GB2067084A

GB2067084A - Spray nozzle assembly for filter devices

Info

Publication number: GB2067084A
Application number: GB8038821A
Authority: GB
Original assignee: Edeleanu GmbH
Current assignee: Edeleanu GmbH
Priority date: 1979-12-28
Filing date: 1980-12-03
Publication date: 1981-07-22
Also published as: PL228663A1; JPS5697515A; MX152530A; PL128017B1; YU316280A; DE2952661B1; BR8008470A; AR224043A1; DE2952661C2; GB2067084B

Abstract

Spray nozzles (3) are disposed in double rows (21, 22) arranged in a succession in the direction of movement of a filter cake to be washed. The nozzles are equally spaced in each row and the nozzles in one row (21) in each double row are staggered with respect to the nozzles in the other row (22). The nozzles of each double row are also staggered with respect to the nozzles of the adjacent double rows (21, 22; 31, 32; 41, 42), in the direction transverse to the direction of filter cake movement (7), by the nozzle pitch (a) divided by the total number of rows (n). This arrangement distributes the sprayed wash liquid more evenly over the filter cake. <IMAGE>

Description

SPECIFICATION Spray nozzle assembly for filter devices The present invention relates to a spray nozzle assembly for filter devices for spraying wash liquid on-to the filter cake to be washed, having pipes supplying the spray nozzles with wash liquid, whereby the spray nozzles are arranged above the filter cake in several successive double rows in the direction of the filter cake movement, the spray nozzles of the individual rows of each double row are arranged in staggered position and the spray nozzles of all rows at equal distance from each other. This corresponds to a triangular pitch arrangement of the nozzles of a double row.

Such spray nozzles devices are used in commercial units, for instance, to wash the wax separated from rotary cellular vacuum drum filters, pressure filters or belt-pan type filters. The wash liquid is applied to the filter cake through an arrangement of spray nozzles connected to distribution pipes. In the spraying of the wash liquid the presently known arrangements of spray nozzles do not produce the best possible liquid distribution on the filter cake.

For instance, in rotary cellular vacuum drum filters, as used in mineral oil dewaxing units for separating the wax, the washing agent is usually distributed through twelve wash pipes positioned parallel to the drum axis. Each of the wash pipes is fitted with 20 to 40 nozzles. Most of the oil in the wax cake is to be removed by the washing agent.

Due to this construction, the nozzle rows are arranged vertically to the direction of filter movement. The number of nozzle rows is twice that of the wash pipes whereby the nozzles of the even and uneven rows are directly arranged behind one another in a linear row, running parallel to the direction of the filter movement. Thus, each even number and eneven numbered nozzle row form a double row.

Because of this arrangement, parallel washing stripes are formed on the filter cake passing through the washing zone, when the washing fluid is sprayed on the cake. This can be seen from Fig. 1.

Due to this customary spray nozzle arrangement, in the course of one rotation of this cellular drum filter always the same areas of the wax cake to be washed pass the projection of the middle of the spray nozzles, with n nozzles rows"# times.

'As a rule, whirl jet, full type or even special nozzles are used as a rule. Although fairly good spraying patterns can be achieved with different types of nozzles, these patterns say very little about liquid distribution on the surface to be washed. If the washing agent quantity emitted from a nozzle is integrated over the sprayed circular segment to determine the distribution of the liquid on the moving cake surface, it will be observed that the surface to be washed is unevenly sprayed on-to within the width of a jet cone and that consequently the intensity of washing varies.

In addition, the spraying angle and the distribution of liquid of the spraying pattern depend on the upstream pressure of the nozzle, and the quantity of the washing liquid, respectively.

For a rotary cellular drum filter with n nozzle rows and a nozzle arrangement as described above, the filter surface area sprayed onto by the various individual nozzles (their so-called spraying patterns) covers the filter surface"# times. Therefore, within the spraying pattern, these quantities deviating from the mean value ofthe minimum and maximum quantities, are additive byfli2.

Consequently, when passing through the washing zone, some segments of the filter cake are repeatedly contacted with large amounts of washing liquid whereas other segments are repeatedly sprayed with too little wash liquid.

Consequently, the uneven distribution of the washing liquid caused by the usual arrangement of nozzles results in for example surplus wash liquid running down some areas of the filter drum unused.

In addition, channelling occurs which means that wash liquid preferentially penetrates such areas of the filter cake that offers less resistance to penetration while other areas of the filter cake receive much smaller quantities of washing agent. Thus, a considerable quantity of the wash liquid is uselessly wasted due to spotty over-dosage of some areas while other areas are insufficiently washed.

