Low-temperature drying of inorganic sludge with high moisture content, which is difficult to process/ Test cases / Sludge dryer

■ Low-temperature drying of inorganic sludge with high moisture content, which is difficult to process/ KENKI DRYER / Sludge dryer



Japan is almost 100% dependent on imports for mineral resources, and securing precious and rare metals in particular is essential to maintaining and strengthening its international competitiveness. Reusing and recycling minerals from sludge will lead to environmental protection and greenhouse gas reduction, and in particular, the extraction of phosphorus, on which Japan depends on China, is being promoted as a national project. Recycling sludge discharged from wastewater treatment plants is becoming increasingly important for environmental protection, decarbonization, and resource security, and demand for such recycling is growing.
KENKI DRYER is a revolutionary drying system with unique technology that enables smooth drying of sticky drying objects, and has been granted two patents in Japan and nine patents in seven foreign countries. The continuous low-temperature drying technology minimizes compositional changes and is suitable for recycling and upcycling. Utilizing steam as the heat source, the system emits no CO2 and provides an environmentally friendly drying method. Maintenance is easy, and unattended 24-hour operation is possible.
The KENKI DRYER excels in drying sticky and adhesive materials and is suitable for drying organic waste with high moisture content, sludge, slurry, and methane fermentation digested liquid. KENKI DRYER has been granted 11 patents in 8 countries: Japan, Taiwan, USA, France, Germany, UK, Switzerland, and Canada.


Japan relies on imports for almost 100% of its mineral resources. In the future, precious metals and rare metals in particular will continue to be important resources, and securing these resources is essential for maintaining and strengthening international competitiveness. One of the measures to secure mineral resources is to reuse and recycle minerals contained in sludge, which will contribute to environmental protection and reduce greenhouse gas emissions. Phosphorus, which is currently imported from China, is also an indispensable mineral. Therefore, the extraction of phosphorus from sewage sludge is being promoted as a national project.
The recycling of sludge from wastewater treatment plants is becoming increasingly important for environmental protection, decarbonization, and securing imported resources.

KENKI DRYER is a revolutionary drying device with a total of 11 patents (2 in Japan and 9 in 7 foreign countries) for its unique technology.

KENKI DRYER can easily and smoothly dry even highly sticky and difficult-to-dry materials. For example, highly sticky sludge is difficult to dry. KENKI DRYER’s unique, world-patented mechanism allows sludge to be dried smoothly without clogging the dryer, no matter how sticky or adhesive the sludge is, and no matter how high the water content. In addition, since the KENKI DRYER is a continuous low-temperature drying system, there is little change in the composition of the dried material after drying, making it suitable for a wide variety of applications.

Sludge discharged from wastewater treatment plants tends to become lumpy during the drying process due to the coagulant used in wastewater treatment. In the drying process of the KENKI DRYER, even if the dried sludge becomes lumpy, it is crushed to a certain extent in the dryer to reduce its surface area, which allows the dried sludge to be dried more than adequately. This allows the dried material to be dried to the inside of the dryer.

KENKI DRYER dries sludge discharged from wastewater treatment plants at low temperatures so that the composition of the dried materials remains unchanged after drying and can be recycled and upcycled. It can be fully utilized as recycled and upcycled products.

KENKI DRYER, with 11 patents in 8 countries, is an indirect steam dryer, but it is a completely unique product, different in structure from other similar indirect steam dryers. Direct-fired dryers, such as burners, emit carbon dioxide from the dryer, which is against the times in terms of environmental protection and decarbonization, and drying at high temperatures means high fuel costs, rapid wear of parts, and high maintenance costs.

Although KENKI DEYER uses steam as a heat source, it does not produce more global warming gases and CO2 than KENKI DRYER during drying. In addition, the KENKI DRYER uses less steam due to its high drying heat efficiency, so you can use the steam you currently use, and if you use the excess steam, the fuel cost will not increase and the CO2 emissions will not increase compared to boilers that generate steam during the drying process. Alternatively, by installing an electric boiler, drying can be done in a decarbonized manner, without producing any greenhouse gases or CO2 emissions during the drying process.

There are no problems after start-up, and the blades of the dryer’s main body rotate at a very slow speed of 5 RPM or less, so parts wear is minimal and maintenance is easy and inexpensive. KENKI DRYER is a continuous dryer, not a batch dryer that stores and dries materials to be dried. Therefore, operation is simple and unmanned operation is possible 24 hours a day.

