Tail gas purification device of stepping gas heating furnace

Abstract

The utility model provides a stepping type gas heating furnace tail gas purification device which is installed on a flue of a heating furnace and comprises a flow mixer, a dust remover and an SCR reactor which are sequentially communicated in the flue gas flowing direction, the flow mixer is provided with a flue inlet and an ammonia gas inlet, and the SCR reactor is filled with a urea catalyst. The tail gas treatment device has the beneficial effects that the emission of nitrogen oxides in tail gas stably reaches the standard through a multi-stage treatment structure. The flow mixer integrates the flue inlet and the ammonia gas inlet, so that high-temperature flue gas and ammonia gas are guided by the swirl vanes to form turbulent mixing, ideal pretreatment conditions are created for SCR reaction, the initial distribution uniformity of nitrogen oxides is improved by 50%, and the problem of local ammonia escape or denitration dead angles is avoided.

Description

Technical Field

[0001] This utility model relates to the field of exhaust gas treatment technology, specifically to a step-type gas heating furnace exhaust gas purification device. Background Technology

[0002] As an important continuous heating device in modern industry, the walking beam gas furnace works by periodically raising and lowering and translating the furnace bottom or water-cooled metal beams, driving the steel billet along a rectangular trajectory through the high-temperature furnace chamber to achieve uniform heating. This design significantly improves the continuity of heat treatment, temperature control accuracy, and production efficiency, and is particularly suitable for large-scale steel rolling and forging production lines. Its fuel is primarily natural gas or liquefied petroleum gas (LPG), and the combustion process must be carried out at high temperatures to ensure the uniformity of billet heating and process stability. However, this high-temperature combustion characteristic also brings significant exhaust emission problems.

[0003] The exhaust gases produced by gas combustion contain a variety of harmful substances, including nitrogen oxides (NOx), carbon monoxide (CO), sulfur oxides (SOx), and volatile organic compounds (VOCs). Among these, nitrogen oxides are particularly harmful: on the one hand, nitrogen oxides combine with water in the atmosphere to form nitric acid, leading to acid rain and corroding buildings and vegetation; on the other hand, long-term exposure to nitrogen oxides can cause respiratory mucosal corrosion, decreased lung function, impaired blood oxygen-carrying capacity, and even increase the risk of cancer. For example, nitrogen dioxide can directly damage alveolar cells, inducing pulmonary edema, and react with respiratory secretions to form the potent carcinogen nitrite.

[0004] The problem of excessive nitrogen oxide emissions from walking beam gas-fired furnaces is particularly prominent, mainly due to two factors: First, during high-temperature combustion, 78% of the nitrogen in the air is activated in the high-temperature zone of the furnace, reacting with oxygen to produce NO, and the formation rate increases exponentially with temperature. Second, differences in natural gas composition, frequent fluctuations in combustion load, and uneven mixing of air and gas all exacerbate incomplete combustion. Especially in actual production, temperature fluctuations caused by steel billets entering and leaving the furnace, and changes in gas pressure, all disrupt combustion stability, further increasing nitrogen oxide concentrations. With increasingly stringent environmental standards, the exhaust gas from traditional walking beam gas-fired furnaces is insufficient to meet current low-NOx emission requirements. Utility Model Content

[0005] To address the issue of excessive nitrogen oxide content in the exhaust gas of walking beam gas heaters;

[0006] This utility model provides a step-type gas furnace exhaust gas purification device, which is installed on the flue of the furnace. It includes a mixer, a dust collector and an SCR reactor connected in sequence along the flue gas flow direction. The mixer is provided with a flue gas inlet and an ammonia inlet, and the SCR reactor is filled with urea catalyst.

[0007] As a preferred embodiment, the dust collector is equipped with a metal wire filter screen, the mesh size of which is 80 to 100 mesh.

[0008] As a preferred embodiment, the dust collector is detachably connected to a dust collection container at its bottom.

[0009] As a preferred embodiment, a first flow equalizer is installed on the flue gas conveying section between the mixer and the dust collector.

[0010] As a preferred embodiment, a second flow equalizer is installed on the flue gas output section between the SCR reactor and the flue.

[0011] As a preferred embodiment, the second flow equalizer is equipped with a compensator connected to the flue, the compensator being used to compensate for thermal displacement.

[0012] The beneficial effects of this utility model are as follows:

[0013] 1. This utility model achieves stable compliance of nitrogen oxide emissions in exhaust gas through a multi-stage treatment structure. The mixer integrates the flue gas inlet and the ammonia inlet, so that the high-temperature flue gas and ammonia gas form turbulent mixing under the guidance of the swirl blades, creating ideal pretreatment conditions for the SCR reaction, improving the initial uniformity of nitrogen oxide distribution by 50%, and avoiding the problems of local ammonia escape or denitrification dead zones.

[0014] 2. The dust collector of this utility model is equipped with an 80-100 mesh metal wire filter screen, which has an efficiency of over 92% in capturing iron filings and dust under 600℃ conditions. The pre-dust removal reduces the dust load entering the SCR reactor to below 20mg / m³, reduces the probability of catalyst pore blockage by 70%, and ensures a significant extension of the catalytic activity life.

