Surface temperature, hydrocarbon

Catalysts in this service can deactivate by several different mechanisms, but deactivation is ordinarily and primarily the result of deposition of carbonaceous materials onto the catalyst surface during hydrocarbon charge-stock processing at elevated temperature. This deposit of highly dehydrogenated polymers or polynuclear-condensed ring aromatics is called coke. The deposition of coke on the catalyst results in substantial deterioration in catalyst performance. The catalyst activity, or its abiUty to convert reactants, is adversely affected by this coke deposition, and the catalyst is referred to as spent. The coke deposits on spent reforming catalyst may exceed 20 wt %. 

Sometimes vessels need special water protection to keep the vessel walls cool during fires. High surface temperatures can result in metal failure at pressures far below the vessel s maximum allowable working pressure (M AWP) with potentially disastrous consequences. In hydrocarbon spill fires unprotected vessels (no insulation or water spray) can fail within minutes. 

Surface temperature of exposed equipment may pose the most readily available ignition source in a hydrocarbon facility. Hot surfaces should be insulated, cooled or relocated, when they pose a threat of ignition, to hydrocarbon release areas. Required equipment should be rated to operate below the autoignitiion temperature of the gas or vapor that may be encountered. 

For example, gas mixtures were prepared containing 3.8 mg. per liter of 2,2-DMB in oxygen-nitrogen mixtures ranging from 10 to 60% 02. The percentage of the hydrocarbon which was oxidized was determined over a catalyst surface temperature range of 400° to 900°C. (Figure 3). 

Data for 2,2-dimethylpropane are plotted in Figure 7 for comparison with n-hexane and 2,2-DMB because 2,2-dimethylpropane gave the highest ion yield of the hydrocarbons studied. Little oxidation of 2,2-dimethylpropane in 60% 02 occurred until the platinum surface temperature... 

The chemisorption of over 25 hydrocarbons has been studied by LEED on four different stepped-crystal faces of platinum (5), the Pt(S)-[9(l 11) x (100)], Pt(S)-[6(l 11) x (100)], Pt(S)-[7(lll) x (310)], and Pt(S)-[4(l 11 x (100)] structures. These surface structures are shown in Fig. 7. The chemisorption of hydrocarbons produces carbonaceous deposits with characteristics that depend on the substrate structure, the type of hydrocarbon chemisorbed, the rate of adsorption, and the surface temperature. Thus, in contrast with the chemisorption behavior on low Miller index surfaces, breaking of C-H and C-C bonds can readily take place at stepped surfaces of platinum even at 300 K and at low adsorbate pressures (10 9-10-6 Torr). Hydrocarbons on the [9(100) x (100)] and [6(111) x (100)] crystal faces form mostly ordered, partially dehydrogenated carbonaceous deposits, while disordered carbonaceous layers are formed on the [7(111) x (310)] surface, which has a high concentration of kinks in the steps. The distinctly different chemisorption characteristics of these stepped-platinum surfaces can be explained by... 

Global Warming An increase in the near-surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to a theory that warming occurs as a result of increased use of hydrocarbon fuels by man. See Climate Change (Greenhouse Effect). ... 

A hydrocarbon dew point meter uses a chilled-mirror instrument by which almost invisible films, having sensitivities on the order of 1 ppm, become detectable. Optical fibers are used to detect the reduction of light intensity, and miniature thermocouples measure the surface temperature of the mirror. For total hydrocarbon measurement, the flame ionization analyzer is reliable and accurate, but it requires the attention of operators and also consumes compressed gases. 

A variety of solvents have higher boiling points than that of water but do not have polar structures. The most accessible of these are the hydrocarbons, which come in a series from the smallest (methane) to higher homologs (ethane, propane, butane, and so on) and are abundant in the solar system. Methane, ethane, propane, butane, pentane, and hexane have boiling points of about 109, 184, 231, 273, 309, and 349 K, respectively, at standard terran pressure. Thus, at a mean surface temperature of 95 K, methane (which freezes at 90 K) would be liquid, implying that oceans of methane could cover the surface of Titan. 

