Gases composition

1 Gas Composition from the Feedstock Recycling of Single Plastics 

Polystyrene gives a low gas yield overall, since there is a much higher conversion of the plastic to oil/wax. The derived gas composition consists mainly of alkene gases, ethene, propene and butene and also methane. 

The pyrolysis of polyethylene terephthalate produces a gas consisting mainly of carbon dioxide and carbon monoxide, due to the high oxygen content of the original plastic 

3 OIUWAX COMPOSITION FROM THE FEEDSTOCK RECYCLING OF SINGLE PLASTICS 

The test gas must be of uniform and known composition. This generally requires on-line gas analysis if flammable mixtures are not supplied from a suitable reservoir. If concentration gradients are created in the surrounding air, errors can be introduced by releasing the test gas stream from a perforated probe doubling as an electrode. The maximum effective energy of a 

Fuels such as diesel and kerosene readily absorb hydrocarbon vapors, the total uptake and absorption rate depending on both chemical and physical factors. If a soluble test gas is introduced above a charged test oil the concentration of flammable test gas therefore decreases with time. Liquid mist and spray produced by charged liquid increase the absorption rate relative to a quiescent liquid surface. As discussed in A-5-4, absorption could lead to an underestimation of test gas MIE near the liquid surface unless the rate of test gas introduction is sufficiently high to offset the rate of removal. Table 3-8.1.2 shows solubilities of a selection of gases in a mineral-based transformer oil at ambient temperature and pressure [200]. 

In the pure sodium chloride system with Na20 and low oxide, CO2 seems to be the preferred product at low cds. The relative amount of CO increases by increasing cds, but decreases rapidly when chlorine starts to form. At high oxide contents in the same system CO forms preferably at low cds, but CO2 increases rapidly at high cds. In the calcium oxide-containing systems CO2 is the main product at low oxide contents whereas CO increases very fast with increasing cd in the oxide rich melt, up to the startpoint of chlorine adsorption [3]. 

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Chromatographic techniques, particularly gas phase chromatography, are used throughout all areas of the petroleum industry research centers, quality control laboratories and refining units. The applications covered are very diverse and include gas composition, search and analysis of contaminants, monitoring production units, feed and product analysis. We will show but a few examples in this section to give the reader an idea of the potential, and limits, of chromatographic techniques. 

The previous equation is only valid as long as there is no compositional change of the gas between the subsurface and the surface. The value of E is typically in the order of 200, in other words the gas expands by a factor of around 200 from subsurface to surface conditions. The actual value of course depends upon both the gas composition and the reservoir temperature and pressure. Standard conditions of temperature and pressure are commonly defined as 60°F (298K) and one atmosphere (14.7 psia or 101.3 kPa), but may vary from location to location, and between gas sales contracts. 

The volume fraction would typically be used to represent the make up of a gas at a particular stage in a process line and describes gas composition e.g. 70% methane and 30% Ethane (also known as mol fractions) at a particular temperature and pressure. Gas composition may also be expressed in mass terms by multiplying the fractions by the corresponding molecular weight. 

With a further increase in the temperature the gas composition moves to the right until it reaches v = 1/2 at the phase boundary, at which point all the liquid is gone. (This is called the dew point because, when the gas is cooled, this is the first point at which drops of liquid appear.) An unportant feature of this behaviour is that the transition from liquid to gas occurs gradually over a nonzero range of temperature, unlike the situation shown for a one-component system in figure A2.5.1. Thus the two-phase region is bounded by a dew-point curve and a bubble-point curve. 

When a chemical reaction takes place at the solid surface, we expect a smooth variation in gas composition in the macropores on a scale comparable with the whole pellet, provided the reaction rate is not too high. 

Low Density Gases. A fan may have to operate on low density gas because of temperature, altitude, gas composition (high water vapor content of the gas can be a cause of low density), reduced process pressure, or a combination of such causes. To develop a required pressure, the fan has to operate at a considerably higher speed than it would at atmospheric pressure, and hence it must operate much closer to top wheel speed. Bearing life is shorter, and the fan tends to vibrate more or can be overstressed more easily by a slight wheel unbalance. Abrasion of the blades from dust particles is more severe. Therefore, a sturdier fan is needed for low density gas service. 

The gasification plant is equipped with two Texaco gasifiers, each capable of producing all of the synthesis gas required for operation of the complex. Eastman chose an entrained-bed gasification process for the Chemicals from Coal project because of three attractive features. The product gas composition using locally available coal is particularly suitable for production of the desired chemicals. Also, the process has excellent environmental performance and generates no Hquids or tars. EinaHy, the process can be operated at the elevated pressure required for the downstream chemical plants. 

