CA1276433C - Process of carrying out high-temperature reactions - Google Patents
Process of carrying out high-temperature reactionsInfo
- Publication number
- CA1276433C CA1276433C CA000521624A CA521624A CA1276433C CA 1276433 C CA1276433 C CA 1276433C CA 000521624 A CA000521624 A CA 000521624A CA 521624 A CA521624 A CA 521624A CA 1276433 C CA1276433 C CA 1276433C
- Authority
- CA
- Canada
- Prior art keywords
- solids
- gas
- fluidized bed
- preheated
- supplied
- 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 - Lifetime
Links
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 21
- 239000007787 solid Substances 0.000 claims abstract description 76
- 239000007789 gas Substances 0.000 claims abstract description 56
- 239000000725 suspension Substances 0.000 claims abstract description 29
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000002826 coolant Substances 0.000 claims abstract description 11
- 239000001301 oxygen Substances 0.000 claims abstract description 11
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 11
- 230000009969 flowable effect Effects 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 description 13
- 206010039509 Scab Diseases 0.000 description 4
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 239000011396 hydraulic cement Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 235000014380 magnesium carbonate Nutrition 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B15/00—Fluidised-bed furnaces; Other furnaces using or treating finely-divided materials in dispersion
- F27B15/003—Cyclones or chain of cyclones
Landscapes
- Engineering & Computer Science (AREA)
- Dispersion Chemistry (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Crucibles And Fluidized-Bed Furnaces (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Carbon And Carbon Compounds (AREA)
- Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
- Treating Waste Gases (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
In a process of carrying out high-temperature reactions between a hot gas and preheated solids, which when treated at a high temperature, are no longer free flowable, the preheated solids are supplied from below in the direction of conveyance through a burner flame, which is disposed in the lower portion of a conveyor passage. When the solids have been conveyed throughout the length of a sufficiently long reaction zone and the desired reaction has been completed, the gas-solids suspension still flowing in the same direction is contacted with a separately introduced coolant at a point succeeding the reaction zone and is thus cooled to a temperature at which the solids are free flowable. The solids are preferably preheated in a circulating fluidized bed, which is supplied with an oxygen-containing fluidizing gas and with an oxygen-containing secondary gas and in which the exhaust gases from the conveyor passage are used. When the solids have been separated from the gas, they are cooled in a fluidized bed cooler.
In a process of carrying out high-temperature reactions between a hot gas and preheated solids, which when treated at a high temperature, are no longer free flowable, the preheated solids are supplied from below in the direction of conveyance through a burner flame, which is disposed in the lower portion of a conveyor passage. When the solids have been conveyed throughout the length of a sufficiently long reaction zone and the desired reaction has been completed, the gas-solids suspension still flowing in the same direction is contacted with a separately introduced coolant at a point succeeding the reaction zone and is thus cooled to a temperature at which the solids are free flowable. The solids are preferably preheated in a circulating fluidized bed, which is supplied with an oxygen-containing fluidizing gas and with an oxygen-containing secondary gas and in which the exhaust gases from the conveyor passage are used. When the solids have been separated from the gas, they are cooled in a fluidized bed cooler.
Description
1 ~i7~3~
The present invention relates to a process of carrying out high-temperature reactions between a hot gas and previously heated solids, which when treated at a high temperature, are no longer free flowable, in a substantially vertical conveyor passage, whereafter the gas-solids suspension is cooled and solids are separated from the cooled suspensionO
In high-temperature reactions, solids are heated to a temperature above that at which said solids are no longer free flowable, so that the individual particles tend to stick or adhere to each other and/or form crusts on the inside surface of the reactor or in pipelines. The loss of free flowability may be due to the reaction of the solids with the gas phase or with other components. The problems mentioned above may be encountered in the burning or sintering, e.g., of alumina, lime, dolomite, magnesite or a yround mixture of raw materials for making hydraulic cement.
Numerous processes and apparatus have been provided in an effort to avoid the difficulties which are due to said process technology.
For instance, in the process disclosed in German Patent Publication No. 23 50 768, solids are preheated in a first zone and are subsequently passed into a second zone through a flame by which they are heated to a final temperature. An air stream for surrounding the flame is supplied in the second zone in order to prevent a formation of crusts on the inside surface of the flame-containing space. That measure has the disadvantage that the air stream supplied to the second zone will inevitably be mixed with the gas-solids suspension which has initially been heated to a sufficiently high temperature and which is thus cooled by the air stream before the desired high-temperature reaction has been ~ ~7~4'~3 completed. As a result, it is not ensured that the solids will be maintained at the high temperature for the residence time required to complete the desired reaction.
