Pittsburgh Activated Carbon at work..·
Vapor Phase Adsorption . . . how it works for industry! Vapor Phase Adsorption
with high retentivity of the product once it has been adsorbed. Considering that adsorption is reversible, the carbon must have high retentivity characteristics so that the vapors, once adsorbed, are not desorbed when the concentration of the adsorbate in the gas passing through the carbon vessels varies. Particle size distribution is another important factor which significantly affects the rate of adsorption. Where high superficial linear velocities of gases are encountered, smaller carbon particles (within pressure drop limitations) are desired to offer sharper gas separations with a minimum of "bleed through." The proper selection of the particle size aids the carbon-gas contact and thus increases the transfer of the adsorbate to the internal pore structure of the carbon particle, resulting in a faster rate of adsorption.
ÎUPER
Vapor phase adsorption deals with the recovery and/or purification of gases using activated carbon. In vapor phase applications there are certain param eters to be considered in order to pro vide a better understanding of the adsorption process. Vapor phase adsorption is essentially a gas-solid equilibrium process where the approach to equilibrium is governed by the rate of adsorption. As such, proc ess conditions that shift the equilibrium towards saturation usually prove most effective. In addition, the adsorption of vapors on activated carbon is closely related to condensation. Consequently, as the system approaches the dew-point of the adsorbate, the adsorption system be comes more efficient. For this reason, it is generally accepted that a vapor phase adsorption system should operate at the Regeneration highest pressure and the lowest temper Carbon regeneration is basically accomature within the process limitations. plished by raising the temperature of the carbon and sweeping out the adsorbate Adsorbent Considerations To provide for the ultimate adsorption vapors with an inert carrier gas. When system efficiency, one of the most critical the temperature of the carbon has been components of the system is, of course, increased to a point where the energy the adsorbent itself. Particle size, surface of adsorption has been overcome, vaporarea, and pore size distribution are the ization of the adsorbate takes place and important carbon factors to consider. it is eluted from the carbon into the For example, in the adsorption of gases sweeping regenerating gas stream. The whose molecular dimensions are rela more efficient the heat transfer in the tively small, activated carbons with the system, the more effective the recovery bulk of the pore surface area in the 17-20 of the adsorbate. Steam is generally used for the reactiAngstrom unit range will provide greater vation of vapor phase activated carbon, efficiency. in that it is inexpensive, is universally The controlled pore structure of Pitts available, inert and has a low vapor presburgh TYPE BPL Carbon permits high sure at ambient conditions. Furthermore, carbon adsorption capacities, coupled steam is readily condensable and can be readily separated from the adsorbate in the liquid phase by simple decanting or RECOMMENDED MAXIMUM distillation. It is important to consider GAS VELOCITIES FOR that one pound of steam carries more SYSTEM PRESSURE BTU's than an equal weight of nitrogen or carbon dioxide, which again, proΕ 60 vides additional economies. When dealing with anhydrous sysË50 tems, such as anhydrous hydrogen chloο ride or natural gas, it is possible to UJ40 regenerate carbon with hot recycled in> ert gas, or with the use of hot process S 30 gas that has already been through the ζ carbon system. In these applications, the same rules of condensation and separaο tion apply for the recovery of the solvent.
Some GAS PRESSURE, psig
Applications
In fixed bed adsorbers, Pittsburgh TYPE BPL Granular Activated Carbon is cur-
A typical vertical cylindrical vessel
rently being used in the separation of LPG and gasolines from natural gas. This application offers a highly efficient and economical means for the recovery of hydrocarbons from lean natural gases that heretofore, had been impractical with ordinary recovery methods. Similarly the removal of organic sulphur compounds and other sulphur compounds from natural gas prior to its use in such applications as ammonia processing is accomplished quite effectively. By removing the sulphur compounds from natural gas prior to reforming, the valuable catalyst is protected from poisoning due to the sulphur, so that plant yields are increased and catalyst replacement costs are decreased. This application has broad uses not only in natural gas but in preparing any reactant gas for catalysis. Another major application for Pittsburgh Activated Carbons is in the recovery of valuable solvents, where recovery rates in excess of 95% plus are not uncommon. For more detailed information on actual applications of Pittsburgh TYPE BPL Activated Carbon in vapor phase adsorption, write for Pittsburgh's brochure "Processing Natural Gas for an Even Greater Profit . · ·" There's no obligation, of course· »«»
PITTSBURGH ACTIVATED CARBON CO. CALOON CENTER · PITTSBURGH. P A . 1 5 2 3 0 A SUBSIDIARY OP CALOON CORPORATION
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