The thermal conductivity of most materials decreases with temperature. When the foam stmcture and gas composition are not influenced by temperature, the k of the cellular material decreases with decreasing temperature. When the composition of the gas phase may change (ie, condensation of a vapor), then the relationship of k to temperature is much more complex (143,191,198). 

The thermal conductivity of a cellular polymer can change upon aging under ambient conditions if the gas composition is influenced by such aging. Such a case is evidenced when oxygen or nitrogen diffuses into polyurethane foams that initially have only a fluorocarbon blowing agent in the cells (32,130,143,190,191,198-201). 

The permeabUity of ceUular polymers to gases and vapors depends on the fraction of open ceUs as weU as the polymer-phase composition and state. The presence of open ceUs in a foam allows gases and vapors to permeate the ceU stmcture by diffusion and convection dow, yielding very large permeation rates. In closed-ceUed foams the permeation of gases or vapors is governed by composition of the polymer phase, gas composition, density, and ceUular stmcture of the foam (194,199,215,218,219). 

Table 16. Char and Gas Composition from Pyrolysis of Municipal Solid Waste Organics ...

Table 18. Gas Composition and Yield from Integrated Hydrogasification Process at Stage T...

Table 3. Gas Composition Requirements for Substitute Natural Gas and for Power Generation...

The gasification is performed usiag oxygen and steam (qv), usually at elevated pressures. The steam—oxygen ratio along with reaction temperature and pressure determine the equiUbrium gas composition. The reaction rates for these reactions are relatively slow and heats of formation are negative. Catalysts maybe necessary for complete reaction (2,3,24,42,43). 

Table 9. BASF Process Consumptions and By-Product Yields and Cracked Gas Composition, ...

The cracked gas composition is shown ia Table 10 for the water queach operatioa (16). Oae thousand cubic meters of methane and 600 m of oxygen produce 1800 m of cracked gas. If a naphtha quench is used, additional yields are produced, consuming 130 kg of naphtha/1000 of methane... 

The classical experiment tracks the off-gas composition as a function of temperature at fixed residence time and oxidant level. Treating feed disappearance as first order, the pre-exponential factor and activation energy, E, in the Arrhenius expression (eq. 35) can be obtained. These studies tend to confirm large activation energies typical of the bond mpture mechanism assumed earlier. However, an accelerating effect of the oxidant is also evident in some results, so that the thermal mpture mechanism probably overestimates the time requirement by as much as several orders of magnitude (39). Measurements at several levels of oxidant concentration are useful for determining how important it is to maintain spatial uniformity of oxidant concentration in the incinerator. 

Undesirable combustible gases and vapors can be destroyed by heating to the autoignition temperature in the presence of sufficient oxygen to ensure complete oxidation to CO2 and H2O. Gas incinerators are appHed to streams that are high energy, eg, pentane, or are too dilute to support combustion by themselves. The gas composition is limited typicaUy to 25% or less of the lower explosive limit. Gases that are sufficiendy concentrated to support... 

LPG is recovered from natural gas principally by one of four extraction methods turboexpander, absorption (qv), compression, and adsorption (qv). Selection of the process is dependent on the gas composition and the degree of recovery of ethane and LPG, particularly from large volumes of lean natural gas. 

The relationship between the gas composition, austenite carbon content, and temperature is known. For example, a gas in equiUbrium with austenite containing 0.8% C must have the partial pressure ratio / Pco ) comprised of only CO and CO2, then the sum of the partial... 

Many commercial gases are generated by burning hydrocarbons (qv) eg, natural gas or propanes, in air (see Gas, natural Liquified petroleum gas). The combustion process, especially the amount of air used, determines the gas composition. For a given fuel-to-air ratio, the gas composition can be used to determine the water vapor content required to achieve a desired equiUbrium carbon content of the austenite (see Combustiontechnology). 

The equihbrium carbon content of austenite also depends on the alloy content, eg, Cr or Ni of the steel. A given gas composition equiUbrates with a carbon content of the austenite which is different for a plain carbon steel than for an alloy steel. 

The maximum surface carbon content is usually set by the gas composition via the equiUbtium constant. If the gas reaction kinetics deposit carbon at a rate which carmot be equaled by the diffusion of carbon into the steel, then the surface value may be less than the possible equiUbtium value. 

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