Liquid heaters and vaporizers – Miscellaneous
Patent
1983-10-14
1985-09-03
Yuen, Henry C.
Liquid heaters and vaporizers
Miscellaneous
110245, F22B 100
Patent
active
045385491
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to fast fluidized bed boilers. More particularly, the invention relates to novel and improved design and control features of such boilers.
TECHNOLOGICAL BACKGROUND
Fluidized bed boilers recently have become of great interest as a very attractive means of generating heat. Many bubbling or turbulent fluidized bed boilers have proved to operate very satisfactory.
However, when it comes to fast fluidized bed boilers, serious problems have to be solved, particularly with regard to heat transfer, particle separation and control of operation.
Thus, the common use of cyclone particle separators means that the boiler has to be built from separated parts and cooling systems. Also, cyclone particle separators have very huge dimensions, at least at high boiler powers, giving serious lay-out problems.
Also, existing power control systems which primarily control fuel feed as the load varies, tend to be inacurate and to give so-called over shoot.
It is previously known that ordinary fluidized bed boilers can be provided with other particle separators than cyclone particle separators; cf. for instance GB A No. 2 046 886 which discloses a fluidized bed boiler having a baffle type separator located in the effluent gas pass. The amount of separated material is of course very low.
However, with regard to fast fluidized bed boilers, those skilled in the art have been convinced that particle separators of the cyclone type are necessary in view of the very large amount of particles to be separated and the high velocity of the gas-particle mixture.
OBJECTS AND SUMMARY OF INVENTION
It is an object of this invention to provide a novel and improved fast fluidized bed system whereby the abovementioned problems are overcome and additional advantages are obtained, as will be apparent from the following.
The object of the invention is achieved by a fast fluidized bed boiler, as well as by a method of controlling such a boiler, having the novel and characterizing features defined in the accompanying claims.
According to a first important aspect of the invention, the boiler is designed as a completely cooled and integrated unit, including the primary particle separator, being a mechanical separator of a labyrinth type and not of the cyclone type.
Thus, it has been found that a mechanical primary particle separator of the labyrinth type can handle the very large amount of circulating material, while simultaneously being integrated both into a compact boiler structure and into one and the same cooling system.
According to a second important aspect of the invention, separated material is recirculated via a non-mechanical control valve, preferably so-called L-valve, thereby enabling an accurately controlled recirculation rate. In a preferred embodiment, separated material is collected in a material or particle storage prior to being recirculated into the reactor via said control valve. The storage can be integrated with the boiler.
According to a third important aspect of the invention, the boiler operation is controlled by maintaining the reactor bed temperature essentially constant, or within a relatively narrow temperature interval, by regulating the recirculation rate dependent on the boiler load.
The above-mentioned aspects, as well as further important features of the invention, will be more fully understood by the following description of presently preferred but nonetheless illustrative embodiments of the invention, when taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a preferred embodiment of a fast fluidized bed boiler in accordance with the invention.
FIG. 2 is a schematic perspective view of a fast fluidized bed boiler, generally in accordance with FIG. 1, further illustrating the novel design of the boiler.
FIGS. 3 and 4 are very schematic side and top views, respectively, of the upper part of a fast fluidized bed boiler according to the invention, illustrating the general operation of an integrated mechanical la
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Studsvik Energiteknik AB
Yuen Henry C.
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