JPS5929286B2 - Koteishiyoshikishiyokubaihannoki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixed bed catalytic reactor for treating exhaust gas containing dust, for example, a fixed bed catalytic reactor for a dry flue gas denitrification device.

When exhaust gas containing dust such as carbon and ash, such as oil-fired boiler exhaust gas, is denitrified using a fixed bed catalyst reactor, the dust accumulates on the catalyst layer, so the pressure loss in the catalyst layer increases over time. In addition, uneven flow of exhaust gas occurs in the reactor, reducing denitrification performance.

If the operation is continued from this state, the pressure loss in the catalyst layer will increase more and more, and it will eventually become impossible to operate the catalytic reactor continuously.

As a measure to prevent such dust accumulation, it is common to install a dust removal device upstream of the catalytic reactor, but dry flue gas denitrification devices have a reaction temperature as high as 300 to 400°C, High-performance dust removal equipment in the area is technically problematic and expensive.

This invention was made to solve the above-mentioned problems, and an object thereof is to provide a fixed bed catalytic reactor that can treat exhaust gas without dust removal.

In order to achieve this object, in the present invention, two or more catalyst layers are provided, and a hopper portion whose cross-sectional area decreases in the gas flow direction is provided on the gas outlet side of each of the catalyst layers, and each of the hopper portions is A gas amount adjustment damper is installed on the downstream side to adjust the amount of gas passing through the catalyst layer, and a collection duct is provided that communicates with the downstream side of all of the gas amount adjustment dampers. A gas rectifying means is provided on the gas inflow side of the layer, and a catalyst scattering prevention means is provided on the gas outflow side of the catalyst layer.

FIG. 1 is a schematic plan sectional view showing a fixed bed catalytic reactor according to the present invention, and FIG. 2 is a schematic front sectional view.

In the figure, Ia and 1b are reactors divided into two, and 2a
, 2b is a catalyst layer 2a, a catalyst layer attached to the gas outflow side of 2b, and 4 is a reactor 1a.

1b is a reactor inlet duct connected to the inlet of the catalyst layer 2a, 6 is a gas rectifying means provided on the gas inflow side of 2b, and 11a and 11b are catalyst layers 2a, respectively.
, 2b, and the cross-sectional area of the hopper parts 11a, 11b decreases in the gas flow direction.

3a and 3b are gas volume adjusting dampers installed on the downstream side of the hopper parts 11a and 11b, respectively; 5 is a damper 3;
a and the downstream side of the damper 3b, which is a reactor outlet duct which is a collecting duct.

In this fixed bed type catalytic reactor, normally the same volume of exhaust gas is sent from the duct 4 to the reactors 1a and Ib.

A NOx reducing gas (for example, N) I3 is added to this exhaust gas on the upstream side of the duct 3, and the exhaust gas is added to the catalyst layer 2a,
When passing through 2b, a denitrification reaction takes place, and the denitrified exhaust gas is discharged from the duct 5.

If this kind of operation continues, soot and dust will form on the catalyst layers 2a and 2b.
The pressure loss of the catalyst layers 2a and 2b increases over time.

Then, when the pressure loss of the catalyst layers 2a, 2b reaches a predetermined value, one of the dampers, for example, the damper 3a, is throttled to an arbitrary opening depending on the pressure loss.

Then, the speed of the exhaust gas passing through the catalyst layer 2b increases, the catalyst particles in the catalyst layer 2b are fluidized, the catalyst particles and the dust are separated, and the separated dust is removed along with the gas flow.

From this state, when the damper 3a is opened and the damper 3b is closed, the soot dust deposited on the catalyst layer 2a is removed in the same manner as described above.

By the way, when a gas amount adjusting damper is attached to the gas inflow side of the catalyst layers 2a, 2b, a drift of exhaust gas is caused by the gas amount adjusting damper on the gas inflow side of the catalyst layers 2a, 2b.

For this reason, soot and dust locally adheres to the inlet surfaces of the catalyst layers 2a and 2b, making it difficult for exhaust gas to pass through the parts to which soot and dust have adhered. , 2b increases, local fluidization of the catalyst layers 2a and 2b occurs, and the catalyst in those areas is scattered downstream together with the exhaust gas, resulting in a blow-through phenomenon.

When this phenomenon occurs, the exhaust gas from that part remains untreated and flows into the reactor 1a.

It will pass through 1b.

However, in this invention, since the dampers 3a and 3b are attached to the gas outlet sides of the catalyst layers 2a and 2b,
Damper 3a.

3b prevents a drift of the exhaust gas from occurring on the gas inflow side of the catalyst layers 2a and 2b, so that the above-mentioned blow-by phenomenon does not occur and the exhaust gas can be reliably treated.

In the above embodiment, the dampers 3a and 3b were opened and closed to fluidize the catalyst particles in the catalyst layers 2a and 2b, but by opening and closing the dampers 3a and 3b, the catalyst particles in the catalyst layers 2a and 2
By reducing the speed of exhaust gas passing through b, the catalyst layer 2a,
The soot and dust may be removed by breaking the balance of 2b and separating the catalyst particles from the soot and dust.

In other words, in the catalyst layers 2a and 2b in which catalyst particles are simply packed to a certain layer height, due to the balance between the catalyst's own weight and the force pushing up the catalyst when exhaust gas passes through the catalyst layer 2, there is a gap between the catalyst particles. Changes are difficult to occur in the voids of

However, if the speed of the exhaust gas passing through the catalyst layer 2a p2b 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 soot and dust are separated, the soot and dust are removed, and the 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 layers 2a and 2b at a normal speed of 1.7 m/s to deposit soot and dust, and then the speed of the exhaust gas was increased to 1.7 m/s three times.
The speed was lowered to 2m/s for a short time.

