AU2003209752B2

AU2003209752B2 - Methods and devices for heating a continuous flow of solids

Info

Publication number: AU2003209752B2
Application number: AU2003209752A
Authority: AU
Inventors: Paul Goedert; Yvan Kroemmer; Louis Schmit
Original assignee: Paul Wurth SA
Current assignee: Paul Wurth SA
Priority date: 2002-02-01
Filing date: 2003-01-27
Publication date: 2007-03-29
Anticipated expiration: 2023-01-27
Also published as: EP1470379A1; JP2005525525A; KR20040077659A; WO2003064950A1; DE50302535D1; JP4098247B2; ATE319064T1; EP1470379B1; LU90888B1

Abstract

A pneumatically conveyed flow of solids is continuously introduced into a pressurized container (42) in which a fluidized bed is maintained by adding an aerating gas, said bed being heated by heat exchange with a heat transfer medium (58). The mixture of solid/gas is continuously removed from the fluidized bed and separated into a lean gas phase and a highly compressed solid /gas mixture by gravitational or centrifugal deposition. The highly compressed solid/gas mixture is then continuously discharged into a pneumatic conveyor line (221) and conveyed pneumatically. The solid content of the pressurized container (42) is continuously monitored. Via a controlled gas removal (68) from the lean gas phase the continuos discharge of the highly compressed solid/gas mixture into the pneumatic conveyor line (221) is controlled in such a manner that the solid content of the pressurized container (42) remains substantially constant.

Description

P-PWU-476WO PROCESS AND APPARATUSES FOR HEATING A CONTINUOUS STREAM OF SOLIDS The present invention relates to a method for heating a continuous stream of solids, and to apparatuses for carrying out this method.

Prior art It is known to heat pneumatically conveyable solids, such as for example coal dust, in a fluidized-bed heat exchanger. Fluidized-bed heat exchangers of this type comprise a pressure vessel in column form, in which a loosening gas flows through a bed of solid particles from below. The solid particles in the bed are supported by the loosening gas flowing upward, so that what is known as a fluidized bed is maintained. The fluidized bed is heated by heat exchangers which are immersed in or surround the fluidized bed.

WO 99/24773 has described a fluidized-bed heat exchanger of this type.

The solid which is to be heated is conveyed to the heat exchanger in a pneumatic conveying line and is fed continuously into the fluidized bed at the lower end of the heat exchanger. At the upper end of the heat exchanger, the fluidized bed flows into a discharge apparatus for the solid. This discharge apparatus comprises a star feeder which discharges the solid continuously. The gas which collects at the upper end of the heat exchanger is extracted in such a manner that a constant excess pressure prevails in the heat exchanger. The extracted gas is purified in a cyclone.

In many processes, there is a need for the solid to be pneumatically conveyed onward after it has been heated in the fluidized-bed heat exchanger.

It would therefore be advantageous if a heated solids/gas mixture could be introduced direct from the'fluidized-bed heat exchanger into a pneumatic conveying line. However, it has been observed that this procedure cannot always achieve stable pneumatic conveying. The reason for this appears primarily to be the fact that the solids/gas mixture which is taken off from the fluidized bed may have very variable levels of solids in it.

Nowadays, when coal dust is being blown into a blast furnace, there is a demand for the coal dust to be heated to temperatures of over 2000C before it is blown into the blast furnace. In the process, the coal dust loses a large proportion of its pore moisture content, with the result that relatively large and very variable quantities of steam are released. In the event of heating to temperatures of over 2000C, the gas phase, which comprises the released steam, the conveying gas and the loosening gas, to be heated, expands considerably. To enable the coal dust which has been heated in the fluidizedbed heat exchanger to be conveyed onward pneumatically without problems, it has hitherto been necessary for the heated material stream first of all to be discharged from the fluidized bed into a degassing vessel via a lock device, so that the gas phase could be taken off from the degassing vessel. The coal dust is then discharged from this degassing vessel into a fluidization apparatus, which feeds it into a pneumatic conveying line, with the mass throughput of coal dust in the pneumatic conveying line being controlled. Of course, the degassing vessel with entry lock, the fluidization apparatus and the mass throughput control apparatus make the installation much more expensive.

