Microwave heated fluidized bed reactor having stages

Details Microwave heated fluidized bed reactor having stages Microwave heated fluidized bed reactor having stages

1982-05-03

1984-10-09

Kyle, Deborah L.

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Fluidized bed

422142, 422143, 422146, 422159, 422186, 42218629, 422903, B01J 826, B01J 842, B01J 1908

Patent

active

044760981

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a fluidized bed-type heating reactor and, more specifically, such a fluidized bed-type heating reactor which is so structured as to receive in the fluidized bed formed therein a watercontaining substance to be heat-treated such as an uranyl nitrate solution for example, and for heat-treatment of the substance, apply microwaves thereto.
2. Background Art
Fluidized bed-type heating reactors generally comprise a column provided therein with a dispersion plate, on which formed is a fluidized bed into which a substance is introduced for heat-treatment, and for means for heating, they rely on hot air which is supplied under pressure from below the dispersion plate.
Where a reactor of the mentioned type is utilized in or for a process in which present is a high water-content condition and which as a whole comprises a process of an enthalpy ruled rate, it is technically and/or economically difficult to meet the whole of a required heat quantity solely by means of hot air, and it therefore is required to provide an additional or auxiliary heating means.
One example of such enthalpy-ruled rate processes is the denitration reaction process that constitutes a part or portion of reprocessing of spent nuclear fuels. This reaction process is for converting by pyrolysis an uranyl nitrate solution to uranium oxide with moisture and NO.sub.x gas liberated, and the heat quantity required in this case is of the order of 2000 Kcal/KgU, approximately. Thus, with fluidized bed-type heating reactors conventionally employed for the mentioned-type denitration reaction, employment is made for their heating means of a so-called external heating system which utilizes for example a resistance heater disposed on the outer wall of the reactor. A difficulty with such external heating system resides in that the supply of the required heat quantity cannot be made with ease and at a high efficiency. That is to say, according to the heating system in reference a certain limit exists with respect to the heat transfer area, and it therefore is indispensable to determine and select for employment an optimal means for supplying the required heat quantity. Particularly, when a scaling-up is contemplated of an existing reactor so as to have the amount of treatment or the capacity for treatment increased, the selection of heating means is difficult to make. Further, in maintaining high the temperature of this portion of the reactor wall which corresponds to the location of the fluidized bed so as to secure a sufficient heat application as desired, another problem is posed relating to the anticorrosion of the structuring material of the reactor; also, in accordance with an increase in the heat release toward outside the reactor, heat loss is increased. Furthermore, to raise high the temperature of the wall of the reactor tends to produce a difficulty in connection with the particle-size control of UO.sub.3 powder to be formed; besides, it is then likely due to a poor heat conduction attributable to a temporary flow failure of the fluidized bed that the fluidized bed undergoes agglomeration, caking and so forth, whereby the serious trouble is generated of the reactor being made inoperable.
In view of the above, it may be devised to employ an internal heating system in which the heating means for example a resistance heater is provided inside the reactor column, but insofar as the substance to be treated contains a radioactive component, unavoidable is to prevent the radioactive substance from being externally leaked, whereby structural difficulties are involved in this case again from the viewpoint of maintenance and replacement of the heater. In addition, particularly in the case of generally employed cylindrical fluidized beds, a dimensional limitation cannot be avoided of the internal heater in order to maintain a good fluidized condition of the bed forming particles, whereby if an increase is made of the heat transfer area, the effect thereof cannot fully be exhibited.
In view of the

REFERENCES:
patent: 2977194 (1961-03-01), Loeding et al.
patent: 4221680 (1980-09-01), Hardwick et al.
patent: 4247518 (1981-01-01), Charlet et al.
patent: 4399106 (1983-08-01), Ueda
Lynch, E. P., "The Use of Microwave Energy in Conjunction with Fluidized Bed Reactors", prepared for 3rd International Conference of Environmental Problems of the Extractive Industries, Dayton, Ohio, Nov. 29, 1977.
Botterill, J. S. M., Fluid-Bed Heat Transfer, Academic Press, N.Y., N.Y. (1975), pp. 132-133.
Perry, R. H. and C. H. Chilton, Chemical Engineers' Handbook, 5th ed., 1973, McGraw-Hill, NY, pp. 20-72.

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