Shell and tube heat exchanger

Abstract

Shell and tube apparatus (1) comprising: an outer shell (2); a first tube bundle (3) and a second tube bundle (4) coaxial with each other; a first inner shell (5) and a second inner shell (6); the first inner shell surrounds the first tube bundle and is arranged between said two tube bundles; the second inner shell surrounds the second tube bundle and is arranged in the space between said second tube bundle and the outer shell (2); the first tube bundle (3) operates as a preheater; the second tube bundle (4) operates as a boiler; the coaxial inner shells (5, 6) define a counterflow path for a hot fluid which passes through the shell side.