Slurry Raw materials drying ,Low-temperature drying of liquid slurry raw materials that change to lumps after drying / Test cases / Slurry drying, Slurry dryer

Liquid materials to be dried, such as slurry raw materials, usually become powdery after drying, but some materials may become lumpy. This is believed to be a characteristic of raw materials that can change from a liquid to a solid state when heated.

The cause of lumping during drying of slurry raw materials depends on the composition and moisture content of the raw material, the type of dryer, and the drying conditions.
In general, it is often caused by sticky substances in the raw materials. Clumping can also be caused by poor flowability in the dryer.
To prevent clumping during drying of slurry raw materials, it is important to properly adjust the composition and moisture content of the raw material, the type of dryer, and the drying conditions. In addition, if the fluidity of the raw materials inside the dryer is important, it is necessary to check the shape and internal structure of the dryer in advance.
In addition, pre-treatment of the raw materials can be considered to reduce stickies in the raw materials.

 KENKI DRYER is an indirect dryer that uses steam as a heat source at low temperatures, so that after drying, the composition of the dried material changes little, making it suitable for manufacturing products.

KENKI DRYER can dry sticky and adhesive materials that others cannot dry. KENKI DRYER is a breakthrough drying device with a total of 11 patents (2 in Japan and 9 in 7 overseas countries). Please consider KENKI DRYER for your high moisture organic waste dryer, sludge dryer, slurry dryer, methane fermentation digestate dryer, and waste upcycling or recycling dryer.

KENKI DRYER has been granted 11 patents in 8 countries (Japan, Taiwan, USA, France, Germany, UK, Switzerland, Canada).

Slurry is a semi-liquid mixture, typically composed of fine solid particles suspended in a liquid. The composition and consistency of a slurry can vary depending on its intended use, but it generally resembles a thick, muddy substance.

Common Types and Uses of Slurry:

1. Construction and Engineering:
   • Concrete Slurry: A mixture of cement, water, and fine aggregate, used as a binding agent in construction.
   • Drilling Slurry: A fluid used in drilling operations to cool and lubricate the drill bit, as well as to carry the cuttings to the surface.
2. Agriculture:
   • Animal Waste Slurry: A mixture of animal manure, water, and sometimes bedding materials, used as a fertilizer in farming.
3. Mining and Mineral Processing:
   • Ore Slurry: A mixture of crushed ore and water used in the extraction and processing of minerals.
4. Food Processing:
   • Food Slurries: Mixtures of food ingredients and water or other liquids, used in the production of various food products, such as soups, sauces, and beverages.

Slurry is a versatile substance used across multiple industries, and its characteristics can be adjusted by altering the ratio of solids to liquids or by adding other materials.

Source：ChatGPT

A slurry that changes into lumps after drying is a mixture where, upon the removal of its liquid component (through evaporation or other means), the solid particles aggregate into distinct lumps or chunks rather than forming a uniform solid or remaining as a powder. This behavior is often seen in materials where the particles have a tendency to stick together as the liquid evaporates.

Examples of Slurries That Form Lumps After Drying:

1. Clay Slurry:

   • Description: A mixture of clay particles and water.
   • Behavior: When dried, clay particles often clump together due to their natural plasticity and the capillary forces during drying, leading to the formation of hard lumps. This is common in ceramics and brick-making.

2. Lime Slurry:

   • Description: A mixture of calcium hydroxide (slaked lime) and water.
   • Behavior: As the water evaporates, the lime particles bind together and form solid lumps. This is used in the production of lime plaster and mortar.

3. Iron Ore Slurry:

   • Description: A mixture of finely ground iron ore and water.
   • Behavior: After drying, the iron ore particles can agglomerate into lumps, which is beneficial in some metallurgical processes like sintering, where larger lumps are needed.

4. Paper Pulp Slurry:

   • Description: A mixture of cellulose fibers and water used in papermaking.
   • Behavior: If dried unevenly, the fibers can bind together into lumps, which can affect the quality of the paper and create defects.

5. Coal Slurry:

   • Description: A mixture of fine coal particles and water.
   • Behavior: Upon drying, the coal particles can clump together into larger lumps. This is often seen when coal slurry is dewatered for storage or transport.

Why These Slurries Form Lumps:

• Particle Adhesion: Certain materials have a natural tendency to stick together when their liquid component is removed, due to surface tension or chemical bonding.
• Capillary Forces: As the liquid evaporates, capillary forces can draw particles together, leading to the formation of lumps.
• Drying Conditions: Uneven drying can cause some parts of the slurry to dry and contract more quickly than others, leading to localized clumping.
• Chemical Reactions: In some cases, chemical reactions that occur as the slurry dries can cause the particles to bond together, forming lumps.

Applications of Lumpy Slurries:

• Ceramics: In ceramics, controlled lump formation in clay slurries is important for shaping and molding processes.
• Construction: In the construction industry, lime or cement slurries are often allowed to dry into lumps as part of the setting process in mortar or concrete.
• Metallurgy: In mining and metallurgy, lumpy products from slurries are often preferred for processes like smelting or sintering, where larger particle sizes are required.

In some cases, the formation of lumps is desirable and intentionally promoted, while in others, it may be an unintended side effect that needs to be controlled or prevented, depending on the desired end-use of the material.

