Auxiliary equipment
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In order to achieve dry and dewatering of materials, in addition to drying, a series of auxiliary equipment, including burners, blowers, dust collectors, induced draft fans, feeders and discharge machines, are required. The dust collector is not introduced here, and the other auxiliary equipments are mainly introduced here.
First, the burning furnace
A furnace is a device that burns combustion to produce high-temperature flue gas. Depending on the combustion, into the coal-fired furnace burner, oil furnace, gas furnace alkenyl. In the coal-fired furnace, according to different combustion methods, it can be divided into a fire bed furnace, a pulverized coal furnace, a cyclone furnace, a boiling furnace and the like. In the thermal drying of the coal preparation plant, most of the fire bed furnaces are used except for the boiling bed layer dryer. Fire-bed furnace having a metal grid - Stoker grate, the fuel was placed on the grid to form a homogeneous, a certain thickness of the fuel bed, and therefore also known. According to the movement pattern of the fuel layer relative to the grate, the fire bed furnace is divided into three types: a fixed grate furnace in which the fuel layer does not move; a tilting feeding furnace and a vibrating grate furnace in which the fuel layer moves along the grate; A chain grate furnace that moves together.
1. The basic structure of a fire bed furnace
The basic structure of the fire bed furnace is shown in Figure 1. The inner wall of the furnace wall is refractory brick, the outer layer is made of red brick, and the middle is filled with heat insulation material. In order to improve the strength of the furnace wall, there is a frame surrounded by metal steel outside the outer wall, and the furnace door and the inspection hole are arranged on the front furnace wall. The top of the furnace is arched, which not only improves the strength of the furnace, but also reflects heat reasonably and improves the combustion state. Since a blast is entered into the combustion chamber from the grate, the ash bin needs to be sealed. The dust chamber uses the principle of inertial separation and gravity sedimentation to accumulate the coarse soot contained in the high-temperature flue gas to avoid entering the dryer to increase the clean coal ash.
2. Grate
Work is an important part of fire grate hearth with cast iron casting. The function of the grate is to support the combustion layer and perform a blast through the grate to fully burn the fuel layer on the grate, and the slag generated after combustion is also removed through the grate. In order to support the combustion layer, and the grate is operated at high temperatures, the grate must have a certain strength. In order to perform a blast, the grate should have a certain porosity, and the grate can be cooled by the air supply to improve the working condition of the grate.
According to the movement mode of the grate, it can be divided into the following two structures.
1 flip grate - flip grate structure as shown in Figure 2, generally consists of two sets of grate, each set of grate has a separate link transmission mechanism, can drive the grate, so that the grate piece is turned from horizontal position to erect The slag is discharged between the slabs of the true slab. The burning and ash discharge of the inverted grate is intermittent, and the two sets of grate are alternately operated.
Figure 1 burning furnace
1, grate; 2, furnace top; 3, dust reduction; 4, feeding box; 5, gray warehouse; 6, burning furnace;
7, grate; 8, grate; 9 coal bucket [next]
Figure 2 flip grate
1. Coal blasting machine; 2. Coal conveying tuyere; 3. Turning grate; 4. Furnace door; 5. Air inlet;
6, look at the fire door; 7, fly ash recovery complex combustion device
2 chain grate - the chain grate piece is shaped like a chain link. The whole grate is made up of many chain links in series to form a wide endless chain and wound around the front and rear axle sprocket, as shown in Figure 3. . The entire grate moves under the drive. Like a conveyor, the fuel moves with the grate on the grate, moves to the end of the grate after complete combustion, and is removed from the end.
In addition to the above two structures, there are vibrating grate and inclined grate.
Figure 3 chain grate
1, sprocket; 2, coal hopper; 3, gate; 4, front arch turret; 5, chain grate; 6, windshield;
7, eagle iron; 8, active link; 9, grate piece; 10, round steel rod
3. Coal shovel
The coal shovel is a device that uniformly throws fuel into the combustion chamber to form a combustion layer. According to different working principles, it can be divided into three types: mechanical slinger, wind slinger and wind machine slinger. The working principle is shown in Fig. 4. Shown.
Figure 4 Schematic diagram of the working principle of the coal thrower
(a), (b) mechanical coal shovel, (c) wind slinger; (d) wind machinery slinger
1. Coal feeding device; 2. Coal striking mechanism; 3. Inclined plate; 4. Wind-seeding coal device [next]
Mechanical coal shovel: Disperse the fuel with rotating blades [Fig. 4(a)] or oscillating screed [Fig. 4(b)]. The coarse granules are thrown away in the longitudinal direction of the grate, and the fine granules are in the vicinity; Coal shovel: Disperse fuel with gas [Fig. 4(c)], the particle size distribution is opposite to that of mechanical pulverizer, coarse granules fall at the front end of the grate, fine granules fall at the rear end of the grate; wind mechanical slinger : Taking into account the characteristics of both wind and mechanical coal shovel [Fig. 4(d)], the particle size distribution of the fuel on the fire bed is relatively uniform.
