JPS5911330B2 - Dedusting method for fixed bed catalyst bed - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing dust from a fixed bed catalyst bed.

FIG. 1 is a sectional view showing a conventional fixed bed catalytic reactor.

In the figure, 1 is a reactor, 2 is a reactor inlet duct connected to the inlet of reactor 10, 3 is a reactor outlet duct connected to the outlet of reactor 1, 4 is a rostrum fixed to reactor 1, and 5 is a reactor inlet duct connected to the inlet of reactor 10. 6 is a catalyst support network laid on the rostol 4, and 6 is a catalyst layer provided on the support network 5.

In this fixed bed type catalytic reactor, gas to be treated sent from a duct 2 is reacted in a catalyst layer 6, and the reacted gas is discharged from a duct 3.

However, if the gas contains dust, part of the dust adheres and accumulates in the catalyst layer 6, and the pressure loss in the catalyst layer 6 increases over time.

One possible method for removing the soot and dust deposited in the catalyst layer 6 is to temporarily fluidize the catalyst layer 6.

However, when the catalyst layer 6 is fluidized, the catalyst particles are damaged and the catalyst particles move, and the catalyst layer 6 has parts where the layer thickness is large and parts where the layer is thin.
If fluidization is repeated, a blow-by phenomenon will eventually occur, and the gas will pass through the catalyst layer 6 untreated, making it impossible to reliably treat the gas.

This invention was made in order to solve the problem mentioned above, and it is an object of the present invention to provide a method for removing dust from a fixed bed type catalyst bed in which the catalyst particles are not damaged or moved. purpose.

In order to achieve this objective, in the present invention, the gas flow path to be treated is branched into two or more, and two or more fixed bed type catalyst beds are provided in parallel in the branched flow paths, and the flow path to the catalyst layer to be dedusted is The flow rate of the supplied gas is reduced compared to normal by a flow rate adjustment means (for example, a damper) provided in a branched gas flow path connected to the catalyst layer, and at the same time the flow rate of the supplied gas to other catalyst layers is fluidized by the catalyst layer. After the flow rate of the gas supplied to each catalyst layer is returned to the normal flow rate, the catalyst particles and soot in the catalyst layer to be dedusted are separated and dedusted.

FIG. 2 is a partially cutaway perspective view showing an apparatus for carrying out a method for removing dust from a fixed bed type catalyst layer of a dry denitrification apparatus according to an embodiment of the present invention.

In the figure, 1 is the inlet of the reactor 1, 8 is the outlet of the reactor 1,
9 and 10 are vertical gas barrier walls fixed to the reactor 1;
Reference numeral 1 denotes a horizontal gas barrier wall fixed to the reactor 1. The reactor 1 is divided into four small chambers by the barrier walls 9 to 11, and each small chamber is equipped with a rostol 4, a catalyst support network, and a catalyst layer 6. The catalyst layers 6 are provided so that the gas always passes through each catalyst layer 6 provided in parallel.

Further, 12 and 13 are damper frames provided at the outlet of the small chamber, 14 is a damper for adjusting the amount of gas rotatably supported by the reactor, and the damper 14 is provided on the gas outflow side of the catalyst layer 6.

15 is an air cylinder fixed to the reactor 1; 16 is a link mechanism connected to the piston front damper 14 of the cylinder 15;
is opened and closed.

Next, the operation will be explained.

The exhaust gas containing NOx and soot is uniformly mixed with NOx reducing gas before being introduced into the reactor 1.
It enters the reactor 1 through the inlet 7.

Here, the exhaust gas is divided almost equally into four small chambers and enters.

The exhaust gas that has entered each small chamber passes through the catalyst layer 6, NOx in the exhaust gas undergoes a denitrification reaction with the reducing gas, and the exhaust gas is denitrated and discharged from the outlet 8.

By the way, when soot and dust are contained in the exhaust gas, a part of the soot and dust adheres and accumulates in the catalyst layer 6, and the pressure loss of the catalyst layer 6 increases over time.

In this case, by operating the cylinder 15, the opening degree of the damper 14 is reduced, and the velocity of the exhaust gas passing through the catalyst layer 6 to be dedusted is set higher than normal to the extent that other catalyst layers 6 are not fluidized. will also decrease.

In other words, if the speed of the exhaust gas passing through the catalyst layer 6 to be dedusted is reduced, the speed of the exhaust gas passing through the other catalyst layers 6 increases accordingly, but the speed of the exhaust gas passing through the other catalyst layers 6 increases accordingly. The velocity of the exhaust gas passing through the catalyst layer 6 to be dedusted is decreased so that the velocity increases within a range that does not cause fluidization.

Then, the balance of forces between the catalyst particles in the catalyst layer 6 to be dedusted is disrupted, the catalyst particles and the soot dust are separated, and the soot dust is removed from the catalyst layer 6.
removed from

In other words, in the catalyst layer 6 in which catalyst particles are simply packed to a certain layer height, the voids between the catalyst particles are changes are unlikely to occur.

However, if the speed of the exhaust gas passing through the catalyst layer 6 is reduced, the above-mentioned force pushing up the catalyst becomes smaller and the balance with the catalyst's own weight is disrupted, causing the arrangement of the catalyst particles to change and the catalyst particles and soot to be separated. is separated, soot and dust are removed, and pressure loss is reduced.

