There are several types of filter-thickener now available in commercial scale, but in this experiment, we studied the fundamental characteristics of the simplest type of filter-thickener as shown in Fig. 1. This filter-thickener consists of a cylindrical settling tank (50cm in diameter and 90cm in depth) with perforated floor covered with a filter medium. (Poly-vinyl chloride filter cloth).
A part of the liquid contained in the sludge sedimented on the bottom of the settling tank is withdrawn as filtrate through the filter cloth by liquid head and suction of the gear pump. The cake sludges on the filter cloth are scraped and gathered to the centre of the tank bottom and withdrawn by the reciprocating diaphragm pump as thickened sludges. Overflow, underflow and filtrate are all sent back to the reservoir, where they are mixed by the stirrer, and recirculated by the pump.
After a long and continuous running under constant feed-, underflow- and filtration-rate conditions. the whole system comes to its equilibrium. Then the concentration distribution of slurry along the height of the settling tank and the underflow concentration are measured. The results obtained are shown in Table 1 and Fig. 5.
According to our study of the capacity of the ordinary continuous thickener, the concentration C_u of underflow sludge is determined mainly by the underflow rate per unit settling area (Q_u/A) and the settling characteristics of that slurry. Solid flux G which may settle down across a horizontal unit area of the slurry layer with a concentration C, is represented by the equation, G=C(R+Q_u/A), where R is a settling velocity of slurry having a concentration C and Q_u/A is a downward bulk flow of liquid induced by the withdrawal of underflow. As shown in Fig. 6 (dotted curve), solid flux G at a constant rate Q_u/A takes a minimum value G_m at a certain value of C(C_mu), and the slurry layer of that concentration controlls the capacity of the thickener.
From the material balance, the underflow concentration to be obtained under this condition may be calculated by means of the following equation.
G_m=C_mu(R_cmu+Q_u/A)=C_uQ_u/A
In the filter-thickener, besides the underflow Q_u, the filtrate Q_ff is withdrawn from the bottom of the tank. Therefore the downward bulk flow of liquid in the lower part of the settling tank becomes (Q_u+Q_ff)/A.
If the sum of Q_u and Q_ff is designated by Q_u', solid handling capacity in the settling part of the filter-thickener is the same as that of ordinary thickener with an underflow rate Q_u'. Then if all the sludge (Q_u') but no filtrate is withdrawn as underflow, the concentration of the underflow sludge becomes C_u' in Fig. 6.
If Q_u (one part of Q_u') is withdrawn as underflow and Q_ff (=Q_u'-Q_u) as filtrate, the concentration of the thickened sludge becomes C_u2 in Fig. 6. In other words, the volume of sludge decreases from Q_u' to Q_u, and solids contained remain the same, so the sludge concentration increases from C_u' to C_u2 which equals C_u'×Q_u'/Q_u. Accordingly, when corrected values of observed C_u2 at various operating conditions are plotted as C_u2Q_u2/Q_u' against

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The mechanism of through-flow drying of pasty materials was studied experimentally under various drying conditions and the results were summarized as shown in Table 1.
The experimental equipment employed was the same as illustrated in the authors' previous papers.
The kinds of preformed materials used in the experiments were as follows:
Silica Gel 10mm diameter × 50mm length
Carbon Black 10mm diameter × 50mm length
Magnesium Carbonate 10mm diameter × 50mm length
Granulated Material A 1mm diameter × 2mm length
Granulated Material B 0.8mm diameter × 1.8mm length
The correlation of the drying data, as expressed with the water content and temperature of the material versus drying time, is illustrated in Fig. 1 and the effects of various factors on drying rate are summarized in Figs. 25.
Heat transfer capacity coefficients calculated from the experimental data are plotted against Reynolds number and are compared with the calculated values from the equation proposed by Hougen et al, as in Fig. 6. The experimental equation was obtained as follows:
ha=26G^0.75 (10mmφ×50mm) (8)
Observed pressure drops through the unit depth of beds versus the velocity of air plotted in Fig. 8 and are expressed by the following equations.
Δp/L=0.87υ_g²(10mmφ×50mm) (10)
Δp/L=3.8υ_g^1.6(1mmφ×2mm) (11)
Δp/L=6.0υ_g^1.6(0.8mmφ×1.8mm) (12)
υ_g=0.62.0m/sec

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The characteristics of a liquid cyclone with a diameter of less than 3 inches have not yet been reported in detail. We studied the design factors of a liquid cyclone whose diameter was less than 3 inches.
In this paper we report pressure drop, flow ratio, thickening and classifying characteristics of it.
Experimental apparatus was installed at the Itaya Ziekulite Chemical Mining Factory. As shown in Fig. 1, clay, wet-crushed in the tube mill, was sent to two 6'' liquid-cyclones and its overflow was fed in a 1'' or 2'' test cyclone. Inlet pressure of the liquid cyclone was adjusted within the range of 0.52.5kg/cm² gauge by closing and opening the by-pass. When the cyclone came to be operated at the constant rate, samples were taken from the overflow and underflow liquids. The solid content was estimated by the Specific Gravity Method and particle size distribution was determined by the Andressen Pipette Method.
1) Pressure drop of the liquid cyclone was about the same as with the result obtained by means of Dahlstrom's equation, but for the small change in the constant.
F=2.6×10^-7Q_f²/(D_i×D_o)^1.8
2) Flow ratio of the liquid cyclone was found to be the function of orifice ratio for underflow and overflow.
1-R_f=1-Rf=0.9/(D_u/D₀)⁴+1
3) Thickening characteristics of the liquid cyclone was found to be the function of flow ratio.
δ_u/δ_f=1.1(Q_u/Q_o)^-m
where m was 0.48 in the case of the 1'' cyclone and 0.19 in that of the 2'' cyclone.
4) Classifying characteristics of the liquid cyclone was as follows:
d₅₀=2.3×10⁴(D_i×D₀)^0.53/Q_f^0.65√μ/ps-pl

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