GB2138316A - Fluidised-bed with protective layer - Google Patents
Fluidised-bed with protective layer Download PDFInfo
- Publication number
- GB2138316A GB2138316A GB08407330A GB8407330A GB2138316A GB 2138316 A GB2138316 A GB 2138316A GB 08407330 A GB08407330 A GB 08407330A GB 8407330 A GB8407330 A GB 8407330A GB 2138316 A GB2138316 A GB 2138316A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bed
- fluidised
- fluidised bed
- protective layer
- workpiece
- 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.)
- Withdrawn
Links
- 239000011241 protective layer Substances 0.000 title claims abstract description 15
- 239000002245 particle Substances 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims description 13
- 239000000126 substance Substances 0.000 claims description 7
- 230000005484 gravity Effects 0.000 claims description 6
- 239000011236 particulate material Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 10
- 239000007789 gas Substances 0.000 description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 7
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 229910002092 carbon dioxide Inorganic materials 0.000 description 5
- 239000001569 carbon dioxide Substances 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 229940105305 carbon monoxide Drugs 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 150000002431 hydrogen Chemical class 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000007792 gaseous phase Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000005555 metalworking Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/53—Heating in fluidised beds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
- B01J8/32—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with introduction into the fluidised bed of more than one kind of moving particles
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Thermal Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Combustion & Propulsion (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Crucibles And Fluidized-Bed Furnaces (AREA)
- Heat Treatments In General, Especially Conveying And Cooling (AREA)
Abstract
To a fluidised bed are added components with a mean size at least 20 times larger than that of the particles of the fluidised bed and with a density lower than that of the fluidised bed, any loss of the three-dimensional components being made up by adding them in an amount ensuring that the required thickness of the protective layer formed by these components over the entire surface of the fluidised bed is maintained. Workpieces are introduced into the fluidised bed preferably through the protective layer. Only one such component, covering substantially the whole of the bed, may be added if desired. <IMAGE>
Description
SPECIFICATION
Fluidised-bed heat and/or chemical treatment method and apparatus
This invention relates to a method of fluidised-bed heat and/or chemical treatment, and to a fluidised bed for the heat and/or chemical treatment. The invention is particularly but not essentially applicable to treatment of metal tools. Fluidised beds known for the heat and/or chemical treatment of metal workpieces contain particles of one size fraction, or of several more fractions which somewhat differ in their sizes and specific gravity. Such fluidised beds of open fluidised-bed furnaces contact air over the vast surface of the particles aerated over the bed and, consequently, considerable amounts of air are absorbed by the bed.Some of the components of the absorbed air, mainly oxygen, water vapour and carbon dioxide, can react with the gaseous or solid phase of the fluidised bed and alter the properties of these phases and their chemical action on the workpieces treated in the fluidised bed.
These alterations are disadvantageous in many cases. Particularly disadvantageous is the penetration of air into a bed consisting of a chemically inactive granular material, such as alundum, fluidised by a gas containing hydrogen and carbon monoxide for the purpose of protecting the treated workpieces from being oxidised and decarburised.
Due to air penetrating into such a bed, the contents of water vapour and carbon dioxide in the fluidising gas increase, which impairs the ability of the bed to protect workpieces from being oxidised and decarburised.
The fluidised beds of heat treatment furnaces are prevented from absorbing air by means of covers and flame curtains. The disadvantages of using a cover are more difficult loading and unloding of the workpieces and also contact between the fluidised bed and air during these two operations. The disadvantages of flame curtains are fuel consumption and increased furnace heat radiation.According to one aspect of the present invention there is provided a method of fluidised-bed heat- and/or chemical treatment of a workpiece comprising establishing a fluidised bed of a particlate material, adding to the fluidised bed at least one threedimensional component having a mean size at least 20 times larger than that of the particles of the fluidised bed and a specific weight lower than that of the fluidised bed to form a protective layer on the bed, making up any loss of the protective layer by adding said three-dimensional components to ensure a required thickness of the protective layer over the entire surface of the fluidised bed, and introducing the workpieces into the fluidised bed for treated ment. Preferably the workpieces are fed into the fluidised bed through that protective layer.
It is advantageous for the three-dimensional components to be added to the fluidised bed in the amount of from 1 to 30 per cent by volume of the immovable fluidised bed and prior to starting the treatment process. Three-dimensional components with hollow, preferably closed, internal voids can be added to the fluidised bed. It is also possible to add to the fluidised bed only one such three-dimensional component with closed internal voids and with openings running throughout that component, and through these openings workpieces are introduced into the inside of the fluidised bed. The threedimensional components introduced in the fluidised bed, being located above the particles oftheflui- dised bed, float on its surface.
The specific gravity of the particles of the fluidised bed and that of the three-dimensional components is understood to be the apparent bulk density, i.e.
based on a volume which also includes the empty internal voids of the three-dimensional components.
That the dimensions of the three-dimensional components are larger than those of the particles of the fluidised bed favours the attenuation of the surface ofthefluidised bed. The protective layer formed on the surface of the fluidised bed is sufficient to make contact between the bed and air difficult, particularly when it covers the entire surface of the bed and is of sufficient thickness. The three-dimensional components can be added to the fluidised bed prior to introducing it into the furnace, or directly into the furnace already filled with a stationary or fluidised bed.
The loss of the three-dimensional components occurring due to the friction caused by the operation of the fluidised bed can be compensated for in any way. If there is only one such three-dimensional component it should favourably cover the entire surface of the bed. Irrespective of the number of the three-dimensional components used, the present invention enables workpieces to be introduced into the inside of the fluidised bed through the protective layer. The advantageous effect of this, when treating only a part of the surface of the workpieces, is that a markedly more distinct boundary is obtained between the areas of the respective workpiece which are treated and untreated thermally and/or chemically. Besides, the application of the protective layer enables both the furnace cover and the flame curtain to be eliminated.
A second aspect of the present invention provides a fluidised bed for the heat-and/or chemicaltreatment of a workpiece, said bed comprising a particulate material and at least one additional three-dimensional component with a size at least 20 timeslargerthanthatofthe particles of said particulate material of the bed and with a specific gravity lower than that of the fluidised bed. Preferably the fluidised bed contains such threedimensional components having a total volume ranging from 1% to 30% of the volume of the basic stationary particulate material of the bed, these volumes including also the internal void volumes where the three-dimensional components have hollow, preferably closed, internal voids.The fluidised bed can also comprise only one such threedimensional component with one or more hollow, closed internal voids and with openings running through the component, these openings being adapted to the transverse dimensions of the workpieces.
In order that the present invention may more readily be understood reference will now be made, merely by way of example, to several preferred embodiments, described with the aid of the accompanying drawings, in which:
Figure 1 is a plan view of a three-dimensional component used in Example 2 below; and
Figure 2 is a section taken on the line ABCDEF of
Figure 1.
For comparison of the results obtained with the invention and with the prior art, respectively, an example by the known method has been provided.
Prior art
66.5 kg of the known fluidised alundum bed, with a particle size of 0.1 mm, are disposed in an open fluidised-bed furnace with a fluidiser diameter of 300 mm and depth of 550 mm atatemperatureof790'C.
The particles are fluidised with a gas supplied to the bed at a rate of 2.5 m3/h and consisting of 39.0% of hydrogen, 19.4% of carbon monoxide, 1.0% water vapour, 0.6% of carbon dioxide, and 40.0% of nitrogen. The composition of the gas changed in the bed to 38.8% of hydrogen, 18.9% of carbon monox ide, 2.0% of water vapour, 1.2% of carbon dioxide, and 39.1% of nitrogen. Ammonia was then added to the bed at a rate of 0.3 m3/h.
Metalworking files, 150 mm long, 15 mm wide and 8 mm thick, and made of grade N12E steel containing about 1.2% of carbon, were heated in the bed to their hardening temperature. For that purpose nine files, each clamped in tongs, were dipped with their working parts into the bed for a time of 3.5 minutes and, next, removed from the bed and quenched in water. After such a treatment, the files did not meet the requirement of the working qaulity test involving filing 58HRC hard steel. The reason for the failure of the treatment was the decarburisation of the edges of the files when being heated in the fluidised bed, as confirmed by the foil test for measuring the carbon potential of the bed, which showed a carbon potential of 0.38%.
Example 1
Next use was made of a bed having alundum, with a particle size of 0.1 mm and a weight of 57.1 kg, to which has been added outside the furnace 2.2 kg of three-dimensional components made of porous chamotte in the form of cubes with a side of 10 mm. The alundum bed, together with the chamotte components, were poured into the furnace. The bed was fluidised with a gas as explained previously, the previous bed temperature being also maintained.
The fluidised bed of alundum particles sized 0.1 mm had a specific gravity of 1.73 kg/dm3. The porous chamotte components shaped as cubes with a side of 10 mm had a specific bulk density of 0.45 kg/dm3. These components formed a 70 mm thick layer on the surface of the bed. The composition of the gas supplied changed in the bed to 39.0% of hydrogen, 19.4% of carbon monoxide, 1.1% of water vapour, 0.7% carbon dioxide, and 39.8% of nitrogen.
As in the prior art example, ammonia was added to the bed at a rate of 0.3 m3/h, and files of the same type were heated and hardened in the same way.
It was noted that the bed surface was less turbulent than before, the flame above the bed was lower, the thermal radiation of the bed was weaker, and the file clamping tongs warmed up less. After the treatment, the files satisfied the requirement of the quality test involving filing 58 HRC hard steel.
The foil test showed a carbon potential of 0.83% in the bed.
Example 2
For hardening the files, just as in Example 1, use was made of an alundum bed having a particle size of 0.1 mm and placed in the furnace in the amount of about 60 kg, and a single three-dimensional component, shaped as a sheet metal can, with closed hollow internal voids and through holes was put onto the bed. The can-shaped component was made from 1 mm thick sheet metal. The can diameter was 580 mm and its thickness 30 mm. Through holes in the shape of rectangles with sides of 10 and 30 mm were made in the can.
The bed was fluidised with a gas as in Example 1, the bed temperature being also maintained at the same value as in Example 1. The fluidised bed of alundum particles sized 0.1 mm had a specific gravity of 1.73 kg/dm3. The can-shaped component had a total weight of 2.0 kg, a volume of 1.66 dm3, and an apparent specific weight of 1.22 kg/dm3. The component floated on the bed surface. The composition of the gas changed in the bed in the same way as in the bed of Example 1. Just as in that example, ammonia was added to the bed at a rate of 0.3 m3/h, and files of the same type were heated and hardened in a similar way. For the purpose of being heated, the files were dipped in the bed through the through holes of the can-shaped component.
The movements of the can-shaped component on the bed surface were slight. The flame passing through the gap between the periphery of the component and the fluidiser bed, and through the through holes of the component, was not high. The heat radiation of the bed was weaker than that of the bed without the can-shaped component. The file clamping tongs were not warmed up to any great extent.
After having been heated, the files satisfied the requirement of the quality test for filing 58 HRC hard steel. The foil test for measuring the coal potential of the bed showed a carbon otential of 0.79%.
Claims (14)
1. A method of fluidised-bed heat-and/or chemical-treatment of a workpiece comprising establishing a fluidised bed of a particular material, adding to the fluidised bed at least one three-dimensional component having a means size at least 20 times larger than that of the particles of the fluidised bed and a specific weight lower than that of the fluidised bed to form a protective layer on the bed, making up any loss of the protective layer by adding said threedimensional components to ensure a required thickness of the protective layer over the entire surface of the fluidised bed, and introducing the workpiece into the fluidised bed for treatment.