Object of the invention It is an object of the present invention to propose a method which can be used to heat a continuous stream of solids and convey it onward directly by pneumatic means, but in which sufficient stability of pneumatic conveying must be ensured.

Summary of the invention A pneumatically conveyable stream of solids is introduced continuously into a pressure vessel, in which a fluidized bed is maintained by the addition of a loosening gas, this fluidized bed being heated by heat exchange with a heat transfer medium. According to the invention, a solids/gas mixture is continuously removed from the fluidized bed and divided, by gravity or centrifugal force separation, into a weakly laden gas phase and a highly compressed solids/gas mixture. The highly compressed solids/gas mixture is then discharged continuously into a pneumatic conveying line, in which it is conveyed onward pneumatically. The solids content of the pressure vessel is continuously monitored. The continuous discharge of the highly compressed solids/gas mixture into the pneumatic conveying line is controlled, by means of controlled gas take-off from the weakly laden gas phase, in such a manner that the solids content of the pressure vessel always remains substantially constant.

This method can be used to heat a continuous stream of solids and to convey it onward directly by pneumatic means, ensuring good stability of the pneumatic conveying.

The proposed method is eminently suitable, for example, for heating and drying a pneumatically conveyable solid which, by virtue of hygroscopicity, has water bound to it. In this case, the solid is heated in the fluidized bed in such a manner that a large proportion of this water evaporates in the fluidized bed and is converted into the gas phase. It should be noted that the proposed method makes it possible for the heated solid then to be conveyed onward directly by pneumatic means, while ensuring good stability of the pneumatic conveying, which has hitherto been considered impossible.

For example, the proposed method can advantageously be applied to coal dust which has been dried at a temperature of less than 1000C upstream of the pressure vessel, so that its surface moisture content on entering the fluidized bed is negligible, but its pore moisture content is still relatively high. In the fluidized bed, at temperatures between 1500C and 2500C, this coal dust loses the majority of its pore moisture content. In this case, the proposed method makes it possible for the strongly heated coal dust to be conveyed onward directly by pneumatic means, while ensuring good stability of the pneumatic conveying, which has hitherto been considered impossible.

In an advantageous embodiment, the pressure vessel comprises a fluidized-bed heat exchanger and a degassing column. The stream of solids is introduced continuously into the lower end of the fluidized-bed heat exchanger.

A fluidized bed is maintained in this fluidized-bed heat exchanger by the addition of a loosening gas, the fluidized bed being heated by heat exchange with a heat transfer medium. At the upper end of the fluidized-bed heat exchanger, a heated solids/gas mixture from the fluidized bed overflows into the degassing column, where the overflow solids/gas mixture forms a fluidized bed which has been highly compressed under the action of the force of gravity, with the separated gas phase collecting in the upper end of the degassing column.

The highly compressed fluidized bed is discharged continuously into the pneumatic conveying line at the lower end of the degassing column. This continuous discharge of the highly compressed fluidized bed into the pneumatic conveying line is in this case controlled by controlled gas take-off at the upper end of the degassing column. The highly compressed fluidized bed can be loosened at the lower end of the degassing column by the addition of a gas before being discharged into the pneumatic conveying line. In this embodiment, a change in the solids content is advantageously recorded by a change in the height of the highly compressed fluidized bed in the degassing column.

In a further advantageous embodiment, the pressure vessel only comprises a fluidized-bed heat exchanger. The solids stream is introduced continuously into the lower end of the fluidized-bed heat exchanger. A fluidized bed is maintained in this fluidized-bed heat exchanger by the addition of a loosening gas, the fluidized bed being heated by heat exchange with a heat transfer medium. A heated solids/gas mixture is removed from the upper end of the fluidized bed via a cyclone, with the cyclone dividing the removed solids/gas mixture into a weakly laden gas phase and a highly compressed solids/gas mixture by centrifugal force. The highly compressed solids/gas mixture is introduced continuously into the pneumatic conveying line. The throughput of the solids/gas mixture into the pneumatic conveying line is controlled by controlled gas take-off in the cyclone. In this embodiment, a change in the solids content is advantageously recorded by a change in the height of the fluidized bed in the fluidized-bed heat exchanger.

Advantageous apparatuses for carrying out these variants of the method are likewise proposed.

