Technology of flame‑induction heating of ferrous metal shavings in hot briquetting installations

Abstract

As a result of the study of flame‑induction heating of steel and cast iron shavings, optimal heating modes, dimensions of the furnace and the ratio of the sizes of its components (gas‑flame and induction heaters) were established, which served as the basis for the development of a new heating technology, which ensures minimization of dimensions in comparison with known analogues, increasing the productivity and efficiency of the furnace. It has been established that at the stage of evaporation and removal of water vapor and light oil fractions from the chips in the temperature range of 100–550 °C until the optimal oil concentration of 1.5–3.0 % is achieved, among all known methods of muffle heating, gas‑flame heating is the most economical and productive heating, and subsequently, when heating a dehydrated porous mass of metal with a density of 1100–1700 kg/m3 to 850 °C – induction heating in an atmosphere of products of thermal sublimation and destruction of coolant. It is advisable to carry out induction heating with a current frequency of 2.0–2.4 kHz with a ratio of the lengths of the gas‑flame and induction heating zones of 2.0–2.5 and the dimensions of the inductor (height to hole diameter) of 3.7–4.0. The degree of oxidation of hot‑pressed briquettes corresponds to the initial oxygen content in the chips: for steel – 1.3–1.7 %, for cast iron – 0.46–0.47 %. The data obtained made it possible to develop a technology for flame‑induction heating of ferrous metal shavings, as well as the design of a small‑sized furnace with a specific productivity of 6500–9500 kg/m2·h and an efficiency of 40–45 %.