit 2 is greatly reduced.

[0024] To improve the CO oxidation efficiency and the regeneration process efficiency of the catalytic purification system, it is preferred to coat a CO catalytic oxidation active coating in the front-stage flow holes of the front-stage purification unit 1. This coating can cooperate with the rear-stage catalytic unit 2 to remove CO, and at the same time can catalytically accelerate the combustion process of carbon black during the regeneration process of the front-stage purification unit 1, shortening the regeneration process time.

[0025] The rear-stage catalytic unit 2 is a straight-through honeycomb ceramic structure, including a rear-stage ceramic housing 21. The rear-stage ceramic housing 21 is arrayed with rear-stage flow holes, and a CO catalytic oxidation active coating is coated in the rear-stage flow holes.

[0026] To ensure the interception efficiency of the front-stage purification unit 1 for solid impurities such as carbon black and ash, it is preferred that the porosity of the front-stage flow holes in the structure of the front-stage purification unit 1 is 50-60%, and the median pore diameter is 12-20 μm.

[0027] The first embodiment of this system:

[0028] The porosity of the front-stage flow holes in the structure of the front-stage purification unit 1 is 50%, and the median pore diameter is 20 μm.

[0029] The second embodiment of this system:

[0030] After the above catalytic purification system operates for a period of time, since the front-stage purification unit 1 has captured a certain mass of impurity substances, the accumulated impurity substances will increase the exhaust back pressure of the purification system, which is not conducive to the passage of air flow. Therefore, it is necessary to perform regeneration regularly. The regeneration methods include replacement regeneration and in-situ regeneration.

[0031] Replacement regeneration is to replace the used front-stage purification unit 1 with a fresh front-stage purification unit 1. Then, the used front-stage purification unit 1 is calcined at high temperature to remove the accumulated carbon black therein. Subsequently, the purification unit is purged with a high-speed air flow in the reverse direction, and the ash is blown out from the inlet of the purification unit to make it return to the fresh state. The replacement regeneration process is relatively complex and requires at least one set of backup front-stage purification units 1, increasing the operating cost.

[0032] In-situ regeneration is to install a regeneration device in the above catalytic purification system, which is a preferred solution. As Figure 6 shown, that is, a heating wire mesh 4 is arranged between the front-stage purification unit 1 and the rear-stage catalytic unit 2, and the heating wire mesh 4 can be heated to above 200 °C. A fan 5 is also arranged in the exhaust pipe 3 behind the rear-stage catalytic unit 2, and the fan 5 can blow the air flow back to the front-stage purification unit 1. Under the action of the high-temperature air flow, the front-stage purification unit 1 is regenerated.

[0033] The porosity of the front-stage flow holes in the structure of the front-stage purification unit 1 is 60%, and the median pore diameter is 12 μm.

[0034] The selection of the regeneration timing can be achieved by fixing the operating time and monitoring the exhaust back pressure of the pre-stage purification unit 1. The method of fixing the operating time means that regeneration is forced after the catalytic purification system has operated for a certain period of time. This method of control is relatively rough. The preferred solution is to achieve it by monitoring the exhaust back pressure, that is, by installing differential pressure sensors at the inlet and outlet ends of the pre-stage purification unit 1. The differential pressure sensors can monitor the exhaust differential pressure of the pre-stage purification unit 1 and are used for the selection of the regeneration timing.

[0035] Application test on the side line of CO purification for the tail gas of iron and steel sintering machine:

[0036] The embodiments 1 and 2 provided by the present utility model and the conventional CO catalytic purification system are applied to the side line purification of the tail gas of a certain iron and steel sintering machine. Among them, the exhaust pipeline 3 of the conventional CO catalytic purification system only contains a catalytic unit, and the structure of the catalytic unit and the parameters of the CO catalytic oxidation active coating are the same as those of embodiments 1 and 2. The test parameters and the main pollutant components in the tail gas are shown in Table 1:

[0037] Table 1 Test parameters and main pollutant components in the tail gas

[0038]

[0039]

[0040] In addition to the pollutant components listed in Table 1, it is inferred from the analysis results of raw materials and catalyst deposits that there are also small amounts of carbon black, fly ash and halogen compounds in the tail gas. Limited by the on-line gas analysis equipment, real-time content test results cannot be obtained.

