Unit operation Essay Example | Topics and Well Written Essays - 1000 words

Unit operation - Essay Example The feed plate is the 10th tray from the top of the column. The height of the column is 21m above ground level. The minimum number of trays are required at total reflux is 18. The column diameter in the enriching section is 1.005 m and the column diameter in the stripping section is 1.39 m. The below feed is bigger than above with an average column diameter. The biggest diameter was selected of 1.39 m as an estimation of the overall column diameter. The type of tray used in this distillation design was Sieve trays. It singly passes liquid flow across. The tray is 5 mm thick and spaced 0.45 m apart. Every tray contains 5888 active holes with diameter 5 mm in each at a hole pitch of 13.5 mm. The pressure drop across each tray is approximately 1.22 kPa, resulting to a total pressure drop down the column of 36.6 kPa. This is insignificant and the total column is considered to be operating at the atmospheric pressure. The saturated feed enters at 103ËšC while temperatures at the top and bottom of the column are 100.86ËšC and 117.48ËšC, respectively. The total condenser used is a double pipe heat exchanger with a duty of 2417.85 kW while a horizontal thermosyphon partial re-boiler with a duty of 1495.32 kW was chosen. The method used in designing the distillation column is the McCabe-Thiel Method and design method outlined in Coulson and Richardson. An assumption of constant molar overflow (CMO) is made in this design.However; it was not an accurate assumption to make as it results in a significant error in the calculations. A summary of the key findings of the design is as illustrated in the flow diagram on page 2. 6.2. The reflux calculations are limited by the equilibrium data and on the assumption of CMO. The optimum reflux ratio is selected in correspondence to the lowest operating cost of the column. Hence if either of these assumptions are incorrect or the true optimum reflux ratio deviates