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Show mterrupting the operation. In order to maintain a continuous operation, a magnetic separator was added, a bypass was provided and an oxygen-enriched burner (27% Oz) was adopted. In spite of all these, an explosion occurred in the water-sealed conveyer, and the low-boiling-point metals such as lead, cadmium and zinc and salts in the bottom ash evaporated into gas, and when the gas was cooled, adhered to the inside of the tubular air preheater. This plugged up the steel tubes very quickly, requiring replacement. 2 . 3 Saitama-East No.l Incinerator free-standing continuous operation furnace Plate type air preheater was installed, and mechanical scraper was adopted for removing dust adhesion. It could not, however, prevent blockage, as the area was within the temperature zone where volatile matters turned to dust. Hence, heat radiator was installed in front of the gas cooler within 700 ° C range, but it caused high temperature erosion. The fuel usage: 510^ /ton ash From the above experiences, we have drawn the following conclusion: (1) A free-standing melting furnace is preferable. (2) Bottom ash must be dry. (3) Metals should be removed by magnetic separators. (4) Clinker must be pulverized, and the ash particle size must be controlled. (5) Radiant-type air pre-heater should be used. 3 . The improvement of Surface-melt furnace 3 .1 The outline and schematics of our surface-melt furnace Figure 1 depicts the transition of our furnace structures. The first model, ca. 1977, was finalized after testing a 12t/24h test furnace. A s we went through several installations, studies were done on the design, and culminated in the second model built during 1977-1992 period. This second model had much better capability of continuous operation, but was a fuel hog. For reducingmelting fuel unit and enlargingthe furnace size, w e have designed a third version which incorporate two furnaces of previous design, face to face, with twin bumers(1993 model). Slag tap opening was made smaller for reducing heat loss from the furnace. 4 |
