Kazuo Endoh

Some flow characteristics of a vertical liquid jet system having downcomers

Abstract The flow characteristics and performance of a vertical liquid jet system having downcomers in an air-water system have been studied in relation to those having no downcomer. In order to obtain the basic data which are necessary for comparing the characteristics between the two systems with and without the downcomer, flow characteristics such as the bubble penetration depth and the gas entrainment rate which change depending on variables such as the nozzle diameter, the jet velocity and the nozzle height were first investigated experimentally. After evaluating the effects of these operating variables on such flow characteristics, empirical equations which may be used to predict the bubble penetration depth and the gas entrainment rate over the range of conditions tested in this ordinary liquid jet system were obtained. For the jet system having the downcomer, the effects of operating variables such as the nozzle diameter, the jet velocity, the downcomer diameter and height, etc. on the flow behaviour or on flow characteristics such as the bubble penetration depth, the gas entrainment rate, the gas holdup, etc. were then investigated, and the empirical correlations useful for predicting the boundary of flow regions, the gas entrainment rate, the gas holdup, etc. in this downcomer device were also presented. Furthermore, a comparison of flow characteristics such as the bubble penetration depth and the gas entrainment rate, which are the factors of importance as indices to evaluate the performance of plunging jet systems, between the two liquid jet systems with and without the downcomer was carried out, based on the results obtained above. As a result, it was ascertained that inserting a downcomer of small size in the gas entrainment region has the effect of markedly increasing the penetration depth of the entrained bubbles compared to that under corresponding conditions in the ordinary liquid jet system having no downcomer without any anxiety over a decrease in performance of gas entrainment and it also produces a much longer gas-liquid contacting section.

Development of fluidized-bed pyrolysis of waste tires

Abstract The problem of waste tire disposal has become critical in all industrialized nations and will worsen in the future. A fluidized-bed process has been developed to treat these waste tires, wherein the tires were mostly pyrolyzed by the heat of oxidation of the tires themselves. Experiments using both tire chips and whole tires are described. All the products, such as oil, char and gas, were found to be capable of reutilization as important resources.

Magnesium requirement for biological removal of phosphate by activated sludge

Abstract The effects of magnesium on excess uptake of phosphate in an aerobic-anaerobic activated sludge process were examined by the fill and draw procedure. The alternation of anaerobic and aerobic conditions in one cycle of fill and draw process was varied many ways. The presence of sufficient magnesium was necessary for uptake of excess phosphate. When sludge contained more phosphorus than the upper limit of phosphorus content in the usual aerobic activated sludge, 2.5% by weight, magnesium was also contained in more than an ordinary amount (0.5%). Their contents in the sludge at the end of each cycle of the process were correlated with each other by a linear equation with the correlation coefficient of 0.99. When magnesium concentration was insufficient for the uptake of excess phosphate, its concentration in the treated water was of the order of 0.1 mg/l. In the first anaerobic period both phosphate and magnesium were released, and in a successive aerobic period they were taken up again. The weight ratio of differential amounts of phosphorus and magnesium released or taken up changed with time in one cycle. Dynamic behaviors of phosphate and magnesium removal against the step change of feed magnesium concentration also showed a stoichiometric relationship supporting the correlation equation above mentioned.

Citric acid production by surface culture using Aspergillus niger: Kinetics and simulation

Abstract The citric acid production rate for batch surface culture using Aspergillus niger Yang no. 2 was examined experimentally in terms of rate coefficients and the effect of various depths of medium. The citric acid production rate was affected by the biofilm mass expressed as mg-Cell/cm2-film. The biofilm mass increased in parallel with medium depth. The citric acid production rate divided by the biomass weight at the end of cultivation was constant when the biofilm mass was less than 40 mg/cm2, but decreased above this critical value. The citric acid fermentation time course was expressed by the Luedeking-Piret type rate expression. The time course of the surface cultivation was simulated well with the expression when biofilm mass was less than 40 mg/cm2. In this range, rate coefficients were obtained by the nonlinear least squares method. Comparison in regard to the citric acid productivity between surface and other types of cultures in the literatures was made.

Potassium removal accompanied by enhanced biological phosphate removal.

Abstract The effects of potassium on excess uptake of phosphate in an aerobic-anaerobic activated sludge process were examined by the fill-and-draw procedure. The presence of sufficient potassium was necessary for excess uptake to occur. The contents of potassium and phosphate in the sludge at the end of each cycle of the process were correlated with each other by a non-linear equation, with some scattering. However, the sum of the molar ion valences of magnesium ( Mg ) and potassium ( K ), 2 Mg + K , was well correlated by a linear equation with the moles of P expressed as mmol/g-VSS, with a correlation coefficient of 0.993. When the potassium concentration was insufficient for the enhanced uptake of phosphate, its concentration in treated water was of the order of 0.1 mg/ l . In the first anaerobic period phosphate was released into the liquid phase, but potassium was released after initial instantaneous removal, and in the successive aerobic period they were both taken up again.

The maximum crushing capacity of a wood particle crusher

The relationship between the increasing rate of holdup and the material-feeding rate were examined. From the results, the maximum crushing capacity was defined as the maximum feed rate where holdup did not change with time and remained at a constant value. The effect of the hammer rotation speed, ω, and the reduction ratio, Dv/dv, on the maximum crushing capacity, Fmax, was expressed as follows: Fmax=K2(Dv/dv)-1ω2

Aeration method and phosphate release behavior in phosphate removal by sea water activated sludge

Abstract The upper limit of the length of the anaerobic period necessary to achieve an excess uptake of phosphate (P), and the relationship between P release and removal were examined by the fill-and-draw anaerobic-aerobic sea water activated sludge process. An anaerobic period of less than 8 h was favorable to achieve an uptake of excess P. The dimensionless amount of released P normalized by BOD fed in one cycle was smaller for sea water sludge than that for fresh water sludge when both sludges realized the same dimensionless amount of P removal normalized by BOD fed in the cycle. The orthophosphate concentration in cold acid extract was 4.49% of total P in the sludge solid. Thus P was mainly taken up biologically by sea water activated sludge.

FORCED CONVECTION HEAT TRANSFER FROM SUBMERGED SURFACE TO LIQUID HELIUM

Heat transfer from a vertical copper surface submerged in circulating liquid helium in a dewar was studied experimentally. Heat transfer increased with the increase of velocity of liquid helium in convective heat transfer region. The data were correlated with an empirical equation as Nusselt number vs. Reynolds number. The peak nucleate boiling heat flux decreased with increasing flow velocity, whereas minimum film boiling heat flux increased with circulating flow velocity.

The Influence of Ultrasonic Wave on Mass Transfer from a Flat Plate in Low Re Number

低Re数域内の正方管の底部に物質移動部を設け, 物質移動を促進させるために, 超音波を管の上から照射した。物質移動の促進は, 流量の影響や, 超音波によって生じた局所的な撹乱流れによるよりも, むしろコヒーレントな超音波によって生じた壁に垂直な速度成分によると考えられる。また物質移動は次の無次元式で表わすことができる。