Tungsten Lamps of High Efficiency-I

1. The efficiency at which the larger sizes of tungsten lamps may be profitably run, is limited principally by the blackening of the bulb. 2. It has usually been considered that the blackening of ordinary lamps was due very largely, if not entirely, to the presence of residual gases. The evidence which has led to this belief is discussed. 3. The sources of gases within the lamp are studied, and the principal gases are found to be water vapor, carbon dioxide, carbon monoxide, hydrogen, nitrogen, and vapors of hydrocarbons. 4. The specific effects produced by these and other gases are determined. It is found that water vapor, which has long been known to be harmful, is the only one that produces perceptible blackening of the bulbs. 5. The blackening by water vapor is due to a cyclic process in which the water oxidizes the tungsten and is itself reduced to atomic hydrogen. The tungsten oxide volatilizes and deposits on the bulb, where it is reduced by the atomic hydrogen to metallic tungsten and water vapor is again formed. 6. Attempts to materially improve the life of lamps by the more complete removal of water vapor result in failure. It is therefore concluded that, although water vapor is usually the cause of the short life of poorly exhausted lamps, yet it is not the cause of blackening in well exhausted lamps. 7.

The simultaneous adsorption of water and hydrocarbon vapor from natural gas bythree grades of alumina has been studied at atmospheric pressure andtemperature. Results of this investigation reveal that the presence of watervapor in the gas inhibits the adsorption of hydrocarbon vapor, although thepresence of the latter does not have a pronounced effect upon the adsorption ofwater vapor. Adsorption of water-hydrocarbon mixtures from gas is divided intothree phases. In the first, both water and hydrocarbon vapor are adsorbed; inthe second, adsorption of water vapor proceeds while desorption of hydrocarbontakes place; in-the third phase, the adsorbent approaches complete saturationwith respect to both water and hydrocarbon vapors. Both theory and experimentaldata can be applied to design and operation of commercial dehydration plants, and an illustration is presented. Introduction Dehydration of natural gas becomes increasingly important as the operatingpressures employed in gas processing and transmission are increased above 500lb. per sq. in. Gas produced from high-pressure wells is saturated with watervapor when it leaves the reservoir and it continues into the processing plantor transmission system in a saturated condition because of the substantialdecrease in temperature due to expansion at the wellhead. Usually this gas isaccompanied by liquid water and hydrocarbons that have condensed with thechange in temperature and pressure. Without dehydration, gas temperatures must be held at relatively high levels toprevent solidification of gas hydrates. According to Hammerschmidt's data onthe relationship of pressure to the freezing point of natural-gas hydrates, theminimum safe operating temperatures range from 55? to 90?F for pressuresranging from 500 to 3000 lb. per sq. in., respectively. Often it is difficultto maintain gas temperatures above the hydrate-freezing temperature because ofclimatic conditions, unless flow-line heaters are installed. Also, inprocessing gas for its gasoline content at high pressures, it is desirable toemploy operating temperatures lower than the hydrate-freezing point. Indistributing high-pressure gas, the large pressure drop from line pressure totown-gate pressure often produces sufficient cooling to freeze the regulatorsand disrupt consumer service. Therefore, it is highly essential to dehydratehigh-pressure natural gas if smooth and economical operation is to bemaintained at all times. Few published data are available on the simultaneous adsorption of water andhydrocarbon vapors. T.P. 1628

Pinholes in aluminium alloy castings are due to gas, mainly hydrogen, liberated during solidification of the molten metal, and it remains in the metal as small bubbles. The origin of hydrogen in aluminium was shown by many authors to be ascribed to the decomposition of water vapour by the melt. How hydrogen originating from water vapour is absorbed by the melt, forms the subject of the present report, the results obtained being summarised as follows: - (1) Oxide film on the surface of the molten metal forms a remarkable protective barrier against water vapour. Owing to this protective action of the oxide coating, pinholes seldom occur even when steam is blown against the surface of the melt. The moisture in the atomosphere, therefore, seems to have almost no effect upon the melt, provided that it is coated with oxide film. On the other hand, direct contact with steam by removing the oxide film from the melt results in the formation of numerous pinholes. (2) That pinholes in aluminium alloys castings are mainly due to water vapour from the sand mould has been experimentally proved. Thus, when the oxide coating is removed in casting the metal into the mould, the most favourable condition for the absorption of hydrogen is established. (3) Hydrogen originating from water vapour seems to be in nascent state and has been found to be absorbed with great rapidity, … within 10 seconds. Prolonged contact of water vapour with the molten metal, however, does not appreciably increase the gas content in the metal. (4) Gases other than water vapour, namely, hydrogen, acetylene, carbon monoxide, and carbon dioxide were blown into the melt to examine their degree of pinhole formation. It has been found that hydrogen at a temperature below 800° is feeble, above this temperature its action gradually becomes vigorous; the action of acetylene resembles that of hydrogen, while carbon monoxide and carbon dioxide are almost inactive in creating pinholes. As the results of the above-mentioned tests, water vapour has been found, to be far more effective than the other gases in creating pinholes. (5) Gas absorbed by the melt can easily be removed by remelting, by treating with dry fluxes, or by maintaining the melt at a suitable temperature for approximately 20 minutes.

