Water balance with transient operation

When water is supplied in excess, the reaction is second order with respect to the propylene oxide concentration and zero order with respect to the water concentration. Its rate constant exhibits an Arrhenius dependence on temperature, with Aq = 3.294 X 10 mV(kmol-hr) and E = 1.556 X 10 kJ/kmol. Furthermore, it is customary to dilute the PO feed with methanol (MeOH), while the H2SO4 catalyst enters the reactor with the feed. Operating conditions are sought for carrying out this liquid-phase reaction in a 47-ft CSTR, with the liquid holdup at 85% of its total volume (1.135 m ). The liquid feeds are fed at 23.9 C, with one consisting of 18.712 kmol/hr of PO and 32.73 fanol/hrof MeOH. The water feed rate is from 160 to 500 kmol/hr (2.84-8.88 m /hr), selected to moderate the reactor temperature. To reduce the risk of vaporization, the reactor is operated at a pressure of 3 bar. Under these conditions, the transients for the PO concentration, Cpo (kmol/m ), and temperature, T (°C), are determined by solving the following species and enthalpy balances ... 

Many possibilities exist for meeting the basic functional requirement here. The required motive power could be dc, gravity, stored (static) energy in the form of pressurised gas or a combination of them. The required water could be stored within the containment, on the containment, outside the containment or a combination of them. Different LOCA scenarios require different amounts of water at different times. Sufficient inventory with sufficient delivery capacity throughout the transient must be maintained. In addition, it is very desirable to deliver the right amount of water, at the right time without operator involvement. The true trade-off here is then between the ac powered, outside containment delivery and cooling system, and one that simply relies on total pressure balances and natural circulation. 

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