SE465655C - Method and apparatus for filtering a liquid - Google Patents

Description

15 20 25 30 465 655 The outlet for purified liquid is inside the bed, this means that the outlet must be fitted with a strainer to prevent the bed material from following the liquid out. This entails a high pressure drop and a high risk of clogging. A screw feeder has a short service life in sand.

There are many other suggestions for filters with a moving bed, but they have been too complicated or had other disadvantages that made them unusable.

* French patent specification 72.fl6629 shows a filter which has an open filter tank at the top, a sand bed with a free top, pipes for transporting the sand to a washing device placed above the bed. The sand is returned to the bed with free fall. The liquid to be filtered is supplied to the lower part of the bed through slotted pipes and taken out over an overflow above the bed.

Swedish patent 7613367-7 discloses a filter of very close construction. The sand transport pipe has been placed in the center of the bed and is powered by air instead of liquid.

The laundry is fed with liquid from the top of the bed. The Tf function is otherwise exactly the same as the filter in the French patent specification.

This filter has been widely used due to its simple construction. However, it has several disadvantages which limit its use and which can cause malfunctions and a great need for service.

The laundry placed in the middle of the bed gives the filter a great height and a large volume of water. To be able to check the function of the filter and to perform maintenance work, for example, replace the sand pump pipe, the filter. It is therefore necessary, it is necessary to go up to such a great height above the filter that one. 2. can stand there. A filter according to patent 7613367 on a 5 m filter surface requires about 8 m ceiling height and weighs about 32 tons. This often makes it impossible to install the filter in existing premises and that the construction cost for new blinds is high. '10 15 20 25 ßO The sand pump tube placed inside the bed cannot be checked without picking it up. If the pump pipe was used for so long that it tore, it may be impossible to replace it without emptying the filter of sand. This results in a long and expensive downtime.

The location of the washing device makes it impossible to wash in more than one step or to add any detergent.

This limits the use of the filter to cases where the contaminants on the sand come off easily.

Another problem with these filters is that the movement of the sand bed is not uniform over the entire bed, this means that the sand movement can easily be stopped. If this happens, the stagnant sand is quickly blocked by contaminants.

The rest of the bed becomes overloaded, the filtration deteriorates and the increased flow can break up the bed.

The non-uniformity of the sand movement is caused, among other things, by a large inlet hood and several inlet pipes which obstruct the free movement of the sand. The angle between the vertical wall of the filter tank and the wall of the bottom cone is 1500, the change in direction of sand causes a considerable braking of the bed. . The sand pump sucks a bit above the surface of the bottom cone and there is no control of the sand at the end of the pump pipe. This means that a very small disturbance, for example a sloping sand pump, can cause large discrepancies in the sand flow.

The sand distributor cone at the bottom can also contribute to operational disturbances. Fat, fibers, etc., can accumulate under the cone and together with sand form lumps that completely or partially impede sand flow. If the deaeration is clogged, the sand cone can be filled with air and lift up the bed and washing. This is an expensive accident that causes long interruptions in operation. 10 15 20 25 30 465 655 In the following it will be shown how it is possible to build a filter where the previously described disadvantages are eliminated. 1; The filter can be made low if the sand wash is placed outside the filter bed and '1 approximately at the same height as this. A sand pump pipe transports to the wash from the wash sand from an outlet below the bottom cone up inlet. An outlet to other pump pipes transports the sand to the top of the sand bed or, if the sand is very difficult to clean, to a second wash and from there up to the top of the bed.

The location of the laundry outside the filter container allows great freedom of the design of the laundry. In some cases, the sand can have coatings that are very difficult to remove. You can then, for example, insert a rotating drum with internal blades that process the sand so that the coatings come loose.

The external placement of washers and sand pump pipes makes them easy to control and maintain. It is unnecessary to go up on the filter, no large distance is required between the roof and the top of the filter.

