I. Overview
A blade dryer is a conduction-type energy-saving sludge treatment equipment. The device indirectly heats sludge generated from wastewater and sludge of a paste-like to slurry-like consistency, achieving dehydration and drying to reduce volume, and then utilizes it comprehensively, turning waste into treasure, thus avoiding secondary pollution. It is an ideal drying equipment for sludge treatment at present. Conduction refers to the heat carrier not directly contacting the material being dried but instead, the heat surface conducts with the material for drying.
Part II: Principle
The hollow shaft is densely arranged with hollow propeller blades in the model, with the heat medium flowing through the blades via the hollow shaft. The heat transfer area per unit effective volume is large, with the temperature of the heat medium ranging from -40℃ to 320℃, which can be steam or liquid types such as hot water, thermal oil, etc. Indirect conduction heating is used, with no air carrying away heat, ensuring all heat is used to heat the material. Heat loss is only due to the heat dissipated through the insulation layer of the equipment to the environment. The heat transfer surface of the model propeller blades features an auto-cleaning function. The relative motion between the material particles and the model surface generates a scrubbing effect, which can wash off the adhered material on the blade surface, maintaining a clean heat transfer surface during operation. The shell of the propeller dryer is W-shaped, generally housing two to four hollow mixing shafts inside. The shell is equipped with a sealed end cap and an upper cover to prevent the leakage of material dust and the collection of solvent vapor from the material. A gate valve is set at the discharge outlet to ensure the material level, covering the heat transfer surface and fully utilizing its function. The heat medium flows through the rotating joint, passing through the shell jacket and the hollow mixing shafts. The hollow mixing shafts have different internal structures depending on the type of heat medium to ensure effective heat transfer.
Section 3: Features
Low energy consumption of paddle blade dryer: Due to indirect heating, there is no large amount of air carrying away heat, and the outer wall of the dryer is insulated. For slurry materials, only 1.22 kg of steam is needed to evaporate 1 kg of water.
2. Low-cost Propeller Blade Dryer System: With a large heat transfer surface per unit effective volume, the processing time is shortened. The reduced equipment size greatly minimizes the building area and space.
3. Wide Range of Material Processing: Handles materials with various thermal mediums, suitable for both heat-sensitive materials and those requiring high-temperature treatment. Common mediums include steam, thermal oil, hot water, and cooling water. Both continuous and intermittent operations are available, applicable in numerous fields.
4. Low environmental pollution: No air-carrying substances used; dust material carryover is minimal. Material solvent evaporation is low, easy to handle. For situations involving polluted materials or the need to recover solvents, closed-loop circulation can be employed.
5. Low operational costs: The equipment operates normally with only 1-2 people per day. Low-speed mixing and a reasonable structure. Minimal wear and low maintenance costs.
6. Stable Operation: The unique compression-expansion mixing action of the wedge-shaped paddle blades ensures thorough contact between the material particles and the heat transfer surface. Within the axial range, the temperature, humidity, and mixing gradient of the material are minimal, thereby guaranteeing the stability of the process.
Section 4: Techno-economic Parameters of Sludge Drying
The sludge moisture content is around 80% before drying.
2. The moisture content after drying is generally between 10-50%.
3. Volume Change: Volume reduces by 4 to 5 times after drying.
4. Evaporating 1kg of water requires only 1.1-1.3kg of steam.
