Propane-propylene splitter

Sizing of isopentane/pentane and propylene/propane splitters. 

Most volatile mixtures have a relative volatility that varies inversely with column pressure. Therefore, their separation requires less energy at lower pressure, and savings in the range of 20 to 40 percent have been achieved. Column pressure can be minimized by floating on the condenser, i.e., by operating the condenser with minimal or no restrictions. In some columns, such as the propylene-propane splitter, pressure can be left uncontrolled. Where it cannot, the set point of the... 

As an example of an ATV test, consider its application to a dynamic simulator of a C3 (propylene/propane) splitter. Figure 15.48 shows an ATV test and an open-loop test on the same time scale for the bottom product composition control loop. Note that the four cycles of the ATV test required 6 to 8 hr, while the open-loop test required in excess of 60 hr. The ATV results were used with TL settings, and the results for three different tuning factors are shown in Figure 15.49. 

The slow speed of response of schemes 16.46 and d is particularly troublesome in trayed superfractionators. The author has experienced situations where the slow and sluggish response of scheme 16.4ethylene-ethane splitter and a propylene-propane splitter. In the ethylene-ethane splitter, response was immensely improved when the control scheme was changed to scheme 16.4a, even though top product purity was far more important than bottom product purity. In the propylene-propane splitter, the energy balance control method (Fig. 16.7) was a significant improvement in performance compared to scheme 16.4d again, the top product was far more important. 

Due to the above limitations, an energy balance control scheme such as scheme 16.7 is not recommended, but some situations exist where this scheme can offer better product composition control than many other alternatives. Superfractionators with a reflux to distillate ratio of 10 to 1 or more are one example. Here, distillate flow may be too small to satisfactorily control either accumulator level or column temperature. The author has experienced a satisfactory operation of scheme 16.7 in a propylene-propane splitter, with intermittent operator intervention to ac ust the material balance. The cycles in reflux and reboil (see above) could be tolerated, as the column was not operating close to its limits. In this column, scheme 16.7 gave tighter composition control than scheme 16.4d. 

It was concluded from the table that the bottom half of the tower had to be washed. The unit was shut down, and the propylene-propane splitter opened for inspection. The feed tray was covered with a thick deposit. Lower trays were also badly plugged. A component analysis of the deposit indicated it to be largely potassium (K). 

What had happened The propylene-propane splitter had formerly run for many years without difficulty. After the unit was revamped, the sieve decks had plugged. 

We consider a binary mixture with constant relative volatility a = 1.12 to be separated in a distillation column with 110 theoretical stages and the feed entering at stage 39 (counted from the bottom with the reboiler as stage 1). Nominally, the feed contains 65 mole% of light component (zp = 0.65) and is saturated liquid (qp = 1.0). This represents a propylene-propane splitter where propylene (light component) is taken overhead as a final product with at least 99.5% purity (xp > 0.995), whereas unreacted propane (heavy component) is recycled to the... 

I had been hired to review the design for a new 12,000 BSD propane-propylene splitter for a chemical plant in Convent, Louisiana. The tower was intended to be a replacement for an existing 10,000 BSD propylene-propane splitter. The incremental capacity of2000 BSD would economically justify the 3,000,000 investment for the new splitter. 

The advantages of coupling a permeation membrane on a distillation-based propylene/propane fractionation were first evaluated in a study carried out at University of Colorado, Boulder, and sponsored by BP. Various membrane/ distillation coupling scenarios (membrane unit located on the top stream or on the bottom stream or on the side stream of the column, all cases with a recirculation of the propylene-enriched permeate inside the column) were compared with a reference case based on a propylene/propane splitter column operated with 152 theoretical stages, a reflux ratio equal to 24.1 and a feed... 

It should be noticed here that no real overall cost analysis of the impact of implementation of a permeation unit on a propylene/propane splitter column was carried out in this paper. Therefore, it was not demonstrated if the extra operating and capital costs due to the membrane and compressor installation and operation were over-balanced by the reduction in the operating costs of the distillation column. 

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