Kinjiro Fujii

Preparation of Porous Magnesia Grains by Use of Acetic Acid Droplets

マグネシアの多泡粒またはペレットは, マグネシアと酢酸との発熱反応による沸騰-固化の現象を利用して調製することができる. 実験用の装置として, マグネシア粉末層の環状ベッドを載せた回転皿を用い, 移動ベッドの表面を140°-180℃に加熱し, そこに酢酸液滴を散布してマグネシアと反応させ, 生成する多泡粒をスクレーパーによってベッドから掻き取る. 加熱用に用いたシュバンクバーナからマグネシア粉末ベッドへの複合伝熱係数は30.8kcal/(m2・h・℃) であった. スプレーノズルから散布される液滴は直径0.5-5mmの間で粒度分布をもつような多泡粒に変化し, また造粒容量は回転ベッド1平方メートル当たり約0.3kgであった. スクレーパーは振動ふるい形式のもので, ベッド層から選択的に多泡粒を分離した. ベッドの表面温度180℃で運転した場合の酢酸の損失は, 全使用量の28%で, 本法のプロセス化を考慮して, 蒸発損失する酢酸分の回収にも言及した.

Influence of Atmosphere on the Bloating of Artificial Light Weight Aggregate from Fly Ash and Pulp Waste Liquor

The cylindrical compacts of fly ash, pulp waste liquor being used as a binder were heated at a temperature between 1000°C and 1300°C in an atmosphere of O2, N2, CO2, CO2 (+2 vol% O2) and CO2 (+4 vol% O2), then subjected to chemical analysis, especially on carbon content and iron valency, and also measurement of magnetic susceptibility, apparent density, water absorption and compressive strength. As a result, there were seen remarkable influences of atmosphere on the sintering and bloating characteristics of the compacts, that is, 1) in oxygen, bloating began to occur at about 1200°C, where no carbon was found to remain, and therefore, the thermal decomposition of ferric oxide to release oxygen gas might lead to bloating, 2) carbon dioxide atmosphere facilitate sintering of the compact and bloating was effected by the reaction of ferric oxide with carbon at a temperature above 1100°C, where the favourable mole ratio of Fe2O3/C for bloating was likely to be from 1/1 to 5/1 and 3) there occured no bloating in N2 and CO atmosphere and substantial amount of carbon was found to remain and thereby about half of iron content was reduced to metal.In addition, the compressive strength (S) of the specimen after heating at a temperature (T) in sintering stage prior to bloating was examined, and In S∝ 1/T relation could virtually be verified, the discussion being made for this relation in view of the sintering mechanism based on viscous flow.

Reactions Between Sodium Silicate Solution and Sodium Fluosilicate

A proposed method of determininig free Na2O in the hardened bodies made from sodium silicate solution and Na2SiF6 is described, in which samples containing not more than 2mg of Na2O are ground in an agate mortar with 5ml isopropyl alcohol, poured into 100ml beaker using 50ml of said alcohol, therein mixed with 20ml of 0.25N HCl solution saturated with BaCl2 for 3 minutes, then the whole mixtures are titrated with 0.3N NaOH solution until the colour of mixed indicator of dimethyl yellow and methylen blue changes from blue-violet to clear green.Using this method, the reaction processes occuring in the mixtures of Na2SiF6 and the sodium silicate solutions having molar ratio of SiO2/Na2O ranging 2.8 to 3.5 and the solid content ranging 14% to 38% were studied with the following results:The reaction proceeds with the rate of first order, whose constant, k, varying with the solid content of sodium silicate solutions employed, may expressed as k=k′e -βC0t and leads to an equation-ln(1-x)=k′e-βC0twhere x is the fraction converted, c0 is the solid content of sodium silicate solution, t is the time in hour after mixing, and k′, β are constants.The reaction obeys the Arrhenius equation in which the mean activations energy was caluculated to be 7.87 kcal/mol in the range of 10°C to 40°C.The reaction stops eventually at about 80% conversion, irrespective of the measure of rates, which may be attributed to the thorough coagulation of sodium silicate in the hardened bodies by the salt effect of NaF produced.

On the Free Lime in Portland Cement

1) 粘土等の調合原料が, 石灰石と焼成反応する際, 石灰が球状にして, 粘土等に密に囲繞されている。且つ, 反応層の厚さが石灰粒子の大きさに無関係であるとの仮定のもとに, 指数法則に従ふ粒度分布をもつ石灰の未反応率と反応層の厚さとの関係, 並びに未反応石灰の粒度分布を算出した。2) 遊離石灰が焼過ぎに基く場合を, 4成分平衡図の上で考察を試みた。3) 市販セメント5種願につき分粒し, 各粒分中の遊離石灰を測定して累積曲線で表わした。この曲線の形状は, 1-5μの粒径の遊離石灰が, セメント粒子中に一様に分布し, そのうちセメント粒子表面に露出しているような, および単体分離しているような遊離石灰の示しうる累積曲線と見掛け上近似する。セメント中の遊離石灰全量の65-75%は, 15μ以下のセメント粒分に聚つている。且つ, セメント粒子中に内包されている遊離石灰は, 遊離石灰全量の10%を越えない。