GB2381483A

GB2381483A - Floatation separation with nozzles and weir

Info

Publication number: GB2381483A
Application number: GB0121854A
Authority: GB
Inventors: Alan Valentine; Donald Roger-Brown
Original assignee: WASTE MECHANICS Ltd
Current assignee: WASTE MECHANICS Ltd
Priority date: 2001-09-10
Filing date: 2001-09-10
Publication date: 2003-05-07
Also published as: GB0121854D0

Abstract

A separator apparatus comprises a water tank 100 with a separation chamber, upper and lower water nozzles 110,111 and a weir 115. The water nozzles 110, 111 being positioned such that in use to separate material 150, they direct less dense particles 152 over the weir 115, whilst allowing more dense particles 151 to drop to the bottom of the separation chamber. Also disclosed is an apparatus as already described, further comprising a conveyor 172 to transport the denser particles 151 away. Also disclosed is a method consistent with the normal use of the first apparatus described. Further disclosed is a separator comprising an upwardly extending chute 100, a pump (125, fig.4) and a weir 115. The first/second apparatus and method maybe used for the floatation separation of the component parts of general builders rubble, containing such as plastics, cardboard, clipboard, to recycle elements of the rubble as hoggin, or low grade concrete filler.

Description

Separator The present invention relates to a separator for separating objects of different densities or weights using a water tank. and in particular for separating waste material such as builders rubble into different components.

Currently much of the material in builders rubble. skip waste. etc. goes in landfill sites because it contains contaminants such as plastics. cardboard. chipboard. wood. etc. and it cannot be recycled while containing these contaminants. This is wasteful. since once the contaminants are removed. the rubble can be recycled as hoggin or low grade concrete filler. It is also bad for the environment. as wood pieces decompose to produce flammable gas which is detrimental to the atmosphere. and many plastics will not readily decompose.

One method of separating such material is by immersing it in water, so that less dense components float to the surface and denser components sink to the bottom. This basic method. along with various improvements. is well known in the prior art. For example.

EP0325324 and EP0322688 show the use of a nozzle of water within the separation tank to increase the buoyancy of the light fraction. EP0325324 and US4375264 show a water separator in which the heavy fraction drops onto a conveyor belt for removal from the tank. EP0325324 shows the use of a filter to filter the material prior to separating its components in the water separator.

The present invention provides a separator apparatus for separating particulate material according to particle density. comprising a water tank with a separation chamber. upper and lower water nozzles inside the separation chamber. the upper water nozzle being situated higher in the separation chamber than the lower water nozzle. and a weir. wherein the water nozzles are positioned such that when in use to separate material. they direct less dense particles over the weir. whilst allowing more dense particles to drop to the bottom of the separation chamber. Preferably. the nozzles are adjustable for

flow rate and angle. such that different settings may be used for different separation requirements.

This allows the lighter contaminants to be removed from builders'rubble and skip waste.

Other aspects and features of the invention are set forth in the accompanying claims.

The invention will now be further described by way of example only. with reference to the accompanying drawings. in which: Figure ! shows a top view of a preferred embodiment of the invention: Figure 2 shows a side view of the embodiment of figure ! : Figure 3 shows an end view of the embodiment of figure 1. including a hydrocyclone : Figure 4 shows connections between a pump and the nozzles of the embodiment of figure 1 : Figure 5 shows an enlarged view of a portion of figure 2 : Figure 6 shows a side perspective view of the embodiment of figure ! : Figure 7 shows a top perspective view of the embodiment of figure 1 : and Figure 8 shows an example of a hydrocyclone which is suitable for use in the present invention.

Referring to figures 1. 2 and 3. the apparatus comprises an inner water tank 100 with an open top. The rear 170 and side 171 walls of the tank 100 are vertical. The front wall 172 slopes downwards and inwards. also forming a floor to the tank 100. which gives the tank 100 a narrow base and a wider top surface. The inner water tank 100 is positioned inside an outer water tank 101. which in turn is positioned inside a support frame 102. The support frame has wheels 103 to allow the unit to be transported more easily. Figure 6 is a photograph of the unit. clearly showing the tanks 100. 101 and support frame 102. Extra supports 104 are optional. and are not included in the apparatus shown in the photograph.

The inner water tank] 00 has a separation area. with two water nozzles 110. Ill attached to its rear wall 170. and a weir 115. Figure 5 shows a more detailed view of this separation area. When material is dropped into the tank 100. water flow from nozzles es 110. Ill directs lighter particles over the weir I I 5. whilst heavier particles drop to the bottom of the tank 100.

