Gas classification

CAS 630-08-0 EINECS/ELINCS 211-128-3 UN 1016 (DOT) UN NA 9202 Synonyms Carbonic oxide Carbon oxide CO Exhaust gas Flue gas Classification Inorganic carbon compd. 

Synonyms Fire damp Liquefied natural gas LNG Marsh gas Methane Methane, compressed Methane, refrigerated liquid Methyl hydride Natural gas Classification Sat. aliphatic hydrocarbon Empirical CH4... 

Intrinsically safe apparatus and systems are usually allocated a group IIC gas classification, which ensutes that the equipment is compatible with all gas/air mixtures. Occasionally, IIB systems are used, as this permits a higher power level to be used [33]. 

One major difference between DOT and TC regulations was the Canadian use of the Class 2.4, corrosive gas classification. This classification was subsequently retained only for anhydrous ammonia. In 1998, TC discussed revisions to the regulations, and one proposal was the complete elimination of Class 2.4 with anhydrous ammonia to be classified as 2.2 (8). Another significant difference from DOT regulations is the Canadian requirement for pictorial placards and labels the use of words is virtually eliminated. See additional information on hazard classes and divisions in the section on Classification in this chapter. 

Table 8-1 shows the standard numerical code for gas classification called the FTSC code. In... 

Both of these gases are listed as Class A poisons and extremely dangerous by the U.S. DOT. In Canada, they are identified for special treatment within the poison gas classification. Specific information on the safe handling of gases of this type is provided in the individual gas monographs. 

Figure Bl.26.3. The lUPAC classification of adsorption isothemis for gas-solid equilibria (Sing K S W, Everett D H, Haul RAW, Mosoul L, Pierotti R A, Rouguerol J and Siemieiiiewska T 1985 Pure. Appl. Chem. 57 603-19).

As explained in Chapter 8, descriptors are used to represent a chemical structure and, thus, to provide a coding which allows electronic processing of chemical data. The example given here shows how a GA is used to Rnd an optimal set of descriptors for the task of classification using a Kohoncii neural network. The chromosomes of the GA are to be used as a means for selecting the descriptors they indicate which descriptors are used and which are rejected ... 

The GA was then applied to select those descriptors which give the best classification of the structures when a Kohonen network is used. The objeetive function was based on the quality of the classification done by a neural network for the I educed descriptors. 

A new classification of hysteresis loops, as recommended in the lUPAC manual, consists of the four types shown in the Figure below. To avoid confusion with the original de Boer classification (p. 117), the characteristic types are now designated HI, H2, H3 and H4 but it is evident that the first three types correspond to types A, E and B, respectively, in the original classification. It will be noted that HI and H4 represent extreme types in the former the adsorption and desorption branches are almost vertical and nearly parallel over an appreciable range of gas uptake, whereas in the latter they are nearly horizontal and parallel over a wide range of relative pressure. Types H2 and H3 may be regarded as intermediate between the two extremes. 

These simple examples serve to show that instinctive ideas about symmetry are not going to get us very far. We must put symmetry classification on a much firmer footing if it is to be useful. In order to do this we need to define only five types of elements of symmetry - and one of these is almost trivial. In discussing these we refer only to the free molecule, realized in the gas phase at low pressure, and not, for example, to crystals which have additional elements of symmetry relating the positions of different molecules within the unit cell. We shall use, therefore, the Schdnflies notation rather than the Hermann-Mauguin notation favoured in crystallography. 

AWS) has issued specifications covering the various filler-metal systems and processes (2), eg, AWS A5.28 which appHes to low alloy steel filler metals for gas-shielded arc welding. A typical specification covers classification of relevant filler metals, chemical composition, mechanical properties, testing procedures, and matters related to manufacture, eg, packaging, identification, and dimensional tolerances. New specifications are issued occasionally, in addition to ca 30 estabUshed specifications. Filler-metal specifications are also issued by the ASME and the Department of Defense (DOD). These specifications are usually similar to the AWS specification, but should be specifically consulted where they apply. 

Pore size is also related to surface area and thus to adsorbent capacity, particularly for gas-phase adsorption. Because the total surface area of a given mass of adsorbent increases with decreasing pore size, only materials containing micropores and small mesopores (nanometer diameters) have sufficient capacity to be usehil as practical adsorbents for gas-phase appHcations. Micropore diameters are less than 2 nm mesopore diameters are between 2 and 50 nm and macropores diameters are greater than 50 nm, by lUPAC classification (40). 

