Method: Vary blanketing vapor above drum.
Process: Net vapor rate positive or zero.
Advantages: Simple, fast response.
Disadvantages: Net consumption of pressurizing gas. Two control valves. May have tuning problems.
Application: Pressure towers.
Variants: Adding make-up gas upstream of the condenser may reduce gas rate required due to partial vapor blanketing of the condenser. However, response time will be slightly slower.
Configuration notes: Pressurizing gas must be compatible with the process. Some pressurizing gas may enter distillate product and reflux. Equalizing line not required.
Operation: When pressure drops below desired set point, vapor added to receiver. When pressure rises above desired set point, vapor product line opened.
Return to Table of Methods
Return to consolidated paper list