Question 14 from the morning session, case 14
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14. Filter a certain suspension using a rotary drum vacuum filter, with a slurry processing capacity of 50 m3/h. It is known that 0.05 m3 of filter cake can be obtained from 1 m3 of filtrate; the immersion depth of the drum is required to be 0.35, and the thickness of the filter cake on the filtration surface must be at least 7 mm. The filter cake is incompressible, and the resistance of the filtering medium can be ignored; the measured filtration constant is K=8×10^(-4) m2/s. What is the filtration area (in m2) of the filter, among the following values? A 5.32 B 8.67 C 6.62 D 7.39 Please, experts, provide a detailed solution process. The formula Vh=3600A(KΦn)^0.5 can be found in the book, but it’s not clear how to determine the rotational speed n; or rather, this formula is not used. Also, it’s not clear how to ensure that the filter cake thickness is at least 7 mm
I also got stuck on finding the value of n during the exam back then. The real reason was that I didn’t understand the principle of the rotary vacuum filter: one rotation of the filter drum corresponds to one complete filtering cycle, which includes filtration, washing, and discharge processes. Since the volume of the filter cake after one rotation can be determined, the total volume of the filter cake can also be calculated. Thus, the rotation speed n can be found by using the relationship between the volumes of the filter cake. This is the key to solving the problem. You can search on forums for solutions to this problem; someone has posted a solution that is actually based on an original question from a textbook on chemical engineering principles (with only the numbers changed). You should take a look at it
Let me check; I’m not sure which version from Tian Da it is