Flowcharts column distillation

In professionally drawn flowcharts, special sj mbols are used to denote different types of process units such as distillation columns and heat exchangers. We will not generally use these symbols in this text, since our main purpose is to show you how to perfonn material and energy balance calculations. Simple boxes are perfectly adequate to represent process units on the flowcharts you draw for these calculations. 

The following flowchart shows a distillation column with two feed streams and three product streams ... 

The fresh feed to the process flows at a rate of60,000 kg/h and contains 25.0 mole% isobutane. 25.0% butylene, and 50.0% -buiane. which is chemically inert in this process. The fresh feed combines with three separate recycle streams, as shown in the flowchart, and the combined stream enters the reactor. Essentially all of the butylene fed to the reactor is consumed. A portion of the reactor effluent is recycled to the reactor inlet and the remainder passes to a decanter, in which the aqueous (sulfuric acid) and hydrocarbon phases are allowed to separate. ITie acid is recycled to the reactor, and the hydrocarbons pass to a distillation column. ITie overhead from the column contains iso-octane and n-butane, and the bottoms product, which is recycled to the reactor, contains only isobutane. The stream entering the reactor contains 200 moles of isobutane per mole of butylene, and 2 kg of 91 wt% H2S04(aq) per kg of hydrocarbon. ITie stream obtained by combining the fresh feed and isobutane recycle contains 5.0 moles of isobutane per mole of butylene. 

A mixture containing 65.0 mole% acetone (Ac) and the balance acetic acid (AA) is separated in a continuous distillation column at 1 atm. A flowchart for the operation is as follows ... 

The flowchart shown here depicts a multi-unit separation process. Three liquid streams are mixed adiabatically the product stream is pumped through a heater to a distillation column, and the overhead product from the column is partially condensed to yield liquid and vapor products. Using the blocks MIX (mix two streams to form a third), PUMP, HEAT, DISTILL, and CNOS, construct a block diagram for the simulation of this process. 

Figure 4-30. Conputer flowchart for sinple distillation column...

Column 2 is a sinple distillation that can be designed by the methods discussed in Chapter 4. Column 1 is considerably more cortplex, but the bubble-point matrix method discussed in Chapter 6 can often be adapted. Since the system is nonideal and K values depend on the solvent concentration, a concentration loop is required in the flowchart shown in Figure 6-1. Fortunately, a good first guess of solvent concentrations can be made. Solvent concentration will be almost constant in the middle section and also in the bottom section except for the reboiler. In the top section of the column, the solvent concentration will very rapidly decrease to zero. These solvent concentrations will be relatively unaffected by the tenperatures and flow rates. The K values can be calculated from Eq. (2-35) with the activity coefficients determined from the appropriate VLE correlation. Process simulators are the easiest way to do these calculations (see appendix to Chapter 81. 

When you draw the flowchart, put a pump (select under pressure changers ) on the distillate line going from column 1 that becomes the feed to column 2. The resulting flowchart should be similar to Figure 8-Al. Pump efficiency = 1.0, and Outlet pressure = 100 psia. 

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