昨年のインタビューに続き，生命理工学研究科で教員をしている古川勉寛さん，齋門良紀さんが大学院修士課程を修了した葵会仙台病院リハビリテーション科理学療法士の横田龍さん，大原綜合病院リハビリテーション科理学療法士の輔さんと共に生命理工学研究科で学んだ2年間についてインタビューをしました．

抄録全体を表示

In order to make a clear evaluation of overall energy requirement for the production system of directly reduced iron through pellet from iron ore powders, exergy analysis was applied to the two systems. The first one consists of pelletizing, firing and reduction processes (Fired pellets method) and the second one includes pellets curing process instead of firing process (Cement bonded pellets method).
Being compared with enthalpy balance, exergy analysis has two advantages in that the exergy expresses the quality of energy and evaluates different kinds of energy like chemical, thermal, pressure, mixing energies and so on by a unified measure.
As a result of exergy analysis, fired pellets lose less exergy than cement bonded pellets in the reduction process in a shaft furnace. As the overall system, however, exergy requirement in the cement bonded pellets method is about 50% of that in the fired pellets method. This marked difference is caused by the large exergy loss in the firing process. Furthermore, exergy loss in the production of cement bonded pellets will be decreased by decreasing the amount of cement added as binder.

抄録全体を表示

The effects of some foreign oxides on the rate limiting step of the reduction of pellets from wustite to metallic iron and the values of rate parameters are studied.
It is confirmed that the reduction behavior of those pellets is represented by an unreacted core model or an uniform reaction model depending on the kinds of foreign oxides and iron oxides as starting materials. The mixed rate control equation of mass transfer in the gas phase, intraparticle gas diffusion, and chemical reaction can be applied to any iron oxide containing CaO and hematite and magnetite containing Al₂O₃. On the other hand, the reduction rate of the pure iron oxides, wustite containing Al₂O₃ and any iron oxides containing MgO is controlled by the oxygen diffusion in the metallic iron shell.
These results are suggested by the conclusion of our previous studies that wustite grains are reduced nontopochemically and pellets are reduced topochemically when those complex oxides consisting of iron oxides and any foreign oxide precipitate in wustite during reduction.

抄録全体を表示

It was tried by observing partially reduced pellets microscopically and by analysing reduction rates to elucidate the mechanism for Al₂O₃ to accelerate the reduction of wustite produced from magnetite containing Al₂O₃. A macroscopical cross section view of partially reduced pellets of 50% reduction indicates that the reduction pattern is of homogeneous type except the one at 1203 K. Furthermore, the microscopical observation displays that wustite grains are covered by a dense layer of metallic iron and that the mean radius of residual wustite grains decreases with an increase in the amount of Al₂O₃. On the other hand, a graphical analysis of reduction rate shows that the rate is controlled by the diffusion of oxygen in a metallic iron layer covering wustite grain. From the above mentioned results, it is concluded that the effect of Al₂O₃ may cause the formation of the dense iron layer covering the wustite grain thoroughly, but it can accelerate the reduction by dividing a wustite grain into smaller many ones.

抄録全体を表示

Experiments have been made to study the crystallization process of free lime and magnesia from the molten LD-converter slag saturated with magnesia.
Many types of free lime exist depending on the cooling conditions and the slag basicity. In rapidly cooled slags with a basicity higher than 4, two types of free lime exist, i.e. primary lime solid solution (L_pri) and lime solid solution (L_per) as residuum which results from a peritectoid reaction between L_pri and the liquid slag. On the other hand, in slowly cooled slag, three types of free lime exist.
1) CaO rich phase (L_wus) which contains a lot of minute precipitates of white spots of wustite.
2) Lime (L_C3S) as a mixture of 2CaO·SiO₂ and lime solid solution which are formed by the decomposition of 3CaO·SiO₂.
3) Lime (L_res) which exists in the form of a string along boundaries of 2CaO·Fe₂O₃ crystals.
Free magnesia forms a solid solution with FeO or/and MnO in slag and changes into magnesio wustite (MW).
The mechanism of the formation of such various phases is discussed.

抄録全体を表示

The pore-radius distributions in the reduced iron from magnetite and wustite containing several foreign oxides were measured by the mercury penetration method, and the cross sections of the wustite grains in the partially reduced samples were observed.
The following results were obtained.
(1) Wustite grains reduced from magnetite containing Al₂O₃ are reduced nontopochemically and the micro pores are formed in the reduced iron. However, this behavior is not observed when the wustite as a starting material contains Al₂O₃.
(2) Wustite grains which are reduced from magnetite and wustite containing CaO are reduced nontopochemically and the pore radius becomes larger with increasing the quantities of CaO.
(3) Wustite grains containing MgO are reduced topochemically as in the case of pure wustite grains and the addition of MgO gives little effect to the pore-adius of reduced iron.
(4) It is concluded that those effects of Al₂O₃ and also CaO can be found when the compounds of the foreign oxides with iron oxides are precipitated in wustite during the reduction.

抄録全体を表示

エチレングリコール抽出・導電率測定法による製鋼スラグ中の遊離酸化カルシウムの迅速定量法について検討した.カルシウムと同時に抽出される鉄及びマンガンが導電率測定時に影響を与えるため,その補正方法を決定した.すなわち,抽出された金属(鉄及びマンガン)量は490nmにおける吸光度から決定できることから,これを補正法として用いて,分析法を確立した.本法による分析結果とAASによる分析結果はよく一致した.又,分析精度は2.5～3.3%(相対標準偏差)であった.

抄録全体を表示