Brief introduction of cleaning methods in the past

To clean spinnerets, packs and pack parts, following methods have been using for a long time.

  • Calcination :
    In automatic box type furnace, the spinnerets are heated to 450～480℃.
    When temperature is over 480℃, a superheated steam will blown out the flames to lower the temperature so that the spinnerets can be prevented from being damaged.
    disadvantage : the cleaning result is not so good and this is dangerous.
  • Salts Bath :
    Formed by NaNO345%-NaNO245%-NaOH10% in mixture, salts bath acts as strong oxidant at its operating temperature, i.e., 450～500℃.
    The polymer is decomposed to CO2 and H2O within 60 to 90 minutes.
    After processed, remaining salts on spinnerets can be washed out by hot water and oxide removed by thin nitric acid.
    disadvantage : some materials for spinneret and pack can be corroded by salt and remove of waste sludge is very dangerous and it requires the additional cost to throw into discard.
  • Fluid Bed :
    At temperature of 450～500℃, quartz sand powder is fluidified by compressed air and clean the spinnerets. Polymer is removed and decomposed into the exhaust gas.
    Carbon becomes CO. All these including inorganic substances, such as TiO2, are discharged in the air.
    advantage : economc, safe and fast. Good cleaning result.
  • TEG :
    First put spinnerets in boiling solution which contents NaOH(15～20%)for 2 to 3 hours to remove most of the polymer, then in TEG bath at 260～280℃ for about 12 hours.
    After cooled. spinnerets should still be washed sequentially in alkaline solution, water and ultrasonic tank before they can be dried and stored up.
    This process can avoid overheat and is suitable for any type of stainless steel, but needs rather long time.
    advantage : good cleaning result
    disadvantage : very dangerous and high operation cost
  • Vacuum Calciner :
    Burning in low pressure and vacuum, most of the polymer can be decomposed.
    Remaining substances are washed out by water in the same furnace.
    The whole process can be automatically controlled and easily operated.
    disadvantage : very long cleaning cycle, low cleaning quality, especially the material of parts to be cleaned becomes to be weak due to the decaburization during the cleaning process.