The vertical force acting on a single sphere was measured and the fluidizing conditions of the fluidized bed with suspended packings were studied.
(1) The vertical force (F) acting on a single sphere which was hung in a fluidized bed was measured by a strain gage. At low gas velocity (near minimum fluidization), F was mainly determined by the apparent buoyancy and downward force arising from stagnant solids on the sphere. And with the increase in gas velocity, it was shown that this was gradually influenced by the drag force of moving solids.
(2) The fluidizing conditions of the fluidized bed with suspended packings were studied by changing the diameter and density of the packings. It was found that the boundary of the packed fluidized bed (PFB) and suspended packing fluidized bed (SPFB) could be expressed by W_p/W_s=1 where W_p and W_s are the weight of suspended packings and fluidized particles, respectively. In SPFB, the left hand side in the preceding equation must be less than unity and the density of the packing should be less than the mean density of the bed. The pressure drop of SPFB(ΔP′) was accounted for by the following equation:
ΔP′=ΔP(W_p/W_s+1) where ΔP is the pressure drop of a conventional fluidized bed (FB). And minimum fluidized velocity of SPFB(u_mf′) could be expressed experimentally by u_mf′=m^(V_p/V_s)u_mf for D_p≥25.4mm. 0<(V_p/V_s)≤(V_p/V_s)* m is calculated by logm=log(1-ε_p)/(V_p/V_s) where D_p, V_p, V_s, (V_p/V_s)*, m, u_mf and ε_p are the diameter of suspended packing, volume of suspended packings, volume of fluidized particles, boundary value of PFB and SPFB, constant, minimum fluidized velocity of FB and void fraction of PFB, respectively. Also, It was observed experimentally that the bed expansion of SPFB was less than that of PFB.

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Nowadays, air pollution is a serious social problem caused by the remarkable progress of industries, rapid increase of automobile and concentration of population. Air pollution must be solved through some kinds of means. Under such circumstance, Electrostatic Precipitator (E. P.) is valuable to prevent from air pollution. In spite of high reputation of E. P., they entail several problem, such as:
(1) The limited applications caused by the electrical resistivity of dusts.
(2) The large scale of plants.
(3) The expensive equipment costs.
If E. P. will be accomplished a more compact design and a more high efficiency, it must possibily grows almighty precipitator. However, collecting efficiency of E. P. may be influenced significantly with electrical resistivity of dusts. Then we observed some phenomena on the collecting electrode through T. V. camera with a microscope, and confirmed three points enumerated hereunder;
(1) Re-entrainment of low resistivity dust, like carbon black.
(2) The irregular flow of the surface dust of moderate resistivity.
(3) The strange behavior of high resistivity dusts, such as sulfur and glass beads.
So we made up some compact trial models with an original scraper to remove the dust deposit. The first point is the compact design of the E. P. This achieved by the short distance of 16mm between the corona wire and flat plate collecting electrode, and by using fine corona wires of 0.15mm in diameter. In order to simplify the test, we used the voltage of positive direct current of 10kV from selen rectifire, so the electric field strength and current density are high, as compared with an industrial E. P. and two-stage air cleaner. Another point is scraping. The capacity of the E. P. depends considerably upon the adhesiveness in the dust layer on the collecting electrode and its removing system. We selected a method to scrape directly along the surface of the electrode, even in the case when carbon black and sulfur were collected on the electrode in thin layer. Scraping is primitive and intricate method but reliable for such unmanegeable dust. We put talc, sulfur dust and the carbon black exhausted from Diesel engine to the test. The results of the tests were rather satisfactory. We have dawn of hope for the application of E. P. to the Diesel engine.

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