Constant Initial Pressure Research Articles

KINETICS OF THERMAL LIQUEFACTION OF SEYITÖMER LIGNITE

ABSTRACT Kinetics of non-catalytic liquefaction of Seyitomsr lignite has been investigated under hydrogen pressure, using tetralin as a Bolvent in a laboratory Bcale batch autoclave reactor. In the first set of experiment hydrogen initial pressure and reaction temperature were kept constant, the reaction time and coal/aolvent ratio were changed at five and three levels espectively. In the second set of experiments coal/solvent ratio was kept constant and hydrogen initial pressure, reaction temperature and time were individually changed at four levels. The produot was analyzed in terms of total conversion, liquid yield and liquid product distribution determined as preasphaltenes, asphaltense and oila. A satisfactory correlation was obtained using the kinetic model proposed by Shalabi et al (1979).

Analytical solutions of one-dimensional problems of gas flow for quadratic resistance law

A study is made of one-dimensional (plane and axisymmetric) problems of the isothermal flow of gas through a porous medium for quadratic resistance law. Self-similar equations for the velocity and pressure of the gas in the porous medium are obtained. Analytical expressions for the pressure and velocity of the gas for constant initial pressure in the medium are obtained. A quadratic dependence of the resistance on the velocity [1,2] is used to describe the motion of the gas in the porous medium at high Reynolds numbers. (Re > 10).

Low pressure R.F. plasma reactions in light hydrocarbons: Ethylene and acetylene

The results obtained in the plasmolysis of ethylene and acetylene in an inductively coupled radiofrequency glow discharge are reported. A static system at a constant initial pressure of 0.5 torr and input power of 50 W was used; the gaseous and polymeric products were evaluated and compared with previous data on ethane plasmolysis and other available literature data. The decomposition products of ethylene were similar to those obtained during the plasmolysis of ethane, with a different distribution and a smaller initial increase of the total pressure. The total pressure of acetylene quickly decreased to near zero value at small specific energy, due to rapid polymerization. No gaseous products were detected, except hydrogen and traces of diacetylene.

R.F. plasma reactions in light hydrocarbons: Effect of the input power on the decomposition of ethane

The effect of the input power on the plasma decomposition of ethane in an inductively coupled radiofrequency glow discharge was studied with a static system at a constant initial pressure of 0.5 torr, with specific energy E s up to 2 × 10 6Jg -1. Input power values of 25, 50 and 100 W were used. The gaseous products were analyzed by gas chromatography. The effect of power input change was found to be smaller than the previously studied influence of the initial pressure variation. The yields of C 2H 4 and C 2H 2 slightly increases with increasing W, while the yield of CH 4 shows a greater variation. The yield of C 3H 8 decreases with increasing W and other heavy products do not show appreciable change. The yield of the crosslinked polymethylene formed as solid product slightly increases and its H/C ratio (about 1.5) slightly decreases with increasing W.

The hydrogen-oxygen reaction on lanthanide oxides: VII. The hydrogen-oxygen reaction on samarium oxide

The stoichiometric hydrogen-oxygen reaction has been studied over samarium oxide at an approximately constant initial hydrogen pressure of 220 N m −1 over the temperature range 323 to 558 K and at varying initial hydrogen pressures at six different temperatures. The nonstoichiometric reaction has been studied at hydrogen-oxygen ratios from 0.14 to 10.2, at initial hydrogen pressures up to about 1 × 10 3 N m −2, and at 423, 500, 589, and 650 K. After detailed kinetic analysis it appears that the results best fit an equation of the form: −dP T dt = kb H 2 2P H 2 2b O 2 P O 2 (1 + b H 2 P H 2 + b O 2 P O 2 ) 3 , where k is a proportionality constant, b H 2 and b O 2 are the adsorption coefficients for hydrogen and oxygen, respectively, p t is the total pressure of hydrogen plus oxygen, and P H 2 and P O 2 are the partial pressures for hydrogen and oxygen, respectively. The most likely mechanism is one involving the competitive adsorption of molecular hydrogen and oxygen, with the ratedetermining step involving the interaction between H 2O 2(ads) and H 2(ads).

On the shock-induced ignition of explosive gases

The paper elucidates the distinction between two regimes of ignition, one strong and the other weak, that characterize the onset of combustion in homogeneous gaseous mixtures whose reaction mechanism is controlled by a chain-branching step, such as that associated with the H+O2 collision in the hydrogen-oxygen system. On the basis of experimental observations, made primarily by the use of a stroboscopic laser-schlieren system yielding a sequence of photographic records of the entire flow field behind a reflected shock near the closed end of the tube at a repetition rate of 2 microseconds between frames, it has been revealed that strong ignition is manifested by a practically instantaneous appearance of a relatively plane pressure front associated with the generation of a flow field across the whole cross section of the tube, while mild ignition starts in the form of distinct flame kernels whose growth is comparatively slow and essentially devoid of any gasdynamic effects. The demarcation line between the two regimes of ignition is then shown to be associated with a critical value of the gradient of the induction time with respect to temperature at constant initial pressure. Specifically, for a stoichiometric hydrogen-oxygen mixture, this turns out to be −2 microseconds/°K. Although basically controlled by the same elementary processes as those that establish the second explosion limit, this so-called strong ignition limit differs from the locus of states obtained by direct extrapolation of the second limit. Moreover, it does not intersect with any of the explosion limits, encompassing a region that is fully contained within the classical explosion regime.

