EP0482161A1 - Thermal reclamation method. - Google Patents
Thermal reclamation method.Info
- Publication number
- EP0482161A1 EP0482161A1 EP91908839A EP91908839A EP0482161A1 EP 0482161 A1 EP0482161 A1 EP 0482161A1 EP 91908839 A EP91908839 A EP 91908839A EP 91908839 A EP91908839 A EP 91908839A EP 0482161 A1 EP0482161 A1 EP 0482161A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- mixture
- fluidised bed
- bed
- fed
- feeding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
- B22C5/08—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by sprinkling, cooling, or drying
Definitions
- This invention relates to a method of and apparatus for thermally reclaiming a material, such as foundry sand.
- Used foundry sand is normally subjected to reclamation so that it can be re-used in foundry processes.
- reclamation can take the form of mechanical attrition, whereby the sand is broken down into grain-size particles.
- used foundry sand contains a high proportion of chemical bonding agents, notably phenolic resins, and after a while these agents reach such a level that the sand becomes unusable, even with mechanical reclamation.
- the sand/bonding agent mixture is fed into the fluidised bed from above, and will comprise a mixture of relatively light particles (i.e.
- the velocity of the air passing through the fluidised bed (which must be above the minimum required to maintain fluidity) is such that it exceeds the settlement rate of the relatively light
- the relatively light particles tend to comprise a high proportion of the bonding agent (up to 50% in some cases), they have a high calorific value and will burn in the hood or stack, subject to there being sufficient oxygen
- the relatively heavy particles are also highly volatile, with the result that ignition tends to occur spontaneously as the particles impinge upon the top of the fluidised bed, so the bulk of the combustion takes place in the top region of the bed. This not only acts against the supposed self-sustaining reaction of the combustion, but also adds to the heating effect on the hood and stack. These effects combined give rise to excessive heat in the flue gases, and indeed it is sometimes the case that the flue gases end up hotter than the fluidised bed itself.
- pre-heating of the sand/bonding agent mixture can make the sand sticky and unmanageable and can also give rise to the emission of noxious vapours. Also, the amount of heat recoverable from the hot flue gases far exceeds that needed for pre-heating the air for the fluidised bed.
- heat exchanges are high maintenance items, and the dust entrained in the flue gases tends to adhere to the heat-exchange surfaces, causing a build-up which must be cleared periodically.
- the silos or hoppers containing the mixture must be provided at an elevated location for gravity feed of the material into the bed. This in itself gives rise to a degree of inconvenience.
- a method of thermally reclaiming a base material such as foundry sand
- a base material such as foundry sand
- incinerated in a fluidised bed comprising feeding said mixture directly into a lower part of the fluidised bed.
- said mixture is fed into the fluidised bed from beneath the latter.
- said mixture is fed (preferably continuously) to a confined space beneath the fluidised bed by means of a mechanical convevor.
- said mixture can be fed to the fluidised bed by a pneumatic conveyor, and is preferably injected into the bed at substantially the same level as the fluidising air/gas mixture.
- a plurality of feeds are preferably provided which operate in sequence. For example, where two such feeds are provided, these can operate alternately.
- said mixture is mechanically comminuted and dust from the comminution process is mixed with said mixture for feeding to the fluidised bed.
- thermal reclamation apparatus for
- the feeding means includes a mechanical
- the feeding apparatus can include a
- pneumatic conveyor having feed pipes which preferably terminate at substantially the same level in the fluidised bed as nozzles which feed air/gas mixture into the bed.
- the feeding means includes a plurality of pneumatic conveyors each of which feeds said mixture to the fluidised bed in batches, and means to operate the
- Figure 1 is a schematic view of one embodiment of thermal reclamation apparatus, according to the present invention.
- Figure 2 is a schematic view of a second embodiment of thermal reclamation apparatus, according to the present invention.
- Figure 3 shows a practical version of the apparatus depicted in Figure 2.
- apparatus comprises a furnace 10 containing a fluidised bed II to which an air/fuel gas mixture is supplied by way of a manifold 12, pipes 12 and nozzles or bubble caps 14. Above the fluidised bed 11 the furnace has a hood 15 and a stack 16 through which flue gases can pass, while to one side of the bed there is an exit chute 17 through which material can be drawn off from the top of the bed.
- material to be reclaimed such as a comminuted mixture of foundry sand and phenolic resin bonding agent
- a mechanical conveyor 19 such as a screw conveyor
- the continuous feed of this material causes the mixture to rise progressively through the space 20 and to enter the fluidised bed 11 from below, through the interstices between the bubble caps 14. This ensures that all of the material, i.e. both relatively light and relatively heavy particles, is passed through the full body of the fluidised bed 11 and that therefore the resin bonding agent is properly incinerated within the bed itself.
