Reasonable selection, maintenance and energy saving of burners in asphalt mixing plants
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Reasonable selection, maintenance and energy saving of burners in asphalt mixing plants
Release Time:2024-04-29
Automatic control burners have been developed into a series of burners such as light oil burners, heavy oil burners, gas burners, and oil and gas burners. The reasonable selection and maintenance of burners can save a lot of money and extend the life of the combustion system. In recent years, facing the reduction in profits caused by rising oil prices, many asphalt mixing station merchants have begun to look for suitable alternative fuels to improve their competitiveness. Road construction machinery has always been biased towards the use of geothermal power generation fuel burners due to the special factors of its working conditions and use sites. In the past few years, light oil was mostly used as the main fuel, but due to the rapid increase in costs caused by the continuous rise in light oil prices, most of them have been biased towards the use of heavy oil burners in recent years. Now a cost budget comparison of light and heavy oil models is made for reference: For example, a 3000-type asphalt mixing equipment has a daily output of 1,800 tons and is used 120 days a year, with an annual output of 1,800×120=216,000 tons. Assuming the ambient temperature is 20°, the discharge temperature is 160°, the aggregate moisture content is 5%, and the fuel demand of a good model is about 7kg/t, the annual fuel consumption is 216000×7/1000=1512t.
Diesel price (calculated in June 2005): 4500 yuan/t, four months cost 4500×1512=6804,000 yuan.
Heavy oil price: 1800~2400 yuan/t, four months cost 1800×1512=2721,600 yuan or 2400×1512=3628,800 yuan. Using heavy oil burners in four months can save 4082,400 yuan or 3175,200 yuan.
As the demand for fuel changes, the quality requirements for burners are also getting higher and higher. Good ignition performance, high combustion efficiency, and wide adjustment ratio are often the goals pursued by various bridge crane construction units. However, there are many burner manufacturers with different brands. Only by choosing the right one can the above requirements be met.
Reasonable selection maintenance and energy saving of burners in asphalt mixing plants_1Reasonable selection maintenance and energy saving of burners in asphalt mixing plants_2
[1] Selection of different types of burners
1.1 Burners are divided into pressure atomization, medium atomization, and rotary cup atomization according to the atomization method.
(1) Pressure atomization is to transport fuel to the nozzle through a high-pressure pump for atomization and then mix it with oxygen for combustion. Its characteristics are uniform atomization, simple operation, fewer consumables, and low cost. At present, most road construction machinery uses this type of atomization model.
(2) Medium atomization is to press 5 to 8 kg of compressed air or pressurized steam to the periphery of the nozzle and premix it with the fuel for combustion. The characteristic is that the fuel requirements are not high (such as poor oil products such as residual oil), but there are more consumables and the cost is increased. At present, the road construction machinery industry rarely uses this type of machine. (3) Rotary cup atomization is to atomize the fuel through a high-speed rotating cup disk (about 6000 rpm). It can burn poor oil products, such as high-viscosity residual oil. However, the model is expensive, the rotating cup disk is easy to wear, and the debugging requirements are very high. At present, this type of machine is basically not used in the road construction machinery industry. 1.2 Burners can be divided into integrated gun-type burners and split gun-type burners according to the machine structure
(1) Integrated gun-type burners are a combination of fan motor, oil pump, chassis and other control components. They are characterized by small size and small adjustment ratio, generally 1:2.5. They mostly use high-voltage electronic ignition systems. They are low in cost, but have high requirements for fuel quality and environment. This type of burner can be selected for equipment with an output of less than 120t/h and diesel fuel, such as the German "Weishuo".
(2) Split gun-type burners are a combination of the main engine, fan, oil pump group and control components into four independent mechanisms. They are characterized by large size and high output power. They mostly use gas ignition systems. The adjustment ratio is relatively large, generally 1:4 to 1:6, and can even reach 1:10. They are low in noise and have low requirements for fuel quality and environment. This type of burner is often used in the road construction industry at home and abroad, such as the British "Parker", Japanese "Tanaka" and Italian "ABS". 1.3 Structural composition of the burner
Automatic control burners can be divided into air supply system, fuel supply system, control system and combustion system.
(1) Air supply system Sufficient oxygen must be provided for complete combustion of fuel. Different fuels have different air volume requirements. For example, 15.7m3/h of air must be supplied for complete combustion of each kilogram of No. 0 diesel under standard air pressure. 15m3/h of air must be supplied for complete combustion of heavy oil with a calorific value of 9550Kcal/Kg.
(2) Fuel supply system Reasonable combustion space and mixing space must be provided for complete combustion of fuel. Fuel delivery methods can be divided into high-pressure delivery and low-pressure delivery. Among them, pressure atomizing burners use high-pressure delivery methods with a pressure requirement of 15 to 28 bar. Rotary cup atomizing burners use low-pressure delivery methods with a pressure requirement of 5 to 8 bar. At present, the fuel supply system of the road construction machinery industry mostly uses high-pressure delivery methods. (3) Control system Due to the particularity of its operating conditions, the road construction machinery industry uses burners with mechanical control and proportional regulation methods. (4) Combustion system The shape of the flame and the completeness of the combustion basically depend on the combustion system. The diameter of the burner flame is generally required to be no larger than 1.6m, and it is better to adjust it relatively wide, generally set to about 1:4 to 1:6. If the flame diameter is too large, it will cause serious carbon deposits on the furnace drum. Too long a flame will cause the exhaust gas temperature to exceed the standard and damage the dust bag. It will also burn the material or make the material curtain full of oil stains. Take our 2000 type mixing station as an example: the diameter of the drying drum is 2.2m and the length is 7.7m, so the flame diameter cannot be greater than 1.5m, and the flame length can be adjusted arbitrarily within 2.5 to 4.5m.

