Denitrification equipment and cement kiln exhaust gas treatment equipment

Abstract

SOLUTION: A denitration device is provided, having an inlet duct, a denitration reactor and an outlet duct. In the denitration device, exhaust gas from a furnace can be flown to the inlet duct, the denitration reactor and the outlet duct in this order, the denitration reactor has a flow passage in which the exhaust gas flows nearly vertically at a linear velocity of 5-8 m / sec, a screen plate and a static bed including a denitration catalyst are arranged in this order along the flow direction in the flow passage, and the static bed has an opening of 7 mm or more, the inlet duct has in the inlet side, a flow passage in which the exhaust gas flows upward and has in the outlet side, a flow passage in which the exhaust gas flows downward, the area of a flow passage cross section between the upward flowing flow passage and the downward flowing flow passage is smaller than the area of an upward flowing flow passage cross section, a hopper is provided below in the downward flowing flow passage, a dam is provided on the edge side of the hopper on the near side to the downward flowing flow passage, and a suit blower is provided in a place where dust is liable to be piled up in each of the flow passages of the inlet duct and the denitration reactor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a denitrification device. And cement kiln exhaust gas treatment equipment More specifically, the present invention relates to a denitrification device suitable for a cement plant or the like that discharges gas containing highly adhesive dust. And cement kiln exhaust gas treatment equipment Regarding. [Background technology]

[0002] Gases emitted from cement kilns include hydrogen chloride, SO x , NO x Therefore, the NO in the exhaust gas is x In order to reduce the concentration, denitrification of exhaust gas is carried out by adding denitrification agents such as ammonia and urea. x It breaks down NO and NO2 into nitrogen (N2) and water (H2O).

[0003] For example, Patent Document 1 discloses an exhaust gas treatment device for a cement kiln, which is characterized by comprising a dust collector that collects dust in the exhaust gas from the cement kiln, a gas addition device that adds an ammonia-containing gas discharged from a fermentation treatment device to the exhaust gas after the dust has been collected by the dust collector, and a catalytic device that denitrifies the exhaust gas after the ammonia-containing gas has been added by the gas addition device.

[0004] Patent Document 2 discloses a cement kiln exhaust gas treatment device comprising a dust collector for collecting dust in cement kiln exhaust gas, a catalyst poisoning substance removal device for removing catalyst poisoning substances from the cement kiln exhaust gas that has passed through the dust collector, a preheating device for preheating the cement kiln exhaust gas that has passed through the catalyst poisoning substance removal device, and a catalytic device for removing one or more substances selected from nitrogen oxides, volatile organic compounds, carbon monoxide, persistent organic pollutants, hydrocarbons and odorous substances in the cement kiln exhaust gas preheated by the preheating device.

[0005] A fair amount of dust remains in the exhaust gas after passing through the dust collector, and this dust can accumulate in the denitration equipment. Various technologies have been proposed to deal with this problem.

[0006] For example, Patent Document 3 discloses an ash scattering nozzle structure for boilers that contain a large amount of ash in the exhaust gas, such as coal-fired boilers or cement kiln exhaust gas boilers, in which an ash scattering nozzle is attached by penetrating the flue in parts of the flue from the boiler outlet to the chimney where stagnation of the flow is likely to occur, or in parts with a slow flow rate where ash is likely to accumulate, and which is characterized by having a mechanism for manually or automatically rotating the nozzle to change the air injection direction and thereby scattering the ash.

[0007] Patent Document 4 discloses a flue gas denitration apparatus in which a catalytic reactor equipped with a catalyst that removes nitrogen oxides in exhaust gas in the presence of ammonia is disposed in an inlet flue of exhaust gas, and a plurality of ammonia water injection nozzles are disposed in the inlet flue region where exhaust gas flows horizontally upstream of the catalytic reactor, and the apparatus is characterized in that a soot blower is installed on the lower wall surface of the horizontal flue region downstream of the ammonia water injection nozzles.