German Patent Specification No. 28 46 584 discloses a process and apparatus for heat-treating fine-grained solids in a preheating zone, a calcining zone, a sintering zone, which consists of a suspension-reacting zone, and a cooling zone. In that process at least part of the substantially calcined material is supplied to the sintering zone after a separate heat treatment, by which molten components forming constituents are volatilized. It will be understood that said prior art can be used only when the solids can be maintained in a free flowable state by volatilisation of said constituents. In other cases, that technology cannot avoid a formation of crusts during the sintering in the suspension-reacting zone as a result of a change of the direction of flow of the gas-solids suspension. Moreover, an additional reaction zone is undesirable.
It is an object of the invention to provide for high-temperature reactions between a hot gas and preheated solids a process which is free of the known disadvantages, particu-larly those described hereinbefore, and which permits a satisfactory processing, is universally applicable and can be conveniently carried out.
In a process of the kind described first hereinbefore that object is accomplished in accordance with the present invention in that the preheated solids are supplied from below in the direction of conveyance of a conveyor passage, through a burner flame, which is disposed in the lower portion of the conveyor passage, and are subsequently caused to flow throughout the length of a sufficiently long ~Z7~3~
reaction zone; and when the desired reaction has been completed, the gas-solids suspension still flowing in the same direction and are contacted behind the reaction zone with a separately introduced coolant and are thus cooled to a temperature at which the solids are free flowable.
Because the solids are supplied from below and in the direction of conveyance and coolant is contacted with the gas-solids suspension after the reaction has been completed and when the suspension still flows in the same direction, the direction of flow of the gas-solids suspension will not be changed as it passes through the critical reaction zone between the heating of the suspension to a high temperature and the cooling of the suspension to a temperature at which the gas-solids suspension can be handled without difficulty.
Because the direction of flow of the suspension is not changed, no crusts can be formed. By the subsequent contact with a separately introduced coolant, the residence time for which the suspension is to be maintained at the required high temperature in a given case can be adjusted exactly.
The mean gas velocity to be maintained in the coveyor passage should be so selected that the relative velocities between the solids and the wall will be high. The mean gas velocity will usually lie in the range from 2 to 10 m/sec (stated as an empty-pipe velocity).
The preheated solids are preferably contained in a gas-solids suspension as they enter the conveyor passage and said suspension is passed through the center of an annular burner, which is supplied with fuel, e.g., with a fuel gas.
That mode of supplying the solids ensures a virtually instantaneous heating of the solids to the desired temperature, which depending on the feedstock and the ~7~3~3 desired result lies approximately in the range from 1300 to 1700C, preferably between 1400 and 1500 C.
The length of the conveyor passage may be selected depending on the residence time required for the desired reaction. As a few seconds are sufficient, as a rule, the conveyor line will usually have a length not in excess of 20 meters and generally a length between 5 and 15 meters.
The cooling required after the high-temperature reaction can be effected with gaseous, liquid or solid coolants. Said coolants should be supplied in such a manner that the coolant is rapidly dispersed in the gas-solids suspension and a contact of the solids with the boundary wall of the conveyor line will be avoided. It is particularly desirable to supply the coolant at high velocity in a tangential direction, at right angles or at an angle up to 60 opposite to or in the direction of flow.
After the cooling below the critical temperature, the gas and solids are separated in conventional manner, e.g., in a cyclone separator.
The solids to be subjected to the high-temperature reaction may be preheated in any conventional manner and such preheating may generally be combined with a chemical reaction. It will be particularly desirable to preheat the solids in a so-called circulating fluidized bed.
Whereas an "orthodox" fluidized bed constitutes a dense phase, which is separated by a distinct density step from an overlying gas space, a circulating fluidized bed has states of distribution without a defined interface and involves no density step between a dense phase and an overlying gas ~'~76~3~3 space but the solids concentration in the reactor gradually decreases from bottom to top. Details relating to the operation of circulating fluidized beds have been described by L. Reh at al. in "Wirbelschichtprocesse f~r die Chemie und H~ttenindustrie, die Energieumwandlung und den Umweltschutz", published in Chem. Ing. Techn. 55 (1983), No.
