Hexamethylene tetraamnie, N4(CH2)6, is to be produced in a well-stirred semibatch reactor by adding aqueous ammonia solution at a constant rate of 10 liters/min. to an initial charge of formalin solution [formaldehyde (HCHO) in water]:

6HCHO + 4NH3 → N4(CH2)6 + 6H2O

The reaction is instantaneous, irreversible, and exothermic. The initial charge of formalin solution is 2000 liters with a formaldehyde (A) concentration, CAi, of 15.0 gmol/liter. The concentration of ammonia (B) in the solution is CB = 15.0 gmol/liter.

Required:
Calculate the time required for complete consumption of formaldehyde.