[0008] Patent Document 5 discloses a denitration device having an ammonia injection tube inserted into an exhaust gas duct extending in a horizontal direction from above the exhaust gas duct, an ammonia water injection nozzle provided on the ammonia injection tube for spraying ammonia water, and a denitration catalyst layer provided downstream in the exhaust gas flow direction of the ammonia injection tube, the denitration device being characterized in having a gas injection means for injecting gas toward a bottom surface of the exhaust gas duct below the ammonia injection tube.

[0009] Patent Document 6 discloses a flue gas nitrogen oxide treatment system having an inlet at the upper end of a reactor, an exhaust port at the lower end of the reactor, and an ash receiving tank provided between the catalyst layer and the inlet, an ash receiving passage having one end communicating with the ash receiving tank and the other end communicating with the exhaust port, a flap and an ash discharge port provided midway through the ash receiving passage, and a compressed air nozzle disposed in the catalyst layer.

[0010] Patent Document 7 discloses an exhaust gas treatment device that reduces nitrogen oxides in exhaust gas discharged from a coal-fired boiler using a denitration device, the exhaust gas treatment device comprising: a horizontal duct extending in a substantially horizontal direction and a vertical duct extending in a substantially vertical direction, a front end of the horizontal duct communicating with an exhaust gas outlet of the coal-fired boiler and a rear end of the horizontal duct communicating with a lower end of the vertical duct, a duct defining an internal space through which exhaust gas discharged from the coal-fired boiler flows from the horizontal duct to the upper side of the vertical duct and is guided to the denitration device; a hopper provided below the vertical duct and communicating with the duct internal space via a hopper upper end opening; and an inclined collision plate that extends upward continuously from the rear end edge of the hopper upper end opening and is fixed to a rear surface of the duct that defines the rear of the duct internal space, and that extends at a downward angle forward from the rear surface.

[0011] Patent Document 8 discloses an exhaust gas treatment device comprising a denitration device having a denitration catalyst that reduces nitrogen oxides in exhaust gas discharged from a coal-fired boiler, and a duct that guides the exhaust gas from the coal-fired boiler to the denitration device, the duct having a horizontal duct connected to an exhaust gas outlet of the boiler, a vertical duct connected to the horizontal duct, and a hopper provided below a connection between the horizontal duct and the vertical duct, wherein an impact plate is provided at an upper opening of the hopper to impact ash particles in the exhaust gas and cause them to fall into the hopper. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2013-169495 A [Patent Document 2] WO 2006 / 073083 A1 [Patent Document 3] Japanese Patent Application Laid-Open No. 60-57117 [Patent Document 4] JP 2010-46579 A [Patent Document 5] JP 2010-54083 A [Patent Document 6] CN 109731462A [Patent Document 7] JP 2019-147142 A [Patent Document 8] JP 2016-198701 A Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to provide a method for producing a gas containing highly adhesive dust, which is suitable for cement plants and the like. Denitrification equipment And cement kiln exhaust gas treatment equipment The purpose of this project is to provide [Means for solving the problem]

[0014] The present invention includes the following aspects.

[0015] [1] Having an inlet duct, a denitrification reactor, and an outlet duct; The exhaust gas from the kiln or furnace can be passed through the inlet duct, the denitrification reactor, and the outlet duct in that order; The denitration reactor has a flow path through which exhaust gas flows in a substantially vertical direction at a linear velocity of 5 to 8 m / sec, and a screen plate and a fixed bed containing a denitration catalyst are provided in this order along the flow direction within the flow path, and the fixed bed has an opening of 7 mm or more; The inlet duct has a flow path on the inlet side through which the exhaust gas flows upward and a flow path on the outlet side through which the exhaust gas flows downward, The cross-sectional area of ​​the upward flow channel narrows along the flow direction, and the cross-sectional area of ​​the downward flow channel expands along the flow direction, A hopper is provided at the bottom of the upward flow path, and a weir is provided around the edge of the hopper on the side closer to the downward flow path; and A soot blower is provided at the inlet duct and / or the denitrification reactor at a location where dust is likely to accumulate. Denitration equipment.

