JP7603385B2 - Denitrification equipment and cement kiln exhaust gas treatment equipment - Google Patents

Description

The present invention relates to a denitration device and a cement kiln exhaust gas treatment device . More specifically, the present invention relates to a denitration device and a cement kiln exhaust gas treatment device suitable for cement plants and the like that discharge gas containing highly adhesive dust.

Gas discharged from a cement kiln contains acid gases such as hydrogen chloride, _SOx , and _NOx . Therefore, in order to reduce the _NOx concentration in the exhaust gas, denitrification of the exhaust gas is carried out by adding a denitrification agent such as ammonia or urea. This method involves decomposing _NOx (NO and _NO2 ) into nitrogen ( _N2 ) and water ( _H2O ) using the denitrification agent.

For example, Patent Document 1 discloses a cement kiln exhaust gas treatment device that is characterized by including a dust collector that collects dust in the exhaust gas from the cement kiln, a gas addition device that adds 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.

Patent Document 2 discloses a cement kiln exhaust gas treatment device that is characterized by comprising a dust collector that collects dust in the cement kiln exhaust gas, a catalyst poisoning substance removal device that removes catalyst poisoning substances from the cement kiln exhaust gas that has passed through the dust collector, a preheating device that preheats the cement kiln exhaust gas that has passed through the catalyst poisoning substance removal device, and a catalytic device that removes 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.

After passing through the dust collector, a fair amount of dust remains in the exhaust gas, which can accumulate in the denitrification equipment. Various technologies have been proposed to deal with this problem.

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 to penetrate the flue in areas where the flow in the flue from the boiler outlet to the chimney is likely to stagnate or where the flow speed is slow and ash is likely to accumulate, and a mechanism is provided to manually or automatically rotate the nozzle to change the air injection direction, thereby scattering the ash.

Patent Document 4 discloses a flue gas denitration device in which a catalytic reactor equipped with a catalyst that removes nitrogen oxides in exhaust gas in the presence of ammonia is placed in the inlet flue of the exhaust gas, and multiple ammonia water injection nozzles are placed in the inlet flue region where exhaust gas flows horizontally upstream of the catalytic reactor, and the device 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 nozzle.

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

Patent Document 6 discloses a flue gas nitrogen oxide treatment system that has an inlet at the top end of a reactor, an exhaust port at the bottom end of the reactor, and an ash receiving tank between the catalyst layer and the inlet, an ash receiving passage with one end connected to the ash receiving tank, the other end of the ash receiving passage connected to 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.

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, and is characterized in that it has 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 communicating with the exhaust gas outlet of the coal-fired boiler, the rear end of the horizontal duct communicating with the lower end of the vertical duct, a duct that defines an internal space in the duct through which the exhaust gas discharged from the coal-fired boiler flows from the horizontal duct to the upper part of the vertical duct and is guided to the denitration device, a hopper provided below the vertical duct and communicating with the internal space in the duct through the upper end opening of the hopper, and an inclined collision plate that extends upward continuously from the rear end edge of the upper end opening of the hopper and is fixed to the rear surface of the duct that defines the rear of the internal space in the duct, and extends from the rear surface at an angle downward toward the front.

Patent Document 8 discloses an exhaust gas treatment device that includes 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 the exhaust gas outlet of the boiler, a vertical duct connected to the horizontal duct, and a hopper provided below the connection between the horizontal duct and the vertical duct, and that is characterized in that a collision plate is provided at the upper opening of the hopper to collide ash particles in the exhaust gas and cause them to fall into the hopper.

JP 2013-169495 A WO 2006/073083 A1 Japanese Unexamined Patent Publication No. 60-57117 JP 2010-46579 A JP 2010-54083 A CN 109731462A JP 2019-147142 A JP 2016-198701 A

An object of the present invention is to provide a denitration device and a cement kiln exhaust gas treatment device suitable for cement plants and the like which discharge gas containing highly adhesive dust.

The present invention includes the following aspects:

[1] Having an inlet duct, a denitration 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, 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 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 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 a location in the inlet duct and/or the denitrification reactor where dust is likely to accumulate.
Denitrification equipment.

[2] A dust collector for collecting dust in cement kiln exhaust gas;
The denitrification apparatus according to [1] for removing nitrogen oxides from a cement kiln exhaust gas is provided.
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;
and a dust collector for collecting dust in the cement kiln exhaust gas.
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.

The denitration device 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. The denitration device and cement kiln exhaust gas treatment device of the present invention are easy to maintain and have low running costs.

