Combined heat exchanger system such as for ammonia synthesis reactor effluent

#The field of the present invention relates to heat exchangers and more particularly to heat exchanger systems in which a process fluid stream passes through two successive heat exchange steps where heat is exchanged between the fluid stream and two exchange fluids, and in which the operating conditions or physical properties such as temperature, corrosiveness, etc. of the fluid stream are aggressive with respect to ordinary materials of construction.

#The successive exchange of heat between a fluid stream and two or more exchange fluids is practiced in many processes. The most common equipment configuration is a separate shell and tube heat exchanger for each exchange fluid with the fluid stream passing to successive exchangers through connecting pipes. For a typical shell and tube heat exchanger, the fluid stream may pass through either the shell side or the tube side of the exchanger, the best choice depending on the specific circumstances.

#An example for successive heat exchange is found in an ammonia synthesis system such as that described in U.S. Pat. No. 4,744,966, where effluent gas (fluid stream) from a reactor is cooled in a first heat exchanger by exchange with reactor feed gas and then in a second exchanger by exchange with steam, the fluid stream flowing from the first exchanger to the second exchanger through connecting pipe.

#FIG. 1 diagrammatically illustrates a combined heat exchanger system in accordance with the present invention, as applied to the cooling of the effluent of an ammonia synthesis reactor;

#FIG. 2 is a detailed cross-sectional view of a combined heat exchanger, including a protective overlay;

#FIG. 3 is a cross-sectional view of an alternative combined exchanger having a protective shroud;

#The preferred embodiments will now be described with reference to the drawings. To facilitate description, any numeral representing an element in one figure will represent the same element in any other figure.

#FIG. 1 is a diagrammatic view of a combined exchanger 10 according to the present invention which as an example is used to cool the effluent of ammonia synthesis reactor 5. The ammonia synthesis reactor 5 is vertically supported on reactor support 7 and is connected to the combined exchanger 10. The combined exchanger 10 is oriented horizontally and is supported by a brace 9 which permits axial movement to accommodate thermal expansion.

#FIG. 2 illustrates details of the combined exchanger 10. The combined exchanger 10 has a first feed-effluent exchanger section 20 and a high temperature heat sink exchanger section 50 within shell 22, the two sections being separated by a tubesheet 36. Hot reacted gas from the reactor 5 passes through a conduit 44 into an exchanger head 40 of the first exchanger section 20 through an expansion means such as expansion joint 42. The first exchanger section 20 includes a tube bundle 30 extending between tubesheets 36 and 38. The hot reacted gas passes through the tubes 32 and through the tubesheet 36 into the shell side of the second exchanger section 50.