[0016] [2] A dust collector for collecting dust in exhaust gas from a cement kiln; A denitrification apparatus according to [1] for removing nitrogen oxides from exhaust gas from a cement kiln. Equipped with A cement kiln exhaust gas treatment device capable of causing exhaust gas from a cement kiln to flow into a dust collector and a denitrification device in that order. [3] A denitrification apparatus according to [1] for removing nitrogen oxides from a cement kiln exhaust gas; A dust collector for collecting dust in exhaust gas from a cement kiln. Equipped with A cement kiln exhaust gas treatment device capable of causing exhaust gas from a cement kiln to flow through a denitrification device and a dust collector in that order. [4] The cement kiln exhaust gas treatment device according to [2] or [3], further comprising a heat recovery boiler for recovering heat from the exhaust gas on the downstream side of the denitrification device. Effect of the Invention

[0017] The denitration apparatus and cement kiln exhaust gas treatment device of the present invention can be operated at a high operating rate because there is almost no clogging of the exhaust gas flow path due to the accumulation of highly adhesive dust, etc. The denitration apparatus and cement kiln exhaust gas treatment device of the present invention are easy to maintain and have low running costs. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing an example of a cement kiln exhaust gas treatment device of the present invention. [Diagram 2] 1 is a diagram showing an example of a denitration device of the present invention. [Diagram 3] FIG. 2 is a diagram showing another example of a denitration device of the present invention. [Figure 4] FIG. 2 is a diagram showing another example of a denitration device of the present invention. [Diagram 5] FIG. 5 is a diagram showing the arrangement of a soot blower above the fixed bed of the denitration apparatus shown in FIG. [Figure 6] FIG. 2 is a diagram showing another example of a denitration device of the present invention. [Figure 7] FIG. 7 is a diagram showing the arrangement of a soot blower above the fixed bed of the denitration apparatus shown in FIG. 6. [Figure 8] FIG. 11 is a diagram showing another example of the arrangement of a soot blower above a fixed bed of a denitration device. [Figure 9] FIG. 11 is a diagram showing another example of the arrangement of a soot blower above a fixed bed of a denitration device. [Figure 10] FIG. 2 is a diagram showing another example of the cement kiln exhaust gas treatment device of the present invention. [Figure 11] FIG. 2 is a diagram showing another example of the cement kiln exhaust gas treatment device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings. It should be noted that the scope of the present invention is not limited to the following embodiments.

[0020] The denitration device of the present invention has an inlet duct 2, a denitration reactor 1, and an outlet duct 3, and exhaust gas G from a kiln or furnace can be made to flow through the inlet duct, the denitration reactor, and the outlet duct in that order. The inlet duct, the denitration reactor, and the outlet duct may have a flow passage cross-sectional shape as viewed from the gas flow direction that is rectangular, trapezoidal, circular, elliptical, etc. Among these, a rectangular shape is preferred from the viewpoint of ease of processing.

[0021] The inlet duct 2 has a flow path for the exhaust gas to flow upward on the inlet side, and a flow path for the exhaust gas to flow downward on the outlet side. There is a flow path that actually flows horizontally between the upward flow path and the downward flow path, but the walls that form the horizontal flow path may be an upward wall that forms the upward flow path and a downward wall that forms the downward flow path that are directly connected as shown in Figure 2, or a horizontal wall may be connected between the upward wall and the downward wall as shown in Figure 3. The outlet of the inlet duct 2 is connected to the inlet of the denitrification reactor 1.

[0022] The cross-sectional area of ​​the flow path between the upward flow path and the downward flow path is smaller than the cross-sectional area of ​​the upward flow path. It is more preferable that the cross-sectional area of ​​the flow path between the upward flow path and the downward flow path is smaller than the cross-sectional area of ​​the downward flow path. For example, the cross-sectional area of ​​the upward flow path may be narrowed along the flow direction, and the cross-sectional area of ​​the downward flow path may be widened along the flow direction. As a result, the linear flow velocity is increased in the flow path between the upward flow path and the downward flow path, and the settling of dust can be suppressed.

