Cottrell process

The Cottrell process proceeds in four definite steps ... 

Water in Dust Settlement.—In nearly every case where water can be used it has a beneficial effect. It is of much assistance in the Cottrell process of dust settlement to be described later. The more finely divided the water, the less need be the amount used but that the effect is somewhat independent of the quantity, that is that a large quantity in bulk will do effective work is shown by the experiments of Iles. Jets of water were allowed to flow down through a tin box with slightly inclined alternate shelves so as to give the water a tortuous course. From 90 to 95 per cent of the smoke and fume was collected from the gas ascending the box. Humidifying can be accomplished by nozzles or by centrifugal apparatus, which whirls the water into an impalpable mist. 

The Cottrell Process.—The Cottrell process is a separation by the silent or glow discharge from high-voltage direct current. The electrodes are usually a small pipe about 10 ft. long and 6 in. diam. through the center line of which is... 

The Cottrell process will not throw down SO2 and it apparently only throws down SOs through the formation and precipitation of sulphuric acid. Water helps on many problems. One use has already been mentioned. It has been stated that zinc fumes with the proper amount of water can be handled at temperatures as high as 600 to 700°F. The water must be thoroughly mixed with the fume. Steam also helps in precipitating tin chloride. 

The voltage maintained ranges from 30,000 to 100,000. Owing to difficulties in rectifying large amounts of currents the capacity of panel sets ranges from 5 to 50 kw. The Cottrell process can be worked at temperatures where cloth filtration would be out of the question. 

In addition, many combinations between alumina, magnesia and silica are possible which may render good service under special conditions. As an example, a comxK)si-tion suitable for spark plugs and high-tension insulators used at about red heat, as in the Cottrell process, is as follows ... 

Pump seals and demister wash receive priority on fresh water additions. In the Research-Cottrell process, two demisting stages insure adequate mist removal. Water sprays are mounted below and above the... 

N2, and traces of PH, CO2, E, and S large furnaces generate off-gas at a rate of about 120—180 m /min. In most installations the off-gas is passed through a series of Cottrell electrostatic precipitators which remove 80—95% of the dust particles. The precipitators ate operated at temperatures above the 180°C dew point of the phosphoms. The collected dust is either handled as a water slurry or treated dry. Einal disposal is to a landfill or the dust is partially recycled back to the process. The phosphoms is typically condensed in closed spray towers that maintain spray water temperatures between 20 and 60°C. The condensed product along with the accompanying spray water is processed in sumps where the water is separated and recycled to the spray condenser, and the phosphoms and impurities ate settled for subsequent purification. 

Other plant-scale applications to pollution control include the flotation of suspended sewage particles by depressurizing so as to release dissolved air [Jenkins, Scherfig, and Eckhoff, Applications of Adsorptive Bubble Separation Techniques to Wastewater Treatment, in Lemlich (ed.). Adsorptive Bubble Separation Techniques, Academic, New York, 1972, chap. 14 and Richter, Internat. Chem. Eng, 16,614 (1976)]. Dissolved-air flotation is also employed in treating waste-water from pulp and paper mills [Coertze, Prog. Water TechnoL, 10, 449(1978) and Severeid, TAPPl 62(2), 61, 1979]. In addition, there is the flotation, with electrolytically released bubbles [Chambers and Cottrell, Chem. Eng, 83(16), 95 (1976)], of oily iron dust [Ellwood, Chem. Eng, 75(16), 82 (1968)] and of a variety of wastes from surface-treatment processes at the maintenance and overhaul base of an airline [Roth and Ferguson, Desalination, 23, 49 (1977)]. 

The idea behind this hypothesis is that an early generation of AGBs might have evolved and polluted the interstellar medium with nuclearly processed material, so that the new generations of stars were born from an already contaminated gas (D Antona et al. 1983 Cottrell Da Costa 1981). 

Knauf A process for making gypsum, suitable for use as plaster, from the waste from the Wet Process for making phosphoric acid. Developed by Research-Cottrell. 

SONOX A process for simultaneously removing S02 and NOx from flue-gas. A slurry of lime or limestone, with a proprietary nitrogen-based additive, is injected into the furnace. Developed by Ontario Hydro (the largest electricity supplier in North America) and marketed by Research-Cottrell. 

Although intended primarily for air-conditioning applications, these units have been successfully applied to the collection of relatively nonconducting mists such as oil. However, other process applications have been limited largely to experimental installations. The large cost advantage of these units over the Cottrell precipitator lies in the... 

For the same process, in chronoamperometry, the Cottrell equation holds ... 

A number of vendors offer SNCR technology based on either ammonia or urea. Exxon Mobil Thermal DeNO (TDN) technology is a common SNCR process applied to FCC units. The technology is licensed exclusively to Hamon Research-Cottrell Inc., and has been utilized to achieve postcombustion NO reduction in CO furnaces, thermal oxidizers, overhead regenerators, and power boilers. Thermal... 

Catalyst particle nucleation in the initial stages and their subsequent growth play an important role in catalytic mechanisms. In a model Pt/alumina catalyst, the general view is that the formation of particles is a stepwise process incorporating the following steps (Wynblatt and Gjostein 1975, Cottrell 1971) individual metal atoms (called monomers) transform to two-dimensional islands, which subsequently transform to three-dimensional clusters. These clusters eventually transform into finite-sized particles. 

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