2. A method according to claim 1, wherein the workpiece is introduced into the bed through the protective layer.
3. A method according to claim 1 or 2, wherein said protective layer is formed by a plurality of the three-dimensional component added to the fluidised bed and has a volume of from 1 to 30% of the volume of the stationary fluidised bed.
4. A method according to claim 3, wherein the volumes are those applicable before starting the treatment.
5. A method according to any one of claims 1 to 4, wherein said three-dimensional components added to the fluidised bed have internal voids.
6. A method according to claim 5, wherein said internal voids are closed.
7. A method according to claim 1 or 2, wherein there is only one three-dimensional component added to the bed, such component having closed internal voids and through holes for introduction of said workpiece therethrough into the inside of the fluidised bed.
8. Afluidised bed forth heat-and/or chemicaltreatment of a workpiece, said bed comprising a particulate material and at least one additional three-dimensional component with a size at least 20 times larger than that of the particles of said particulate material of the bed and with a specific gravity lower than that of the fluidised bed.
9. A bed according to claim 8, wherein said at least one three-dimensional component has internal voids.
10. A bed according to claim 9, wherein said internal voids are closed.
11. Afluidised bed according to claim 8,9 or 10, wherein there is a plurality of said three-dimensional components with a total volume of from 1 to 30% of that of the basic particulate material of the bed when stationary.
12. A bed according to claim 8, wherein there is only one said three-dimensional component having closed internal voids and holes through that component, the transverse dimensions of said holes being at least as large as the transverse dimensions of the workpiece to be treated.
13. A method of treating a workiece, substantially as hereinbefore described with reference to
Example 1 or Example 2.
14. Afluidised bed for heat-and/or chemical- treatment of a workpiece, substantially as hereinbefore described with reference to the Examples 1 and 2 or as illustrated in Figures 1 and 2.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PL24112583A PL140261B1 (en) | 1983-03-21 | 1983-03-21 | Fluidized bed for heat and or thermochemical treatment of metal articles,in particular tools,preferably hardenable ones |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8407330D0 GB8407330D0 (en) | 1984-04-26 |
| GB2138316A true GB2138316A (en) | 1984-10-24 |
Family
ID=20016336
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08407330A Withdrawn GB2138316A (en) | 1983-03-21 | 1984-03-21 | Fluidised-bed with protective layer |
Country Status (3)
| Country | Link |
|---|---|
| GB (1) | GB2138316A (en) |
| HU (1) | HUT39210A (en) |
| PL (1) | PL140261B1 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1087355A (en) * | 1963-12-16 | 1967-10-18 | Exxon Research Engineering Co | Fluidised bed operation |
| GB1489421A (en) * | 1975-03-20 | 1977-10-19 | Coal Ind | Combustion or gasification of combustible solids |
| GB2117660A (en) * | 1982-02-22 | 1983-10-19 | David John Ayres | Fluidisation apparatus |
-
1983
- 1983-03-21 PL PL24112583A patent/PL140261B1/en unknown
-
1984
- 1984-03-21 HU HU112584A patent/HUT39210A/en unknown
- 1984-03-21 GB GB08407330A patent/GB2138316A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1087355A (en) * | 1963-12-16 | 1967-10-18 | Exxon Research Engineering Co | Fluidised bed operation |
| GB1489421A (en) * | 1975-03-20 | 1977-10-19 | Coal Ind | Combustion or gasification of combustible solids |
| GB2117660A (en) * | 1982-02-22 | 1983-10-19 | David John Ayres | Fluidisation apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8407330D0 (en) | 1984-04-26 |
| HUT39210A (en) | 1986-08-28 |
| PL241125A1 (en) | 1985-08-13 |
| PL140261B1 (en) | 1987-04-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |