Process Equipment and Plant Design
Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features
Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at all flow rates
Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for seive and valve trays than the bubble cap
Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provides the maximum flexible operating range
Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids
In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed due to large temperature changes
Plate tower is perferred, if interstage cooling is required to remove heats of reaction or solution
The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty
Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm²
Thickness of spherical shell is half that of the cylinderical vessel under same operating pressure condition. Besides, the ratio of surface area to volume is less for sphere than any other shape ; hen
Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm²
Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column
EXAMIANS