The first deceleration operation was performed with soot and dust deposited on the catalyst layers 2a and 2b to such an extent that the surfaces of the catalyst layers 2a and 2b were locally blown through, in order to clarify the soot and dust removal effect. .

As a result, when the exhaust gas velocity is returned to 1.7 m/s, the pressure loss in the catalyst layers 2a and 2b becomes the initial pressure loss 2.
It was reduced to 240 mmAq, which is almost close to 0.05 mmAq, showing the remarkable effect.

At the time of the second and third deceleration operations, the catalyst layer 2a
.

Although the reduction in pressure loss is small due to the small amount of dust accumulated in 2b, it is clear that it is effective, and if the speed reduction operation is performed periodically, the amount of accumulated dust can be reduced to a desired amount or less. It confirms what can be done.

From the above, the operation of dampers 3a and 3b is as follows:
It can be said that the speed of exhaust gas passing through the catalyst layers 2a and 2b may be increased or decreased.

That is, the soot and dust can be removed by setting the speed of the exhaust gas passing through the catalyst layers 2a and 2b to a different speed from the normal speed and separating the soot and dust from the catalyst particles in the catalyst layers 2a and 2b.

FIG. 4 is a partially cutaway plan view showing another fixed bed catalytic reactor according to the present invention, and FIG. 5 is a partially cutaway side view of the same.

In the figure, 1 is a reactor, 6 is a Rosdol fixed to the reactor 1, 7 is a catalyst support network laid on the Rosdol 6, 8 is a partition wall fixed to the reactor 1 and Rosdol 6, and the partition wall 8 The catalyst layer 2 is divided into six parts.

9 is a catalyst migration prevention net attached to the partition wall 8; 10 is a catalyst scattering prevention net provided on the gas outflow side of the catalyst layer 2; the catalyst scattering prevention net 10 is attached to the partition wall 8.

11 is a pyramidal hopper attached to the upper part of the partition wall 8; 12
13 is a damper for adjusting the gas amount installed on the downstream side of the hopper 11; 13 is a damper shaft provided on the damper 12;
4 is an air cylinder for opening and closing the damper 12.

In this fixed bed type catalytic reactor, in order to remove the dust accumulated on the catalyst layer 2, one damper 12 is fully opened and the other dampers 12 are closed all at once or one by one. The provided catalyst layer 2 is fluidized and soot and dust are removed.

This operation is performed for each catalyst layer 2 in sequence.

In this fixed bed type catalytic reactor, the catalyst layer 2
Since the catalyst scattering prevention net 10 is provided on the gas outflow side, when the catalyst layer 2 is fluidized to remove soot and dust, it is possible to prevent the catalyst from scattering together with the soot and dust.

In addition, since the hopper 11 is installed, the damper 12
is small, and the torque for driving the damper 12 can be small.

Furthermore, since the catalyst migration prevention net 9 is provided, the surface height of the catalyst layer 2 will not vary significantly and the degree of reaction will not vary from place to place.

As explained above, in the fixed bed catalytic reactor according to the present invention, the soot and dust accumulated on the catalyst layer can be removed, so that the exhaust gas that has not been removed can be treated without stopping the operation. Furthermore, there is no need to change the amount of exhaust gas treated during soot and dust removal, the exhaust gas can be treated reliably, and furthermore, it is possible to prevent the catalyst from scattering.

Further, in the case of a large fixed bed type catalytic reactor, by dividing the catalyst layer into an appropriate number, it is possible to effectively remove soot and dust accumulated on the catalyst layer.

In the above embodiment, the planar catalyst layer is divided, but two or more catalyst layers may be provided in multiple stages, and a gas amount adjusting damper may be attached to each of the catalyst layers.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan cross-sectional view of a drying fixed bed catalytic reactor according to the present invention, FIG. 2 is a schematic front cross-sectional view, FIG. 3 is a graph for explaining the present invention, and FIG. FIG. 5 is a partially cutaway plan view showing another fixed bed catalytic reactor according to the present invention, and FIG. 5 is a partially cutaway side view. 1, 1a, 1b--reactor, 2, 2a,
2b-...Catalyst layer, 3a, 3b...
・Damper for gas amount adjustment, 4... Reactor inlet duct, 5... Reactor outlet duct, 6...
Rosdol, 7... Catalyst support network, 8...
Partition wall, 9... Catalyst migration prevention net, 10...
... Catalyst scattering prevention net, 11 ... Pyramid hopper, 1
1a, 11b...hopper section, 12...
Damper for adjusting gas amount, 14...Air cylinder.

Claims (1)

[Claims] Twelve or more catalyst layers are provided, a hopper portion whose cross-sectional area decreases in the gas flow direction is provided on the gas outflow side of each of these catalyst layers, and a hopper portion whose cross-sectional area decreases in the gas flow direction is provided on the downstream side of each of these hopper portions. A gas amount adjustment damper is installed to adjust the amount of gas passing through the catalyst layer, and a collection duct is provided that communicates with the downstream side of all of the gas amount adjustment dampers, and a gas inflow side of the catalyst layer is provided. A fixed bed catalytic reactor characterized in that it is equipped with a gas rectification means. 22 or more catalyst layers are provided, a hopper portion whose cross-sectional area decreases in the gas flow direction is provided on the gas outflow side of each of these catalyst layers, and the gas passes through the catalyst layer on the downstream side of each of these hopper portions. A gas volume adjustment damper is installed to adjust the gas volume, a collection duct is provided that communicates with the downstream side of all of the gas volume adjustment dampers, and a gas rectification means is provided on the gas inflow side of the catalyst layer. . A fixed bed catalytic reactor, characterized in that a catalyst scattering prevention means is provided on the gas outflow side of the catalyst layer.