The first precaution is to avoid, as far as possible, the entry of hydrocarbons into the main condensing evaporator through the correct operation of the front-end purging adsorber: in addition to removing water from the process air, the purging adsorber must be very effective in removing CO2. Monitoring the CO2 content in the purged air not only helps to operate the purging adsorber correctly in order to remove CO2 and hydrocarbons but also reduces the likelihood of blocking of the main condensing evaporator passages caused by the solid CO2. that could cause blockage of the main condensing evaporator passages. If CO2 penetration of the purification adsorber occurs, the cycle time for switching between the two purifiers should be reduced accordingly.
The second means of preventing the enrichment of hydrocarbons in the main condensing evaporator is the continuous discharge of liquid from the condensing evaporator bath. This unit uses an internal compression process with a liquid oxygen pump, and the product oxygen exits the distillation column in liquid form, so the potential for hydrocarbon build-up is minimal. Despite these precautions, some impurities may still be deposited on the corrugated sheets of the main condensing evaporator after a period of time. As an additional measure, the main-condensing evaporator must be cleaned by thorough defrosting during a heating cycle specifically determined for the unit. To ensure effective defrosting, the temperature and moisture of the defrosted gas at the outlet of the main condensing evaporator should be monitored and defrosting should only be stopped when the required dryness and temperature have been reached.
A section of advanced copper packing is used at the top of the main cooler (at the bottom of the low pressure tower) to replace the traditional aluminium packing. The copper packing is more effective in isolating the main cooler from the combustible aluminium packing. Increased safety.