To ensure uniform sand movement in the bed, it should be as free as possible from details that can brake to be filtered, through a ring channel in the lower, outer part of the bed. The annular channel can be formed by the outer wall of the filter container, the outer wall of the bottom cone and by a wall which forms an angle of 160-1700 with the container wall. The large angle means that the change in the direction of flow of the sand becomes small and thus the deceleration of the speed of the sand also becomes small.

On large filters, in order to obtain a uniform flow of liquid in the bed, it may be necessary to let the liquid in also through an inner annular channel. It can be formed by the top of the sand distributor cone and an inlet hood which is placed slightly above the sand distributor cone and which is fed through a central, vertical pipe. 10 15 20 25 BO .Pa C \ CT! CN Cfl U1 The underside of the sand distributor cone is closed and forms with the bottom cone an annular channel with, in the direction of movement of the sand, decreasing cross-section. This causes an even acceleration of the sand and contributes to a uniform sand movement.

Fig. 1 shows Fig. 2 Fia 3 Fig. Ä prior art and a filter according to the invention. schematically an embodiment of the invention. shows a design with two washes. shows a way to reduce wear of the bottom cone. is a size comparison between a filter with A suitable embodiment of the filter for commonly occurring filtration cases is shown in Fig. 1. The filter container 1, which may have a circular or polygonal cross-section, is open at the top and in its upper part provided with an outlet 2, for filtered liquid, with an assault edge 3.

In the lower part of the container there is an inlet Ä for the liquid to be filtered. An inlet channel 5 is formed by the outer wall of the container, an inner wall 6 and the wall 7 of the bottom cone.

A throttle plate 8, mounted in the inlet duct 5, is shaped so that the outflow from the annular duct becomes uniform.

The inner wall 6 of the ring channel and the wall 1 of the container form an angle of 160-1700. The wall 1 of the container and the upper wall 7 of the bottom cone form an angle of about 1500. The walls 7 and 9 of the bottom cone can, in order to reduce the height of the filter, form an angle of 160-17o °.

In the bottom cone there is a sand distributor cone 11 on the supports 10.

The upper tip angle of the sand distributor cone can be 60-900, the lower angle approximately equal to the angle of the bottom cone or larger. The angles of the sand distributor cone affect the uniformity of the sand movement and can be different on different sized filters.

In the lower part of the bottom cone, a replaceable ring 12 is inserted.

The function of the ring is to protect the bottom cone against wear. 10 15 20. 25 30 465 655: If the upper edge of the ring protrudes above the surface of the bottom cone, Fig. 3 will, outside the ring, form a layer of stationary sand # 2. This sand layer protects the bottom cone against wear where the speed is high.

Under the bottom cone, an outlet cover 13 is mounted. In its side, a drain pipe 14 with a valve 15 is inserted. This tube was used when emptying the filter.

Between the ring 12 and the outlet cover there is a net or a perforated wall 16, its task is to prevent the sand from accompanying the liquid out when emptying.

The outlet cover is provided with an outlet pipe 17 for the sand, to which the sand pump pipe 18 is connected. The sand pump tube has, near its lower end, an inlet 19 for air or water for propelling the sand. The upper end of the sand pump pipe opens into an air or water separator 20, located above the laundry 21 which is placed in a container 22. Fig. 1 shows that the sand pump pipe passes through the center part of the laundry but the pipe can instead pass the laundry outside the container and connect radially to the separator . The wash will then look like in Fig. 2.

The laundry consists, in this embodiment, mainly of an outer labyrinth part 23, an inner labyrinth part 24 and in the upper part an adjustable cover edge 25 with an outlet 26 for contaminated liquid.

A socket 27 in the walls of the containers allows liquid to flow from the filter container to the underside of the laundry.

The bottom of the washing container is inclined and at a small distance from the lowest point of the bottom the lower end of a sand pump pipe 28 opens, near its end there is an inlet pipe 29, alternatively 30, for air or water. Its upper end opens into a separator 31 located above the center of the bed. 10 15 20 25 30 35 .Iis- G \ C11 CN LH in An inner inlet channel is formed by an inlet hood 32 and by the top of the sand distributor cone. The duct is fed through the pipe 33. Detail 3Ä is a distribution plate which ensures that the sand bed becomes symmetrical and also protects the inlet pipe against wear.

The filter works as follows: The starting position is that the filter container is filled with liquid up to the overflow edge 25 and with sand so that the top of the bed, at a normal race angle, is 50-100 mm below the lower edge of the separator 31.

The sand movement is started by supplying air or liquid to the connections 19, ooh 29 or 30 of the sand pump pipes, this starts a flow of liquid in the pipes which will fluidize the sand and transport it from the bottom of the bed up to the top of the sand wash. The sand falls down through the wash to the bottom of the washing container, the sand pump pipe and is transported up to the top of the bed. the sand sucks up there by the second Filtration is started by letting liquid in through inlet pipes Ä and 33. The liquid enters the bed through the annular cavities that form under the inlet ducts. The liquid flow turns upwards, spreads in the bed and leaves its pollutants to the sand and leaves the bed through the free upper surface. The largest part of the flow goes out of the filter over the edge 3 and through the pipe 2. A small part of the flow it goes through the hole 27 into the lower part of the wash, up through the wash, where it meets the dirty sand and then, together with the dirt out over the overflow edge 25 and out through the pipe 26.

A filter with 2 washing devices, a labyrinth washer and a rotating drum washer is shown in Fig. 2. The drum washer consists of a drum 35, internally provided with helical vanes 36 which feed the sand and vanes 37 which move around the sand. The drum is driven by a slow-moving motor 38.

The washing liquid is led in through the tube 39 and is caught by the tray fi 40 and led out, together with the dirt. 10 20 465 655; The sand is led from the bottom of the bed and into the drum by the sand pump pipe Ä1.

The drum wash works here as a prewash for a labyrinth wash. The pre-washed sand falls down through the wash and is washed there a second time. The sand is then returned to the bed with a sand pump pipe.

It is possible to make many variants in Figs. 1 and 2.

You can, for example, if a drum wash provides sufficiently clean sand, place the drum, fig. 2, with the outlet over the middle of the bed. The maze cleaner and sand pump pipe 28 are not needed.

The principle of cleaning the sand outside the filter container allows great freedom to arrange the best possible cleaning system.

It is possible to combine different washing methods. ' It is possible to use detergent, solvent, hot water, etc. in one or more steps.

It is also possible to heat-treat the filter material, for example for regeneration or for easier release of contaminants.

Claims (1)

A 465 ess 9 Patentkrav. Device for filtration through a movable bed of granular material where the liquid to be filtered is supplied to the bed in its lower part and taken out of the filter over a overflow (2,3) located above the bed, washing of the filter material takes place outside the filter container (1) and the transport of the filter material from the bottom cone (7,9) of the filter container to the top of the wash (2l) and from the bottom of the wash to the top of the bed is made with air and / or water-powered pump tubes (18,28) characterized by the wash (21) being a countercurrent labyrinth wash (23,24) placed in a container (22), mounted next to the filter container and connected to it through an opening (27) or a tube, so that the liquid levels are approximately equal, that the labyrinth wash is provided with a device (25) for regulating of the washing liquid flow Device according to the preceding claim, characterized in that the liquid to be filtered is supplied to the bed through an annular inlet channel (5) formed by the outer wall (of the filter container). l) and of the bottom cone_wall (7} and of an inner wall (6) which at the same time constitutes an outer wall for the lower part of the bed. . Device according to one of the preceding claims, characterized in that the inner wall (6) of the annular channel and the wall (1) of the filter container form an angle of 160-179 degrees. . Device according to one of the preceding claims, characterized in that an inner, annular inlet channel is formed by an underside cone (32), placed at a small distance above the sand distributor cone (11), that the inlet channel is fed through a central pipe (33).