[0023] A hopper 16 is provided at the bottom of the upward flow passage. The hopper 16 widens the cross-sectional area of ​​the upward flow passage and reduces the linear flow velocity of the exhaust gas, making it easier for the dust to settle in the hopper. In addition, a weir 15 is provided around the edge of the hopper on the side closer to the downward flow passage. This weir 15 creates a vortex in the exhaust gas flow, making it easier for the dust to fall into the hopper, and also prevents dust that has not been removed by the hopper from overflowing into the downward flow passage.

[0024] If necessary, there may be a horizontal flow passage before the upward flow passage, which serves to introduce exhaust gas from a cement kiln, boiler, etc., into the upward flow passage.

[0025] The denitration reactor 1 has a flow path through which the exhaust gas flows in a substantially vertical direction. In the denitration reactor, the cross-sectional area of ​​the flow path is set so that the exhaust gas flows at a linear velocity of 4 to 8 m / sec. The outlet of the denitration reactor is usually connected to the inlet of an outlet duct.

[0026] A screen plate 13 and a fixed bed 12 containing a denitration catalyst are provided in this order along the flow direction within the flow path of the denitration reactor.

[0027] The screen plate 13 is usually provided on the inlet side of the denitration reactor. A structure for supporting the screen plate, such as a beam that is stretched across the inside of the denitration reactor, can be installed on the inlet side of the denitration reactor. The screen plate is supported within the denitration reactor by the screen plate support structure.

[0028] The screen plate preferably comprises a plurality of blades. The blades are usually arranged so that their main surfaces are parallel to each other. In order to fix such an arrangement of the blades, wires or plates (cross members) may be joined to each blade along a direction perpendicular to the main surface of each blade to form a lattice. Also, outer frame members (end members) may be provided on both ends of the blades. The screen plate is preferably installed on the inlet side of the flow passage of the denitration reactor so that the longitudinal direction of the blades is substantially perpendicular to the horizontal gas flow direction in the inlet duct over the entire cross section of the flow passage.

[0029] The fixed catalyst bed 12 is usually provided at the outlet side of the denitration reactor. A structure supporting the fixed catalyst bed, such as a beam that is stretched across the denitration reactor, can be provided at the outlet side of the denitration reactor. The fixed catalyst bed is supported within the denitration reactor by the fixed catalyst bed support structure. Although only a single stage of fixed catalyst bed is provided in FIG. 2, multiple stages of fixed catalyst beds may be provided if necessary.

[0030] The fixed bed installed in the denitration reactor is loaded with a catalyst body having a shape such as a lattice, corrugated, honeycomb, or plate. The catalyst body contains an active component of the denitration catalyst. Examples of the active component of the denitration catalyst include those containing oxides of titanium, oxides of molybdenum and / or tungsten, and oxides of vanadium (titanium-based catalysts); those containing mainly aluminosilicates such as zeolite carrying metals such as Cu and Fe (zeolite-based catalysts); and those containing a mixture of titanium-based catalysts and zeolite-based catalysts.

[0031] The fixed bed has an opening of 7 mm or more, preferably 10 mm or more. The upper limit of the opening is preferably 20 mm. In a catalyst body having a lattice, corrugated or honeycomb shape, the opening is the size of the openings, and in a catalyst body having a plate shape, the opening is the size of the gap between the plates.

[0032] A soot blower 14 is provided in the inlet duct and / or at a location in the denitration reactor where dust is likely to accumulate. A soot blower blows off attached dust by spraying an injection medium. Examples of the injection medium that can be used include water, steam, and compressed air (or pressure waves). A nozzle is attached to a tube called a lance, and the injection medium is ejected from the nozzle. Depending on the operation of the lance, it may be called a reciprocating soot blower, a fixed soot blower, a long-slot soot blower, or a rotary soot blower. The length and shape of the lance and the number of nozzles can be set appropriately depending on the size of the flow path in the inlet duct and / or the denitrification reactor.

[0033] One possible location for installing a soot blower is the passage between the upward flow passage and the downward flow passage of the inlet duct. Since an injection device for ammonia, urea, or other denitrification agent may be provided here, an injection device integrated with the soot blower may be installed (see, for example, Patent Documents 4 and 5).

