TITLE Development of a high-efficiency dechlorination process for waste plastics and establishing the technology to convert from wet to dry blast furnace dust collectors
(Joint Program to Promote Technological Development with the Private Sectors)




Since the container and package law went into full effect in April 2000, the recycling of classified plastic waste bags mingled with polyvinyl chloride collected by local governments has became a serious problem.

In the meantime, the Japan Iron and Steel Federation has been seeking to reduce energy consumption in 2010 by 11.5 % to the 1990 level to comply with the plan for COP3. This plan includes effective use of waste plastics and improving the efficiency of the blast furnace top pressure recovery generator by converting from wet to dry blast furnace dust system.

To achieve the above target by using waste plastics, it becomes imperative to reduce chlorine content level, a highly corrosive substance in waste plastics, to as low as possible before feeding it into the furnace.

This project aims to establish:

* A highly effective dechlorinating process

* The technology to use dechlorinated waste plastics as a reducing agent for blast furnaces equipped with a dry dust collector and top pressure recovery generator

* The technology making appropriate quality coke under the condition of adding dechlorinated waste plastics to coal in the coke oven.?

The accomplishments of JSW's and SMI's research work in 2001 are:

1. The virgin polymers basic test was conducted. It was confirmed that the negative factors for the dechlorination were insufficient thermal-degrade of Poly-vinylidene chloride and generation of organic-chloride of high boiling point from polyethylene terephthalate.

2. Using dechlorination extruder, residual chlorine content was achieved below 0.1wt% on the condition of cylinder temperature 370℃ and standard input 50kg/h using waste plastics collected by local governments.

3. The field test of the dechlorinating process was conducted. It was confirmed that any significant damage by corrosion or abrasive wear was not observed in screw materials.

4. The waste plastics injection test into the t uyere of a commercial blast furnace was conducted. The combustion characteristics of waste plastics in the raceway were cleared, and it was confirmed that the stable operation was possible with dechlorinated waste plastics injection.

5. The calculation results by mathematical blast furnace model showed that the dechlorinated waste plastics could be used with no problem at the amount of 20kg/t-HM.

From the research results conducted these three years, the technology to reduce chlorine content of waste plastics collected by local governments to the level below 0.1% was established, and it was confirmed that the dechlorinated waste plastics were able to be used at blast furnace and coke oven with no problem.