- the fluidised bed can be arranged to achieve the theoretical self-supporting combustion
- FIG. 2 shows a second embodiment of the apoaratus wherein the sand/bonding agent mixture is fed to the fluidised bed 11 by means of a pneumatic conveyor 22. More particularly, a pressure vessel 23 is periodically charged with the mixture from a silo/hopper 24 via a valve 25. The oressure vessel 23 communicates with a manifold 25, which in turn communicates with pneumatic conveyor lines 27 by way of respective valves 28. The lines 27 terminate at resoective injection nozzles 29 disposed at approximately the same level as the bubble caps 14.
- the valve 25 is closed and the vessel 23 is pressurised so that the mixture is conveyed pneumatically to the bed 11 through the lines 27 and the nozzles 29.
- the valve 25 is closed and the vessel 23 is pressurised so that the mixture is conveyed pneumatically to the bed 11 through the lines 27 and the nozzles 29.
- sand/bonding agent mixture is fed directly into the lower part of the fluidised bed 11 and passes upwardiy
- bonding agent is properly incinerated in the bed itself, and there is no combustion in the space above the bed.
- This embodiment also has the added advantage that oxygen is fed into the bed not only in the normal manner with the fuel gas through the bubble caps 14, but also in the air employed in the pneumatic conveyor 22. Injection of the material into the bed can be made as uniform as possible (to avoid the creation of any cold spots) by providing as many injection nozzles 29 as is practicable across the whole area of the fluidised bed.
- processed material i.e. clean sand
- exit chute 17 as the level of the top of the fluidised bed 11 rises above a weir 21, while material for reclamation is continuously fed into the bed from beneath.
- the material Before processing in the fluidised bed, the material is subjected to mechanical attrition to break it down into grain-sized particles. This process does however create a great deal of dust, which tends to contain a high
- FIG. 3 shows a practical version of the apparatus
- Used material from a casting process is fed through a hopper 30 containing a drum magnet for removing pieces of metal. From there, the material passes down a chute 31 and via a valve 32 to a pressure vessel 33.
- a pneumatic conveyor 34 extends from the pressure vessel 33 to a fluidised bed 35, and comorises an inlet pipe 36, a manifold 37 and a pluralitv of
- pneumatic lines 38 extending from the manifold 37.
- Each line 38 is provided with a valve 39 for regulating the flow of material to the bed 35, and terminates at an injector 40 disposed at approximately the level of bubble caps (not shown) in the bed 35.
- an injector 40 disposed at approximately the level of bubble caps (not shown) in the bed 35.
- To one side of the bed 35 there is provided a cooler/classifier 41 to which material flows from the bed 35 over a weir (not shown). If desired, an after-bed (not shown) can be interposed between the bed 35 and the cooler/classifier 41.
- the pressure vessel 33 is provided with a high level probe 42 and a low level probe 43. When the level of material in the vessel reaches the probe 42, the valve 32 is
- the provision of the low level probe 43 prevents the mixture from being completely exhausted from the pneumatic conveyor 34 after each batch feed operation, so that hot sand from the bed 35 is prevented from running through the system and into the vessel 33 under the action of gravity.
- the apparatus can also be provided with a charging or priming system which, as the bed is about to be shut down, allows clean sand to be fed into the vessel 33 and thence into the conveyor 34. In this way, it is ensured that these parts do not contain any bonding agent during shut down, which might otherwise cause rebonding of the sand and consequent clogging of the pneumatic conveyor.
- foundry sand for reclamation is fed in batches to the fluidised bed.
- a substantially continuous feed can be provided by arranging a series of pressure vessels and pneumatic conveyors in parallel.
- one pressure vessel can be charged with material from the chute 31 at the same time as material from the other vessel is conveyed to the bed.
- Reference numeral 44 designates a detector provided in the chute 31 to regulate the flow of the material to the vessel 33.
- material will accumulate in the chute 31 waiting for the valve 32 to be re-opened. So long as the material is fed at a rate less than the maximum capacity of the system, the level of the material in the chute 31 will never rise as far as the detector 44 before the valve 32 re-opens and causes the level to drop once again. However, if the feed rate exceeds the maximum capacity of the system, then the level of the material in the chute will rise as far as the detector 44, and the latter will activate a control to cause feeding of the material to cease.
