Sakae Yagi

Fluidized-solids reactors with continuous solids feed—I: Residence time of particles in fluidized beds

The distribution of residence times of solid particles is examined in fluidized beds at steady state with continuous feed and discharge of solids, both for beds consisting of a single particle size and for beds consisting of a wide spectrum of particle sizes. The mean age (residence time in bed) of particles of a given size in the overflow and carryover streams is found in all cases to be given by where F1 is the mass flow rate of overflow stream, W is the weight of solids in the bed, ψ is the ratio of the size distribution function of overflow particles to that within the bed and ϰ is the elutriation velocity constant of particles whose mean age is being considered. The constant ψ is a measure of the degree of vertical segregation of particles within the bed. In most practical situation the bed may be considered to be not segregated, in which case ψ can be taken to be unity. For significant carryover of solids the elutriation velocity constant κ controls in determining the average length of stay of particles in the fluidized bed. In all cases the mean age of particles of a given size is the same in both the overflow and carryover streams.

Fluidized-solids reactors with continuous solids feed—II: Conversion for overflow and carryover particles

Abstract Based upon the simple model of particles which keep their diameters almost constant during reaction with the gas flowing in the fluidized bed, and applying the exit age-distribution functions obtained in Part I, equations for the conversion of product particles were derived. For chemical reaction controlling: For gas diffusion through solid phase controlling: where y is the conversion of particles of diameter x , φ is the ratio of time required for complete conversion of one particle of diameter x to the average residence time of the particle. The above equations are applicable to both overflow and carryover particles, hence the conversion for overflow particles must be equal to that for carryover particles for a given particle size. The mean value of the conversion y can be given as follows: for overflow stream for carryover stream where K 1 ( x ) and K 2 ( x ) represent the size frequency distribution functions for the overflow and carryover particles respectively.

The absorption of oxygen into sodium sulphite solution

Abstract In this work the kinetics of the absorption of oxygen by sulphite solution have been investigated, for which many diverse mechanisms have been proposed. For this end the oxidation reaction of sulphite with oxygen in liquid phase was first investigated by a polarographic method. From the experiments it was found that the reaction was first order with respect to both oxygen and sulphite concentration, and that the promoting effect of cobaltous catalyst was proportional to its concentration. The reaction rate constant was obtained at 20°C. Using these results the mechanism of oxygen gas absorption from bubbles into sulphite solution could be determined. The results of experiments agreed roughly with the theoretical prediction and it was shown that in the presence of cobaltous catalyst the absorption process was determined by the second-order reaction with sulphite in the liquid film.

Fluidized-solids reactors with continuous solids feed—III: Conversion in experimental fluidized-solids reactors

Abstract Experimental data from gas-solid fluidized reactor systems are analysed on the basis of the theoretical treatment of Parts I and II. The following systems are treated: 1. Roasting of pyrrhotite and zinc blende particles with uniform size. 2. Roasting of zinc blende concentrate with wide distribution of size. 3. Distillation of sulphur with two-stage fluidized reactor. 4. Nitrogenation of calcium carbide. Close agreement between theory and experiment is obtained.

Experimental Studies on Continuous Stirred Tank Reactor Models

径4cmのタービンで撹拌する内径11.5cmの流系撹拌槽の2次反応を伴う時, および無反応の時の入口濃度変化に対する過渡応答を求める実験を行なった。結果は1次近似としては完全混合, 2次近似としては1循環流を有する循環モデルにて表わすことができた。循環モデルの設定に必要な種々の量を測定し, 過去の研究と比較してほぼ妥当な結果を得た。

Optimization of Two Consecutive Reactions with a Parallel Reaction as an Application of Maximum Principle

