Each pressure control method is laid out with a figure showing
the method, then a number of sub-sections with descriptive information
and guidelines. The major sections include:
1. Method: Brief one or two line description of the method.
2. Process: type of process for application.
3. Advantages: common reasons to use the method.
4. Disadvantages: common reasons not to use the method.
5. Application: specific application notes.
6. Variants: modifications of the method in common use.
7. Configuration notes: specific design and operating issues to account for in equipment design, installation, operation, or troubleshooting.
8. Operation: how the method works.
9. Warnings: special problems to watch out for.
The figures are simplified to the essence of each method. Most of the configurations shown require other control loops for condensate liquid level control, piping for venting non-condensable gas, water boots on condensate drums, and other equipment. In order to keep the diagrams clear and concise, the figures only information required for discussion of the pressure control problem.
All figures show refluxed towers. Many of the configurations work equally well with conventional fractionation towers and towers that have no reflux. These include columns with reflux provided by pumparounds, internal condensers, or external streams. Many refinery and petrochemical main fractionator columns fall into the no-reflux tower category.
All figures show towers with a liquid product. All vapor rate
> 0 methods (group 1) easily adapt to no-liquid distillate
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