To ensure that all areas of the filter cake are sufficiently washed by this usual arrangement of nozzles, it is necessary to supply so large a quantity of wash liquid that the liquid sprayed in the insufficiently supplied zones of the spraying jet cone will be sufficient to adequately wash those filter cake segments which constantly pass through spray zones with low amounts of wash liquid. The result is that because of the high wash liquid consumption the associated separating equipment needed for the recovery of the washing agent must be sized for large throughput and requires a large amount of energy.

The purpose of the invention is to devise a spray nozzle assembly which more evenly distributes the wash liquid on the filter cake.

The solution to the problem is achieved by the invention in such a way that with unchanged arrangement of the spray nozzles (3) within a double row the arrangement of the spray nozzles of a double row are positioned in staggered arrangement in relation to the succeeding double row in direction transversely to the direction of movement of rotation of the filter cake.

The staggered nozzle arrangement of the double row ensures that the equal amounts of wash liquid are sprayed across the width and on all areas of the filter cake. This utilises lower quantities of wash liquid and improves considerably the washing effect with the same quantity of wash liquid, respectively.

As a result of the further development of this invention, the nozzles of the double rows are staggered by the distance "a" of two adjacent nozzles divided by the number "n" of the total nozzle rows.

This staggered arrangement of nozzles avoids the disadvantages of the areas of the spray cones overlapping one another with the minimum and maximum values of the liquid quantity within the jet cone area building up while the cake passes through the washing zone.

The nozzles staggered by a/n distribute the wash liquid evenly on the filter cake running through the washing zone. Each section of the surface of the filter cake is exposed to spray jet segments with much washing medium and to those segments with less washing medium so that the total quantity of the liquid sprayed on the various sections of the filter cake is almost identical. This avoids insufficient washing and uneconomically high quantities of wash liquid.

The invention is explained in detail by the examples shown in the drawing.

Shown are in Fig. 1 a known nozzle arrangement with nozzles in triangular pitch position, Fig. 2 the new nozzle arrangement with staggered nozzle rows, different from the common type.

A filter surface (1) formed by filter cake is sprayed with wash liquid. This is done using nozzles (3) which form spray cones (5) on the filter cake (1).

In Figures 1 and 2 the nozzles (3) are arranged from top to bottom in the rows 21,22,31,32,41,42 etc. The nozzles in the rows 21,22 as well as the nozzles in the rows 31,32,41,42 etc. form double rows with identical nozzle arrangement. This means that the nozzles of each row with the end digit 1 as well as nozzles of the rows with the final digit 2 show the same distance "a". The nozzles of the rows with end digits 1 and 2 are always staggered by the dis tanceal2. This means that the spray nozzles of a double row with initial digits 2,3,4 etc. are always arranged on a triangular pitch.

In the known spraying device shown in Fig. 1 the double rows 21,22,31,32,41,42 etc. are arranged beneath one another in the same sequence. This means that strips (8) are formed on filter cake (1) in direction of arrow (7) when the filter cake (1) rotates.

These strips are formed where across the direction of arrow 7 only border zones 9 of the spray cones 5 run over the filter cake. The strips 8 are areas of insufficient washing as indicated in Fig. 1 by a line.

In the spraying assembly according to the invention shown in Fig. 2, the double rows with the initial digits 2,3,4 etc. are no longer arranged symmetrically and evenly to one another in the direction of filter cake (1) movement marked with arrow 7.

Rather the double rows with the initial digits 2,3,4 etc. are staggered transversely to the direction of arrow 7 by the distance a/n with n equal to the number of all nozzle rows. This arrangement ensures even washing of the cake without formation of washing strips.

The various nozzles are connected to the wash pipes (10) which supply the double rows21,22 or 31, 32 or41, etc. Branch lines (11) of different lengths leading to the various nozzles (3) branch off from the wash pipe (10).

Claims

1. A spray nozzle assembly for spraying wash liquid onto filter cake in a filter device, said assembly comprising a plurality of spray nozzles disposed above the filter cake in double rows arranged in a succession in the direction of movement of the filter cake relative to the assembly, the spray nozzles of one row in each said double row being staggered with respect to the spray nozzles of the other ro-;j in said double row, and the spray nozzles in all said rows being substantially equally spaced from one another in their row, wherein the spray nozzles of a said double row are staggered with respect to the spray nozzles of the next adjacent said double rows in the direction transverse to the direction of filter cake movement relative to the assembly.

2. An assembly according to claim 1 wherein'the spray nozzles of said adjacent double rows are staggered by the pitch of two adjacent nozzles in a row divided by the total number of said rows. i

3. An assembly according to claim 1 or claim 2 including a wash liquid supply pipe connected to supply wash liquid to the nozzles in each said row.

4. An assembly as claimed in claim 1 or claim 2 including a wash liquid supply pipe having branch pipes connected to supply wash liquid to the nozzles in two or more of said rows.

5. A spray nozzle assembly substantially as described herein with reference to Figure 2 of the accompanying drawings.