| JPS54162274 | FILTER |
| WO/2019/048121 | AXIAL FLOW PUMP AND HOUSEHOLD APPLIANCE EMPLOYING SUCH PUMP |
| JP6061295 | A suspended particle condensation method and a device |
| WO1991008818A1 | 1991-06-27 | |||
| WO1981002393A1 | 1981-09-03 | |||
| WO1994001194A1 | 1994-01-20 |
| US4197201A | 1980-04-08 |
| 1. | Method of filtering a liquid through a bed of granular filter material, where the bed moves downwardly and where filtermateπal is taken out from the lower part of the bed, is transported to a washer device (7) whose inlet part for filter material may consist of a wash liquid vessel (8) where liquid and impurities from the washer (wash liquid) are collected and led out through outlet and where the filter material is led into the washer and the liquid that has accompanied the filter material during the transport (transport liquid) is separated and led out, the washed filter material is returned to the top of the bed, WHEREIN the liquid flow from the washer device (7) (wash liquid flow) is kept separate from the liquid flow that accompanies the filter material during the transport (transport liquid flow) by a container (10), equipped with outlet pipe (12), placed in the wash liquid vessel (8) above the washer device (7), filter material and transport liquid are separated in the container (10), the separated filter material falls down into the washer device the liquid levels in the wash liquid vessel (8) and in the container (10) are kept equal . |
| 2. | Method according to the preceding claim, WHEREIN the level is kept the same in the vessel (8) and in the container (10) by means of control means. |
| 3. | Method according to the preceding claim WHEREIN the control means consists of overflow weirs. |
| 4. | Method according to claim 2, WHEREIN the control means consists of control valves. |
| 5. | Method according to any of the preceding claims, WHEREIN the wash liquid flow is returned to the inlet side of the filter. |
| 6. | Method according to the preceding claim WHEREIN the returned flow is led through a particle separator (16). |
| 7. | Method according to any of the preceding claims WHEREIN the transport liquid flow and wash liquid flow are returned to the inlet siαe of the filter, and at least one of the flows is lead through a particle separator. |
| 8. | Method according to any of the preceding claims WHEREIN the transport liquid flow or wash liquid flow or parts of these flows are used for a liquid jet driven filter material pump. |
| 9. | Method according to the preceding claim WHEREIN the flow to the liquid jet pump is led through a particle separator. |
| 10. | Apparatus for filtering a liquid through a bed of granular filter material where the bed moves downwardly and where filter material is taken out from the lower part of the bed, is transported to a wasner device whose inlet part for filter material may consist of a wash liquid vessel (8) where liquid and impurities from the washer (wash liquid) are collected and led out through outlet and where the filter material is led into the washer and the liquid that has accompanied the filter material during the transport (transport liquid) is separated and led out, the washed filter media is returned to the top of the bed, WHEREIN a container (10) is placed in the wash water vessel (8) above the washer device (7) the container is equipped with level control device and bottom sand outlet 1 1 Apparatus according to the preceding claim WHEREIN the level control device consists of overflow weir 12 Apparatus according to any of the preceding claims, WHEREIN the level control device consists of control valves 13 Apparatus according to any of the preceding claims WHEREIN the outlet area of the sand outlet can be controlled by a control body 14 Apparatus according to claim 13 WHEREIN the control body is pressed upward with a force that is adiusted to get an even flow of filter material around the control body 15 Apparatus according to claim 14, WHEREIN the force that presses the control body upwards is accomplished by the buoyance of the liquid 16 Apparatus according to claim 13 WHEREIN tne control body consists of center part (13) of the washer 17 Apparatus according to any of the preceding claims WHEREIN the transport liquid outlet or waεn liquiα outlet is connected to the inlet of the filter 18 Apparatus according to any of the preceding claims WHEREIN a panicle separator is connected to the transport liquid outlet or the wash liquid outlet or both outlets 19 Apparatus according to claim 18, WHEREIN the clean liquid outlet of the separator is connected to the inlet of the filter. |
| 11. | 20 Apparatus according to claim 18, WHEREIN the clean liquid outlet of the particle separator is connected to a pump for drive liquid to the filter material pump. |
Sandfilters with continuous washing of the sand, so called dynamic filters, are used extensively for purification of water. They have several advantages compared with filters with fixed bed, but the dynamic filters used so far have a relatively large reject flow and large power consumption. This can lead to high operating costs, especially if expensive flocculants are used
In a dynamic filter, the sand is transported from the bottom of the bed up to the sand washer by means of compressed air in a so-called air lift pump, or by a water jet in an elector pump In both cases, considerable amounts of water follows the sand up to the washer and this water is mixed with the water from tne sand washer and flows out as reject water
