Subtopic: Concentration and drying of liquid foods – evaporators, tray, drum and spray dryers
Question Statement:
In a triple effect feed forward evaporator, pineapple juice is entering at the rate of 6.3 kg s⁻¹ and leaving the last effect as 50% concentrate. The system is using saturated steam of 2.48 kg s⁻¹ at 121.1 ºC. If vapour transferred from the first to the second effect, second to third effect and third to ambient are 5675, 6053 and 6416 kg h⁻¹, respectively, the steam economy of the evaporator is __________. [round off to two decimal places]
Official Answer Key:
2.00 to 2.04
Step-by-Step Solution & Explanation
• Total vapour produced (sum of vapour generated across all three effects) = 5675+6053+6416 = 18,144 kg/h
• Steam consumption = 2.48 kg/s × 3600 = 8928 kg/h
• Steam economy = Total vapour produced/Steam consumed = 18144/8928 = 2.03
Computed value: 2.03 (within official range 2.00–2.04)
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