What Is Refuse-Derived Fuel?

Refuse Derived Fuel (RDF) is a fuel made by crushing, sorting, drying, adding medicaments, and compression molding to combustible garbage.

Chinese name: Refuse Derived Fuel / Solid Solid Fuel

Foreign name: RefuseDerivedFuel
Short name: RDF

Characteristics of garbage derived fuel

RDF fuel is characterized by uniform size and uniform heating value. The molding process can increase the heating value of the waste by about 4 times, and is easy to transport and store. It can be stored at room temperature for 6 to 10 months without decay. Therefore, a part of the garbage can be temporarily stored to solve the problem of disposal capacity in the peak period of garbage production due to the shutdown of boiler technology or the peak season. Adding additives in the RDF molding process can achieve the purpose of removing SO ₂ and HCl in the furnace and reducing the emission of dioxins. Therefore, the obtained RDF fuel has the characteristics of high calorific value, stable combustion, easy transportation, easy storage, low secondary pollution, and low emissions of dioxins. This fuel can be burned separately as the main raw material, or it can be mixed with coal and fuel oil according to the boiler process requirements ^[1] .

Waste Derived Fuel Classification

The American Inspection and Materials Association (ASTM) divides RDF into 7 categories according to the degree of processing, shape, and use of municipal solid waste-derived fuel. In the United States, RDF generally refers to RDF22 and RDF23, Switzerland, Japan and other countries. RDF is generally RDF25, its shape is (10-20) × (20-80) mm cylindrical, and its calorific value is 14600-21000kJ / kg.

Preparation of refuse derived fuel

After the garbage enters the yard, it is pretreated by broken bags and a magnetic separation, etc., removing incombustible materials such as metal, glass, sand and so on, and putting combustible materials (such as plastic, fiber, rubber, wood, food waste, etc.) in the garbage into a crusher After being broken into easy-to-dry granules, it enters the dryer through the conveyor and is automatically rolled down in the dryer. The hot air passes through the upper part of the dryer to prevent the material from catching fire due to direct contact with the hot air. By controlling the hot air to adjust the moisture content, the moisture content of the material is reduced to below 8%. The dried flue gas is discharged through the dust collector, and the dried material is sent to the wind separator after secondary magnetic separation and aluminum separation. After removing incombustible materials (lime, broken glass, metal shavings, etc.), it is sent to the secondary Crusher, which crushes the material to easy-to-form small particles, adds a certain amount of sulfur-fixing, chlorine-fixing and preservatives and sends it to the molding machine ^[2] . The molding machine continuously produces RDF, and after cooling, it is sent to the finished product hopper through a vibrating screen and bagged by an automatic weighing machine. The process flow is shown in the figure.

Figure Waste Derived Fuel Process Diagram

Composition of refuse derived fuel

The nature of RDF varies with regions, lifestyles, and levels of economic development. The material composition of RDF is generally: paper 68.10%,

Plastic film 15.0%, hard plastic 2.0%, non-ferrous metals 0.8%, glass 0.1%, wood, rubber 4.0%, and other materials 10.10% [7].

Waste-derived fuel applications

RDF is a solid waste treatment method developed by foreign developed countries. RDF fuel has been widely used in Japan, South Korea and other countries for power generation or heating.

Developed countries attach great importance to RDF technology, which has continuously expanded its application scope. In addition to RDF can be used for power generation, there are many other fields of application, currently the main applications are in the following areas:

(1) Small and medium public places. The application of RDF in public places mainly refers to warm water swimming pools, gyms, hospitals, public baths, welfare homes for the elderly, melting snow, etc.

(2) Drying project. RDF is burned in a special boiler and used as a heat source in drying and thermal deodorization. At present in Japan, the application of RDF in drying projects generally accounts for 1/4 to 1/3 of the total.

(3) District heating project. In areas where the heating T-process infrastructure is relatively complete, only a dedicated RDF combustion boiler can be built to achieve RDF heating, with less investment. But the foundation of heating engineering is relatively backward

Due to the high cost of heating, RDF heating is not economical.

(4) Power generation project. In a combustion power plant, RDF and coal are mixed for power generation, which has a very economical advantage. Small-scale combustion power generation in special RDF combustion boilers has also developed rapidly. 13 The government has been studying RDF combustion power generation schemes since the mid-1990s. At present, local governments such as Hokkaido, Tochigi, Gunma, Mie, Shiga, Kochi, Ishikawa, and Fukuoka are highly motivated. And has invested in the construction of RDF combustion power plants ^[3] .

(5) Application as a carbide. The RDF is pyrolyzed and carbonized under the condition of air insulation, and the obtained combustible gas is burned as a heat source for the drying process. The pyrolysis residue is the carbide, which can be used as a reducing agent in the ironmaking blast furnace instead of coke.