Steam is the most expensive factor in evaporators operation. From this, follows that the economy of such an equipment has to be estimated or measured somehow.
For short, the economy of an evaporator, of single stage or multiple effect, is just defined as,
Eq. (01)In single stage evaporators the economy will usually be smaller than 1 while in multiple effect evaporators, this parameter could be greater than 1. This is because for every effect the heat in the solvent vapor is used as much as possible. On the other hand, single stage evaporators are easy to use but with low economy while multiple effect evaporators are difficult to used but of higher economy.
Notice, that the economy is given in terms of the mass but if mass flow rates of solvent vapor and steam are the only available data, these can be used without any issue.
Evaporator capacity
This is defined as the mass flow rate of solvent vapor extracted from the solution, fiven in mass/hour units.
Eq. (02)Of course, in a multiple effect evaporator all solvent vapor streams would contribute.
Steam consumption
The total steam consumption can be easily calculated from division of the evaporator capacity over its economy,
Eq. (03)In this case, the steam consumption is given as mass flow rate.
Other stuff of interest
- Understanding the law of Boyle
- Measuring atmospheric pressure
- Some examples of temperature instruments
- Minor losses - Formulas
- What is a process variable?
- What are the most important process variables?
- Time dependence of process variables
- A list of process variables
- Composition variables for mixtures
Ildebrando.
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