BDIST-SimOpt has been successfully used for several years in the operation of batch distillation columns. For a given sequence of fractions, the simulation model predicts the duration of each fraction based on the feed composition and column operating conditions. The cut durations comprise the set points for the batch control system. This eliminates costly off-line analyses, increases reliability, improves yield and increases profitability. BDIST-SimOpt is so simple to use that operators run it before distilling each batch through a column.
The problem statements of some of the BDIST-SimOpt applications are given below.
Tetrahydrofuran (THF) is separated from a highly non-ideal mixture of process effluents using a batch distillation column. Determine the distillate quantities as the reflux ratio is changed during the entire operation. If a batch contains more than 1.5% Methylene Chloride, use a reflux ratio of 20 until Methylene Chloride in the distillate drops below 1.5%. Use a reflux ratio of 13 until the distillate composition reaches 85% THF by volume and water is less than 0.1% by weight. Change the reflux ratio to 6 until the distillate composition reaches 95% THF by volume. Use a reflux ratio of 1.2 until the distillation composition drops below 96% THF by volume. Stop the distillation whenever the amount in the reboiler drops to 300 gallons. If the condenser composition exceeds 94% THF, empty the condenser into the specified accumulator. Present the results with compositions expressed in volume fractions, amounts in gallons, and temperatures in degrees Centigrade. All volumes are to be measured at 20 degrees Centigrade at one atmospheric pressure.
Determine the operation policy for a 21-plate batch distillation column to maximize the profit on separating Tetrahydrofuran (THF) from a mixture containing Methylene Chloride and six other components. The profit on 97% THF by volume is $10.50 per gallon, while the profit on 99% THF by volume is $14.50 per gallon. Due to environmental considerations, product containing more than 1.5% Methylene Chloride must be burnt, which incurs a loss of $0.60 per gallon. The operation shall take no more than 20 hours. The reflux profile desired for each fraction is selected from the following choices: constant, linear, and exponential.