Vapor pressure carbon dioxide

Li2C03/K2C03 electrolytes have been used without any significant developments or improvements since Ketelaar and Broers work. The 62/38 eutectic composition has a relatively high volatility, causing the fuel cell to dry out. The partial pressure of MeOH varies with the square root of the water vapor to carbon dioxide vapor pressure ratio ... 

As Figure 5.8 makes clear, solids have vapor pressures, just as liquids do. The same is obvious from Figure 1.9 for water and Figure 5.2 for carbon dioxide. Vapor pressures of solids behave the same as the vapor pressures of liquids. We have fewer data for them, and most of those data are at temperatures at which their vapor pressure is modest, and well represented by the C-C equation. You may not think of wood, steel, or concrete as having vapor pressures. But they do. The values, at normal temperatures, are so low that the evaporation rate is nearly zero, even on a geologic time scale, (Problem 5.25). 

Some values of physical properties of CO2 appear in Table 1. An excellent pressure—enthalpy diagram (a large Mohier diagram) over 260 to 773 K and 70—20,000 kPa (10—2,900 psi) is available (1). The thermodynamic properties of saturated carbon dioxide vapor and Hquid from 178 to the critical point,... 

K, have been tabulated (2). Also given are data for superheated carbon dioxide vapor from 228 to 923 K at pressures from 7 to 7,000 kPa (1—1,000 psi). A graphical presentation of heat of formation, free energy of formation, heat of vaporization, surface tension, vapor pressure, Hquid and vapor heat capacities, densities, viscosities, and thermal conductivities has been provided (3). CompressibiHty factors of carbon dioxide from 268 to 473 K and 1,400—69,000 kPa (203—10,000 psi) are available (4). 

The reactor effluent is rapidly quenched with aqueous mother Hquor in specially designed equipment operating at pressures essentially equal to the reactor pressure. This operation yields an off-gas consisting of ammonia and carbon dioxide vapor and a crystalline melamine slurry saturated with ammonia and carbon dioxide. The slurry is concentrated in a cyclone mill. The mother Hquor overflow is returned to the quenching system. The concentrated slurry is redissolved in the mother Hquor of the crystallization system, and the dissolved ammonia is stripped simultaneously. 

Braune and Strassman8 measured the concentration of iodine in gaseous carbon dioxide at pressures up to 50 atm from 32° to 98°C. They passed the carbon dioxide over an excess of solid iodine and analyzed the effluent mixtures. Their pressures were too low to find the saturation vapor pressures or to show whether or not critical end points were formed. 

A piece of solid carbon dioxide, with a mass of 22.0 g, is placed in an otherwise empty 4.00-L container at 27°C. What is the pressure in the container after all the carbon dioxide vaporizes If 22.0 g of solid carbon dioxide was placed in a similar container already containing air at 740. torr, what would be the partial pressure of carbon dioxide and the total pressure in the container after the carbon dioxide had vaporized ... 

Phenol was successfully extracted from water using pure supercritical carbon dioxide at pressures up to 31 MPa for two isotherms 298 and 323 K. The distribution coefficient increased with increasing pressure, but decreased with increasing temperature. This is expected since increasing the temperature severely drops the carbon dioxide density and hence the solubility of the phenol in it. Increased volatility at the higher temperature is not sufficient to off-set the density effect, since phenol has a low vapor pressure. Benzene was foimd to be a suitable entrainer since its solubility in water is very small and it enhances the distribution of phenol into the supercritical phase. The presence of methanol was found to have no effect. Since methanol is polar and completely soluble in water, it favors the aqueous phase and therefore does not change the characteristics of the supercritical phase. Others have found that the distribution of short chain alcohols between water and supercritical carbon dioxide highly favors the aqueous phase (ifl). 

Some solids, such as iodine and carbon dioxide, vaporize at atmospheric pressure without passing through the liquid state. This process is known as sublimation. Solids exhibit vapor pressures just as liquids do, but they generally have much lower vapor pressures. Solids with high vapor pressures sublime easily. The characteristic odor of a common household solid, j) r -dichlorobenzene (moth repellent), is due to sublimation. The reverse process, by which a vapor solidifies without passing through the liquid phase, is called deposition. 