This is supported by experiments. FIG. 3 is a diagram showing the results of the experiment.

In this experiment, boiler exhaust gas at about 350°C was passed through the catalyst layer at a normal speed of 1.7 m/s to deposit soot, and then three times the catalyst layer 6, which was installed in parallel, was passed through the catalyst layer. The speed of exhaust gas passing through the catalyst layer 6 to be dedusted is set to 1.2.
m/s for a short time.

The first deceleration operation was performed with soot dust deposited on the catalyst layer 6 to such an extent that the surface of the catalyst layer 6 may or may not cause a local blow-through phenomenon, in order to clarify the dust removal effect. Ta.

As a result, when the speed of the exhaust gas was returned to 1.7 m/s, the pressure loss in the catalyst layer 6 was reduced to 240 mmAq, which is almost the initial pressure loss of 205 mmAq, indicating the remarkable effect.

At the time of the second and third deceleration operations, there is less dust accumulated on the catalyst layer 6, so the reduction in pressure loss is small, but it is clear that it is effective, and the deceleration operations are performed periodically. This proves that if carried out, the amount of accumulated soot and dust can be reduced to a desired amount or less.

When the flow rate of exhaust gas is lowered than normal,
Unlike when the catalyst layer 6 is fluidized, the catalyst particles are not damaged and the catalyst particles do not move, so the thickness of the catalyst layer 6 does not change, even if the dust removal operation is repeated. However, the blow-by phenomenon does not occur, and the exhaust gas can be reliably treated.

Furthermore, by providing a plurality of catalyst layers 6 in multiple stages in the vertical direction, even if the amount of gas to be treated is large, the installation area of the device can be reduced, the device can be made compact, and the structure is simple. It has improved reliability, is suitable for large-scale production, has a large degree of structural freedom, is highly adaptable to existing and new plants, and is simple to operate and easy to automate. .

Furthermore, when the flow rate of exhaust gas is controlled on the gas inflow side of the catalyst layer 6, a drift of the exhaust gas occurs on the gas inflow side of the catalyst layer 6, and soot and dust locally adhere to the inlet surface of the catalyst layer 6. Since it becomes difficult for exhaust gas to pass through the affected areas, the exhaust gas passes only through areas where soot and dust do not adhere, so the speed at which the exhaust gas passes through the catalyst layer 6 increases, and fluidization of the catalyst layer 6 occurs locally. There is a risk that the catalyst in that area will scatter downstream with the exhaust gas, causing a blow-by phenomenon.In contrast, a damper 14 is provided on the gas outflow side of the catalyst layer 6 to reduce the flow velocity of the exhaust gas on the gas outflow side of the catalyst layer 6. If controlled, no drift of exhaust gas will occur on the gas inflow side of the catalyst layer 6, so there is no risk of a blow-through phenomenon occurring.

The shape of the inlet and outlet of the reactor 10 does not necessarily have to be a square hopper shape as shown in Figure 2, but an appropriate shape should be selected taking into consideration the arrangement of equipment connected before and after. Bye.

Furthermore, the space above and below the catalyst layer 6 can be appropriately selected in consideration of maintenance and the like, and depending on the space above and below, the damper 14 can have multiple stages of blades.

Furthermore, in the above-mentioned embodiment, when the speed of exhaust gas passing through the catalyst layer 6 to be dedusted was reduced, the opening degree of the damper of the other catalyst layer 6 was not changed; The velocity of the exhaust gas passing through the other catalyst layer 6 may be increased within a range where fluidization does not occur by increasing the opening degree of the damper and decreasing the flow path resistance.

As explained above, in the method for removing dust from a fixed bed catalyst bed according to the present invention, the soot and dust deposited on the catalyst bed can be effectively removed, so that stable operation is possible and catalyst particles The gas will not be damaged and the gas can be reliably processed.

As described above, the effects of this invention are remarkable.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional fixed bed catalytic reactor;
The figure is a partially cutaway perspective view showing an apparatus for carrying out a method for removing dust from a fixed bed catalyst layer of a dry denitrification apparatus according to an embodiment of the present invention, and FIG. 3 is a graph for explaining the present invention. . DESCRIPTION OF SYMBOLS 1...Reactor, 4...Rostle, 5...Catalyst support network, 6...Catalyst layer, 9, 10...Vertical gas barrier wall, 11...Horizontal gas barrier wall, 14. ...Damper, 1
5...Air cylinder.

Claims (1)

[Claims] 1 Branch the gas flow path to be treated into two or more, and add two or more to the branched flow path.
The above fixed-bed catalyst beds are arranged in parallel, and the flow rate of the gas supplied to the catalyst bed to be dedusted is controlled to be higher than normal by means of a flow rate adjusting means (for example, a damper) installed in a branched gas passage connected to the catalyst bed. Reduce the feed gas flow rate to other catalyst layers at the same time,
After the flow rate of the gas supplied to each catalyst layer is increased from normal to a range where the catalyst layer does not become fluidized, the flow rate of the gas supplied to each catalyst layer is returned to the normal flow rate, and the catalyst particles and soot in the catalyst layer to be dedusted are separated and dedusted. A method for removing dust from a fixed bed catalyst bed, characterized by: