CA1236291A - Fluidized bed furnace heated by infrared radiation - Google Patents
Fluidized bed furnace heated by infrared radiationInfo
- Publication number
- CA1236291A CA1236291A CA000488245A CA488245A CA1236291A CA 1236291 A CA1236291 A CA 1236291A CA 000488245 A CA000488245 A CA 000488245A CA 488245 A CA488245 A CA 488245A CA 1236291 A CA1236291 A CA 1236291A
- Authority
- CA
- Canada
- Prior art keywords
- bed
- lamps
- infrared radiation
- product
- temperature
- 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.)
- Expired
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- Furnace Details (AREA)
- Crucibles And Fluidized-Bed Furnaces (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Heat treating of product such as strip like material is accomplished by use of a fluidized bed heated by infrared radiation energy emitted immediately above the bed. The energy is produced by electrically powered infared radiation lamps, the output of which are controlled in accordance with the heat requirements of the bed. Product is introduced to the bed and heated to the desired temperature upon exiting the bed. Energy distribution throughout the bed occurs rapidly due to the known heat transfer characteristics thereof. Such a system can heat product to a temperature of up to about 1200°C and also allows fast start up of the bed from ambient to the operating temperature.
Heat treating of product such as strip like material is accomplished by use of a fluidized bed heated by infrared radiation energy emitted immediately above the bed. The energy is produced by electrically powered infared radiation lamps, the output of which are controlled in accordance with the heat requirements of the bed. Product is introduced to the bed and heated to the desired temperature upon exiting the bed. Energy distribution throughout the bed occurs rapidly due to the known heat transfer characteristics thereof. Such a system can heat product to a temperature of up to about 1200°C and also allows fast start up of the bed from ambient to the operating temperature.
Description
` I
-I TITLE: IMPROVED FLUIDIZED BED FURNACE HEATED BY Infrared RADIATION
l BACKGROUND OF THE INVENTION
Heat treatment of metals in -Fluids boas with or without a controlled atmosphere have been proposed for many applications and the his-tory of fluidized beds and the various techniques are well described in an article by ROW. Reynolds on, published in the publication Heat Treatment of Metals, 1977.1, entitled Control Atmosphere Fluidizied Bed -For Heat Treatment of Metals. In this article, a fluidized bed furnace is shown where internal resistance heating elements are place within a fluidized bed for the batch treating of a product. The article also refers to various types of combustion processes winch may be carried out within and/or above a fluidized bed. Generally, fluidized beds heated by combustion have an operating temperature somewhere between 600 and 800C and are not suitable for high temperature application.
In fluidized beds and in -the heat treating of any product, it is important to provide uniform heating and it is also important to provide a system which is capable of fast start up.
A substantial amount of research has been undertaken with respect to introducing of a combustible gas Jo a flossed bed in a manner where the gas assists in the Fluidization of 6693/85 - 2 - lS~Sli 1 the bed while also providing the proper gas mixture to support corrbustion within the bed. In cases where a controlled atmosphere is required, the combustion process is still carries out within a portion of -the bed which results in the heating of particles which are stripped from the combustion gases anywhere returned to the fluid be for heating of the remaining particles of the bed and heating of the product being treated.
In this way, the product briny treated is isolator from tune atmosphere required to support combustion. The portion of the bed which does not have the combustible chases is fluidized by an inert gas.
The demands placed on the heating source of -the fluidized bed should be capable of rapidly raising the temperature of the fluid bed from ambient to the heat treat temperature, preferably up to about 1200C. In addition, the heating source should be capable of providing uniform heating of the bed once the bed has arrived at its operating temperature. To date, the ability to rapidly raise the temperature of the fluid bed to operating levels and -thereafter 2û maintain it in a manner such that the uniform heating of products is accomplished, has been achieved with -fluids beds, but problems occur with gas fired at tune upper temperatures.
~3~2~
6693/85 - 3 - 1~5~G
We have found that it is possible -to provide uniform and rapid heating of a bed of fluidized refractory particles in a channel type furnace used for the heat treating of product on a continuous basis by using high intensity infrared radiation lamps exposed to the surface of the fluidized bed.
This system allows the fluidized gas to be separated from the initial heating step as the energy is transmitted -to the particles of the bed by radiation, resulting in efficient an rapid heat transfer. The high intensity infrared radiation lamps are capable of operating at maximum power to rapidly raise the temperature of a fluidized bed and are capable of operating at a reduced power setting to provide uniform heating of the bed. The heating of the surface of the bed by infrared radiation and the thermal transfer characteristics of the bed cooperate to effect rapid and uniform heat transfer throughout the length, width and depth of the bed. The radiation emitted by the lamps can be controlled by adjusting the power input to the lamps and preferably the lamps are disposed along the length of the bed to initially expose the surface of the bed to generally uniform radiation levels.
SUMMARY OF THE INVENTION
Apparatus according -to the invention is used for heat treating of metal products such as wire, s-trip and special section materials and the like on a continuous basis as the product is passed through a fluids bed.
66~3/85 - 4 - lS5~G
1 The apparatus comprises a normal fluidized owed of refractory particles suitably fluidized by a gas with a surface of the bed being exposed -to high intensity infrared radiation for heating thereof. Infrared radiation sources are positioned above the bed and emit the radiation which is absorbed by tune particles. The absorbed energy is quickly dissipate throughout the bed due to the thermal -transfer characteristics of fluid beds. This combination provides a heated fluid bed which is highly temperature responsive to increasing levels of radiation varied by controlling the input energy to the radiation source. The product being treated is passed through -the bed preferably out of direct contact with the emitted radiation.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings wherein;
Figure 1 is a sectional view through fluidized bed furnace; and Figure 2 is a sectional view taken along line AA of Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The channel-type fluidized bed furnace generally indicated as 2 has a fluidized bed generally indicated as 4, including refractory particles or the like fluidized by tune yes I
6693/85 - 5 - 1~53 1 flow generally indicated as 6. The fluidized gas will be selected in accordance with the post processing surface conditions sought to be obtained. This gas is introduce in any of a number of known manners adjacent the base of the refractory insulation material 10. Exterior to the insulation material, is an exterior steel shell and section case which includes suitable means for supporting the furnace. In this case, a fluidizing gas inlet 12 is provided a-t the upper surface of -the base of the refractory insulation material 10.
Heating of the fluidized bed is accomplished by an infrared radiation source generally indicated as 14. This radiation source includes high intensity infrared radiation lamps 16 positioned generally immediately above the surface of the fluid bed 4. The lamp end tips 18 have been located within cooling conduits 22 for cooling of the lamp ens. A cooling gas is circulated through the conduits 22 to maintain the lamp end tips at a lower temperature to increase the life of the lamps. Above the lamps 16 and intermediate the cooling conduits 22 is a top panel 24 which has a lower surface exposed on to the infrared radiation lamps and is preferably of a material and shape to redirect radiation emitted by the lamps which strikes the panel, downwardly to the surface of the fluid bed 4.
The channel-type fluid bed furnace 2 has an entrance generally indicated as 30 and a exit generally indicated as for introducing and withdrawing a product from the fluid bed.
I
669~/85 - 6 - 1~5 l In some cases, submerged rollers or other devices may be required to maintain the introduced product submerged and out of direct contact with emitted radiation as it is passed throughout the length of the furnace 2.
The product which is passed through the fluid bed furnace may be wire, strip and the like and can be pushed or pulled through the furnace depending upon the actual product.
The product is heated as it is moved from the entrance MU to the exit 32 to leave -the fluid bed furnace at an approximate lo given temperature. The fluidized be of particles serves -tug isolate the product being treated from the emit-ted radiation of the infrared radiation source 14. It can be appreciate treating of` other products are possible and -the application is not limited to strip and wire.
The fluid bed particles are preferably aluminum or zirconium oxide particles, although other refractory particles may be suitable. The fluid bed particles in addition to the normal characteristics required in any fluidized bed application should tend to absorb infrared radiation impinged thereon and should not be highly reflective to this radiation.
The spacing of the high intensity infrared radiation lamps 16 along the length of the fluid bed furnace can vary depending upon the maximum temperature capability of the furnace, however, it has been found that if lamps extend across US the bed and are spaced from one another approximately one to four inches along -the length of the bed, rapid heating of the fluid bed from ambient to operating -temperatures is possible.
~23~æ~
6693/85 - 7 - 1~5~G
l With the system described above, the infrared radiation lamps directly heat the surface of the fluid bed and the absorbed infrared radiation is quickly transmitted throughout the fluid bed due to the thermal transfer characteristics of the bed. It has been found that tune infrared radiation lamps and particularly high intensity electrically powered shortwave infrared radiation lamps are capable of rapidly raising the temperature of the bed to an operating temperature in the range of a maximum of about lo 1200C and thereafter the power supplied to the lamps can be reduced to a level of radiation sufficient -to maintain the bed at the desired temperature. The response characteristics of the infrared radiation lamps in accordance with the electrical power supply to the lamps is thus used to result in a fluidized bed furnace which can be quickly raised to the aerating temperature and thereafter maintained to provide even uniform heat distribution throughout the fluid bed. Ail the lamps may be controlled in unison or in groups by varying the electrical input in accordance with a sensed be temperature. Such a system has improved operating characteristics and reduced operating costs.
In Figure l, the infrared radiation source is movable to a service position exposing the upper surface of the fluid bed and exposing the infrared radiation lamps for inspection and service as shown in broken line. Preferably, one of the I
6~93/85 - 8 - 1353~
1 cooling conduits 22 is hingidly attached to -the exterior steel shell and section case 8 to allow convent positioning of the infrared radiation 14 for service. A quartz limiting member 20 is shown in Figure 1, and serves to isolate the lamps 16 from the hot gas flow 6 and fluid bed particles at the surface of the bed. This limiting member may not be required in all cases, however, in high temperature applications the life of the lamps can be increased.
The apparatus and method have been described with respect to a continuous process, however, the heat treating of products on a batch basis is also possible.
Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.
-I TITLE: IMPROVED FLUIDIZED BED FURNACE HEATED BY Infrared RADIATION
l BACKGROUND OF THE INVENTION
Heat treatment of metals in -Fluids boas with or without a controlled atmosphere have been proposed for many applications and the his-tory of fluidized beds and the various techniques are well described in an article by ROW. Reynolds on, published in the publication Heat Treatment of Metals, 1977.1, entitled Control Atmosphere Fluidizied Bed -For Heat Treatment of Metals. In this article, a fluidized bed furnace is shown where internal resistance heating elements are place within a fluidized bed for the batch treating of a product. The article also refers to various types of combustion processes winch may be carried out within and/or above a fluidized bed. Generally, fluidized beds heated by combustion have an operating temperature somewhere between 600 and 800C and are not suitable for high temperature application.
In fluidized beds and in -the heat treating of any product, it is important to provide uniform heating and it is also important to provide a system which is capable of fast start up.
A substantial amount of research has been undertaken with respect to introducing of a combustible gas Jo a flossed bed in a manner where the gas assists in the Fluidization of 6693/85 - 2 - lS~Sli 1 the bed while also providing the proper gas mixture to support corrbustion within the bed. In cases where a controlled atmosphere is required, the combustion process is still carries out within a portion of -the bed which results in the heating of particles which are stripped from the combustion gases anywhere returned to the fluid be for heating of the remaining particles of the bed and heating of the product being treated.
In this way, the product briny treated is isolator from tune atmosphere required to support combustion. The portion of the bed which does not have the combustible chases is fluidized by an inert gas.
The demands placed on the heating source of -the fluidized bed should be capable of rapidly raising the temperature of the fluid bed from ambient to the heat treat temperature, preferably up to about 1200C. In addition, the heating source should be capable of providing uniform heating of the bed once the bed has arrived at its operating temperature. To date, the ability to rapidly raise the temperature of the fluid bed to operating levels and -thereafter 2û maintain it in a manner such that the uniform heating of products is accomplished, has been achieved with -fluids beds, but problems occur with gas fired at tune upper temperatures.
~3~2~
6693/85 - 3 - 1~5~G
We have found that it is possible -to provide uniform and rapid heating of a bed of fluidized refractory particles in a channel type furnace used for the heat treating of product on a continuous basis by using high intensity infrared radiation lamps exposed to the surface of the fluidized bed.
This system allows the fluidized gas to be separated from the initial heating step as the energy is transmitted -to the particles of the bed by radiation, resulting in efficient an rapid heat transfer. The high intensity infrared radiation lamps are capable of operating at maximum power to rapidly raise the temperature of a fluidized bed and are capable of operating at a reduced power setting to provide uniform heating of the bed. The heating of the surface of the bed by infrared radiation and the thermal transfer characteristics of the bed cooperate to effect rapid and uniform heat transfer throughout the length, width and depth of the bed. The radiation emitted by the lamps can be controlled by adjusting the power input to the lamps and preferably the lamps are disposed along the length of the bed to initially expose the surface of the bed to generally uniform radiation levels.
SUMMARY OF THE INVENTION
Apparatus according -to the invention is used for heat treating of metal products such as wire, s-trip and special section materials and the like on a continuous basis as the product is passed through a fluids bed.
66~3/85 - 4 - lS5~G
1 The apparatus comprises a normal fluidized owed of refractory particles suitably fluidized by a gas with a surface of the bed being exposed -to high intensity infrared radiation for heating thereof. Infrared radiation sources are positioned above the bed and emit the radiation which is absorbed by tune particles. The absorbed energy is quickly dissipate throughout the bed due to the thermal -transfer characteristics of fluid beds. This combination provides a heated fluid bed which is highly temperature responsive to increasing levels of radiation varied by controlling the input energy to the radiation source. The product being treated is passed through -the bed preferably out of direct contact with the emitted radiation.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings wherein;
Figure 1 is a sectional view through fluidized bed furnace; and Figure 2 is a sectional view taken along line AA of Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The channel-type fluidized bed furnace generally indicated as 2 has a fluidized bed generally indicated as 4, including refractory particles or the like fluidized by tune yes I
6693/85 - 5 - 1~53 1 flow generally indicated as 6. The fluidized gas will be selected in accordance with the post processing surface conditions sought to be obtained. This gas is introduce in any of a number of known manners adjacent the base of the refractory insulation material 10. Exterior to the insulation material, is an exterior steel shell and section case which includes suitable means for supporting the furnace. In this case, a fluidizing gas inlet 12 is provided a-t the upper surface of -the base of the refractory insulation material 10.
Heating of the fluidized bed is accomplished by an infrared radiation source generally indicated as 14. This radiation source includes high intensity infrared radiation lamps 16 positioned generally immediately above the surface of the fluid bed 4. The lamp end tips 18 have been located within cooling conduits 22 for cooling of the lamp ens. A cooling gas is circulated through the conduits 22 to maintain the lamp end tips at a lower temperature to increase the life of the lamps. Above the lamps 16 and intermediate the cooling conduits 22 is a top panel 24 which has a lower surface exposed on to the infrared radiation lamps and is preferably of a material and shape to redirect radiation emitted by the lamps which strikes the panel, downwardly to the surface of the fluid bed 4.
The channel-type fluid bed furnace 2 has an entrance generally indicated as 30 and a exit generally indicated as for introducing and withdrawing a product from the fluid bed.
I
669~/85 - 6 - 1~5 l In some cases, submerged rollers or other devices may be required to maintain the introduced product submerged and out of direct contact with emitted radiation as it is passed throughout the length of the furnace 2.
The product which is passed through the fluid bed furnace may be wire, strip and the like and can be pushed or pulled through the furnace depending upon the actual product.
The product is heated as it is moved from the entrance MU to the exit 32 to leave -the fluid bed furnace at an approximate lo given temperature. The fluidized be of particles serves -tug isolate the product being treated from the emit-ted radiation of the infrared radiation source 14. It can be appreciate treating of` other products are possible and -the application is not limited to strip and wire.
The fluid bed particles are preferably aluminum or zirconium oxide particles, although other refractory particles may be suitable. The fluid bed particles in addition to the normal characteristics required in any fluidized bed application should tend to absorb infrared radiation impinged thereon and should not be highly reflective to this radiation.
The spacing of the high intensity infrared radiation lamps 16 along the length of the fluid bed furnace can vary depending upon the maximum temperature capability of the furnace, however, it has been found that if lamps extend across US the bed and are spaced from one another approximately one to four inches along -the length of the bed, rapid heating of the fluid bed from ambient to operating -temperatures is possible.
~23~æ~
6693/85 - 7 - 1~5~G
l With the system described above, the infrared radiation lamps directly heat the surface of the fluid bed and the absorbed infrared radiation is quickly transmitted throughout the fluid bed due to the thermal transfer characteristics of the bed. It has been found that tune infrared radiation lamps and particularly high intensity electrically powered shortwave infrared radiation lamps are capable of rapidly raising the temperature of the bed to an operating temperature in the range of a maximum of about lo 1200C and thereafter the power supplied to the lamps can be reduced to a level of radiation sufficient -to maintain the bed at the desired temperature. The response characteristics of the infrared radiation lamps in accordance with the electrical power supply to the lamps is thus used to result in a fluidized bed furnace which can be quickly raised to the aerating temperature and thereafter maintained to provide even uniform heat distribution throughout the fluid bed. Ail the lamps may be controlled in unison or in groups by varying the electrical input in accordance with a sensed be temperature. Such a system has improved operating characteristics and reduced operating costs.