[0015] 3. The first-stage flow equalizer at the front end of the dust collector of this utility model adopts a porous baffle structure, which compresses the standard deviation of the flue gas velocity field from the initial 35% to less than 12%; the second-stage flow equalizer at the rear end of the SCR reactor integrates a compensator, which effectively absorbs the thermal displacement of ±80mm. The dual-stage regulation makes the inlet velocity deviation of the SCR reactor <5%, and increases the ammonia coverage of the catalyst surface to 98%, while avoiding the risk of flange leakage caused by thermal stress. Attached Figure Description

[0016] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0017] Figure 1 This is a schematic diagram of the structure of this utility model;

[0018] The numbers in the attached diagram are:

[0019] 1. Mixer; 11. Flue gas inlet; 12. Ammonia inlet; 2. First flow equalizer; 3. Dust collection container; 4. Dust collector; 5. SCR reactor; 6. Second flow equalizer; 7. Compensator; 8. Flue gas. Detailed Implementation

[0020] To illustrate the features of this utility model, the following description, in conjunction with the accompanying drawings and embodiments, will further explain this utility model.

[0021] Example:

[0022] Please see Figure 1 This utility model provides a step-type gas furnace exhaust gas purification device. Its structure, along the flue gas flow direction, sequentially connects a mixer 1, a first flow equalizer 2, a dust collector 4 with a wire mesh filter, an SCR reactor 5, and a second flow equalizer 6. The end is connected to a flue duct 8 via a compensator 7. The mixer 1 has a flue inlet 11 on its left side connecting to the furnace flue gas source, and an ammonia inlet 12 at its top for ammonia injection. The dust collector 4 is fitted with a swing-type dust collection container 3 at its bottom, with a 90-mesh stainless steel wire mesh filter installed inside. The SCR reactor 5 is filled with a honeycomb urea catalyst with a pore density of 300 cpsi. The first flow equalizer 2 is installed in the middle section of a DN500 pipe between the mixer 1 and the dust collector 4. The second flow equalizer 6 is connected to the flue duct 8 via a corrugated compensator 7, which can absorb an axial thermal displacement of 15 mm.

[0023] During operation, 780℃ high-temperature flue gas enters the mixer 1 from the flue inlet 11 at a flow rate of 12 m / s, forming a turbulent mixture with atomized ammonia gas injected at a pressure of 0.3 MPa from the ammonia inlet 12. After the airflow is adjusted by the guide vanes of the first flow equalizer 2, it evenly impacts the metal wire filter of the dust collector 4, intercepting iron filings and some dust. The collected ash falls into the dust collection container 3. The purified airflow then enters the SCR reactor 5, where the urea catalyst increases the NOx reduction rate to over 95% at 310℃. Finally, the flue gas passes through the second flow equalizer 6 to eliminate eddies, and is buffered by the 12 mm pipe contraction caused by the sudden temperature drop through the compensator 7 before being discharged from the flue 8 in compliance with the Ministry of Environmental Protection's requirement of nitrogen oxide emissions being less than 50 mg / m³. 3 The standard.

[0024] This embodiment achieves stable compliance of nitrogen oxide emissions in exhaust gas through a multi-stage treatment structure; and the mixer integrates the flue gas inlet and ammonia inlet, so that the high-temperature flue gas and ammonia are mixed in turbulent flow under the guidance of the swirl blades, creating ideal pretreatment conditions for the SCR reaction, improving the initial uniformity of nitrogen oxide distribution by 50%, and avoiding the problems of local ammonia escape or denitrification dead zones.

[0025] The above embodiments and accompanying drawings are only used to illustrate the technical solutions of this utility model and are not intended to limit this utility model. This utility model has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of this utility model do not depart from the spirit of this utility model and should also fall within the protection scope of the claims of this utility model. Other related technical structures not disclosed in detail in this utility model are existing technologies in the art.

Claims

1. A step-type gas furnace exhaust gas purification device, installed on the flue (8) of the furnace, characterized in that: It includes a mixer (1), a dust collector (4) and an SCR reactor (5) connected in sequence along the flue gas flow direction. The mixer (1) is provided with a flue gas inlet (11) and an ammonia gas inlet (12). The SCR reactor (5) is filled with a urea catalyst.

2. The step-type gas furnace exhaust gas purification device according to claim 1, characterized in that: The dust collector (4) is equipped with a metal wire filter screen, the mesh size of which is 80 to 100 mesh.

3. The step-growth gas purification device for a gas-fired furnace according to claim 2, characterized in that: The dust collector (4) is detachably connected to a dust collection container (3) at its bottom.

4. The step-growth gas furnace exhaust gas purification device according to claim 1, characterized in that: A first flow equalizer (2) is installed on the flue gas conveying section between the mixer (1) and the dust collector (4).

5. The step-growth gas purification device for a gas-fired furnace according to claim 1, characterized in that: A second flow equalizer (6) is installed on the flue gas output section between the SCR reactor (5) and the flue (8).

6. The step-growth gas purification device for a gas-fired furnace according to claim 5, characterized in that: The second flow equalizer (6) is equipped with a compensator (7) connected to the flue (8), and the compensator (7) is used to compensate for thermal displacement.

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