Consider the DME Tower, T-201, in the DME process. Simulate this unit using a shortcut model with different liquid-state activity-coefficient models to determine the required number of stages for the reflux ratio and the recoveries. Include no corrections for heat of mixing. Then perform a rigorous column simulation to check the distillate purity. Compare the results.

The base case uses the UNIFAC model with vaporphase fugacity correction. The specifications are as follows:

• Column pressures: top, 10.3 bar; bottom, 10.5 bar
• Key components: light, DME; heavy, methanol
• Light key recovery in distillate: 98.93%
• Heavy key recovery in bottoms: 99.08%
• Reflux ratio: 0.3631
• 70% plate efficiency

An initial CHEMCAD simulation confirms the value given in Appendix B of 22 actual stages.