Mohsen darabi - Department of chemical engineering ,university azad shahrood,branch shahrood,shahrood,iran
reza naeimi - process engineer oil refinery of abadan
mostafa montazeri - Department of chemical engineering ,university azad shahrood,branch shahrood,shahrood,iran
hamed sohrabzadi - Department of chemical engineering ,university azad shahrood,branch shahrood,shahrood,iran

The design of a distillation column involves many parameters: product compositions, productflow rates, operating pressure, total number of trays, feed-tray location, reflux ratio, reboiler heat input, condenser heat removal, column diameter, and column height. Not all of these variables are independent, so a degrees of freedom analysis is useful in pinning down exactly how many independent variables can (andmust) be specified to completely define the system. A rigorous mathematical degrees of freedom analysis involves counting the number of variables in the system and subtracting the number of equations that describe the system. For a multicomponent, multistage column, this can involve hundreds, if not thousands, of variables and equations. Any error in counting is grossly amplified because we are taking the difference between two very large numbers. A simple intuitive approach is used below. The normal situation in distillation design is that the feed conditions are given: flow rate F (mol/h), composition zj (mole fraction component j, temperature TF, and pressure PF. The desired compositions of the product streams are also typically known. We consider a twoproduct column, so that the normal specifications are to set the heavy-key impurity in the distillate xD,HK, and the light-key impurity in the bottoms xB,LK. These specifications apply in binary and multicomponent systems.

Simulation, designing, distillation, aspen plus