Single batch extractions were performed on municipal waste incinerator fly ash. The effects of stirring speed, solid to liquid ratio, contact time, pH and the type of acid which was added to maintain pH constant during extraction on the amounts of heavy metals released from fly ash were investigated. It was confirmed that the extraction conditions which were defined in the Availability Test (NVN 2508) gave the maximum release of cadmium, copper and zinc. These conditions, however, were not aggressive enough to obtain the maximum release of iron, manganese and lead. The release of manganese was limited by pH and the release of iron was limited by pH and contact time. Acetic acid was more suitable pH controlling chemical than hydrochloric acid in evaluating the release of lead.

View full abstract

Characteristics of continuous analyzers for SO₂ in flue gas (SO₂ analyzers) were investigated in municipal incinerators.The investigated SO₂ analyzers were the non-iispersive infrared absorption (NDIR) type and ultraviolet absorption (UV) type.
The reasons for the difference between the observed values of the SO₂ analyzers by NDIR and UV were thought to be the influence of coexistent CO₂ and H₂O condensation efficiency.The reasons why the observed values of the SO₂ analyzer by NDIR were different from the precipitation titration method in the range of about-5 ppm and+4 ppm, were thought to be as follows: the influence in CO₂, the difference in H₂O condensation efficiency, the difference of measured species in the two methods, and absorption loss of SO₂ into the condensed water.Especially, it may be very influential that not only SO₂ but also SO₃ is measured by the precipitation titration method.The reasons why the observed values of the S0₂ analyzer by UV were about 4 ppm smaller than the observed values of the precipitation method were thought to be as follows: the difference of measured species in the two methods, and absorption loss of SO₂ into the condensed water.

View full abstract

Energy analysis was done for the RDF production and utilization system in Sapporo. The analysis covered the whole range of the system: from refuse collection to landfilling of residue.Excluding minor parameters in calculation with a sensitivity analysis, the authors'energy calculating procedure can be easily applied to other systems.The RDF system can produce larger net energy output than input energy requirements, although it consumes much energy to produce RDF.In terms of the energy yield, the ratio of the net energy output to the calorific value of the refuse input, the RDF system is comparable to the Atsubetsu refuse incinerator, which has the highest energy recovery rate in Japan.

View full abstract

For a municipal solid waste incinerator, it is crucial to establish design and operation methods to perform complete combustion of flue gas, which is essential for reducing the generation of micro-pollutants such as dioxins. Accordingly, influential factors and degree of effect on gaseous combustion need to be identified. However, the individual effect of each factor is hardly ever evaluated because actual waste combustion is composed of extremely complicated phenomena occurring simultaneously: drying, gaseous combustion and solid combustion of waste whose characteristics also vary considerably with time. The purpose of this work, therefore, is to recognize the degree of effect of each factor influencing gaseous combustion by using bench-scale test equipment modeling the secondary combustion chamber of an actual incinerator. Carbon monoxide (CO) gas, considered an indicator for complete combustion, is employed as unburned gas for the tests. The variation of CO concentration is measured under various combustion conditions including temperature, O₂ concentration and retention time. Then, the Arrhenius-type rate equation of CO is obtained from the measured data by determining the parameters of the equation. In addition, by applying the rate equation to an actual incinerator, the combustion conditions are evaluated.

View full abstract