Melting Treatment of Incineration Ash

Abstract

In Japan, mainstream municipal waste processing is by incineration, and this has been established from the viewpoint that it offers stable, sanitary processing for large quantities and that it enables a great reduction in the ultimate disposal volume.However, the annual volume of municipal waste has a tendency to increase year by year.With the decreasing capacity of ultimate disposal sites, further reduction for volume of incineration ash both in municipal solid waste (MSW) and sewage sludge is required.In addition, secondary pollution by the harmful components of heavy metals or dioxins eluded from landslide ash is feared, and the inactive and stabilization of incineration ash has become an increasingly important issue.The melting and solidification process, in which ash is heated up to a temperature higher than the fusion point and melted, then cooled to solidify and recovered as slag, is considered an effective technique that will meet the expectations mentioned above.And, several processes that differ from heat source for ash melting for each other have been appeared in these days, and are divided into two groups equipped with combustion devices or electrical heated up devices.Reported in this paper are the characteristics of typical incineration ash first.And next, ash melting performance, such as behavior of heavy metals contained in ash, the characteristics of the melt and solidification slag for sample ashes taken from different types of incineration are described.These report are based on operation of our established two types of melting furnace, “swirling flow melting furnace” and “plasma melting furnace”. The first one is included in combustion melting methods, and other is in electrical melting methods.Both processes enable the melting furnace to melt a fly ash individually that contains harmful components.As a swirling flow melting furnace, we have operated commercial plants, with the maximum capacity of 120ton/day.On the other, we have operated commercial plant of plasma melting furnace with the capacity of 5ton/day.This commercial plant has the advantage to enables the plasma furnace to melt fly ash of the fluidized-bed incinerator individually.Based on the performance of these plants, we are now going to optimize the design for more large size melting furnace with stable operation.