SAPPI – Air heater, condensate system design

Client: SAPPI
Purpose: Redesign the condensate system to reduce steam hammer and improve control
Steam pressure: 62 bar and 3.2 bar
Steam temperature: 285 oC
Mass flowrate: 8 T/hr
Fuel: N/A
Project type: Brownfields

A new air heater system was installed to supply hot air (260 oC) to an evaporation plant. The air heating system made use of Low Pressure (LP) and High Presure (HP) steam to heat the air via fin and tube heat excahngers, which were arrranged in series. High water hammer was being expereinced at the condensate side of the LP steam system and the failure of the HP steam traps was a major concern. A new control philosophywas developed and appropriate modifications proposed to mitigate the steam trap failures and water hammer concerns, whilst improving the control assocaited with each of the heater banks and the subsequent exhaust air temperatures.