Carbon dioxide pressure-temperature

Figure 9.1. Carbon dioxide pressure-temperature phase diagram adapted from McHugh and Krukonis (1994).

Carbon dioxide pressure-temperature phase diagram. 

Although neither inflammable nor self-igniting, sodium peroxide is highly inflammable when mixed with oxidi2able substances. Such mixtures bum violendy, even ia the absence of air. Tme sodium peroxocarbonates can be formed under the influence of atmospheric moisture and carbon dioxide. At temperatures >50° C and when exposed to pressure or friction, these peroxocarbonates can decompose and generate flame. 

Carbon dioxide gas is added to either the water used to prepare beverages or the symp and water mixture, depending on the type of manufactuting equipment. In both manufactuting processes, the carbon dioxide gas is iatroduced under pressure to the system. The carbonation of the beverage is dependent on the carbon dioxide pressure and the temperature of the mixture. 

Available data on the thermodynamic and transport properties of carbon dioxide have been reviewed and tables compiled giving specific volume, enthalpy, and entropy values for carbon dioxide at temperatures from 255 K to 1088 K and at pressures from atmospheric to 27,600 kPa (4,000 psia). Diagrams of compressibiHty factor, specific heat at constant pressure, specific heat at constant volume, specific heat ratio, velocity of sound in carbon dioxide, viscosity, and thermal conductivity have also been prepared (5). 

It is impossible to have liquid carbon dioxide at temperatures above 31°C, no matter how much pressure is applied. Even at pressures as high as 1000 atm, carbon dioxide gas does not liquefy at 35 or 40°C. This behavior is typical of all substances. There is a temperature, called the critical temperature, above which the liquid phase of a pure substance cannot exist The pressure that must be applied to cause condensation at that temperature is called the critical pressure. Quite simply, the critical pressure is the vapor pressure of the liquid at the critical temperature. 

Provided that the temperature and the carbon dioxide pressure conditions in the calcination furnace are such that they correspond to the point A, or to any point above the calcium carbonate line, no dissociation occurs because in such a situation,... 

The hazard of well blowout is greatest if hydrochloric acid wastes exceeding certain temperature and concentration limits are injected into a carbonate formation. When carbonate dissolves in acid, carbon dioxide is formed. Normally, this gas remains dissolved in the formation waters at deep-well temperatures and pressures, but if the temperature exceeds 88°F or acid concentration exceeds 6% HC1, carbon dioxide will separate from the formation waters as a gas. The resulting gas accumulation can increase pressures to a point where, if injection stops or drops below the subsurface carbon dioxide pressure, a blowout can occur. 

Fig. 16.1. Phase diagram for carbon dioxide critical temperature 31.3°C critical pressure 72.9 atm.

Malinin, S.D. Savelyeva, N.I. "Solubility of Carbon Dioxide in Sodium Chloride and Calcium Chloride Solutions at Temperatures of 25, 50, and 75 C and Elevated Carbon Dioxide Pressures," Geochem. Intern., 1972, 9, (3), 410-18. 

Matsudo s team uses the bacterium Bacillus megaterium in supercritical carbon dioxide at temperatures of about 100°F (40°G) and 100 atmospheres of pressure to bring about carboxylation. The process illustrates yet one more way of using more than one green chemistry principle in a process the use of a safer catalyst as well as a safer solvent. (The role of supercriticial carbon dioxide as a solvent will be discussed in the next section.)... 

Fig. 7. Glass-transition temperatures of (A) polymethylmethacrylate (PMMA) ( ) polymethylmethacrylate-fo-styrene (SMMA60) and ( ) polystyrene (PS) as a function of carbon dioxide pressure, where the solid line represents C02 vapor pressure (37). To convert MPa to psi, multiply by 145.

To a good first approximation, the Great Lakes fit a model involving the equilibrium of calcite, dolomite, apatite, kao-Unite, gibbsite, Na- and K-feldspars at 5°C., 1 atm. total pressure with air of PCo2 = 3.5 X 10" atm. and water. Dynamic models, considering carbon dioxide pressure and temperature as variables (but gross concentrations fixed), show that cold waters contain excess carbon dioxide and are unsaturated with respect to calcite, dolomite, and apatite, whereas warm waters are nearly at equilibrium with the atmosphere but somewhat supersaturated with respect to calcite, dolomite, and apatite. 

