JP2022012043A - Denitration device - Google Patents

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

The present invention relates to a denitration device. More specifically, the present invention relates to a denitration device suitable for a cement plant or the like that discharges a gas containing highly adhesive dust.

The gas discharged from the cement kiln contains acid gases such as hydrogen chloride, SO _x , and NO _x . Therefore, in order to reduce the NO _x concentration in the exhaust gas, a denitration agent such as ammonia or urea is added to denitrate the exhaust gas. It decomposes NO _x (NO and NO ₂ ) into nitrogen (N ₂ ) and water (H ₂ O) by a denitration agent.

For example, Patent Document 1 describes a dust collector that collects dust in the exhaust gas of a cement kiln, and a gas containing ammonia discharged from a fermentation treatment device in the exhaust gas after the dust is collected by the dust collector. Discloses a cement kiln exhaust gas treatment device comprising a gas adding device for adding a gas, and a catalyst device for denitration of the exhaust gas after the gas containing ammonia is added by the gas adding device.

Patent Document 2 describes a dust collector that collects dust in cement kiln exhaust gas, a catalyst poisoning substance removing device that removes a catalyst poisoning substance from the cement kiln exhaust gas that has passed through the dust collecting device, and the catalyst poisoning device. A preheating device that preheats the cement kiln exhaust gas that has passed through the substance removal device, and nitrogen oxides, volatile organic compounds, carbon monoxide, residual organic pollutants, hydrocarbons and odors in the cement kiln exhaust gas preheated by the preheating device. Disclosed is a cement kiln exhaust gas treatment apparatus comprising a catalyst apparatus for removing one or more selected from substances.

Not a little dust remains in the exhaust gas after passing through the dust collector, and it may be deposited on the denitration device. Various techniques have been proposed as countermeasures.

For example, Patent Document 3 describes, in a boiler containing a large amount of ash in the exhaust gas such as a coal-fired boiler or a cement kiln exhaust gas boiler, a portion where the flow of the flue from the boiler outlet to the chimney is likely to stagnate or a portion where the flow velocity is slow. An ash scattering nozzle is attached to a place where ash is likely to accumulate by penetrating the chimney, and a mechanism is provided to rotate the nozzle manually or automatically to change the direction of air injection to disperse the ash. The ash scattering nozzle structure characterized by the above is disclosed.

In Patent Document 4, a catalytic reactor provided with a catalyst for removing nitrogen oxides in the exhaust gas in the presence of ammonia is arranged in the inlet flue of the exhaust gas, and the exhaust gas flows in the horizontal direction on the upstream side of the catalytic reactor. In the flue gas denitration device in which a plurality of ammonia water injection nozzles are arranged in the inlet flue region, the flue gas denitration is characterized by installing a soot blower on the lower wall surface of the horizontal flue region in the wake portion of the ammonia water injection nozzle. The device is disclosed.

Patent Document 5 describes an ammonia injection pipe inserted from above the exhaust gas duct into an exhaust gas duct extending in the lateral direction, an ammonia water injection nozzle provided in the ammonia injection pipe to spray ammonia water, and the ammonia. It is a denitration device having a denitration catalyst layer provided in the wake in the flow direction of the exhaust gas of the injection pipe, and has a gas injection means for injecting gas toward the bottom surface of the exhaust gas duct below the ammonia injection pipe. The featured denitration device is disclosed.

Patent Document 6 is provided with an inlet at the upper end of the reactor, an exhaust port at the lower end of the reactor, and an ash receiving tank provided between the catalyst layer and the inlet, and one end of the ash communicates with the ash receiving tank. A receiving passage is provided, the other end of the ash receiving passage communicates with the exhaust port, a flap and an ash discharge port are provided in the middle of the ash receiving passage, and a compressed air nozzle is arranged in the catalyst layer. Discloses the flue gas nitrogen oxide treatment system.

Further, Patent Document 7 is an exhaust gas treatment device for reducing nitrogen oxides in exhaust gas discharged from a coal-fired boiler by a denitration device, and includes a horizontal duct extending in a substantially horizontal direction and a vertical duct extending in a substantially vertical direction. The front end of the horizontal duct communicates with the exhaust gas outlet of the coal-fired boiler, the rear end of the horizontal duct communicates with the lower end of the vertical duct, and the exhaust gas discharged from the coal-fired boiler is discharged from the horizontal duct. A duct that partitions the space inside the duct that flows above the vertical duct and leads to the denitration device, a hopper that is provided below the vertical duct and communicates with the space inside the duct via the opening at the upper end of the hopper, and the hopper. It is provided with an inclined collision plate that extends continuously upward from the rear end edge of the upper end opening, is fixed to the rear surface of the duct that partitions the rear of the duct inner space, and extends forward and downward from the rear surface. The characteristic exhaust gas treatment device is disclosed.

