Adsorption process design vessels

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. 

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.)... 

During the adsorption process, a device (reactor, dryer, etc.) is filled with a porous solid designed to remove gases or liquids from a mixture. Typically the process is run in parallel with a primary and secondary vessel. The adsorber can be activated alumina or charcoal. A variety of adsorption materials can be used. The adsorption material has selective properties that will remove specific components of the mixture as it passes over the adsorber. A stripping gas is used to remove the stripped components from the adsorption material. 

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]). 

Pressure swing adsorption is a commercial process for separating fluids based on their different affinities for an adsorbent. A sequence of steps involves more than one vessel ("bed") packed with adsorbent. Bed No. 1 receives the feed at the high supply pressure while bed No. 2 is opened to the low exhaust pressure. When Bed No. 1 becomes saturated with desired product (the undesired product leaves the bed at the exit), the supply is switched to Bed No. 2, and Bed No. 1 is opened to the low pressure so that the desired product is recovered. In the meantime desired product collects in Bed No. 2. After Bed No. 2 is saturated, the supply is again shifted back to Bed No. 1, and so on. More than two beds can be employed, and the specific design of the system and operating conditions are based on economical operation to conserve compression energy. 

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