Wet Air Oxidation Technology
What is AquaCritox?
Using our patented hydrothermal oxidation process, AquaCritox oxidises all oxidisable compounds present in wet waste (such as spent caustic) – converting them into inert by-products and producing a non-toxic, odourless effluent.
AquaCritox can be used to treat a variety of wet wastes, including spent caustics, recalcitrant COD and ammonia streams: providing a safe, sustainable and cost-effective handling and disposal solution.
How does it work?
Very simply, hydrothermal oxidation (HTO) combines specific temperature and pressure levels with an oxygen supply to oxidise the oxidisable components present in spent caustic. This reaction offers improved efficiency and speed compared to standard wet air oxidation, and typically reduces the COD (chemical oxygen demand) of waste by up to 97% – as well as making it safe for disposal through conventional routes.
- For consistent feed concentration, spent caustic enters AquaCritox via a spent caustic storage tank (V-101), with any oil accumulating at the surface periodically skimmed off and diverted to an oily water tank
- The incoming spent caustic stream is pumped up to the required pressure (at least 190 bar (2,755 psi)) using a high-pressure pump (P-103)
- The pressurised feed is then passed through a heat exchanger (H-201), where it is brought up to temperature (300-374°C (572-705°F)). It then flows to the tubular reactor (R-401).
- The reaction temperature and pressure of the AquaCritox process causes water to behave in a completely different manner, and it becomes a perfect reaction medium. Vaporised liquid oxygen (LOX) is then introduced into the hot pressurised feed, causing an almost immediate oxidation reaction. The resulting oxygen consumption is typically less than 120% of stoichiometric requirement
- Once underway, the exothermic HTO process becomes auto-thermal, using energy recovered from the reactor effluent to heat the incoming waste stream (quench water is used to control the internal reactor temperature when needed)
- The quality of the off-gas is measured to ensure compliance with emissions standards (and to control the oxidation reaction)
- After exiting the heat exchanger, the temperature and pressure of the treated spent caustic is reduced to ambient using the AquaCritox patented pressure control system.
- AquaCritox HTO typically delivers a COD reduction of more than 97% for spent caustics and 99.99 % for gas liquors.
- After processing, the odourless, foam-free and benign treated liquor is now suitable for disposal through conventional wastewater treatment plants, and is highly amenable to biological treatment.