A large and economical type of multi-stack
vertical tube evaporator (MS-VTE) is disclosed having units of multiple stacks of
vertical tube bundles or stages mounted in a
single vessel, and having its liquid feed pumped to the uppermost VTE bundle stack or stage and having the feed then cascading downward through the lower bundle stacks in series flow, and wherein all the tube bundles are heated with the same waste steam of no or low $-value, e.g. with
turbine reject steam in parallel flow under vacuum into the steam-sides of all tube bundles in the unit through a common steam conduit; and wherein the feed liquid is progressively evaporated from stage to stage or stack to stack and the vapors produced in the tubes of each bundle during the partial
evaporation of the feed are separated between the stacks and condensed by parallel flow into one or more condensers. Applied to
seawater desalination in a co-generation procedure with a coastal power
plant, this
evaporator produces about one pound of
distilled water per pound of
turbine reject steam used under vacuum and applied to single-effect mode in one
evaporator unit or several units mounted in a
single vessel with a condenser, to substantially reduce the cost of such useful
distilled water. When applied in a similar
cogeneration procedure but in a multi-effect series mode of several such units, or multiple units, the rate of
distilled water production can be increased several-fold based on the amount of
turbine reject steam applied.