I am trying to understand a mass balance sheet for an ethanol plant. Looking at the beer column overhead vapor here's the original conditions:

flow 80,064 lb/hr

vapor mole frac. 1

mass fractions:

-water 0.44125

-ethanol 0.595875

Enthalpy -287.43 MMBtu/h

Temp 229.3166F

Press 30.2286 psia

I'm not a chemical engineer, so having a little trouble understanding the enthalpy value.

I'm using NIST Refprop software, and for that same mixture at that temperature and pressure their enthalpy value for vapor phase is 696.99 btu/lbm

multiply that by the flowrate and i'm getting 55.8MMBtu/h.

I'm sure I'm missing some fundamental principle, but i'm stumped as to why it's a negative value and so much more than what i'm coming up with.

Any help is greatly appreciated. Thanks!