Column feed temperature control with economizer and preheater enthalpy cannot be measured directly, it must be calculated as follows:
4>f = cp/Ti + —cpb (Tm - TB2) + — iJ/s (5.1)
where tfjF = enthalpy of feed entering column, pcu/lbm cpf — feed specific heat, pcu/lbm °C
Tbi = temperature, degrees Celsius, of bottom product entering economizer Tb2 = temperature, degrees Celsius, of bottom product leaving economizer T, = feed initial temperature, degrees Kelvin (= °C + 273) wB = bottom-product flow rate, lbm/min wF = feed rate, lbm/min
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