Single-Column Process

In a simple single-column process, although the oxygen purity is high, the nitrogen effluent stream is impure. The equilibrium vapor... 

The single-column process (Figure 1) is similar to that of Jones et al. (1). This process is useful for bulk separations. It produces a high pressure product enriched in light components. Local equilibrium models of this process have been described by Turnock and Kadlec (2), Flores Fernandez and Kenney (3), and Hill (4). Various approaches were used including direct numerical solution of partial differential equations, use of a cell model, and use of the method of characteristics. Flores Fernandez and Kenney s work was reported to employ a cell model but no details were given. Equilibrium models predict... 

Two-Column Process The heatless adsorption process (Figure 2) has two columns Each column undergoes a four-step cycle. Three steps involve the same sequence as the single column process pressurization with feed, feed at high pres-... 

Modeling of this process proceeds in the same way as for the single-column process described above except for introduction of a purge step. The process is started with one column equilibrated with feed at high pressure and the other at low pressure Eqs (16), (20) and (22) are used as before with renumbering of cells and mole fractions at appropriate points in the cycle, but the purge step is inserted into the sequence at the appropriate point ... 

An example of the effect of pressure on the performance of the single column process for the methane-helium separation is shown in Table 1. Using Figure 4(b) and 4(d), the cuts corresponding to 80 percent recovery of helium were determined as a function of yF and Pr L Then the enrichments and in... 

Effect of Pressure on Single-Column Process for Helium-Methane Separation... 

The curves for H = 0 represent the performance of the single-column process. It is apparent that the single-column process is superior at large product cuts in terms of both enrichment and recovery. For small cuts, the two-column process is superior. 

The equations for a local equilibrium cell model of pressure swing adsorption processes with linear isotherms have been derived. These equations may be used to describe any PSA cycle composed of pressurization and blowdown steps and steps with flow at constant pressure. The use of the equations was illustrated by obtaining solutions for a single-column recovery process and a two-column recovery and purification process. The single-column process was superior in enrichment and recovery of the light component at large product cuts. The two-column process was superior at small cuts ... 

For the large throughputs that are common today, the double-column process is preferred over the single-column process, since it does require smaller columns with smaller column diameters, which makes the transportation... 

In the example discussed in this chapter (Sections 10.3-10.6), we restrict ourselves to the single-column process for the simple reason that the analysis is straightforward and illustrates the concepts best. In addition, data for this analysis are readily available [6]. 

Another way to improve the single-column process is to use a membrane to split the feed into two different feed streams (see Figure 10.15). Since the membrane does part of the separation, the column has to do less work to... 

The initial flowsheet has some default controllers already installed. In this simple, single-column process there is only one default controller, the pressure controller. It is... 

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