Particularly, the concentration of catalyst after the FCC regenerator is usually over 150 mg/Nm3. Since these levels of emissions didn't represent any environmental harm in the past, they were not controlled by any separator or filter. Plant managers main concern was to clean a fraction of the gas to produce energy in a Turbo Expander, or similar, while concentrating the rest of the pollutant in a dirty gas fraction and releasing it to the atmosphere.
With stricter emission limits, plant managers have to control catalysts emissions and therefore need a very robust particle collection system, capable of withstanding temperatures of many hundreds of degrees, while being more cost effective than expensive sinterized filters. The system shall be placed immediately after the regenerator or after the particle separator upstream of the turbo expander.
Client's needs include a low maintenance cyclone system efficient enough to comply with regulatory PM limits, thus avoiding the use of a filter.
Spray Drying | General Arrangement
Usual spray drying arrangement (single point, two point and closed cycle) includes a high efficiency cyclone and a bag filter.
The cyclone serves the purpose of separating and collecting the dried powder originated in the spray drying chamber. In the vast majority of the cases, the fraction of product escaping to the bag filter is not considered as first grade product, and thus seen as losses. The main reasons for this are contamination with filter fibers, product cross contamination and risk of heat degradation.
For fine powders with a median diameter in volume (MVD) of less than 5 µm, losses due to low cyclone efficiency can rise to more than 25 %
Fluid Bed Drying | General Arrangement
In fluidized bed arrangements, cyclones are used to recover the fine fraction of the dried powder, collecting or returning it to the bed.
This fraction frequently has a very small particle size distribution which results in low yields in the cyclone.
Improving the efficiency is crucial both to recover first grade product and to reduce filter bag cleaning and frequent change of bags.
Client needs include a cyclone system efficient enough in order to replace the bag filter and comply with regulatory emission limits.