Efficient recovery of food ingredients
after a dryer can be quite challenging, especially for finer particles. The same problem occurs in many milling and micronization applications.
Usual spray drying arrangements
(single point, two point and closed cycle) include 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. Often, 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 5µm, losses due to low cyclone efficiency can rise to more than 25%.
The preferred way to recover these sensitive and expensive products is with cyclone collectors due to their direct and sanitary powder capture. Unlike bag filters or wet scrubbers, cyclones minimize filter or product contamination and product cross contamination and can easily handle a wide range of operating temperature, pressure and moisture conditions.
Product losses due to cyclones' low efficiency represent a high cost
. Cyclones need to be complemented with expensive second stage filters that may not allow for product recovery. Even for a few applications where the losses may not be so costly (less expensive products), they are not environmentally and socially responsible
, with waste or side stream management being an additional problem to tackle.
For the first stage of separation, clients need the highest possible performance since this is where first grade product is captured. ACS tailor designs high efficiency cyclones that maximize yield
, manufactured with full sanitary quality amd equipped with state of the art CIP technology.
Often there is also the need to comply with increasingly stricter emission limits, which vary geographically.
The options for these police filters have different advantages, drawbacks, investment and operational costs.
Clients' needs include
||Regular Cyclones and Multicyclones | Problem: Low Efficiency
+ Low cost, easy to operate and clean. Allow for quick stops and product rotation.
- Low efficiency for small particles (<10μm) leading to non-compliance with emission limits. Regular cyclones available on the market are not an option for emission control.
||Bag & Ceramic Filters | Problem: O&M costs
+ Bag filters are very efficient (> 99.9 %) and guarantee compliance with a wide range of emission limits.
- Demanding in terms of temperature conditions: product can easily stick to the bags if temperature drops.
- CIPable and sanitary bag houses are expensive and maintenance is labour and time consuming.
- For sensitive products such as infant nutrition, lactose or gluten free, etc, product recovered from the bag house may not be considered first grade because of the risk of fiber or cross contamination.
||Wet Venturi Scubbers and WESPs | Problem: Secondary Pollution
+ Can work well for a variety of operating conditions.
- No product recovery possible from a wet scrubber.
- Secondary pollution of water is an operational added problem requiring a water treatment facility.
a highly efficient final dedusting system from where they can recover first grade product, maximizing yield of the whole production line. ACS cyclones can be a real alternative to other police filters depending on the required emission limits and particle size of the product.