This invention relates to method and apparatus for preventing the water from the washer and the sand pump from being mixed, this makes it possible to reduce the reject water flow as well as to reduce the power consumption
The Austrian patent description A 128/72 depicts a filter where the sand is transported from the bottom of the bed, by a water driven ejector pump, to a hydrocyclone. placed above the bed. where sand and water with impurities are separated The lower outlet of the hydrocyclone is connected to a container which has a bottom outlet for the sand Pure water is fed into the container in order to prevent the reject water from flowing down into the filtrated water A part of the supplied water follows the sand down into the filter and a part follows the water from the hydrocyclone to the retention vessel The vessel is equipped with an overflow pipe for reject water Tne water in the vessel is used for the ejector pump It seems that the method of using a hydrocyclone for cleaning the sand does not give sufficiently clean sand for exacting applications Tne filter naε not gain any commercial significance
The filter according to the Swedish patent 7602999 has because of simple design and good performances become very popular In this filter the sand is transported from the Dottom of tne bed by a compressed air driven pump placed in the center uo to a counter- current washer placed aoove the oed Filtrated water flows up tnrough the washer and meets there the sand that falls down Tne dirty water flows out over an overflow weir
The water that follows the sand through the sand pump is mixed with the wash water and flows out over the same overflow weir This means that the water flow through the washer is affected considerably if the sand flow changes If the sand flow is increased, the amount o * water that follows the sand increases As a result the level in the top of the washer rises and thereby the water flow through the washer is decreased This is contrary to what is desireable, an increased sand flow requires an increased wash water flow The capacity of a compressed air driven sand pump is highly dependent on the pressure difference between inlet and outlet If the flow into the filter varies the sand flow varies too If the filter has to be able to manage flow variations, the reject water flow must be adjusted that there is a large excess of wash water flow under normal conditions, in order to ensure that the sand becomes clean even if the flow to the filter should increase
The present invention provides a method and an apparatus for keeping the water flow from the washer and the waterflow from the sand pump separate and thereby making possible a lower reject water flow and a lower power consumption
Fig 1 shows a filter according to heretofore known technique with the washer modified according to the invention
Fig 2 shows a filter with water jet driven sand pump and separator for impurities
Fig 3 shows a variant of Fig 2
Fig 4 shows a filter with the washer placed outside the filter tank
Fig 5 shows a detail of the invention
The filter according to Fig 1 functions in the following way The water to be filtered is fed through the pipe 1 , distributed round the bed by the circular channel 2 moves up vertically through the bed 3 and flows out over the overflow weir 4
In the lowest part of the sand bed a sand pump 5 is connected which may be driven by air that is supplied through pipe 6 or by water that is supplied through pipe 22 or by a combination of air and water The sand is transported up to a vessel 8, placed above the washer 7, with outlet 4 and overflow weir 9 Filtrated water is pushed up through the washer by the level difference between the overflow weirs 4 and 9
This is known technique from, for exemple Swedish patent 760299 and Swedish patent application 8904138-8
The novelty of this invention is that a container 10 with an overflow weir 11 and with an outlet pipe 12 is placed in the center, above the center part 13 of the washer The container is equipped with a conical bottom and an outlet hole or holes for the sand The container may be placed immediately above the center part 13 in such a manner that a slot 14 is formed The slot is so adjusted that the flow of sand fills the greater part of the slot In order to be able to easily adapt the filter to different operational conditions the slot may be made adjustable for example by making the container 10 or the top of the center part 13 adjustable vertically
The slot can be made automatically adjustable if the top of the center part is made moveable and equipped with a spring or a float that keeps it against the bottom of the container 10 the slot will then be adjusted automatically according to the sand flow Alternatively the container 10 may be placed quite above the center part 13 and equipped with a manually or automatically regulated throttle see Fig 5
If tne overflow weir 11 is set as the same level as the over flow weir 9 the same pressure will be applied to both sides of the slot 14 there will be no flow through the slot Tnis means that the water that follows the sand flows out over the overflow weir 11 and the water from the washer flows out over the overflow weir 9 Instead of the overflow weirs 9 and 11 the outlet pipes 12 and 27 may be equipped with regulating valves In that case, the levels in vessels 8 and 10 must be set to be equal by adjusting the valves manually or automatically
