High temperature gasifying and direct melting technology of solid waste
T.Matsudaira(JFE Engineering Corporation), S. Nakamura(JFE Engineering Corporation)@Y. Suzuki(JFE Engineering Corporation)

In Japan, a little over 70 percent of general solid waste is incinerated, and therefore there are problems such as discharge of highly toxic substances including dioxins generated during incineration, treatment of ash remaining after incineration, and others.  In 1992, we started to develop next generation waste treatment technology which can treat various kinds of solid wastes without an external environmental impact and also can recover energy with high efficiency.

As shown in Figure 1, the furnace is divided into three zones. In zone 1, which is filled with coke, coke and fixed carbon in solid waste are burned by oxygen-rich air sent through main tuyeres.  By combustion heat, non-combustibles in waste is melted, and the molten non-combustibles are discharged through an extracting port at the furnace bottom while keeping a molten state at about 1800K in a reducing atmosphere.  CO2 produced by combustion is reduced to CO by a solution loss reaction, and CO flows into the upper zone 2.   In zone 2, the gas temperature is adjusted to about 900K by partial burning of the product gas using air sent through sub tuyeres while this zone maintaining a partially fluidized state.  By this heat, solid waste discharged from the furnace top is preheated and thermally decomposed.  In zone 3, some of the product gas is burned under a high temperature reducing atmosphere above 1100K on average by air sent through tertiary tuyeres.  The combustion gas is subjected to gas treatment such as pyrolysis of tar and production restraint of dioxin by the stay for two seconds and longer at the high temperature, being converted into combustible gases that are easy to handle, and discharged to a secondary combustion furnace.

We had received the first order for a commercial plant in May 2000.  It was followed by further orders from six citys.  At present, more than 600 tons of waste are treated of daily in these plants.  Photo 1 shows a plant in Kakamigahara City of Gifu Prefecture with a capacity of 192 tons/day.  

Photo 1 :  Kagamigahara Plant in Gifu Prefecture

NKK and Kawasaki Steel established JFE on Sept. 27, 2002.  We will promote aggressive R&D activities in order to create a new environmental technology.


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