FE Chemical Practice Question Solution included after investigation
CASE E-062 · FE

The Evaporator That Removed 750 kg/h of Water

The feed was 1000 kg/h at 10 wt% solids. Concentrating to 40 wt% left only 250 kg/h liquid product.

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Case E-062 engineering failure visual
HOW THIS WORKS

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Follow the investigation process used in the field — in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

2

Commit

Choose your hypothesis.

3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

Sign Off

See the full debrief and key takeaways.

Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

An evaporator receives 1000 kg/h of solution containing 10 wt% nonvolatile solids. Water is evaporated, and the liquid product contains 40 wt% solids. Assume no solids leave with the vapor. A quick estimate says the product flow is 400 kg/h because the product is 40% solids. Determine the actual liquid-product and vapor flow rates.

Material Energy Balances Chemical Design Verification Root Cause Analysis Safe Correction
E-062
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
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CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What failed

Product composition was mistaken for a feed-flow fraction.

What was missed

Only 100 kg/h of nonvolatile solids enter.

Corrected model

Use the solids component balance, then the overall balance.

QUICK ANSWER

The feed contains 100 kg/h nonvolatile solids. At 40 wt% solids, product flow is 100/0.40=250 kg/h. The remaining 750 kg/h leaves as water vapor.

ENGINEERING TAKEAWAY

For a nonvolatile solute, balance the solute first; it fixes the concentrated-product flow.

CASE QUESTIONS

Questions this case should settle.

How do you solve an evaporator material balance with nonvolatile solids?

Balance the solids first, then use the overall mass balance for the vapor flow.

How much water is evaporated in this case?

750 kg/h.

NEXT FE PRACTICE QUESTION

The Heater That Needed 418 kW, Not 209

Material Energy Balances · 5–10 min

Continue Practice →
WHAT YOU’LL LEARN

Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?

Basic subject familiarity helps, but every case is designed to teach through the investigation itself.

How long does a case take?

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Are the cases aligned with engineering exams?

Each case is mapped to a verified exam, subject, topic, and misconception before publication.

What happens after I complete a case?

The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.