An approach for determining ignition temperature of adiabatic fixed-bed reactors is suggested. A phase plane of dimensionless temperature θ and of dimensionless concentration is used to show both the ignition curve and the extinction curve of a single catalyst pellet. Also expressed in the phase plane is the trajectory depicting the deepening of the reaction, the trajectory being the operating line of the reactor. This trajectory is a straight line, the slope of which is always -45°. The reactor definitely ignites once the trajectory touches the catalyst ignition curve. A kinetics-free approach is recommended which enables precise determination of critical inlet temperature causing reactor ignition. Zero-order assumption can be securely made because only very limited error is brought about. In the meantime, experimentation is greatly simplified.

One-dimensional, heterogeneous model for transient state is used for simulating steady-state temperature profiles of adiabatic fixed-bed reactors. Since the length of the high-temperature zone is determined by the temperature profile, it is essential to investigate factors affecting temperature profile. This paper discusses the influences of heat conduction of the bed, of the gas and of the reactor wall. An example is given for making explanation clearer. Results show that for experimental reactors the effect of heat conduction through reactor wall is by no means negligible; therefore, this effect should be taken into account during reactor scale-up.

Ignition and extinction of radial flow reactors are different from those of axial flow ones because of the change of gas velocity. This paper deals with ignition and temperature profiles of both centrifugal and centripetal flow reactors. An example is given showing the difference between axial and radial flow reactors.

Axial mixing of continuous phase in a rotating disk extraction column has been studies by considering the flow characteristics of fluids in the column. Equations were developed to predict the effects of rotation speed of the disks, continuous-phase flow rate and disperse-phase flow rate on the axial mixing of the continuous-phase. For single phase flow, the overall axial mixing can be considered as the combined contribution from eddy diffusion and channeling phenomenon. The axial mixing of continuous-phase in single phase flow can be described by the following equation: For two phase counterflow in the column, the axial mixing of continuous-phase becomes even more complex owing to swarming of drops of disperse-phase. Physical model developed as well as experimental results indicates that axial mixing of continuous-phase could either be enhanced or diminished by the disperse-phase flow as operating conditions vary. The motion of wakes of continuous-phase behind the drops increases thebackmixing of continuous-phase. The backmixing ratio fw, from the wake movement can be represented by The movement of a swarm of drops in a continuous-phase reduces the channeling flow of continuous-phase and thus forward mixing. Decrease of the ratio of forward mixing AW can be correlated by The total contribution of disperse-phase to the axial mixing of continuous-phase is given by (fw-△W). Experimental results of axial mixing of continuous-phase in two phase counter-current flow can be represented satisfactorily by the following equation:

Vapor-liquid equilibrium of 4-methyl-2-pentanol and water was determined at 760 mm Hg with a modified circulation still within the temperature range of 94.37 to 131.38℃. Liquid-liquid equilibrium for the same system was determined by the closed-tube method in the same temperature range. The NRTL parameters correlated from the liquid-liquid equilibrium data were used to calculate the vapor-liquid equilibrium with mean deviations of temperature and vapor composition of 0.61℃ and 0.0131 mole fraction, respectively.

In order to clarify the cause of tube failures in high pressure waste heat boilers with vertical U-shaped tubes, a series of tests was made to study flow pattern transitions over wide velocity ranges of ambient air-water mixtures in a 21.5mm 1. D. vertical U-shaped tubes with 180°-bends of radii 694,500 and 320 mm respectively. The flow patterns observed in these bends were similar to those in horizontal two-phase flow. The data obtained showed that the differences from the horizontal flow were the expansion of stratified flow and restriction of wavy and intermittent flow. Both annular and dispersed transitions were quite close to those in horizontal tubes. The transition data obtained in the present tests were compared with the transition correlations of Mandhane et al. and Weisman et al. forhorizontal tubes. An overall flow pattern diagram based on the present tests was established in terms of superficial gas and liquid velocities, VsG and VSL. Correlations for determining flow pattern transitions were suggested. The effects of the bend radii on flow pattern transitions are small within the test range.

In order to clarify the cause of failure in waste heat boilers with vertical U-shaped tubes, variation of wall temperature along the bend under thermal conditions was investigated in an electrically heated high pressure water loop experimental installation. The water loop consisted of a 25 mm i. d. stainless steel tube with a 180° bend of radius 700 mm operating under the conditions of P=106×105Pa, G=800-2000 kg/m2·s and q = 80-330kW/m2·In the tests, the circumferential wall temperature profile along the bend was found to increase from the middle of the downward section of the tube to 15°of the upward section, at low mass velocities and low steam qualities, reaching a peak value at (?)=75°. The temperature difference, △t, between the inner side and outer side of the bend was found to vary with mass velocity, steam quality and heat flux, increasing abruptly to a peak value at low steam qualities. Variation of △t was noted to reflect the influence of flow pattern transitions. As may be anticipated, the flow regime belongs to stratified flow for low mass velocities and low steam qualities. In this regime, slow-moving vapor, packets on the inner wall of the bend, and hence low heat transfer rates may be expected to lead to large temperature gradients. For bigher steam qualities, inter-mittent two-phase flow may be expected to reduce the temperature difference. Finally, appearance of liquid film around the tube wall in the annular flow regime may be anticipated to result in considerable suppression of the temperature difference.