A feed container 105 is positioned at the rear end of the machine. with one of its ends held above the inner tank 100. above the position of the water flow from the water nozzles. The feed container 105 is supported partly by the support frame 102. and partly by the edge of the inner water tank] 00. The floor of the feed container 105 comprises a feed elevator ! 06. which is an upwardly sloping conveyor belt to transport material over the edge of the feed container 105 and into the inner water tank 100. where it is separated into more and less buoyant fractions with the aid of the water flow from nozzles HO. III. The feed elevator has a variable speed drive which allows the trajectory of material to be set as it comes off the belt. This results in a more controlled. steady delivery than would be provided by e. g. a delivery chute. It allows the trajectory to be changed depending on the type of material which is being put into the tank.

The total water flow from the nozzles 110. 111 is approximately 100 I/sec. and this is divided between the top I 10 and bottom 111 nozzles. by adjustable valves 27. 128.

The high velocity of the water. plus the inclusion of a proportion of cement/brick dust in suspension enables the separator to separate out contaminants that are slightly heavier than water. as well as those that float in water. However. the inclusion of brick dust is not crucial. and the apparatus will still function without it.

Each nozzle I 10. 111 is fitted on a pipe) 82. ! 83. and the water is pumped into the pipe from both sides. Water is pumped out from a slot 180. 181 in each nozzle using a pump 125. Figure 4 shows the configuration of the connections between the pump 125 and nozzles 11 0. 11 1. Valves 197. 1 28 are provided to allow the flow to be regulated. The water to be pumped through the nozzles 110. Ill is obtained from the outer tank 101.

The bottom part of the outer tank 101 has a square box shape 193. with a mesh on top of the box 93. The mesh prevents any stones from passing through. The inlet to the pump

is located inside this box 193. The box 193 has a door 192 which can be opened during maintenance of the apparatus to access the inside of the tank.

The slots 180. 181 are adjustable in angle and in width. An alternative to having adjustable slots is to have a range of replaceable nozzles. where the correct nozzles are fitted for different applications. For example. if a mixture has to have a large proportion of contaminants removed. it may need slot sizes which result in fractionation into a small amount of decontaminated material and a large amount of waste with impurities.

However. if it is not quite so important to remove all the waste. the mixture may be separated into a fraction with a large amount of material containing a few impurities. and a small amount of material containing a very high level of impurities. Also. to separate a mixture containing a lot of cement dust. it may be necessary to use different slots than with a mixture containing only large particles. as the cement dust would help increase the buoyancy of the lighter particles.

For any particular mixture. the best slot sizes may be found be trial and error. then those settings repeated the next time a similar mixture is to be separated in the same way.

Preferably. the length of the slots 180. 181. in the direction parallel to the axis of the pipe 182. 183. is fixed, but the width of the slots is adjustable.

It will be appreciated that the rate of flow of water from the nozzles 110. Ill may be adjusted by changing the pumping rate of pump 125. the feed of the water to the nozzles. and optionally providing separately controllable pumps for the nozzles.

A primary application of the apparatus of the invention is to clean up a mixture of stones and pieces of brick. etc. This mixture may include bits of slab and pieces of kerbstone of up to around 75 cm long. Preferred settings for this are with the top slot 180 between 6 and 12mm wide. and the bottom slot 181 much wider. 10 to 25mm. A smaller gap gives a higher force of nozzle. This causes a slower laminar flow from the bottom slot 181. and a faster nozzle from the top slot 180. The resultant heavy fraction is a clean mixture of stone. with sizes from about 5 mm upwards. The light fraction may contain some small stones.

Another application of the apparatus of the invention is to clean up chipped wood to remove stone. glass. nails, metal, etc. For this application. the velocity of the top nozzle I 10 should be reduced by using the lower valve 128 to reduce the flow. The top slot 180

may be opened further to give a slower velocity of water from the nozzle. A top slot 180 y width of around 15 mm may be used for wood chips. The bottom slot 181 will still be fairly wide.

The upward flow from bottom nozzle I I I is to direct those objects which are slightly more dense than water upward. and is preferably generally laminar. However in practice. eddy currents in the tank 100 may drag these objects back down. This problem may be reduced by making the convex section 6] of the wall bigger and closer to the top nozzle.

The top nozzle is more effective at adjusting the cut-off point. i. e. the average density or size of particle which will be swept across the weir. With the top nozzle turned up high. the aggregates come out very clean-with no wood or plastic. but there are some small stones in the light fraction (an acceptable amount). By turning the top nozzle down. it is possible to go right through the range to the point where there is no stone in the light fraction.

Ideally. the nozzles HO. ! 1 ! should set up a standing wave across the weir l l S where the water moves, but the wave remains stationary. As shown in figure 7. the wave is quite turbulent. and looks more like a breaking wave than a standing wave. However. by fine tuning of the shape of the tank and the settings of the nozzles 110. 111. the amount of turbulence can be reduced.

