Scaling a Material Balance

[@LearnChemE]

This screencast has been reviewed by faculty from other academic institutions.

[@baseer8000]

Can be this be done on a Process flow diagram ?? like if we calculate the whole process to give a product of around 70 tons /years ,but we require to know the values regarding 55,000 tons /year ??

[@LearnChemE]

In the video the value of 66.7 was simplified too early and really is 66.666 repeating. Hence why she wrote 6667 and 5333. Important to carry out terms to the end before simplifying.

[@binn12t82]

how did we solve for the mass flow rate of the feed mf?

[@LearnChemE]

+binn12 To solve for the mass flow rate of the feed, we can use two material balances. First the overall balance: m_f = 5 + 15 + m_s, then either a salt or a water balance - here I'll do salt: 0.35m_f = 15 + 0.25m_s, substituting the first equation into the second gives us 0.35(20 + m_s) = 15 + 0.25m_s, further calculations: 7 + 0.35m_s = 15 + 0.25m_s, 0.1m_s = 8 m_s = 80 kg/h; put that back into the overall balance: m_f = 5 + 15 + 80 = 100 kg/h.

[@Chimera47Firefly]

@4:30 100*66.7 = 6670, NOT 6667 80*66.7 = 5336, NOT 5333