Vertical mill merges fine crushing, drying, grinding and powder selecting into a single, which simplifies the production process. It has the advantages of high grinding efficiency, low power consumption, large feed particle size, easy adjustment of grinding fineness, simple process, less land occupation, low noise, simple operation and maintenance, low cost and less wear-resistant material consumption. With the development of cement industry, vertical mill is not only used to grind raw meal and pulverized coal, but also to grind slag and clinker. It is more and more widely used in cement plants.
In the construction of cement production line, vertical mill is the main equipment. Its installation and commissioning plays a vital role in the construction and benefit of the whole cement plant.
The construction of Vertical Mill
Vertical mill consists of transmission device, grinding device, pressure device, separator, shell and holder, lubrication system, detection and control system, etc.
Transmission Device
The transmission device of vertical mill consists of three parts: main motor, coupling and reducer. It is installed in the lower part of the mill, not only drives the grinding disc, but also bears the weight of grinding disc, material, roller and the grinding pressure applied by the pressure device. It is one of the most important parts in vertical mill.
Grinding Device
The grinding device is composed of grinding disc and roller. Its shape design must make the ground material form a uniform material layer on the grinding disc. Therefore, a reasonable shape of the grinding disc matched with suitable grinding rollers plays an extremely important role in stabilizing the material layer, improving grinding efficiency and reducing grinding consumption.
Pressure Device
The vertical mill uses hydraulic pressure to exert force on materials. It can adjust pressure according to the grindability of materials so that the mill often operates under the most economical conditions. Because of the cushioning effect of accumulator, the pressure exerted by hydraulic cylinder has great elasticity and can be adjusted automatically.
Separator
The rotation rate of the separator is adjustable. The high-speed rotation of the rotor separates the coarse and fine particles. Then the fine particles will pass through the clearance between the separator blades to get out of the mill and be collected by the dust collector.
Shell and Holder
The shell of vertical mill restricts the space of grinding operation, and the frame bears the weight of the shell and the dynamic load generated in the running of equipment.
Lubrication System
Lubrication system includes oil station, pipeline and various valves. The oil station can be further divided into electric motor oil station, high and low pressure oil station of reducer, powder concentrator oil station and the roller lubrication oil station.
Detection and Control System
The detection and control system includes temperature detector, pressure detector and some other primary detectors. And then there are sensors and control cabinets.
The Installation of Vertical Mill
The Placement of Pad Iron
The function of pad iron is to make all the weight and the working load of the equipment pass to the base evenly and adjust the height of the equipment by adjusting the thickness of the pad. It is usually made of ordinary steel plate or cast steel and can be made into plane and inclined plane. When we install the vertical mill, it should be mounted close to the anchor bolt, as far as possible arranged in the center gravity position of the load. Moreover, we need to pay attention to the symmetrical arrangement to prevent the machine base from being loose or broken due to uneven force. During the placement, the number of pads should not exceed 4 pieces and the height of each set should not be less than 30 mm. Under normal conditions, we hold the opinion that the optimum height is 40-80 mm and the optimum horizontal degree of the upper surface is 0.2 mm/m.
The Installation of Transmission Device
During the installation of the transmission device, we need firstly install the base of reducer, in which removing the anti-rust paint on the base surface is usually the first step. Then, drill the anchor bolt hole, and make the bolt in a natural state, respectively placed in the center of the hole. Each anchor bolt should be placed with a set of pad iron and each set should not exceed four pieces. Among them, there should have one pair of oblique pads. The length of the oblique pads that exposed outside the base is 30 mm. After that, we will continue with the installation of reducer and main motor. When installing the main motor, we should first connect the main motor and the bottom plate with bolts, and add a 2.0mm pad between them. The same as the reducer base, each bottom plate anchor bolt also need to be placed with a set of pad iron. The anchor bolts should drop naturally in the hole to align the center of the main motor and reducer. After positioning, we grouted in the void and tightened the anchor bolts when the concrete strength reached 75% of the specified strength. And when we finish all of these, between pad iron and pad iron, pad iron and bottom plate shall be spot welded and fixed.
The Installation of Pressure Device
First of all, we need to put the assembled pressure device in place according to the requirements of the drawings and connect it with the main body of the mill. Then check the working cylinder and inspect the distance between the two centers of the cylinder. After that, the anchor bolts will be grouted and fixed and the bolts will be tightened after the mortar solidifies.
The Installation of Grinding Disc
In the first step, we need to gently lift the grinding disc and mount it on the reducer, then align them and install the locating pin. After that, we should tighten the connecting bolt with uniform force and adjust the position of the lower casing to make the radial clearance between the grinding disc and the air ring basically consistent.
