Question

Evaporator economy is defined as:

• A. Kg of steam used per kg of solvent evaporated
• B. Kg of solvent evaporated per kg of steam used
• C. Heat transferred per unit area
• D. Rate of heat loss to surroundings

Hint:

Logic Tip: Think of it like a car's fuel economy (Miles per Gallon). You want the most distance (solvent evaporated) for the least amount of fuel (steam used). Therefore, it must be Solvent per Steam, not the other way around.

Answer 1

The Correct Option is B

Concept:
In chemical engineering, an evaporator concentrates a solution by boiling off the solvent (usually water). This boiling requires heat, which is typically provided by condensing hot steam. "Economy" is the standard metric for evaluating how efficiently this equipment uses that steam.

Step 1: In engineering, efficiency or "economy" is always a ratio of "what you want to get" divided by "what you have to pay to get it."

Step 2: The entire purpose of the evaporator is to remove solvent from the mixture. Therefore, the "output" is the mass of the solvent successfully evaporated.

Step 3: The energy driving the process comes from the plant's steam supply. Therefore, the "input" is the mass of live steam consumed by the heating coils.

Step 4: Evaporator Economy = (Useful Output) (Required Input).

Step 5: This ratio gives the standard definition: the kilograms of solvent evaporated divided by the kilograms of steam used to cause that evaporation.