GB1593008A

GB1593008A - Method and apparatus for reducing the resin content of used foundry sand

Info

Publication number: GB1593008A
Application number: GB8229/78A
Authority: GB
Original assignee: FREIER GRUNDER EISEN METALL
Current assignee: FREIER GRUNDER EISEN METALL
Priority date: 1977-03-02
Filing date: 1978-03-02
Publication date: 1981-07-15
Also published as: SE7802366L; FR2382291A1; ES467504A1; DE2708961A1; NL7802329A

Description

(54) METHOD AND APPARATUS FOR REDUCING THE RESIN CONTENT OF USED FOUNDRY SAND (71) WE, FREIER GRUNDER EISEN UND METALLWERKE GmbH, a German Company, of P.O. Box 1220, 5908 Neunkirchen, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns a method and apparatus for reducing the resin content in used foundry sand for the purpose of recycling the sand.

Foundry sand used for making moulds is bonded together by using mainly cold-setting resins, particularly furan- or phenol-based resins. By grinding the broken up moulds after use, the used sand can be re-used for making further moulds, and indeed a certain amount of resin clinging to the grains of sand is desirable for several purposes. If re-cycled a number of times, however, the used sand acquires an undesirably high resin content, and for this reason the resin content of the used sand should be reduced for satisfactory re-use of the sand.

It is the object of this invention to provide a method of reducing resin content of used foundry sand which is cheap in operation and which does not take up a lot of space. A further object of the invention is to provide a compact apparatus for carrying out such a method of used sand regeneration.

According to the invention there is provided a method for reducing the resin content of used foundry sand for the purpose of regeneration. wherein the used sand is subjected to air flow from below which causes fluidization of the sand, and wherein strong jets of compressed air are directed into the used sand whilst it is in this fluidized state to remove resin coatings from the sand.

An important advantage of the invention is that it can be performed without causing damage to the environment.

The invention also provides an apparatus for carrying out the regeneration of used foundry sand by reducing the resin content thereof, the apparatus comprising: a regenerating drum adapted to break up lumps of used sand and to separate metal pieces therefrom while sieving the used sand; a fluidized bed cooler arranged to receive the sifted used sand from the regenerating drum, said cooler including a cooling chamber to cool down the used sand, and a jet nozzle chamber; a number of nozzles for directing jets of compressed air into said nozzle chamber; an air-dust exhaust outlet near the top of the jet nozzle chamber and, substantially half way up the jet nozzle chamber, a discharge outlet for the regenerated used sand.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic side elevation of foundry sand regenerating plant according to one embodiment of the invention; Fig. 2 is a vertical longitudinal section through a fluidized bed cooler forming part of the plant of Fig. 1; Fig. 3 is a partly cut-away plan view of the plant shown in Fig. 2, and Figs. 4, 5 are diagrammatic sectional and plan views respectively corresponding to Figs. 2 and 3 of an alternative form of fluidized bed cooler for use in plant according to the invention.

The regenerating plant shown diagrammatically in Fig. I fits into a pit of the following dimensions: 5 m. long, 2.8 m. wide and 3.3 m.

deep. A feed hopper I including a crusher means or breaker means receives smashed moulds and passes them as smaller pieces to a vibratory conveyor 2 which in turn conveys the fragments to be recycled to a regenerating drum 3. The regenerating drum 3 is of the kind as described in German Offenlegungschrift No. 2445 459 and contains heavy balls which tumble in a rotating barrel to crush the mould fragments as they pass through the drum. The drum 3 has foraminous sieve walls surrounded by a duct into which the used sand produced by crushing the mould fragments in the drum 3 passes, the sand falling into a fluidized bed cooler 4 for further pneumatic regeneration and separation.

The used sand is cooled down in the fluidized bed cooler 4 from 200"C to 29"C and is conveyed by a pneumatic conveyor 5 into a used sand silo.

The above-described components of the regenerating plant are joined together by means of a support structure 6 comprising six supports and a number of connecting members. Where the regenerating plant is installed above floor level, it is possible to fit casing walls quite close to these supports to enclose the plant. Such enclosure substantially reduces the escape of dust and also muffles the considerable noise made by the regenerating drum 3 in operation of the plant. In order to avoid dust emerging through the opening of the feed hopper 1, a vacuum is maintained inside the casing of the plant and air is constantly drawn over an exhaust filter 7. In the illustrated embodiment an electrical switch- and control unit 8 is mounted inside the casing. The unit 8 could also be arranged outside the casing.

