Establishment of Recycling System of Incinerated Ashes produced from Paper Garbage and Paper

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Incineration conditions as well as milling conditions of the incinerated ash prepared from paper sludge were investigated in detail in order to establish recycling system of inorganic compounds in paper sludge, because most of these inorganic compounds originate from paper fillers, which are added to paper stock to increase opacity and brightness of paper produced. The results show that paper sludge ash obtained by incineration at 800℃ for 1 h followed by ball-milling in water can be used as recycled paper fillers. Distribution of elements in the incinerated ash particles was analyzed by using a scanning electron microscope attached with an X-ray dispersive analyzer. Calcium carbonate, magnesium carbonate and kaolin clay present in the paper sludge are converted to gellenite by fusion during incineration at the temperature below 600℃. Elementary analysis of garbage-incinerated ash sampled in garbage-incineration centers in Tokyo metropolitan areas showed that calcium, silicate and aluminum are the predominant components, which suggested that these elements originated from paper fillers. These garbage-incinerated ash samples, however, contained water-soluble fraction in the range of 5-20%. Low-crystalline compounds having similar X-ray diffraction patterns were obtained from the garbage-incinerated ash samples by boiling-water extraction. It was impossible so far to improve brightness of paper sludge incinerated ash to more than 70% even by various trials.The paper sludge incinerated ash was added to paper stock up to 40% to evaluate properties of handsheets containing the ash as fillers. Reduction of tensile index could be restricted by using a dry-strength additive such as anionic PAM. Although brightness of the handsheets decreased with the ash addition, remarkable improvement of opacity was achieved by the ash addition.