Multi-stage flash distillation is used to desalinate seawater so it is fit for h
ID: 1003726 • Letter: M
Question
Multi-stage flash distillation is used to desalinate seawater so it is fit for human consumption. A flash distillation tank is composed of small chambers (called "stages"), each at a lower pressure than the previous stage. Salt water enters the first chamber, some fresh water flash evaporates, condenses, and is removed from the distillation tank. The remaining salt water moves to the next chamber, some fresh water flash evaporates, condenses, and is removed from the distillation tank. The remaining salt water moves to the next chamber, and the process repeats until very salty water is expelled as waste. Brine that is 35,000 ppm salt is desalinated through a 5-stage flash distillation process. The pressure in the stages is such that 8.5% by mass of the water entering the stage evaporates and leaves as fresh water. If the desalination plant wants to produce 1800.0 gallons of drinking water per day, The density of fresh water is 1.000 g/cm3. The density of brine is 1.025 g/cm3.
1- how many gallons of brine must the plant take in per day?
2- What mass of waste brine is expelled in one day?
Explanation / Answer
since it is given that 8.5% of water eliminates as fresh water. this leaves us with the following table:
finally leaving waste is 64.14 kg from 100kg brine.
now with the simple unitary method, 1800 gallons of freshwater will correspond to 4897.09 gallons of total brine entering the system (using volume= mass/density for mass to volume conversion for brine).
and the final mass of water leaving the system would be 12187.2032kg (by first finding the corresponding mass of wastewater for 1800 L of fresh water and then converting it to corresponding gallon value)
entering brine water (kg) leaving freshwater (kg) 100 8.5kg 91.5 7.77 83.73 7.1 76.61 6.5 70.1 5.95Related Questions
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