c.t.s.
Manzhurin I.P., Sidorina E.A., Medvedeva I.E.,Dostayeva A.M.
Karaganda State
Technical University, Kazakhstan
CALCULATION OF KEY PARAMETERS ROLLER OF THE CRUSHER
Roller mills are used for small and medium crushing of coal, ore, limestone
and other materials. Roller crusher (Figure 1) consists of two rolls 3 and 5 of
the same diameter, which rotate in opposite directions with equal speed.
Figure 1 - Scheme
of roller crusher
For brittle materials are also used grooved rollers and gears. The bearings
of one of the rollers may slip into the track and kept the springs 2. Between
the two bearing rollers are placed bearing
disk 4, which govern the width of the gap between the rollers.
The size of this gap determines the maximum amount of fragmented pieces of shattered
product coming out of the crusher. Smooth rollers crush lumps of material
crushing, dragging the piece between the friction rollers.
Toothed rollers crushed material splitting. Figure 2 shows that the imaginary plane of the OM and ON, the
tangents to the smooth surfaces of the rollers at the points contact tightened
with a piece of material form an angle β = 2α, where α is the
angle of capture roller crusher roller crusher.
To tighten the piece of material into the space between the rollers to be
complied with the condition β = 2 α. It follows that for roller
crusher
α ≤ φ,
where φ - the angle of friction of the material piece of rolls;
(φ = arctg f).
Thus, the coefficient of friction material on the rolls f = 0,3 and capture
angle should be α ≤ 16 ° 42 '. The multiplicity of crushing rollers
for smooth
i = Dc / d = 3 ÷ 5, for corrugated and toothed - 8; of these mills out pieces with dimensions of
20 mm.
Figure 2 -
Scheme of roller crusher
Maximum size of divisibility of the material depends on the diameter Dc
rolls, the state of their surface and the gap between the rollers. When smooth
rolls Dk = (0,04 ÷ 0,056); for corrugated Dk =
(0,08 ÷ 0,1).
Crusher performance is given by
Q = 3600 (2e + s) Lvμγ, t / h,
where 2e - the gap between the
rollers, m;
s - withdrawal of
rolling roll, m (s = 2-4 mm);
L - length of roll, m; v
- peripheral speed at the rim of the rotor, m / s;
v = (πDvn)
/ 60 m / s;
Dv - diameter of the rotor, m;
n - number of
revolutions per minute in the roll;
μ - coefficient of
loosening of the material, (μ = 0.2-0.5);
γ - specific weight
of material, t/m3.
Number of revolutions of the rolls
is determined by the formula
n = 308 √ f / (γrR), r / min,
where f - coefficient of friction
of the material on the surface of the rollers
(f = 0,3-0,4);
r - the radius (or shown
Radix) downloadable pieces of material, m;
R - radius of rolls, m
Necessary for the roll crusher capacity is determined by the formula
N = (LRn) / 142 800 {[σ2 (r2 - e2) / Er] + R2/740},
kW.
where L, R, r - cm;
e - half the gap between the rolls in cm;
σ and E - respectively the tensile strength and
modulus of elasticity of the ground material, kg/cm2.
Example of calculation. Determine
the performance of roller mills and the necessary power for its operation. The
diameter of the rollers Dv = 610 mm, length L = 400 rolls mm, the distance between the
rollers 2e = 10 mm, the strength of the divisibility of material (limestone)
σ = 1300 kg/cm2,
modulus of elasticity E = 600 000 kg/cm2;
specific gravity (density) γ = 2700 kg/m3.
The diameter of downloadable pieces
of material (smooth rollers)
Dc = 0.05 • DB = 0.05 • 610 = 30 mm.
Number of revolutions of the rolls
n = 308 √ f / (γrR) = 308 • √ 0,4 /
(2700 • 0,015 • 0,3 = 55 rev / min,
where f = 0,4; r = dc / 2 = 30 / 2
= 15 mm or 0.015 m;
R = DB / 2 = 305 mm, or
0.3 m.
The peripheral speed at the rim roll
v = πDvn / 60 = (3,14 • 0,61 • 55) / 60 =
1.8 m / sec.
Performance crusher
Q = 3600 (2e + s) Lvμγ = 3600 • (0,01 + 0,003)
• 0,4 • 1,8 • 0,3 • 2,7 = 27 t / h
where μ = 0,34; s = 3 mm or 0.003 m
Necessary to grind the material power
N =(LRn)/142800{[σ2(r2 - e2)/Er] + R2/740} = (40 · 30,5 · 55 )/142800· {[13002 ·
· (1,52 -0,52
)/600000·1,5] + 30,52/740}= 2,4 kW.
Literature
1. Efimenko GG Levchenko, VE Iron and other Metals .- Kiev: High School,
1988.-351 with.
2. Ramm AN The
modern blast furnace process .- Moscow: Metallurgiya, 1980.-303 with.