Wet-air oxidation process

Because powdered activated carbon is generally used in relatively small quantities, the spent carbon has often been disposed of in landfills. However, landfill disposal is becoming more restrictive environmentally and more costiy. Thus large consumers of powdered carbon find that regeneration is an attractive alternative. Examples of regeneration systems for powdered activated carbon include the Zimpro/Passavant wet air oxidation process (46), the multihearth furnace as used in the DuPont PACT process (47,48), and the Shirco infrared furnace (49,50). 

Figure 1. Thermodynamic properties of moist gases from a wet-air oxidation process.

Raeder H, Bredesen R, Crehan G, Miachon S, Dalmon J-A, Pintar A, Levee J, and Torp EG. A wet air oxidation process using a catalytic membrane contactor. Sep. Purif. Technol. 2003 32 349-355. 

The Zimpro wet air oxidation process (13) can effectively restore the adsorptive properties of PAC without dewatering of the spent carhon slurry. Estimated carbon loss is about 5% per regeneration cycle. Zimpro, Inc. has used the wet air oxidation process to regenerate PAC used in wastewater treatment. A pilot plant was set up in Rothschild, WI, USA. The carbon was used through 23 cycles, and the average loss of the activated carbon per cycle was 4.7%. 

Figure 10.2. Simplified flow chart of the catalytic wet air oxidation process.

Luck, F. (1996). A Review of Industrial Catalytic Wet Air Oxidation Processes. Catal. Today, 27, pp. 195-202. 

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