Below the regenerating drum 3 there is located a collecting bin 9 for receiving lumps and metal parts which cannot be broken up and which are separated from the foundry sand in the regenerating drum 3.

As can be seen in Fig. 1, the compact construction of the regenerating plant results from the fact that the fluidized bed cooler 4 is placed directly below the regenerating drum 3, or rather below its sifting area, and extends towards the feed hopper 1 and its vibratory conveyor 2, both of which do not extend downwards as much as the regenerating drum 3. Since the input into the pneumatic conveyor 5 is effected through a chute, the said conveyor 5 has to be arranged below the fluidized bed cooler 4; otherwise it would be possible to reduce the overall height of the plant even more.

rig. 2 shows a longitudinal section of the fluidized bed cooler 4. The cooler 4 is provided at one end with a jet nozzle chamber 14 also shown in plan in Fig. 3 from above. The fluidized bed cooler 4 has a box shaped housing 15 which has an enlarged height over the area of the jet nozzle chamber 14, the housing 15 being elsewhere of square cross section. The base of the housing 15 is provided with air chambers 16 above which is a fluidized bed supporting floor 17.

The fluidized bed supporting floor 17 may be provided with pores to allow air flow. but equally useful are small boreholes 18, particularly when these are directed diagonally upwards towards the chamber 15. Adjacent the jet nozzle chamber 14 and above the air chamber 16 is a cooling chamber 13 provided with cooling coils 19. The inlet and outlet for cooling water which flows through the coils 19 are indicated by 20. An opening 21 in an upper wall of the chamber 13 forms a connection between the chamber 13 and the regenerating drum 3.

The chambers 13 and 14 are separated by a transverse vertical wall 22 which serves as a barrier for the fluidized or flowing stream of used sand. Opposite the wall 22 in the chamber 14 there are six nozzles 23 to 28 which are arranged in pairs at three different levels one above the other in an external wall of the chamber 14. As can be seen in Fig. 3 the jets of each pair of nozzles intersect each other at points 29, 30, 31 at a certain distance from the wall 22, and also at a certain distance from one another. The jets from the nozzles 23 and 26 meet at point 29, the jets from the nozzles 24 and 27 meet at point 30 and the jets from the nozzles 25 and 28 meet at point 31.The choice of how many jets from the pairs of nozzles are to be used is dependent upon the rate of flow and upon how much of the resin content is to be removed from the used sand, that is, the number of jets can be either increased or reduced to only one single working pair. The direction of the jet is horizontal or inclined to the horizontal.

Above the nozzles 23 to 28 there is a downwardly inclined outlet chute 32 for the treated used sand, which leads to the pneumatic conveyor 5, and an exhaust outlet 33 which leads to a dust-collecting device, not shown.

The operation of the regenerating plant of Figs. 1 to 3 is as follows: Foundry waste or broken up foundry moulds are emptied into the feed hopper 1. Due to the vibration of the feed hopper 1, a partial breaking up of the moulds is already achieved here, preventing bulky metal pieces from entering further into the plant. The vibratory conveyor 2 carries the lumpy sandy material into the regenerating drum 3, where the lumps of sand are crushed and a further separation of sand and any residual metal takes place. Whilst the sand is allowed to fall through the sieve walls of the regenerating drum 3 the pieces of residual metal are eventually passed, due to the accumulation of material, towards an ejection opening which is situated in the barrel shell above the collecting bin 9, allowing the metal pieces to fall into the said collecting bin 9. The sieved used sand falls into the fluidized bed cooler 4 where it is cooled down to a temperature below 30on, the crushed material of the broken up moulds having initially a substantially higher temperature of over 200 C. The air which passes through the floor 17 of the fluidized bed makes the sand fluid and also creates in the fluidized bed a certain eddy-motion, as a result of which the continually incoming used sand can make good contact with the cooling coils 19. The diagonal position of the boreholes 18 in the floor 17 furthermore favours a drifting of the flowing used sand of the fluidized bed towards the left, as viewed in the drawing, so that the used sand becomes packed against the wall 22 which acts as a weir over which the sand streams.

