Denitration device and method for reducing fuel consumption of low-temperature flue gas catalytic denitration

Abstract

The invention discloses a denitration device and method for reducing low-temperature flue gas catalytic denitration fuel consumption, the denitration device comprises a desulfurization device, a dust remover, an SCR reactor, an induced draft fan and a chimney which are sequentially communicated through flues, and heat exchangers are arranged on the flues at the input end and the output end of the SCR reactor; a heat exchanger is arranged at the input end of the SCR reactor, a hot blast stove and a reducing agent spraying device are sequentially arranged on a flue between the heat exchanger and the input end of the SCR reactor, and a CO oxidation catalyst and a plurality of denitration catalysts located above the CO oxidation catalyst are arranged in the SCR reactor. According to the low-temperature flue gas SCR denitration device, NOx and CO up-to-standard emission of sintering flue gas, steel rolling flue gas and the like which are relatively low in temperature of iron and steel enterprises can be continuously and stably achieved, the requirement of SCR denitration for flue gas temperature rising can be met, fuel consumption of a hot blast stove is reduced, and the low-temperature flue gas SCR denitration operation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection technology equipment, and in particular to a denitration device and method for reducing fuel consumption of catalytic denitration of low-temperature flue gas. Background Art

[0002] Iron and steel enterprises are equipped with coking, ironmaking and steelmaking processes, which also produce dust, SO2, NO X In addition, due to the influence of raw materials, fuel and carbon addition, some flue gas in steel mills contains a large amount of CO, and its concentration is generally 6000~12000mg / m 3 Its emissions account for about 50% of steel mills, and the emission equivalent has a great impact on the ambient air quality. Therefore, it is imperative to use ultra-low emission technology to treat the polluted flue gas emitted by existing steel.

[0003] At present, the treatment of SO2 produced by steel enterprises generally adopts semi-dry and dry desulfurization technology, and the treatment of dust adopts high-efficiency bag dust removal technology. X The treatment adopts the selective catalytic reduction denitrification technology (SCR technology). The applicable temperature window of the mature denitrification catalyst currently used is 180~500℃. It has a high denitrification effect within this temperature range. If the flue gas temperature is lower than the minimum operating temperature, it is necessary to use an external hot air method to continuously heat the flue gas before denitrification to above 180℃. The heating fuels used are mainly coke oven gas, blast furnace gas and converter gas. X For the treatment of CO, most of the current steel flue gas has been equipped with SCR denitrification equipment, and a catalyst spare empty layer is provided in the reactor. However, the treatment of CO has not yet been popularized in the existing steel flue gas.

[0004] The applicable temperature window of the mature denitrification catalyst used in the current SCR denitrification technology is 180~500℃. It has a high denitrification effect within this temperature range and is widely used in high-temperature flue gas purification in the power industry, cement industry, etc. Because the flue gas temperature meets the use requirements of the catalyst, the denitrification effect can be achieved by placing the catalyst in the flue gas; however, the flue gas temperature generated in some steel production processes such as sintering, steel rolling and coking is less than 180℃. Some denitrification equipment is placed at the rear end of wet desulfurization, and the flue gas temperature is even lower, only about 50℃, which belongs to the category of low-temperature flue gas denitrification. In order to meet the minimum use temperature of the catalyst, a hot blast furnace is required to continuously heat the flue gas to above 180℃ during denitrification. The heating fuels used are mainly coke oven gas, blast furnace gas and converter gas, etc. However, due to the large amount of flue gas, the heat required for heating is huge, and the fuel consumption is high, resulting in the high cost of denitrification operation; with a 430m 2Taking the sintering flue gas treatment as an example, if the flue gas temperature is increased by 30°C, if blast furnace gas is used as the heat source, the annual blast furnace gas cost can reach 15.5 million yuan. If converter gas is used as the heat source, the annual converter gas cost will be even higher, reaching 42 million yuan. Summary of the invention

[0005] The purpose of the present invention is to solve the problems in the prior art and to propose a denitrification device and method for reducing the fuel consumption of catalytic denitrification of low-temperature flue gas. The separate NOx removal equipment and CO removal equipment are combined together, so that the relatively low-temperature sintering flue gas and steel rolling flue gas of the steel enterprise can continuously and stably achieve the emission standards of NOx and CO, and can meet the needs of SCR denitrification for flue gas heating, reduce the fuel consumption of the hot blast furnace, and reduce the operating cost of SCR denitrification of low-temperature flue gas.

