Urban mining・Minor metal sludge drying, Low-temperature drying for recycling / Test cases / Sludge drying, Recycling drying

Summary

Importance of sludge recycling

• Resource security: Japan is dependent on imports for many of its mineral resources, especially precious and rare metals, which are essential for maintaining international competitiveness.
• Environmental protection: Reusing minerals contained in sludge reduces the environmental impact of mining new resources.
• Decarbonization: Recycling sludge helps reduce greenhouse gas emissions.
• Food security: Phosphorus is the main ingredient in fertilizers, much of which is imported. Phosphorus recovery from sewage sludge is an important issue from a food security perspective.

Solving the problem of drying lumpy sludge

KENKI DRYER solves the problem of drying lumps of dewatered sludge, which easily become lumpy during drying due to flocculants and are difficult to dry inside the sludge.

• Crushing in the dryer: Sludge that clumps together during drying is broken into smaller pieces in the dryer, increasing surface area and reducing drying time.
• Clogging Prevention: A world-patented mechanism prevents clogging in the dryer, ensuring smooth drying process.

High-quality dried products through low-temperature drying

KENKI DRYER uses an indirect drying method by heating steam at low temperature. This provides the following benefits

• Minimized compositional change: Compositional changes caused by high temperature drying are minimized, resulting in high quality dried products suitable for recycling and upcycling.
• Contributes to recycling and upcycling: The dried sludge can be effectively used as a resource.

Reduced environmental impact

• Reduced carbon dioxide emissions: Unlike direct burner drying, steam heating significantly reduces carbon dioxide emissions. Combined with an electric boiler, drying is achieved with zero carbon dioxide emissions.
• Improved energy efficiency: High thermal efficiency reduces steam consumption and fuel costs.
• Reduced waste: Drying sludge reduces the volume of sludge, which in turn reduces waste disposal costs and the carbon dioxide emissions associated with trucking.

Ease of maintenance

• Low-speed rotation: Less load on parts and longer service life.
• Fewer problems : There have been no problems since start-up.
• Reduced maintenance costs: Fewer parts to replace, resulting in lower maintenance costs.

Ease of operation

• Continuous drying: Unlike batch drying, continuous operation is possible, allowing 24-hour unattended operation.
• Simplified operation and management: No complicated operations are required, and anyone can easily operate the system.

Suitable for various applications

• Organic waste with high water content: Not only sewage sludge, but also various organic wastes with high water content can be dried.
• Waste upcycling: After drying, organic waste can be effectively used as fuel, biochar, bio-coke, etc.

Patented Proprietary Technology

• 11 patents granted in Japan and overseas: Unique technology for drying adherent and sticky materials.

Conclusion

The KENKI DRYER is a revolutionary dryer with numerous advantages, including reduced environmental impact, high maintainability, ease of operation, and versatility. In particular, its contribution to environmental issues such as reduction of carbon dioxide emissions and waste volume is attracting attention, and it is expected to be a technology that contributes to the realization of a sustainable society.

Japan is almost 100% dependent on imports for 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 to maintaining and strengthening international competitiveness. One of the measures to secure mineral resources is the reuse and recycling of 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 reuse and recycling of sludge from wastewater treatment plants is becoming increasingly important for environmental protection, decarbonization and securing resources that are currently dependent on imports.

In the drying process of the KENKI DRYER, lumpy sludge and other dried materials are crushed to a certain extent inside the dryer to reduce their surface area, which allows sufficient drying to occur inside the dried materials. Even lumpy dried materials may not be discharged because of clogging inside the dryer due to strong adhesion during drying, but KENKI DRYER’s world-patented unique mechanism prevents clogging inside the dryer and enables smooth drying.

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. The KENKI DEYER uses steam as a heat source, but its high drying heat efficiency means that less steam is used. The use of excess steam is not costly in terms of fuel costs, and the dryer does not emit carbon dioxide during the drying process, allowing for decarbonized drying. Alternatively, by installing an electric boiler, no greenhouse gases or CO2 emissions are produced during drying.

