Advanced Cyclone Systems, S. A.

High efficient cyclone systems with electrostatic recirculation for particulate matter (PM) emission control

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Courtesy of Courtesy of Advanced Cyclone Systems, S. A.

The development of new optimized dedusting systems has particular and increasing relevance for atmospheric particulate emission control. Indeed, traditional 'particulatetraps' present several disadvantages that foster the search for alternative solutions.

Industrial cyclones are, for their robust construction, absence of moving parts and general application, an appropriate technology for emission control when dealing with temperatures as high as those in biomass boilers. Nevertheless, cyclones' relatively low efficiency, particularly for small (< 10 µm) and low density particles, leads many users to complement them with Bag Filters (BF) or Electrostatic Precipitators (ESP). Usually, BFs are financially bearable and very efficient (> 99.9 %), but are maintenance demanding due to frequent change of filter elements. On the other hand, ESPs are robust equipments and are very effective (in a given range of dust resistivity) but their high investment cost is frequently out of reach o fsmall and medium size companies.

Electrostatic ReCyclone® systems appear as an effective alternative to the traditional solutions, since they combine several key advantages of the referred systems, mainly a numerically optimized gas-cyclone geometry (referred as Hurricane) and electrostatic precipitation, allowing biomass boilers to comply with strict legal emissions limits. ReCyclone® systems consist of an optimized reverse-flow cyclone (which can have, by itself, about half of the emissions of other high-efficiency cyclones), combined with partia lrecirculation of un-captured particles via a straight-through cyclone concentrator (recirculator). Particle separation in the recirculator is achieved via the application of a DC electric field combined with centrifugal forces. Global efficiency is further enhanced through a very relevant phenomenon inside cyclones, which is agglomeration/clustering of very fine particles with larger particles in the turbulent flow field inside the gas cyclone.

In order to build a custom made solution for each situation, numerical simulations are made using a model, referred as PACyc, which is based on previously published models to predict collection efficiency either for isolated cyclones, or for cyclones with recirculation. This model considers not only the flow conditions inside the system, but also the particle agglomeration phenomenon. Considering that cyclone efficiency is sensitive to particle size, if the particles 'seem' larger to the cyclone, their calculated efficiency will significantly increase above theoretical predictions.

These systems have been shown, for industrial and pilot scales, to have very high efficiencies when dealing with the emissions of biomass boilers, allowing these to comply with strict emissions policies, and the PACyc model has been proven as a reliable tool to predict the behavior of these kind of systems, for several different configurations, several kinds of dusts and operation conditions.

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