Question

Show good examples for calculation of mass balance

Answer 1

Mass balance

Total mass in a system is conserved

General mass balance equation

Input - output + generation - consumption = Accumulation

At steady state

Accumulation = 0

Input - output + generation - consumption = 0

For non reactive species at steady state

generation = consumption = 0

Input = output

Mass balance examples

A distillation column separates the mixture of benzene and toluene in two separate streams of benzene (major product) and toluene (major product) as distillate and bottom products respectively

Mass flow rate of benzene in Feed = 500 kg/h

Mass flow rate of toluene in Feed = 500 kg/h

Mass flow rate of benzene in distillate = 450 kg/h

Mass flow rate of toluene in distillate = m1 kg/h

Mass flow rate of benzene in bottom = 475 kg/h

Mass flow rate of toluene in bottom = m2 kg/h

Benzene balance

Mass flow rate of benzene in Feed = Mass flow rate of benzene in distillate + Mass flow rate of benzene in bottom

500 = 450 + m2

m2 = 50 kg/h

Mass flow rate of toluene in Feed = Mass flow rate of toluene in distillate + Mass flow rate of toluene in bottom

500 = 475 + m1

m1 = 25 kg/h

Now we can check for the mass conservation

Total Input = total output

500 + 500 = 450 + m1 + m2 + 475

1000 = 450 + 25 + 50 + 475

1000 kg/h = 1000 kg/h