Depropanizer distillation

The overhead vapor from a depropanizer distillation column is totally condensed in a water-cooled condenser at 120°F and 227 psig. The vapor is 95 mol % propane and 5 mol % isobutane. Its design flow rate is 25,500 lb yh and average latent heat of vaporization is 125 Btu/lb . 

Depropanization distillation in which lighter components are separated from butanes and higher boiling material also called depropanation. 

Depropanizer distillation tower. This tower is presented on the CD-ROM (either... 

After the simulation file is augmented, the revised simulation is run and the results are sent to Aspen IPE. Note that the ASPEN PLUS and HYSYS.Plant simulators contain menu entries to direct the results to Aspen IPE. For details, the reader is referred to course notes prepared at the University of Pennsylvania (Nathanson and Seider, 2003), which are provided in the file. Aspen IPE Course Notes.pdf, on this CD-ROM. This section presents estimates of equipment sizes and purchase and installation costs using Aspen IPE for two examples involving (1) the depropanizer distillation tower presented on the CD-ROM (either HYSYS —> Separations —> Distillation or ASPEN PLUS Separations Distillation), and (2) the monochlorobenzene (MCB) separation process introduced in Section 4.4, with simulation results using ASPEN PLUS provided on the CD-ROM (ASPEN Principles of Flowsheet Simulation —> Interpretation of Input and Output —> Sample Problem). Just the key specifications and results are presented here. The details of using Aspen IPE for these two examples are presented in the file. Aspen IPE Course Notes.pdf... 

Figure 16.16 Specifications for design of the depropanizer distillation tower...

Table 16.33 Aspen IPE estimates of equipment sizes, purchase costs, and direct materials and labor costs for installation of the depropanizer distillation complex... 

The objective of this work is to simulate the depropanizer distillation column of the NGL plant to compare the costs of the conventional distillation with the cost of a heat pump distillation system. Using the column grand composite curves (CGCC) of the depropanizer distillation column, the depropanizer column is suitable for retrofitting by... 

In a typical case, the tower could be a depropanizer making a separation between propane and isobutane. Purity specifications on the butane product from the base of the tower allow a relatively large concentration of propane. Isobutane level in the recovered propane would be estimated by what separation would occur in a deethanizer which would further fractionate the depropanizer distillate into an... 

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

Example 3.9 A depropanizer normally operates as described in Example 2.4. The column is computer-controlled, using the Jafarey et al. algorithm. The algorithm manipulates reflux flow to control top product purity. Distillate flow rate must remain fixed, but bottom purity is allowed to vary. The top product purity spec is temporarily relaxed from 0.5 mole percant to 0.9 mole percent. What would the controller set the reflux flow at ... 

Description The process includes a fixed-bed alkylation reactor, a fixed-bed transalkylation reactor and a distillation section. Liquid propylene and benzene are premixed and fed to the alkylation reactor (1) where propylene is completely reacted. Separately, recycled polyisopropylbenzene (PIPB) is premixed with benzene and fed to the transalkylation reactor (2) where PIPB reacts to form additional cumene. The transalkylation and alkylation effluents are fed to the distillation section. The distillation section consists of as many as four columns in series. The depropanizer (3) recovers propane overhead as LPG. The benzene column (4) recovers excess benzene for recycle to the reactors. The cumene column (5) recovers cumene product overhead. The PIPB column (6) recovers PIPB overhead for recycle to the transalkylation reactor. 

Oxygenated compounds and unconverted ethylbenzene, collected at the bottom of the second depropanizer, are first distilled under vacuum to recover the propylene oxide and lighter components at the top. This effluent is nd in succession of the acetaldehyde and propionaldehyde it contains by simple distillation, and then of methyl formate by extractive dbtiUation with ethylbenzene. The latter b then purified and recycled. The operation b terminated by a final column whidi produces propylene oxide to commercial specifications. 

A depropanizer is a distillation operation encountered in almost all oil refineries. Our task here is to design a column to separate 1000 mol/s of a four component mixture containing 300 mol/s n-propane and 500 mol/s -butane so that there is no more than 3.5 mol/s of n-propane present in the bottom product and no more than 3.5 mol/s of n-butane is... 

Depropanizer /-Butane splitter n-Butane splitter Figure 5.5. Simplistic distillation train. 

After filtration of the reactor outstream. the propane is extracted in a depropanizer and partly recycled. Excess benzene and cumene, which is obtained in a purity of 99.9 per cent weight, are recovered by distillation in columns with about 30 trays each. The cumene contains about 1200 ppm of impurities, usually consisting of 0.02 per cent weight ethylbenzene. 0.05 per cent weight n-propvlbenzene, and 0.05 per cent weight butyl benzene. The yield is 96 to 97 molar per cent in relation to benzene, and 91 to 92 per cent in relation to propylene. The fractionation section of the unit is of carbon steel In some cases, part of the reactor and other equipment may be of stainless steeL... 

