How to improve the specification of tube mill to increase output?
Date：2019-09-03 16:21 Source：cementepcViews:
This paper mainly introduces the technical improvement and application of the anti - blocking grate in tube mill.
1. Existing problems of casting grate plate
1.1 grate joints are easily blocked by abrasive bodies
The current technology of grate plate for ball mill usually adopts traditional casting grate plate, which has many problems.Because the casting error and draft Angle, grate seam is commonly 7 to 10 mm, and often USES fine grinding storehouse Φ 8 ~ 10 mm Φ steel section, once the wear and tear, hard to avoid congestion grate seam, light person reduce material flow velocity in the grinding, affect the grinding production, increase the endogenous wind resistance, increase the grinding energy consumption;If there is too much incoming material or partial blockage of compartments and grate plates, "full grinding" will occur. Even if the abrasive body is located in the outer layer, it cannot produce projectile movement, which will increase the energy consumption of the mill.
1.2 low hardness and short service life
People have not been able to get rid of the tube mill high power consumption, high metal (steel ball, lining plate, compartment plate, etc.) consumption problems.Cast liner is thicker, traditional design thickness is 50mm.Although cast alloy is used and heat treatment is used to harden it, the hardness can only reach HRC40.
1.3 low through-hole ratio
Limited by casting and strength conditions, the traditional design grate perforation rate of 9%, once there is a local blockage, material flow directly blocked, the speed is lower, fine powder can not go out, forming a mat, reduce grinding output, increase grinding energy consumption.
2 Technical improvement of anti - blocking grate plate
2.1 improvement purpose and design idea
The purpose of the design is to fundamentally solve the problems existing in the grate plate of the current mill, improve the strength, wear resistance, through-hole rate and operation rate, and reduce the power consumption of grinding, manufacturing cost and operation cost.
2.2 improvement contents
2.2.1 aiming at lightweight and high-strength mechanical properties, study and optimize the wear-resistance, cutting and welding properties of various sieve plate materials, and optimize the grate plate which is nearly 50% smaller than the original thickness.A cutting, welding and heat treatment hardening alloy steel grate plate is developed to replace the current ball mill casting grate plate, and the accuracy of grate seam is accurately controlled ±0.2mm to basically avoid steel section blockage.
Grate is wear parts, improve wear parts wear resistance is the main goal of research and development, the usual method is:
(1) add wear alloy elements;(2) surface treatment to improve wear resistance;Heat treatment hardening.This design optimization good hardenability chromium manganese alloy, have good weld performance of carbon equivalent, on the basis of carbon in low alloy steel to study a kind of new wear-resistant steel: design n in different chemical composition of test steel, n kinds of test steel under the condition of invariable in carbon equivalent, by changing the content of Mn, Cr, Mo element, analysis and comparison test metallographic structure and mechanical properties of steel after rolling;Then choose a material with the best hardness and impact toughness from n kinds of test steels for subsequent heat treatment test.The most reasonable heat treatment process specifications are determined by comparing the performance indexes of different heat treatment processes, and industrial trial production is carried out.
2.2.2 the use of advanced molding process and a new heat treatment process to make grate plate hardness around HRC50, intensity of sigma b > 1600 mpa, Φ Φ 4 ~ 5 m and 2.8 ~ 3.8 m Φ Φ mill original 50 mm thickness of the casting can be 30 mm and 20 mm, instead of grate plate save nearly half of steel.For the reform of the grate plate of the original mill, the combined grate plate technology method of welding the alloy liner plate to the frame after hardening during heat treatment in this project can be adopted. The modification can be carried out simply without moving the position of the liner plate.
2.2.3 the mathematical model between grate opening rate, grate thickness, grate gap size and form, material flow resistance, fine powder passing capacity and grinding energy consumption is established to provide theoretical basis for the form and size of grate opening.The main factors affecting the output of ball mill are the arrangement and width of grate seam.
To further reduce material flow resistance, in addition to appropriately increase the rate of hole, the project team to grate seam form and the working mechanism of grate plate were analyzed and research: grate form V respectively, inverted V and V 9 types, such as grate plate thickness from 15 mm to 60 mm, build test device, adjust the fan speed, test through grate seam section size of wind speed, material flow through the speed of grate seam forms and grate plate thickness effects on the material flow velocity, the wind speed.CFD and EDEM coupling method is adopted to build a mathematical model on the basis of the above test data, and optimize the grate slit size, form, opening ratio and grate thickness, so as to provide theoretical feasible basis for the grate lightweight and pre-grinding to reduce energy consumption.
2.2.4 the traditional silo structure is silo bracket + sieve plate + casting grate plate, with a clearance of about 50mm between grate plate and sieve plate.The improved silo structure is silo bracket + blocking grate plate, which is directly installed on the silo bracket.The effective grinding space is increased after improvement.
(1) the grate plate of the new mill saves more than 60% of the material than the casting grate plate, the transformation and replacement of the grate plate saves about 50% of the material, and the combined grate plate saves more than 25% of the material than the casting grate plate.
(2) the service life of grate plate is on average more than 50% longer than before.
(3) the grate plate of ball mill casting can be modified by this technology, and the comprehensive average energy saving in grinding process is more than 1.5kWh/t.
(4) improved grate wear resistance, improved mill operation rate, reduced grinding energy consumption and reduced operating cost.
(5) the width of the silo separation device and grate device decreases with the adoption of the grate plate, the grinding space increases, and the grinding efficiency improves.
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