The dryer’s blades rotate at a very slow speed of 5 rpm or less, which means that wear on parts is minimal and maintenance is easy and inexpensive.
KENKI DRYER is a continuous dryer, not a batch dryer that stores 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 rising due to the recent trucking problem in 2024, and by reducing the number of trucks used to transport waste, thereby reducing carbon dioxide emissions.

Currently, there is a shortage of wood in Japan. The use of dried organic waste as fuel instead of wood, or the use of dried organic sludge as biochar or biocoke by carbonization, is attracting much attention. For example, bio-coke can be used as a reductant or deoxidizer to replace coke in the steel and foundry industries.
Biochar and bio-coke are carbonized materials made from biological resources that are effective in revitalizing organisms and improving the environment. We can provide carbonization services using our Biogreen pyrolysis equipment, which does not use fossil fuels and does not emit CO2, a greenhouse gas, so please contact us.

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

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The term “minor metal” refers to a broad range of metals that are not traded on formal exchanges, such as the London Metal Exchange (LME). These metals are often extracted as by-products of base metal smelting and have relatively low annual production volumes compared to base metals. They are used in various high-tech applications, including electronics, solar panels, and batteries.

Some examples of minor metals include tungsten, titanium, cobalt, molybdenum, indium, niobium, and rare-earth elements. These metals are critical to modern technology and are used in a wide range of industries, including pharmaceuticals, semiconductors, automotive, glass, and solar energy.

Source：Perplexity

An urban mine is the stockpile of rare metals in the discarded waste electrical and electronic equipment (WEEE) of a society. Urban mining is the process of recovering these rare metals through mechanical and chemical treatments. In 1997, recycled gold accounted for approximately 20% of the 2700 tons of gold supplied to the market.

The name was coined in the 1980s by Professor Hideo Nanjyo of the Research Institute of Mineral Dressing and Metallurgy at Tohoku University and the idea has gained significant traction in Japan (and in other parts of Asia) in the 21st century.

Research published by the Japanese government’s National Institute of Materials Science in 2010 estimated that there were 6,800 tones of gold recoverable from used electronic equipment in Japan.

Source：Wiki Urban mining

Mineral resources are naturally occurring, solid, inorganic substances with a specific chemical composition and a characteristic crystal structure. They are essential for our modern way of life. Over 95% of the energy we use, 80% of industrial raw materials, and 70% of raw materials for agriculture come from mineral resources.
There are over 2,000 identified minerals, and they can be broadly classified into two categories: metals and non-metals.

Metals are lustrous, ductile, and malleable. They are good conductors of heat and electricity. Examples of metals include iron, copper, gold, and silver.

Non-metals are all minerals that are not classified as metals. They have a wide variety of properties and are used in a wide variety of applications. Examples of non-metals include diamond, sulfur, salt, and limestone.

Source：Gemini

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

“Minor metal sludge” refers to the residual byproducts or waste material that contains minor metals. These minor metals are elements that are not commonly found in large quantities but have significant industrial value. Examples include rare earth elements, indium, gallium, and others used in high-tech applications such as electronics, renewable energy, and aerospace.

The term “sludge” indicates that these metals are in a semi-solid or liquid state, often mixed with other substances. This sludge is typically produced during the processing, refining, or recycling of materials containing minor metals. Proper management and recycling of minor metal sludge are crucial because these metals are valuable and sometimes scarce, making their recovery important for both economic and environmental reasons.

Source：ChatGPT

Inorganic sludge is a type of sludge that is primarily composed of non-organic materials. These materials are typically minerals, metals, and other inorganic substances. Unlike organic sludge, which contains a high percentage of organic matter like bacteria and food scraps, inorganic sludge is more likely to contain sand, grit, and other solid particles.

