The work was undertaken to determine the reaction rate of the catalytic dehydrogenation of ethanol and aqueous solution of ethanol. The reaction rate was measured over the range of space velocities (3.0×10³3.8×10²) and temperatures (240°270°C), using the Cu-Cr catalyst coating the carrier. Taking into consideration the reverse reaction, the following equation based on partial pressures of the reactant and the products was derived from the data obtained.
r=3.86×10¹¹e-19720/RT(n_EtOH/n_t-n_AcHn_H2/Kn_t²)
where
n_t=n_EtOH+n_AcH+n_H2+n_H2O
The proposed rate equation was employed in the operation of a pilot plant, in order to prove its applicability to practical use-designing of commercial reactors. The calculated values based on the rate equation were found to be in good agreement with the experimental results obtained with the pilot plant.

抄録全体を表示

The mechanism of the flow of gas in a fluidized bed at low pressure could be presumed from the formal analogy to the flow of gas in a capillary, but there had been no work reported on it. In order to make a contribution to the studies on the behavior of the fluidized bed at low pressure, the present work was carried out experimentally with the apparatus whose schematic diagram is shown in Fig. 1. Sifted sand, silica gel and glass beads were used as material samples and the operating conditions covered the range of pressures from 1 to 760mmHg, and that of linear velocities of gas from 10 to 250cm/sec
The results obtained may be summarized as follows:
(1) The behavior of the fluidized bed at low pressure has a resemblance to that at atmospheric pressure.
(2) It is more difficult to have a uniform fluidized bed at low pressure than at atmospheric pressure. χ, the ratio of ΔP to the gravitational force of the bed, falls between 0.85 and 0.95 as shown in Fig. 5.
(3) The relation between the pressure drop and the flow velocity through the bed at low pressure can be correlated with modified friction factor, f'' (comprizing F(ε), φ and the effect of slip-flow), in the experimental region of the present work, as shown in Figs. 7 and 8.
(4) The minimum flow rate for fluidization is found to decrease proportionally with the decrease in operating pressure as shown in Eq. (1); however, at a pressure lower than 100mmHg or so, no such linear relationship is found. Consequently, the corrected relation between the minimum flow rate for fluidization and pressure is proposed as given by Eq. (8), where the correction factor, J, has been obtained by correlating the conductance of capillary in the medium vacuum region. The experimental results from which Eq. (7) and J value for d_pP have been obtained are shown in Figs. 9 and 10.

抄録全体を表示

A theoretical analysis of the rate of anhydrous CaSO₄-scale deposition in sea-water evaporators is presented under the premise that the deposition may be regarded as a simple crystallization process of anhydrous CaSO₄ taking place on a heating surface superheated above the saturation temperature of evaporator liquid. Discussion is presented in Section 1 to show that the above simplified treatment is applicable to evaporation of sea water seeded with fine anhydrous CaSO₄ crystals to suppress scale formation.
By this simplified treatment, the surface temperature, t_w, of the heating surface in contact with the evaporator liquid is shown to be an essentially important factor to determine the rate of scale formation, which, therefore, depends on the question of which side of the heat-transfer wall has greater resistance to heat flow, -the liquid side or the vapor condensing side.
Equations (2) and (3) give the rate of scale formation and the thickness of the scale, respectively. When the equations are employed to analyze the published data on anhydrous-CaSO₄-scale formation in sea-water evaporators, a reasonable agreement is obtained between the measured data and the calculated values as shown in Fig. 3. Possible explanations for the deviation of the data from the theory are discussed. The data and the calculations are summarized in Table 1.
Based on this agreement, the influence of some important variables on the rate of scale formation is discussed, where the variables cover c_e/c_s, t_w, t_L and u. Some numerical examples are given for these variables, showing that the theory can predict the actual scale formation reasonably well.

抄録全体を表示