Bulk containers used for storing liquid carbon dioxide at low pressures should be protected from tampering by unauthorized individuals. If a small enclosed location is used, the outlet from the pressure relief valves must be piped to the outside away from personnel, building air intakes, or other points such that discharge of the carbon dioxide vapor will not result in a high concentration of carbon dioxide. Such piping must not be equipped with valves or other means of stopping the flow of gas. 

No attempt should be made to use carbon dioxide vapor without a pressure-reducing regulator of suitable design and in good condition. 

Carbonation of Electrolyte. Carbon dioxide, which is present in the atmosphere at a concentration of approximately 0.04%, reacts with an alkaline solution (electrolyte) to form an alkali metal carbonate and bicarbonate. Zinc/air batteries can be satisfactorily discharged using a carbonated electrolyte, but there are two disadvantages of extreme carbonation (1) vapor pressure of the electrolyte is increased, aggravating water vapor loss in low-humidity conditions, and (2) crystals of carbonate formed in the cathode stracture may impede air access, eventually causing cathode damage with subsequent deterioration of cathode performance. As indicated in Fig. 13.16 carbonation must be extreme to be detrimental to cell performance in most applications. ... 

Liquid carbon dioxide under pressure is sealed in an evacuated glass tube some vaporizes. 

This carbon dioxide-free solution is usually treated in an external, weU-agitated liming tank called a "prelimer." Then the ammonium chloride reacts with milk of lime and the resultant ammonia gas is vented back to the distiller. Hot calcium chloride solution, containing residual ammonia in the form of ammonium hydroxide, flows back to a lower section of the distiller. Low pressure steam sweeps practically all of the ammonia out of the limed solution. The final solution, known as "distiller waste," contains calcium chloride, unreacted sodium chloride, and excess lime. It is diluted by the condensed steam and the water in which the lime was conveyed to the reaction. Distiller waste also contains inert soHds brought in with the lime. In some plants, calcium chloride [10045-52-4], CaCl, is recovered from part of this solution. Close control of the distillation process is requited in order to thoroughly strip carbon dioxide, avoid waste of lime, and achieve nearly complete ammonia recovery. The hot (56°C) mixture of wet ammonia and carbon dioxide leaving the top of the distiller is cooled to remove water vapor before being sent back to the ammonia absorber. 

Ammonium bicarbonate, also known as ammonium hydrogen carbonate or ammonium acid carbonate, is easily formed. However, it decomposes below its melting point, dissociating into ammonia, carbon dioxide, and water. If this process is carefully controlled, these compounds condense to reform ammonium bicarbonate. The vapor pressures of dry ammonium bicarbonate are shown below (7). (To convert kPa to mm Hg, multiply by 7.5.)... 

Solvent Strength of Pure Fluids. The density of a pure fluid is extremely sensitive to pressure and temperature near the critical point, where the reduced pressure, P, equals the reduced temperature, =1. This is shown for pure carbon dioxide in Figure 2. Consider the simple case of the solubihty of a soHd in this fluid. At ambient conditions, the density of the fluid is 0.002 g/cm. Thus the solubiUty of a soHd in the gas is low and is given by the vapor pressure over the total pressure. The solubiUties of Hquids are similar. At the critical point, the density of CO2 is 0.47 g/cm. This value is nearly comparable to that of organic Hquids. The solubiHty of a soHd can be 3—10 orders of magnitude higher in this more Hquid-like CO2. 

Phase Behavior. One of the pioneering works detailing the phase behavior of ternary systems of carbon dioxide was presented ia the early 1950s (12) and consists of a compendium of the solubiHties of over 260 compounds ia Hquid (21—26°C) carbon dioxide. This work contains 268 phase diagrams for ternary systems. Although the data reported are for Hquid CO2 at its vapor pressure, they yield a first approximation to solubiHties that may be encountered ia the supercritical region. Various additional sources of data are also available (1,4,7,13). 

Fig. 7. Glass-tiansition tempeiatuies of (A) polymetfiylinetfiaciylate (PMMA) ( ) polymetfiylinetfiaciylate-fo-styiene (SMMA60) and ( ) polystyrene (PS) as a function of carbon dioxide pressure, where the solid line represents CO2 vapor pressure (37). To convert MPa to psi, multiply by 145.

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