併発反応を伴う逐次反応系において,反応物の転化率に対する中間生成物の収率を最大にすることを目的として,最適温度制御を求めた。反応の例としては, エチレンの酸化反応を取り上げ, 反応速度式は, 加納・金塚の提案したものを用い,温度の上限は300℃,下限は200℃として,Pontryaginの最大原理によって計算した。その結果,最適温度制御,および,その時のエチレン,エチレンオキシドの量は,図1に示すようなものになった。図2では,250℃,280℃ で等温操作を行なった場合と,最適制御を行なった場合との,エチレンの転化率に対するエチレンオキシドの収率を比較した。図3には,同じく,選択率を比較した。計算には,OKITAC 5090を用い,演算時間9分を要した。

Heat Transfer in a Reacting System

均相瞬間反応系であるN2O4-NO2ガスを円管内に流し, 壁における境膜伝熱係数, 温度および流速分布を測定した。平均のNu数は物性値を平均のエンタルピにおける値を用いると, Colburnの式で整理することができ, その係数は0.023であった。エンタルピーを推進力にとり, 反応による密度と粘度の変化を考慮して, Deisslerのアナロジーを適用して流速分布とエンタルピー分布を求め, 実験値と比較した。

A Study of the Chlorination Velocity of Titan Slag

In order to design an apparatus for chlorinating titan slag, we must be informed of the following three fundamental data: -the reaction velocity constant (γkc), the diffusion constant (Dvs) of Cl2 in the ash, and mass transfer coefficient (kf) of Cl2 in the gas film on the spherically formed sample, composed of coke and slag.vs< During the chlorination of the titan slag at high temperature, the weight loss of the tabletted cylindrical solid sample, composed of coke and slag, was measured by means of a thermobalance. In these experiments, variables of reaction conditions were found to be temperature, velocity of Cl2 gas, mixing ratio of coke and slag and diameter of coke particles and slag particles.From these experimental results, we can calculate the above mentioned three fundamental data (γkc, Dvs, kf).In the first place, dW/dt and W can be known from the weight loss of the sample and the time of reaction t. α and β can be obtained by means of Eq. 7, and Dvs and by means Eqs. 8, 9 and 10.To know γkc, kf should be calculated independently of γkc. In order to obtain the value of kf, the modified equation for the mass transfer in a single sphere reported by Frosessling (Eq. 19) can be resorted to.The three fundamental data thus obtained are given in the form of Eqs. 26, 16 and 19. Much useful information for the practical design and operation of an apparatus may be got by their application.(1) The time required for the complete reaction of a spherically formed sample composed of coke and slag with Cl2……θ0 (Eq. 28 and 27).(2) The capacity of the apparatus.(3) The utility of Cl2 in the fixed-bed type appratus.In this report calculated value of θ0 is employed.

Wall-Film Mass Transfer Coefficients of Fixed Beds

In order to explore the film coefficient of a fluid adjacent to the inside wall of fixed beds, data were obtained on the rate of dissolution of β-naphthol, by passing water through the beds whose inside was coated with the same material.Glass beads and sand were used as packings. The experimental range of the modified Reynolds number was from 1 to 2, 000, and the Schmidt number, from 1, 000 to 1, 700.Table 1 presents the dimensions of the various solid particles and of tubes used in this work. Solution was analyzed by means of a spectrophotometer.As the result, it was made clear that under the conditions employed in this investigation, the eddy diffusion in the radial direction had little effect on the coefficients of the wall-film transfer.The experimental data and calculated results for typical runs are presented in Table 2.Fig. 3 shows a summary of the wall-film coefficients, where Sh/Sc1/3 is plotted versus Rep.In this plot the properties of the particles do not appear as a parameter. The following correlations are obtained from the lines drawn in Fig. 3.Sh=0.60Sc1/3Rep1/2 Rep 40

Studies on Vertical Pipe Reactor (II)

垂直管内における,気体-液体混相流動の過程を化学工学的諸操作に利用せんとする,新らしい型式の反應裝置の基礎的研究として,まず気液混相の流動についての実驗を行つた。内径10.25mm,の垂直ガラス管内に,水および物性の異る3種の油を,おのおの空気と混合上昇させ,この場合に起る種々な流動状態を観察すると同時に,Hold-upを測定し,若干の相関を行つた結果,これらについての実驗式を得たのでこゝに報告する。