The present invention relates to a process of carrying out high-temperature reactions between a hot gas and previously heated solids, which when treated at a high temperature, are no longer free flowable, in a substantially vertical conveyor passage, whereafter the gas-solids suspension is cooled and solids are separated from the cooled suspensionO
In high-temperature reactions, solids are heated to a temperature above that at which said solids are no longer free flowable, so that the individual particles tend to stick or adhere to each other and/or form crusts on the inside surface of the reactor or in pipelines. The loss of free flowability may be due to the reaction of the solids with the gas phase or with other components. The problems mentioned above may be encountered in the burning or sintering, e.g., of alumina, lime, dolomite, magnesite or a yround mixture of raw materials for making hydraulic cement.
Numerous processes and apparatus have been provided in an effort to avoid the difficulties which are due to said process technology.
For instance, in the process disclosed in German Patent Publication No. 23 50 768, solids are preheated in a first zone and are subsequently passed into a second zone through a flame by which they are heated to a final temperature. An air stream for surrounding the flame is supplied in the second zone in order to prevent a formation of crusts on the inside surface of the flame-containing space. That measure has the disadvantage that the air stream supplied to the second zone will inevitably be mixed with the gas-solids suspension which has initially been heated to a sufficiently high temperature and which is thus cooled by the air stream before the desired high-temperature reaction has been ~ ~7~4'~3 completed. As a result, it is not ensured that the solids will be maintained at the high temperature for the residence time required to complete the desired reaction.
German Patent Specification No. 28 46 584 discloses a process and apparatus for heat-treating fine-grained solids in a preheating zone, a calcining zone, a sintering zone, which consists of a suspension-reacting zone, and a cooling zone. In that process at least part of the substantially calcined material is supplied to the sintering zone after a separate heat treatment, by which molten components forming constituents are volatilized. It will be understood that said prior art can be used only when the solids can be maintained in a free flowable state by volatilisation of said constituents. In other cases, that technology cannot avoid a formation of crusts during the sintering in the suspension-reacting zone as a result of a change of the direction of flow of the gas-solids suspension. Moreover, an additional reaction zone is undesirable.
It is an object of the invention to provide for high-temperature reactions between a hot gas and preheated solids a process which is free of the known disadvantages, particu-larly those described hereinbefore, and which permits a satisfactory processing, is universally applicable and can be conveniently carried out.
In a process of the kind described first hereinbefore that object is accomplished in accordance with the present invention in that the preheated solids are supplied from below in the direction of conveyance of a conveyor passage, through a burner flame, which is disposed in the lower portion of the conveyor passage, and are subsequently caused to flow throughout the length of a sufficiently long ~Z7~3~
reaction zone; and when the desired reaction has been completed, the gas-solids suspension still flowing in the same direction and are contacted behind the reaction zone with a separately introduced coolant and are thus cooled to a temperature at which the solids are free flowable.
Because the solids are supplied from below and in the direction of conveyance and coolant is contacted with the gas-solids suspension after the reaction has been completed and when the suspension still flows in the same direction, the direction of flow of the gas-solids suspension will not be changed as it passes through the critical reaction zone between the heating of the suspension to a high temperature and the cooling of the suspension to a temperature at which the gas-solids suspension can be handled without difficulty.
Because the direction of flow of the suspension is not changed, no crusts can be formed. By the subsequent contact with a separately introduced coolant, the residence time for which the suspension is to be maintained at the required high temperature in a given case can be adjusted exactly.
The mean gas velocity to be maintained in the coveyor passage should be so selected that the relative velocities between the solids and the wall will be high. The mean gas velocity will usually lie in the range from 2 to 10 m/sec (stated as an empty-pipe velocity).
The preheated solids are preferably contained in a gas-solids suspension as they enter the conveyor passage and said suspension is passed through the center of an annular burner, which is supplied with fuel, e.g., with a fuel gas.
That mode of supplying the solids ensures a virtually instantaneous heating of the solids to the desired temperature, which depending on the feedstock and the ~7~3~3 desired result lies approximately in the range from 1300 to 1700C, preferably between 1400 and 1500 C.
The length of the conveyor passage may be selected depending on the residence time required for the desired reaction. As a few seconds are sufficient, as a rule, the conveyor line will usually have a length not in excess of 20 meters and generally a length between 5 and 15 meters.
The cooling required after the high-temperature reaction can be effected with gaseous, liquid or solid coolants. Said coolants should be supplied in such a manner that the coolant is rapidly dispersed in the gas-solids suspension and a contact of the solids with the boundary wall of the conveyor line will be avoided. It is particularly desirable to supply the coolant at high velocity in a tangential direction, at right angles or at an angle up to 60 opposite to or in the direction of flow.
After the cooling below the critical temperature, the gas and solids are separated in conventional manner, e.g., in a cyclone separator.