[0041] As above, embodiments 1, 2 and the comparative example are respectively applied to the side line of the above-mentioned iron and steel sintering machine tail gas. The CO content at the inlet and outlet of the catalytic purification system is regularly monitored and the CO conversion efficiency is calculated. At the same time, the exhaust differential pressure of the pre-stage purification unit 1 is also monitored by the differential pressure sensors in the solutions of embodiments 1 and 2. The conversion rate of CO and the change of the exhaust differential pressure of the pre-stage purification unit 1 during different operation periods are shown in Table 2.

[0042] Table 2 Monitoring of CO conversion efficiency and exhaust differential pressure

[0043]

[0044] Note: Based on the requirements of the engineering target, the CO conversion rate needs to be maintained above 95%.

[0045] It can be seen from the comparison results in Table 2 that the pollutant conversion efficiency of the comparative example decreased significantly after running for 50 h and could no longer meet the requirements of the engineering target. The CO catalytic purification systems provided by Embodiments 1 and 2 can stably maintain a high CO conversion efficiency within 800 h of operation time and meet the requirements of the engineering target.

[0046] The exhaust gas pressure difference of the CO catalytic purification systems provided in Embodiments 1 and 2 increased by approximately 5 kPa after running for 800 h. Here, the pre-stage purification unit 1 was regenerated by the regeneration device attached to Embodiment 2. The regeneration conditions were that the temperature of the heating wire mesh 4 rose to 400 °C, the fan 5 was turned on, and the air volume was controlled to be 200 m 3 / h, and the regeneration process time was 30 min. After the above regeneration treatment, the exhaust gas pressure difference of the pre-stage purification unit 1 of Embodiment 2 decreased from 8.5 kPa to 3.7 kPa, which was basically equivalent to the initial state.

[0047] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present utility model. However, the present utility model is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present utility model, and these modifications and improvements are also regarded as the protection scope of the present utility model.

Claims

1. A steel sintering machine tail gas CO catalytic purification system, comprising an exhaust pipe (3), characterized in that: A front-stage purification unit (1) and a rear-stage catalytic unit (2) are sequentially installed in the exhaust pipe (3); the front-stage purification unit (1) is a wall-flow type honeycomb ceramic structure, comprising a front-stage ceramic shell (11), wherein the front-stage ceramic shell (11) is provided with front-stage flow holes in an array, plugs (12) are installed at the front end or rear end of the front-stage flow holes, and the plugs (12) in adjacent front-stage flow holes are located at different ends; the rear-stage catalytic unit (2) is a straight-through type honeycomb ceramic structure, comprising a rear-stage ceramic shell (21), wherein the rear-stage ceramic shell (21) is provided with rear-stage flow holes in an array, and the rear-stage flow holes are coated with a CO catalytic oxidation active coating.

2. The steel sintering machine tail gas CO catalytic purification system according to claim 1, characterized in that: A CO catalytic oxidation active coating is coated inside the front-stage flow hole of the front-stage purification unit (1).

3. The steel sintering machine tail gas CO catalytic purification system according to claim 1, characterized in that: The porosity of the front-stage flow holes in the structure of the front-stage purification unit (1) is 50-60%, and the median pore size is 12-20 μm.

4. The steel sintering machine tail gas CO catalytic purification system according to claim 1, characterized in that: A heating screen (4) is arranged between the front-stage purification unit (1) and the rear-stage catalytic unit (2), and a fan (5) is also arranged in the exhaust pipe (3) behind the rear-stage catalytic unit (2).

5. The steel sintering machine tail gas CO catalytic purification system according to claim 1, characterized in that: The heating screen (4) can be heated to above 200°C.

6. The steel sintering machine tail gas CO catalytic purification system according to claim 1, characterized in that: Pressure difference sensors are installed at the air inlet and outlet ends of the pre-purification unit (1).

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