[0034] Another possible location for the soot blower is the gas inlet side of a screen plate or fixed bed in a denitration reactor. Dust is likely to adhere to the gas inlet side of the screen plate or fixed bed. The soot blower can be arranged in the denitration reactor, for example, as shown in Figures 5, 7, 8 or 9. It is preferable to arrange lances or nozzles at a high density in a location where dust is likely to accumulate (specifically, near a wall, horizontal part, etc.). It is also preferable to install the soot blower so that the longitudinal direction of the lance is substantially perpendicular to the horizontal gas flow direction in the inlet duct, as shown in Figure 7. Furthermore, a sonic horn 17 can be used in combination, as shown in Figure 9.

[0035] In the denitration apparatus of the present invention, dust can be effectively removed from the exhaust gas by the hopper, the weir, and the soot blower provided in the inlet duct. In the denitration apparatus of the present invention, dust is less likely to accumulate on the screen plate and the fixed bed provided in the denitration reactor. As a result, the decrease in the denitration rate due to the accumulation of dust can be suppressed.

[0036] The cement kiln exhaust gas treatment device of the present invention comprises a dust collector 5 and a denitration device. The dust collector 5 may be provided upstream of the denitration device as shown in Fig. 1, or may be provided downstream of the denitration device as shown in Fig. 11. The dust collector that can be provided downstream of the denitration device can be an electric dust collector for low-temperature gas. An electric dust collector for low-temperature gas has lower installation costs than an electric dust collector for high-temperature gas.

[0037] It is also preferable that the cement kiln exhaust gas treatment device of the present invention further comprises a heat recovery boiler. The heat recovery boiler 18 may be provided upstream of the denitration device, or downstream of the denitration device as shown in Fig. 11. The heat recovery boiler 18 and the dust collector 5 may be arranged in the order shown in Fig. 11, or in the reverse order. The heat recovery boiler allows heat to be used effectively. The steam generated in the boiler can also be used as an injection medium for a soot blower. [Explanation of symbols]

[0038] 1:Denitrification reactor 2: Inlet duct 3: Exit duct 4: Denitration agent addition device 5: Dust collector 6: Cement raw materials 7: Calcination furnace 8: Cement kiln 9: Clinker cooler 10: Chimney 11: Preheater 12:Catalyst fixed bed 13: Screen plate 14: Soot Blower 15: Weir 16: Hopper 17: Sonic Horn 18: Waste heat recovery boiler G: Exhaust gas

Claims

1. An inlet duct, a denitration reactor, and an outlet duct; The exhaust gas from the furnace can be passed through the inlet duct, the denitrification reactor, and the outlet duct in that order. the denitration reactor has a flow path through which exhaust gas flows in a substantially vertical direction at a linear velocity of 5 to 8 m / sec, a screen plate and a fixed bed containing a denitration catalyst are provided in this order along the flow direction within the flow path, and the fixed bed has an opening of 7 mm or more; The inlet duct has a flow path on the inlet side through which the exhaust gas flows upward, and has a flow path on the outlet side through which the exhaust gas flows downward, the cross-sectional area of ​​the upward flow path narrows along the flow direction, and the cross-sectional area of ​​the downward flow path expands along the flow direction, a hopper is provided below the upward flow path, and a weir is provided around the edge of the hopper on the side closer to the downward flow path, and A soot blower is provided at the inlet duct and / or the denitrification reactor at a location where dust is likely to accumulate. Denitration equipment.

2. A dust collector for collecting dust in the cement kiln exhaust gas; A denitrification apparatus according to claim 1 for removing nitrogen oxides from exhaust gas from a cement kiln; Equipped with A cement kiln exhaust gas treatment device capable of causing exhaust gas from a cement kiln to flow into a dust collector and a denitrification device in that order.

3. A denitrification apparatus according to claim 1 for removing nitrogen oxides from a cement kiln exhaust gas; A dust collector for collecting dust in exhaust gas from a cement kiln. Equipped with A cement kiln exhaust gas treatment device capable of causing exhaust gas from a cement kiln to flow through a denitrification device and a dust collector in that order.

4. 4. The cement kiln exhaust gas treatment device according to claim 2, further comprising a heat recovery boiler for recovering heat from the exhaust gas on the downstream side of the denitrification device.

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