The open lower end of the outlet chute 32 is situated lower than the top of the wall 22 so that the flowing used sand moves towards this outlet; before reaching the outlet chute, however, the sand is caught by the stream of the compressed air from the nozzles 23 to 28 and, as shown in Fig. 2, is dragged along with the compressed air jets towards the right. The sand thus entrained rubs against the surrounding sand as well as against the sand that is blown crosswise from the nozzle jets, particularly in the vicinity of the jet intersection points 29, 30, 31, as shown in Fig. 3. This rubbing action between the grains of sand causes the resin deposits on the sand grains to be rubbed off, the resin particles being entrained like dust in the outflowing air stream and sucked up through the exhaust outlet 33.In this way the object of reducing the resin content of the used sand is effectively achieved.

Fig. 4 and Fig. 5 show an alternative embodiment of a fluidized bed cooler 40 according to this invention, whereby corresponding parts carry the same reference numerals as in the drawings of the first embodiment shown in Figs. 1 to 3. The cooling chamber 13 and the jet nozzle chamber 14 are in this embodiment arranged one above the other rather than side by side.

Instead of one transverse wall 22 a row of, for example, seven transverse dam walls 41, 42 is provided, these walls being at different heights and depths in the chamber 13 and arranged alternatively, so as to force the fluidized material to flow in a zigzag stream through the fluidized bed cooler, as shown by the arrow 43 in Fig. 4.

Inside the jet nozzle chamber 14 there is a closed tubular frame 44 along the opposite longitudinal sides of which nozzles 45 and 46 respectively are arranged. Compressed air is fed into the tubular frame 44, through an inlet duct 47, and then escapes through the two rows of nozzles 45, 46 so that the compressed air jets are directed so as to confront one another. In this way the grains of used sand rub against each other, rubbing off some of the resin coating from the grains.

the detached resin particles being entrained as dust along with the outflowing air. This method also reduces the resin content in the used sand, as desired.

Instead of cooling coils 19, the cooling chamber 13 is the embodiment of Figs. 4 and 5 provided with rows of vertical cooling plates 49 which extend in a longitudinal direction through the fluidized bed cooler 40 and could, for example, be eight in number.

The cooling plates 49 and the dam walls 41, 42 are arranged like a lattice whereby the dam walls 41, 42 have alots therein in which the cooling plates 49 are accommodated, the walls 41, 42 being in effect comb-shaped. A water inlet manifold 50 and a water outlet manifold 51 are connected to opposite ends of the cooling plates 49 for circulating water through the plates, from left to right as viewed in Fig. 5.

The operation of the fluidized bed cooler 40 corresponds with the operation of the fluidized bed cooler 4 in embodiment described with reference to Figs. 1 to 3 and needs therefore no further explanation.

WHAT WE CLAIM IS: 1. A method for reducing the resin content of used foundry sand for the purpose of regeneration, wherein the used sand is subjected to air flow from below which causes fluidization of the sand, and wherein strong jets of compressed air are directed into the used sand whilst it is in this fluidized state to remove resin coatings from the sand.

2. A method as claimed in Claim 1, wherein the jets of compressed air intersect each other when penetrating the fluidized used sand.

3. A method as claimed in Claim 1 or Claim 2, wherein the planes of the compressed air jets are substantially horizontal.

4. A method as claimed in any of Claims 1 to 3, wherein the jets of compressed air are directed into the fluidized sand at different levels.

5. Apparatus for carrying out the regenertion of used foundry sand by reducing the resin content thereof, the apparatus comprising: a regenerating drum adapted to break up lumps of used sand and to separate metal pieces therefrom while sieving the used sand; a fluidized bed cooler arranged to receive the sifted used sand from the regenerating drum, said cooler including a cooling chamber to cool down the used sand, and a jet nozzle chamber; a number of nozzles for directing jets of compressed air into said nozzle chamber; an air-dust exhaust outlet near the top of the jet nozzle chamber and, substantially half way up the jet nozzle chamber, a discharge outlet for the regenerated used sand.

6. Apparatus as claimed in Claim 5, wherein the nozzles are arranged in pairs and wherein the jets of compressed air from the nozzles intersect at specific points in use of the apparatus.

7. Apparatus as claimed in Claim 5 or Claim 6, wherein the nozzles are arranged at different levels vertically in the nozzle chamber.

8. Apparatus as claimed in Claim 5, Claim 6 or Claim 7, wherein the jet nozzle chamber lies above the cooling chamber within the fluidized bed cooler.