The solids to be subjected to the high-temperature reaction may be preheated in any conventional manner and such preheating may generally be combined with a chemical reaction. It will be particularly desirable to preheat the solids in a so-called circulating fluidized bed.
Whereas an "orthodox" fluidized bed constitutes a dense phase, which is separated by a distinct density step from an overlying gas space, a circulating fluidized bed has states of distribution without a defined interface and involves no density step between a dense phase and an overlying gas ~'~76~3~3 space but the solids concentration in the reactor gradually decreases from bottom to top. Details relating to the operation of circulating fluidized beds have been described by L. Reh at al. in "Wirbelschichtprocesse f~r die Chemie und H~ttenindustrie, die Energieumwandlung und den Umweltschutz", published in Chem. Ing. Techn. 55 (1983), No.
2, pages 87 to 93, and have also be described in German Patent Specification No. 17 67 628 and U.S. Patent No.
3,579,616.
A circulating fluidized bed has the advantage that it can be operated at a high throughput rate per unit of cross sectional area of the reactor and in that such a long residence time can be selected for the solids to be heated that the chemical reaction combined with the preheating will virtually be completed. In such a case, only the high-temperature reaction proper must be carried out in the process in accordance with the invention so that said process will involve virtually no reactions which can be effected also at lower temperatures.
When the solids leaving the conveyor passage have been separated they are usually cooled further. Said further cooling may be accomplished by conventional coolers, preferably by fluidi~ed bed coolers.
In a preferred embodiment of the invention the high-temperature treatment carried out in accordance with the invention is so integrated in the overall process comprising the preheating and the final cooling of the solids that the several gas streams may be used interchangeably. For instance, oxygen-containing gas may be preheated in the cooler and may then be supplied to the solids-preheating stage and/or the high-temperature reaction stage. The ~'76fl~3~
exhaust gas from the conveyor passage may be supplied to the solids-preheating stage.
In an optimum overall process, the feedstock is preheated in a circulating fluidized bed, which is preceded by preheaters supplied with the exhaust gases, and the final cooling is carried out in a fluidized bed cooler, which comprises a plurality of successive cooling chambers, for through flow.
The solids may be directly and/or indirectly cooled with oxygen-containing gases, which are subsequently supplied as an entraining gas to the conveyor passage and/or as a fluidizing gas to the circulating fluidized bed. The fluidizing gases which have been used in the fluidized bed cooler may finally be used as a coolant in the pneumatic conveyor and the exhaust gases from the pneumatic conveyor may be used as secondary gas in the circulating fluidized bed.
The invention will be explained more in detail and by way of example with reference to the drawing and to the Examples.
The drawing is a flow scheme of a combined system of the kind described hereinbefore.
The solids to be treated are supplied by metering means l to a venturi heat exchanger 2, which is the last of a plurality of such exchangers in the gas flow path. In said last heat exchanger 2 the solids are heated by the available heat of the exhaust gas. The solids are separated from the gas in a cyclone separator 3 and are then supplied through a conveyor 4 to another preheating system, which consists of a venturi heat exchanger 5 and an associated cyclone separator 6 and of a venturi heat exchanger 7 and an associated cyclone separator 8. A by-pass line 9 can be used to supply ~ Z 7 Ei ~3 ,~
conveyed solids directly to the venturi heat exchanger 7 without passing through the preceding preheating stage.
From the cyclone separator 8, the solids are supplied to a circulating system, which consists of a fluidized bed reactor 10, a recycling cyclone 11 and a return line 12.
The fluidized bed reactor 10 is supplied with fuel through line 13, with fluidizing gas through line 14 and with secondary gas through line 15.
After a sufficiently long residence time the preheated suspension is supplied through line 16 to the lower portion of the conveyor passage 17 and is supplied from below into the burner flame, which is produced by means of fuel (line 18) and oxygen-containing gas (line 19). As the gas-solids suspension rises in the lower portion of the conveyor passage 17, the suspension is subjected to the high-temperature reaction and when said reaction has been completed the suspension is cooled by means of gases which are supplied through line 20. When the gas-solids suspension still flowing in the same direction has been sufficiently cooled, the suspension is discharged through line 21 and is separated in the cyclone separator 22 into solids supplied to the fluidized bed cooler 23 and gas supplied through line 15 as secondary gas to the fluidized bed reactor 10.
The fluidized bed cooler 23 is divided into a plurality of cooling chambers, which the solids flow through in succession. The cooler 23 comprises three cooling stages.
