Application and Maintenance of Aggregate Heating System in Asphalt Mixing Station

The aggregate heating system of the asphalt concrete mixing station is composed of a burner and an aggregate heating drum. It is one of the key systems of the entire equipment. The reliability of the system plays an important role in the unit output of the equipment and the quality of the finished materials. The decisive role. Only scientific and reasonable use and maintenance of the system can ensure the efficient operation of the entire equipment, produce high-quality finished materials, and create good economic and social benefits.
1. The use and maintenance of diesel burners The QLB1000 asphalt concrete mixing plant used by our unit, whose burner is a Weishaupt (Weishop) fully automatic Monarch-R type 1-11 product imported from Germany, and its composition includes a burner Motor, oil supply pump, air supply device, air flow adjustment servo motor, high-pressure ignition device, flame injection device, flame diffuser, automatic program controller, etc. Since the whole machine is imported with original packaging, it must be used and maintained in strict accordance with the provisions of the instruction manual.

  • 1) The burner has relatively high requirements for fuel. The quality of the fuel must be ensured to avoid excessive impurities and wax in the fuel, and it can be used after 48 hours of precipitation; it is recommended to install two more on the fuel inlet pipe of the fuel pump. The density of the channel filter should be between 50-100μm. The filter screen should be made of corrosion-resistant copper material, the first is added on the side close to the oil storage tank, and the other is added on the side close to the oil supply pump to increase the filtering effect. This is because as long as the fuel supply pump is working, the diesel oil in the oil storage tank is always in circulation. Therefore, the impurities at the bottom of the tank are easily splashed and may enter the oil pump with the oil, causing serious wear of the oil pump. Therefore, the filter screen should be cleaned every 150-200h, and the filter should be replaced in time when the cleaning is invalid. The oil return pipeline should minimize the use of elbows, because the pressure value of the oil supply pump is higher (2~2.5MPa). If there are too many elbows, the oil return pressure will increase, increasing the pressure wear of the oil pump itself. Ensuring fuel quality, unobstructed fuel supply pipeline and good filtering effect are important guarantees for increasing the service life of the burner.
  • 2) When the burner is used again after being out of service for a long time, first open the installation hole of the fuel supply pump pressure gauge, check whether the fuel supply pump is full of diesel, and drain the gas in the pipeline and fuel pump before starting. Because the speed of the oil pump is very high (up to 3000r/min), if there is no diesel or air mixed in the oil pump, the oil pump will instantly form non-lubricated wear or air resistance at such a high speed, which will seriously affect the service life of the oil supply pump. .
  • 3) The function of the air flow adjustment servo motor is to automatically adjust the opening and closing angle of the damper when the burner is in ignition, low fire, high fire, and closed states according to the set damper opening and closing angle. This angle value is generally set by the manufacturer, but as the output increases during use, the heating effect of the burner on the aggregate will be weakened after a long period of use. This is due to slight wear and tear of the fuel supply pump, resulting in low fuel supply pressure. At this time, you can adjust the servo motor according to the relevant content of the instruction manual: move the lever of the servo motor to the side of the gear box, and increase the angle of the cam corresponding to the ignition, high fire, and low fire by 10-15°. Then move the lever to the vertical position, which can increase the air flow supply, play a role in supporting the combustion of the flame sprayed by the flame injection device, and enhance the combustion effect. There is a fan-shaped eccentric adjustable spring belt connected to the motor shaft on one side of the servo motor. Its function is to open the damper regulator at different angles according to the command of the servo motor to supply different amounts of air to meet the requirements of high-pressure diesel combustion. need. The shape and structure of the adjustable spring belt is adjusted by the manufacturer according to the air supply volume of the air supply device and the diesel fuel supply volume of the fuel supply pump. It should not be adjusted at will during use, so as not to cause an imbalance of the air and fuel ratio and affect the fuel. Burning effect.
  • 4) is to spray the high-pressure diesel oil delivered by the fuel supply pump in a mist form for full combustion. Its structure is a high-pressure one-way shut-off valve, and the outer layer is a filter screen. Clean the fuel injection nozzle every 400-500h to ensure sufficient and even fuel injection. When high-pressure diesel is injected, the automatic control device issues a command to ignite. The ignition device is composed of two high-voltage electrodes and an ignition transformer. The ignition transformer must be clean and dry during use. At the same time, the dust attached to the ignition electrode should be cleaned regularly to ensure that the burner can be ignited successfully. After cleaning the fuel injector, pay special attention to the distance between the two electrodes and the distance between the electrode and the fuel injector when installing two electrodes. The distance between the two electrodes is 3.5mm≤Ld≤4mm, the horizontal distance between the electrode and the fuel injector is 1.0mm≤LH≤3mm, and the longitudinal distance is 3mm≤LZ≤5mm. There is a flame sensor behind the injector, its function is to transmit the signal to the program controller after the ignition is successful, thereby interrupting the ignition operation program. If the sensor is too dirty, it cannot transmit the signal to the controller, and the ignition cannot be successful. During use, keep the flame sensor clean.
  • 5) The function of the flame diffuser is to make the sprayed flame form a swirling flame under the action of the diffuser. Swirl flame has two advantages: ①Form a low-pressure swirl zone at the head of the flame to make combustion more complete; ②The swirling effect of air makes the flame produce more intense heat radiation and transfer heat to the aggregate more efficiently , Reduce heat loss. After long-term use, due to the excessive dust particles in the air, a thick layer of coke mud will be formed under the action of high temperature, which will adhere to the diffuser and block the swirling pores, which will seriously affect the diffusion effect of the diffuser. Therefore, the coke sludge on the diffuser should be removed every 400-500h to ensure the good working effect of the diffuser. The cleaning method is to remove the locking nut of the burner, and then remove the fastening bolt on the other side that is symmetrical to the hinge axis, push the entire burner to one side, and loosen the fastening screw of the diffuser. Remove the diffuser, clean the coke mud, dredge the swirl hole and install it firmly. It should be noted that pay attention to the original position when disassembling the diffuser plate, otherwise it will cause the flame spreading distance to change and affect the flame burning effect.
  • 6) The function of the automatic program controller is to automatically adjust the working status of the burner according to the set working program. The controller is installed on the console in the operating room. Its structure is very precise and must be clean to prevent floating dust from falling into the circuit board and causing short-circuit failure.