Patent Document 8 includes a denitration device provided with a denitration catalyst for reducing nitrogen oxides in exhaust gas discharged from a coal-fired boiler, and the denitration device provided with a duct for guiding the exhaust gas from the coal-fired boiler. The duct has a horizontal duct connected to the exhaust gas outlet of the boiler, a vertical duct connected to the horizontal duct, and a hopper provided below the connection portion between the horizontal duct and the vertical duct. Disclosed in the exhaust gas treatment device, the exhaust gas treatment device is provided with a collision plate at the upper end opening of the hopper, which causes ash particles in the exhaust gas to collide with each other and drop into the hopper.

Japanese Unexamined Patent Publication No. 2013-169495 WO 2006/073083 A1 Japanese Unexamined Patent Publication No. 60-5717 Japanese Unexamined Patent Publication No. 2010-46579 Japanese Unexamined Patent Publication No. 2010-54083 CN 109731462 A Japanese Unexamined Patent Publication No. 2019-147142 Japanese Unexamined Patent Publication No. 2016-198701

An object of the present invention is to provide a denitration device suitable for a cement plant or the like that discharges a gas containing highly adhesive dust.

The present invention includes the following aspects.

[1] It has an inlet duct, a denitration reactor and an outlet duct.
Exhaust gas from the kiln furnace can flow through the inlet duct, denitration reactor and outlet duct in this order.
The denitration reactor has a flow path in 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 arranged in this flow path in this order along the flow direction. And the fixed floor has an opening of 7 mm or more.
The inlet duct has a flow path in which the exhaust gas flows upward on the inlet side, a flow path in which the exhaust gas flows downward on the outlet side, and a cross section of the flow path between the flow path flowing upward and the flow path flowing downward. The area of the flow path is smaller than the area of the cross section of the flow path that flows upward, a hopper is provided at the bottom of the flow path that flows upward, and a weir is provided near the edge of the hopper near the flow path that flows downward. And, a soot blower is provided at the place where dust is likely to accumulate in the inlet duct and / or the denitration reactor.
Denitration device.

[2] A dust collector for collecting dust in cement kiln exhaust gas,
It is equipped with the denitration device according to [1] for removing nitrogen oxides in cement kiln exhaust gas.
A cement kiln exhaust gas treatment device that can flow exhaust gas from a cement kiln to a dust collector and a denitration device in this order.
[3] The denitration device according to [1] for removing nitrogen oxides in cement kiln exhaust gas, and
Equipped with a dust collector for collecting dust in cement kiln exhaust gas,
A cement kiln exhaust gas treatment device that can flow exhaust gas from a cement kiln to a denitration device and a dust collector in this order.
[4] The cement kiln exhaust gas treatment device according to [2] or [3], further provided with an exhaust heat recovery boiler for recovering the heat of the exhaust gas on the wake side of the denitration device.

The denitration device and the cement kiln exhaust gas treatment device of the present invention can be operated at a high operating rate because highly adhesive dust hardly clogs the flow path of the exhaust gas. The denitration device and the cement kiln exhaust gas treatment device of the present invention are easy to maintain and have a low running cost.

It is a figure which shows an example of the cement kiln exhaust gas treatment apparatus of this invention. It is a figure which shows an example of the denitration apparatus of this invention. It is a figure which shows another example of the denitration apparatus of this invention. It is a figure which shows another example of the denitration apparatus of this invention. It is a figure which shows the arrangement of the soot blower above the fixed floor of the denitration device shown in FIG. It is a figure which shows another example of the denitration apparatus of this invention. It is a figure which shows the arrangement of the soot blower above the fixed floor of the denitration device shown in FIG. It is a figure which shows another example of the arrangement of the soot blower above the fixed floor of a denitration device. It is a figure which shows another example of the arrangement of the soot blower above the fixed floor of a denitration device. It is a figure which shows another example of the cement kiln exhaust gas treatment apparatus of this invention. It is a figure which shows another example of the cement kiln exhaust gas treatment apparatus of this invention.

Embodiments of the present invention will be specifically described with reference to the drawings. The scope of the present invention is not limited by the following embodiments.

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 (kiln kiln or furnace furnace) is applied to the inlet duct, the denitration reactor, and the outlet duct in this order. Can be shed.
The inlet duct, denitration reactor, and outlet duct may have a rectangular, trapezoidal, circular, or elliptical shape in cross section of the flow path when viewed from the gas flow direction. Of these, a rectangle is preferable in terms of ease of processing.