In the hottest stage, which is the first in the solids flow path, oxygen-containing gas is heated; that gas is subsequently supplied through line 19 to the conveyor passage 17. The second stage is used to heat the oxygen-~.~7~3~
containing gas which is subsequently supplied through line14 to the fluidized bed reactor lO. The third cooling stage is used for the final cooling of the solids by means of cooling water, which is supplied through a line 24 and discharged through line 25. The cooled product is discharged through a device 26. The fluidizing gas streams which have been used in the fluidized bed cooler 23 are collected and supplied as a coolant through line 20 to the conveyor passage 17.
Example Aluminum hydroxide which is moist after having been filtered is to be converted to highly burnt alumina.
Aluminum hydroxide having a moisture of 12% by weight is supplied at a temperature of 60 C and at a rate of 8690 kg/h through the metering means 1 to the venturi heat exchanger 2 and is subjected in said heat exchanger 2 to a heat exchange with the gases at 390 C which are supplied from the cyclone separator 6. As a result, the aluminum hydroxide is heated to 160 C and the gas is cooled approximately to the same temperature.
By the conve~or 4, the preheated aluminum hydroxide is contacted in the venturi heat exchanger 5 with the exhaust gases at 510C from the cyclone separator 8. This results in a heating of the solids and a cooling of the gas to about 390C. When the gas and solids have been separated in the cyclone separator 6, the solids are supplied to the venturi heat exchanger 7, which is supplied from the circulating fluidized bed with exhaust gases at 1150C. The thorough mixing action results in a gas-solids suspension at a temperature of 510C. After another separation of gas and ~2`76~3~
solids effected in the cyclone separator 8, the solids are supplied to the circulating fluidized bed.
The fluidized bed reactor 10 of the circulating fluidized bed is supplied through line 14 from the second stage of the fluidized bed cooler 23 with fluidizing air at 580C, at a rate of 2000 sm3/h, through line 15 from the cyclone separator 22 with secondary air at 1020 C, at a rate of 4800 sm3/h, and through line 13 with natural gas at a rate of 390 sm3/h. This results in a temperature of 1150 C, which is virtually constant throughout the circulating system consisting of the fluidized bed reactor 10, the recycling cyclone 11 and the return line 12.
lhe aluminum oxide is completely calcined within an average residence time of about 20 minutes. Thereafter, solids corresponding to the feeding rate are supplied through line 16 to the conveyor passage 17 and are heated to 1400C by the burner flame and by the flue gases from the burner. The burner is supplied with natural gas at a rate of 110 sm3/h and from the first stage of the fluidized bed cooler 23 with air at 650C, at a rate of 1200 sm3/h.
~ hen the high-temperature reaction has been completed after about 4 seconds, the gas-solids suspension is cooled by a supply of air, which is at a temperature of 470C and is supplied from the fluidized bed cooler 23 at a rate of 3500 sm3/h. The suspension is thus cooled to a temperature of 1020 C, at which the solids are sufficiently free flowable.
The gas-solids suspension are subsequently separated in the cyclone separator 22 into a gas, which is supplied at a rate of 4800 sm3/h as secondary gas to the fluidized bed reactor 10, and solids, which are supplied to the fluidized bed cooler 23.
~276~
In the fluidized bed cooler 23 the sollds are cooled in a plurality of successive stages to a final temperature of 80C. This is effected in the first stage in the di.rection of flow of the solids by means of air which is supplied at a rate of 1200sm3/h and is thus heated to 650C, in the second stage by means of air which is supplied at a rate of 2000 sm /h and is thus heated to 580 C, and in the third stage with water which is supplied at a rate of 20 m3/h and is thus heated from 35 to 65 C. The gas streams are recycled to the process as described hereinbefore. Alumina having a B.E.T. surface area of 3 m /g is produced at a rate of 5000 kg/h.
A circulating fluidized bed has the advantage that it can be operated at a high throughput rate per unit of cross sectional area of the reactor and in that such a long residence time can be selected for the solids to be heated that the chemical reaction combined with the preheating will virtually be completed. In such a case, only the high-temperature reaction proper must be carried out in the process in accordance with the invention so that said process will involve virtually no reactions which can be effected also at lower temperatures.
When the solids leaving the conveyor passage have been separated they are usually cooled further. Said further cooling may be accomplished by conventional coolers, preferably by fluidi~ed bed coolers.
In a preferred embodiment of the invention the high-temperature treatment carried out in accordance with the invention is so integrated in the overall process comprising the preheating and the final cooling of the solids that the several gas streams may be used interchangeably. For instance, oxygen-containing gas may be preheated in the cooler and may then be supplied to the solids-preheating stage and/or the high-temperature reaction stage. The ~'76fl~3~
exhaust gas from the conveyor passage may be supplied to the solids-preheating stage.
In an optimum overall process, the feedstock is preheated in a circulating fluidized bed, which is preceded by preheaters supplied with the exhaust gases, and the final cooling is carried out in a fluidized bed cooler, which comprises a plurality of successive cooling chambers, for through flow.
The solids may be directly and/or indirectly cooled with oxygen-containing gases, which are subsequently supplied as an entraining gas to the conveyor passage and/or as a fluidizing gas to the circulating fluidized bed. The fluidizing gases which have been used in the fluidized bed cooler may finally be used as a coolant in the pneumatic conveyor and the exhaust gases from the pneumatic conveyor may be used as secondary gas in the circulating fluidized bed.
The invention will be explained more in detail and by way of example with reference to the drawing and to the Examples.
The drawing is a flow scheme of a combined system of the kind described hereinbefore.
The solids to be treated are supplied by metering means l to a venturi heat exchanger 2, which is the last of a plurality of such exchangers in the gas flow path. In said last heat exchanger 2 the solids are heated by the available heat of the exhaust gas. The solids are separated from the gas in a cyclone separator 3 and are then supplied through a conveyor 4 to another preheating system, which consists of a venturi heat exchanger 5 and an associated cyclone separator 6 and of a venturi heat exchanger 7 and an associated cyclone separator 8. A by-pass line 9 can be used to supply ~ Z 7 Ei ~3 ,~
conveyed solids directly to the venturi heat exchanger 7 without passing through the preceding preheating stage.
From the cyclone separator 8, the solids are supplied to a circulating system, which consists of a fluidized bed reactor 10, a recycling cyclone 11 and a return line 12.
The fluidized bed reactor 10 is supplied with fuel through line 13, with fluidizing gas through line 14 and with secondary gas through line 15.
After a sufficiently long residence time the preheated suspension is supplied through line 16 to the lower portion of the conveyor passage 17 and is supplied from below into the burner flame, which is produced by means of fuel (line 18) and oxygen-containing gas (line 19). As the gas-solids suspension rises in the lower portion of the conveyor passage 17, the suspension is subjected to the high-temperature reaction and when said reaction has been completed the suspension is cooled by means of gases which are supplied through line 20. When the gas-solids suspension still flowing in the same direction has been sufficiently cooled, the suspension is discharged through line 21 and is separated in the cyclone separator 22 into solids supplied to the fluidized bed cooler 23 and gas supplied through line 15 as secondary gas to the fluidized bed reactor 10.
The fluidized bed cooler 23 is divided into a plurality of cooling chambers, which the solids flow through in succession. The cooler 23 comprises three cooling stages.
In the hottest stage, which is the first in the solids flow path, oxygen-containing gas is heated; that gas is subsequently supplied through line 19 to the conveyor passage 17. The second stage is used to heat the oxygen-~.~7~3~
containing gas which is subsequently supplied through line14 to the fluidized bed reactor lO. The third cooling stage is used for the final cooling of the solids by means of cooling water, which is supplied through a line 24 and discharged through line 25. The cooled product is discharged through a device 26. The fluidizing gas streams which have been used in the fluidized bed cooler 23 are collected and supplied as a coolant through line 20 to the conveyor passage 17.
Example Aluminum hydroxide which is moist after having been filtered is to be converted to highly burnt alumina.
Aluminum hydroxide having a moisture of 12% by weight is supplied at a temperature of 60 C and at a rate of 8690 kg/h through the metering means 1 to the venturi heat exchanger 2 and is subjected in said heat exchanger 2 to a heat exchange with the gases at 390 C which are supplied from the cyclone separator 6. As a result, the aluminum hydroxide is heated to 160 C and the gas is cooled approximately to the same temperature.
By the conve~or 4, the preheated aluminum hydroxide is contacted in the venturi heat exchanger 5 with the exhaust gases at 510C from the cyclone separator 8. This results in a heating of the solids and a cooling of the gas to about 390C. When the gas and solids have been separated in the cyclone separator 6, the solids are supplied to the venturi heat exchanger 7, which is supplied from the circulating fluidized bed with exhaust gases at 1150C. The thorough mixing action results in a gas-solids suspension at a temperature of 510C. After another separation of gas and ~2`76~3~
solids effected in the cyclone separator 8, the solids are supplied to the circulating fluidized bed.
The fluidized bed reactor 10 of the circulating fluidized bed is supplied through line 14 from the second stage of the fluidized bed cooler 23 with fluidizing air at 580C, at a rate of 2000 sm3/h, through line 15 from the cyclone separator 22 with secondary air at 1020 C, at a rate of 4800 sm3/h, and through line 13 with natural gas at a rate of 390 sm3/h. This results in a temperature of 1150 C, which is virtually constant throughout the circulating system consisting of the fluidized bed reactor 10, the recycling cyclone 11 and the return line 12.
lhe aluminum oxide is completely calcined within an average residence time of about 20 minutes. Thereafter, solids corresponding to the feeding rate are supplied through line 16 to the conveyor passage 17 and are heated to 1400C by the burner flame and by the flue gases from the burner. The burner is supplied with natural gas at a rate of 110 sm3/h and from the first stage of the fluidized bed cooler 23 with air at 650C, at a rate of 1200 sm3/h.
~ hen the high-temperature reaction has been completed after about 4 seconds, the gas-solids suspension is cooled by a supply of air, which is at a temperature of 470C and is supplied from the fluidized bed cooler 23 at a rate of 3500 sm3/h. The suspension is thus cooled to a temperature of 1020 C, at which the solids are sufficiently free flowable.
The gas-solids suspension are subsequently separated in the cyclone separator 22 into a gas, which is supplied at a rate of 4800 sm3/h as secondary gas to the fluidized bed reactor 10, and solids, which are supplied to the fluidized bed cooler 23.
~276~
In the fluidized bed cooler 23 the sollds are cooled in a plurality of successive stages to a final temperature of 80C. This is effected in the first stage in the di.rection of flow of the solids by means of air which is supplied at a rate of 1200sm3/h and is thus heated to 650C, in the second stage by means of air which is supplied at a rate of 2000 sm /h and is thus heated to 580 C, and in the third stage with water which is supplied at a rate of 20 m3/h and is thus heated from 35 to 65 C. The gas streams are recycled to the process as described hereinbefore. Alumina having a B.E.T. surface area of 3 m /g is produced at a rate of 5000 kg/h.
Claims (6)
1. A process of carrying out high-temperature reactions between a hot gas and previously heated solids, which are heated at a high temperature, at which they are no longer free flowable in a substantially vertical conveyor passage, whereafter the gas-solids suspension is cooled and solids are separated from the cooled suspension, characterized in that the preheated solids are supplied from below and in the direction of conveyance of the conveyor passage to and through a burner flame, which is disposed in the lower portion of the conveyor passage, and are subsequently caused to flow throughout the length of a sufficiently long reaction zone, and when the desired reaction has been completed the gas-solids suspension still flowing in the same direction is contacted behind the reaction zone with a separately introduced coolant and is thus cooled to a temperature at which the solids are free flowable.
2. A process according to claim 1, characterized in that the solids are preheated in a circulating fluidized bed which is supplied with oxygen-containing fluidizing gas and oxygen-containing secondary gas.
3. A process according to claim 1 or 2, characterized in that the solids are preheated with the aid of the exhaust gases from the conveyor passage.
4. A process according to claim 1 or 2, characterized in that the solids separated from the gas are cooled in a fluidized bed cooler.
5. A process according to claim 1 or 2, characterized in that the solids are cooled by a heat exchange with oxygen-containing gases, which are thus preheated and which are subsequently used in the solids-preheating stage and/or for the high-temperature reaction.
6. A process according to claim 1 or 2, characterized in that an oxygen-containing gas which has been indirectly preheated in the fluidized bed cooler is used as a fluidizing gas in the circulating fluidized bed and exhaust gas from the conveyor passage is used as oxygen-containing secondary gas in the circulating fluidized bed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3540206.7 | 1985-11-13 | ||
| DE19853540206 DE3540206A1 (en) | 1985-11-13 | 1985-11-13 | METHOD FOR CARRYING OUT HIGH TEMPERATURE REACTIONS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1276433C true CA1276433C (en) | 1990-11-20 |
Family
ID=6285845
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000521624A Expired - Lifetime CA1276433C (en) | 1985-11-13 | 1986-10-28 | Process of carrying out high-temperature reactions |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0222433B1 (en) |
| JP (1) | JPS62114642A (en) |
| AT (1) | ATE40923T1 (en) |
| AU (1) | AU582025B2 (en) |
| BR (1) | BR8605585A (en) |
| CA (1) | CA1276433C (en) |
| CZ (1) | CZ815386A3 (en) |
| DE (2) | DE3540206A1 (en) |
| ES (1) | ES2008033B3 (en) |
| GR (2) | GR880300146T1 (en) |
| HU (1) | HU206279B (en) |
| IN (1) | IN164695B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3725512A1 (en) * | 1987-07-29 | 1989-02-09 | Kettenbauer Gmbh & Co Verfahre | FLOATING GAS REACTOR |
| DE19750475C1 (en) * | 1997-11-14 | 1999-04-08 | Treibacher Schleifmittel Ag | High temperature treatment of very small particles |
| CN112858384B (en) * | 2021-01-08 | 2023-06-23 | 湖南中冶长天节能环保技术有限公司 | High-temperature detection-cooling treatment method and system for activated carbon flue gas purification device |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2350768C3 (en) * | 1973-10-10 | 1982-09-02 | Krupp Polysius Ag, 4720 Beckum | Process for firing or sintering fine-grained goods |
| DE2846584C2 (en) * | 1978-10-26 | 1984-12-20 | Klöckner-Humboldt-Deutz AG, 5000 Köln | Method and device for the heat treatment of fine-grained material |
| FR2465694A1 (en) * | 1979-09-24 | 1981-03-27 | Lafarge Sa | PROCESS FOR THE PRODUCTION OF PRODUCTS BASED ON CALCIUM SILICATES AND / OR ALUMINATES |
| ES8400999A1 (en) * | 1982-02-22 | 1983-12-16 | Empresa Nac Hulleras Norte | Manufacture of cement clinker |
| FR2554107B1 (en) * | 1983-10-28 | 1986-02-21 | Fives Cail Babcock | PROCESS AND APPARATUS FOR CALCINATION OF POWDERED MINERAL MATERIALS |
| JPS60156541A (en) * | 1984-01-27 | 1985-08-16 | Denki Kagaku Kogyo Kk | Melting furnace for producing molten spherical body of inorganic material |
| FR2563119B1 (en) * | 1984-04-20 | 1989-12-22 | Creusot Loire | PROCESS FOR THE CIRCULATION OF SOLID PARTICLES WITHIN A FLUIDIZATION CHAMBER AND IMPROVED FLUIDIZATION CHAMBER FOR IMPLEMENTING THE METHOD |
-
1985
- 1985-11-13 DE DE19853540206 patent/DE3540206A1/en not_active Withdrawn
-
1986
- 1986-03-03 IN IN157/CAL/86A patent/IN164695B/en unknown
- 1986-10-16 ES ES86201796T patent/ES2008033B3/en not_active Expired
- 1986-10-16 EP EP86201796A patent/EP0222433B1/en not_active Expired
- 1986-10-16 AT AT86201796T patent/ATE40923T1/en not_active IP Right Cessation
- 1986-10-16 DE DE8686201796T patent/DE3662164D1/en not_active Expired
- 1986-10-28 CA CA000521624A patent/CA1276433C/en not_active Expired - Lifetime
- 1986-10-29 JP JP61258082A patent/JPS62114642A/en active Pending
- 1986-11-11 CZ CS868153A patent/CZ815386A3/en unknown
- 1986-11-12 AU AU65040/86A patent/AU582025B2/en not_active Ceased
- 1986-11-12 BR BR8605585A patent/BR8605585A/en not_active IP Right Cessation
- 1986-11-12 HU HU864675A patent/HU206279B/en not_active IP Right Cessation
-
1989
- 1989-03-08 GR GR88300146T patent/GR880300146T1/en unknown
- 1989-05-23 GR GR89400069T patent/GR3000062T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| CZ815386A3 (en) | 1994-12-15 |
| GR880300146T1 (en) | 1989-03-08 |
| GR3000062T3 (en) | 1990-10-31 |
| EP0222433A1 (en) | 1987-05-20 |
| AU582025B2 (en) | 1989-03-09 |
| ATE40923T1 (en) | 1989-03-15 |
| IN164695B (en) | 1989-05-13 |
| ES2008033B3 (en) | 1989-07-16 |
| HUT45921A (en) | 1988-09-28 |
| JPS62114642A (en) | 1987-05-26 |
| AU6504086A (en) | 1987-05-21 |
| EP0222433B1 (en) | 1989-02-22 |
| DE3540206A1 (en) | 1987-05-14 |
| HU206279B (en) | 1992-10-28 |
| BR8605585A (en) | 1987-08-18 |
| DE3662164D1 (en) | 1989-03-30 |
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