Reboiler consists of a horizontally mounted TEMA K-shell and a tube bundle comprised of either U-tubes or straight tubes (regular or finned) with a pull-through (type T) floating head. The tube bundle is unbaffled, so support plates are provided for tube support. Liquid is fed by gravity from the column sump and enters at the bottom of the shell through one or more nozzles. The liquid flows upward across the tube bundle, where boiling takes place on the exterior surface of the tubes. Vapor and liquid are separated in the space above the bundle, and the vapor flows overhead to the column, while the liquid flows over a weir and is drawn off as the bottom product.
Low circulation rates, horizontal configuration and all-vapor return flow make kettle reboilers relatively insensitive to system hydraulics. As a result, they tend to be reliable even at very low (vacuum) or high (near critical) pressures where thermosyphon reboilers are most prone to operational problems. Kettles can also operate efficiently with small temperature driving forces, as high heat fluxes can be obtained by increasing the tube pitch. On the negative side, low circulation rates make kettles very susceptible to fouling, and the over-sized K-shell is relatively expensive.