- a further advantage of the method and apparatus according to the invention is that the hopper from which material to be reclaimed is fed is not necessarily located above the level of the furnace. This enables the apparatus to be installed in a building with a relatively low roof or ceiling.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Processing Of Solid Wastes (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
- Working-Up Tar And Pitch (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9010611 | 1990-05-11 | ||
GB909010611A GB9010611D0 (en) | 1990-05-11 | 1990-05-11 | Thermal reclamation method and apparatus |
PCT/GB1991/000714 WO1991017848A1 (en) | 1990-05-11 | 1991-05-03 | Thermal reclamation method and apparatus |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0482161A1 true EP0482161A1 (en) | 1992-04-29 |
EP0482161B1 EP0482161B1 (en) | 1995-04-19 |
Family
ID=10675837
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91908839A Expired - Lifetime EP0482161B1 (en) | 1990-05-11 | 1991-05-03 | Thermal reclamation method |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0482161B1 (en) |
AT (1) | ATE121326T1 (en) |
DE (1) | DE69109049T2 (en) |
ES (1) | ES2071996T3 (en) |
GB (2) | GB9010611D0 (en) |
WO (1) | WO1991017848A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2680326B1 (en) * | 1991-08-14 | 1995-03-24 | Fm Ind | METHOD, UNIT AND INSTALLATION FOR REGENERATION BY CALCINATION OF FOUNDRY SANDS. |
GB2263535B (en) * | 1992-01-08 | 1995-07-12 | Richards Eng Ltd | Incineration apparatus |
GB2264352A (en) * | 1992-01-31 | 1993-08-25 | Richards Eng Ltd | Incineration apparatus |
FR2696367B1 (en) * | 1992-10-07 | 1994-12-23 | Fm Ind | Method and installation for regenerating heterogeneous foundry sands. |
GB2285119A (en) * | 1993-12-21 | 1995-06-28 | Boc Group Plc | Oxygenated incinerator |
GB9624340D0 (en) * | 1996-11-22 | 1997-01-08 | Foseco Int | Sand reclamation |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB731923A (en) * | 1951-09-21 | 1955-06-15 | Dorr Co | Process for the thermal treatment of finely divided solids |
US3776150A (en) * | 1972-03-06 | 1973-12-04 | Awt Systems Inc | Fluidized bed system for solid wastes |
US4213938A (en) * | 1976-03-29 | 1980-07-22 | Robert Pyzel | Fluid bed reactor |
DE2814239C2 (en) * | 1978-04-03 | 1985-11-14 | Steag Ag, 4300 Essen | Fluidized bed combustion for the combustion of lumpy fuel |
GB2056048B (en) * | 1979-07-19 | 1983-06-08 | Richards Structural Steel Co L | Handling and/or treatment of particulate materials |
US4330502A (en) * | 1980-06-16 | 1982-05-18 | A. Ahlstrom Osakeyhtio | Fluidized bed reactor |
SE437722B (en) * | 1980-10-22 | 1985-03-11 | Stal Laval Turbin Ab | VIRVELBEDDSBRENNKAMMARE |
DE3903604C1 (en) * | 1989-02-08 | 1990-03-29 | Siempelkamp Giesserei Gmbh & Co, 4150 Krefeld, De | Process for regenerating moulding sand |
-
1990
- 1990-05-11 GB GB909010611A patent/GB9010611D0/en active Pending
-
1991
- 1991-05-03 ES ES91908839T patent/ES2071996T3/en not_active Expired - Lifetime
- 1991-05-03 DE DE69109049T patent/DE69109049T2/en not_active Expired - Fee Related
- 1991-05-03 AT AT91908839T patent/ATE121326T1/en not_active IP Right Cessation
- 1991-05-03 WO PCT/GB1991/000714 patent/WO1991017848A1/en active IP Right Grant
- 1991-05-03 GB GB9109673A patent/GB2244939B/en not_active Expired - Fee Related
- 1991-05-03 EP EP91908839A patent/EP0482161B1/en not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
---|
See references of WO9117848A1 * |
Also Published As
Publication number | Publication date |
---|---|
GB9109673D0 (en) | 1991-06-26 |
DE69109049D1 (en) | 1995-05-24 |
EP0482161B1 (en) | 1995-04-19 |
ES2071996T3 (en) | 1995-07-01 |
GB2244939B (en) | 1993-12-08 |
WO1991017848A1 (en) | 1991-11-28 |
GB2244939A (en) | 1991-12-18 |
DE69109049T2 (en) | 1995-08-31 |
GB9010611D0 (en) | 1990-07-04 |
ATE121326T1 (en) | 1995-05-15 |
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