Adsorption vessels, design

The basic adsorption process design. Sub-tasks within that include the adsorbent selection, made in view of aU of the requirements imposed on the dehydration process. The adsorption step time, regeneration and cooHng step times all need to be settled and these in view of mechanical details. The overall vessel configuration, for example, the vessel ID and length, which quantities are typically sized based on pressure drop. Finally we need to make some estimate of the expected service Hfetime for the adsorbent product. 

Mechanical design of the adsorber then takes up the remainder of the engineering effort to produce a workable adsorption process design. Once a vessel is sized to provide the required inventory of adsorbenf we need to provide the mechanical details, which include flow distribution devices, bed supports and the required vessel wall thickness to withstand the working pressure and added stresses encountered during regeneration and repeated de-pressurization and re-pressurization. 

Attrition of activated carbon can be minimized by proper design of the adsorption vessels. The air-flow rate should be below 100 ft/min., preferably below 60 ft/min., and good air distribution to the top of the bed should be provided. Plugging of activated carbon beds can be prevented by eliminating any sources of carbon attrition and providing an adequate screen or filter ahead of the adsorption vessel. 

FIG. 16-46 Pressurized adsorber vessel. (Reptinted with peirrussion of EPA. Reference EPA, Process Design Manual for Carbon Adsorption, U.S. Envir. Protect. Agency., Cincinnati, 1973.)... 

An apparatus with high sensitivity is the heat-flow microcalorimeter originally developed by Calvet and Prat [139] based on the design of Tian [140]. Several Tian-Calvet type microcalorimeters have been designed [141-144]. In the Calvet microcalorimeter, heat flow is measured between the system and the heat block itself. The principles and theory of heat-flow microcalorimetry, the analysis of calorimetric data, as well as the merits and limitations of the various applications of adsorption calorimetry to the study of heterogeneous catalysis have been discussed in several reviews [61,118,134,135,141,145]. The Tian-Calvet type calorimeters are preferred because they have been shown to be reliable, can be used with a wide variety of solids, can follow both slow and fast processes, and can be operated over a reasonably broad temperature range [118,135]. The apparatus is composed by an experimental vessel, where the system is located, which is contained into a calorimetric block (Figure 13.3 [146]). 

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