List of figures Various configurations of the invention will now be described with reference to the appended figures, in which: Fig. 1: shows a simplified installation diagram for blowing in coal dust for a blast furnace, having a first configuration of an apparatus according to the invention for heating the pneumatically conveyed coal dust; Fig. 2: shows an enlarged excerpt from Fig. 1, showing the structure of the apparatus for heating a pneumatically conveyed solid, in diagrammatic longitudinal section; Fig. 3: shows a diagrammatic longitudinal section through a second configuration of an apparatus according to the invention for heating a pneumatically conveyed solid; Fig. 4: shows a cross section on section line 4-4' from Fig. 3; and Fig. 5: shows an enlarged excerpt from Fig. 3.

Description of preferred configurations of the invention with reference to the figures Fig. 1 shows a greatly simplified installation diagram for blowing coal dust into a blast furnace 10. A parenthesis mark bearing reference numeral 12 overall denotes an installation for the preparation of the coal dust. This installation 12 comprises, in a known way, a storage hopper 14, a lock vessel 16 and a blow-in vessel 18. The coal dust 20 is stored in the storage hopper 14 and if appropriate dried at temperatures below 100 0 C. A plurality of pneumatic conveying lines 221, 222, 223, 224, are connected to this blow-in vessel 18.

Each of these pneumatic conveying lines 221, 222, 223, 224, in this case supplies a tuyere 241 of the blast furnace 10, in which the coal dust is blown into the blast furnace 10. To control the mass throughput of the coal dust, each pneumatic conveying line 221, 222, 223, 224, comprises a control apparatus 261. In Fig. 1, this control apparatus 261 in the pneumatic conveying line 221 is illustrated by a mass throughput meter 28 and a throughput control valve 30. It should also be noted that the coal dust in the pneumatic conveying lines 22 1, 222, 223, 224, is preferably conveyed in a dense stream, so that gas and energy consumption and also the wear are minimized. In this context, densestream conveying is to be understood as meaning a solids loading of at least kg of solid per kg of conveying gas.

Reference numeral 40 denotes an apparatus for heating the pneumatically conveyed coal dust, which is installed in the pneumatic conveying lines 221 (the section of the pneumatic conveying line 221 downstream of the apparatus 40 is in this case provided with reference symbol 22'1). This apparatus 40 is intended to heat the coal dust which is conveyed in the pneumatic conveying line 221, 22'1 to temperatures of between 150'C and 300 0 C before it is blown into the blast furnace The apparatus 40 from Fig. 1 will now be described in more detail with reference to Fig. 2. It comprises two pressure vessels 42, 44 in column form, the first pressure vessel 42 forming a fluidized-bed heat exchanger and the second pressure vessel 42 forming a degassing column. It should be noted that each of the two pressure vessels 42, 44 in column form have a height of several meters.

At its lower end, the fluidized-bed heat exchanger 42 has a fluidizing apparatus 46 with a gas connection 48 for a loosening gas. A fluidizing apparatus 46 of this type comprises, for example, a porous fluidization base which is known per se and via which the loosening gas (which in the case of coal dust is preferably an inert gas, such as for example nitrogen), is distributed uniformly over the entire cross section of the pressure vessel 42 in column form.

The coal dust from the pneumatic conveying line 221 is introduced into the pressure vessel 42 via a solids inlet device 52 immediately above the fluidization base 50. The loosening gas which flows in via the porous fluidization base 50 in this case carries the solids particles upwards. A fluidized bed 54 which has properties similar to those of a liquid is formed in the pressure vessel 42 in column form. This fluidized bed 54 extends from the fluidization base up to a transverse connection 56 which connects the top ends of the two pressure vessels 42, 44 in column form. The solids/gas mixture overflows from the fluidized bed 54 into the second pressure vessel 44 through this transverse connection 56. In a continuous operating state, the solids mass throughput in the transverse connection 56 corresponds to the solids mass throughput in the pneumatic conveying line 22. Accordingly, a fluidized bed 54 with a height of several meters, in which the coal dust particles move slowly from the bottom upward, is maintained in the first pressure vessel 42. This fluidized bed 54 is heated by a heat exchanger, which in Fig. 2 is formed by a double-walled jacket 58. This jacketed heat exchanger 58 surrounds the fluidized bed 54 over most of its height, and a heat transfer medium, normally a heat transfer oil, flows through it from the top downward.

The fluidized-bed heat exchanger 42 is preferably designed in such a manner that the temperatures and residence times in the fluidized bed 54 ensure that the majority of the pore moisture content of the coal dust evaporates in the fluidized bed 54. This is normally achieved at temperatures of 1500C to 2500C, residence times of 2 to 4 minutes and a pressure in the pressure vessel of approximately 6 to 8 bar. It can be assumed that in this case between 0.05 and 0.1 kg of steam would be released per kg of coal dust, which at a pressure of 8 bar and a temperature of 200'C corresponds to a gas volume of between 0.012 and 0.024 m 3 per kg of coal dust.

In the second pressure vessel 44 in column form, which forms the degassing column, the solids/gas mixture which overflows from the fluidized bed 54 through the transverse connection 56 is highly compressed under the force of gravity. In the process, a highly compressed fluidized bed 60 is formed in the degassing column 44, with the separated gas phase collecting at the upper end 62 of the degassing column 44. At the lower end, the degassing column 44 has a discharge apparatus 64 for continuously discharging the highly compressed fluidized bed 60 into the pneumatic conveying line 22'. This discharge apparatus 64 advantageously comprises a loosening apparatus 66 which is acted on by gas and loosens the highly compressed fluidized bed before it is discharged into the pneumatic conveying line 22'.

The continuous discharge of the highly compressed fluidized bed 60 out of the degassing column 44 into the pneumatic conveying line 22'1 is in this case controlled by means of a controlled gas take-off 68 at the upper end 62 of the degassing column 44 in such a manner that the solids content of the apparatus 40 remains substantially constant. For this purpose, the controlled gas take-off 68 has a control valve 70, a controller 72 and a measurement probe 74. The measurement probe 74 records a change in the height of the highly compressed fluidized bed 60 in the degassing column 44. Examples of suitable measurement probes 74 include capacitive level meters, or microwave level meters. In the event of an increase in the height of the highly compressed fluidized bed 60, the controller 72 causes less gas to be taken off via the control valve 70. As a result, the gas pressure in the degassing column 44 rises and the discharge apparatus 64 discharges more coal dust into the pneumatic conveying line 22'. In the event of a decrease in the height of the highly compressed fluidized bed 60, the controller 72 causes more gas to be taken off via the control valve 70. As a result, the gas pressure in the degassing column 44 drops and the discharge device 64 discharges less coal dust into the pneumatic conveying line 22. This control therefore ensures that the solids stream which is discharged continuously from the apparatus 40 corresponds to the solids stream which is introduced continuously into the apparatus 40. In this way, a stable, dense-stream conveying of the coal dust can be achieved in the pneumatic conveying line 22'1 downstream of the device 40. The gas which is extracted from the upper end 62 of the degassing column 44 can, as shown in Fig. 1, be returned to the storage hopper via a line 76, where it contributes to preheating of the coal dust before being discharged to atmosphere via a filter apparatus 78.

An apparatus 140 for heating a pneumatically conveyed solid which represents an advantageous alternative to the apparatus 40 shown in Fig. 1, since it comprises just one pressure vessel 142 in column form, will now be described with reference to Figures 3 to 5. The pressure vessel 142 likewise has a height of several meters and forms a fluidized-bed heat exchanger. The pressure vessel 142 in column form, like the pressure vessel 42 in column form, has a fluidization apparatus 146 with a gas connection 148 for a loosening gas at its lower end. A fluidization apparatus 146 of this type comprises, for example, a porous fluidization base 150 which is known per se and via which the loosening gas, which in the case of coal dust is preferably an inert gas, such as for example nitrogen, is distributed uniformly over the entire cross section of the pressure vessel 142 in column form. The coal dust from the pneumatic conveying line 221, which comes from the installation 12 for the preparation of the coal dust, is introduced into the pressure vessel 142 directly above the fluidization base 150 via a solids inlet apparatus 152. The loosening gas which flows in via the porous fluidization base 150 in this case carries the solids particles upward. A fluidized bed 154 is formed, extending in the pressure vessel 142 in column form from the fluidization base 150 into the upper end of the pressure vessel 142. Accordingly, a fluidized bed 154 with a height of several meters, in which the coal dust particles move slowly from the bottom upward, is maintained in the pressure vessel 142. This fluidized bed 154 is heated by a heat exchanger which is formed by a double-walled jacket 158 in Fig. 3. This jacketed heat exchanger 158 surrounds the fluidized bed 154 over the majority of its height, and a heat transfer medium, normally a heat transfer oil, flows through it from the top downward. Like the fluidized-bed heat exchanger 42, the fluidized-bed heat exchanger 142 is also preferably designed in such a manner that temperatures and residence times which ensure that the majority of the hygroscopically bound water evaporates in the fluidized bed 154 are achieved in the fluidized bed 154.

A heated solids/gas mixture is removed from the fluidized bed 154 via a cyclone 161 at the upper end of the fluidized bed 154, with the removed solids/gas mixture being divided into a weakly laden gas phase and a highly compressed solids/gas mixture by centrifugal force. The cyclone 161 is advantageously arranged inside the pressure vessel 142 in column form, the cyclone having an inlet 163 for the removal of a solids/gas mixture from the fluidized bed 154, a first outlet 165 for a compressed solids/gas stream and a second outlet 167 for the weakly laden gas stream. The first outlet 165 and the second outlet 167 lead out of the pressure vessel 142 in column form in a pressure-tight manner. It should be noted that the cyclone 161, on account of being arranged inside the pressure vessel 142, does not itself have to be designed as a pressure vessel.

The first outlet 165 of the cyclone 161 opens out directly into the pneumatic conveying line 22'1 which leads to the blast furnace 10. Therefore, a highly compressed solids/gas mixture is introduced continuously into the pneumatic conveying line 22'1 via this first outlet 165.

The throughput of the highly compressed solids/gas mixture into the pneumatic conveying line 22'1 is in this case controlled by means of a controlled gas take-off through the second outlet 167 of the cyclone 161, in such a manner that the total solids content of the apparatus 140 remains substantially constant.

For this purpose, the second outlet 167 has a control member 170, which is designed as a throttling apparatus, for the controled take-off of a weakly laden gas stream from the cyclone 161. This control member 170, together with a controller 172 and a measurement probe 174, forms a control circuit. The measurement probe 174 records a change in the height of the fluidized bed 154. In the event of an increase in this height, the controller 172, via the throttling apparatus 170, throttles the second outlet 167, so that less gas is taken off via the cyclone 161. As a result, the gas pressure rises, which causes the mass throughput in the first outlet 165 of the cyclone 161 to rise. In the event of a decrease in the height of the fluidized bed 154, the controller 172 reduces the throttling of the second outlet 167 via the throttling apparatus 170, so that more gas is taken off via the cyclone 161. As a result, the gas pressure in the cyclone 161 drops, which causes the mass throughput in the first outlet 165 of the cyclone 161 to be reduced. This control therefore ensures that the solids stream which is discharged continuously from the apparatus 140 corresponds to the solids stream which is introduced continuously into the apparatus 140. In this way, stable pneumatic conveying of the coal dust can be achieved in the pneumatic conveying line 22'1, i.e. downstream of the apparatus 140.

An advantageous configuration of the cyclone 161 will now be described with reference to Figs. 4 and 5. This cyclone comprises a separation chamber 180 having a tangential inlet chamber 182 which forms the inlet 163 in the fluidized bed 152. The separation chamber 180 tapers conically downward and merges into the first outlet 165. It is connected, via a pipe 184, to a flange 186 which is secured in a gastight manner to a mating flange 188 of the pressure vessel 142. The second outlet 167 is arranged centrally in the separation chamber 180. It is formed by a vertically displaceable inlet connection piece 200 which extends through the pipe 184 and leads out of the pressure vessel 142 in a sealed manner. The vertical displacement of the inlet connection piece 200 is effected by means of an actuating drive 202 arranged outside the pressure vessel 142 (cf. Fig. A stationary closure body, which projects centrally into the lower exit of the inlet connection piece 200, is denoted by reference numeral 204. Here, it interacts with a reduced passage opening 206 of the inlet connection piece 200, in such a manner that the closure body 204 constricts the passage opening 206 to a greater or lesser extent, i.e. throttles the second outlet 167 to a greater or lesser extent, depending on the vertical position of the inlet connection piece 200.

It remains to be noted that the height measurement of the fluidized bed 54, 154 described hereinabove is very likely to be the most simple way of recording a change in the solids content in the apparatuses 40 and 140. If necessary, it can be refined by one or more density measurements carried out on the fluidized bed 54, 154. It is even within the scope of the present invention for a change in the solids content in the apparatuses 40 and 140 to be recorded using other measurement methods, such as for example a weight measurement.

Claims

1. A method for heating a continuous stream of solids, wherein: a stream of solids is introduced continuously into a pressure vessel; a fluidized bed is maintained in this pressure vessel by the addition of a loosening gas; and the fluidized bed is heated by heat exchange with a heat transfer medium; characterized in that a solids/gas mixture is continuously removed from the fluidized bed and is divided, by gravity or centrifugal force separation, into a weakly laden gas phase and a highly compressed solids/gas mixture; the highly compressed solids/gas mixture is discharged continuously into a pneumatic conveying line, and is therein conveyed onward pneumatically; the solids content of the pressure vessel is continuously monitored, and the continuous discharge of the highly compressed solids/gas mixture into the pneumatic conveying line is controlled, by means of a controlled gas take-off from the weakly laden gas phase, in such a manner that the solids content of the pressure vessel remains substantially constant.

2. The method as claimed in claim 1, wherein: in the event of an increase in the solids content in the pressure vessel, less gas is taken off from the weakly laden gas phase; and in the event of a decrease in the solids content of the pressure vessel, more gas is taken off from the weakly laden gas phase.

3. The method as claimed in one of claims 1 to 2, wherein the solid, by virtue of hygroscopicity, has water bound to it, and wherein the solid is heated in the fluidized bed in such a manner that a large proportion of this water evaporates in the fluidized bed and is converted into the gas phase.

4. The method as claimed in claim 3, wherein: the solid is a coal dust which has been dried upstream of the pressure vessel at a temperature of less than 100'C, so that its surface moisture content on entering the fluidized bed is negligible, but its pore moisture content is still relatively high; and the coal dust loses the majority of its pore moisture content in the fluidized bed at temperatures between 1500C and 250 0 C. The method as claimed in one of claims 1 to 4, wherein: the pressure vessel comprises a fluidized-bed heat exchanger and a degassing column; the solids stream is introduced continuously into the lower end of the fluidized-bed heat exchanger; a fluidized bed is maintained in this fluidized-bed heat exchanger by the addition of a loosening gas; the fluidized bed is heated by heat exchange with a heat transfer medium; a heated solids/gas mixture from the fluidized bed overflows into the degassing column at the upper end of the fluidized-bed heat exchanger; the overflow solids/gas mixture in the degassing column forms a fluidized bed which has been highly compressed under the action of the force of gravity, wherein the separated gas phase collects in the upper end of the degassing column; the highly compressed fluidized bed is discharged continuously into the pneumatic conveying line at the lower end of the degassing column; and the continuous discharge of the highly compressed fluidized bed into the pneumatic conveying line is controlled by controlled gas take-off at the upper end of the degassing column.

6. The method as claimed in claim 5, wherein: the highly compressed fluidized bed is loosened at the lower end of the degassing column by the addition of a gas before it is discharged into the pneumatic conveying line.

7. The method as claimed in claim 5 or 6, wherein: a change in the height of the highly compressed fluidized bed in the degassing column is recorded; in the event of an increase in this height, less gas is taken off from the upper end of the degassing column; and in the event of a decrease in this height, more gas is taken off from the upper end of the degassing column.

8. The method as claimed in one of claims 1 to 4, wherein: the pressure vessel comprises a fluidized-bed heat exchanger; the solids stream is introduced continuously into the lower end of the fluidized-bed heat exchanger; a fluidized bed is maintained in this fluidized-bed heat exchanger by the addition of a loosening gas; the fluidized bed is heated by heat exchange with a heat transfer medium; a heated solids/gas mixture is removed from the upper end of the fluidized bed via a cyclone, the cyclone dividing the removed solids/gas mixture into a weakly laden gas phase and a highly compressed solids/gas mixture by centrifugal force; the highly compressed solids/gas mixture is introduced continuously into the pneumatic conveying line; and the throughput of the solids/gas mixture into the pneumatic conveying line is controlled by a controlled gas take-off in the cyclone.

9. The method as claimed in claim 8, wherein: a change in the height of the fluidized bed in the fluidized-bed heat exchanger is recorded; in the event of an increase in this height, less gas is removed from the cyclone; and in the event of a decrease in this height, more gas is removed from the cyclone. The method as claimed in claim 8 or 9, wherein the cyclone is arranged in the fluidized bed.

11. The method as claimed in one of claims 8 to 10, wherein: the cyclone has an adjustable nozzle for the take-off of the weakly laden gas stream.

12. An apparatus for carrying out the method as claimed in one of claims 5 to 7, comprising: a first pressure vessel (42) in column form, having a lower end and an upper end, which forms the fluidized-bed heat exchanger and comprises at least the following parts: a feed means (52) for a solids stream at the lower end of the first pressure vessel (42) in column form; a fluidization apparatus (46) in the lower end of the first pressure vessel (42) in column form, for maintaining a fluidized bed (54) in the first pressure vessel (42) in column form; a heat exchanger (58) for heating the fluidized bed (54); a second pressure vessel (44) in column form, having a lower end and an upper end, which forms the degassing column and comprises at least the following parts: a discharge device (64) at the lower end of the degassing column for continuously discharging the highly compressed fluidized bed into the pneumatic conveying line 22 and a controllable gas take-off apparatus (68) at the upper end of the degassing column (44) for taking off the gas stream from the weakly laden gas phase in a controlled manner; and a connection (56) between the two upper ends of the two pressure vessels (42 and 44) in column form, so that the solids/gas mixture at the upper end of the fluidized-bed heat exchanger can overflow from the fluidized bed (54) into the degassing column (44).

13. The apparatus as claimed in claim 12, comprising: a measurement probe (74) for measuring the height of the highly compressed fluidized bed (60) in the degassing column and a control circuit for controlling the controllable gas take-off apparatus (68) as a function of the measured height of the highly compressed fluidized bed (60) in the degassing column (44).

14. The apparatus as claimed in claim 12 or 13, wherein the discharge apparatus comprises a loosening apparatus which is acted on by gas.

15. An apparatus for carrying out the method as claimed in one of claims 8 to 11, comprising: a pressure vessel (142) in column form, having a lower end and an upper end; a feed means (152) for feeding in a solids stream at the lower end of the pressure vessel (142) in column form; a fluidization apparatus (146) in the lower end of the pressure vessel (142) in column form, for maintaining a fluidized bed (154) in the pressure vessel (142) in column form; a heat exchanger (158) for heating the fluidized bed (154); and a cyclone (161) which is arranged in the upper end of the pressure vessel (142) in column form, the cyclone having an inlet (163) for the take-off of a solids/gas mixture from the fluidized bed (154), a first outlet (165) for a compressed solids/gas stream, and a second outlet (167) for a weakly laden gas stream, the first and second outlets (165, 167) leading out of the pressure vessel (142) in column form in a pressure-tight manner, and the second outlet (167) has a control member (170) for the controlled take-off of a weakly laden gas stream.

16. The apparatus as claimed in claim 15, comprising: a measurement probe (174) for measuring the height of the fluidized bed (154) in the degassing column; and a control circuit for controlling the control member for the take-off of the weakly laden gas stream as a function of the height measured by the measurement probe (174).

17. The apparatus as claimed in claim 15 or 16, wherein the cyclone comprises the following parts: a separation chamber (180) having a tangential inlet chamber (163) which forms the inlet in the fluidized bed (154), the separation chamber (180) tapering conically downward and merging into the first outlet (165), and the second outlet (167) being arranged centrally in the separation chamber (180).

18. The apparatus as claimed in claim 17, wherein the control member (170) is designed as a throttling apparatus in the entry of the second outlet (167).

19. The apparatus as claimed in claim 18, wherein the throttling apparatus is formed by a stationary, central closure body (204) and a vertically displaceable inlet connection piece (200) with a reduced passage opening (206), and the closure body (204) constricts the passage opening (206) to a greater or lesser extent depending on the vertical position of the inlet connection piece (200).