As far as the entire burner is concerned, whether it is the control circuit, oil circuit or mechanical operation parts, it is most important to ensure cleanliness during use, and all parts must be cleaned or replaced regularly. Strictly speaking, the working environment of the burner should be fully enclosed and should not be exposed to the natural environment to avoid the dust particles in the air from being sucked in by the damper, forming a dirt layer on the surface of the flame sensor, ignition electrode, and flame diffusion plate , Thereby affecting the ignition and normal operation of the burner.

2. Use and maintenance of the aggregate heating roller

The function of the aggregate heating roller is to uniformly heat the various aggregates conveyed by the inclined belt. The heating roller is a cylindrical thick-walled roller, the outer layer is an insulation layer, and the inner surface is welded with a spirally arranged L-shaped scraper. The heating roller is installed on the bracket at a certain inclination angle, and is equipped with a rotary drive device, which is driven by a motor to make a rotary motion.

The normal working state is that the aggregate moves forward in the drum through the rotary motion of the drum, and is distributed in the entire space of the drum under the drive of the L-shaped scraper, and evenly receives the heat transferred from the burner. After a long period of use, due to the excessive powder in various aggregates, a thick hardened layer will be formed on the surface of the L-shaped scraper, which will affect the scraping effect of the scraper. , So that part of the aggregate is distributed in the upper, lower, left, and right spaces of the drum, and the other part of the aggregate can only move forward at the bottom of the drum. As a result, the heating effect of the aggregate will be significantly weakened, which not only reduces the unit output of the finished material, but also causes a waste of fuel. In response to this situation, after the annual production tasks are completed, the hardened layer on the scraper should be chiseled off in time.

In summary, in ordinary work, we must not only master the operation skills and maintenance procedures of the aggregate heating system, but also master its structure and working principle, and be good at observation and analysis, and look for faults that occur. Find out various reasons, conduct a comprehensive analysis, and use effective methods to troubleshoot and improve the working efficiency of the entire equipment.

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