Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1984-12-07
1986-04-01
Camby, John J.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 10, 34 57C, F26B 300, F26B 308, F26B 1700
Patent
active
045788766
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process and an apparatus for spraying a powder with liquid and more especially to spraying a powder with liquid in a mixing vessel.
Previously an apparatus for spraying a powder with liquid has included a mixing vessel having an inlet duct in an upper portion, a spray zone portion including radially arranged spraying nozzles for producing a spray of liquid droplets and an outlet duct in a lower portion, together with a feeding means and a collecting means. In operation powder is entrained in air and conveyed by the feeding means into the inlet duct of the mixing vessel at an optimum throughput rate in the range of 100 to 20,000 kg/hour of powder, then the powder entrained in air is sprayed with liquid droplets emanating from the spray nozzles in the spray zone after which the sprayed powder is collected in the collecting means. To accommodate the powder entrained in air necessitates that the feeding means includes relatively larger diameter ducting and piping because of the velocity of the entraining air. Additionally the dimensions of the mixing vessel need to be correspondingly large so as to accommodate a relatively large volume of air having a high velocity to promote mixing of the powder entrained in air with the liquid droplets, and to provide a reduction in the velocity of the entraining air. Also the collecting means needs to be correspondingly large in dimensions so as to effect separation of the sprayed powder and the entraining air. Consequently such an apparatus is relatively large in overall dimensions thus having a relatively high capital cost. Additionally it is uneconomic to operate the apparatus at rates outside the optimum throughput rate, for example when a relatively small through rate of 50 kg/hour of powder is required.
It has now been found possible to provide a technically simpler apparatus which is structurally more compact and has relatively smaller overall dimensions. Thus having a relatively lower capital cost. Additionally the apparatus has been found to be economic to operate for throughput rates in the range of 20 to 100 kg/hour of powder.
According to the invention there is provided a process for spraying a powder with liquid including the steps of introducing a powder having an average particle size in the range of 1 micron to 1.0 mm as a stream into an upper region of a mixing vessel, effecting within the mixing vessel entrainment of the powder stream in air, spraying the powder entrained in air with liquid in a spray zone of the mixing vessel, and collecting the sprayed powder. According to the invention there is also provided an apparatus for spraying a powder with a liquid including a mixing vessel having aligned axially an upper portion including an inlet duct, a lower portion including an outlet duct, and a spray zone intermediate the upper and lower portions, a feeding means for feeding powder into the inlet duct of the mixing vessel having an outlet duct axially aligned with the inlet duct and the spray zone of the mixing vessel, a venturi device axially aligned within the upper portion of the mixing vessel intermediate the inlet duct and the spray zone arranged to effect entrainment of the powder in a stream of air, and a spray nozzle axially aligned within the spray zone arranged to direct a spray of liquid into the stream of air and entrained powder.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagramatic drawings in which:
FIG. 1 represents an apparatus for spraying a powder with liquid including a mixing vessel mounted on a vibrating fluidized bed chamber; and
FIG. 2 represents in section the mixing vessel represented in FIG. 1.
With reference to FIGS. 1 and 2 an apparatus 1 for spraying a powder with liquid includes a mixing vessel 2 having extending coaxially a cylindrical upper portion 4 having an axially aligned inlet duct 6, an intermediate portion 8 including an apertured domed upper region 10 and a downwardly diverging frusto conical region 12, and a cylindrical low
REFERENCES:
patent: 321512 (1885-07-01), Mathewson
patent: 2413420 (1946-12-01), Stephanoff
patent: 2837467 (1958-06-01), McClure
patent: 3042526 (1962-07-01), Spiess, Jr. et al.
Cartwright William J.
Lyne Christopher W.
Babcock Spraymixer Limited
Camby John J.
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