Chemistry: physical processes – Physical processes – Agglomerating
Patent
1997-12-16
1999-10-12
Straub, Gary P.
Chemistry: physical processes
Physical processes
Agglomerating
23313R, 422110, 422140, 425222, C05B 1900, C05C 702
Patent
active
059649011
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for detecting clogging in a granulation step of forming granules from a liquid of a molten raw material, such as molten urea. The present invention also relates to a granulation method wherein the feed of a liquid of a raw material to be formed into granules is partially stopped: to a series of sections wherein such clogging has occurred, but the whole apparatus is not stopped, and thereby the method allows continuous operation.
BACKGROUND ART
As the granulation method in a granulation step of forming granules, for example, of urea, and as the method of coating granules, many proposals have been made. For example, the applicant of the present application has proposed a method disclosed in JP-B ("JP-B" means examined Japanese patent publication) No. 63729/1992 as a method for processing large particles of urea. A case of this granulation method is described using a granulator illustrated in FIG. 4, by way of example.
FIG. 4 is a vertical cross-sectional view of a granulator. In this figure, seed crystals of urea are fed into a granulation section 1 through a feed port 2. Molten urea liquid is sprayed at a prescribed angle from nozzles 3 into the granulation section 1. As a result, the above seed crystals of urea are subjected to the spray of molten urea in the granulation section 1 and grow in granule diameter. The grown urea 7 is whirled up into a space 6 by currents for jetting from multiple air feed pipes 5 branched from a lower feed port 4, and the urea 7 is allowed to drop into a space 8. Meanwhile, a fluid for the fluidization is fed from an upper feed port 9, to keep the grown granular urea 7 on a bottom bed 10 in a fluidized state in the space 8, so that the granular urea is fluidized to occupy throughout the space 8 over the nozzles 3. This movement is repeated, and finally the granular urea is discharged from a discharge port 11.
However, in this granulator, sometimes, due to some reason during the continuous operation, the molten urea jetted from the nozzles 3 provided on a line 12, or the grown granular urea 7, adheres to some of outlets 13 of the air feed pipes 5, to prevent the air from being jetted out and to clog the outlets. As a result of the occurrence of the malfunctioned section, the fluidized state in the space 8 becomes turbulent, the granulation
DISCLOSURE OF INVENTION
The present invention has been made with the above circumstances taken into consideration, and the above objects of the present invention have been attained by the following detection method and granulation method.
That is, the present invention provides: pipes, each having an outlet for jetting air into a granulation section, and jetting nozzles, each situated at the center of the air outlet of a said air feed pipe for jetting a liquid of a molten raw material, wherein, in jetting the liquid of the molten raw material from the said jetting nozzles into the granulation section to carry out granulation, pipes, a section for taking up orifice rear pressure is provided in each air feed pipe and is located downstream of the orifice section, and a section for taking up orifice forward pressure is provided upstream of the orifice section, and the said orifice rear pressure is measured, to detect clogging of the air feed pipes based on a change (abnormality) in the pressure difference regarding the air feed pipes. the molten raw material is molten urea. said air feed pipes are grouped into multiple series of prescribed number of air feed pipes, and the pressure difference of the air feed pipes of each series is monitored. the method as stated in the above (1), (2), or (3) to detect an air feed pipe whose pressure difference is abnormal, stopping the feed of a liquid of a molten raw material to the said air feed pipe, and compensating the amount corresponding to the stoppage with the remaining function.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-sectional view showing an embodiment of the granulator used in the present invention.
FIG. 2 is an enlarged cro
REFERENCES:
patent: 3903333 (1975-09-01), Shirley et al.
patent: 4749595 (1988-06-01), Honda et al.
patent: 5013336 (1991-05-01), Kempf et al.
patent: 5108034 (1992-04-01), Houy et al.
Honda Tetsuzo
Kido Kimikazu
Straub Gary P.
Toyo Engineering Corporation
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