A pilot-plant rotary-drum vacuum filter, with 10 ft² of filter area in tests involving a new product, delivers 9 ft³ /minute (cfm) of filtrate at a total pressure differential of 15 psi. The drum rotates at 2.5 rpm and 25% of the drum is submerged in the feed reservoir. The pilot-plant data are to be used to design a large plant unit, made by the same manufacturer, to deliver 100 cfm of filtrate. The new unit is also expected to run at a ΔP of 15 psi, but with an rpm of 2.0 and a submergence of 30%. The cake compressibility, filtrate viscosity, as well as the medium and cake resistance in the pilot and plant units are expected to be very much alike. 

(a) What should be the drum area for the plant unit? 

(b) Your boss has asked you to recommend desirable and future actions to be taken if production rates have to be increased by 50–400%.