Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Reexamination Certificate
1999-04-21
2001-12-11
Atkinson, Christopher (Department: 3743)
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
C165SDIG002, C034S167000, C034S372000, C034S373000, C034S374000, C034S474000
Reexamination Certificate
active
06328099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to drying solid particles and, more particularly, to an apparatus and method for drying solid particles such as fertilizers.
2. Description of Related Art
The manufacture of fertilizers is generally carried out by agglomeration or prilling processes in which particles such as prills or granules of the fertilizer are formed. There are numerous agglomeration and prilling processes known for the manufacture of fertilizers such as ammonium nitrate, urea, potash and phosphates. Agglomeration processes are generally carried out in paddle mixers, pug mills, rotary drums, pans or fluidized beds. Prilling processes are usually carried out in prilling vessels such as prilling towers.
In many cases the fertilizer particles formed in these processes must be dried. Traditional moving bed dryers typically rely upon a large volume of air to purge the solids bed and remove water.
However, traditional moving bed dryers have high capital and operating costs associated with air scrubbing requirements. In addition, conventional moving bed dryers are frequently complex in operation.
U.S. Pat. No. 5,167,274 discloses a method and apparatus for cooling particulate solids. This patent teaches that free-flowing solid particles are cooled in an apparatus comprising a housing containing a multiplicity of parallel, vertical, expanded heat exchanger plates having a cooling fluid therein. However, U.S. Pat. No. 5,167,274 does not disclose the drying of solid particles.
U.S. Pat. No. 3,181,488 discloses a coal drying apparatus that includes vertical hollow plates containing a heated liquid. Air chambers positioned beneath the plates discharge atmospheric air upwardly through coal particles passing between the plates to carry off water vapor. However, U.S. Pat. No. 3,181,488 does not disclose the use of dehumidified gas to dry coal particles.
There is a need for an improved moving bed dryer having reduced air scrubbing requirements, lower operating costs, reduced capital costs and simplicity of operation in drying solid particles.
SUMMARY OF THE INVENTION
The present invention provides a moving bed dryer for drying solid particles and a method of drying solid particles. The moving bed dryer of the invention includes a source of dehumidified gas and at least one heat exchanger plate. Each heat exchanger plate contains an interior fluid flow channel connecting in continuous fashion a fluid inlet and a fluid outlet. In addition, each heat exchanger plate has a gas flow manifold on one end of the plate. Optionally, one or more partial gas flow manifolds located between the ends of a heat exchanger plate can extend across the plate so as to partially constrict the interior fluid flow channel between the fluid inlet and the fluid outlet. Each gas flow manifold and partial gas flow manifold has an inlet connected to the source of dehumidified gas and an outlet consisting of at least one aperture.
In embodiments of the invention, a plurality of parallel and closely spaced heat exchanger plates can be arranged in a bank. The fluid inlet of each heat exchanger plate can be connected to a common inlet header and the fluid outlet of each heat exchanger plate can be connected to common outlet header. Similarly, the inlet of the gas flow manifold and of any partial gas flow manifold of each heat exchanger plate can be connected to a common gas flow inlet header. The bank of heat exchanger plates can be enclosed in a housing. A feed hopper can be attached to one end of the housing in communication with the spaces between the plates. A discharge hopper can be attached to the other end of the housing and in communication with the spaces between the plates. Any suitable mass flow discharge control device will suffice.
According to the present invention, a method of drying solid particles is provided in which free-flowing solid particles are dried by passing the particles adjacent to a heat exchanger plate containing a heated fluid while passing a dehumidified gas into the solid particles from a gas flow manifold and any partial gas flow manifolds in the heat exchanger plate.
In embodiments, solid particles to be dried can be fed into the feed hopper described above and can be carried between the heat exchanger plates by gravity or momentum in a continuous uninterrupted flow to ensure mass flow of the particles in the dryer over the entire cross-section of the dryer between the heat exchanger plates. Dehumidified gas passes through the apertures in the gas manifold(s) into the moving bed of the solid particles to dry the particles. The dried particles can be collected in the discharge hopper and then discharged in a controlled fashion. Drying is aided by heat transfer to the solid particles from a heated fluid in the interior fluid flow channel of each heat exchanger plate.
REFERENCES:
patent: 3092472 (1963-06-01), Figley
patent: 3181488 (1965-05-01), Roe et al.
patent: 3397460 (1968-08-01), Hall
patent: 4141155 (1979-02-01), Benzon
patent: 4424634 (1984-01-01), Westelaken
patent: 5167274 (1992-12-01), Mueller
Hilt George Allen
Thomas Donald Ray
Atkinson Christopher
Mississippi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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