It is preferable to have an even flow of water from the slot] 80. 18]. along the length of the nozzle 184. 185. To prevent most of the water coming out the middle of the slot 180. 18 1. and less from the two sides. it is possible to form the pipe 182. ! 83 as a plenum chamber. and give a more even water flow along the length of the slot 180, 18 1.

The bottom surface of the inner tank 100 is a conveyor belt 120. driven by motor 121.

The conveyor belt 120 picks up the denser particles which drop to the bottom of the

inner tank 100. and transports them out of the tank. The conveyor belt forms a barrier between the inner] 00 and outer 101 tanks. At the boundary between the conveyor belt

120 and the rear wall 170 of the inner tank 100. there is a slit. which is covered by a rubber flap 190. This flap 190 reduces the water flow between the inner 100 and outer 101 tanks. The water level is therefore greater in the inner tank 100 than in the outer tank 101. due to the action of the pump 125.

Less dense particles which are transported over the weir are deposited onto a dewatering conveyor 116. which has a mesh surface to allow water to drain through. and is driven by a motor 117. When water passes through the mesh surface. it flows through into a channel 191. and then into the outer tank 101.

Containers such as skips may be placed below the end of each conveyor 120. 116 to collect the light fraction and the heavy fraction. Alternatively. another conveyor belt may be positioned below the end of the conveyors 120.116 of the separating apparatus to collect each fraction and transport it into a lorry.

The rear wall 170 of the tank between the top 110 and bottom 111 nozzles has a convex shape z The channel is therefore wider at the bottom. narrower in the middle. and wider again at the top. One nozzle is in the wider part at the bottom. and the other nozzle is in the wider part at the top. This improves the water flow. giving a more uniform and faster water flow upwards. and it reduces turbulence and eddy currents which drag material downwards. Other ways of altering the shape of the tank are also possible. although these must take account of the fact that large pieces of kerbstone may be falling past. so they must be of a suitably strong construction. Optionally. a barrier ! 60 may be provided, extending from the bottom of the weir 115. This barrier 160 stops slightly short of the conveyor belt 120. so that a significant amount of water from the lower nozzle 111 goes upwards rather than along the surface of the conveyor belt 120. but heavy particles 151 which land on the conveyor belt 120 may still pass below the barrier 160. The barrier 160 has a significant effect when the lower nozzle 111 is directed towards it. but normally the lower nozzle 111 will be more upwardly directed than this.

The water may be cleaned by hydrocyclones 140. A second pump 126 pumps water through the hydrocvclones 140 and back into the tank. as shown in figure 3. The material 146 removed by the hydrocvclones 140 is deposited into a tank 145. The hydrocyclones 140 are of standard design. and can be obtained from a number of different manufacturers. In the preferred embodiment of the invention. they will only need to be switched on occasionally. when the water gets particularly dirty. or for half an hour at the end of the day. This will prevent problems due to the silt in the water settling overnight, and hardening in the bottom of the tank or pump.

An example of a suitable hydrocyclone is a ten inch hydrocyclone. shown in figure 8.

The hydrocyclone has a cone section 200 with a lightweight stainless steel shell. which attaches to a feed chamber 20 L The feed chamber 201 has a water inlet 202 on its side and a water outlet 205 fits on top. A mounting rail 204 with hinged bolts 203 may be used to mount the hydrocyclone in position. At the bottom of the body. the hvdrocyclone has a wear resistant liner 206. onto which a spigot cap 208 is fitted using a quick release clamp 207. This hydrocyclone has cut points in the 18 to 40 micron size range with capacities between 20 and 110 m3/h. The performance of the hydrocyclone can be controlled by its operating pressure. and the diameters of the outlets. A hydrocyclone with operating pressure in the range of 0.7 to 2.0 bar would be suitable for use in the present invention. Finer cut points and higher capacities can be achieved by fitting a body extension between the cone section 200 and the feed chamber 201 of the hydrocyclone.

Evaporation may occur from the tanks. and water may be lost via the hydrocyclones and via the light and heavy fractions of the material which is removed from the tank. To keep the tank topped up. a ballcock (not shown in the figures) is provided in the outer tank to control its water level. The upward slope of the conveyor belt 120 allows drainage of the material in the heavy fraction and reduces water loss from the tank.

Claims

CLAIMS : 1. A separator apparatus for separating particulate material according to particle density. size or weight. comprising a water tank with a separation chamber. upper and lower water nozzles inside the separation chamber. the upper water nozzle being situated higher in the separation chamber than the lower water nozzle. and a weir. wherein the water nozzles are positioned such that when in use to separate material. they direct less dense particles over the weir. whilst allowing more dense particles to drop to the bottom of the separation chamber.