Precision Flash X-Ray Determination of Density Ratio in Gaseous Detonations

An x-ray densitometer has been used to measure the density ratio across a detonation wave in a number of different gaseous mixtures involving C2H2, C2N2, or H2 with O2 and Kr. In a 3-in. i.d. tube at an initial pressure of 60 cm the density ratios observed were between 1.64 and 1.67. Investigations of the influence on density ratio of tube diameter at constant initial pressure and of initial pressure at constant tube diameter both indicate an extrapolated infinite diameter density ratio of 1.70 for a 0.3 C2H2 + 0.3 O2 + 0.4 Kr mixture. This result is significantly lower than the ratio 1.79 which corresponds to the tangent point on the equilibrium Hugoniot from the initial state. At the present time these observations cannot adequately be explained by detonation theory.

Observations and reflections on manometric calibrations with air: Methods for indolent mercurophobes

Methods approaching the ultimate in simplicity, accuracy, reproducibility, and rapidity have been described for the calibration of manometric vessel and capillary volumes with either known or unknown volumes of air, withdrawn from or added to the test manometer system by means of a precalibrated reference standard manometer system (or other equivalent precalibrated device) connected by tubing to the test manometer. Two fundamental steps of procedure are employed, in accordance with Boyle's law, to obtain measurements applicable in two simultaneous equations for two unique conditions of simplicity, the one at constant pressure, the other at constant volume. In the first step, after initial equilibration, the standardizing volume of air is transferred between standard (∗) and test manometer with releveling to constant initial pressure (Δ P = 0), yielding a determination of v, the capillary volume per specified length, from no more than simple inverse proportionality between the observed capillary fluid length changes ( v = v ∗L ∗ L ). In the second step the manometers are closed off at their stopcocks and the confined gases brought back to their initial space volumes (Δ V = 0), yielding a determination of the vessel gas space volume v g , from no more than simple inverse proportionality between the observed capillary fluid pressure changes ( v g = v g ∗h ∗ h ). v ∗ and v g ∗ are previously known from the standard manometer, L ∗ and h ∗ are obtained with it, and L and h with the test manometer. Our most recommended procedures for measuring manometric capillary ( v) and vessel ( V) values (Eqs. (1′) and (5) with known volumes of air, see Table I, and Fig 1, and Eqs. (1′ u) and (5 u) with unknown volumes) require no (numerical) knowledge of barometric pressure, watervap or pressure, absolute temperature, “dead space” of connecting tubes, solubility of air in water, etc., apart from assurance of maintenance of their constancy during manipulations. These factors and other second- and third-order effects (difference in draining of capillaries, changes in dissolved air with pressure changes, differences of temperature outside and inside the thermostat) that enter into applied manometry, are in principle rendered negligible by the differential methodology of our procedure of calibrating a test manometer with another (precalibrated) manometer. The accuracy and reproducibility of these air calibrations can be adjusted, depending upon the will and the skill of the investigator, either to the maximum attainable in operating manometry (say ± 0.2%), or to an accuracy as good or better than that employed in 95 % of all manometry, namely ±1 %. Methods for the minimization or actual elimination of thermobarometric (TB) changes, an important factor largely neglected in previously described methodology of air calibration, are outlined. The outer manometer arms are not left open to the external atmosphere, but are connected with a large vessel (e.g., a 20-l. carboy) whose pressure can be manipulated (as by a large connected syringe) so that any effects of pressure or temperature variations can be readily restored to precisely zero in the TB manometer, and simultaneously thereby in all other manometers connected in parallel. The uses and advantages of such a carboysyringe device in not only calibration, but even more importantly and generally, in many aspects of operative manometry, are indicated. No manometric laboratory should be without such a device (see Fig 1). The proposed methodology is recommended to all indolent mercurophobes and aerophiles, for whom the gravity of the problem of mercury calibration is herewith reduced by the levity of air, and a little air of levity.

空氣マイクロメータの靜特性(第6報)

This pneumatic divice makes use of the variation in total resistance of a compressed gas leaving from two symmetrical orifices which are at an equal short distance (h) from the wall (its diameter D) of a workpiece to be measured. It is arranged so that the compressed air with constant initial pressure (PA), passing through the fixed orifice, may part into two branches to jet out of two measuring orifices, and that the pressure of the air in the space between the fixed orifice and the branching point can be measured. The nondimensional amplification |dPC/dD| (dB/PA). (dB/d2) and the suitable clearance (h/dB).(d2/dB) are respectively represented theoretically as the functions of a characteristic parameter (dynamic similarity factor) consisting of Reynolds Number, d2/d1 and dB/d2 The results thus obtained fairly agree with those of the experiment. When two jetting clearances are not equal, errors in comparative checkingwhich are small in comparing with the symmetrically standard characteristics will appear. Such errors, however, can be eliminated only by keeping two jets with guide pieces, contacting very closely to the works, horizontal. We can plan through the rtsults obtained the checking of ID by air spindles, OD by air rings and thickness of plastics and foils by air snaps with any desirable sensitivity.

The dissociation of carbon dioxide at high temperatures

The power of an internal combustion engine is greatest when operating with a “rich” mixture, that is to say, with a mixture which contains more fuel than is necessary for complete combustion. Similarly, it is found that if mixtures of carbon monoxide and air in varying proportions are exploded in a closed bomb at constant initial temperature and pressure, the explosion pressure is greatest when the ratio CO/O 2 is greater than 2. These phenomena are known to be connected with the dissociation of carbon dioxide at high temperatures, for if there were no dissociation we should expect the explosion pressure to be greatest when CO/O 2 = 2. No attention appears, however, to have been paid to the position of the maximum. It can be shown in the following way that there is a very simple relation between the composition of the mixture giving maximum pressure on explosion, and the dissociation of carbon dioxide at the maximum explosion temperature. Let the initial composition be represented by the expression 2 (1 + a ) CO + O 2 + b N 2 (Total mols = 3 + 2 a + b ), and let P i , T i represent the initial pressure and temperature; P e the maximum pressure observed after explosion, and T e the corresponding maximum temperature.