You can use ASPEN for it with various assumptions. Generally the fluid bed accepts more flow than a fixed bed of the same size, but takes more power to run and causes abrasion and dust that has to be contained.

Usually fluid bed is used when heat of adsorption is high enough to damage the adsorbent. Heat is carried away by the turbulent flow.

thankyou

In general a fixed bed is preferred unless the absorbent (or catalyst for reactors) loses effectiveness quickly (or deactivates and need to be replaced without shutting down or if the heat release is high enough that it need to be dissipated in a well mixed adsordber  (or reactor) fluidized beds also scale up much better than fixed beds and are sometimes more cost effective for very large reactors 

Fluid bed allows a smaller reactor as long as the dust is practical to mitigate.

Operating cost is a factor if the adsorbent cost is high, and / or must be removed frequently. Installed cost of the design is a major factor. The cost of a design depends on if the adsorbent can be regenerated in place or is a waste, and if the break-through time is short or long, or if 100% removal is required.   At relatively low flows, the equipment, and construction costs are lower for a fixed bed system. Fluidization requires a gas recirculation system; blower, piping, sometimes  a cooling exchanger. Another problem is dust control. Attrition of the adsorbent can occur in a fluidized bed also.  Proper process design (especially at start-up) can make allowances to control temperatures, and optimize the time to change out. For removal of small concentrations of contaminants, dual beds (one off line in regeneration mode) are very good. if premature break-through of the contaminant can not be tolerated; 2 beds in series is required with the ability to swap beds. The second bed should always be the new one (to clean any break thru of the first). Careful calculations on the time to break through are needed. Proper contact time is needed. This is an area of the design where over design is desired. It is better to spend money on a larger vessel (to reduce velocity, and add residence time) than to be under-designed and not have a workable system. Pilot testing the application in the lab or pilot plant are the ways I use to ensure the design will work.  Design must eliminate the possibility of the bed short-circuiting (the treated gas must fill the total diameter of the bed). this is easier in a gas application than a liquid system.  

The books are written about it. A few remarks (different than above). In the fluidized bed reactor there are no problems with external heat and mass resistances. There are in fixed-bed reactor. There is problem with gas flow control  in  fluidized-bed reactor (steady gas flow). There is no with fixed-bed reactor. There is problem with temperature control in fixed-bed reactor. There is no in fluidized-bed reactor. There is problem with multiplicity in fixed-bed reactor ......... etc.

Regards,

thankyou all for you answer and valuable time.Actually its my first time to work on it and I have no idea so can anyone tell me where to start and also about the kinetic and mass transfere study too I am using calcium based sorbent in my thesis

If the treated gas flows are small and the bed needs to be larger, so that the treated gas flow is unable to fluidize the bed, then a recirculation flow is needed to make the bed work. if contamination levels are high or process upsets can occur, then the heat of adsorption can over heat the bed. In fixed beds with carbon, for example, surges of contaminants can heat the bed, and if flow is not kept running or the contaminant level decreased, the bed can thermally run away. I have seen this happen with NO2 gas on carbon. I know of fires produced from these circumstances. So, high heat of adsorption, with high contaminant flows, or low total gas flow can be a problem. Batch operation can lead to this problem. Attention to the heat balance and process operating conditions can identify this problem. with low contaminant levels and high process flow, this will not be a concern.

Start with a mass balance of the stream you want to treat. define upper and lower concentrations to study.

Pick a fixed bed to develop calculations for mass loadings (this will help you start a fluidized bed design later).

Decide if the bed is to be regenerated in place or run to break-thru, or exhaustion.

Decide on the amount of loading on the bed before regeneration or wasting.

Decide on the amount of break thru that is acceptable.

For a 2 bed system - Calculate a regeneration time, and cycle time to put the bed back online.

Optimize the sizes for two beds - loading time versus regen. time.

Develop equipment sizings for this with cost, then design a comparable fluidized design.

Determine which is cost effective, which gives the best removal, is easy to operate, ....

Fluidized bed is usually characterized by excellent internal mixing, so in ASPEN it would be reasonable to use CSTR reactor model. Fixed bed may theoretically belong to either CSTR or plug flow type (and transient regimes between them), but most probably plug flow model will be most sutable to use in ASPEN in this case. As told above, fluidized bed is more technically complicated and it would be reasonable to use in case of high heat effects only (in that case you will have to provide your reactor with external or internal heat exchanger). If you will work with fluids with low content of adsorbable species and, therefore, with low heat effect of adsorption, I recommend you to use fixed bed - it will be more simple and more reliable.