Heat, of absorption

When the exit-liquor temperature rises owing to the heat of absorption of the solute, the value of m changes through the tower, and the liquid-to-gas ratio must be chosen to give reasonable values of miG ilh. and where the subscripts 1 and 2 refer to the bot-... 

When the solute has a large heat of solution or when the feed gas contains high percentages of the solute, one should consider the use of internal coohng coils or intermediate external heat exchangers in a plate-type tower to remove the heat of absorption. In a packed tower, one could consider the use of multiple packed sections with intermediate hquid-withdrawal points so that me hquid coiild be cooled by external heat exchange. 

This, as is shown by the theory, is due to the evolution of the heat of absorption, during solute adsorption at the front part of the peak. Conversely, the back of the peak is eluted at a lower temperature than the surroundings throughout the length of the column due to the absorption of the heat of solute desorption. As a result, the distribution coefficient of the solute at the front of the peak, and at a higher temperature, will be less than the distribution coefficient at the back of the peak, at the... 

Figure 24. Theoretical Temperature and Integral Temperature Curves Obtained from the Heat of Absorption Detector...

Most absorbers require some intercooling between some stages or trays to remove heat of absorption and to provide internal conditions compatible with proper or required absorption. Some temperature rise (10-30°F) is usually designed into the initial conditions. The rise above this must be handled with intercoolers. 

A second approach to the same result involves the same requirements as for a balanced heat design the heat of absorption of the actual components absorbed must equal the sum of the heat added to the lean oil and to the lean... 

Figure 8-60. Component heats of absorption. Used by permission. Hall, R. J., and Raymond, K., Oil and Gas Jour., Nov. 9 (1953) thru Mar. 15 (1954).

Figure 8-60 presents actual total heats of absorption based on experimental studies [32]. As long as the hydrocarbon absorption is in the range of 80-120°F, the values read from the graph should apply. 

Absorption Efficiency, or fraction absorbed Overall tray efficiency, fraction Stripping efficiency, or fraction stripped Fraction of v + li absorbed by the liquid Fraction of loi stripped out of the liquid Mols individual components stripped per hour Total heat of absorption of absorbed components, thousand Btu/day... 

Kremser-Brown-Sherwood Method — No Heat of Absorption, 108 Absorption — Determine Component Absorption in Fixed Tray Tower, 108 Absorption — Determine Number of Trays for Specified Product Absorption, 109 Stripping — Determine Theoretical Trays and Stripping or Gas Rate for a Component Recovery, 110 Stripping — Determine Stripping-Medium Rate for Fixed Recovery, 111 Absorption — Edmlster Method, 112 Example 8-33 Absorption of Hydrocarbons with Lean Oil, 114 Inter-cooling for Absorbers, 116 Absorption and Stripping Efficiency, 118 Example 8-34 Determine Number of Trays for Specified Product Absorption, 118 Example 8-35 Determine Component Absorption in Fixed-Tray Tower, 119 Nomenclature for Part 2, 121... 

High-temperature reactants that can absorb C02 at elevated temperatures in a chemical reaction offer another way to avoid the energy penalties that are associated with creating low operating temperatures or high pressures in the absorption step. In such a system, the heat of absorption is delivered at a temperature that makes it economically attractive. A successful implementation of the injection of reaction-based sorbents will, therefore, require the incorporation of effective process integration schemes to minimize the parasitic... 

Duplessix et al. used water vapor pressure isotherm (i.e., water uptake vs external relative humidity) data combined with simultaneous isotherm differential microcalorimeter analysis to determine the average heat of absorption per water molecule for 1200 EW acid form samples. Hysteresis was seen between sorption and subsequent desorption curves at 25 °C, and nonzero water content remained at zero relative humidity, indicating the presence of tightly... 

Fowkes and co-workers also clearly demonstrated that the physical Interaction of polymers with neighboring molecules was determined by only two kinds of interactions London dispersion forces and Lewis acid-base interactions (21) Calculations based on this concept were shown to correct many of the problems inherent in the solubility approach. They were also able to use the concept to study the distribution of molar heats of absorption of various polymers onto ferric oxides, and thereby more accurately described the requirements for adequate adhesion to steel substrates (21) In the symposium on which this book is based, Fowkes summarized work showing that the polar Interactions between polymers and metal surfaces that are... 

It must be expected that the effect on the heat of absorption will be particularly pronounced at higher pressures and in the middle temperature range, let us say between —170° and 200°. The reason for this is that absorption, which is a slow activated process, will affect the fast adsorption at low temperatures very little. Again at the very high temperatures absorption will be less than adsorption because of its lower heats. On the other hand, at the very high temperatures another absorption process, the endothermic solution, can possibly enter the picture, although this effect is undoubtedly small at low pressures, let... 

The heat of absorption of hydrogen is considerably lower than the heat of chemisorption. 

It is seen from the curves in figure (9) that the heat convected into the detector cell or plate also distorts the curves, It is apparent that, unless the heat lost radially is extremely high, so that little heat is convected to the sensor, symmetrical integral peaks will not be obtained. This heat loss appears impossible to achieve in practice and thus, the heat of absorption detector does no seem viable for LC. 

Solute equilibrium between the mobile and stationary phases is never achieved in the chromatographic column except possibly (as Giddings points out) at the maximum of a peak (1). As stated before, to circumvent this non equilibrium condition and allow a simple mathematical treatment of the chromatographic process, Martin and Synge (2) borrowed the plate concept from distillation theory and considered the column consisted of a series of theoretical plates in which equilibrium could be assumed to occur. In fact each plate represented a dwell time for the solute to achieve equilibrium at that point in the column and the process of distribution could be considered as incremental. It has been shown that employing this concept an equation for the elution curve can be easily obtained and, from that basic equation, others can be developed that describe the various properties of a chromatogram. Such equations will permit the calculation of efficiency, the calculation of the number of theoretical plates required to achieve a specific separation and among many applications, elucidate the function of the heat of absorption detector. 

Glass transition determinations Decomposition reaction Reaction kinetics Phase diagrams Dehydration reactions Solid-state reactions Heats of absorption Heats of reaction Heats of polymerization Heats of sublimation Heats of transition Catalysis... 

The heat of absorption of acetone, ethanol, or ether by nitrocellulose was reported by Calvet [124] ... 

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