GB2090544A - Washing column - Google Patents

Abstract

The washing column for the cleaning of exhaust air and gases by means of a washing liquid contains a plurality of washing stages 2, in each of which an atomized layer 3 is produced, in a space which contains no internally mounted components, by means of spray nozzles 4 which are mounted in the wall 5 of the column. In each washing stage 2 the droplets of washing liquid which are collected on the wall of the column 5 are led into a collecting channel 10. The washing liquid is drawn by suction from the collecting channel 10 and delivered to the spray nozzles 4 under pressure by a pump 11 located outside the washing space. In an alternative construction the column is horizontal with collecting compartments along the bottom of the column separated by weirs over which the liquid flows from one end of the column to the other. <IMAGE>

Description

SPECIFICATION Washing column The invention relates to washing columns for cleaning exhaust air and gases by means of a washing liquid, with a plurality of washing stages, in which an atomized layer with repeated circulation of the liquid is produced.

Washers with internally mounted components of various kinds are known, for example bodies of packing material, filters, bubble trays and perforated bottom plates, which all serve the purpose of distributing the washing liquid over a large area so as to attain the largest possible exchange surface area between the gas and the liquid. The distribution of the liquid so as to produce the contact boundary area between the gas and the liquid is obtained in these washers by the energy of the gases to be washed. Due to the many reversals and accelerations of the gas, such washers have a considerable pressure loss, which materially impairs the exchange action and the capacity of the washer.

Since it is more economical to obtain the distribution of the washing liquid over a large area by pressure energy, spray washers of various different constructions have been developed. In these washers the washing liquid is distributed by means of spray nozzles and is sprayed mainly axially but also partly radially into the washing column. The washing process in these washers, in which the whole of the space within the column for the exchange of material between the gas and the liquid is very badly utilized, takes place in one stage.

In order to achieve better utilization of the whole of the volumetric space within the column as an exchange space, multi-stage washers have been developed in which the washing liquid is sprayed through rotating distributing elements mounted in the space within the column and is circulated repeatedly in each stage. These washers have a very low pressure loss and, due to the multi-stage method of operation, a good washing performance. The multi-stage washers have, however, the disadvantage that the free passage of the gas to be washed is obstructed by the internally mounted components so that the efficiency (of these washers) is thereby impaired, and that the normal wear of the movable internally mounted elements, such as drive shafts and shaft bearings for the rotary distributing elements necessitates expensive regular servicing.

The problem underlying the invention is to provide a washing column with a minimum pressure loss, the construction of which avoids the use of movable parts for the liquid spraying apparatus.

Starting from a washing column of the kind initially described, this problem is solved by a washing column which has spray nozzles with liquid under pressure for producing an atomized layer in the washing space of each stage, which (washing space) is devoid of internally mounted components, as well as a circulating device with a collecting channel for the droplets of the atomized layer that are collected on the wall of the column and also a feed pump arranged outside the washing space for supplying the spray nozzles with washing liquid from the collecting channel.

Further features resulting from the invention are the spray nozzles mounted in the wall of the column and distributed within each washing stage at various different heights over the circumference of the wall of the column with the same or a different spraying direction.

In an advantages construction of the invention, the spray nozzles are formed as flat jet nozzles.

In a further constructional form of the washing column according to the invention, the spray nozzles of each washing stage are mounted in a separate spray tube which is arranged coaxially with the longitudinal axis of the column.

According to the invention, the washing column may be made of either vertical or horizontal construction.

In the washing column according to the invention almost the whole of the cross-section of the column is made available as a cross-sectional area which allows free passage for the gas, so that the loss of pressure is extremely low. Because of the minimal pressure loss the washing column is characterised by a very good exhange action and a high capacity. Finally, due to the fact that the movable parts which are subject to wear have been eliminated from the spraying apparatus, the washing column requires servicing only at very long intervals and consequently has substantially lower operating costs than the known washers.

The invention is explained in detail below with reference to embodiments shown in the drawing, in which: Figure 1 shows schematically a longitudinal section of a vertical washing column and Figure 2 is a diagrammatic longitudinal section of a horizontal washing column.

The washing column 1 according to Fig. 1 has for example three washing stages 2 in which the washing liquid is brought into intimate contact with the gas or exhaust air to be cleaned in the form of a large area atomized layer 3 in an exchange space containing no internally mounted components.

The atomised layer 3 of each washing stage 2 is produced by flat spray discharge nozzles 4 which are arranged on the inner circumference of the wall 5 of the column at different heights and so that they discharge radially.