Attack of graphite by an oxidising gas at low partial pressures and high temperatures

The study presents a mathematical model to analyze the dynamic evolution of molar concentrations for toluene (C7H8), water vapor (H2O) carbon monoxide (CO), hydrogen (H2), methane (CH4) and carbon dioxide (CO2) in fixed bed catalytic reactor. The mathematical model was discretized using the method of lines (MDLs) to transform the system of partial differential equations (PDEs) in a system of ordinary differential equations (ODE). The system of ODEs has been solved by the implementation of the RungeKutta Gill to estimate the chemical species C7H8, H2, CO, H2, CH4 and CO2.The estimation allows the quantification of individual forecasts of the variables presented in this study. However, valuable information can be obtained from the estimated behaviors in fixed bed catalytic reactor. The model has allowed the validation of chemical species (H2, CO and CO2) by comparing the optimized values. Additionally, the concentrations for the chemical species C7H8, H2, CO, H2, CH4 and CO2 was studied.

In ground tests of hypersonic scramjet, the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants of water vapor and carbon dioxide. The contaminants may change the ignition characteristics of fuels between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels, the effect of water vapor and carbon dioxide on the ignition delay times of China RP-3 kerosene was studied behind reflected shock waves in a preheated shock tube. Experiments were conducted over a wider temperature range of 800–1 500K, at a pressure of 0.3 MPa, equivalence ratios of 0.5 and 1, and oxygen concentration of 20%. Ignition delay times were determined from the onset of the excited radical OH emission together with the pressure profile. Ignition delay times were measured for four cases: (1) clean gas, (2) gas vitiated with 10% and 20% water vapor in mole, (3) gas vitiated with 10% carbon dioxide in mole, and (4) gas vitiated with 10% water vapor and 10% carbon dioxide, 20% water vapor and 10% carbon dioxide in mole. The results show that carbon dioxide produces an inhibiting effect at temperatures below 1 300 K when ϕ = 0.5, whereas water vapor appears to accelerate the ignition process below a critical temperature of about 1 000 K when ϕ = 0.5. When both water vapor and carbon dioxide exist together, a minor inhibiting effect is observed at ϕ = 0.5, while no effect is found at ϕ = 1.0. The results are also discussed preliminary by considering both the combustion reaction mechanism and the thermophysics properties of the fuel mixtures. The current measurements demonstrate vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of China RP-3 kerosene at air-like O2 concentration. It is important to account for such effects when data are extrapolated from ground testing to real flight conditions.

Analysis of the long term NOAA carbon dioxide flask sample records to examine the exchange among the continental Antarctic air mass and other air masses shows a meteorological variation of carbon dioxide concentration. There is an inverse relation between the seasonal variation of carbon dioxide concentration and water vapor at all stations examined. Well established diffusion coefficients indicate an interaction of water and carbon dioxide vapor on the molecular scale. Laboratory experiments using a Fourier transform spectrometer show carbon dioxide to be removed from an airstream in proportion to water vapor precipitated. We propose that interaction of carbon dioxide and water vapor in the atmosphere provides temporary sinks that can influence the balance of the carbon dioxide budget.