Health and Safety Factors. Sulfur hexafluoride is a nonflammable, relatively unreactive gas that has been described as physiologically inert (54). The current OSHA standard maximum allowable concentration for human exposure in air is 6000 mg/m (1000 ppm) TWA (55). The Underwriters Laboratories classification is Toxicity Group VI. It should be noted, however, that breakdown products of SF, produced by electrical decomposition of the gas, are toxic. If SF is exposed to electrical arcing, provision should be made to absorb the toxic components by passing the gas over activated alumina, soda-lime, or molecular sieves (qv) (56). 

Rheology. The rheology of foam is striking it simultaneously shares the hallmark rheological properties of soHds, Hquids, and gases. Like an ordinary soHd, foams have a finite shear modulus and respond elastically to a small shear stress. However, if the appHed stress is increased beyond the yield stress, the foam flows like a viscous Hquid. In addition, because they contain a large volume fraction of gas, foams are quite compressible, like gases. Thus foams defy classification as soHd, Hquid, or vapor, and their mechanical response to external forces can be very complex. 

Classification of the many different encapsulation processes is usehil. Previous schemes employing the categories chemical or physical are unsatisfactory because many so-called chemical processes involve exclusively physical phenomena, whereas so-called physical processes can utilize chemical phenomena. An alternative approach is to classify all encapsulation processes as either Type A or Type B processes. Type A processes are defined as those in which capsule formation occurs entirely in a Hquid-filled stirred tank or tubular reactor. Emulsion and dispersion stabiUty play a key role in determining the success of such processes. Type B processes are processes in which capsule formation occurs because a coating is sprayed or deposited in some manner onto the surface of a Hquid or soHd core material dispersed in a gas phase or vacuum. This category also includes processes in which Hquid droplets containing core material are sprayed into a gas phase and subsequentiy solidified to produce microcapsules. Emulsion and dispersion stabilization can play a key role in the success of Type B processes also. 

Fig. 12. Classification of adsorptive separations where NG = natural gas and S = sulfur.

Drilling fluids are classified as to the nature of the continuous phase gas, water, oil, or synthetic. Within each classification are divisions based on composition or chemistry of the fluid or the dispersed phase. 

No method has been devised to estimate with complete accuracy the amount of cmde petroleum that ultimately will be produced from the world s conventional oil and gas fields. Degrees of uncertainty, therefore, should be attached to all such estimates. These uncertainties can be expressed in several ways, the most important of which is achieved by dividing a resource into various categories. Several petroleum resources classifications have been proposed, and a comprehensive discussion of them (1), as well as the definition used in the assessment of the undiscovered resources of the United States (2), have been provided. Seven commonly used categories of resources are given here. 

When constmction is complete, the pipeline must be tested for leaks and strength before being put into service industry code specifies the test procedures. Water is the test fluid of choice for natural gas pipelines, and hydrostatic testing is often carried out beyond the yield strength in order to reHeve secondary stresses added during constmction or to ensure that all defects are found. Industry code limits on the hoop stress control the test pressures, which are also limited by location classification based on population. Hoop stress is calculated from the formula, S = PD/2t, where S is the hoop stress in kPa (psig) P is the internal pressure in kPa (psig), and D and T are the outside pipe diameter and nominal wall thickness, respectively, in mm (in.). 

A recirculation design (Fig. 10) returns the gas to the classifier through the fan after the fine particles are removed from the gas stream. Such an arrangement requires an excellent soHd/gas separator otherwise the classification becomes less efficient. A perfect soHd/gas separator would be a device having a = 1. If the recirculated gas is entered through a secondary coarse stream classification section, then the classification is not less efficient unless the secondary classification is very iaefficient. 

It is quite common ia the designs for fine classification to recontact the coarse stream transversely or ia counterflow with air before dischargiag it (see Fig. 9). This removes dry fine particles not removed ia the primary classification. That is, these particles are swept back iato the feed and given another chance to exit with the fine particles. Such an arrangement iacreases the overall sharpness iadex and reduces the overall apparent bypass. Another variation is to reenter the air from the sohd/gas separation of the coarse stream. 

Gas-phase separations may be classified as enrichment, sharp, or purification separation, depending on the purity, recovery, and magnitude of the pertinent separation. The classification system allows for a certain amount of synergy, as several separation methods may be combined in order to achieve the desired result. Certain separation methods ate favored for each category (26). 

Shipment and Storage. Liquid sulfur dioxide is commonly shipped in North America using 55- and 90-t tank cars, 20-ton tank tmcks, 1-ton cylinders, and 150-lb cylinders. Cylinders made of specified steel are affixed with the green label for nonflammable gases. The DOT classification is Poison Gas, Inhalation Ha2ard. Purchasers of tank-car quantities are required to have adequate storage faciUties for prompt transfer. 

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