01The challenge
Why does an air separation unit need pre-purification?
Water and CO₂ in feed air freeze in the main heat exchanger and distillation column, blocking flow and forcing warm-up shutdowns. Trace hydrocarbons and N₂O can also build up in the liquid oxygen sump, which is a safety risk. The pre-purification unit must hold CO₂ below about 1 ppm at its outlet.
Our solution
- Grade: activated alumina layer to take up most of the water, then 13X APG beads (1.6–2.5 or 3.0–5.0 mm) for CO₂ and residual water; add a CaX layer where N₂O and hydrocarbon removal is required.
- Regeneration: thermal swing with heated dry waste nitrogen, typically 150–200 °C; typical bed life 5–8 years.
- Outlet spec: CO₂ below 1 ppm and H₂O below 0.1 ppm at the PPU outlet.
02Recommended grades
Which products does a PPU bed need?
03On site
Installed in plants like yours
Which molecular sieve is used for ASU pre-purification?
13X APG is the standard grade for CO₂ and water, usually above a layer of activated alumina. A CaX layer is added when N₂O and trace hydrocarbons must be removed.
Why use activated alumina together with 13X?
Activated alumina takes up bulk water at lower cost and needs less regeneration energy, so the 13X layer is left to remove CO₂ and the last traces of water.
What regeneration temperature does a PPU use?
Most PPUs regenerate with heated dry waste nitrogen at around 150–200 °C, followed by cooling before the bed goes back on line.
How long does a PPU adsorbent charge last?
Typically 5–8 years. Liquid water carry-over, dust and poor regeneration control shorten it.
Replacing a PPU charge or designing a new ASU?
Send air flow, pressure, temperature, cycle time and outlet CO₂ spec — we reply with a layer design, loading quantities and quote within 24 hours.