Carbon dioxide high pressure

Although the process requires the treated gas to have a certain minimum carbon dioxide partial pressure for removal of sulfurous compounds with liquid carbon dioxide, promising new SNG processes under development produce medium to high carbon dioxide content crude gases ideally suited for acid gas removal via the CNG process (12,13). The novel features of the CNG process have been demonstrated with bench-scale process development units second generation process development units are in various stages of... 

The direct synthesis of ethyleneurea from ethylene glycol, ammonia, and carbon dioxide under pressure was investigated until it became evident that rather high pressures probably would be required. Best results (58% yield) were obtained from a charge consisting of 1 mole of glycol, 8 moles of... 

In normal high pressure liquid chromatography, typical sample volumes are 20-200 p.L this can become as little as 1 nL in capillary HPLC. Pretreatment of the sample may be necessary in order to protect the stationary phase in the column from deactivation. By employing supercritical fluids such as carbon dioxide, pretreatment can be bypassed in many instances so that whole samples from industrial and environmental matrices can be introduced directly into the column. This is due to the fact that the fluid acts as both extraction solvent and mobile phase. Post-column electrochemistry has been demonstrated. For example, fast-scan cyclic voltammo-grams have been recorded as a function of time after injection of microgram samples of ferrocene and other compounds in dichloromethane solvent and which are eluted with carbon dioxide at pressures of the order of 100 atm and temperatures of 50°C the chromatogram is constructed as a plot of peak current vs. time [18]. 

Oxygen is an extremely important gas because it supports combustion. (You will learn more about combustion reactions in Unit 5.) The more oxygen available, the hotter a fire will burn. Pressurized oxygen is used in the manufacture of steel and specialized alloys. In the manufacture of steel, oxygen is used to remove excess carbon by burning the carbon into carbon monoxide or carbon dioxide. High levels of carbon make steel too brittle for many uses. 

Whether corrosive constituents are removed at the oil or gas well or just before they enter cross country lines is a matter of economics (i.e., cost of the line, ease of replacement, etc). When dehydration or gas purification is not performed at the wellhead, severe corrosion may occur. Laboratory data on the corrosion rate vs partial pressure of carbon dioxide (Figure 4.5 in Chapter Four) often do not give a good estimate of the corrosiveness of the fluid because variables other than carbon dioxide partial pressure also affect metal loss. When the gas contains less than 15% oil (corrosion is low when there is more than 15% oil in the gas) and velocities are high, the chemical composition of the water, rather than the carbon dioxide partial pressure, appears to control the corrosion. The pH of the system calculated from the water composition has been used to determine whether or not a well is corrosive. To date, however, there is not a one-to-one correlation between the in situ pH and corrosiveness. 

Stainless steel, mild steel for normal conditions of temperature and pressure. When moist use silver, platinum or tantalum. Moist or dry gas use backed carbon, graphite. High pressure work in heavy black iron pipework. High pressure Monel or aluminium iron bronze valves Low-carbon steel at normal temp, and stainless steel for higher temperatures Steel in the absence of sulphur dioxide contaminants in the gas and at temperatures <65°C. Monel, Inconel, nickel and copper for liquid or gas at elevated temperature... 

Gas cooled reactors use carbon dioxide under pressure as a recirculating heat transfer medium (coolant) between the hot nuclear reactor core and water in a secondary circuit in order to raise steam and electrical power in an otherwise conventional high pressure steam generator/turbine/condenser loop. The role played by ion exchange is denoted by systems A-D in Figure 8.22. 

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). 

Recent work on the carbon dioxide system shows another unusual high-pressure behaviour. Raman spectra of carbon dioxide show that CO2 molecules remain the basis of the phases to more than 40 GPa at temperatures below a few hundred Kelvin [52]. These results, however, do not mean that the molecular crystals are the stable phases indeed, recent studies of the combustion of carbon at high pressures by Yoo et al [53] reach another conclusion. They initiated combustion of a mixture of carbon and oxygen at pressures between 7 and 13 GPa by heating the carbon with a Nd YAG laser, quenching the products to ambient temperature under pressure and recording their Raman spectra. As well as features of unreacted O2 and CO2 in some samples,... 

Carolan MF, Dyer PN, Motika SA, Alba PB. Compositions capable of operating under high carbon dioxide partial pressures for use in solid state oxygen producing devices. U.S. Patent 5,712,220, 27 June 1998. 

One of the earliest explanations offered for the harmful effects was high concentration of carbon dioxide in the immediate vicinity of the decomposing green manure. This is a possibility, since we are concerned with seedlings, and since we know that occasionally the carbon dioxide partial pressure in the soil air may be as high as 5% and possibly higher. There is now less emphasis on this explanation, since others seem to be much more important. 

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 ... 

Enzymes can also be used in supercritical fluids (6,7), the most widely used being supercritical carbon dioxide (critical pressure 31.1°C, critical temperature 7382 kPa). The main difficulty with supercritical fluids, apart from the increased cost imposed by the high-pressure equipment, comes from the fact that properties such as solubility and reaction rates depend strongly on the pressure, making the optimization and operation of processes difficult. 

The caesium and tetramethylammonium derivatives of the unknown a-fluorinated diol CFzfOH), have been isolated following treatment of a slurry of caesium fluoride in acetonitrile with carbon dioxide under pressure ca. 10 atm) or after allowing a solution of tetramethylammonium fluoride in the same medium to absorb carbon dioxide 2M+F 4- COj - CFj(0 M+) (M = Cs or Me N) use of high - CO, pressures (ca. 45 atm) seems to enable the intermediate FCX>, Cs to be isolated. ... 

Figure 16.9 Carbonated beverages. Bottling under a high carbon dioxide partial pressure increases the solubility of the gas in the liquid solution. When you open the bottle, the partial pressure of carbon dioxide above the solution drops to become equal to atmospheric Pcoj> dramatically decreasing the solubility of the gas, which escapes from the solution in the form of gas-phase bubbles that consist of carbon dioxide molecules (and a relatively small quantity of water molecules). 

One interesting application of Hemy s law is the production of carbonated beverages. Manufacturers put the fizz in soft drinks using pressurized carbon dioxide. The pressure of CO2 applied (typically on the order of 5 atm) is many thousands of times greater than the partial pressure of CO2 in the air. Thus, when a can or bottle of soda is opened, the CO2 di.s.solved under high-pressirre conditiorrs comes out of solution— resulting in the bubbles that make carbonated drinks appealing. 

The solid-gas equilibrium line represents those conditions of pressure and temperature where sublimation occurs. For HjO, obvious sublimation occurs at pressures lower than those that are normally experienced. (Sublimation of ice does occur slowly at normal pressures, which is why ice cubes get smaller over time in your freezer. The so-called freezer burn of frozen foods is caused by sublimation of ice from the food. This is why it s important to wrap frozen food tightly.) Flowever, for carbon dioxide, normal pressures are low enough for sublimation. Figure 6.4 shows a phase diagram for CO2, with the 1-atm position marked. Liquid CO2 is stable only under pressure. Some gas cylinders of carbon dioxide are high enough in pressure that they actually contain liquid CO2. 

Schott also investigated the shock Hugoniot of Carbon Dioxide . Shocked states of Carbon Dioxide at pressures from 100 to 300 kbar were measured using high explosives in systems with cryogenically liquefied Carbon Dioxide confined between parallel metal layers. 

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