Aerobic decomposition of organic wastes I. Stoichiometric calculation of air change

Capturing rogue carbon

Pretreatment stage is usually a requirement for any adsorption based air separation process. Carbon dioxide and water vapor present in the atmosphere act as contaminants, deactivating adsorbents, particularly zeolites used in oxygen pressure swing adsorption processes. Such systems usually present one or more prelayers to ensure full removal of these two contaminants, protecting the oxygen/nitrogen selective layer. In the present study, two 13X-type zeolites—one activated alumina and one highly pure silica—are compared in terms of capacity for water vapor and carbon dioxide removal from air. Water and carbon dioxide adsorb irreversibly on these adsorbents up to a certain extension and then effective adsorption isotherms and breakthroughs curves were obtained. The effective properties were attained after three cycles under close to vacuum pressure swing adsorption conditions. A combination of two layers for the precolumns is suggested: the first, composed by either silica or alumina to remove most of the water without significant loss of cyclic adsorption capacity, and a second, composed by zeolite, to reduce the amount of water and carbon dioxide down to parts per million (ppm) levels. These should prevent contamination and consequent loss of efficiency in the nitrogen/oxygen selective layer.

Detection of water vapour or carbon dioxide using a zirconia pump-gauge sensor

The complete reduction of iron oxide on heating the initial Fe3O4–H2O–C system with isothermal holding is subjected to thermodynamic analysis. (Note that the initial system contains eo moles of Fe3O4 and bo moles of H2O, with excess carbon.) The processes in the system may be divided into four stages. First, the gasification of carbon by water vapor at temperatures below 880 K activates the reaction of the water gas and the dissociation of CO with the formation of lamp black (solid carbon). The composition of the H2–H2O–CO–CO2 gas mixture obtained depends only on the temperature. The carbon consumption at 880 K is ~0.445 mole per mole of water. The second stage, in the range 880–917 K, is the reduction of Fe3O4 to wustite FeO1+x with different degrees of oxidation. Hydrogen reduces the oxide at temperatures above 888 K. The proportion of the oxide reduced by hydrogen in this temperature range increases from zero to ~63%. The total quantity of Fe3O4 reduced to wustite at 917 K is ~123 moles per mole of water. This is only possible with repeated regeneration of the reducing agents CO and H2 as a result of the gasification of carbon by water vapor and carbon dioxide CO2. The carbon consumption is approximately 78 moles. In the third stage, the wustite FeO1.092 is reduced solely by carbon monoxide CO in the range 917–955°C to wustite FeO1.054, with a lower degree of oxidation. The carbon is only gasified by CO2; the carbon consumption is around 18 moles. In the fourth stage, with isothermal holding at ~955 K, the wustite is reduced to iron by carbon monoxide alone. The carbon consumption is around 257 moles. In a closed system at 1 atm, 1 mole of water is sufficient for the complete reduction of around 123 moles of Fe3O4 in a mixture with excess carbon. The total carbon consumption is ~353 moles, with the production of 368 moles of Fe; that is, the carbon consumption is ~0.21 kg/kg of iron.

According to the present data, KA zeolite, which can adsorb only water vapor, helium, and hydrogen, has the greatest selectivity in drying. The feasibility of using this zeolite in devices for selective drying of gases used in gas-analysis systems was studied. The results of the experiments were approximated by the thermal equation of the theory of bulk filling of micropores. The limiting value of the adsorption depends on the temperature, and it can be calculated according to the density of the adsorbed phase and the adsorption volume. The critical diameters of the water and carbon dioxide molecules are close to the dimensions of the KA-zeolite pores, something that determines the activated nature of the adsorption of these substances. Experiments on coadsorption of water vapor and carbon dioxide by a fixed bed of KA-zeolite under dynamic conditions showed that the adsorption of these substances has a frontal nature. The time of the protective action of the layer of zeolite during adsorption af water vapor exceeded by more than an order the time of the protective action during adsorption of carbon dioxide. The results showed that this adsorbent can be used for selective drying of gas mixtures containing carbon dioxide in batch-operationmore » devices. Beforehand, the adsorbent should be regenerated with respect to moisture, and then it should be saturated with carbon dioxide by blowing the adsorbent with a gas mixture of the working composition until the equilibrium state is reached.« less

A mass spectrometer study is made of the residual gases in several types of vacuum evaporators ranging from oil-diffusion-pumped, conventional systems to an oil-free, ultra-high-vacuum chamber. Partial pressures of water vapor, hydrogen, carbon monoxide, carbon dioxide, nitrogen, oxygen, argon and hydrocarbon vapors varied appreciably in the evaporators studied. The performance of a conventional system was improved by using special low-vapor-pressure gasket materials to minimize hydrocarbon contamination, a liquid-nitrogen trap to reduce water vapor, titanium gettering for oxygen and nickel-iron gettering for hydrogen. For thin-film deposition, the importance of thoroughly outgassing the source materials is pointed out.

Water vapor and carbon dioxide species measurements in narrow channels