Liquid classification

Clear-liquor advance from what is called a double draw-off crystallizer is simply the removal of mother liquor without simultaneous removal of crystals. The primary action in classified-fines removal is preferential withdrawal from the crystallizer of crystals of a size below some specified value this may be coupled with the dissolution of the crystals removed as fines and the return of the resulting solution to the crystallizer. Classified-product removal is carried out to remove preferentially those crystals of a size larger than some specified value. In the following discussion, the effects of each of these selective removal functions on crystal size distributions will be described in terms of the population density function n. Only the ideal solid-liquid classification devices will be examined. It is convenient in the analyses to define flow rates in terms of clear liquor. Necessarily, then, the population density function is defined on a clear-liquor basis. 

It is clear, however, that a s is not quantitatively equal to a because the macrostructural looseness (A) of the polymer in the two cases is not the same A for (Sty), x(DVB)x is given by [(1/x)1 3 — (l/x)o 3], as defined in Eq. 20, whereas A for the non-crosslinked polymer varies with the class of liquid, which determines y and the distribution of the self-associated domains that comprise y as noted above. It may be possible, however, to establish a quantitative relationship of a with oc9 for a given class of liquids, which could then be used in turn to establish the corresponding a/ocs for other P-L systems in that liquid classification. 

Because of the way Figure 2.6 reveals the various couplings and decouplings that can be encountered in ionic liquid media, we have used it as a basis for ionic liquid classification. We divide ionic liquids into ideal, subionic (or poor ionic) liquids, and superionic liquids. The subionic liquids may still be good conductors at ambient pressure because their fluidities are high, but the conductivity is much lower than if all the moving particles were cations or anions. 

Table 1 Ignitable liquid classification scheme (adapted from ASTM E1618) ...

Z THE MIXTURE-MODEL APPROACH TO LIQUIDS CLASSIFICATIONS BASED ON LOCAL PROPERTIES OF THE MOLECULES... 

The timescale is just one sub-classification of chemical exchange. It can be further divided into coupled versus uncoupled systems, mutual or non-mutual exchange, inter- or intra-molecular processes and solids versus liquids. However, all of these can be treated in a consistent and clear fashion. 

Figure C2.2.7. Schematic illustrating tire classification and nomenclature of discotic liquid crystal phases. For tire columnar phases, tire subscripts are usually used in combination witli each otlier. For example, denotes a rectangular lattice of columns in which tire molecules are stacked in a disordered manner (after [33])...

Schemes for classifying surfactants are based upon physical properties or upon functionality. Charge is tire most prevalent physical property used in classifying surfactants. Surfactants are charged or uncharged, ionic or nonionic. Charged surfactants are furtlier classified as to whetlier tire amphipatliic portion is anionic, cationic or zwitterionic. Anotlier physical classification scheme is based upon overall size and molecular weight. Copolymeric nonionic surfactants may reach sizes corresponding to 10 000-20 000 Daltons. Physical state is anotlier important physical property, as surfactants may be obtained as crystalline solids, amoriDhous pastes or liquids under standard conditions. The number of tailgroups in a surfactant has recently become an important parameter. Many surfactants have eitlier one or two hydrocarbon tailgroups, and recent advances in surfactant science include even more complex assemblies [7, 8 and 9].

Acrolein is a DOT Flammable Liquid having subsidiary DOT hazard classifications of Poison B and Corrosive Material. It is also an inhalation hazard that falls under the special packaging requirements of 49 CER 173.3a. 

DMF can be purchased ia steel dmms (DOT 17E, UNlAl, 410 lbs net = 186 kg), tank tmcks, and railcars. On Oct. 1, 1993, new regulations in the United States were estabUshed for DMF under HM-181 the official shipping name is /V, /V- dim ethyl form am i de (shipping designation UN 2265, Packing Group III, Flammable Liquid). Formerly, it was classified as a Combustible Liquid in bulk quantities, but as "Not Regulated" in dmms (49 CFR). International overseas shipments have an IMCO classification of 3.3. 

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. 

Shipping and Storage. MSA is shipped in tank tmcks and in plastic 55-gaHon dmms or smaller containers with polyethylene inserts. The freight classification is Alkyl Sulfonic Acid, Liquid 8 Corrosive Material, UN 2586, Chemical NOIBN. 

Ethyl alcohol is a flammable Hquid requiring a red label by the DOT and Coast Guard shipping classifications its flash point is 14°C (Tag, closed cup). Vapor concentrations between 3.3 and 19.0% by volume in air are explosive. Liquid ethyl alcohol can react vigorously with oxidi2ing materials. Ethyl alcohol has found wide appHcation in industry, and experience shows that it is not a serious industrial poison (273—275). If proper ventilation of the work environment is maintained, there is Httle likelihood that inhalation of the vapor will be ha2ardous. 

For fully developed incompressible cocurrent upflow of gases and liquids in vertical pipes, a variety of flow pattern terminologies and descriptions have appeared in the hterature some of these have been summarized and compared by Govier, Radford, and Dunn Can. J. Chem. Eng., 35, 58-70 [1957]). One reasonable classification of patterns is illustrated in Fig. 6-28. 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

Various types of filter media and the materials oi which they are constructed are surveyed extensively by Purchas Industrial Filtration of Liquids, CRC Press, Cleveland, 1967, chap. 3), and characterizing measurements (e.g., pore size, permeabihty) are reviewed in detail by Rushton and Griffiths (in Orr, op. cit., chap. 3). Briefer summaries of classification of media and of practical criteria for the selec tion of a filter medium are presented by Shoemaker (op. cit., p. 26) and Purchas [Filtr Sep., 17, 253, 372 (1980)]. 

NFPA 497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1997 edition. National Fire Protection Association, Quincy, MA. 

Classification of gases, chemical vapour and volatile liquids... 

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