Aspen Plus mass flow rate

The equipment requirements were determined from the ASPEN-Plus model. The quantity and size of each piece of equipment was determined on the basis of the mass flow rate through the equipment. From the thickness calculations, it was found that three reactors were optimal to accommodate a mass flow rate of 83,333 dry kg/h. It was also found that the solids concentration of the pretreated material made it necessary to use more than one Pneumapress filter. 

To get started, do external mass balances and calculate accurate values for the two bottoms flow rates assuming that the water and MEK products are both pure. Specify the bottoms flow rate of column 1 = 60, but do NOT specify bottoms in column 2. In column 2 start with D = 20 and increase D in steps, 30, 40, 50, 60, 70, and so forth without reinitializing. If you don t step up. Aspen Plus will have errors. 

The resulting Makeup flow rate will be extremely small since losses of solvent are small (after all, no one wants to drink ethylene glycol with their alcohol or their water). If you immediately use this value of solvent makeup as a feed to the system. Aspen Plus will not converge. Start with the value you were using previously and rapidly decrease it (say by factors of roughly 5 or 10). Until the solvent makeup stream is at the desired value for the external mass balance, the extra ethylene glycol will exit with the distillate (water product) from column 2. This occurs because Bottoms flow rate in column 2 is specified and the only place for the extra ethylene glycol to go is with the distillate from column 2. 

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