Hot condensate is a target for energy savings. If the pressure is high, steam can be recovered by installing a flash drum to recover the required steam pressure. The unrecoverable energy is recovered as depressurized condensate.
If it is not recovered with flash steam, it may cause hammering in the condensate pipe at the downstream end, so installing and operating a flash drum is essential.
Formula of LMTD
Amount of flash steam generated by hot condensate can be calculated using the following formula:
mfs = mc*(hc-hfc)/(hfs-hfc)
mfｓ : Flash Steam Flow Rate (kg/h)
mc : Condensate Load (kg/h)
hc : enthalpy of condensate (kcal/kg)
hfs : enthalpy of flash steam (kcal/kg)
hfc : enthalpy of saturated water (kcal/kg)
Python code
The following is a Python example where 100 lb/hr of hot condensate is introduced into a flash drum at a pressure of 120 psig and flashed with 60 psig steam, and approximately 4.91 lb/hr is recovered as flash steam.
from pyXSteam.XSteam import XSteam
steamTable = XSteam(XSteam.UNIT_SYSTEM_FLS) # ft/lb/sec/°F/psi/btu
def flash(mc, Phc, Pf):
hc = steamTable.h_pt(Phc+14.696, steamTable.tsat_p(Phc+14.696)-1)
hfs = steamTable.h_pt(Pf+14.696, steamTable.tsat_p(Pf+14.696)+1)
hfc = steamTable.h_pt(Pf+14.696, steamTable.tsat_p(Pf+14.696)-1)
return mc*(hc-hfc)/(hfs-hfc)
print("flash steam flow = ", flash(100, 120, 60)) # 100 lb/hr, 120 psig, 60 psig
flash steam flow = 4.91