Common sources of inorganic sludge include:

• Industrial wastewater: Wastewater from factories and manufacturing processes often contains inorganic contaminants.
• Stormwater runoff: Stormwater can carry sand, grit, and other inorganic debris into wastewater treatment plants.
• Construction sites: Construction activities can generate significant amounts of inorganic sludge.

Inorganic sludge is often denser and heavier than organic sludge and may require different treatment and disposal methods. It can be a challenge to remove and dispose of effectively due to its inorganic composition.

Source：Gemini

The key differences between minor metal sludge and inorganic sludge lie in their composition and the types of materials they contain:

1. Composition:

   • Minor Metal Sludge: Contains minor metals, which are elements present in relatively small quantities but are important for various high-tech applications. These metals include elements like indium, gallium, and others that are used in electronics, solar panels, and similar technologies. Minor metal sludge often comes from processes involving the extraction or recycling of these metals.
   • Inorganic Sludge: Contains inorganic materials, which are non-carbon-based compounds. This sludge can include a variety of materials like minerals, metals (both major and minor), salts, and other non-organic substances. Inorganic sludge can originate from industrial processes, wastewater treatment, or mining activities, and it may not necessarily have a significant concentration of valuable minor metals.

2. Sources and Processes:

   • Minor Metal Sludge: Typically generated from specific processes that deal with the recovery or processing of minor metals. This includes refining ores, recycling electronic waste, or extracting metals from industrial residues.
   • Inorganic Sludge: Produced from a broader range of processes, including chemical manufacturing, water treatment, and mineral processing. It is a more general term and can be associated with various types of industrial and environmental processes.

3. Value and Recycling:

   • Minor Metal Sludge: Often considered valuable due to the presence of rare or precious metals. Special methods are employed to recover these metals from the sludge for reuse or recycling.
   • Inorganic Sludge: May not always have high economic value unless it contains specific valuable minerals or metals. The focus is often on proper disposal or treatment to mitigate environmental impact.

In summary, while both types of sludge can contain valuable materials, minor metal sludge is specifically associated with the recovery and processing of rare or minor metals, whereas inorganic sludge encompasses a wider range of non-organic materials from various industrial processes.

Source：ChatGPT

Inorganic and organic sludge are two primary types of sludge produced during wastewater treatment processes. They differ significantly in their composition, properties, and disposal methods.

Inorganic Sludge

• Composition: Primarily consists of inorganic materials such as sand, grit, and metal particles.
• Sources: Wastewater from industrial processes, construction sites, and stormwater runoff.
• Properties: Typically denser, heavier, and less biodegradable than organic sludge.
• Disposal: Often disposed of in landfills or used as fill material in construction projects.

Organic Sludge

• Composition: Contains a high percentage of organic matter, including bacteria, viruses, and suspended solids.
• Sources: Domestic wastewater, food processing wastewater, and agricultural runoff.
• Properties: More biodegradable and can generate methane gas during anaerobic decomposition.
• Disposal: Can be treated through anaerobic digestion to produce biogas, composted, or landfilled.

Key Differences:

Feature	Inorganic Sludge	Organic Sludge
Composition	Inorganic materials	Organic matter
Source	Industrial, construction	Domestic, food processing
Properties	Dense, heavy, non-biodegradable	Biodegradable, generates methane
Disposal	Landfills, fill material	Anaerobic digestion, composting, landfills

In summary, inorganic sludge is primarily composed of inorganic materials and is often disposed of in landfills, while organic sludge contains a high percentage of organic matter and can be treated or composted. Understanding the differences between these two types of sludge is crucial for proper wastewater treatment and disposal.

Source：Gemini

• Material to be dry: Urban mining, Minor metal sludge
• Purpose of drying: Recycling, Reducing industrial waste cost and amount
• Moisture content: 52.2％W.B. before drying, 3.8％W.B. after drying
• Requirements for dryer: Drying is carried out inwards as the dried material is lumpy and heat does not penetrate easily into the interior. 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

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