低炭素高炉操業の課題: 滴下帯の通気性に影響を及ぼすスラグ融体物性

摘要

Currently, low reducing agent operation of blast furnace is actively investigated in order to reduce CO_2 emission. However, low reducing agent operation accelerates coke wear, resulting in the decrease in the void fraction in the blast furnace. Particularly, at the dripping zone, the decrement in the void fraction increases the hold-up amount of liquid burden. As a consequence, the gas permeability at the dripping zone becomes lower dramatically. In the present paper, we have focused on the effect of thermophysical properties of molten slags on the gas pressure drop and the liquid hold-up, the measures of the gas permeability, in the counter-current region of gas-liquid flow. It has been considered from the results of hold-up experiments and/or simulations that the surface tensions of molten slags and their contact angles against carbonaceous materials are the most significant properties for the gas pressure drop as well as the liquid hold-up. The previous studies with respect to their properties have been reviewed for the slag compositions and the temperatures close to those at the dripping zone.%鉄鋼業から排出されるCO_2の削減が課題となっており，フエロコークス, COURSE50等のナショナルプロジェクトを通して多くの研究開発が実施されている。これらの研究開発では，低還元材比，低炭素•低コークス製鉄を最終目標とし，新しい高炉原料の追求，その利用方法といった製銑プロセス全体系の見直しがなされている。しかし，現在提案されている熱保存帯の低温化，還元材の水素化は，炉内反応に大幅な変化をもたらし，低コークス化は高炉内の通気性に甚大な影響を与え得る。