The possibility of keeping the wash water and pump water separate from each other opens several possibilities to improve the performance of the filter, for exaple reαuced reject water flow reduced energy consumption lower installation costs less need for service and higher reliability
The invention makes it possible to introduce a control system that automatically adapts the wash water flow to the filter load This can be accomplished for example, by measuring the flow into the filter and control the wash water flow in proportion to the inflow
The pressure loss through the bed is affected by the inflow and tne degree of contamination of the bed Therefore the pressure loss may be used for control of tne wash water flow
An increase of tne pressure loss means that the inflow nas increased or the amount of impurities in the bed has increaseα In that case the wash water flow must be increased too to avoid that the filtration may become worse
If the pressure loss decreases the wash water flow may also be decreased
An automatic control of the wash water flow can reduce the reject water fiow considerably and thereby reduce operating cost It is no longer necessary to set the wash water flow higher than what is necessary to get the sand clean
The pressure loss through the bed affects the sand flow, but if the filter load varies much, it can be advantageous to introduce an active control so that the sand flow is always adapted to the surface load Thereby the energy consumption of the pump and the wear of sand pump and washer are reduced
The feature of the sand pump that, besides sand, water too is transported leads to its functioning as a pre-washer for the sand The pump water can contain a large amount of impurities Depending on the operational conditions, the pump water or wash water may be more contaminated If the more contaminated water flow is discharged as reject water and the other flow is returned to the inlet of the filter, the reject flow is reduced conciderably The filters which have gained the most use so far have a sand pump that is driven by compressed air It has been shown that the energy cost for the compressed air is considerable, the installation cost for the compressor equippment is high and the service cost may become very high
Now that it is possible to keep pump water and wash water separate in a simple and certain way it is also possible to replace the compressed air driven sand pump with a water jet pump Experiments have shown that it is possible to make a water jet driven sand pump that has considerably lower energy consumption than a compressed air driven pump A water pump is much cheaper, has longer life requires much less service takes less space and is less noisy than a compressor
Fig 2 shows a filter equipped with a water jet pump
A water pump 15 takes water from the inlet side of the filter and pushes it through a nozzle 22 in the lowest part of the bed The water jet from the nozzle pushes up the sand through the pipe 5 The sand falls down through the washer and the pump water out over the overflow weir 11 through the pipe 12, and, if the water is very dirty, through a separator 16 where concentrated impurities are taken out through the outlet pιpe17 The water goes from the separator to a tank 18 with an overflow pipe 19 The water from the washer goes directly to the tank 18 or if the water is very dirty via separator 16 The water is pumped from tank 18 to the inlet of the filter The flow is controlled by the valve 20 so that a suitable reject water fiow flows out of pipes 19 and 20
Fig 3 shows a filter similar to Fig 1 but with the difference that the water from the tank 18 goes directly to pump 15 The reject water flow from pipes 17 and 19 are controlled here by the level of the overflow weirs 9 and 11
In order to prevent the nozzle 22 to be clogged with impurities or sand, it may be made of an elastic material, rubber, polyurethane or similar If something gets stuck in the nozzle the water pressure rises, the nozzle expands and releases what has got stuck The reduction 23 in the inlet of the pump pipe and the conical outlet 24 increase the efficiency of the pump and lower the power consumption
Fig 4 shows that a washer according to the invention may be placed by the side of the fiter tank when a low filter is needed This filter may also be equipped according to Fig 2 and 3
Fig 5 shows an embodiment of the pump water container 10 The container is here equipped with an overflow weir around the full circumference The flow area of the outlet hole is controlled by a control body 26 The control can be accomplished automatically if an upward force is applied against the control body The force is so adjusted that the sand flows evenly around the periphery of the control body The force may be generated by a spring 23 or a float The control body may be shaped as a float
In the above description, 'Water" is used as a general term for the liquid to be filtered, but this invention can be applied to all filterable liquids "Sand" is used as a general term for all granular materials that can be used as filter material, for example natural sand crushed mineral, glass balls and activated carbon