At present, most of the screening and crushing equipment used at the front end of pulverized coal furnaces in coal-fired boiler power plants at home and abroad are mainly rolling screens and mineral sizers. The coal below 300mm goes into the rolling screen for screening, and the material below 30mm passes directly through the material under the screen and out of the skip without entering the mineral sizers. The screenings enter the mineral sizers to 30mm, and then enter the coal mill to grind into pulverized coal, and then enter the pulverized coal furnace to burn. Roller screen is independent power, each shaft is driven by a reducer rotor to the direction of coal flow in the same direction, the rotor and the horizontal plane is installed at a certain Angle, for two adjacent rotors, in the combined part, the same rotation into opposite rotation, at this time, if the material contains the size of the screen close to the coal gangue and other hard objects, stuck phenomenon is inevitable: If the moisture content of the material is too large, the phenomenon of rolling screen sticking is inevitable.
Mineral sizers use the opposite differential rotation of the two-toothed roller to achieve material fragmentation. When the material enters the crusher, the smaller material less than the gap between the toothed rollers passes directly from the middle gap between the two toothed rollers, avoiding the crushing of the smaller material again, and the larger material larger than the gap between the two toothed rollers rolls on the tooth roller, so as to choose the fragile direction of the material for crushing, which can save energy as much as possible. The material is split, squeezed and pulled between the toothed rollers into the required particle size. This mode of work integrates screening and crushing functions in one, while fully saving energy, and minimizes the loss of materials such as over-crushing. The crusher has the following characteristics:
(1) The discharge particle size can be adjusted: when the tooth plate is worn to a certain extent, the gap between the two teeth rollers is adjusted to ensure that the discharge particle size is up to standard.
(2) Non-sticky and non-blocked, no requirement for water content of broken materials: The principle of differential rotation, the two teeth roller opposite the differential rotation, due to the different speed, so the two teeth of the roller line speed is different, that is, in the two teeth of the roller mesh crushing teeth produce relative movement, equivalent to the edge of the crushing edge automatic cleaning each other, completely solve the crushing industry in the past hundred years due to the material moisture is too large and viscous caused by the problem of crusher water content of the material without requirements.
(3) A machine with screening and crushing function, the amount of powder is very low: the two teeth roller tooth plate with a certain gap between each other, the gap between them is similar to the sieve, therefore, saving the traditional arrangement of the crusher front end of the roller screen; When broken, the material less than the size of the screen passes directly and is no longer broken, so as to achieve the screening effect without increasing the amount of powder.
(4) High-efficiency and energy-saving: The roller is hollow, and most of the mass is distributed on its outer circumference, so the inertia of the tooth roller is very large, and it can reserve a lot of energy. During the crushing process, it mainly uses its own energy for inertial crushing, which has little impact on the motor current. The motor only needs to smoothly replenish energy to the tooth roller, and the motor configuration is only about 40% to 60% of the ring hammer of the same specification. Practice has proved that the unit crushing energy consumption of L crusher is only 0.300.51kW.h/t, less than 2/3 of the ring hammer.
(5) Environmental protection, no dust: mineral sizers the two toothed rollers rotate inward at the same time, the air flow generated by the toothed rollers basically cancels each other, the wind pressure difference between the inlet and outlet of the equipment is very small, basically no dust, there is no need to install special dust removal equipment.
(6) Small vibration, low noise: mineral sizers tooth roller speed is very low, is the ring hammer rotor speed of a few tens of times, so the equipment runs smoothly, the amplitude is only about 1/3 of the same specification ring hammer amplitude, the noise is lower than the equipment motor 85 dB.
(7) High degree of intelligence: set the automatic refueling cycle of each lubrication point in advance, and lubricate each lubrication point at a fixed time: the control system issues control instructions according to the automatically detected temperature signal, automatically remove dirty oil, add new oil to cool down the lubrication point: When the vibration of the equipment in bad working conditions intensifies beyond the set value or the overload speed of the equipment decreases below the set value, the control system sends out control instructions according to the detected amplitude value or speed value signal, and automatically stops to protect the safety of the equipment; The control signal of the device itself can be transmitted to the user's central controller to achieve remote linkage control.
In the coal transport system of 2×300MW unit of a pulverized coal furnace power plant in Xinjiang, before 2010, the screening and crushing equipment used two 600t/h roller screens + ring hammer. As lignite is the main coal in this region, the water content in the coal medium is large, and the coal gangue content in the medium is as high as 40%, therefore, the roller screen often fails to stop the screen shaft, break the safety pin, and stick and block, and the ring hammer is also often blocked, and the grate holes are often blocked, resulting in a substantial decrease in the ring hammer output, high vibration, high noise, large dust and high energy consumption. The normal operation of the device is directly affected. In order to solve the above problems, the power plant accepted the transformation of L crusher instead of roller screen + ring hammer broken by our company, after more than 3 years of use, the equipment runs well, withstands the harsh working condition verification of large material water content and large coal rod stone content, and the vibration and noise are significantly reduced compared with the previous ring hammer broken, basically no dust, no sticking and no blocking. Yield, product size and grain size gradation are guaranteed. Through comparison, it is found that mineral sizers has obvious energy saving and efficiency improvement effects, as follows:
(1) Cancel the roller screen in the original process, reducing the procurement cost of about 400,000 yuan.
(2) In the original process, the roller screen runs 18 hours a day, the single power of 48kW, the annual work 300 days (the same below), the power consumption of 259,200 degrees, the electricity price of 0.50 yuan per degree (the same below), the annual operation of a single electricity bill of about 129,600 yuan: a single screen treaty replaced once a year 30000 yuan. Annual operating cost savings of 319,200 yuan.
(3) The original process of the ring hammer is running 18 hours a day, the motor power is 560kW, the power consumption is 3,024,000 degrees, and the annual operation electricity cost of a single set is about 15.12 million yuan; mineral sizers only run for 12 hours a day, the motor power is 250kW, the power consumption is 900,000 KWH, and the annual operating electricity cost of a single unit is about 4.5 million yuan. The power saving benefits of shortening coal loading time and reducing power during coal loading are about 21.24 million yuan each year.
(4) The normal service life of the first class wearing parts broken by the hammer in the original process is 3 months, and it is replaced at least 3 times a year, costing about 200,000 yuan/set each time, and the total annual maintenance cost is 1.2 million yuan: mineral sizers tooth plate life is 2500 hours, the replacement cycle of tooth plate is 1.44 times per year, each cost about 250,000 yuan/unit, the annual maintenance cost is 720,000 yuan. The annual equipment maintenance cost is reduced by 480,000 yuan. In summary, mineral sizers can save about $22,429,200 annually, and considering that the accuracy rate of analysis and calculation is 50%, the annual actual benefit is $11,214,600.