2. A separator apparatus as claimed in claim 1. wherein the nozzles are adjustable for flow rate and/or angle. such that different settings may be used for different separation requirements.

3. A separator apparatus as claimed in claim 1 or 2. further comprising removal means for removing from the tank said less dense material which has been transported across the weir.

4. A separator apparatus as claimed in claim 1. 2 or 3. further comprising removal means for removing said more dense material from the bottom of the separation chamber.

5. A separator apparatus as claimed in claim 3 or 4. wherein the or each said removal means comprises a conveyor belt.

6. A water separator as claimed in any one of the previous claims. further comprising a hydrocyclone to remove fine silt from the water..

7. A water separator as claimed in claim 6. wherein a plurality of hydrocyclones are connected in series to remove fine silt from the water.

8. A water separator as claimed in claim 7. wherein said hydrocyclones are all identical.

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9. A water separator as claimed in claim 8. wherein said hvdrocyclones can remove different ranges of particle size from the water.

10. A water separator as claimed in any one of the previous claims. further comprising feeding means for feeding unsorted material into the tank.

11. A water separator as claimed in claim 10. wherein said feeding means comprises an upwardly sloping conveyor belt.

12. A water separator as claimed in any one of the previous claims. wherein said separation chamber has a vertical channel shape having a narrower cross-section in the middle than at the ends. and wherein said nozzles are positioned above and below said narrower section.

13. A water separator as claimed in any one of the previous claims, wherein said separation chamber comprises a convex wall.

14. A water separator as claimed in claim 4. further comprising a barrier above the removal means for more dense material, said barrier defining a gap above said removal means for more dense material. wherein said gap is sufficiently large to allow passage of said more dense material. but sufficiently small to prevent a significant part of the water flow from said lower nozzle from passing through.

15. A water separator as claimed in claim 3. wherein said removal means for said less dense material comprises a dewatering conveyer. said dewatering conveyor having a mesh surface to allow water to drain through.

16. A water separator as claimed in any one of the previous claims. wherein said nozzles comprise slits through which the water passes, and said slits are adjustable in width and/or angle.

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17. A water separator as claimed in any one of the previous claims. wherein said nozzles have a range of replaceable nozzles. such that different nozzles may be fitted for different applications.

18. A water separator as claimed in any one of the previous claims. wherein each said nozzles is mounted on a pipe. with water entering both ends of the pipes. and passing through the nozzles.

19. A water separator as claimed in claim 18. wherein said pipes have a plenum tank mounted behind them to give a substantially even flow from along the length of the nozzle outlet.

20. Apparatus for recovering and separating solids of different densities. sizes or weights. the apparatus comprising an upwardly extending chamber filled. in use. with water. a conveyor at the bottom of the chamber and extending out of the chamber for conveying more dense solids from the chamber. solids to be separated being fed into the chamber from the top. a weir at the top of the chamber. less dense solids being conveyed over the weir by a flow of water. wherein a first nozzle is provided at a lower position in the chamber. water being pumped through the nozzle to carry less dense material upwards. a second nozzle is provided at an upper position in the chamber. water being pumped through the nozzle to carry the less dense material over the weir.

2 !. A method of recovering and separating solids of different densities. sizes or weights. comprising the steps of providing a water tank with a weir at the top. and with upper and lower water nozzles inside the tank. the upper water nozzle being situated higher in the tank than the lower water nozzle. wherein the water nozzles are positioned such that when in use to separate material. they direct less dense. smaller or lighter solids over the weir. whilst allowing more dense. larger or heavier solids to drop to the bottom of the separation chamber : dropping a mixture of said solids into the tank. such that the less dense. smaller or lighter particles are directed across the weir: and

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separately collecting the fraction of the mixture which has passed across the weir. and the fraction of the mixture which has dropped to the bottom.

22. A separator for separating articles of different buoyancy, the separator comprising an upwardly extending chute into which the articles are tipped from above. a pump for creating. in use. an upward flow of water in the chute to carry more buoyant articles upwards. and a weir at the top of the chute. the water. in use. overflowing the weir to carry more buoyant articles out of the chute.

23. A separator as claimed in claim 22. wherein a nozzle is provided at the top of the chute for directing water and more buoyant articles over the weir.

24. A separator as claimed in claim 22 or 23. wherein the chute is narrowed in cross-section between upper and lower ends of the chute.

25. A separator as claimed in claim 22. 2. 3 or 24. wherein a water nozzle is provided at a lower end of the chute. and the pump pumping water through the nozzle to form the upwardly directed flow of water in the chute.