• Utilization of Low-Temperature Thermal Energy:
The EVD system supplies internal thermal circulation using a highly efficient heat pump that delivers low-temperature heat energy at an average of 60–100°C. This minimizes heat loss and maximizes energy efficiency.
• When combined with the first-stage dewatering process (ELODE):
ELODE effectively removes various forms of water present in sludge—including capillary water, intracellular water, bound water, and free water—through electro-osmosis, electrophoresis, and infiltration. During this process, gluezone components are also broken down, resulting in the formation of a high-quality PAN-CAKE-type sludge.
• PAN-CAKE Characteristics:
As the sludge passes through compression equipment such as belt, drum, or caterpillar systems, the cell walls are broken, creating numerous fine porous structures (pinholes) inside. This PAN-CAKE structure features a cracked surface resembling a turtle shell, which expands the surface area and significantly improves drying efficiency. (See photo below)
• Generation of Coulomb Heat:
During DC three-phase electro-osmosis and electron migration, positive and negative charges rapidly move, naturally generating Coulomb heat. As a result, the internal temperature of the sludge cake can reach 40–80°C at the moment of dewatering, and this heat continuously facilitates moisture evaporation.
• Sludge Feeding and Slitting:
The EVD is equipped with a specially designed SSD (Sludge Slitting Distributor), which cuts the PAN-CAKE sludge into uniform thickness and evenly feeds it onto the internal conveyor belt. This improves both drying efficiency and process stability.
•Evaporation and Condensation:
The sludge is exposed to a sustained supply of thermal energy within a low-temperature heat-storing environment. The heat pump enhances efficiency by recovering energy. The evaporated moisture is recovered through a condenser in a clean state with almost no suspended solids (SS), ensuring minimal odor and environmental friendliness.
• Applicable Sludge Types:
For sludge with low organic content, inorganic composition, or extremely low conductivity, the principle of electro-osmosis cannot be applied, making the ELODE dewatering process unsuitable. In such cases, the EVD system is installed and operated independently.
• Performance Guarantee Limits and Variables:
When operated as a standalone system, the EVD can guarantee drying performance for inlet moisture content up to 80% and final moisture content below 40%.
However, differences may arise in the following seven key performance indicators compared to combined operation with ELODE.
• Pre-conditions for Guarantee:
To provide reliable guarantee metrics to clients, a preliminary on-site test (pilot test) using at least 1 ton of sludge is required to verify process compatibility and performance.
• Testing Costs and Contract Terms:
The pilot test is charged at a cost, but the testing fee will be deducted from the total contract amount if the main project contract is signed afterward.
• Response for New Plant Projects:
For new projects where actual sludge data is unavailable, a preliminary review based on similar sludge characteristics is conducted. Ideally, an EVD unit should be installed on-site and tested for at least three days to minimize project risk and secure performance guarantees.
Municipal
18%DS
95%DS
Industrial
15%DS
90%DS
3. Technical Advantages and Competitive Strengths
• Guaranteed Moisture Reduction:
Capable of achieving as low as 10% moisture content, typically below 20%, ensuring the production of high-quality dried sludge.
• Energy Efficiency:
Consumes approximately 400W per liter of water evaporated, achieving at least 40%–60% energy savings compared to traditional thermal dryers using hot air.
• Compact Installation Footprint:
Requires only 1/5 the space of conventional thermal dryers, significantly enhancing space utilization.
• Low Maintenance Costs:
Maintenance costs are approximately one-tenth of traditional systems, ensuring superior operational cost competitiveness.
• Equipment Durability:
Robust design guarantees a minimum equipment lifespan of 30 years, reducing long-term capital expenditure.
• Environmental Benefits:
The evaporated water is discharged as clean water with minimal suspended solids, and odor emissions are extremely low, promoting a safe and eco-friendly work environment.