FIG. 1 is a diagram showing an example of a cement kiln exhaust gas treatment device of the present invention. 1 is a diagram showing an example of a denitration device of the present invention. FIG. 2 is a diagram showing another example of a denitration device of the present invention. FIG. 2 is a diagram showing another example of a denitration device of the present invention. FIG. 5 is a diagram showing the arrangement of a soot blower above the fixed bed of the denitration apparatus shown in FIG. 4. FIG. 2 is a diagram showing another example of a denitration device of the present invention. FIG. 7 is a diagram showing the arrangement of a soot blower above the fixed bed of the denitration apparatus shown in FIG. 6 . FIG. 11 is a diagram showing another example of the arrangement of a soot blower above a fixed bed of a denitration device. FIG. 11 is a diagram showing another example of the arrangement of a soot blower above a fixed bed of a denitration device. FIG. 2 is a diagram showing another example of the cement kiln exhaust gas treatment device of the present invention. FIG. 2 is a diagram showing another example of the cement kiln exhaust gas treatment device of the present invention.

The embodiments of the present invention will be described in detail with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiments.

The denitration apparatus 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.

The inlet duct 2 has a flow path on the inlet side through which exhaust gas flows upward, and a flow path on the outlet side through which exhaust gas flows downward. Between the upward flow path and the downward flow path, there is in fact a horizontal flow path, but the walls constituting the horizontal flow path may be directly connected between the upward wall constituting the upward flow path and the downward wall constituting the downward flow path as shown in Figure 2, or may be connected to a horizontal wall 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.

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.

A hopper 16 is provided at the bottom of the upward flow path. The hopper 16 increases the cross-sectional area of the upward flow path and reduces the linear flow velocity of the exhaust gas, making it easier for 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 path. This weir 15 creates a vortex in the exhaust gas flow, making it easier for dust to fall into the hopper, and also prevents dust that is not removed by the hopper from overflowing onto the downward flow path.

If necessary, there may be a horizontal flow passage before the upward flow passage. The horizontal flow passage before the upward flow passage is for directing exhaust gas from a cement kiln, boiler, etc. into the upward flow passage.

The denitration reactor 1 has a flow passage through which the exhaust gas flows in a substantially vertical direction. The cross-sectional area of the flow passage 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.

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

The screen plate 13 is usually provided on the inlet side of the denitration reactor. A structure to support 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.

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.

The fixed catalyst bed 12 is usually provided on the outlet side of the denitration reactor. A structure supporting the fixed catalyst bed, such as a beam that is placed inside the denitration reactor, can be provided on the outlet side of the denitration reactor. The fixed catalyst bed is supported inside 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.

The fixed bed installed in the denitration reactor is loaded with a catalyst body in the shape of a lattice, corrugated, honeycomb, plate, etc. The catalyst body contains the 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 zeolites carrying metals such as Cu and Fe (zeolite-based catalysts); and those made by mixing titanium-based catalysts and zeolite-based catalysts.

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.

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.

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. An injection device for ammonia, urea, or other denitrification agent may be installed here, so an integrated injection device and soot blower may be installed (see, for example, Patent Documents 4 and 5).

Another possible location for the soot blower is the gas inlet side of the screen plate or fixed bed in the denitration reactor. Dust is likely to adhere to the gas inlet side of the screen plate or fixed bed. The soot blower can be placed in the denitration reactor, for example, as shown in Figures 5, 7, 8, or 9. It is preferable to place the lances or nozzles at a high density in places where dust is likely to accumulate (specifically, near walls, horizontal parts, etc.). It is also preferable to install the soot blower so that the length 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.

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

The cement kiln exhaust gas treatment device of the present invention is equipped with 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 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.

The cement kiln exhaust gas treatment device of the present invention preferably 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.

1: Denitrification reactor
2: Inlet duct
3: Exit duct
4: Denitrification 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: Sootblower
15: Weir
16: Hopper
17: Sonic Horn
18: Waste heat recovery boiler
G: Exhaust gas

Claims (4)

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 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 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 a location in the inlet duct and/or the denitrification reactor where dust is likely to accumulate.
Denitrification equipment. A dust collector for collecting dust in the cement kiln exhaust gas;
and a denitrification apparatus according to claim 1 for removing nitrogen oxides from exhaust gas from a cement kiln.
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. A denitrification apparatus according to claim 1 for removing nitrogen oxides from a cement kiln exhaust gas;
and a dust collector for collecting dust in the cement kiln exhaust gas.
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. The cement kiln exhaust gas treatment device according to claim 2 or 3, further comprising a heat recovery boiler for recovering heat from the exhaust gas downstream of the denitrification device.

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