Question

In the process SKetched in Figure P6.3.18, Na2c03 Is produced by the reaction NaaS + CaCO3 ? Na2CO3 + Cas. The reaction is 90% complete on one pass through the reactor, and the amount of CaCO3 entering the reactor is 50% in excess of that needed. Calculate on the basis of 1000 lb/hr of fresh feed, all streams, molar and mass compositions. Assign a letter for each stream. Write the results in a table. Fresh Feed 1000 lb/hr 40% Na2S 60% H2O Pure Na S H2O Reactor 30% CaCO3 80% Na CO 70% H2O 1923 Ib/hr 20% H2O 30% CaCO3 ? 20% CaS soln. soln. CaCOs soln. 60 lb/hr CaCO Total:

Answer 1

caco_3 flow rate = 30% times (1923) = 576.9 lb/hr = 576.9 times 453.592/100 = 2616.772 mol/hr with 90% efficiency so we need 0.9 times 2616.772 mol/hr of Na_2S = 2355.1 mol/hr to react with caco_3 2355.1 mol/hr of Na_2S = 2355.1 times (2 times 23 + 32)/453.592 = 405 lb/hr Incoming Na_2S = 45% (1000 lb/hr) = 450 lb/hr Therefore, recycled Na_2S = 450 - 405 = 45 lb/hr