Primary absorber

The per pass ethylene conversion in the primary reactors is maintained at 20—30% in order to ensure catalyst selectivities of 70—80%. Vapor-phase oxidation inhibitors such as ethylene dichloride or vinyl chloride or other halogenated compounds are added to the inlet of the reactors in ppm concentrations to retard carbon dioxide formation (107,120,121). The process stream exiting the reactor may contain 1—3 mol % ethylene oxide. This hot effluent gas is then cooled ia a shell-and-tube heat exchanger to around 35—40°C by usiag the cold recycle reactor feed stream gas from the primary absorber. The cooled cmde product gas is then compressed ia a centrifugal blower before entering the primary absorber. 

The vapor from the HPS flows to the primary absorber and the liquid is pumped to the stripper. The HPS is essentially a separation stage with an external cooler located between the primary stripper and absorber. In some units, they are a single tower. 

The HPS overhead vapor contains appreciable amounts of Cj s and heavier components. The primary absorber recovers these components. The HPS vapor enters below the bottom tray and proceeds up the tower contacting absorption oil. Heavy components are absorbed in the oil,... 

To enhance C3+ recovery, some units have installed presaturator drums that function as an additional absorption stage. In this operation, the cooled debutanized gasoline is mixed (presaturated) with the absorber overhead gas. The mixture is cooled and flashed in the presaturator drum. The liquid from this drum is then pumped to the top of the primary absorber. 

The vapor from the primary absorber or the presaturator contains a small quantity of gasoline. The sponge oil absorber recovers this gasoline. Sponge oil is stripped or unstripped light cycle oil. It is used for final absorption of the dry gas stream. Instead of LCO, a... 

The lean sponge oil enters the absorber on the top tray. The gas from the presaturator or from the primary absorber enters below the bottom tray. The rich sponge oil from the bottom is then returned to the main fractionator. The lean gas leaves the top of the absorber to an amine unit for H,S removal prior to entering the refinery fuel... 

The HPS liquid consists mostly of C3 s and heavier hydrocarbons however, it also contains small fractions of Cj s, H2S, and entrained water. The stripper removes these light ends. The liquid enters the stripper on the top tray. The heat for stripping is provided by an external reboiler, using steam or debutanizer bottoms as the heat medium. The vapor from the reboiler rises through the tower and strips the lighter fractions from the descending liquid. The rich overhead vapor flows to the HPS via the condenser and is fed to the primary absorber. The stripped naphtha leaves the tower bottoms and goes to the debutanizer. Usually, at least one draw is installed in the tower to remove the entrained water. 

The debutanized gasoline is cooled, first by supplying heat to the stripper reboiler or preheating the debutanizer feed. This is followed by a set of air or water coolers. A portion of the debutanizer bottoms is pumped back to the presaturator or to the primary absorber as lean oil. The balance is treated for sulfur and blended into the refinery gasoline pool. 

The objective of the primary absorber/stripping towers is to maximize recovery of C3 and heavier components while rejecting and lighter to fuel, C3 is first absorbed and then and lighter components are stripped. Although maximizing C3-C4 recovery for alkylate feed is very profitable, lower recoveries are often accepted to maximize the FCC conversion and/or feed rate. 

In this example, the Hg atom is the primary absorber of light. If the primary absorber is regenerated, it can participate in subsequent cycles, and is called a photosensitizer. In other cases, the photoactive species yields the active species directly. Thus, chlorine molecules can absorb light and dissociate into chlorine atomic radicals ... 

An apparent decrease in the emission quantum yield and/or distortion of the band shape due to the reabsorption of emitted radiation. If such an effect is not corrected or compensated for, results of an emission experiment may prove to be incorrect. This is especially true in fluorescence quenching experiments conducted to evaluate the stoichiometry and affinity of ligand binding. 2. In a light irradiation experiment, the absorption of incident radiation by a species or molecular entity other than the intended primary absorber. See Fluorescence... 

