壓延工場に於ける加熱爐の熱能率と鋼片の大小に據る損得比較其他に就て

Abstract

As an example of reheating furnace of billets, a furnace for wire rod mill was taken as the subject for the present investigation. The writer measured the temperature of billets heated in the furnace and of the waste gas passing through the flue. He theoretically calculated the beat efficiency, the size of billet and the ra'e of heating, which he compared with the results of the present experiment in order to find out the difference in heat efficiency & etc. due to the size of billets.Summary of Conclusions.1. The temperature in the furnace gradually decreases from the fire-grate to the flue; being on average 1, 230°C at the fire-grate and 474°C at the flue (Figs. 1-3).2. The fall of temperature due to bad combustion practice is sensibly large at the part of higher temperature near the fire-grate, but does not affect so much at the other parts of the furnace (Fig. 2).3. The average surface temperature of the heated billets taken out of the furnace was 1, 226°C, every billet having been kept heating in the furnace for about 56 minutes and a half (Tab. 1-2).4. The heat capacity of the heating furnace to be contained at its stationary state is equivalent to 2.32 Kgr. tons of coal, which being equal to about 53 per cent of the fuel fired in the furnace to obtain the same state.5. The loss of heat due to radiation and conduction & etc. is about 13.1 per cent of the total amount of fuel fired.6. The heat which was carried out by billet is about 22.68 per cent of the total fuel.7. The heat to be carried away by ashes is about 1.13 per cent of the total fuel used.8. The heat which was carried away by the waste gas through the flue amounts to about 56.5 per cent of the total heat evolved by the fuel fired.9. From the equation of heat conduction, the relation between the thickness of the billet and the heating time was calculated; the results shows that the increase of the heating time was proportional to the square of depth (Figs. 8-9).10. Of two kinds of billets of sizes respectively 9.6×9.6×102.0cm. and (9.6×2)×(9.6×2) ×102.0cm., when heated in the furnace under the same condition, the former required 0.127 tons of coal per ton of billet and the latter 0238 tons of coal, the heat efficiencies of both being respectively 22.68 per cent and 12.20 per cent. It was found by calculation that the increase in depth caused the increase of coal used, but on the contrary, the heat efficiency diminished (Figs. 10-11).11. In billets of the above sizes, it was found that when they were charged in the furhace kept at 1, 240°C, the former required 22 minutes to reach 1, 000°C at the centre, while the latter, an hour and 32 minutes to reach the same temperature at the same point.12. Six kinds of specimens of cube and four kinds of billets were charged in the furnace kept at 900°C in order to observe the time taken by the temperature of the surface and that at the centre of the specimen to feach 900°C (Figs. 12-15).13. The fact that the increase in thickness of a billet caused the increase of heating time in proportion to the square of it was experimentally ascertained. If x be the thickness of plate, or a side of cube or the cross section of billet, and t be the time taken by the temperatures of the respective specimens to reach the same height at their centres, then. x2=at (Fig. 16).