Sludge Dryer Comparison | ELODE (EODS-3000) | NVD (Model-3000)/ EVD (Model-10800) | Conventional Thermal Dryers (DDS, FBD, KILN, BD etc) |
|---|---|---|---|
Typical Wet Sludge Feed Rate | 30 Wet Tons/Day | 15 Wet Tons/Day | 30 Wet Tons/Day |
Dry Solids Achieved | Up to 40%DS | Up to 90%DS+ | Up to 90%DS+ |
ROI | 24 months | 24 months | - |
Drying Process | By DC Electro-Osmosis+ Electro-Penetration+Electrophoresis | Evaporation by Heat Pump | Boiling by Furnace |
Area (sqm) | 12 sqm | 37 sqm | +500 sqm |
Energy to Remove 1 Ton of Water | 180 kWh | 300 kWh | 1,200 kWh (Heat Equivalent) |
Stock Unit | Yes | Yes | No |
Additional Equipment | Minor | Minor | Several Required |
Maintenance | Low | Low | High |
Installation & Building Cost | Low | Low | High |
Processing Speed | 3 Minutes | 1 – 2 Hours | Hours |
Startup Time | 2 Minutes | 15 Minutes | Hours |
Odors Produced | Low | Mid | High |
Dust Produced | None | Low | High (Req. Extra Equipment) |
Building Temperature Increase | Low | Mid | High (Unbearable) |
The EVD uses warm air convection inside a closed loop heat pump dryer without heat loss:
1. Sludge cake enters the shaping machine inlet, evenly extruding and distributing the cake "spaghetti" across the belt.
2. Dry warm air passes over the wet cake, collecting moisture as the two belts convey the dried cake to the exit.
3. The A/C evaporator fins capture the moisture.
4. The dehumidified warm air is reheated by the heat pump and sent back into the drying chamber.
5. The dried sludge cake is discharged and conveyed away from the dryer.
The Evaporative Dryer (EVD) further dries cake produced by either ELODE or mechanical dewatering equipment.
(eg. belt press, screw press, centrifuge)
This low temperature belt dryer processes cake at 10%DS+, drying it up to 90%DS+ to achieve Class A biosolids with a low operating temperature (≤80˚C).
The EVD uses heat pumps in a closed loop, convection process to maximize heat recovery and minimize energy waste, consuming
400 kWh to remove 1 ton of water.
EVD Specifications | 3600 Model | 7200 Model |
|---|---|---|
| Typical Wet Sludge Cake Feed Rate | 6 wet tons/day | 12 wet tons/day |
| Water Removal Rate / 24hr | 3,600 kg | 7,200 kg |
| Water Removal Rate / hr | 150 kg | 300 kg |
| Typical Power Consumption | 60 kW Running 80 kW Peak** | 108 kW Running 138 kW Peak** |
| Base Unit Dimension (L x W x H) | 151 x 135 x 139 in 4830 x 2215 x 2420 mm | 375 x 88 x 96 in 9500 x 2215 x 2420 mm |
| Base Unit Weight (Est.) | 5 tons | 8 tons |
| Assembly Required | Yes | Yes |
| Typical Input Cake Solids | 10–50%DS (Depends on sludge characteristics) | |
| Typical Output Cake Solids | 40–90%DS+ (Depends on sludge type; 95%DS Max Observed) | |
| Drying Temperature | Typical Return Air: 40–65°C; Typical Supply Air: 60–80°C | |
| Energy to Remove 1 Ton of Water | 400 kWh | |
| Power Supply | 3 Phase, 480 V, 60 Hz | |
| Utilities Required | Electricity, drain Optional: vent duct | |
| Construction | SS304, SS316 Stainless Steel | |
| Refrigerant | R134a | |
| Cooling Method | Air Cooling | |
| Shaping Method | Strip Cutting | |
| Control System | Touch Screen + PLC + VFD | |
Note: Specifications are subject to change depending on many factors. There are thousands of types of sludge - we may modify the machine to better suit our customer’s application.
Peak kW = total power when preheating coil is on, including compressors, electrical heating, fans, and gear motors for shaping machine and exit conveyor.
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