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SCHMIDT'SCHE® QUICK QUENCHER TRANSFER LINE EXCHANGERS
Schmidt'sche® Quick Quencher Transfer Line Exchangers are multi-tube exchangers having a number of double tube registers welded together to form an exchanger tube bundle which accommodates two or four gas inlets that connect to a set of furnace coils. An oblong type quick quencher and a circular type are illustrated.
The water/steam mixture flows through the oval header ends through which it flows to the annulus between the inner and outer tube to quench the process gas. The novel design of the quick quencher was co-developed and patented by ABB Lummus and Schmidt'sche designers. The process gas flows directly from the furnace coils to a defined number of TLE tubes via an aerodynamic ceramic insert. The insert first decelerates the gas through a diffuser and is then uniformly distributed to the tubes as it reaccelerates through a nozzle section.
Using three-dimensional Computational Fluid Dynamics (CFD) Modeling the contour of the insert is properly designed to eliminate flow separation and dead zones that would otherwise promote coke formation and increase residence time.
The Quick Quencher connects up to 12 TLE tubes to one furnace coil outlet. This arrangement provides for a high heat exchanged surface area to volume ratio that translates to rapid quenching of the gas in a single exchanger without the need of a second process cooling stage, hence an additional second process cooling stage, hence an additional secondary TLE.
The Quick Quencher inlet design significantly reduces the residence time between furnace coil outlet and the exchanger tube inlet to the range between 10-12 milliseconds compared to 40 milliseconds in Conventional TLEs. It does not have a "tube sheet" facing the gas flow; thereby, avoiding the inherent drawbacks of erosion, pressure drop and coke formation.
Typical pressure drop through the Schmidt'sche® Quick Quencher is in the same range as Schmidt'sche® Conventional and Bathtub TLEs at less than 1.45 psi (0.1 bar).