Desorption steam stripping

PuraSiv HR A process for removing solvent vapors from air by adsorption on beaded activated carbon contained in a combined fluidized moving bed. For water-soluble solvents, the gas used for desorption is nitrogen and the process is known as PuraSiv HR, Type N (not to be confused with PuraSiv N) for chlorinated hydrocarbons, steam stripping is used and the process is known as PuraSiv HR, Type S. Developed by Kureha Chemical Company and now marketed by the Union Carbide Corporation. The process was originally known as GASTAK because it was developed by the Taiyo Kaken Company, subsequently acquired by Kureha Chemical Company. It is also marketed by Daikin Industries under the name Soldacs. 

STRATEX, or the stratified temperature extractor technology, is an integrated ex situ soil treatment technology that uses solidification/stabilization, thermal desorption, and steam stripping. 

The operations described above require mass transfer of a substance from the gas stream to the liquid. When mass transfer occurs in the opposite direction (i.e., from the liquid to the gas) the operation is called desorption, or stripping. For example, the benzene and toluene are removed from the absorption oil mentioned above by contacting the liquid solution with steam, whereupon the aromatic vapors enter the gas stream and are carried away, and the absorption oil can be used again. Since the principles of both absorption and desorption are the same, we can study both operations simultaneously. 

Steam stripping, which is widely used in the regeneration of solvent recovery systems using an activated carbon adsorbent, can be considered as a combination of thermal swing and displacement desorption. Vacuum desorption, which is used in some versions of the Union Carbide IsoSiv process for separation of medium-chain linear paraffins as well as in some air separation systems can be considered as a special case of pressure swing. 

In the rectification section, below the feed point, the lighter components are stripped from the adsorbed phase while the heavier components are concentrated in the adsorbed phase. Desorption of the heavier components is accomplished by steam stripping in the bottom section of the column in which the temperature is raised to 510°F by a dowtherm heat exchanger and live... 

Another example is absorbing SO2 from the flue gases by absorption in alkaline solutions. In the hydrogenation of edible oils in the food industry, hydrogen gas is bubbled into oil and absorbed. The hydrogen in solution then reacts with the oil in the presence of a catalyst. The reverse of absorption is called stripping or desorption, and the same theories and basic principles hold. An example is the steam stripping of nonvolatile... 

The removal of a volatile species, gas or a vapor, from a nonvolatile ahsorhent or solvent hy an inert gas or vapor or by simple heating is called stripping. When air is used as the inert gas, the process is called air stripping, in the case of steam, the term steam stripping is used. The word desorption is also employed. 

Stripping Equations Stripping, or desorption, involves the removal of a volatile component from the hquid stream by contact with an inert gas such as nitrogen or steam. In this case the change in concentration of the liquid stream is of prime importance, and it... 

As the spent catalyst falls into the stripper, hydrocarbons are adsorbed on the catalyst surface, hydrocarbon vapors fill the catalyst pores, and the vapors entrained with the catalyst also fall into the stripper. Stripping steam, at a rate of 2 to 5 lbs per 1,000 lbs (2 kg to 5 kg per 1,000 kg,) is primarily used to remove the entrained hydrocarbons between catalyst particles. Stripping steam does not address hydrocarbon desorption and hydrocarbons filling the catalyst pores. However, reactions continue to occur in the stripper. These reactions are... 

Regeneration of a chemically reactive solvent is a process of chemical desorption the chemical reaction which has taken pla ce in the absorption step takes place in the reverse direction in the regeneration step, and the absorbed gaseous components are desorbed back to a stripping gas phase, which is usually steam. 

An important point to be discussed with regard to chemical desorption is the question of the required steam rate. The steam injected into the regeneration unit serves two purposes it provj des the sensible and latent heat required for the desorption oper tion, and it represents the diluent gas needed to keep the partial pressure of acid gas in the gas phase low enough to allow strippiiig to take place. Consequently, the required steam rate may be dict ted either by the heat balance, or by stripping operation. The minimum steam rate needs to be calculated for both requirements, and the actual minimum is the larger one of the two. 

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