Second, the feeder and the discharge machine
The feeder and the discharge machine are the control devices for the wet clean coal and the dried product entering and leaving the dryer. There are two functions of the feeder: firstly, the wet clean coal is uniformly fed into the dryer and the feed amount of the clean coal is controlled; secondly, it acts as a sealing to prevent the cold air from entering the dryer from the feed end, Closed to the main. There are also two functions of the discharge machine: first, the product after drying is fed to the next process; and second, it acts as a sealing to prevent cold air from entering the dryer from the discharge end, and is also mainly closed. Because the dryer is operated under negative pressure, the pressure of the hot flue gas in the dryer is slightly less than the atmospheric pressure. Since the feeder and the discharger are closed at both ends of the dryer, external cold air can be prevented from entering the dryer to lower the drying temperature. , thereby reducing heat loss and ensuring product moisture.
Feeder
The feeders used in the thermal drying of coal preparation plants include star feeders and SG type feeders.
1 star feeder - star feeder is also called roller feeder, or drum feeder, the structure shown in Figure 5. The casing is cast from cast iron and connected to the wet coal bunker, such as in the front of the drum dryer; the lower feed sealing chute, if used in front of the tubular dryer, the lower part is connected to the loose coal, to the drying pipe Throw coal. The rotor rotates under the drive, and when the wet clean coal enters the star feeder, it is stored in the arc space of the rotor, and is discharged from the lower end of the casing by its own weight as the rotor rotates. The transmission drives the cleaner to rotate, but the rotation speed is different from that of the rotor. Each time the rotor rotates through a curved blade, the cleaner rotates for one week and the wet coal that sticks to the rotor is scraped off.
The loose coal machine [Fig. 5(b)] consists of three parts: the casing, the rotor and the transmission. The casing is made of cast iron, the rotor consists of 20 segments, and each blade has 8 blades that can be rotated by the transmission. The wet clean coal enters the loose coal machine through the star feeder, and is stored in the space between the blades, and rotates with the rotor for nearly half a week. Under the action of centrifugal force, the discharge port breaks into the dryer, and the large flotation The coal ball is broken, which is good for the drying of wet coal.
Star feeders are commonly used for the feeding of drum dryer dryers. The advantage is good sealing performance. The disadvantage is that the feeding space is small, the material is easy to be bonded, and the feeding volume is reduced; if the amount of flotation fine coal in the wet coal bin is large or unevenly distributed, the discharging is difficult; when the coal bin is loaded too much, the rotor pressure is relatively Big.
The structure of the 2SG type feeder - SG type feeder is shown in Figure 5. The important working parts of the SG type feeder are the feeding rolls 2, which are the driving roller and the driven roller respectively, and are driven to rotate by the transmission device, and the two rollers are driven by the linkage gear. The wet clean coal is fed to the feed roller, which is discharged from the lower portion due to the rotation of the roller. In order to prevent the wet clean coal from "shelving" above the feed rolls, a breaking arch device 1 is placed above it. In order to prevent the flotation of the clean coal, increase the vaporization area of ​​the wet clean coal in the dryer, and set a loose wheel 4 under the feed roller, and the wet clean coal is put into a dryer of 10 mm size. A cleaning device 3 is also placed under each feed roller to scrape off the wet fine coal on the adhesive roller. When working on the SG type feeder, a small amount of coal should be kept in the feeder to seal the gap between the feed roller and the outer casing. The throughput of the SG type feeder is adjusted by the governor controlling the rotation speed of the feed roller.
Figure 5 star feeder and loose coal machine
(a) star feeder, (b) loose coal
1, the casing; 2, the impeller rotor; 3, the cleaner; 4, the blade rotor shaft; 5, the blade [next]
2. Discharge machine
The discharge machine used in the thermal drying of the coal preparation plant has a vane type discharge machine and a gas locker.
The structure of the 1-wheel type leaf discharge machine - the vane type discharge machine is shown in Fig. 7. The casing is cast from cast iron, the upper end is connected to the dryer discharge box, and the lower end is fed to the next process through the chute. The casing is provided with a leaf plate or a rotor, and a rubber strip 4 is arranged on the blade, and the rubber strip is in contact with the casing to seal. After drying, the product is fed into the vane type discharge machine from the upper end, and the product is brought to the lower part to fall by its own weight as the rotor rotates. Since the product moisture after drying is 8%-10%, it does not stick to the blade, so there is no need to clean the device.
Figure 6 SG type feeder
1. Broken arch device; 2. Feeding roller; 3. Cleaning device; 4. Loose wheel; 5. Drive device
Figure 7 vane discharge machine
1, the casing; 2, the rotor shaft; 3, the blade; 4, rubber strip
2 air locker - air lock is widely used, suitable for all types of dryers, generally installed on the discharge pipe of the dust collector. There are various forms, among which the non-powered air locker has the advantages of simple structure, low reliability of operation and low maintenance, and convenient maintenance, and is more widely used than a powerful air locker.
In the unpowered air lock, according to the different structural characteristics, it is divided into two types: rotary valve type and valve type. The valve type locker is divided into two types: a flat flap type and a conical flap type. FIG. 8 is a conical shutter type air locker.