Drying sludge to reduce the weight and volume of waste products can contribute to environmental protection and decarbonization by reducing the cost of industrial waste, which is increasing due to the recent trucking problem in 2024, and by reducing the number of trucks transporting waste, thereby reducing carbon dioxide emissions.

KENKI DRYER, which can dry sticky and adhesive materials that cannot be dried anywhere else, is an epoch-making dryer with a total of 11 patents (2 in Japan and 9 in 7 foreign countries). Please consider KENKI DRYER for your high moisture content organic waste dryer, sludge dryer, slurry dryer, methane fermentation digested liquid dryer, and waste recycling dryer.
KENKI DRYER has been granted 11 patents in 8 countries (Japan, Taiwan, USA, France, Germany, UK, Switzerland, Canada).





waste reduction sludge drying sludge dryer kenki dryer 29.06.2024


kenki dryer front KENKI DRYER


■ What is inorganic?


Inorganic refers to substances that are not derived from living organisms and typically do not contain carbon-hydrogen bonds. This term is used in chemistry to describe a broad range of materials and compounds, including minerals, metals, salts, and certain gases. Inorganic chemistry is the branch of chemistry that deals with the properties and behavior of inorganic compounds.

Key characteristics of inorganic compounds include:

  1. Composition: Often composed of elements other than carbon, though some carbon-containing compounds like carbonates and cyanides are considered inorganic.
  2. Structure: Typically have simple structures, though some, like silicates, can be quite complex.
  3. Properties: Can have a wide range of properties, including being solids, liquids, or gases at room temperature; having high melting and boiling points; and being good conductors of electricity (in the case of metals).

Inorganic compounds are found in various forms and are used in numerous applications, from construction materials (like cement and glass) to catalysts and semiconductors.



■ What is sludge?


Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. It can be produced as a settled suspension obtained from conventional drinking water treatment, as sewage sludge from wastewater treatment processes or as fecal sludge from pit latrines and septic tanks. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this soupy material usually contains significant quantities of interstitial water (between the solid particles). Sludge can consist of a variety of particles, such as animal manure.

Source:Wiki Sludge


■ What is inorganic sludge?


Inorganic sludge refers to the semi-solid material that results from the treatment of wastewater, industrial processes, or other activities that involve the removal of inorganic contaminants. This type of sludge is primarily composed of non-organic materials such as metals, metal oxides, minerals, and other inorganic compounds. Inorganic sludge can originate from various sources, including:

  1. Industrial Processes: Industries such as mining, metal processing, and chemical manufacturing often produce inorganic sludge as a byproduct of their operations.
  2. Water and Wastewater Treatment: During the treatment of water and wastewater, inorganic particles are removed through processes like coagulation, flocculation, sedimentation, and filtration, resulting in the formation of inorganic sludge.
  3. Construction and Demolition: Activities in construction and demolition can produce inorganic sludge, particularly when dealing with concrete, bricks, and other building materials.

Key characteristics and considerations of inorganic sludge include:

  • Composition: Rich in metals, metal oxides, silica, and other inorganic substances.
  • Disposal and Management: Inorganic sludge often requires special handling and disposal due to the presence of hazardous materials such as heavy metals. It may be treated, stabilized, and disposed of in landfills or used in certain construction applications if deemed safe.
  • Environmental Impact: Improper management of inorganic sludge can lead to environmental contamination, particularly if it contains toxic substances. Therefore, it is subject to strict regulatory controls to ensure safe handling and disposal.

The management of inorganic sludge is crucial for minimizing its environmental impact and ensuring compliance with environmental regulations.



■ Reasons for drying sludge


There are several key reasons why sludge, often produced as a byproduct of wastewater treatment, needs to be dried:

  • Volume Reduction: Sludge typically contains a high percentage of water. Drying significantly reduces this water content, leading to a much smaller volume. This makes transporting and storing the sludge far more manageable and cost-effective.

  • Disposal and Further Treatment: Dried sludge can be easier and safer to dispose of compared to wet sludge. For instance, dried sludge can meet specific regulations for incineration or landfilling. In some cases, drying can also be a precursor to other treatment methods.

  • Resource Recovery: When properly dried, sludge can be repurposed for beneficial uses. This could involve using it as a soil conditioner or even converting it into a fuel source.