The gas to be washed enters the column 1 through the inlets 6 in the bottom region (of the said column), flows through the individual washing stages 2, in which the impurities are washed out of the gas by the washing liquid, as well as through a spray catcher 7 arranged in the domed top part of the washing column 1 for separating out the droplets of washing liquid which may possibly be entrained by the vapour, and leaves the washing column through the outlet 8. The washing liquid-flows through the feed pipe 9 into the collecting channel a 110 of the upper washing stage.In the individual washing stages the washing liquid is fed by a pump 11 from the collecting channel 10 to the flat spray discharge nozzles 4 which spray the washing liquid radially through the column and, due to their relative vertical displacement, produce in (each of) the exchange stages an atomized layer or zone which consists of a plurality of parallel layers extending in various different directions. The exchange of material is effected in the spray layer, in which the gas to be cleaned comes into intimate contact with the washing liquid which is sprayed over a large exchange surface.The pumps 11 deliver a multiple of the quantity of washing liquid supplied, so that it is ensured that a sufficiently thick atomized layer 3 is produced in each washing stage 2 to achieve optimum utilization of the absorptive capacity of the washing fluid in each washing stage.

The sprayed droplets of washing liquid are collected by the outer wall 5 of the column and flow back over the latter into the collecting channels 10. In this way the washing liquid is circulated repeatedly in each washing stage 2.

The surplus washing liquid flows over the outer overflow edge 1 Oa of (each of) the individual collecting channels 10, which (outer edge) is lower than the inner edge 1 Ob of the respective collecting channel, into the subjacent collecting channel 18 O of the next washing stage 2.

The washing liquid loaded with impurities is discharged from the sump 1 3 of the washing column through the outlet 1 2.

The horizontal type of construction of the washing column 14 according to Fig. 2, which is sometimes advantageous for spatial reasons and in which those component parts which are the same as or similar to component parts of the vertical washing column 1 are indicated by the same references, operates essentially in the same way as the vertical washing column. The sprayed washing liquid is received in the lower part of the horizontal washing column 14 in chambers 16 separated from each other by weirs as and flows, as determined by the different heights of the weirs, from one chamber to the respective next chamber and into the sump 13, and is then discharged via the outlet 1 2.

In Fig. 1 there is shown a further advanta- geous embodiment of a washing column which is advantageous in the case of large diameter columns. In this embodiment the spray nozzles 4 of each washing stage 2 are fitted in a separate spray tube 17 which is arranged coaxially with respect to the longitudinal axis 18-18 and is connected to the feed pump 11 by a tube 19 which extends outwardly from the column.

As described in a copending application of the same date No. (claiming priority from German application No. P 31 00005.3), to which reference is made for detailed description, apparatus similar to the washing column n described in the present application can be used as a rectifying column, primarily for vacuum operation, in which the liquid to be rectified is atomized and brought into contact with steam.

Claims (9)

1. Apparatus for contacting a liquid with a gas or vapour comprising a column with an inlet for the passage of the gas or vapour through the column and a plurality of stages within the column in which the gas or vapour is brought into intimate contact with droplets of the liquid, each stage comprising spray nozzles supplied with liquid under pressure for producing an atomized layer in a space which is free of internally mounted components, a collecting channel or compartment for collecting the sprayed liquid, and a feed pump arranged outside the said space for supplying the spray nozzles with liquid from the collecting channel or compartment.

2. Washing column for cleaning exhaust air and gases by means of a washing liquid, with a plurality of washing stages, in which an atomized layer with repeated circulation of the liquid is produced, characterized by spray nozzles supplied with liquid under pressure for producing an atomized layer in the washing space of each stage, which washing space is devoid of internally mounted components, as well as a circulating device with a collecting channel for the droplets of the atomized layer that are collected on the wall of the column and a feed pump arranged outside the washing space for supplying the spray nozzles with washing liquid from the collecting channel.

3. Washing column according to claim 1 or 2, characterized by the fact that the spray nozzles are mounted in the wall of the column.

4. Washing column according to claim 1, 2 or 3, characterized in that the spray nozzles of each washing stage are vertically offset.

5. Washing column according to any one of claims 2 to 4, characterized in that the spray nozzles of each machine stage are distributed over the circumference of the wall of the column with the same or a different spraying direction.

6. Washing column according to claim 1 or 2, characterized in that the spray nozzles of each washing stage are mounted in a separate spray tube which is arranged co-axially with respect to the longitudinal axis of the column

7. Washing column according to any one of claims 1 to 6, characterized in that the spray nozzles are formed as flat jet nozzles.

8. Washing column according to any one of claims 1 to 7, characterized by a vertical construction of the column.

9. Washing column according to any one of claims 1 to 7 characterized in that the column is horizontally arranged.