Glue-zone

During sludge drying, there is a phenomenon where viscosity suddenly increases within the moisture content range of 65% to 50%.
In this range, the sludge becomes sticky like glue, and the rate of moisture evaporation significantly decreases.
(This is the main cause of energy cost issues, equipment damage, and drying defects in existing drying systems.)

Causing substances of glue zone

• Excess sludge in dewatered sludge (composed of microbial cells)
• Polymer coagulants used in the dewatering process
• Organic coagulants included in dewatered sludge (polysaccharides, sugars, oils, resins, etc.)

Supercritical CO₂ drying technology

To avoid the glue zone, dissolve and extract polymer substances that cause the glue zone using supercritical CO₂ which is a lipophilic substance

• Sludge moisture structure
• CO₂ injection
• Destruction of intracellular CO₂injection
• Dried sludge
• Moisture removal

Comparison of existing and developed technologies

Left and right scrolling is possible.

Schematic diagram
Division	Supercritical CO2	Direct drying	Indirect drying	MW drying
Principle	Dehydration drying by CO2 at medium temperature and high pressure	Direct drying by hot air	Indirect drying by steam heat	Drying using microwaves
Arrangement	Vertical	Horizontal	Horizontal	Horizontal
Evaporation energy required (Kcal/kg)	280	860	760	754
CO2 emissions (g CO2/kg)	113	350	309	307
Products	Below 10%	Below 10%	Below 10%	Below 10%
Thermal medium	Supercritical CO2	Air	Air	Microwave