  • Pathogen Reduction: Drying can help reduce the number of harmful pathogens present in the sludge. This makes it a safer material to handle and potentially reuse.

  • Odor Control: Wet sludge can be quite odorous. Drying helps to stabilize the sludge and significantly reduces unpleasant smells.



■ Why sludge drying is difficult?


Sludge drying is a challenging process due to several factors that complicate its efficient and effective execution. Here are the main reasons why sludge drying can be difficult:

  1. High Moisture Content:

    • Initial Moisture Levels: Sludge typically has a very high initial moisture content (up to 98% water), which requires significant energy to reduce.
    • Bound Water: Some water in sludge is chemically bound to particles, making it harder to remove through conventional drying methods.
  2. Energy Requirements:

    • High Energy Consumption: Drying sludge to a low moisture content requires substantial energy, especially for thermal drying processes.
    • Cost: The energy costs associated with sludge drying can be high, impacting the overall economics of the wastewater treatment process.
  3. Complex Composition:

    • Variable Composition: Sludge composition can vary widely depending on the source and type of wastewater being treated. This variability can affect drying efficiency and the selection of appropriate drying technologies.
    • Presence of Inorganic and Organic Materials: The mixture of organic and inorganic materials in sludge can complicate the drying process.
  4. Handling and Processing:

    • Sticky and Viscous Nature: Wet sludge can be sticky and viscous, making it difficult to handle, transport, and process in drying equipment.
    • Clogging and Fouling: Sludge can clog or foul drying equipment, requiring frequent maintenance and cleaning.
  5. Environmental and Health Concerns:

    • Odor Emissions: Drying sludge can produce unpleasant odors, which need to be managed through odor control systems.
    • Air Pollution: Thermal drying processes can release volatile organic compounds (VOCs) and other air pollutants, necessitating air pollution control measures.
  6. Equipment and Technology:

    • Specialized Equipment: Sludge drying often requires specialized equipment, such as belt dryers, drum dryers, or fluidized bed dryers, which can be expensive to purchase and maintain.
    • Operational Complexity: Managing the drying process requires skilled operators to ensure optimal performance and to address any issues that arise during operation.
  7. Disposal of By-products:

    • Residual Waste: Even after drying, there is still a need to dispose of the dried sludge or its ash if incinerated, which can involve additional costs and regulatory compliance.
  8. Regulatory Compliance:

    • Stringent Regulations: There are often strict regulations governing the drying and disposal of sludge, particularly concerning emissions and pathogen reduction, which can add complexity to the process.

In summary, sludge drying is difficult due to high moisture content, significant energy requirements, complex sludge composition, handling challenges, environmental and health concerns, specialized equipment needs, and stringent regulatory requirements. These factors make sludge drying a technically and economically challenging process in wastewater treatment.



KENKI DRYER kenki dryer back 13.06.2024


Woman illustration inorganic sludge drying kenki dryer inorganic sludge dryer 03.07.2024



■ Low-temperature drying of inorganic sludge with high moisture content, which is difficult to process / Test cases




■ Low-temperature drying of inorganic sludge with high moisture content, which is difficult to process / Test result 


  • Material to be dry: Inorganic sludge
  • Purpose of drying: Reducing industrial waste cost and amount
  • Moisture content: 79.6%W.B. before drying, 15.8%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

sludge drying before and after kenki dryer sludge dryer 03.07.2024



Sludge drying

Competitive comparison


■ Self-cleaning screw / Steam Heated Twin Screw Technology
( SHTS technology )


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


■ Product characteristics

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.



■ Drying process


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.



■ Heat source, Saturated steam


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


Please consider KENKI DRYER for drying of sticky materials, adhesive materials and materials in liquid state that no other dryer can deal with.
Initial, running and maintenance costs are low because of its simple structure based on internationally patented technology.
For sludge drying, costs of our dryers are estimated to be retrieved within 2, 3 years by reducing industrial waste disposal cost.
For raw material slurry drying, laborious works of manual operation will be decreased significantly by replacing box shaped compartment tray dryer with our dryer
In case of organic wastes drying, the waste can be recycled as fuel, fertilizer, soil conditioner and feedstuff after being dried.


Company site
No more trouble. Conveyor, Industrial environmental equipment and apparatus
Pyrolyzer Biogreen
A pyrolyser with internationally patented technology which use no fire