JPS5846345B2 - Gas-liquid contact device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve a horizontal gas-liquid contact device that is effectively used in equipment spaces with limited height, and in particular improves the uniformity of liquid dispersion in the packed bed. This invention relates to improvements to improve the contact effect.

When new sewage treatment plants are constructed these days, there is a trend to isolate them from the outside by making them semi-underground or underground, and opening the upper part of the facility to the general public as a playground or park.

In such a situation, a horizontal gas-liquid contact device called a cross-flow cleaning device, which is suitable for indoor equipment, is suitable for deodorizing equipment for exhaust gas in a sewage treatment plant.

This device feeds gas horizontally from one side of a packed bed containing a packed material in a hexahedral container (basically a rectangular parallelepiped) with a right-angled cross-section for the gas flow flowing horizontally. This is a gas-liquid contacting device having a mechanism for discharging liquid from the other opposing side surface, accumulating a liquid such as a cleaning liquid such as acid or alkali from the upper part of the packed bed, and draining the liquid from the lower part.

Conventionally, such devices have been designed based on empirical knowledge, and sufficient chemical engineering studies have not been conducted.

The present inventors completed the present invention as a result of conducting various experiments to obtain basic design data for this device.

Normally, the height of the packed bed of this equipment is around 1 m, and even including the accessory equipment for collecting and draining the cleaning liquid, the height of the equipment is significantly lower than that of a conventional vertical cleaning tower. It is extremely advantageous to perform cleaning with two or more types of cleaning liquids, such as alkali, in succession, but cleaning efficiency in the packed bed depends on how uniformly the liquid can be dispersed in the low packed bed height of around 1 m. This is an extremely important factor that influences

Conventionally, methods using a spray nozzle or a method using a single perforated plate have been known as means for evenly dispersing the accumulated liquid on the upper surface of the packed bed in such devices, but the former method suffers from pressure loss due to spraying. Since it is thick and requires a high-pressure pump, running costs are high, and the nozzle is easily clogged, and in the latter case, as shown in the comparative example shown later, the dispersion of the filtrate is uneven in the packed bed. .

The present invention is an improvement on this point, in which perforated plates having a large number of regularly arranged small holes are arranged in two stages, upper and lower, between the liquid inlet and the packed bed, and the lower perforated plate It is characterized in that the average aperture ratio of the upper perforated plate is equal to or lower than the average aperture ratio of the upper perforated plate.

Furthermore, when the gas flow rate is high, the pressure loss from the gas inlet side to the outlet side of the packed bed becomes so large that it cannot be ignored.
As a result, a phenomenon occurs in which the amount of liquid falling from each manufacturer on the lower perforated plate is smaller on the inlet side where the gas pressure is higher than on the outlet side.

To cover this, the large number of small holes in the lower perforated plate can be set so that the aperture ratio is large on the entrance side and small on the exit side.

Specifically, the arrangement spacing of the small holes on the lower perforated plate may be kept constant, and the hole diameter may be made smaller on the gas inlet side and smaller on the outlet side, depending on the expected change in gas pressure. Conversely, the number of holes per unit area may be smaller on the gas inlet side and smaller on the outlet side while keeping the hole diameter the same.

Further, it is not necessary to change the aperture ratio continuously in response to changes in gas pressure; the purpose can be sufficiently achieved even if the lower porous plate is divided into several sections and the opening ratio is changed in units of sections.

In either case, there is no problem even if the aperture ratio of the lower perforated plate partially exceeds the aperture ratio of the upper perforated plate on the gas inlet side, and the overall average aperture ratio of the lower perforated plate is higher than that of the upper perforated plate. It is good as long as it does not exceed that of .

Another method for dealing with changes in gas pressure is to make the lower perforated plate slope along the gas flow direction or to configure it in a stepped manner, in which case the gas inlet side is at a lower position and the outlet side is at a higher position. The liquid layer accumulated on the lower porous plate may be deep on the gas inlet side and shallow on the outlet side to balance the gas pressure.

The hole diameter of each perforated plate is 1~10m1ψ, preferably 2~5m
mψ, the arrangement interval is 5 to 30 mm, preferably 10 to 20
mm, and the aperture ratio is practically 0.5 to 10%, preferably 1 to 5%.

