Gas components

Natural-gas components include water vapor, carbon dioxide (qv), sometimes hydrogen sulfide, heavier hydrocarbons (qv), methane, nitrogen, small amounts of argon, traces of neon and hydrogen, and helium. The production of pure helium from natural gas requires three basic processing steps (73). 

Process selectivity indicates the preference with which the process removes one acid gas component relative to or in preference to another. For example, some processes remove both hydrogen sulfide and carbon dioxide, whereas other processes are designed to remove hydrogen sulfide only. Thus it is important to consider the process selectivity for hydrogen sulfide removal compared to carbon dioxide removal, ie, the carbon dioxide-to-hydrogen sulfide ratio in the natural gas, in order to ensure minimal concentrations of these components in the product. 

Extensive work has been done on corrosion inhibitors (140), activated carbon use (141—144), multiple absorption zones and packed columns (145,146), and selective absorption and desorption of gas components (147,148). Alkan olamines can also be used for acid gas removal in ammonia plants (149). 

In the first step of the reaction, the acetoxylation of propylene is carried out in the gas phase, using soHd catalyst containing pahadium as the main catalyst at 160—180°C and 0.49—0.98 MPa (70—140 psi). Components from the reactor are separated into Hquid components and gas components. The Hquid components containing the product, ahyl acetate, are sent to the hydrolysis process. The gas components contain unreacted gases and CO2. After removal of CO2, the unreacted gases, are recycled to the reactor. In the second step, the hydrolysis, which is an equhibrium reaction of ahyl acetate, an acid catalyst is used. To simplify the process, a sohd acid catalyst such as ion-exchange resin is used, and the reaction is carried out at the fixed-bed Hquid phase. The reaction takes place under the mild condition of 60—80°C and ahyl alcohol is selectively produced in almost 100% yield. Acetic acid recovered from the... 

A process development known as NOXSO (DuPont) (165,166) uses sodium to purify power plant combustion flue gas for removal of nitrogen oxide, NO, and sulfur, SO compounds. This technology reHes on sodium metal generated in situ via thermal reduction of sodium compound-coated media contained within a flue-gas purification device, and subsequent flue-gas component reactions with sodium. The process also includes downstream separation and regeneration of spent media for recoating and circulation back to the gas purification device. A full-scale commercial demonstration project was under constmction in 1995. 

Physica.1 Absorption. Whereas chemical absorption rehes on solvent reactions to hold acid gas components in solution, physical absorption exploits gas—hquid solubiUties. The amount of absorption for these solvents is direcdy proportional to the partial pressure of the acid gas components. Thus these processes are most appHcable in situations involving high pressure feed streams containing significant concentrations of acid gas components. To favor absorption, lower temperatures are often employed. Some processes require refrigeration. 

Figures 5-9 and 5-10 depict the two most common forms of in-out arrangements. This arrangement is also referred to as a compound compressor. In these applications, the flow out of the compressor is taken through an intercooler and back to the compressor. The arrangement is not limited to cooling because some services use this arrangement to remove and scrub the gas stream at a particular pressure level. Provision for liquid removal must be made if one of the gas components reaches its saturation...

The rod drop monitor is recommended for all non-lubricated compressor applications, because there is no lubricant to act as a buffer to prevent piston-to-cylinder contact on the loss of the wear band. Lubricated com pressors handling gases with traces of water or gas components that can degrade the local lubricant are candidates. Hydrogen compressors should be considered for monitors because hydrogen is a difficult gas in it sc It and may contain trace quantities of water. While sweet gas compressor-, as are found in pipeline service, would normally not be considered a problem, the rod drop monitor may be used to signal a loss of lubricant anti the compressor can be shutdown before damage can occur. 

Bacton Terminal Gas Component Concentration vol.% Relative Pressure Potential Uptake g/g... 

Electrochemistry plays an important role in the large domain of. sensors, especially for gas analysis, that turn the chemical concentration of a gas component into an electrical signal. The longest-established sensors of this kind depend on superionic conductors, notably stabilised zirconia. The most important is probably the oxygen sensor used for analysing automobile exhaust gases (Figure 11.10). The space on one side of a solid-oxide electrolyte is filled with the gas to be analysed, the other side... 

The properties of gas ions are of great importance for the electrical performance of an electrostatic precipitator. They also are very important for particle-charging processes. The size of gas ions is normally such that they can be regarded as gas molecules carrying a single elementary charge. It can even be assumed that ions form a gas component with a very low- partial pressure. Thus, the thermal motion of gas ions is assumed to be similar to that of gas molecules. The most important parameters describing the properties of gas ions are... 

Fourier transform infrared (FTIR) analyzers can be used for industrial applications and m situ measurements in addition to conventional laboratory use. Industrial instruments are transportable, rugged and relatively simple to calibrate and operate. They are capable of analyzing many gas components and determining their concentrations, practically continuously. FTIR analyzers are based on the spectra characterization of infrared light absorbed by transitions in vibrational and rotational energy levels of heteroatomic molecules. 

These processes are based on the solubility of the H2S and/or GO2 within the solvent, instead of on chemical reactions between the acid gas and the solvent. Solubility depends first and foremost on partial pressure and. secondarily on temperature. Higher acid-gas partial pressures and lower temperatures increase the solubility of H2S and CO2 in the solvent and thus decrease the acid-gas components. 

Solvent temperatures below ambient are usually used to increase the solubility of acid gas components and therefore decrease circulation rates. 

To select a process, determine flow rate, temperature, pressure, concentration of the acid gases in the inlet gas, and allowed concentration of acid gases in the outlet stream. With this information, calculate the partial pressure of the acid gas components. 

Dehydration to dew points below the temperature to which the gas will be subjected will prevent hydrate formation and corrosion from condensed water. The latter consideration is especially important in gas streams containing CO2 or H2S where the acid gas components will form an acid with the condensed water. 

Gas Component Net Heating Value Btu/SCF SCF/Gallon Equiv[Pg.251]

The BiodeNOx process is a novel process concept to reduce NO emissions from flue gases of stationary sources like power plants and other industrial activities [1]. The concept combines a wet chemicd absorption process with a novel biotechnological regeneration method. In the wet chemical absorption step, flue gas components are absorbed into an aqueous solution of Fe"(EDTA) (EDTA= ethylme-diamino-tetraacetic acid). The following reactions take place ... 

The gas component, which is the most important form in which matter is found in outer space (up to 98-99%), is dominated by the element hydrogen, which makes up 70% of the mass and 90% of the particles. In ionized form (the H-II regions) the gas can be recognized by its recombination and fluorescence light emission. The hydrogen is mainly present in neutral form (H-I regions), at a mean density of 2x 107 particles per cubic metre and a mean temperature of about 80 K. 

The activation of methane by microwaves has long been a goal of scientists in attempts to convert this natural gas component into higher hydrocarbons valuable in petrochemistry and the chemical industry. Two pathways are being extensively investigated by research groups all over the world ... 

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