Fluidized bed combustion boiler

Claim 1

A circulating fluidized bed combustion boiler for producing steam from water containing a substantial proportion of dissolved solids, comprising, a substantially vertical elongated combustion chamber, circulation means for circulating a combusting fluidized bed upwardly through said combustion chamber from the lower end thereof to the upper end thereof, said circulating means including means for withdrawing gasses and entrained solids from the upper end of said combustion chamber and for separating solids from said fluidized bed after passage through said combustion chamber and for storing said solids for return to said combustion chamber at the lower end thereof, and tube means arranged in a single layer around the outer periphery of said combustion chamber, said tube means comprising at least one coiled tube with the convolutions thereof being joined by a web throughout substantially the entire length of said tube, said means including inlet means positioned toward the lower end of said combustion chamber and including outlet means positioned toward the upper end of said combustion chamber and being of a configuration to provide an ascending helical flow path for fluid passing therethrough and such that the region of higher steam quality in said tube means coincides with the region of lowest heat transfer coefficients, and means for establishing a flow of fluid in said tube means to result in a steam quality and flow velocity sufficient to prevent deposition of solids on said tube means.