Process and spray drying apparatus for producing stable particle agglomerates
AssigneeA/S Niro Atomizer
InventorsJan Pisecky, Soren P. Hansen
Life of this patent
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Abstract
Agglomeration is improved in a straight-through spray drying process by adjusting the location for introduction of recycled fine particles to the atomization zone. The fine particles are dispersed in a minor portion of the drying air and adjustment of the location for the introduction of the fine particles is made so as to change the average distance from the wheel to the area where the fine particles meet atomized droplets or partly dried particles. A spray drying apparatus in which the fine particles are recycled through the use of turnable deflectors, telescopic connections or swivel joints which are suitable for achieving the improved agglomeration.
Claims9
In a process for spray drying liquids containing dissolved or suspended solids to produce stable particle agglomerates, wherein the liquid is atomized in a drying chamber by means of an atomizer wheel to form droplets which are sprayed from said wheel along substantially outwardly directed paths;
- a stream of drying air encircling the atomizer wheel is conducted against the ejected droplets in directions predominantly axial with respect to said wheel and transversely to the paths of these droplets, whereby the droplets are dried to form a particulate material;
- recovering said particulate material;
- separating said recovered particulate material to recover at least a finest fraction thereof;
- and pneumatically recycling said finest fraction to the drying chamber upstream of said atomizer wheel to collide with ejected partly dried sticky particles, the improvement which comprises:
- (i) introducing said recycled finest particles fraction into the stream of drying air before it meets the ejected partly dried droplets;
- (ii) dispersing and entraining said finest dried particles fraction in a minor portion only of the stream of drying air;
- (iii) causing said entrained finest particles to transversely collide with the partly dried droplets at a predetermined distance from the wheel, and
- (iv) adjusting the location for the introduction of said finest particles to adjust said predetermined distance, of the place for collision, from the wheel as a function of the characteristics of the liquid being spray dried and the spray drying operational parameters, whereby to obtain agglomerates of a desired size and structure.
A spray drying apparatus comprising a drying chamber (3) having an atomizer wheel (5) therein for ejecting droplets of the liquid to be sprayed dried into the drying chamber, drying gas dispenser means (2) for providing a stream of drying gas around the atomizer wheel and predominantly transversely to the paths in which the droplets are ejected from the wheel, means to pass said drying gas containing spray dried particles entrained therein to a particle separator, a particle separator (11) for recovering at least the finest spray dried particles from the drying gas, and means for recycling these finest particles to the drying chamber, wherein said means for recycling the finest particles comprise at least one pipe (20) debouching in the drying chamber (3) at a location which, when the apparatus is in operation, is within the stream of drying gas, upstream of the area where said drying gas meets the ejected droplets, and so located that said finest particles are entrained within said drying gas and intersect the paths of said ejected droplets after said droplets are partially dried;
- and means for adjusting the location for the debouching of said at least one conduit whereby adjusting the distance between the place where the recycled finest particles entrained in drying gas collides with the ejected droplets and the atomizer wheel periphery.
Dependencies are inferred from the claim text.