In Figure l, the infrared radiation source is movable to a service position exposing the upper surface of the fluid bed and exposing the infrared radiation lamps for inspection and service as shown in broken line. Preferably, one of the I
6~93/85 - 8 - 1353~
1 cooling conduits 22 is hingidly attached to -the exterior steel shell and section case 8 to allow convent positioning of the infrared radiation 14 for service. A quartz limiting member 20 is shown in Figure 1, and serves to isolate the lamps 16 from the hot gas flow 6 and fluid bed particles at the surface of the bed. This limiting member may not be required in all cases, however, in high temperature applications the life of the lamps can be increased.
The apparatus and method have been described with respect to a continuous process, however, the heat treating of products on a batch basis is also possible.
Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.
Claims (10)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for the heat treating of metal product such as wire, strip, and other elongate product on a continuous basis as the product is passed through a heating medium comprising a fluidized bed of refractory particles and including means for continuously passing a gas through the bed to fluidize the particles, an entrance at one end of said bed for introducing such product to said bed and an exit at the opposite end of said bed for removing product therefrom, means for submerging such product within said bed intermediate the entrance and exit, said bed being heated by a high intensity infrared radiation source position immediately above the bed which emits high intensity infrared radiation energy absorbed by the exposed particles of the fluid bed, the absorbed radiation being quickly and evenly distributed throughout the bed due to the thermal transfer characteristics of the fluid bed, said radiation source being controlled to vary the emitted infrared radiation as required to initially raise the bed temperature to operating temperature or to maintain such operating temperature.
2. Apparatus as claimed in claim 1, wherein said source is a plurality of electrically high intensity infrared radiation lamps disposed above said bed and transmitting radiation emitted by said lamps to a surface of said fluidized bed to effect a generally even distribution of radiation energy to such surface of said bed.
3. Apparatus as claimed in claim 2, wherein said lamps are disposed across said bed and are generally equally spaced one from the other.
4. Apparatus as claimed in claim 1, wherein said lamps are spaced apart in the range of 1 to 4 inches along essentially the length of said bed and wherein said apparatus may be raised from ambient to the operating temperature within at least about half the time required to heat the bed if a combustion process was used to heat the bed.
5. Apparatus as claimed in claim 1, including means for sensing the temperature of the bed and control means which adjusts the electrical power of said lamps in accordance with the sensed temperature.
6. Apparatus as claimed in claim 2, wherein said gas is recycled at the surface of the bed and maintained out of contact with said lamps.
7. Apparatus as claimed in claim 6, wherein said gas is air.
8. Apparatus as claimed in claim 5, wherein said control means separately controls some of said lamps to effect different rates of energy input to said bed along the length thereof.
9. In a fluidized bed having an open top and capable of the continuous heat treating of heat treatable product such as metal strip, wire and the like, the improvement comprising heating the particles of the bed by exposing the top surface of the fluid bed to high intensity infrared radiation at a rate sufficient to maintain the fluid bed temperature about a predetermined temperature.
10. In a fluidized bed as claimed in Claim 9, wherein the high intensity infrared radiation is produced by shortwave infrared radiation lamps disposed generally immediately above the fluid bed and in a manner to provide heating of substantially all of the top surface of the bed.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000488245A CA1236291A (en) | 1985-08-07 | 1985-08-07 | Fluidized bed furnace heated by infrared radiation |
| AT86305987T ATE89397T1 (en) | 1985-08-07 | 1986-08-04 | HEATING A FLOW-BED FURNACE. |
| EP86305987A EP0224320B1 (en) | 1985-08-07 | 1986-08-04 | Improved heating of fluidized bed furnace |
| DE8686305987T DE3688422T2 (en) | 1985-08-07 | 1986-08-04 | HEATING A FLUID BED. |
| AU60916/86A AU596368B2 (en) | 1985-08-07 | 1986-08-06 | Improved heating of fluidized bed furnace |
| US06/889,518 US4752061A (en) | 1985-08-07 | 1986-09-08 | Infrared heating of fluidized bed furnace |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000488245A CA1236291A (en) | 1985-08-07 | 1985-08-07 | Fluidized bed furnace heated by infrared radiation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1236291A true CA1236291A (en) | 1988-05-10 |
Family
ID=4131133
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000488245A Expired CA1236291A (en) | 1985-08-07 | 1985-08-07 | Fluidized bed furnace heated by infrared radiation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1236291A (en) |
-
1985
- 1985-08-07 CA CA000488245A patent/CA1236291A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |