1. A transmission system comprising at least a satellite station and a connection station for connecting the system to a switched network, in which system at least one of said stations includes means for receiving speech messages transmitted in frames and a speech message correction device for modifying the speech signal frames as a function of the quality of the transmission, which system is characterized in that the speech message correction device includes a counter of bad frames, an attenuation circuit for diminishing the amplitude of the speech signals for a count of said counter that is higher than a predetermined value.
2. A satellite station suitable for a system as claimed in claim 1, including a message correction device, characterized in that the speech message correction device has a counter for counting bad frames, an attenuation circuit for diminishing the amplitude of the speech signals for a count of said counter that is higher than a predetermined value.
3. A connection station suitable for a system as claimed in claim 1, including a message correction device, characterized in that the speech message correction device includes a counter for counting bad frames, an attenuation circuit for diminishing the amplitude of the speech signals for a count of said counter that is higher than a predetermined value.
4. A method of improving the quality of the speech messages implemented in a system as claimed in claim 1 or in a station as claimed in claim 2 or 3, characterized in that it comprises the following steps:
counting of bad frames,
diminishing the signals when the count of bad frames exceeds a predetermined value.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A method of controlling heat transfer in a fluidized bed reactor, said fluidized bed reactor having:
a heat transfer chamber (12,312,412,512) with a bed (14,314,414,514) of solid particles therein, means (22,322,422,522) for introducing fluidizing gas into the heat transfer chamber for fluidizing said bed of solid particles therein and heat transfer surfaces (16,316,416,516) in contact with said bed of solid particles in said heat transfer chamber; whereby
heat is transferred to said heat transfer surfaces from solid particles in said heat transfer chamber, while the fluidization of the bed of solid particles in the heat transfer chamber is varied according to a periodical function, the improvement comprising
the flow velocity of fluidizing gas being continuously introduced into the heat transfer chamber is periodically varied between two or more different positive flow velocities, for controlling the instantaneous heat transfer from solid particles to said heat transfer surfaces in said heat transfer chamber.
2. The method defined in claim 1, wherein the fluidization of the solid particle bed is varied by varying a parameter of the flow velocity function of the fluidization gas being continuously introduced into the heat transfer chamber.
3. The method defined in claim 1, wherein the flow velocity of gas being continuously introduced into the heat transfer chamber is alternated between a first and a second flow velocity, said first flow velocity being higher than the second velocity, said first flow velocity thereby providing a higher heat transfer from the solid particles to the heat transfer surfaces than the second flow velocity.
4. The method defined in claim 1, wherein the flow velocity of gas being introduced into the heat transfer chamber is varied periodically according to a step-wise or saw-tooth function or a sin-function.
5. The method defined in claim 1, wherein the flow velocity of gas being introduced into the heat transfer chamber is varied periodically between an upper and lower limit velocity, where for fine bed materials, such as bed material in a circulating fluidized bed reactor, the upper limit being >0.2 ms, preferably >0.25 ms and the difference between the upper and lower limit being >0.1 ms, preferably >0.15 ms.
6. The method defined in claim 1, wherein the flow velocity of gas being introduced into the heat transfer chamber is varied periodically between an upper and lower limit velocity, where for coarse materials, such as solid material in an ash cooler, the upper limit being >0.4 ms, preferably >0.5 ms and the difference between the upper and lower limit being >0.2 ms, preferably >0.25 ms.
7. The method defined in claim 1, wherein
the flow velocity of gas being introduced into the heat transfer chamber is varied periodically between an upper and lower limit velocity and
the instantaneous heat transfer coefficient, for heat being transferred from solid particles in said heat transfer chamber to said heat transfer surfaces, at said lower limit velocity is less than 60% of its maximum value and at said upper limit velocity more than 80% of its maximum value.
8. The method defined in claim 1, wherein the flow of gas being introduced into the heat transfer chamber is varied between a high velocity gas flow and a low velocity gas flow, and the duration of high velocity gas flow sub-period is constant and duration of low velocity gas flow sub-period is varied, for controlling heat transfer in the heat transfer chamber.
9. The method defined in claim 8, wherein the duration of low velocity gas flow is <30 s, preferably between 0 to 10 s.
10. The method defined in claim 1, wherein flow of gas being introduced into the heat transfer chamber is varied between a high velocity gas flow and a low velocity gas flow, and the duration of a low velocity gas flow sub-period is constant and the duration of a high velocity gas flow sub-period is varied, for controlling heat transfer in the heat transfer chamber.
11. The method defined in claim 1, wherein the flow of fluidizing gas being introduced into at least a first and a second zone of the heat transfer chamber is controlled separately, for preventing periodic thermal disturbances in the system.
12. The method defined in claim 1, wherein said fluidized bed reactor further comprises a processing chamber, such as a combustion chamber, in solid particle flow communication with said heat transfer chamber, and heat generated in the combustion chamber is recovered with heat transfer surfaces in said heat transfer chamber.
13. The method defined in claim 12, wherein the heat transfer chamber is an ash cooler and heat is recovered from ash discharged from the fluidized bed reactor.
14. The method defined in claim 1, wherein said fluidized bed reactor is a circulating fluidized bed reactor, including a reactor chamber and a solid particle separator, and said heat transfer chamber is connected to a return duct connecting said particle separator to a lower part of said reactor chamber, and heat generated in the combustion chamber is recovered with heat transfer surfaces in said heat transfer chamber.
15. The method defined in claim 1, wherein
change in heat transfer need is monitored and
said means for introducing fluidizing gas into the heat transfer chamber is controlled to provide the monitored change in heat transfer need.
16. The method defined in claim 1, wherein
the temperature of heat transfer medium, such as hot water or steam, provided by said heat transfer surfaces, is monitored and compared to a preset value, and
the duration of high velocity gas flow sub-periods and low velocity gas flow sub-periods is altered according to a preset program to provide the desired heat transfer in said heat transfer chamber, for said temperature to reach the preset value.
17. Apparatus for controlling heat transfer in a fluidized bed reactor, said fluidized bed reactor having:
a heat transfer chamber (12,312,412,512) with a bed (14,314,414,514) of solid particles therein,
means (22,322,422,522) for introducing fluidizing gas into the heat transfer chamber for fluidizing said bed of solid particles therein,
heat transfer surfaces (16,316,416,516) in contact with said bed of solid particles in said heat transfer chamber,
means (34,334,434,534) for varying the flow velocity of fluidizing gas for varying the fluidization of the bed of solid particles in the heat transfer chamber according to a periodical function, characterized by
the means for introducing fluidizing gas including means for continuously introducing fluidizing gas into the heat transfer chamber, and
the means for varying the flow velocity including means for periodically varying the flow velocity of fluidizing gas being continuously introduced into the heat transfer chamber between two or more different flow velocities.
18. An apparatus according to claim 17, wherein said means for varying the fluidization include
means (32,332) for monitoring the need of change of heat transfer in the heat transfer chamber, and
means (38,338) for processing said monitored need of change of heat transfer into a change of parameter of periodical flow velocity.
19. An apparatus according to claim 18, wherein
said means for monitoring the need or need of change of heat transfer in the heat transfer chamber includes temperature measuring means, arranged to measure the temperature of heat transfer medium having transported heat out from the heat transfer chamber.
20. An apparatus according to claim 17, wherein
said means for varying the fluidization include a valve means (26,326) for controlling the velocity of gas flow being introduced into the beat transfer chamber.
21. An apparatus according to claim 17, wherein said fluidized bed reactor further comprises a processing chamber (312,412,512), such as a combustion chamber, in solid particle flow communication with said heat transfer chamber.
22. The apparatus according to claim 21, wherein the heat transfer chamber (512) is an ash cooler for discharging coarse solid bed material from the processing chamber.
23. The apparatus according to claim 17, wherein said fluidized bed reactor is a circulating fluidized bed reactor, including a reactor chamber (312) and a solid particle separator (311), and said heat transfer chamber (312) is connected to a return duct (313) connecting said particle separator to a lower part of said reactor chamber.