Generally, the mass transfer unit method or theoretical plate number method is used to calculate the total height of packing layer Z
Z = HTU * NTU = holnol = hognog or Z = HETP * nt
Theoretically, the two-phase concentration in packed tower changes continuously along the tower height, which belongs to continuous (differential contact) mass transfer equipment. Therefore, it is reasonable to use mass transfer unit method to calculate the packing height. However, in some engineering fields (distillation, hydrocarbon absorption, etc.), theoretical calculation is used. Computer software and HETP data for calculating the number of theoretical plates are provided.
There will be some discrepancies between the calculated height of packing layer and the actual needs of production due to the fact that there will be some discrepancies between the calculated packing layer height and the actual production requirements (such as balance data, physical property data, mass transfer coefficient or hog, HETP, etc.). In order to ensure the safety of production needs, but also in order to make the production fluctuations when there is appropriate room for adjustment, so the actual use of filler height must also add a safety factor.