Method and apparatus for particle agglomeration

Abstract

Fine particles of dust and other pollutants in gas streams are agglomerated to form larger particles which are more easily filtered in downstream processing. In one embodiment, particles in successive portions of the gas stream are charged with opposite polarity, and the gas stream is introduced into an Evase portion (12) to slow it down. Particles of different sizes have differential deceleration and therefore mix generally in the direction of flow, leading to agglomeration of oppositely-charged particles. In another embodiment, a gas stream is divided into substreams in respective parallel passages, and the particles in adjacent passages are charged to opposite polarity. Deflectors at the downstream end of the passages cause substreams of particles of opposite polarity to mix, with resultant agglomeration of oppositely charged particles.

Description

[0001] The invention relates to a method and a device for agglomerating particles, in particular to an electrostatic agglomerator used in air pollution control. Background technique [0002] Many industrial production processes produce small harmful particles that are emitted into the atmosphere. For example, due to the presence of heavy metals and heavy organic materials in coal, toxic by-products of coal combustion suspended in the air tend to aggregate into small particles that are dispersed. Many trace metals, such as arsenic, cadmium, nickel, selenium and their compounds volatilize at high combustion temperatures, and then uniformly nucleate or mainly condense on dust particles as the flue gas cools. Some toxic organic air pollutants are the same. [0003] Toxic particles formed by uniform nucleation are very fine submicron particles. These particles can enter people's respiratory system, so they cause great harm to public health. The definite link between toxicity and breathi...

AI Technical Summary

Problems solved by technology

For particles smaller than 0.1 microns, diffusion is usually the main mechanism of action for particle transport, charging and trapping, however, for particles between 0.1 and 0.2 microns, diffusion, electrostatic and inertial effects are not very strong, known Devices using these principles of action exhibited the lowest collection efficiencies for particles in these size ranges

[0012] The effect of diffusion trapping can be improved by providing a large surface area and / or more time for diffusion to occur, but this requires a substantial increase in device size

Larger inertial forces can be obtained by increasing the relative velocity of the particles relative to the collection surface, but at the expense of larger pressure differences and energy input to the collection device, which will result in a significant increase in cost

Therefore, economic considerations limit the application of these methods

[0013] Other dust collection devices used for fine particle emission control include wet electrostatic precipitators and wet precipitators, which generally require large and expensive equipment and create problems with polluting wastewater

Fiber filters have also been used as dust collectors, but they are generally ineffective collectors for fine particles because these small and often smooth particles tend to flow through the fabric used in such filters

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