Vertical bed

Adsorption is performed most commonly in fixed vertical beds of porous granular adsorbents. Flow of adsorbing fluid usually is down through the bed, that of regenerant usually is upward. Moving and fluidized beds have only a limited application in the field. 

Figure 15.17. Two designs of fixed bed gas adsorbers, (a) Vertical bed with balls on top for hold-down and distribution of feed (Johnson, Chem. Eng. 79, 87 (27 Nov. 1972)]. (b) Horizontal fixed bed for low pressure drop operation [Treybat, Mass Transfer Operations, McGraw-Hill, New York, 1980 Logan, U.S. Pat. 2,180,712 (1939)].

An alternative to the above method is to introduce one of the reactants at a given vertical bed height and to measure steady-state conversion at the bed outlet by varying the height. This method, named the differential reactivity test, was suggested by T. Kikuchi and applied experimentally to catalytic hydrogenation of ethylene by Furusaki et al. (F18). 

The feed enters the top of the static vertical bed reactor. Level sensors automatically interrupt the loading when the reactor is filled to the proper level. Whenever the wood feed level drops below a second selected level, the load auger automatically runs until the full load level is reached. 

Milling (end, form, slab) Flat and contoured surfaces and slots Milling machine— horizontal, vertical, bed-type Multiple points... 

In a bubbling fluidized bed the coefficient of heat transfer between bed and immersed surfaces (vertical bed walls or tubes) can be considered to be made up of three components which are approximately additive (Botterill, 1975). 

FTGURC 5—2 A vertical-bed temperature profile shows if the catalyst needs to be changed. 

Vertical installations are used when there is a need to obtain lower resistivities, when there are difficulties with trenching for a horizontal bed, or when the physical surface area is limited. Generally, due to their length, vertical bed anodes are brittle and must be carefully handled to prevent breakage. Figure 13.14 shows a typical local distributed vertical anode system. The anode cable is prone to failure if the insulation is damaged in any way. As a result, particular care should be exercised in handling the anode leads. 

The flow direction for adsorption in a vertical fixed bed is determined not only by the potential for lifting or fluidizing the bed but also by whether the feed is a gas or a liquid. For gas and vapour phase applications velocities which cause crushing of an adsorbent tend to be much higher than those required to lift a bed and therefore it is convenient to arrange to have the highest flowrate in the downwards direction through a vertical bed. 

---