separation trays, number of reactive trays, and column pressure. The temperatures at the top and bottom of different sections are also given in this table.

Figure 3.13 displays the composition profile of the optimum design for the base case (Keq)366 = 2. The highest composition of reactant A is at the bottom of the reactive zone where it is fed. Reactant B has its highest composition at the top of the reactive zone, which is also its feed tray. The composition of A decreases up through the reactive zone, but the composition of product C increases. The reverse occurs for reactant B and product D through the reactive zone. The rest of the column operates as a separation unit. Thus, the composition of heavy product D increases down through the stripping section, and the composition of light product C increases up through the rectifying section.

Figure 3.14 shows the temperature profiles of the optimum designs for three different kinetic cases: (Keq)366 = 1,2, and 5. The temperature profiles of each case are similar with higher temperatures for higher values of (Keq)366 because of the higher optimum pressures. There are fairly significant temperature breaks around tray 4 for all cases, and these tray temperatures can be used in control schemes to infer bottoms purity. A similar break occurs at different tray numbers near the top of the column for each case. These could be used to infer distillate purity. For all kinetic cases, the temperatures show little change in the reactive zone.

Figure 3.15 illustrates the effect of conversion on the TAC for different pressures. The conversion is increased to 99%, and the optimal results at each pressure are given for base kinetic case (Keq)366 = 2. To achieve the required purity, the optimum number of separation stages is NS = NR = 7 in this instance, which is 2 more than in the 95% conversion system. The optimum number of reactive stages is 13, which is 4 more than the base case.

Figure 3.14 Temperature profiles.

Was this article helpful?

0 0

Post a comment