Alkali systems

In such systems as (M, Mj (i/2))X (M, monovalent cation Mj, divalent cation X, common anion), the much stronger interaction of M2 with X leads to restricted internal mobility of Mi. This is called the tranquilization effect by M2 on the internal mobility of Mi. This effect is clear when Mj is a divalent or trivalent cation. However, it also occurs in binary alkali systems such as (Na, K)OH. The isotherms belong to type II (Fig. 2) % decreases with increasing concentration of Na. Since the ionic radius of OH-is as small as F", the Coulombic attraction of Na-OH is considerably stronger than that of K-OH. 

Kaplan, N. "Summary of Utility Dual Alkali Systems" presented at EPA Flue Gas Desulfurization Symposium,... 

It is proposed that in mixed organic base-alkali systems, the presence of the organic base changes the solid-liquid equilibrium and stabilizes larger sol-like aluminosilicate species ( 25 m/ ). The alkali ion affects agglomeration of the sol particles to larger amorphous precipitate particles from 100 to 500 min size which subsequently crystallize to zeolite. 

After Abe s work the problem again lay dormant for a number of years until it was taken up by Wilmarth and his co-workers. Claeys, Baes, and Wilmarth (29) in 1948 reported that a liquid ammonia solution of potassium metal rapidly catalyzed o-p H2 conversion, a half-time in solution of 37 sec. being obtained at —53°. In order to establish that this result was due to dissolved metal and not to amide ion impurity, Claeys, Dayton, and Wilmarth (30) studied the o-p H2 conversion in the presence of potassium amide in liquid ammonia. Rates were obtained comparable with those occurring with the metal solution. The mechanism of the conversion was different for the two cases, however, since the amide solution also catalyzed exchange between gaseous deuterium and liquid ammonia, while the metal solution did not. It was assumed that the metal acted by a paramagnetic mechanism and the amide ion by a chemical mechanism. In the same note Claeys, Dayton, and Wilmarth (30) reported confirmation of Wirtz and Bonhoeffer s results on the aqueous alkali system and questioned the validity of Abe s objections. 

Effects of Magnesium and Chloride Ions on Limestone Dual Alkali System Performance... 

Kaplan, N., "Summary of Utility Dual Alkali Systems," In Proceedings Symposium on Flue Gas Desulfurization, Las Vegas, Nevada, March 1979, Volume II, EPA-600/7-79-167b (NTIS... 

Dual alkali systems have been extensively applied to scrubbing SO2 from boiler flue gas. In most of these applications, the objective in using a dual alkali system as compared to a single alkali system, is to minimize the use of the more expensive sodium as compared to the calcium in lime. However, the most cost-effective operation for the system on the MPF is one that will eliminate the expensive drying process. The design shown in Figure 1 may actually require considerably more alkali than... 

The principal advantage of a dual alkali process applied to the MPF is the substitution of a relatively inexpensive filtering step for the expensive drying step in the single alkali system. 

In the triphenyhnethanides, the metal is coordinatively and electronically saturated by the encompassing crown ether that occupies an equatorial plane around the metal, as well as by the axially located HMPA donors. This favorable cation coordination enviromnent is well established in alkaline earth metal chemistry. The hgands are free to adopt the most conformationally stable orientation, and steric demands force the rings away from planarity and in both the strontimn and barium systems the rings display the familiar propeller geometry, comparable to that seen for related alkali systems. 

Dynamic Interfacial Tension. Crude-oil-alkali systems are unusual in that they exhibit dynamic interfacial tension (Figure 11). A solution of 0.05 wt% sodium hydroxide in contact with David Lloydminster crude oil initially produces ultralow values of IFT. A minimum value is reached, after which IFT increases with time by nearly 3 orders of magnitude, measured in the spinning drop tensiometer. Taylor et al. (57) showed that dynamic inter-facial tension can also occur in crude-oil-alkali-surfactant systems. Figure 11 shows interfacial tension versus time for a solution containing 1 wt% sodium carbonate, and the same solution containing 0.02 wt% of Neodol 25-... 

We have chosen 78 Rb among all alkali systems because of its spectroscopic characterics (Fig. 2) [Bacher 1932 Lindgard 1977 Gallagher 1994], In particular, 78 Rb has no hyperfine structure (its nuclear spin is 0) which ensures that the ground level 5s is degenerate this is necessary for the projection scheme as we shall see below. Moreover it has a long enough lifetime (r 17.66 min) for the proposed experiment. 

The dual alkali process has been tested extensively at laboratory, pilot plant, and prototype levels using lime (calcium hydroxide) as the source of calcium for the regeneration reactions (1). The performance of the process in these test programs prompted the federal Environmental Protection Agency (EPA) to select it for a full-scale demonstration plant. This lime-based dual alkali system has been installed on a 300 MW boiler at Louisville Gas and Electric s Cane Run Station. The system is currently undergoing a one-year test program. 

It must be pointed out that the use of the term "active sodium" is simply one of convenience since it is only an indirect indication of the absorptive potential of the liquor. S02 is actually absorbed by or reacts with the sulfite or bicarbonate ions rather than the sodium ion. Also, even though the bisulfite cannot absorb any S02, it can be regenerated to sulfite (as will be discussed later) and, therefore, it is a potentially active species. The limestone dual alkali system operates at "active sodium" concentrations of 1.1 to 1.7 M. 

The presence of sodium sulfate and sodium chloride is principally the result of secondary absorption reactions. Sodium sulfate is formed by the oxidation of sodium sulfite via reaction with oxygen absorbed from the flue gas. Oxidation also occurs in other parts of the system where process solutions are exposed to air however, the amount of oxidation is small relative to the oxidation which occurs in the absorber. At steady state, the sulfate must leave the system either as calcium sulfate or as a purge of sodium sulfate at the rate at which it is being formed in the system. Although a practical limit for the level of oxidation that can be tolerated by the limestone dual alkali system has not yet been established, it appears that oxidation rates equivalent to 15 to 20% of the S02 removed might be accommodated without intentional purges of sodium sulfate. 

Power Consumption. The power consumption by the dual alkali system ranged from 2.5% (0.53 MW) at flue gas rates equivalent to a boiler load of 21 MW, to 5.3% (0.42 MW) at an equivalent load of 8 MW. 

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