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 disk4, 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 D c rolls, the state of their surface and the gap between the rollers. When smooth rolls D k = (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.