[0006] To achieve the above-mentioned purpose, the present invention proposes a denitrification device for reducing fuel consumption of catalytic denitrification of low-temperature flue gas, comprising a desulfurization device, a dust collector, an SCR reactor, an induced draft fan and a chimney which are sequentially connected through a flue, a heat exchanger is provided on the flue at the input end and the output end of the SCR reactor, a hot air furnace and a reducing agent injection device are sequentially provided on the flue between the heat exchanger and the input end of the SCR reactor, and a CO oxidation catalyst and a plurality of denitrification catalysts located above the CO oxidation catalyst are provided in the SCR reactor.

[0007] Preferably, two or three layers of denitration catalysts are arranged at intervals in the SCR reactor.

[0008] Preferably, the main active components of the CO oxidation catalyst include precious metals or non-precious metals, the precious metal catalysts include one or more of Pd, Pt, Au, and Ag, and the non-precious metal catalysts include one or more of Cu, Mn, Co, and Fe.

[0009] Preferably, the denitration catalyst and the CO oxidation catalyst are both honeycomb-type, and the number of holes in the catalyst is 25 to 35 holes.

[0010] Preferably, nitrogen oxides and CO can be removed simultaneously in the SCR reactor (1).

[0011] Preferably, the heat exchanger is a rotary, plate or tubular heat exchanger, which transfers a large amount of chemical heat generated by the catalytic combustion of CO from its hot end to its cold end, thereby increasing the flue gas temperature at the denitrification inlet of the SCR reactor by 15-35°C.

[0012] Preferably, the combustion fuel used in the hot blast stove is coke oven gas, blast furnace gas or converter gas.

[0013] A method for reducing fuel consumption for catalytic denitration of low-temperature flue gas, which is based on the above-mentioned denitration device for reducing fuel consumption for catalytic denitration of low-temperature flue gas, comprising: firstly passing the 100-150°C flue gas from sintering / rolling through a dry / wet desulfurization device for desulfurization reaction, and then passing the flue gas with SO2 removed through a dust collector for dust removal. At this time, the outlet flue gas temperature of the dust collector becomes 50-80°C, and the low-temperature flue gas first enters from the cold end inlet of the heat exchanger and flows out from the cold end outlet. Under the action of the heat exchanger, The temperature of the flue gas flowing out from the cold end outlet rises to 150~250℃, and then high-temperature hot air is added through the hot blast furnace to increase the flue gas temperature from 150~250℃ to 180~280℃. At the beginning, the heat required for the flue gas temperature rise is provided by the combustion of gaseous fuel in the hot blast furnace. When the flue gas reaches the temperature window of the denitration catalyst, the denitration reducing agent is sprayed from the denitration reducing agent injection device. The flue gas and the reducing agent are fully mixed in the flue at the denitration inlet and then contact the denitration catalyst at the top of the SCR reactor, thereby achieving NO X Removal of NO X The flue gas then contacts the CO oxidation catalyst at the bottom of the SCR reactor. The CO in the flue gas undergoes an oxidation combustion reaction under the action of the CO oxidation catalyst, and while achieving CO removal, a large amount of chemical reaction heat is generated, raising the flue gas temperature from 180~280℃ after denitrification to 200~310℃. Under the action of the heat exchanger, the flue gas at 200~310℃ transfers heat from the hot end to the cold end, thereby raising the flue gas at the cold end outlet of the heat exchanger from 150~250℃ to 180~280℃, thereby reducing the fuel consumption of the hot blast furnace, and even stopping the hot blast furnace to supplement the heat for the flue gas, saving a lot of fuel; under the action of the heat exchanger, the flue gas after CO oxidation and temperature increase drops from 200~310℃ at the hot end inlet to 80~110℃ at the hot end outlet, and is finally drawn out by the induced draft fan and discharged through the chimney.

[0014] Beneficial effects of the present invention: 1. By combining the separate NOx removal equipment and CO removal equipment, the sintering flue gas and steel rolling flue gas with relatively low temperature in steel enterprises can continuously and stably achieve the emission of NOx and CO up to standard. Compared with other technologies, it has the following advantages: 1. Using catalysts containing precious metals or non-precious metals, through oxidation catalytic combustion, the emission of CO pollutants in flue gas can be reduced; 2. The catalyst used for removing CO can be arranged in the spare layer of the existing SCR denitrification reactor, sharing the reactor and bracket, not occupying other sites, with low investment and short transformation cycle; 3. When CO is removed, catalytic combustion releases a large amount of chemical heat. After the flue gas temperature rises, the heat is transferred to the flue gas at the front end of denitrification through the heat exchanger, which indirectly realizes the recovery of heat energy, can meet the needs of SCR denitrification for flue gas heating, reduce the fuel consumption of the hot blast furnace, and reduce the operating cost of SCR denitrification of low-temperature flue gas; 4. CO catalyst has a certain effect of removing NOx, which can synergistically improve the SCR denitrification efficiency and reduce the consumption of denitrification reducing agent; 5. When CO is removed, it will consume oxygen in the flue gas, thereby reducing the oxygen content in the flue gas. After conversion to standard oxygen, the indicators of various pollutants in the flue gas will be indirectly reduced.