Figures 5 and 6 show the results of the calculations, and they are compared with the actual data distribution as shown by a dashed bounding line. With both calcite and dolomite, colder waters match conditions of carbon dioxide pressure greater than atmospheric, and high temperature conditions match carbon dioxide pressure nearly the same as the atmosphere. It appears the degree of mixing and the rate of carbon dioxide diffusion is of prime importance when considering approach to liquid, gas, and solid equilibrium.

The carbon dioxide pressure is only 3.6 bar. From the carbonation chart, assuming a temperature of 20 °C, the volumes carbonation at 4 bar would be 4.3 but only 4.1 at 3.6 bar. Hence, with the presence of ah we have lost 0.2 volumes carbonation. This is the maximum tolerance normally given for volumes carbonation during the manufacture of soft drinks. 

Carbon dioxide removal by slurry absorption is attractive down to about -75°C, a temperature easily achieved by slurry regeneration to slightly above one atmosphere carbon dioxide pressure. For example, with a -75°C exit gas temperature, slurry absorption reduces the carbon dioxide content of a 1000 psia synthesis gas from about 13 to about 4 mole percent, a 70% reduction in carbon dioxide content. The exact level to which carbon dioxide can be removed from a treated gas by slurry absorption also depends on the solubility of solid carbon dioxide in the treated gas the solubility of solid carbon dioxide in synthesis gas (3H2 CO) is illustrated in Figure 10 for several synthesis gas pressures. Fine removal of carbon dioxide to lower levels is accomplished by conventional absorption into a slip stream of the slurry solvent which is regenerated to meet particular product gas carbon dioxide specifications. 

Novoselova I.A., Volkov S.V., Oliinyk N.F., Shapoval V.I. (2003) High -temperature Electrochemical Synthesis of Carboncontaining Inorganic Compounds under Excessive Carbon Dioxide Pressure. J. Mining Metallurgy. 39 (1-2) B, 281-293. 

As the area is diminished below some thousands of sq. A., where the molecules cover only a small fraction of the surface, the surface pressure rapidly becomes much smaller than that of a perfect gas, and in the four acids with the longest chains becomes constant over a considerable region. The curves are indeed a very faithful reproduction of Andrews s curves for the relation between pressure and volume, for carbon dioxide, at temperatures near the critical. The horizontal regions in the curves correspond to the vapour pressure of liquids, and indicate the presence of an equilibrium between two surface phases, the vapour film, and islands of liquid, coherent film. 

Urea is synthesized from ammonia and carbon dioxide at temperatures ranging from 170 to 210 C at pressures between 12 and 30.10 Pa absolute. The present tendency is to use a pressure of about 15.10 Pa absolute. 

In the case of reduction by organic compounds, free carbon, or gaseous carbon monoxide, different courses of the process are possible depending on the partial pressure of carbon dioxide and temperature ... 

An interesting effect is seen when FBSs are exposed to pressures of carbon dioxide. Pressures of between 16 and 50 bar can cause many such systems to become monophasic at room temperature and this may have applications in future separations. Related to this is the use of carbon dioxide pressure as a switch for recycling a fluorous catalyst on a fluorinated silica support. 

The parent methylenecyclopropane (16, R = H) as well as alkylidenecyclopropanes react with carbon dioxide under palladium(O) catalysis to yield furan-2(5//)-ones 17 and 18. Although a complex mixture of cyclotrimers, cyclotetramers and higher oligomers is obtained from the parent MCP, under optimized conditions with regard to the palladium/phosphorus ratio, polarity of the solvent, carbon dioxide pressure and reaction temperature, the [3-f2] cycloadduct 17 (R = H) can be obtained in 80% yield. 

FIGURE A.1 Density variation of carbon dioxide with temperature and pressure. The bold line shows the saturated liquid line (left) and the saturated vapor line (right). The dashed line represents the density at the critical temperature, i.e., 30.978°C (304.128 K). 

Carbon dioxide pressures from 1 to 75 atmospheres and temperatures from 0° to 80°C were assessed. Since the liquid phase is in contact with the coal and is responsible for mineral matter dissolution, its composition would be expected to have a bearing on ash reduction in the coal. The solubility of CO2 in the liquid phase increases as the CO2 pressure increases and may be related to swelling of coal structure (although not linearly). Table I summarizes a set of experiments directed toward determining the effect of aqueous phase concentration of CO2 on the treated product ash content for Pittsburgh Seam coal. At low CO2 concentrations,... 

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