Fine particles, solid state

Solids materials that are insoluble in hydrocarbon or water can be entrained in the crude. These are called bottom sediments and comprise fine particles of sand, drilling mud, rock such as feldspar and gypsum, metals in the form of minerals or in their free state such as iron, copper, lead, nickel, and vanadium. The latter can come from pipeline erosion, storage tanks, valves and piping systems, etc. whatever comes in contact with the crude oil. 

The very fine particles of nearly atomic proportions react almost immediately. Because the BaO product hcis an extremely large surface area, the solid state reaction Is not diffusion limited. In the last method (see 4.9.18.), we might use a precipitated product to use as the basis to form the desired compound. We might precipitate ... 

Another observation is that solid state reactions involving very fine particles ought to be very fast in the beginning, but then will slow down as the product particles become larger. There are other properties of particles which we can think of, as follows ... 

Fine particle powders can be produced by various methods, such as micronization or spray drying. The physicochemical nature of these fine particles largely defines the stability of the bnlk powder, which in turn is critical to the long-term effective performance of the dry powder product. The section Fine Particles and the Solid State in this article is an introduction to understanding better the fundamental properties that underlie the behavior of bulk powders. Commentary on the various means of producing fine powders follows in the section Powder Production Formulation and Processing. ... 

Pass gas upward through a bed of fine particles. For superficial (or inlet) gas velocities much in excess of this minimum the bed takes on the appearance of a boiling liquid with large bubbles rising rapidly through the bed. In this state we have the bubbling fluidized bed, BFB. Industrial reactors particularly for solid catalyzed gas-phase reactions often operate as bubbling beds with gas velocities Wq 5 30 u. ... 

POWDER METALLURGY. Powder metallurgy (PM) embraces the production of finely divided metal powders and their union through the use of pressure and heat into useful articles. The temperatures required are below the fusion point of the principal constituent, and bonding depends on interdiffusion of the metal particles in the solid state. It is necessary to provide intimate contact between particles, hence reducing atmospheres are provided in the sintering process to prevent formation of oxide films Readily oxidized powders such as aluminum require special technique. 

SURFACE. In physical chemistry the area of contact between two different phases or states of matter, e.g., finely divided solid particles and air or other gas (solid-gas) liquids and air (liquid-gas) insoluble particles and liquid (solid-liquid). Surfaces are the sites of tire physiochemical activity between the phases that is responsible for such phenomena as adsorption, reactivity, and catalysis, The depth of a surface is of molecular order of magnitude, The term interface is approximately synonymous with surface, but it also includes dispersions involving only one phase of matter, i.e., solid-solid or liquid-liquid,... 

Metal carbonates are often used as reagents in solid-state reactions because heating them creates finely divided metal oxides as a result of the release of C02(g) from the crystal lattice. These finely divided particles, which are made freshly in situ, are often more reactive in heterogeneous solid-state reactions than are the metal oxides found on the laboratory shelf because they have a higher surface area that is more reactive because of its fresh preparation. Determine the minimum temperature necessary to achieve spontaneous thermal decomposition of BaC03. 

In continuous flow, the only point in the tank that must be equal to the feed composition for steady-state operation is the drawoff point. Thus, if the drawoff point is at the bottom, middle, or top of the tank, different average tank compositions can result, even though the composition of the entrance and exit streams are the same. If the mixer is large enough to provide complete uniformity of all the solids, including the coarse particles as well as the fine particles, then the drawoff point does not make any difference in the composition of the tank. However, if the mixer is designed only to just suspend the solids to the drawoff point, then tank compositions vary widely, depending upon the drawoff conditions. 

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