SO2, NOx, and total hydrocarbons. The mass spectrometric gas analysis is on a wet basis, as water vapor is not condensed out of the gas, while the analyzers at the sample port measure a gas stream dried using a permeation tube and refrigeration-type dryers in series. In addition to the measurements described above, surface temperature measurements of the boiler skin are made to estimate radiation losses, using the skin temperature, the room temperature and tabulated heat loss factors based on the temperature difference. Particulate mass emission rate and carbon content are measured for heat and mass balance purposes. At present, material deposited within the boiler during a test is collected but not factored into the heat or mass balances, because this deposition is considered to be negligible. Data taken are used to examine the heat balance for the 20-hp system. 

It is important to assess the need to implement further atomic and molecular reactions into the modeling. Our knowledge about the re-erosion yields of deposited layers has to improved urgently. A better understanding of hydrocarbon molecules and radicals is needed, in particular with respect to layer formation and material transport. The atomic data bases needed for the spectroscopic determination of impurity fluxes has to be improved for a critical re-evaluation of erosion yield measurements in tokamaks. The behaviour of mixed material systems (C, Be, W, etc.) deserves special attention. The data base about the dependence of chemical erosion on surface temperature, plasma flow density and ion energies needs to be consolidated. Finally the benchmarks of the numerical models with dedicated experiments must be one of the prime tasks of ongoing experiments. 

Biogenic VOC and NO emissions are calculated on-line based on land use data, simulated surface temperature and radiation. Anthropogenic emissions of primary pollutants, like NOx, SO2, and hydrocarbons, as well as emissions of primary particulate matter have to be supplied either at hourly intervals or as yearly data from gridded emission inventories. Validation studies with MCCM have shown its ability to reproduce observed meteorological quantities and pollutant concentrations for different conditions and regions of the Earth (Forkel and Knoche 2006 Forkel et al. 2004 Grell et al. 1998, 2000 JazcUevich et al. 2003 Kim and Stockwell 2007 Suppan and Skouloudis 2003 Suppan and Schadler 2004 Suppan 2010). 

Near rich limits of hydrocarbon flames, soot is sometimes produced in the flame. The carbonaceous particles—or any other solid particles— easily can be the most powerful radiators of energy from the flame. The function k(t) is difficult to compute for soot radiation for use in equation (21) because it depends on the histories of number densities and of size distributions of the particles produced for example, an approximate formula for Ip for spherical particles of radius with number density surface emissivity 6, and surface temperature is Ip = Tl nrle ns) [50]. These parameters depend on the chemical kinetics of soot production—a complicated subject. Currently it is uncertain whether any of the tabulated flammability limits are due mainly to radiant loss (since convective and diffusive phenomena will be seen below to represent more attractive alternatives), but if any of them are, then the rich limits of sooting hydrocarbon flames almost certainly can be attributed to radiant loss from soot. 

A hydrocarbon adsorber system [1], which has been used for reduction of cold-start hydrocarbons, adsorbs the hydrocarbons in the initial period of cold-start. Generally, the adsorber system is consisted of adsorber followed by light off catalyst. As the surface temperature of the adsorber is heated up, the adsorbed hydrocarbons are released slowly from the surface, and then converted to inert gases by oxidation reactions on adsorber or light-ofF catalyst. 

A heavy hydrocarbon oil with heat capacity, Cp = 0.55 Btu/(lb °F), is being cooled in a countercurrent double-pipe heat exchanger from Tj = 210°F to T2 = 170°F. The oil flows inside a tube at the rate of 8000 Ib/h and the inside tube surface temperature is maintained at 60°F. The overall heat-transfer coefficient,... 

At a reduced pressure of 0.01 atm methane (CH4) is a dominant hydrocarbon species when the temperature is below 1200 K. Then, acetylene (C2H2) becomes dominant when the temperature is increased to 1300 K. It is believed that acetylene is one of the main surface reactive hydrocarbons playing an important role in... 

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