[0015] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a denitration device for reducing fuel consumption of catalytic denitration of low-temperature flue gas according to the present invention.

[0017] In the figure: 1-SCR reactor, 2-denitrification catalyst, 3-CO oxidation catalyst, 4-heat exchanger, 5-induced draft fan, 6-chimney, 7-hot blast furnace, 8-reducing agent injection device, 9-flue, 10-desulfurization device, 11-dust collector. DETAILED DESCRIPTION

[0018] See also Figure 1 The present invention discloses a denitration device for reducing fuel consumption of catalytic denitration of low-temperature flue gas, comprising a desulfurization device 10, a dust collector 11, an SCR reactor 1, an induced draft fan 5 and a chimney 6 which are sequentially connected through a flue 9, a heat exchanger 4 is provided on the flue 9 at the input end and the output end of the SCR reactor 1, a hot air furnace 7 and a reducing agent injection device 8 are sequentially provided on the flue 9 between the heat exchanger 4 and the input end of the SCR reactor 1, and a CO oxidation catalyst 3 and a plurality of denitration catalysts 2 located above the CO oxidation catalyst 3 are provided in the SCR reactor 1.

[0019] The SCR reactor 1 is a rectangular parallelepiped structure. Two or three layers of denitration catalysts 2 are arranged in the SCR reactor 1. The denitration catalyst 2 is arranged on the top layer of the SCR reactor 1 to remove NO in the flue gas. X The CO oxidation catalyst 3 is arranged at the original reserved position at the bottom layer inside the SCR reactor 1 .

[0020] The main active components of the CO oxidation catalyst 3 are precious metals or non-precious metals. Precious metal catalysts include one or more of Pd, Pt, Au, and Ag, and non-precious metal catalysts include one or more of Cu, Mn, Co, and Fe.

[0021] The denitration catalyst 2 and the CO oxidation catalyst 3 are both honeycomb-type, and the number of holes in the catalyst is 25 to 35 holes.

[0022] In the SCR reactor (1), nitrogen oxides and CO can be removed simultaneously.

[0023] The heat exchanger 4 is a rotary, plate or tubular heat exchanger. The heat exchanger 4 transfers a large amount of chemical heat generated by the combustion of CO oxidation catalyst 3 from its hot end to its cold end, thereby increasing the flue gas temperature at the denitration inlet of the SCR reactor 1 by 15-35°C.

[0024] The combustion fuel used by the hot blast stove 7 is coke oven gas, blast furnace gas or converter gas.

[0025] A method for reducing fuel consumption of catalytic denitration of low-temperature flue gas, the method is based on the above-mentioned denitration device for reducing fuel consumption of catalytic denitration of low-temperature flue gas, comprising: the 100-150°C flue gas from sintering / rolling first passes through a dry / wet desulfurization device 10 for desulfurization reaction, the flue gas with SO2 removed then passes through a dust collector 11 for dust removal, at which time the outlet flue gas temperature of the dust collector 11 becomes 50-80°C, the low-temperature flue gas first enters from the cold end inlet of the heat exchanger 4 and flows out from the cold end outlet, under the action of the heat exchanger 4 , the temperature of the flue gas flowing out from the cold end outlet rises to 150~250℃, and then high-temperature hot air is added through the hot blast furnace 7 to increase the flue gas temperature from 150~250℃ to 180~280℃. At the beginning, the heat required for the flue gas temperature rise is provided by the combustion of gaseous fuel by the hot blast furnace 7. When the flue gas reaches the temperature window of the denitration catalyst, the denitration reducing agent is sprayed from the denitration reducing agent injection device 8. The flue gas and the reducing agent are fully mixed in the flue 9 at the denitration inlet and then contact the denitration catalyst 2 at the upper part of the SCR reactor 1, thereby achieving NO X Removal of NO X The flue gas then contacts the CO oxidation catalyst 3 at the bottom of the SCR reactor 1. The CO in the flue gas undergoes an oxidation combustion reaction under the action of the CO oxidation catalyst 3. While achieving CO removal, a large amount of chemical reaction heat is generated, raising the flue gas temperature from 180-280°C after denitration to 200-310°C. Under the action of the heat exchanger 4, the flue gas at 200-310°C transfers heat from the hot end to the cold end, thereby raising the flue gas at the cold end outlet of the heat exchanger 4 from 150-250°C to 180-280°C, thereby reducing the fuel consumption of the hot blast furnace 7, and even stopping the hot blast furnace 7 to supplement the heat for the flue gas, saving a large amount of fuel. Under the action of the heat exchanger 4, the flue gas temperature after CO oxidation and temperature increase drops from 200-310°C at the hot end inlet to 80-110°C at the hot end outlet, and is finally drawn out by the induced draft fan 5 and discharged through the chimney 6.