The inlet duct 2 has a flow path in which the exhaust gas flows upward on the inlet side, and has a flow path in which the exhaust gas flows downward on the outlet side. There is a flow path that flows horizontally between the flow path that flows upward and the flow path that flows downward, but the wall that constitutes the flow path that flows horizontally is a flow that flows upward as shown in FIG. The upward wall that constitutes the road and the downward wall that constitutes the downward flow path may be directly connected, or as shown in FIG. 3, between the upward wall and the downward wall. It may be a series of horizontal walls. The outlet of the inlet duct 2 is connected to the inlet of the denitration reactor 1.

The area of the cross section of the flow path between the flow path flowing upward and the flow path flowing downward is smaller than the area of the cross section of the flow path flowing upward. It is more preferable that the area of the cross section of the flow path between the flow path flowing upward and the flow path flowing downward is smaller than the area of the cross section of the flow path flowing downward. For example, the area of the flow path cross section of the upward flowing flow path may be narrowed along the flow direction, and the area of the flow path cross section of the downward flowing flow path may be expanded along the flow direction. As a result, the linear flow velocity increases in the flow path between the flow path flowing upward and the flow path flowing downward, and the sedimentation of dust can be suppressed.

A hopper 16 is provided at the bottom of the flow path that flows upward. The hopper 16 increases the area of the cross section of the flow path that flows upward, and lowers the linear flow velocity of the exhaust gas, so that dust tends to settle in the hopper. Further, a weir 15 is provided near the edge of the hopper on the side close to the flow path flowing downward. This weir 15 causes a vortex in the flow of the exhaust gas to make it easier for dust to fall on the hopper, and it is possible to prevent dust that could not be removed by the hopper from overflowing to the side of the flow path that flows downward.

If necessary, there may be an additional flow path that flows horizontally in front of the flow path that flows upward. The horizontally flowing flow path in front of the upward flowing flow path is for guiding the exhaust gas from the cement kiln, boiler, etc. into the upward flowing flow path.

The denitration reactor 1 has a flow path through which the exhaust gas flows in a substantially vertical direction. In the denitration reactor, the area of the cross section 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 the outlet duct.

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

The screen plate 13 is usually provided on the inlet side of the denitration reactor. A structure supporting the screen plate, for example, a beam passed into the denitration reactor, can be installed on the inlet side of the denitration reactor. The screen plate is supported in the denitration reactor by the screen plate support structure.

The screen plate preferably comprises a plurality of feather plates. Multiple blades are usually arranged so that the main surfaces are parallel to each other. In order to fix such an arrangement of multiple wing plates, even if wire rods or plate materials (cross members) are joined to each wing plate in a direction orthogonal to the main surface of each wing plate to form a grid. good. Further, outer frame materials (end members) may be provided at both ends of the plurality of feather plates.
The screen plate is installed on the inlet side of the flow path of the denitration reactor so that the length of the wing plate is substantially orthogonal to the horizontal gas flow direction in the inlet duct over the entire flow path cross section. Is preferable.

The catalyst fixing bed 12 is usually provided on the outlet side of the denitration reactor. A structure that supports the catalyst fixing bed, for example, a beam passed into the denitration reactor, can be installed on the outlet side of the denitration reactor. The catalyst fixed bed is supported in the denitration reactor by the catalyst fixed bed support structure. Although the catalyst fixing bed is provided only in a single stage in FIG. 2, a plurality of stages may be provided if necessary.

The fixed bed provided in the denitration reactor is loaded with a catalyst body in the shape of a grid, a corrugate, a honeycomb, a plate, or the like. The catalyst contains the active ingredient of the denitration catalyst. The active component of the denitration catalyst is one containing an oxide of titanium, an oxide of molybdenum and / or tungsten, and an oxide of vanadium (titanium-based catalyst); a zeolite on which a metal such as Cu or Fe is supported. Those mainly containing aluminosilicate such as (zeolite-based catalyst); those formed by mixing a titanium-based catalyst and a zeolite-based catalyst can be mentioned.

The fixed floor has an opening of 7 mm or more, preferably 10 mm or more. The upper limit of the opening is preferably 20 mm. The mesh size is the size of those eyes in a lattice-shaped, corrugated, or honeycomb-shaped catalyst body, and the size of the gap between the plates in a plate-shaped catalyst body. That's right.

