Adsorber Station

The residual traces of water and other components, such as odorants, are removed in regenerative adsorbers filled with molecular sieve or silica gel and activated carbon. Typically the unit operates according to the following automatic sequence  

Adsorption, expansion, regeneration, cooling, pressure build-up and adsorption again in possibly parallel operation, (see also Sections 2.2.4 and 2.2.5.6). 

For the regeneration of the adsorbent either residual gas of the rectification or dried CO2 is used. But air can also be used for regeneration of adsorbers. In this case the cooling is normally done with dry CO2 or residual gas to sweep the air from the adsorbent The regeneration gas is heated to about 200 °C either electrically or by means of steam. By these means, the components adsorbed on the molecular sieve as well as on the activated carbon are desorbed. The regeneration gas is then emitted to the atmosphere. If only water is desorbed by means of dry COj, it can be recycled to the compressor to improve the recovery rate. 

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Fig. 4.2 Diagram of a four-bed pressure swing adsorber station.

If hydrogen and neon are contained in the crude gas to the helium recovery plant, the separation of these components in a pressure swing adsorber station is not possible, since they behave similar to helium. Hydrogen can then be... 

Stations 23 and 24, located in the LSLE, have been subjected to hypoxic conditions since the 1980s. With depletion of oxygen in the bottom waters, the sediment oxygen penetration depth decreased, and Fe oxides, concentrated in the oxic sediment layer, were reductively dissolved and released adsorbed arsenic. Hence, the low oxygen levels during the last 25 years in the bottom waters is reflected in more reducing conditions in the sediment and increases in both dissolved and HA-extractable Fe and As. 

The effluent from the ion exchange station is adjusted, if necessary, to the desired pH level (4.5 to 4.8) before it is further decolorized with activated carbon. This step is usually carried out in two stages and the adsorbent is utilized countercurrently. Thus, the virgin carbon is applied to the liquor concentrated to about 50 to 55% solids and this once used adsorbent is re-used on the more dilute effluent from the ion exchange station. The liquor must be filtered thoroughly to remove all traces of carbon prior to concentration, in vacuo, to about 74% solids. 

Needle valve N4 allows a slow bleed of adsorbate to the out septum and then to a sample cell positioned at the outgassing station. The slow flow of gas through this part of the circuit provides a source of adsorbate for the purpose of signal calibration and as a purge for the outgassing station holding cell S2. 

Since PCBs are generally adsorbed on the particle surface, the concentration in sediment and soil samples is much more likely to be related to the particle surface area per volume unit than to the mass unit (16). For this reason, the concentration of each sample, expressed in pg g (dry weight), was normalized by dividing it by the relevant CS, expressed in square meters of surface per cubic centimetre of dry sample (m cm ), as obtained by particle size analysis (5). Table 9.9 shows the normalized mean concentration of the seven selected congeners along with the total and the normalized total mean PCB concentration. In this case, the calculated value of the total PCB content was very close to the experimental one (the difference was always lower than 10%). Table 9.10 shows the total mean PCB concentration and the normalized mean PCB concentration for each matrix analysed. In four stations where marine sediments were collected at different depths, a concentration of about 100-200 (pg g )/(m cm ) was generally observed in a surface layer of about 10-15 cm, while in deeper layers PCBs were below the LoDs. These results show that the normalized total mean PCB content in marine sediment samples was 150 (pg g )/(m cm ) and did not show any significant difference from open sea to the coastal line. Lake sediment and soil samples showed a normalised total mean PCB content of 240 and 130 (pg g )/(m cm ) which did... 

Stations and Inglesia [44] simulated for comparison the ordered surface of a crystal obtained by cutting the bulk material, the unrelaxed cut-off amorphous surface, as well as the latter relaxed. The last case was the random structure created by the Monte Carlo sphere packing method. They calculated the adsorption potential surface for some weakly bound adsorbates (N2, Ar, CH4) with the aim of judging the fidelity of the surface models by comparison with the available experimental data on the heats of adsorption and surface diffusivity. The adsorption energy profile in Fig. 5.12 gives an interesting look of the surface from the point of view of the problems discussed in this book the concrete data will be called for an analysis in later sections. 

Studies have been made of continuous systems. In the hypersorption process, a vertical column contains a bed of carbon that continuously moves downward. Raw gas enters at a point midway in the column. As the smaller hydrocarbon molecules are less adsorbable they flow upward to be collected and recovered at the top of the column whereas the larger hydrocarbon molecules are adsorbed and are carried with the carbon to the discharge at the bottom. The adsorbed hydrocarbons are recovered at a heating station and the denuded carbon is returned to the top of the column to repeat the cycle.25... 

A. S. Joy Fiiel Research Station, London) Experiments at the Fuel Research Station have shown that if carbon monoxide is added to a surface fully covered with adsorbed hydrogen at temperatures above 50°, no reaction takes place, but nearly all the hydrogen is displaced from the surface. Presumably, any 1 1 complex is unstable at these temperatures, and in the absence of sufficient gas phase hydrogen immediately decomposes. This result parallels that of Eley and Couper on the displacement of chemisorbed hydrogen by carbon monoxide. 

Assume the propane filling station can charge the bed with a propane supply pressure of 2 = 10 atm and the bed is exhausted at a propane partial pressure of Fi = 0.1 atm. We are interested in selecting an adsorbent material that maximizes the amount of propane that desorbs while changing from P2... 

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