[0026] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration, characterized in that: The invention comprises a desulfurization device (10), a dust collector (11), an SCR reactor (1), an induced draft fan (5) and a chimney (6) which are sequentially connected through a flue (9); a heat exchanger (4) is provided on the flue (9) at the input end and the output end of the SCR reactor (1); a hot air furnace (7) and a reducing agent injection device (8) are sequentially provided on the flue (9) between the heat exchanger (4) and the input end of the SCR reactor (1); a CO oxidation catalyst (3) and a plurality of denitrification catalysts (2) located above the CO oxidation catalyst (3) are provided in the SCR reactor (1).

2. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: Two or three layers of denitration catalysts (2) are arranged at intervals in the SCR reactor (1).

3. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: The main active components of the CO oxidation catalyst (3) are precious metals or non-precious metals. The precious metal catalysts include one or more of Pd, Pt, Au, and Ag. The non-precious metal catalysts include one or more of Cu, Mn, Co, and Fe.

4. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: The denitration catalyst (2) and the CO oxidation catalyst (3) are both honeycomb-type, and the number of holes in the catalyst is 25 to 35.

5. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: In the SCR reactor (1), nitrogen oxides and CO can be removed simultaneously.

6. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: The heat exchanger (4) is a rotary, plate or tube heat exchanger. The heat exchanger (4) transfers a large amount of chemical heat generated by the CO oxidation catalytic combustion (3) from its hot end to its cold end, thereby increasing the flue gas temperature at the denitration inlet of the SCR reactor (1) by 15 to 35°C.

7. A denitration device for reducing fuel consumption of low-temperature flue gas catalytic denitration according to claim 1, characterized in that: The combustion fuel used by the hot blast stove (7) is coke oven gas, blast furnace gas or converter gas.

8. A method for reducing fuel consumption for catalytic denitration of low-temperature flue gas, the method being implemented based on a denitration device for reducing fuel consumption for catalytic denitration of low-temperature flue gas according to any one of claims 1 to 7, characterized in that: The 100-150°C flue gas from sintering / rolling first passes through a dry / wet desulfurization device (10) for desulfurization reaction. The flue gas with SO2 removed then passes through a dust collector (11) for dust removal. At this time, the outlet flue gas temperature of the dust collector (11) becomes 50-80°C. The low-temperature flue gas first enters the cold end inlet of the heat exchanger (4) and flows out from the cold end outlet. Under the action of the heat exchanger (4), the flue gas temperature flowing out from the cold end outlet rises to 150-250°C. Then, it passes through the heat exchanger (4) for desulfurization. The blast furnace (7) introduces high-temperature hot air to raise the flue gas temperature from 150-250°C to 180-280°C. At the beginning, the heat required for the flue gas temperature rise is provided by the combustion of gaseous fuel by the hot blast furnace (7). When the flue gas reaches the temperature window of the denitration catalyst, the denitration reducing agent is sprayed from the denitration reducing agent injection device (8). The flue gas and the reducing agent are fully mixed in the flue duct (9) at the denitration inlet and then contact the denitration catalyst (2) at the upper part of the SCR reactor (1), thereby achieving NO X Removal of NO X The flue gas then contacts the CO oxidation catalyst (3) at the bottom of the SCR reactor (1). The CO in the flue gas undergoes an oxidation combustion reaction under the action of the CO oxidation catalyst (3). While achieving CO removal, a large amount of chemical reaction heat is generated, raising the flue gas temperature from 180-280°C after denitration to 200-310°C. The flue gas at 200-310°C transfers heat from the hot end to the cold end under the action of the heat exchanger (4), thereby raising the flue gas at the cold end outlet of the heat exchanger (4) from 150-250°C to 180-280°C. This reduces the fuel consumption of the hot blast furnace (7), and even allows the hot blast furnace (7) to be stopped to supplement the flue gas with heat, thereby saving a large amount of fuel. After the flue gas is heated by CO oxidation, its temperature drops from 200-310°C at the hot end inlet to 80-110°C at the hot end outlet under the action of the heat exchanger (4), and is finally drawn out by the induced draft fan (5) and discharged through the chimney (6).

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