Distillation calculations by computer

If the use of electronic computers is advantageous on the laboratory and pilot-plant scale it is a must in industrial distillation with its complex control problems. Nowadays the whole separating process in a multistage plant is controlled by a process computer. A comparison of the essential criteria of the various process computers used for laboratory automation is given by Blatt and Meissner [259]. 

We distinguish between digitu.1 [246] and analog computers [247] and the combination of the two in hybrid computational systems [248]. The digital computer supplies the data in tables of figures whereas the analog machine represents the results as time-dependent voltages which may be recorded in various forms. It would lead us too far to go into details here the reader is referred to books on the subject [248, 2491. 

The calculation of batch distUlations of multicomponent mixtures is particularly difficult. Rose [251b] developed a computer programme which simulates the dynamic behaviour of discontinuous distillation processes. 

Sealey [252] used an English Electric KDF 7 comjiuter to optimize the total efficiency of an Oldershaw laboratory plate column (cf. Fig. 268) with a diameter of 31.8 mm and 12 and 10 actual plates in the lower and upper sections, respectively. He analyzed 280 cases using methyl cyclohexane-toluene as test mixture. The optimum plate number was defined as the one which minimizes the errors. These sources of error were investigated  

The mathematical model of a semitechnical rectification column with stationary 0])eration was elaborated and experimentally tested by GroBhennig [267]. The tests were made in an NVV 310 bubble-cap column with 35 plates using the system chloroform-carbon tetrachloride. A comparison showed that even the simplified version of the model gave satisfactory agreement. 

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