Absorption process Accelerator

An example of industrial relevance is the removal of sulfur dioxide (S02) from vent gases by absorption into water or a lime slurry (48). In the water absorption process, both gas-film and liquid-film resistance to mass transfer occurs. As a result the overall mass transfer rate is proportional to gas-flow rate and acceleration but inversely proportional to liquid-flow rate. Due to the fast reaction of S02 with lime, this system is only gas-film diffusion limited. The overall mass transfer rate is largely unaffected by gas- or liquid-flow rate and is proportional to acceleration, but to a lesser extent than the water absorption process. In both cases the overall mass transfer rate is reportedly much higher than the corresponding conventional packed towers. 

It has been found [69] that, at 77 K in vitreous ethanol, methanol and MTHF, the process kinetics demonstrates a close to linear dependence of the concentration of the MP+. .. CC14 pairs on the logarithm of the observation time, t, which is characteristic of electron tunneling reactions. The process rate increases dramatically upon illuminating the solutions in the absorption bands of MP+ (kmax 400 and 700 nm) or CC14 (Xmax 365 nm). The mechanisms of the process acceleration upon illumination in the absorption bands of MP+ and CC14 have proved to be essentially different. 

Binding of causative agents of enteric infections and their protein toxins by Silics, as well as its antisecretory properties and ability to enhance absorption processes in bowels, give rise to its high efficacy in the treatment for infectious diarrheas. Thus, addition of Silics (at a daily dose of 100-250 mg kg-1) to the basic therapeutic complex makes it possible to accelerate (by 2-3 days) the positive dynamics of symptoms in patients and, as a result, to attain a shortening of their hospital stay. Besides, administration of Silics leads to a decrease in the necessary amounts of agents for dehydration therapy and prevents development of bacteria carrying states (Table 6). 

The literature on gas-liquid reactions has mainly dealt with gas-absorption processes, in which the reaction is applied as a means of accelerating the absorp>-tion. The reactions used in these absorption processes are very fast, as can be seen from some typical k-values, selected from a paper by Sharma and Danckwerts [5] given in Table 6.3.d-l. With such fast reactions y is large and it is often justified to consider the reaction to be completed in the film. But from Table 6.3.d-2 (Barona [6]) which gives characteristic parameters of important industrial gas-liquid reactions, it follows that quite often y is much smaller than one. 

Skin usually acts as an effective barrier against the entry of most chemicals (i.e., inorganics), however, cuts and other abrasions can accelerate any absorption process. Depending on conditions, absorption of organic chemicals may or may not be realised easily as outlined above even some organic chemicals can enhance absorption of others through the skin (e.g., dimethyl sulfoxide (DMSO)). 

One such possibility consists in the acceleration of contaminant hydrolysis. Hydrolytic detoxification in an alkaline medium is known to be several orders of magnitude faster than that in a neutral medium. Therefore, one can cover underwater places of contaminant burial with any solid alkaline reagent, which will create an alkaline medium in the zone of the contaminant s location. Requirements for such a reagent are rather simple. It should be very poorly soluble in sea water, have a considerable specific surface area (no less than 50 m /g), display clearly defined alkaline properties and be a nontoxic, low-priced, and easily available substance. I believe that chemists-technologists working in the fields of silicate industry, metallurgy, and absorption processes already understand that a wide variety of well-known materials, including some industrial wastes, comply with the above requirements. 

Some toxic agents can also be absorbed by the skin. Since skin is permeable, toxic gases can be absorbed and can be distributed by the blood stream quickly through skin penetration. Cuts and other abrasions can accelerate the absorption process. 

It is also clear from Figure 1 that the presence of nanoclay significantly affects the water absorption process. In fact, both the moisture diffusivity and maximum moisture content of the nanocomposite materials were found to increase. (It should be noted that the y-axis limit of Fig. lb is double that of Fig. la.) It is possible that the presence of the clay promotes the creation of miCTopores at the interface area between the polypropylene matrix and the clay particles, thus accelerating the water absorption process and improving the diffusion phenomena [8]. Moreover, owing to the hydrophiUc nature of the clay, the nanocomposite materials would be expected to absorb moisture at a higher rate and in larger amounts than the neat PP. 

The printing of newspapers is conducted at very high speeds, often reaching 3000 feet per miaute. AH three printing processes utilize similar quaHty newsptint which, essentiaHy, is made of groundwood or thermomechanical pulp. Presses are fed a continuous web of newsptint that unwiads from a feed roUer. Inks dry by absorption of Hquid iato the porosity of the substrate. Some evaporation of water ia a flexo pubHcation ink can accelerate the dryiag process. 

A number of processes have been developed using hot potassium carbonate plus an activator. The activator, which may be DEA, boric acid, or a hindered amine, serves to accelerate the rate of absorption, thus reducing absorber and regenerator sizes. Catacarb, Benefield, and Flexsorb HP are examples of proprietary processes of this type. 

Gases and liquids may be intentionally contacted as in absorption and distillation, or a mixture of phases may occur unintentionally as in vapor condensation from inadvertent cooling or liquid entrainment from a film. Regardless of the origin, it is usually desirable or necessary ultimately to separate gas-liquid dispersions. While separation will usually occur naturally, the rate is often economically intolerable and separation processes are employed to accelerate the step. 

While carburisation itself is not a normal corrosion process, in that there is no metal wastage, absorption and diffusion of carbon can lead to significant changes in the mechanical properties of the affected material and in particular to marked embrittlement. Furthermore, initial carburisation can produce an acceleration of the normal oxidation process, a phenomenon that is notable in nickel-chromium alloys. 

An initial solution was prepared by dissolving metallic niobium powder in 40% hydrofluoric acid. The dissolution was performed at elevated temperature with the addition of a small amount of nitric acid, HN03, to accelerate the process. The completeness of niobium oxidation was verified by UV absorption spectroscopy [21]. The prepared solution was evaporated to obtain a small amount of precipitate, which was separated from the solution by filtration. A saturated solution, containing Nb - 7.01 mol/1, HF - 42.63 mol/1, and corresponding to a molar ratio F Nb = 6.08, was prepared by the above method. The density of the solution at ambient temperature was p = 2.0 g/cc. Concentrations needed for the measurements were obtained by diluting the saturated solution with water or hydrofluoric acid. 

Three test batches of a chemical were manufactured with the intention of validating the process and having a new product to offer on the market. Samples were put on stability under the accepted ambient (25°C, 60% relative humidity) and accelerated (= stress 40°C, 75% rh) conditions cf. Section 4.20. One of the specification points related to the yellowish tinge imparted by a decomposition product, and an upper limit of 0.2 AU was imposed for the absorption of the mother liquor (the solvent mixture from which the crystalline product is precipitated) at a wavelength near 400 nm. 

Maldotti (96) studied the kinetics of the formation of the pyrazine-bridged Fe(II) porphyrin shish-kebab polymer by means of flash kinetic experiments. Upon irradiation of a deaerated alkaline water/ethanol solution of Fe(III) protoporphyrin IX and pyrazine with a short intense flash of light, the 2 1 Fe(II) porphyrin (pyrazine)2 complex is formed, but it immediately polymerizes with second-order kinetics. This can be monitored in the UV-Vis absorption spectrum, with the disappearance of a band at 550 nm together with the emergence of a new band due to the polymer at 800 nm. The process is accelerated by the addition of LiCl, which augments hydrophobic interactions, and is diminished by the presence of a surfactant. A shish-kebab polymer is also formed upon photoreduction of Fe(III) porphyrins in presence of piperazine or 4,4 -bipyridine ligands (97). 

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