Abstract
The main classes of separators of particulates from gases comprise inertial separators, filters, (wet) scrubbers and electrostatic precipitators, each of which technique has its proper niche and each has its advantages and its disadvantages. In the present paper a new class of equipment, the turbulent flow precipitator (TFP) for gas cleaning is described that, though at the present only in its infancy, is rapidly gaining popularity because it has some advantages over each and every known type of separator and it has very few limitations. TFPs are far more efficient for the removal of fine particles than inertial separators, unlike filters they do not plug up, they do not present secondary disposal problems and they require less maintenance (and are less expensive) than electrostatic precipitators. They can be very efficient also in the submicron range of particle size and there are no practical limitations as far as high temperatures and/or corrosive atmospheres are concerned. They are equally suitable for the removal of solid and liquid particles from gases. Turbulent flow precipitators work on the principle of turbulent eddy penetration into deep regions where there is no net flow, where the eddies die out and where the fine particulates carried by the eddies deposit on collector surfaces. TFPs comprise two well defined regions:- straight, uniform and unobstructed flow passages in which the gas carrying the suspended fine particulates is passed in turbulent flow;- and adjacent collection regions where there is no net gas flow and where all of the separation of particles from the gas takes place. Hence, a TFP is a filter in which the separation of the particulates from the gas takes place outside the passages where the gas flows.
Highlights
The most widely used dry systems for particle separation from air and gases employ filters or electrostatic precipitators for fine dust, fumes, and smoke, mechanical collectors, such as impingers and cyclones, for particles greater than about 5 μm
The author does not know of the existence of any mechanical collector, either in the technical or patent literature, or in practice, that would collect particles of submicron or even micron size with a viable efficiency
The idea for the separation principle was inspired by the paper of Friedlander and Johnstone [3], who showed that from a gas in turbulent flow dust particles of about 1 micron size deposited at a high rate on the wall of a duct coated with a sticky substance
Summary
The most widely used dry systems for particle separation from air and gases employ filters or electrostatic precipitators for fine dust, fumes, and smoke, mechanical collectors, such as impingers and cyclones, for particles greater than about 5 μm. These authors explained that dust particles were carried by turbulent velocity fluctuations, or eddies, into the viscous sublayer adjacent to the duct wall and they continued their path until they collided with the wall and were held there by the sticky coating This mechanism of dust deposition, termed “turbulent deposition”, has been the subject of a number of research papers since the original discovery of Friedlander and Johnstone, but no practical suggestion for utilizing the penetration of eddies into a viscous sublayer for the efficient separation of fine particles from gases has been made until the presentation of Dullien and Collins [1]
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