Consultation on distillation column installation factor

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a) Hello, the installation factor of the distillation column seems to be a little high. The installation factor of the distillation column in NREL (corn stover 2011 model) is 2.4-2.8 (as shown in the figure below), while that in BioSTEAM is 4.3 (https://biosteam.readthedocs.io/en/latest/_modules/biosteam/units/distillation.html#Distillation:~:text=_F_BM_default%20%3D%20%7B,%3A%201.%7D). Is that not right?

b) If I want to change the installation factor of the distillation column and its related equipment, could I ask you how to change it?

c) I build distillation tower with bst.BinaryDistillation(ins, P=101325, Lr=0.999, Hr=0.99, k=1.2, Rmin=0.001, LHK=()). However, the sum of equipment purchase cost (4.46E+06) in excel's Design requirements data table (as shown in the figure below) is lower than the purchase cost (4.49E +06) in Itemized costs data table. May I ask you why?

d) May I ask you what the installation factor of other distillation column related equipment (Condenser - Double pipe, Reflux drum - Vertical pressure vessel, Reflux drum - Platform and ladders, Pump – Pump, Pump – Motor, Reboiler - Floating head) is? It doesn't seem to be specified in the code (https://biosteam.readthedocs.io/en/latest/_modules/biosteam/units/distillation.html#Distillation:~:text=_F_BM_default%20%3D%20%7B,%3A%201.%7D). Thanks for your help. Wish you a good day.