[2] Burner Maintenance
(1) Pressure Regulating Valve Regularly check the fuel pressure regulating valve or pressure reducing valve to determine whether the surface of the locking nut on the adjustable bolt is clean and removable. If the surface of the screw or nut is too dirty or rusty, the regulating valve needs to be repaired or replaced. (2) Oil Pump Regularly check the oil pump to determine whether the sealing device is intact and the internal pressure is stable, and replace the damaged or leaking sealing device. When using hot oil, check whether all oil pipes are well insulated. (3) The filter installed between the oil tank and the oil pump must be cleaned regularly and checked for excessive wear to ensure that the fuel can reach the oil pump smoothly from the oil tank and reduce the possibility of potential component failure. The "Y" type filter on the burner should be cleaned frequently, especially when using heavy oil or residual oil, to prevent the nozzle and valve from clogging. During operation, check the pressure gauge on the burner to see if it is within the normal range. (4) For burners that require compressed air, check the pressure device to see if the required pressure is generated in the burner, clean all filters on the supply pipeline and check the pipeline for leaks. (5) Check whether the inlet protection device on the combustion and atomizing air blower is correctly installed, and whether the blower housing is damaged and leak-free. Observe the operation of the blades. If the noise is too loud or the vibration is too loud, adjust the blades to eliminate it. For the blower driven by the pulley, lubricate the bearings regularly and tighten the belts to ensure that the blower can generate the rated pressure. Clean and lubricate the air valve connection to see if the operation is smooth. If there is any obstacle in the operation, replace the accessories. Determine whether the wind pressure meets the working requirements. Too low wind pressure will cause backfire, resulting in overheating of the guide plate at the front end of the drum and the material stripping plate in the combustion zone. Too high wind pressure will cause excessive current, excessive bag temperature or even burnt.
(6) The fuel injector should be cleaned regularly and the spark gap of the ignition electrode should be checked (about 3mm).
(7) Clean the flame detector (electric eye) frequently to determine whether the position is installed correctly and the temperature is appropriate. Improper position and excessive temperature will cause unstable photoelectric signals or even fire failure.

[3] Reasonable use of combustion oil
Combustion oil is divided into light oil and heavy oil according to different viscosity grades. Light oil can obtain good atomization effect without heating. Heavy oil or residual oil must be heated before use to ensure that the viscosity of the oil is within the allowable range of the burner. The viscometer can be used to measure the results and find the heating temperature of the fuel. Residual oil samples should be sent to the laboratory in advance to test their calorific value.
After heavy oil or residual oil has been used for a period of time, the burner should be checked and adjusted. A combustion gas analyzer can be used to determine whether the fuel is fully burned. At the same time, the drying drum and bag filter should be checked to see if there is oil mist or oil smell to avoid fire and oil blockage. The accumulation of oil on the atomizer will increase as the oil quality deteriorates, so it should be cleaned regularly.
When using residual oil, the oil outlet of the oil storage tank should be located about 50 cm above the bottom to prevent water and debris deposited at the bottom of the oil tank from entering the fuel pipeline. Before the fuel enters the burner, it must be filtered with a 40-mesh filter. An oil pressure gauge is installed on both sides of the filter to ensure the good operation of the filter and to detect and clean it in time when it is blocked.
In addition, after the work is completed, the burner switch should be turned off first, and then the heavy oil heating should be turned off. When the machine is shut down for a long time or in cold weather, the oil circuit valve should be switched and the oil circuit should be cleaned with light oil, otherwise it will cause the oil circuit to be blocked or difficult to ignite.

[4] Conclusion
In the rapid development of highway construction, the effective use of the combustion system not only prolongs the service life of mechanical equipment, but also reduces the project cost and saves a lot of money and energy.