Sulfur, oxygen, and nitrogen molar balances

The next step in calculating a heatup path point is to develop steady state molar S, O and N balances for Fig. 11.3 s feed and level L gases. 

Each mole of SO2 and SO3 contains 1 mole of S, so this expands to  

The steady state molar oxygen balance for the segment is  

Each mole of SO2 and O2 contains 2 moles of O while each mole of SO3 contains 3 moles of O, so this equation expands to  

The segment s steady state molar nitrogen balance is  

The steady-state molar oxygen balance for the segment is kg mol O in = kg mol O out 

The segment s steady-state molar nitrogen balance is kg mol N in = kg mol N out. 

Each mole of N2 contains 2 mol of N, so this balance becomes 2 kg mol N2 in = 2 kg mol N2 out or, subtracting 2 kg mol N2in from both sides  

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