Vertical U-shaped tubes have been used in some waste heat boilers of targe synthetic ammonia plants. In operation, accident of tube failure at the bend due to overheating occurs frequently. The present tests showed that under the action of both centrifugal and gravitational forces, tratification of steam-water flow occurs, leading to heat transfer deterioration on the inner side of the bend. In order to solve the problem, three types of inserted turbulator-a single twisted tape, a double twisted tape and a spiral coil-were tested in a high-pressure electrically heated water-loop experimental installation. Boiling heat transfer and pressure drop characteristics were investigated. The experimental loop consisted of a φ25 × 2 mm stainless steel tube with a 180° bend of 700mm radius, under an operating pressure of 106 × 105Pa. These tests showed that boiling heat transfer deterioration might be eliminated effectively by use of any of the three types of inserted turbulator. The pressure drop of the turbulators were determined, and then the single-phase friction factor relationships were obtained. The Chisholm equation was used to correlate the data of the two-phase pressure drop, and acorrelation for determining the two-phase frictional multiplier was proposed. In order to understand the operating mechanism of the inserted turbulator, flow pattern observations of the single twisted tape were carried out in a transparent tube for air-water flow and an overall flow-pattern map was established in terms of superficial liquid and gas velocities. The single twi-sted tape, which was found to have the lowest frictional pressure drop, is recommended for waste heat boilers.

The rheological behavior of HIPS prepolymers with rubber having different molecular weights were studied. It was found that, besides the phase inversion point, there existed another minimum on the apparent visco-sity-versus-conversion curve at about 7% conversion. The rheological characteristics of the prepolymers were also affected by agitation speed, viz , the higher the speed, the lower the apparent viscosity of the prepolymer obtained. These phenomena were explained in terms of the two-phase characteristics of the prepolymer. Furthermore, the temperature effect on the prepolymer Theological behavior was investigated, and the apparent visco-sity(ηa)can be correlated with temperature(T)and shear rate(γ)by where A1, A2, B1 and B2 are regression coefficients.

The kinetics of carbon deposition and its subsequent gasification by steam in the heptane-steam reforming process on a Chinese nickel catalyst has been studied in the temperature range of 460-550℃ and at a pressure of 1.01 ×105 Pa. The constant coking rates are represented as without steam ro = 1.99 ×107exp(-16100/RT)PHep0.97., with steam re=4.71 × 106exp( -18600/RT)PHep0.94.PH2O-0.98, and the constant decoking rates as carbon deposited without steam carbon deposition with steam The reaction order, energy of activation, pre-exponential factor and the role of steam are discussed. It is concluded that the function of steam during carbon deposition is not only to gasify the deposited carbon, but also, more significantly to suppress the formation and growth of carbon fibre nuclei.

The mechanical degradation by high-speed stirring of poly (ethylene oxide) and polyacrylamide in aqueous solution were studied. The limiting chain length and the rate constant of degradation were shown to change with concentration, and the rate constant was shown to be related to stirring time at any given concentration. The dependence of the number of scission per molecule on stirring time can be expressed by the following equation According to the experimental result, it was inferred that molecules of neither polymer acquire the entanglement structure at a concentration of 0.5%.As shown by gel permeation chromatogram comparing the original and the degraded polymers, the molecular weight distribution of the latter became narrower.

Longitudinal mixing in a liquid-filled column packed with four sizes of Raschig-rings, 6×6, 8×8, 10×10 and 12×12 mm, using an air-water system, was studied in terms of velocities of the gas and liquid phases and the relative height of π-shape pipe. From analysis with a minicomputer, the following expression was obtained The experimental results showed that longitudinal mixing in a liquid-tilled column was comparable to that in a dry packed column.

In the paper, a succimide derivative was used as the surfactant, tri-n-octylamine as the mobile carrier, kerosene as the membrane solvent and Na2CO3 solution as the internal phase of the membrane to form a system of water-in-oil emulsified liquid membranes, in studying the extraction of uranium from sulfuric acid leach liquor. Factors affecting the stability of the liquid surfactant membranes and extraction efficiency of uranium were studied, and suitable technological conditions were determined. Experimental results showed the advantages of liquid membranes: rapid rate of uranium transport, high efficiency of extraction, high selectivity and good stability. The efficiency of uranium extraction was 99.4%.

Binodal curves and conjugate the lines were determined for the toluene -n-heptane-sulpholane ternary system at 30℃ and 50℃, and for the sul-oholane-n-heptane-water ternary system at 50℃. From these curves andany of the physical properties of the saturated solutions, such as refractive index or density, the equilibrium liquid-liquid compositions of the two ternary systems were found. The UNIQUAC equation was used to correlate the liquid-liquid equilibrium data of the first ternary system, including the UNIQUAC parameters at 30℃ and 50℃, and the UNIFAC method was used to predict the liquid-liquid equilibrium data of both ternary systems. Agreement between calculated and experimental data is satisfactory.

The adsorption kinetics of C8 aromatic hydrocarbons in diethylbezene solution was studied by a transient method. The breakthrough curves of para-xylene, orthoxylene, ethylbenzene in diethylbenzene solution at 170℃ were measured respectively. From the breakthrough curves as well as the related parameters and relations, we analyzed and computed some properties. The controlling mechanism of the adsorption process for this system was also investigated and determined.