Cottrell electrostatic precipitator

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. 

The generating unit investigated had a 93-megawatt output and went on line in September 1949. The unit contained a pulverized coal, corner-fired furnace with an Aerotec Corp. mechanical ash collection system and a Research Cottrel electrostatic precipitator. At a 93-megawatt output, a steam flow of 810,000 lbs/hr resulted in a gas flow through the electrostatic precipitators of 232,700 cu ft/min (CFM) in the north... 

This study was made at the Thomas A. Allen Steam Plant in Memphis, Tennessee, which has an 870 MW(e) peak capacity from three similar cyclone fed boilers. The plant is part of the TVA power system and was chosen because the Number 2 unit was being renovated. A new Lodge Cottrell electrostatic precipitator was being added so the TVA Power Production Division test sampling crew were available to help sample during compliance testing of the precipitator. 

The gases are quenched at the furnace exit by water or a water.bydrocarbon mixture, rid of tars (Cottrell electrostatic precipitator) and compressed before being sent to the... 

Flue gas leaving the cyclones contains a small r esidual concentration of catalyst and is passed through a Cottrell electrostatic precipitator recovered catalyst is returned to the regenerated-catalyst hopper. Catalyst losses for this type of unit have been reported to be within the range of 0.12 to 0.4 lb. per barrel of feed (232,233). The losses are compensated for by the intermittent addition of fresh catalyst. 

Catalyst recovery. Catalyst losses in downflow units are typically in the range of 0.2 to 0.4 Ib./barrel of feed (100,234). Cyclones recover most of the catalyst from vapors leaving the reaction vessels. Catalyst that escapes from the reactor cyclones is recovered in the bottoms from the fractionating tower. The upflow units and the early downflow units were equipped with Cottrell electrostatic precipitators to recover en-i rained catalyst from the flue gas leaving the regenerator cyclones. It... 

Regenerated catalyst and gas flowed out the top of the regenerator to three cyclone separators connected in series, where, approximately 99.9% of the catalyst was separated from the flue gases and deposited in the regenerated catalyst hopper. The stack gas was then passed through a waste gas fresh feed heat exchanger to a Cottrell electrostatic precipitator where 96-98% of the fine catalyst not separated by the cyclones was recovered and returned by air injection to the inlet of the tertiary regenerated catalyst cyclone. 

Hy ash is usually precipitated by a Cottrell electrostatic precipitator and/or collected in filter bags. The composition of the fly ash usually differs from the bottom ash due to thermal fractionation of the oxides. This is illustrated in Table 2.4 where the composition of the bottom ash is compared with various fractions of the fly ash which is classified into five groups ... 

Gas cleaning may be accomplished either by mechanical methods (such as gravitational settling, centrifugal separation, filtration, ultrasonic precipitators, spray towers, mechanical scrubbers, etc) or by electrical me tbods (such as electrostatic precipitation by Cottrell Method, etc)... 

Pollution control devices for particulates do not depend upon new technology whereas SO2 control does. Since the first decade of this century, as a result of Cottrell s original work (9j, the electrostatic precipitator had been used to collect fly ash particulates. These devices were used on many of the older coal burning plants which had converted to oil. On the reconversion to coal, they were put back in operation or else new ESP units were put in the place occupied by the older ones. The performance of these systems, when designed for a specific coal, was... 

But despite the need and tile invention. Cottrell had considerable difficulty over a number of years in gaining acceptance of the electrical precipitator by industry. Today, and for a number of decades past, the electrostatic precipitator has been a major device for combatting air pollution. Since the precipitator functions only against particulates, numerous other items of air pollution control equipment, such as absorbers, scrubbers, and biters, are required and are described elsewhere in this volume. 

SMOKE. A colloidal or microscopic dispersion of a solid in gas, and aerosol. (1) Coal smoke A suspension of carbon particles in hydrocarbon gases or in air, generated by combustion. The larger particles can be removed by electrostatic precipitation in the stack (Cottrell). Dark color, nausealing odor,... 

Cottrell, Frederick G. (1877-1948). American scientist, inventor of an electrostatic precipitator, now known as Cottrell Precipitator, for smoke, dust fumes. Among other inventions are the pebble bed furnace, boiling point apparatus the Cottrell-Daniels process for fixation of atmospheric nitrogen. Cottrell was Director of US Bureau of Mines Director of the Fixed Nitrogen Research Laboratory, and founder of the Research Corporation, a nonprofit organization... 

A particle removal method commonly used in industry is electrostatic precipitation. Industrial interest in this very efficient scheme can be traced back to 1911 with the investigation of F. Cottrell. His pioneering studies of sulfuric acid mist removal from copper smelter effluents led to the production of the Cottrell precipitator. 

Cottrel s trap an electrostatic precipitator for removing dust from a gas stream... 

Frederick Cottrell invented the electrostatic precipitator, which removes pollutants from smoke. Cottrell was born on Jannaiy 10, 1877, in Oakland, California, the son of Henry and Cynthia Cottrell. His ingenuity and interest in the applied sciences were demonstrated early on. At the age of thirteen, he ran his own printing business with a handpress in the basement of his home, publishing, among other works, a four-page technical magazine. Boy s Workshop. He also earned money from odd jobs as an electrician and landscape photographer. 

Cottrell had struggled to finance the experiments that led to the development of the electrostatic precipitator. Althongh the profits from the eventual manufacture of his precipitator could have made him a wealthy man. 

Research-Cottrell is also supplying a gas cleaning system using an electrostatic precipitator for dry particulate collection followed by a multi-stage gas liquid contactor for sulfur dioxide removal. The first stage is a cyclonic quencher for gas saturation and moderate sulfur dioxide absorption followed by a spray and packed-tower section where the major sulfur dioxide absorption takes place. Again the reagent is applied countercurrent to the gas flow. 

Electrostatic Precipitators The principles and operation of electrical precipitators are discussed in Sec. 17 under Gas-Sohds Separations. Precipitators are admirably suited to the collection of fine mists and mixtures of mists and solid particulates. Tube-type precipitators have been used for many years for the collection of acid mists and the removal of tar from coke-oven gas. The first practical installation of a precipitator by Cottrell was made on sulfuric acid mist in 1907. Most older installations of precipitators were tube-type rather than plate-type. However, recently two plate-type wet precipitators employing water sprays or overflowing weirs have been introduced by Mikropul Corporation [Bakke,/. Air Pollut. Control Assoc., 25, 163 (1975)] and by Fluid Ionics. Such precipitators operate on the principle of making all particles conductive wnen possible, which increases the particle migration velocity and collection efficiency. Under these conditions, particle dielectric strength becomes a much more impor-... 

---