Japanese carbonizing furnace 2002-02(96)

 

Introduction

In recent years, waste incineration regulations have become increasingly strict, including revisions to laws such as the Law Concerning Special Measures against Dioxin and the Waste Disposal and Public Cleansing Law. Simultaneously, various recycling laws have been enacted to realize a resource-recycling society. The cost of waste disposal has skyrocketed due to the tightening of final disposal sites, leading to a strong demand for shifting from incineration and landfill to recycling.

In line with this trend, there is an emerging need for alternative recycling methods for organic wastes (construction waste wood, food waste, sewage sludge, livestock manure, etc.), which were previously disposed of in landfills after intermediate treatments like dehydration, drying, and incineration. One such method, carbonization, is gaining attention.

Current Status and Direction of Carbonization Furnace Development

Charcoal production is a typical example of carbonization. Traditional charcoal-making techniques (e.g., Tsuki Kiln and Proc Furnace) and industrial mass production methods such as flat furnaces, screw furnaces, rotary kilns, and fluidized bed furnaces have been used. However, while conventional technologies can handle materials like thinned wood and sawmill waste with low dioxin countermeasures, using carbonization equipment as an alternative to waste incineration presents unavoidable dioxin problems.

For recycling purposes, carbonization equipment must produce high-quality carbonized material at low cost without generating dioxin. This requires the furnace to be sealed and oxygen-free (or low oxygen) to suppress dioxin formation while allowing high-temperature steaming. The materials must be stirred to ensure homogeneous carbonization.

The rotary kiln is the most widely used carbonization equipment that meets these requirements. In the rotary kiln method, materials are placed in a rotating cylindrical furnace and carbonized by internal or external heat. One drawback of rotary kilns is that the residual material (carbide) must be post-combusted in a stoker until it is completely reduced to ash. However, this is also an advantage as the carbonization process converts organic content into combustible dry distillation gas, providing the necessary heat for carbonization and saving fuel.

Advantages and Marketability of Carbonization

The advantages of the carbonization process include:

1. Fuel Efficiency: The organic content in the raw material is converted into combustible gas, which provides the heat necessary for carbonization, thus saving fuel.
2. Simple Structure: The furnace has a simple structure with no mechanical parts, minimizing breakdowns.
3. Cost-Effective: Although advanced sealing technology is required, the lack of a dioxin removal system and stoker makes it superior in terms of installation space and equipment cost.
4. Even Carbonization: The raw materials are evenly carbonized due to the rotation of the kiln.

The basic technology in this field has already been established, leading many companies, from major machinery manufacturers to small and medium-sized enterprises and ventures, to enter the carbonization equipment market. Equipment ranging from 10 kilograms per day to several tens of tons per day has been developed. This section looks at examples of carbonization processes for various organic wastes and their marketability.

Expanding Charcoal Market

The expanding range of uses for charcoal is one major reason why carbonization is attracting attention. Charcoal's excellent functionality as a material—such as its ability to absorb odorous substances and pollutants, improve soil quality, and adsorb volatile organic compounds—has driven new demand. This has led to increased production and the use of charcoal for non-fuel purposes like soil conditioners, humidity regulators, and activated carbon.

Carbonization of Construction Waste Wood

Construction waste wood represents a significant business opportunity in the carbonization market. The full enforcement of the Construction Materials Recycling Law in May 2002 will provide a tailwind for this sector. The carbonization process for construction waste wood can transform it into valuable products, making it a promising area for recycling innovation.

Conclusion

Carbonization offers a new direction for recycling organic wastes. The development and market expansion of carbonization technology are expected to reduce waste disposal costs and promote recycling. The high commercial value of carbonized products, especially from construction waste wood, food waste, sewage sludge, and livestock manure, supports the establishment of a viable recycling business. Future advancements in carbonization technology and its applications will further enhance waste management and resource recycling.