Panchromatic sensitization of vinyl addition polymerization requires the presence of suitable dyes as primary absorbers of radiation. In 1949 Bamford and Dewar (5) reported that styrene could be polymerized by irradiation of a variety of dyes. It was later shown by Koizumi, Watanabe, and Kuroda (6) that these reactions, and others uncovered by the Japanese group, were the result of photoinduced decomposition of the dyes rather than a true sensitization process. 

Table III. CORRELATION COEFFICIENTS FOR IRON ABSORPTION OF THE HOMOLOGOUS SET AT SEVERAL WAVELENGTHS CALCULATED FROM PRIMARY ABSORBANCE DATA AND FROM 1ST AND 2nd DERIVATIVE TRANSFORMS...

Upconversion is included because it is a case, unlike aU the others presented, where the refractive index is not a concern in the design of the material. For upconversion, the important parameters for the designer include absorption bands and excited-state lifetimes. Einding the blank host to hold the emitters and keep them separated from each other is also part of the design task. In addition, this host often serves as the primary absorber of the tight to be upconverted. In the case of Er" ", the host contains Yb for this purpose. 

We have found that a certain number of polyhalogenated aromatic derivatives such as compounds 1-3 greatly accelerate the rate of bleaching of a number of poly silane derivatives in the solid state (33). This effect is dramatically demonstrated in Figure 5 for a PM PS film doped with —20% by weight of l,4-bis(trichloromethyl)benzene, 1. Similar results were obtained with substituted triazine sensitizers such as 2. In these cases, the polysilane is the primary absorber of the incident radiation. Interestingly, when compound 3, which absorbs at —400 nm, was incorporated into a PM PS film and the sample was irradiated at 404 nm, where only the sen-... 

In emission spectroscopy, this refers to the decrease in emission and distortion of the emission band shape by preabsorption of the emitted radiation. In an absorption experiment, this refers to the absorption of incident radiation by the same or a species other than the intended primary absorber. At high concentrations the primary absorber, even if in solution and not stirred, along with any photodegradation products may act as is inner filters. 

The distance of the scatting atoms Rj from the primary absorber. 

EXAFS data analysis consists of varying Eq and the values of—at least—Rj, Nj, and a-j, for each shell of atoms adjacent to the primary absorber, to produce optimum agreement between the experimental and simulated data and their Fourier transforms. 

Therefore, XAS—especially with respect to EXAFS—has many advantages as a probe of transition metal centers in biological materials. Beyond the absence of a requirement for crystalline materials, the major attractions are the specificity, and sensitivity of the technique and the provision of interatomic distances with an accuracy of 0.02 A within (say) 4 A of the primary absorber. However, it should be noted that (1) no angular information is usually obtained (2) rarely does the structural information extend beyond 4 A, (3) the spectrum sums data for all atoms of a particular element and, if the element of interest is present in more than one chemical form, an average environment is obtained (4) the possibility of radiation damage must be anticipated and the integrity of samples should be monitored after, and if possible... 

When the excited states return to the ground state, a photon may again be emitted with an energy equal to or, most often, lower than the energy of the primary absorbed photon. 

Molten lithium metal is a potential candidate for the coolant to be circulated through the blanket. Lithium is a light metal with a low melting point (186 degrees Celsius). In the liquid state, it has a high specific heat and thermal conductivity. These properties make it an excellent heat transfer material and thus, a good choice as a means of removing heat from the reactor. When lithium is used in the blanket for heat transfer it also serves as the primary absorber of the 14,100 keV neutrons from the D + T reaction. 

The depth of vertical mixing may also be directly affected by increased UVR. In many systems (particularly fresh waters), the major component responsible for determining UVR penetration, chromophoric dissolved organic matter (CDOM), is also the primary absorber of visible radiation. Absorption of solar radiation by CDOM results in near-surface heating and shallow stratification [10,11]. However, CDOM absorbance is not constant, due to photobleaching by UVR [12]. As CDOM bleaches, there is deeper penetration of solar radiation and less pronounced surface heating, allowing deeper mixed layers to develop ([13] also see Chapters 3 and 6). 

In summary, information concerning the electronic structure at and/or in the immediate environment about the primary absorbing atom can be obtained by the accurate measurement of ... 

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