Question 4 in:

A gas from a processing facility has residues of ammonia in it. which needs to be removed by absorption. Absorption is to be done in a counter-current sieve tray tower using pure water as the absorbent. The process gas enters with a flow-rate of 250kgmole/h with an ammonia content of 10%. The column is to remove 95% of the ammonia. Equilibrium data for the ammoniawater system is given in table 1 . The process is to be operated at 1 bar of pressure and 25C. Assume that ammonia is the only species absorbing. Table 1: equilibrium data for the ammonia-water system. 1) Determine the minimum L/V Ratio The column is to operate as 1.7 times the minimum L'V'-ratio. 2) Determine the actual operating conditions and flow rates in and out of the column. 3) Using an X,Y-plot determine the number of trays in the column. Based on literature the sieve trays used are found to only have an efficiency of 48%. 4) Determine actual number of trays in the column as well as tower height and diameter using a flooding factor of 0.8 , foaming factor of 0.75 , tray spacing of 18, surface tension of 72 dyne/cm and an active to hole area ratio of the tray of 0.2 . 5) Design your tower in a process simulator and compare the results. Do you see any major differences and if so why