Further, it is sufficient if the distance between the two upper and lower perforated plates is 20 mm or more, and the overall height of the device is hardly affected.

The type of filler can be arbitrarily selected from commercially available products, taking into consideration the required contact efficiency, pressure loss, etc.

If the packed bed is small in width and length of 1 m or less, there may be only one liquid inlet in the center, but if the packed bed is larger than that, it is preferable to have multiple inlets.

Example Using an apparatus as shown in FIG. 1, the degree of liquid dispersion in the packed bed of a horizontal gas-liquid contact device was measured.

In the figure, 1 is a packed bed, 2 is a gas inlet, 3 is a gas outlet,
4 is a liquid inlet, 5 is an upper perforated plate, 6 is a lower perforated plate, and 7 is a liquid reservoir provided to measure the degree of dispersion of the liquid descending in the packed bed. Equally divided into 6 rooms,
Furthermore, two chambers g and h are provided on the gas downstream side.

8 is a gas distribution plate, and 9 is a demister.

The packed bed 1 has a height of 700 mm (the lowest 100 mm is a dead space), a width of 600 mm, and a length of 900 mm. Therefore, each chamber of the liquid reservoir 7 has a length of 150 mm and a width of 600 mm.

A commercially available plastic filling was used. The gas flow velocity at the inlet of the packed bed is 2 m/see liquid (water)
The amount was 222007/m2 hours.

Therefore, for a packed bed irrigation area of 0.54 tri:, the irrigation rate is 200 t/min.

The following four combinations of perforated plates were used: A, B, C, and D, and the results of measuring the amount of liquid passing through each chamber (a = h) of the liquid reservoir 7 (1/min) are shown in Figure 2 for each combination. .

Each perforated plate had holes arranged at equal intervals over the entire surface, and the aperture ratio was varied depending on the hole diameter.

Also, the distance between the upper and lower perforated plates in B, C, and D is 30 mm.
And so.

As can be seen from FIG. 2, in case A where only one perforated plate is used, the liquid distribution is very non-uniform.

This also applies to case B in which the aperture ratio of the lower perforated plate is larger than that of the upper perforated plate even if two perforated plates are used.

On the other hand, in Case C and Case D in which the present invention was implemented, it is clear that the liquid dispersion is uniform.

In both cases, the amount of liquid is small in the first chamber a, and the reason why the liquid has come to the 7.8D chambers g and h outside the packed bed is due to the effect of the liquid being blown backward by the gas flow. In order to prevent this, known techniques such as configuring the filling layer itself to have a forwardly inclined parallelogram cross section or providing a front spray may be applied.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus based on the present invention, and FIG. 2 is a diagram showing test results, with A and B showing comparative examples and C2D showing an example. And each graph A, B, C. The horizontal axis of D corresponds to the measurement position (each chamber of the liquid reservoir) shown in Figure 1, and the vertical axis represents the liquid volume (1/min).
shows. 1... Filled bed, 2... Gas inlet, 3.
...Gas outlet, 4...Liquid inlet, 5...
... Upper perforated plate, 6... Lower perforated plate, 7...
...Liquid reservoir, 8-...Gas distribution plate, 9...
・・Akustar

Claims (1)

[Scope of Claims] 1. In a horizontal gas-liquid contact device having a mechanism for accumulating liquid from the upper part of the packed bed and draining the liquid from the lower part for a gas flow flowing horizontally in the packed bed, the liquid inlet and the filling A gas liquid characterized in that perforated plates having a large number of regularly arranged small holes are arranged in the middle of the layer in two stages, upper and lower, and the average aperture ratio of the lower perforated plate is equal to or less than the average aperture ratio of the upper perforated plate. Contact device. 2. The device according to claim 1, wherein the large number of small holes in the lower perforated plate are set so that the aperture ratio is small on the gas inlet side and small on the gas outlet side. 3. The device according to claim 1, wherein the lower perforated plate is installed at an angle along the gas flow direction so that the gas inlet side is at a low position and the gas outlet side is at a high position. 4. The device according to claim 1, wherein the lower perforated plate is configured in a stepped manner along the gas flow direction, and is installed so that the gas inlet side is at a low position and the gas outlet side is at a high position.