Transportation solids

Although the continuous-countercurrent type of operation has found limited application in the removal of gaseous pollutants from process streams (Tor example, the removal of carbon dioxide and sulfur compounds such as hydrogen sulfide and carbonyl sulfide), by far the most common type of operation presently in use is the fixed-bed adsorber. The relatively high cost of continuously transporting solid particles as required in steady-state operations makes fixed-bed adsorption an attractive, economical alternative. If intermittent or batch operation is practical, a simple one-bed system, cycling alternately between the adsorption and regeneration phases, 1 suffice. 

Traii.sfer Meaii.s and Metliod.s iVlotor v ehicles, railroads, and barges are the principal means used to transport solid wastes. Pneumatic and hydraulic systems hav e also been used. 

Mukherjee studied the gas phase equilibria and the kinetics of the possible chemical reactions in the pack-chromising of iron by the iodide process. One conclusion was that iodine-etching of the iron preceded chromis-ing also, not unexpectedly, the initial rate of chromising was controlled by transport of chromium iodide. Neiri and Vandenbulcke calculated, for the Al-Ni-Cr-Fe system, the partial pressures of chlorides and mixed chlorides in equilibrium with various alloys and phases, and so developed for pack aluminising a model of gaseous transport, solid-state transport, and equilibria at interfaces. 

The rubber belt of a bucket elevator, fitted with aluminium buckets and used for transporting solid chlorate, jammed during use. Friction from the rotating drive pulley heated and powdered the jammed belt. A violent explosion consumed all the rubber belt and most of the 90 aluminium buckets. Bronze and steel equipment is now installed. 

The streaming current that is generated while transporting solids is a function of the solids processing method (see Table 7-3) and the flow rate, as shown by... 

Hexachloroethane also enters the environment as part of the waste from companies that make or use it. Vapors can be released to the air during production, use, or transport. Solid wastes containing it are buried in landfills or burned. In landfills, it can dissolve in underground water because it does not bind strongly to soil. Once dissolved, it can reach rivers, lakes, streams, or well water. 

Condolios, E. and Chapus, E.E., Transporting solid materials in pipelines, Chemical Engineering, 70 pp. 93-8 (24 June 1963a). 

CVT makes use of the temperature dependence of the above heterogeneous equilibrium to transport solid A through the vapour phase by means of gaseous intermedi-ate(s) C. That the process involves true transport and not just evaporation and condensation is evident from the fact that solid A does not possess an appreciable vapour pressure at the experimental temperature moreover, transport of A is not observed without the transporting agent B. 

Elemental sulfur1-4 occurs naturally in association with volcanic vents and, in Texas and Louisiana, as underground deposits. The latter are mined by injecting air and superheated water, which melts the sulfur and carries it to the surface in the return flow (the Frasch process). Most of the sulfur used in industry, however, comes as a by-product of the desulfurization of fossil fuels. For example, Albertan sour natural gas, which often contains over 30% (90%, in some cases) hydrogen sulfide (H2S), as well as hydrocarbons (mainly methane) and small amounts of C02, carbonyl sulfide (COS), and water, is sweetened by scrubbing out the H2S and then converting it to elemental S in the Claus process.5 The Claus process is applicable in any industrial operation that produces H2S (see Section 8.5) it converts this highly toxic gas to nontoxic, relatively unreactive, and easily transportable solid sulfur. 

Pipelines to transport solids are called freight pipelines, of which three different types exist pneumatic pipelines, the use of which is known as pneumotransport or pneumatic conveying slurry pipelines, which may also be called hydrotransport or hydraulic conveying and capsule pipelines. When air or inert gas is used to move the solids in the pipeline, the system is called a pneumatic pipeline and often involves a wheeled vehicle inside the pipeline, propelled by air moving through the pipe (25). Slurry pipelines involve the transport of solid particles suspended in water or another inert liquid. Hydraulic capsule pipelines transport solid material within cylindrical containers, using water flow through the pipeline for propulsion. 

H. Liu, "Freight Pipelines for Transporting Solids and Packages," presented at ASCE 1993, Annual Convention andExposition, Dallas, Tex., Oct. 26,... 

Electric or fuel-powered means of transporting solid materials, such as forklift trucks, should be employed only when full consideration has been given to any hazardous atmospheres in which these might be used. Such transport must be properly maintained to preserve the integrity of built-in safety... 

Effects of rifling on four-inch pipe transporting solids. Ibid., 106 135-147. 

In moving-bed transport, solid particles are in contiguous contact with one another and are pushed along by the transporting fluid more or less in plug flow, with a voidage equivalent to that of the loosest fixed bed. The velocity of solids movement can be varied from zero to any practical upper limit. 

Water Transport Barges, scows, and special boats have been used in the past to transport solid wastes to processing locations and to seaside and ocean disposal sites, but ocean disposal is no longer practiced by the United States. Although some self-propelled vessels (such as U.S. Navy garbage scows and other special boats) have been used, most common practice is to use vessels towed by tugs or other special boats. 

Pneumatic Transport Both low-pressure air-vacuum conduit transport systems have been used to transport solid wastes. The most common application is the transport of wastes from high-density apartments or commercial activities to a central location for processing or for loading into transport vehicles. The largest pneumatic system in use in the United States is at the Walt Disney World amusement park in Orlando, Florida. 

Another method to increase the stability of the solution, especially for transport purposes, is to use monomethylol dicyandiamide. This eliminates the need for adding formaldehyde and decreases the polymerization rate during transport. Solid monomethylol dicyandiamide was mixed with solid melamine 111, 112). This solid composition can then be shipped to treating facilities where it is mixed with water and then reacted with phosphoric acid. A similar modification allows dicyandiamide to react with formaldehyde at elevated temperatures until no free formaldehyde exists (iii). The melamine is then added and the solution can be shipped. Both modifications increase the stability of the solution and eliminate the excess formaldehyde. 

Transportation Solid waste disposal Stationary fuel combustion Industrial boilers Utility boilers Industrial processes Miscellaneous sources... 

A coal slurry pipeline is a system for transporting solid coal particles in a liquid carrier. Long-distance coal slurry pipelines are an alternative to railroad transport, and their practicality and economics are largely dependent on land ownership, terrain, water availability and water contamination concerns, political considerations, and coal demand. An example of pipeline transport is the 440 km Black Mesa pipeline, which was completed in 1970 and is currently the only long-distance coal slurry pipeline operating in the United States. Slurry pipelines are also used over shorter distances to transport material within a processing facility. 

Mathieu, P., 1972. Apports chimiques par les precipitations atmospheriques en savane et sous foret. Influence du milieu forestier sur la migration des ions et des transports solides (Bassin d Amitioro, Cote d Ivoire). D. Sci. Thesis, University of Nice, Nice, 441 pp. 

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