9. Apparatus as claimed in Claim 8, wherein the cooling chamber has internal transverse dam walls arranged at different

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. becomes packed against the wall 22 which acts as a weir over which the sand streams. The open lower end of the outlet chute 32 is situated lower than the top of the wall 22 so that the flowing used sand moves towards this outlet; before reaching the outlet chute, however, the sand is caught by the stream of the compressed air from the nozzles 23 to 28 and, as shown in Fig. 2, is dragged along with the compressed air jets towards the right. The sand thus entrained rubs against the surrounding sand as well as against the sand that is blown crosswise from the nozzle jets, particularly in the vicinity of the jet intersection points 29, 30, 31, as shown in Fig. 3. This rubbing action between the grains of sand causes the resin deposits on the sand grains to be rubbed off, the resin particles being entrained like dust in the outflowing air stream and sucked up through the exhaust outlet 33.In this way the object of reducing the resin content of the used sand is effectively achieved. Fig. 4 and Fig. 5 show an alternative embodiment of a fluidized bed cooler 40 according to this invention, whereby corresponding parts carry the same reference numerals as in the drawings of the first embodiment shown in Figs. 1 to 3. The cooling chamber 13 and the jet nozzle chamber 14 are in this embodiment arranged one above the other rather than side by side. Instead of one transverse wall 22 a row of, for example, seven transverse dam walls 41, 42 is provided, these walls being at different heights and depths in the chamber 13 and arranged alternatively, so as to force the fluidized material to flow in a zigzag stream through the fluidized bed cooler, as shown by the arrow 43 in Fig. 4. Inside the jet nozzle chamber 14 there is a closed tubular frame 44 along the opposite longitudinal sides of which nozzles 45 and 46 respectively are arranged. Compressed air is fed into the tubular frame 44, through an inlet duct 47, and then escapes through the two rows of nozzles 45, 46 so that the compressed air jets are directed so as to confront one another. In this way the grains of used sand rub against each other, rubbing off some of the resin coating from the grains. the detached resin particles being entrained as dust along with the outflowing air. This method also reduces the resin content in the used sand, as desired. Instead of cooling coils 19, the cooling chamber 13 is the embodiment of Figs. 4 and 5 provided with rows of vertical cooling plates 49 which extend in a longitudinal direction through the fluidized bed cooler 40 and could, for example, be eight in number. The cooling plates 49 and the dam walls 41, 42 are arranged like a lattice whereby the dam walls 41, 42 have alots therein in which the cooling plates 49 are accommodated, the walls 41, 42 being in effect comb-shaped. A water inlet manifold 50 and a water outlet manifold 51 are connected to opposite ends of the cooling plates 49 for circulating water through the plates, from left to right as viewed in Fig. 5. The operation of the fluidized bed cooler 40 corresponds with the operation of the fluidized bed cooler 4 in embodiment described with reference to Figs. 1 to 3 and needs therefore no further explanation. WHAT WE CLAIM IS:

1. A method for reducing the resin content of used foundry sand for the purpose of regeneration, wherein the used sand is subjected to air flow from below which causes fluidization of the sand, and wherein strong jets of compressed air are directed into the used sand whilst it is in this fluidized state to remove resin coatings from the sand.

heights alternately, whereby the used sand is forced to flow along a zigzag path through the said chamber.

10. Apparatus defined in Claim 8 or Claim 9, wherein the cooling chamber has parallel cooling plates which extend in the cooling chamber in the direction of the discharge outlet for the regenerated used sand.

11. Apparatus as claimed in any of Claims 5 to 10, wherein the cooling chamber has a floor supporting the fluidized bed, the floor having diagonal boreholes therein, and the axes of said boreholes being inclined to the vertical in the direction of the discharge opening for the regenerated used sand.

12. Apparatus as claimed in any of Claims 5 to 11, wherein the fluidized bed cooler is situated below the regenerating drum and its inlet forms with the drum and said cooler a compact unit, and including a common support structure for said unit.

13. Apparatus as claimed in Claim 12, wherein the support structure is adapted for installation in a pit.

14. Apparatus as claimed in Claim 12, including a casing cladding said support structure.

15. Apparatus for the regeneration of used foundry sand substantially as herein described with reference to and as shown in Figs. 1 to 3 or Figs. 4 and 5 of the accompanying drawings.