The conical valve locker is directly mounted on the discharge pipe and consists of a support frame, a lever, a hammer, a conical shutter and an outer casing. Due to the action of the weight 2, the conical shutter 3 is in the closed position, at which time it does not discharge and acts as a seal. When the clean coal enters the discharge pipe 4, it falls on the conical shutter, and since the weight of the weight is larger than the weight of the material, the shutter is still closed. As the amount of clean coal in the discharge pipe increases, and the weight is greater than the weight of the weight, the conical shutter opens to drain the clean coal. After the clean coal is discharged, the conical shutter is closed again by the action of the weight.
Figure 8 Conical valve locker [next]
1. Support frame; 2. Heavy hammer valve; 4. Discharge pipe; 5. Lever; 6. Shell
In order to better seal, in a pipeline, it is better to install two air lockers, and the two air lock flaps are respectively opened and closed to close.
Third, blower and induced draft fan
It can be known from the fuel combustion process and the thermal drying principle that in order to fully burn the fuel entering the combustion chamber, it is necessary to supply the air reasonably; in order for the high-temperature flue gas generated by the fuel to dry the clean coal, the exhaust must be organized.
To achieve the flow of various airflows, it is necessary to rely on external forces to overcome the flow resistance. The external force is called ventilation.
Both the high chimney and the installation of the fan provide ventilation for the air and fumes. Therefore, there are two different ways of ventilation. The ventilation generated by the chimney is called natural ventilation. In addition to the chimney, the ventilation generated by the wind is artificial ventilation, also known as mechanical ventilation or forced ventilation. Artificial ventilation is divided into three categories: pressure feed blast type, suction suction type and smooth ventilation type. The combined use of pressure blast and suction air is balanced ventilation, and the thermal drying of the coal preparation plant adopts balanced ventilation. Balanced ventilation is the most ideal ventilation method. Even if the ventilation resistance in the system is large, the pressures in the combustion chamber, dryer, dust collector and flue can be adjusted freely and conveniently to fully utilize the thermal efficiency of the furnace.
The pressure ventilation is to use a blower to forcibly send air having a pressure higher than atmospheric pressure from the underside of the grate or from the tuyere on the wall of the combustion chamber to the combustion chamber, and the blower is disposed at the air inlet of the combustion chamber. In order to facilitate the operation, the pressure in the furnace should be similar to or slightly lower than the atmospheric pressure, that is, the furnace is kept under a slight negative pressure, and the flame is not sprayed when the furnace door is opened. Therefore, the blower and the induced draft fan are required to match.
The function of the blower is to supply the oxygen necessary for the combustion of the fuel to promote the full combustion of the fuel. According to the position and function of the air supply, the combustion furnace can be divided into two types: one blast and two blasts. A blast blows air from the grate into the combustion chamber, provides the oxygen necessary for fuel combustion, and is heated and cooled by the grate as it passes through the grate to improve the working environment of the grate. The secondary blasting, feeding air from the fire bed, providing a part of oxygen, can also disturb the airflow in the furnace and make it self-mixing, thereby ensuring the excess air coefficient in the furnace and reducing the chemical incomplete combustion loss. The feeding mode, position and air volume of the secondary blast are related to the furnace type and fuel, and generally account for 5%-10% of the total air volume.
The air volume of the blower is related to the type of fuel, the fuel consumption per unit time, and the air consumption factor. The wind pressure of the blower can overcome the resistance of the air duct, gate, grate and fuel layer.
The induced draft fan is installed between the dust collector and the chimney and has a certain suction force to overcome the resistance of the flue gas through the combustion furnace, the dryer, the dust collector, the flue and various control gates, so as to be discharged from the chimney at a certain speed. Therefore, the wind pressure of the induced draft fan is greater than the resistance of the flue gas through the combustion chamber, the dust chamber, the feed box, the dryer, the discharge bin, the dust collector, the flue and various control gates. The air volume of the induced draft fan is related to the amount of flue gas generated by fuel combustion per unit time and the amount of moisture vaporized by wet clean coal.
The blower fan used in the force drying of the coal preparation plant mostly uses a centrifugal fan, and its structure is shown in Fig. 9. It is mainly composed of an impeller and a casing. The impeller is composed of a vane 3 and a front disc 2 and a rear disc 4 which connect the vanes, and is mounted on a rotating shaft (not shown) through a rear disc, and the motor belt rotates at a branch. The casing is generally made of an Archimedes spiral box made of steel plate, and a shutoff plate 7 is installed at the air outlet 6 to control the air volume.
Figure 9 Schematic diagram of the main structure of the centrifugal fan
1, the air inlet; 2, the front disk; 3, the blade; 4, the rear disk; 5, the casing;
6, the air outlet; 7, the interceptor; 8, the bracket
When the impeller rotates, the gas rotates with the blades to obtain centrifugal force, and the air is squeezed into the casing from the opening between the blades, so that the gas pressure in the casing is increased and discharged by the guiding air outlet. After the gas is scooped out, the pressure at the central portion of the impeller is reduced, less than atmospheric pressure, so that the external gas energy continuously enters the machine.