(2) When the sedimentation interface is clear and the sedimentation curve is smooth and there is no critical compression point, the settlement test and data processing should use the tangent method, as shown in Figures 4(b) and (c).
Select settling tests on tH curve obtained at several points A i (t i, H i ), respectively, for the tangent of the curve, to cross the longitudinal axis of the points B i, calculated according to formula 10 of the supernatant in each B interface level i The average unit volume solid content of the pulp below the point:
Where i—the second of the selected points;
c p, i --- clarified to settle upon the interface B i, the solids content per unit volume of the slurry B i, t / m 3;
H o — the height of the pulp surface in the cylinder, m;
B i ———the intersection height of the tangent on the ordinate m..
Calculate the settling velocity of each point selected on the sedimentation curve of each test according to formula (11):
Where i—the second of the test;
υ ij ——— Settlement velocity of selected points on the settlement curve, m/h;
H i ———the height of each point selected on the curve, M;
t i ——— Settling time of each point above, h.
Find the required maximum unit concentration area as follows:
Where a max ———the maximum unit concentration area of ​​the desired concentrator, m 2 /(t · h -1 );
υ min ——— the minimum of the settling velocity of each point selected on the settlement curve of each test, m/h;
C pij ——— When the sedimentation interface of the test slurry settles to B ij , the average unit volume of the slurry below B ij is solid content t/m 3 ;
C p ———solid content per unit volume of the initial slurry, t/m 3 .[next]
(3) The sedimentation interface is unclear. When the sedimentation curve is not available (for example, the slurry is not easy to be settled, and the flocculant is not allowed to be added thereto), the sedimentation velocity measurement and calculation can be carried out according to the following steps.
A number of cylinders with a capacity of 2000 ml were selected to prepare samples of the same concentration required by the design, and were respectively loaded into the respective cylinders. According to different settlement time t i , the liquid of a certain fixed height h under each cylinder surface is taken out, the settlement speed Ï… i is calculated according to formula (14), and the suspended matter content c i is measured respectively, and Ï… i --c is drawn. The i- curve, according to which the sedimentation velocity is determined according to the overflow water quality c required by the design:
Where h———settling height, m;
t i ——— Settlement time required to reach the overflow quality required by the design, h. The required concentration area is:
Where Q—the designed overflow, m 3 /h;
K———Safety factor, according to the selected concentration and hunger size, K=1.1～1.2.
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