The feed to a depropanizer is 66% vaporized at the column inlet. The feed composition and average relative volatilities are given in the table below. It is requited that 98% of the propane in the feed is recovered in the distillate, and 99% of the pentane is to be recovered in the bottoms product. Calculate the minimum reflux ratio for this case using Underwood s method. 

The deethanizer bottoms and condensate stripper bottoms from the charge compression system are depropanized (12). Methylacetylene and propadiene are hydrogenated in the depropanizer using CDHydro catalytic distillation hydrogenation technology. The depropanizer bottoms... 

In multicomponent separations, the sensitivity of temperature to the key components is important. Figure 18.2a and b shows composition and temperature profiles for a depropanizer separating propane (C3) and lighter components from butane (C4) and heavier components. The temperature is sensitive to the composition of the keys between tray 3 and tray 13. Below tray 3 and above tray 13 the temperature is more sensitive to the concentration of nonkeys than to the concentration of the keys. Trays 8 to 10 show some tendency toward retrograde distillation (recognized by the maximum in the C4 concentration curve) and are best avoided. Moczek et al. (287) provide a detailed demonstration of the anomaly in temperature response in the retrograde distillation region. This leaves trays 3 to 7 and trays 11 to 13 as those suitable for temperatime control. 

In the separation train, the gas stream is partially liquefied before entering the demethanizer at 320 bar. The overhead vapor, containing methane and hydrogen, is sent to a membrane separator in which these products are separated. The pressure of the bottoms product is reduced to 270 bar and fed to the deethanizer. In this column, the ethylene and ethane are removed in the distillate, whose pressure is reduced to 160 bar before the species are separated in the C-2 splitter. The bottoms product from the deethanizer, containing propylene, propane, and the heavier species, is throttled to 190 bar, mixed with the bottoms product from the condensate splitter, and fed to the depropanizer. The overhead product of the depropanizer is a mixture of propane and propylene and the bottoms product is throttled to 50 bar and sent to the debutanizer. In this column, the butylenes and butadiene are separated from the SCN. 

A depropanizer example is provided to illustrate the use of Aspen IPE. The depropanizer is a distillation tower to recover propane and lighter species from a normal-paraffins stream, as shown in Figure 1. The simulation flowsheet and selected results are shown in Appendix I and in the multimedia tutorial on the CD-ROM that contains these course notes ASPEN Tutorials —> Separation Principles -> Flash and Distillation). Also, a copy of the file, RADFRAC.bkp, is provided on the CD-ROM. 

For the depropanizer, all items are mapped and sized in sequence, since the Size ICARUS Project Components button is checked. When this button is not checked, only the mapping step is completed. Also, when there are multiple process units of a certain type, it may be preferable to map each process unit independently. For example, if two distillation towers differ in tray efficiency, it is necessary to map them separately and change the tray efficiency under Design Criteria before each tower is mapped. In this case, with just one tower, it is simplest to press the Map all Items button under Source. Under Basis, the Default and Simulator Data button should be selected, as shown. After pressing OK, the Project Component Map Preview dialog box is produced ... 

For the depropanizer column, most of the default values are acceptable. Because a single distillation system would be installed normally on an existing plant site, using utilities provided by the site, the Project Type would not be selected as Grass Roots/Clear field. This Project Type would cause new items, already provided at the site, to be included in the design and cost estimates. Typically, these include a new control system and electrical substation components. 

Another very large potential application of membranes in ethylene plants is replacing the C2 and C3 splitters. An example of a possible process design is shown in Fig. 7.15. In this example, a two-step membrane system equipped with propylene-permeable membranes is used to split a 50/50 propylene/propane overhead stream from a depropanizer column into a 90% propylene stream and a 90% propane stream. Both streams could then be sent to distillation units for polishing, but the size of columns required would be much reduced. For this design to be feasible, membranes with an olefin/paraffin selectivity of 5 to 10 are required. Many other designs that combine membranes and distillation columns to achieve good separation are possible [23]. 

Process Studied. The numerical example used in this section with an aU-vapor distillate stream is a depropanizer with a feed that contains a small amount of ethane, but is mostly propane, isobutane, and -butane. Two cases are considered. The first has a feed composition that is 2mol% ethane and 40mol% propane, so the distillate flow rate is large and the RR is moderate (RR = 2.6). In the second case, the propane in the feed is only 4 mol% (with 0.02 mol% ethane), which gives a small vapor distillate flow rate and a large reflux ratio (RR = 20). Table 8.1 gives design parameters for the two cases. The Chao-Seader physical properties are used. 

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