Question

Ferric hydroxide is to be filtered at constant pressure in a Plate and Frame press 3 ft² with 1 inch frame thickness. After 6.5 hours of operation, the press is full and 4.5 ft³ of filtrate per ft² of area has been collected. It is desired to wash the cake with 1/3 the volume of the filtrate collected. How much time will be required to wash the cake when the same pressure is applied?

a	12.98hrs
b	17.33hrs
c	16.05hrs
d	10.72hrs

Answer 1

sy For constant pressure filtratia » [t= kv? 4.5*3 total filtrate obtained fel V = 13.5 ft] in t=6.5 hz now t=ky? 6.5 = K (13-5)? K = 0.0356 now , differentiating dv dt 2kY & X0.0356 413.5 dv 1.04 ft3/hr dt For plate & frame : I Washing 4 • x 107 = 0.2667% tate of 1 4x Jake of fistration x Volume this time of washing f Washing fluid user zate of washing 13.5 x 13 = 17.33 hr 0:26 Ans is (b)