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Double effect evaporation startup and control

Start Double effect evaporation with default parameters. The objective of this exercise is to start the installation and set it to produce a 25% mass fraction concentrate from a 7% mass fraction feed

  • Set cooling water to condenser, read feed tank holdup, and check evaporators levels are around 90%
  • Start MP evaporator heating with steam valve fully open
  • Fully open degasing valve of MP evaporator to LP overhead line
  • Open degasing valve of LP evaporator at 20%, and start vaccuum pump at 100%
  • When MP evaporator begins to boil, let the pressure increase up to 3 bar a then decrease degasing
  • Control LP evaporator thermosiphon startup (flow, heating), and decrease heat input to the MP evaporator if needed to limit pressure to 4.5 bar a, and keep relief valve closed
  • When the LP evaporator start to boil, control vapor condensation
  • Set the following controllers in automatic: feed flowrate, heating steam flowrate, MP and LP evaporator levels, condensate drum level, and start draw off pumps
  • Decrease MP degasing valve to ~10%, and set vaccuum pump at 50% and degasing/recirculation valve closed on LP evaporator
  • Adjust feed and heating steam flowrates to reach a fixed mass fraction of 25% for second effect concentrate (example)
  • Check global and partial mass balance when the process reach steady state
  • Check energy balance and calculate the economy of this double effect evaporator
  • Shutdown the installation, empty all capacities, and estimate the installation holdup during normal operation