introduce B relaxation factor and lower tolerance on distillation/liq…

…uid extractino

biosteam/units/stage.py

@@ -561,7 +561,7 @@ def _create_material_balance_equations(self):
  def _update_energy_variable(self, departure):
  phases = self.phases
  if phases == ('g', 'l'):
- self.B += departure
+ self.B += self.B_relaxation_factor * departure
  elif phases == ('L', 'l'):
  self.T = T = self.T + departure
  for i in self.outs: i.T = T
@@ -593,6 +593,7 @@ class PhasePartition(Unit):
  _N_outs = 2
  strict_infeasibility_check = False
  dmol_relaxation_factor = 0.5
+ B_relaxation_factor = 0.5
  T_relaxation_factor = 0.5
  K_relaxation_factor = 0.5
 
@@ -1069,8 +1070,8 @@ class MultiStageEquilibrium(Unit):
  default_maxiter = 20
  default_max_attempts = 20
  default_fallback_maxiter = 1
- default_molar_tolerance = 0.001
- default_relative_molar_tolerance = 0.0001
+ default_molar_tolerance = 1e-3
+ default_relative_molar_tolerance = 1e-6
  default_algorithm = 'root'
  available_algorithms = {'root', 'optimize'}
  default_methods = {
@@ -2158,7 +2159,7 @@ def get_energy_balance_phase_ratio_departures(self):
  def update_energy_balance_phase_ratio_departures(self):
  dBs = self.get_energy_balance_phase_ratio_departures()
  for i, dB in zip(self.partitions, dBs):
- if i.B_specification is None: i.B += dB
+ if i.B_specification is None: i.B += i.B_relaxation_factor * dB
 
  def update_energy_balance_temperatures(self):
  dTs = self.get_energy_balance_temperature_departures()