Propane separation

The above applies to both binary and multicomponent distillation. In multicomponent distillation, once the above are specified, other components will distribute according to the equilibrium relationship. Frequently, a product spec sets the maximum concentration of impurities that can be tolerated in the product. Product specs are less than" specifications. The one impurity which is dependent on the column separation and is most difficult to achieve sets the composition specification in the column. This is illustrated in Table 3.1 for a propylene-propane separation (Ca splitter). Since the light nonkeys (hydrogen, methane, ethylene, ethane, and oxygen) end up in the distillate, their concentration in the distillate is independent of the column. Of the others, the most difficult purity to achieve sets the composition specification, Similarly, the heavy nonkeys (MAPD, C4 and... 

A zeotropic and extractive distillations have been used through the years in the chemical industry to separate mixtures where the relative volatility of the key components is very close, or equal, to unity. Applications from the classical dehydration of alcohol with benzene (1) to more recent ones such as the propylene-propane separation (2) and aromatics recovery from hydrocarbon mixtures with N-methylpyrrolidone (3), indicate a continuous interest through the years in this area. 

Natural Gas Litfuids NGL) Liquefied hydrocarbons, usually ethane and propane, separated from natural gas. 

Figure 17.2. Specifications for a propylene-propane separation process.

Tyreus and Luyben investigated the application of double-effect distillation o the separation of methanol from water and to the propane separation problem... 

It is perhaps of greater practical interest to compare the daily utility costs of the double-effect and single-effect processes for propylene-propane separation. We assume the following costs and use electric motors for all compressors and pumps. 

Table 17-3 Dally utility costs for propylene-propane separation...

Vapor produced in the condenser is compressed back to column bottom pressure before entering the column. Figure 17.13 shows the application of this scheme to the propylene-propane separation problem. The bottoms liquid is flashed to 72psia to remove the required heat in the condenser. Additional heat added during isentropic compression is insufficient to make up the difference between reboiler and condenser duties. Therefore, the auxiliary steam-heated reboiler is needed. 

For the propylene-propane separation shown below, calculate ... 

Figure 17.7. Double-effect distillation process for propylene-propane separation.

Figure 9.22 Distillation system for propylene-propane separation. Table 9.4 Properties for Propylene-Propane Separation...

Figure 9.23 Low-temperature distillation with reboiler-liquid flashing for propylene-propane separation.

Chng ML, Xiao Y, Chung TS, Toriida M, Tamai S. Enhanced propylene/propane separation by carbonaceous membrane derived from poly (aryl ether ketone)/2,6-bis(4-azidoben-zylidene)-4-methyl-cyclohexanone interpenetrating network. Carbon 2009 47(7) 1857-66. 

Hess, S., Staudt-Bickel, C., and Lichtenthaler, R.N. 2006. Propene/propane separation with copolyimide membranes containing silver ions, 275(1-2) 52-60. 

Reprinted from C. Zhang, Y. Dai, J.R. Johnson, O. Karvan, W.J. Koros, High performance Z1F-8/6FDA-DAM mixed matrix membrane for propylene/propane separations. Journal of Membrane Science 389 (2012) 34—42. 

Mokrushin, V, Assenbaum, D., Paape, N., Gerhard, D., Mokrushina, L., Wasserscheid, R, Arlt, W, Kistenmacher, H., Neuendorf, S. and Goke, V, Ionic liquids for Propene-Propane separation, Chem. Eng. Technol. 33, 63-73 (2010). 

Simple process versions such as in the case of dew point adjustment are not suitable here, since at a tjrpical crude gas pressure of 50 to 100 bar and a single-stage, partial condensation with ensuing separation of the developed fluid, too much propane remains in the gas phase, thus limiting the propane separation from the sales gas. 

Similar to the propane separation, with this simple process the economic ethane yield can only be brought to slightly over 90%. For higher yields, the further development of the GSP will be useful, which is known under the term RSV (Recycle Split Vapoiu) (US patent 5,568,737 of the Elcor Corporation, see Fig. 7.15). 

The concept of using Ag+ in liquid membranes to promote facilitated transport of simple gaseous alkenes, specifically ethylene/ethane separations, began with papers by LaBlanc et al. (6) and Teramoto et al. (7,8). Interest in this process waned somewhat when it was discovered that Ag+ formed explosive side products with acetylene which was present in the feed stocks. Despite this potential problem, researchers at BP America developed a Ag- --based separation process for propene/propane separation (9). 

Carbon membranes are promising candidates for separating light alkenes/alkanes, especially propene/propane separation, because carbon molecrrlar sieve membranes possess excellent propene/propane permselectivities. 

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