Source：ChatGPT

Preventing the clumping of slurry during drying is essential in many industrial processes to ensure a uniform and consistent final product. Here are some effective measures to prevent clumping:

1. Control Drying Rate:

• Gradual Drying: Dry the slurry slowly to allow the liquid to evaporate evenly, reducing the chance of localized drying, which can lead to clumping.
• Temperature Control: Maintain an optimal temperature that is not too high to prevent rapid drying, which can cause the outer layers to dry and clump while the interior remains wet.

2. Use of Dispersants:

• Chemical Additives: Add dispersants or surfactants to the slurry. These chemicals help to keep the particles suspended evenly in the liquid, preventing them from aggregating as the liquid evaporates.
• pH Adjustment: Adjust the pH of the slurry to enhance the effectiveness of dispersants and improve particle stability.

3. Mechanical Agitation:

• Stirring or Mixing: Continuously stir or mix the slurry during the drying process to prevent particles from settling and clumping together.
• Vibration: Apply gentle vibrations to the slurry to keep the particles in motion, reducing the likelihood of aggregation.

4. Optimize Particle Size Distribution:

• Uniform Particle Size: Ensure the slurry contains particles of uniform size, as a wide range of particle sizes can lead to uneven drying and clumping.
• Grinding and Milling: Pre-process the material to achieve a more uniform particle size distribution before creating the slurry.

5. Use of Anti-Caking Agents:

• Powder Additives: Incorporate anti-caking agents into the slurry. These agents, such as silicates or starches, reduce the tendency of particles to stick together as the slurry dries.
• Hydrophobic Agents: Add hydrophobic materials to create a barrier that prevents moisture from causing the particles to clump.

6. Controlled Atmosphere Drying:

• Humidity Control: Maintain a controlled humidity environment to ensure that the drying process is even and does not cause the slurry to dry out too quickly.
• Airflow Management: Use controlled airflow to promote uniform drying. Proper airflow prevents hotspots that can cause rapid drying and clumping.

7. Pre-Drying Treatments:

• Dehydration: Remove excess water or liquid from the slurry before the final drying stage, reducing the amount of moisture that needs to evaporate and minimizing clumping risks.
• Chemical Stabilization: Treat the slurry with stabilizers that prevent the particles from binding together during drying.

8. Layered Drying:

• Thin Layers: Spread the slurry in thin layers to promote even drying. Thick layers are more prone to uneven drying and clumping.
• Rotational Drying: Rotate the drying material periodically to expose different areas to drying conditions evenly.

9. Use of Specialized Equipment:

• Spray Dryers: Utilize spray dryers that atomize the slurry into fine droplets, which dry rapidly and uniformly, reducing the risk of clumping.
• Fluidized Bed Dryers: Use fluidized bed dryers where the slurry particles are suspended in a stream of air, promoting even drying and preventing clumping.

Implementing these strategies helps maintain the quality and consistency of the dried product, ensuring that it remains free-flowing and lump-free.

Source：ChatGPT

• Material to be dry: Liquid slurry raw materials that change to lumps after drying
• Purpose of drying: Product Manufacturing
• Moisture content: 82.1％W.B. before drying, 1.4％W.B. after drying
• Requirements for dryer: To prevent clogging inside the dryer caused by the stickiness and adhesiveness. Automated continuous operation with no operator attended.
  Machine cost can be recovered in short term.
• Test result: OK

Slurry drying

Competitive comparison

One of the International Patented Technology that KENKI DRYER has is a self-cleaning structure called Steam Heated Twin Screw technology (SHTS technology). No matter how materials are sticky, adhesive and viscous is, they can be dried without clogging inside of the dryer because of this unique structure that no other products has.
For example, even materials stuck to the blades of one screw, blades of the other screw in the dryer’s body forcibly peels the materials off as they rotate. Since the blades rotate by peeling the material off each other, any sticky, adhesive and viscous material does not adhere to the blade, and the blades continue rotating, peeling, agitating and heating material without stopping while they carries material further. Also, since surface of blades are always renewed and kept clean, heat near the blades is not blocked and it is conducted directly into the materials.

Self-cleaning screw

KENKI DRYER has three main characteristics. They are 1) Any materials can be dried as expected including sticky, adhesive and viscous materials and raw material slurry that no other company can deal with, 2) dried material can by recycled or utilized as raw materials because of its low-temperature drying method, and 3) there is no need to assign operator since its continuous operating system makes 24 hours unattended operation possible.

Products

The unique and original drying mechanism of KENKI DRYER is also International Patented Technology. Because 4 drying mechanisms which are crashing drying, agitation drying, circulation drying and indirect drying work simultaneously and add heat to material being dried repeatedly and continuously, inner part of the material is dried thoroughly and quality of discharged material after drying is stable. This series of drying mechanisms prevents agglomeration which causes insufficient drying from feeding process of the material into the dryer until discharging process after drying completed. Various ingenuities to conduct heat surely into inner part of the materials are exercised and stable heating and drying are proceeded continuously.

Methods

Even KENKI DRYER uses only saturated steam as its heat source, it is outstanding in safety and hygiene point of view with its unique drying mechanism based on combined use of conductive heat transfer method and heated air method. Since steam is a stable heat source, quality of discharged material after drying is also stable and equable. Maximum allowed steam pressure is 0.7Mpa and adjustment of steam pressure, adjustment of drying temperature in other words, can be easily done. Saturated steam is commonly used in many factories so that it can be said as a familiar and handy heat source. In comparison with drying methods using burner or hot blasts, saturated steam method is an indirect drying applying heat exchange via pipes that steam is passing through, therefore, it hardly burns the materials and is outstanding in safety and hygiene point of view.

Heat source, Steam