Regeneration of the loaded adsorbents

After volumetric flow measurement (FT) the crude helium gas is fed to the station. Atthe outlet of each individual adsorber G1-G4 the pressure is measured (PT) and maintained in the pure helium flow (PC). The desorption of impurities from the adsorbent respectively the regeneration of the loaded adsorber is controlled via purging steps with pure helium and via flow respectively pressure control of the residual gas (FC). Pressure or flow fluctuations of the residual gas are dampened by a buffer tank (b). 

Adsorption processes and ion-pair extraction processes can also be used to remove color from wastewater [117-119]. The main problem to be solved in adsorption processes is the further treatment of the loaded adsorbents (regeneration, disposal). A similar situation is found in ion-pair extraction, where a concentrated organic phase results from the process and further treatment of this product is required. 

Adsorption by activated carbon is commonly employed for the removal of TNT from aq waste streams, eg, pink water formed in shell-loading operations. Low efficiency in regeneration of the carbon for reuse has led to a study of the factors involved (Ref 99), with conclusions as follows. The TNT is adsorbed at many of the numerous high-energy sites on the surface of the carbon. Basic materials, introduced during activation of the carbon by combustion and oxidation and also present at these sites, then induce oxidation-reduction reactions of the methyl with the nitro groups in the TNT. This is... 

The pressure drop over the filter increases continuously with time until the moment, when a critical soot load has accumulated on the filter surface. Self-ignition of the soot then occurs, which in addition depends on the exhaust gas temperature, the filter temperature, the oxygen concentration, the type and amount of the volatiles adsorbed onto the carbonaceous soot matrix, and the packing density of the soot on the filter surface. The soot-laden filter bums free, the pressure drop decreases and the loading/regeneration cycle repeats itself again, as shown in Fig. 15.4. 

Supercritical fluid extraction (SFE) is a suitable process for many separation problems. The regeneration of the supercritical fluid is as important as the extraction step itself Therefore this paper presents a method to do this in a more isobaric way than the customary pressure reduction regeneration. For the example of soil remediation we have investigated the activated carbon regeneration of supercritical carbon dioxide loaded with the low-volatile polycyclic aromatic hydrocarbon (PAH) pyrene. Characteristics of supercritical fluid extraction for soil remediation are elevated temperatures and pressures up to 370 K and 300 bar. For this reason adsorption isotherms of pyrene on activated carbon up to these conditions are measured first. Subsequently this method is used to regenerate carbon dioxide in a closed solvent cycle plant with a 4 1 extractor. An economic analysis using these results indicate that the soil remediation costs will decrease for about 20 - 30 % by means of an activated carbon adsorber. 

The technical application of high-silica molecular sieves without any non-framework aluminium as protective layer restricts the water loading of the stream in sorption processes. The use of supersaturated steam for the regeneration of the adsorbent is impossible since already after a few adsorption/desorption cycles the molecular sieve is totally damaged. However, adsorbents which are modified by surface alumination are remarkably more resistant against water. 

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