A soot blower 14 is provided at an inlet duct and / or a denitration reactor where dust is likely to accumulate.
The soot blower blows off the adhering dust by spraying an injection medium. As the injection medium, for example, water, water vapor, compressed air (or pressure wave) or the like is used. A nozzle is installed in 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 stationary soot blower, a long pull-out type soot blower, a rotary soot blower, or the like. The length and shape of the lance and the number of nozzles can be appropriately set depending on the size of the flow path in the inlet duct and / or the denitration reactor.

As one of the installation locations of the soot blower, there may be a flow path between the flow path flowing upward and the flow path flowing downward in the inlet duct. Since an injection device for a denitration agent such as ammonia or urea may be provided here, an injection device integrated with a soot blower may be installed (see, for example, Patent Documents 4 and 5).

Another place to install the soot blower is the gas inflow side of the screen plate or fixed floor in the denitration reactor. Dust tends to adhere to the gas inflow side of the screen plate or fixed floor. The soot blower can be placed in the denitration reactor, for example, as shown in FIGS. 5, 7, 8 or 9. It is preferable to arrange the lance or the nozzle at a high density in a place where dust is likely to accumulate (specifically, near a wall, a horizontal portion, etc.). Further, as shown in FIG. 7, it is preferable to install the soot blower so that the length of the lance is substantially orthogonal to the horizontal gas flow direction in the inlet duct. Further, as shown in FIG. 9, the sonic horn 17 can also be used in combination.

In the denitration device 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 device of the present invention, dust is unlikely to accumulate on the screen plate and the fixed floor provided in the denitration reactor. As a result, it is possible to suppress a decrease in the denitration rate due to the accumulation of dust.

The cement kiln exhaust gas treatment device of the present invention includes a dust collector 5 and a denitration device. The dust collector 5 may be provided on the front flow side of the denitration device as shown in FIG. 1, or may be provided on the wake side of the denitration device as shown in FIG. The dust collector that can be provided on the wake side of the denitration device can be an electric dust collector for low temperature gas. The equipment cost of the electrostatic precipitator for low-temperature gas is lower than that of the electrostatic precipitator for high-temperature gas.

Further, it is preferable that the cement kiln exhaust gas treatment apparatus of the present invention further includes an exhaust heat recovery boiler. The exhaust heat recovery boiler 18 may be provided on the front flow side of the denitration device, or may be provided on the wake side of the denitration device as shown in FIG. The exhaust heat recovery boiler 18 and the dust collector 5 may be arranged in the order shown in FIG. 11 or vice versa. The heat can be effectively used by the exhaust heat recovery boiler. The steam generated by the boiler can also be used as an injection medium for the soot blower.

1: Denitration reactor
2: Entrance duct
3: Exit duct
4: Denitration agent addition device
5: Dust collector
6: Cement raw material
7: Temporary firing furnace
8: Cement kiln
9: Clinker cooler
10: Chimney
11: Preheater
12: Catalyst fixed floor
13: Screen plate
14: Soot blower
15: Weir
16: Hopper
17: Sonic Horn
18: Exhaust heat recovery boiler
G: Exhaust gas

Claims (4)

It has an inlet duct, a denitration reactor and an outlet duct,
Exhaust gas from the kiln can flow through the inlet duct, denitration reactor and outlet duct in this order.
The denitration reactor has a flow path in 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 arranged in this flow path in this order along the flow direction. And the fixed floor has an opening of 7 mm or more.
The inlet duct has a flow path in which the exhaust gas flows upward on the inlet side, a flow path in which the exhaust gas flows downward on the outlet side, and a cross section of the flow path between the flow path flowing upward and the flow path flowing downward. The area of the flow path is smaller than the area of the cross section of the flow path that flows upward, a hopper is provided at the bottom of the flow path that flows upward, and a weir is provided near the edge of the hopper near the flow path that flows downward. And, a soot blower is provided at the place where dust is likely to accumulate in the inlet duct and / or the denitration reactor.
Denitration device. Cement kiln A dust collector for collecting dust in exhaust gas,
The denitration device according to claim 1 for removing nitrogen oxides in cement kiln exhaust gas is provided.
A cement kiln exhaust gas treatment device that can flow exhaust gas from a cement kiln to a dust collector and a denitration device in this order. The denitration device according to claim 1 for removing nitrogen oxides in cement kiln exhaust gas, and
Equipped with a dust collector for collecting dust in cement kiln exhaust gas,
A cement kiln exhaust gas treatment device that can flow exhaust gas from a cement kiln to a denitration device and a dust collector in this order. The cement kiln exhaust gas treatment device according to claim 2 or 3, further comprising an exhaust heat recovery boiler for recovering the heat of the exhaust gas on the wake side of the denitration device.

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