QUESTION $2$: PUMP SELECTION AND SIZING

$25$ MARKS

Crude dichlorobenzene is pumped from a storage tank to a distillation column. The tank is blanketed with nitrogen and the pressure above the liquid surface is held constant at $0\mathrm{.}1$ bar gauge pressure. The minimum depth of liquid in the tank is $1m.$ The distillation column operates at a pressure of $500mmHg(500mm$ of mercury, absolute$).$ The feed point to the column is $12m$ above the base of the tank. The tank and column are connected by a $50mm$ internal diameter commercial steel pipe, $200m$ long. The pipe run from the tank to the column contains the following valves and fittings: $20$ standard elbows; two gate valves to isolate the pump $($operated fully open$)$; an orifice plate and a flowcontrol valve. If the maximum flow$-$rate required is $20,000k\frac{g}{h},$ calculate the pump motor rating $($power$)$ needed. Take the pump efficiency as $70$ per cent and allow for a pressure drop of $0\mathrm{.}5$ bar across the control valve and a loss of $10$ velocity heads across the orifice. Density of the dichlorobenzene $1300k\frac{g}{m^3},$ viscosity $1\mathrm{.}4cp.$

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