The development of automatic control burners has been serialized such as light oil machines, heavy oil machines, gas machines, and oil-gas dual-purpose machines. Reasonable selection and maintenance of the burner can save a lot of money and prolong the life of the combustion system. In recent years, in the face of the decrease in profit caused by rising oil prices, many asphalt mixing plant operators have begun to look for suitable alternative fuels to improve their competitiveness. Due to the special factors of its working conditions and the site of use, road construction machinery has always been biased towards the use of fuel oil burners. In the past few years, light oil was mostly used as the main fuel, but due to the continuous rise in the price of light oil, the cost has increased rapidly, and in recent years most of them have focused on the use of heavy oil burners. A cost budget comparison of light and heavy fuel oil models is now made for reference:
For example, the daily output of a 3000-type asphalt mixing plant is 1800t, and it is used for 120 days per year, and the annual output is 1800×120=216000t. Assuming that the ambient temperature is 20°, the discharge temperature is 160°, the moisture content of the aggregate 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=6.804 million yuan.
Heavy oil price: 1800-2400 yuan/t, four months cost 1800×1512=2.7216 million yuan or 2400×1512=3.6288 million yuan. After four months, the use of heavy oil burners can save 4.0824 million yuan or 3.1752 million yuan.
While the demand for fuel is changing, 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 construction units. However, there are many burner manufacturers and different brands. Only when the burner is selected properly can the above requirements be met.
1 Selection of different types of burners
1.1 The burner is divided into pressure atomization, medium atomization and rotor atomization according to the atomization method
(1) Pressure-type atomization is to deliver fuel to the oil nozzle through a high-pressure pump for atomization and then mixed with oxygen for combustion. It is characterized by uniform atomization, simple work, less consumables, and low cost. At present, most road construction machinery All choose this kind of atomization model.
(2) Medium atomization is through 5~8kg of compressed air or pressurized vapor pressure to the periphery of the oil nozzle and fuel for premixing and then combustion. It is characterized by low requirements for fuel (such as residual oil and other poor oil products), but There are many consumables and the cost is high. At present, this type of machine is rarely used in the road construction machinery industry.
(3) Rotor cup atomization is to use a high-speed rotor disc (about 6000 rpm) to remove the fuel from the atomization. It can burn poor oil products, such as high-viscosity residual oil, etc. However, the model is expensive, and the rotor disc is easy to wear, which requires high debugging. At present, the road construction machinery industry basically does not use this type of machine.
1.2 According to the machine structure, the burner can be divided into one-piece gun type machine and split gun type machine
(1) The integrated gun machine is a combination of fan motor, oil pump, chassis and other control components. It is characterized by small size and small adjustment ratio, generally 1:2.5. High-voltage electronic ignition system is mostly used, and the cost is low, but Higher requirements on fuel quality and environment. This type of equipment can be used for equipment with a material output of less than 120t/h and diesel fuel, such as the German "Weissout".
(2) The split gun machine is to divide the main engine, fan, oil pump group and control components into four independent mechanisms. It is characterized by large volume, high output power, mostly gas ignition system, relatively large adjustment, generally 1:4~1:6, even up to 1:10, low noise, and low requirements on fuel quality and environment. This type of machine is often used in road construction industries at home and abroad, such as "Parker" in the UK, "Tanaka" in Japan, and "ABS" in Italy.
1.3 Structural composition of the burner
The automatic control burner 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 the fuel to be completely burned. Different fuels have different air volume requirements. For example, under the standard pressure state of No. 0 diesel oil, 15.7m3/h of air must be distributed for each kilogram of oil to be completely burned. The heavy oil with a heat value of 9550Kcal/Kg needs to distribute 15m3/h of air in order to completely burn it.
(2) The fuel supply system must provide reasonable combustion space and mixing space for complete combustion of fuel. Fuel delivery methods can be divided into high-pressure delivery and low-pressure delivery. Among them, the pressure-type atomizing burner adopts high-pressure delivery mode, and the pressure requirement is 15-28bar. The rotary cup atomizing burner adopts a low-pressure delivery method, and the pressure requirement is 5-8bar. At present, the fuel supply system in the road construction machinery industry mostly adopts high-pressure delivery.
(3) Control system The road construction machinery industry uses burners with mechanical control and proportional adjustment due to the particularity of its working conditions.
(4) Combustion system The shape of the flame and the completeness of combustion basically depend on the combustion system. The flame diameter of the burner is generally required to be no more than 1.6m, and it is better to adjust it wider, generally set at about 1:4 to 1:6. If the diameter of the flame is too large, it will cause serious carbon deposits on the furnace tube. If the flame is too long, the temperature of the exhaust gas will exceed the standard, which will damage the dust bag, and will also burn the material or make the material curtain full of oil. Take the 2000-type mixing plant in our unit as an example: the diameter of the drying cylinder is 2.2m and the length is 7.7m, so the maximum diameter of the flame cannot exceed 1.5m, and the length of the flame is preferably adjustable within 2.5-4.5m.
2 Maintenance of the burner
(1) Pressure regulating valve Regularly check the fuel pressure regulating valve or pressure reducing valve to determine whether the surface of the lock nut on the adjustable bolt is clean and removable. If the surface of the screw or nut is dirty or rusty, the control valve needs to be repaired or replaced.
(2) Oil pump Check the oil pump regularly to determine whether the sealing device is intact and whether the internal pressure is stable, and replace the damaged or leaking sealing device. When using hot oil, check that all oil lines are well insulated.
(3) The filter installed between the oil tank and the oil pump must be cleaned regularly and checked for excessive wear, which can ensure the smooth arrival of fuel from the oil tank to the oil pump and reduce the possibility of potential component failure. The "Y" filter on the burner should be cleaned frequently, especially when heavy oil or residual oil is used, to prevent the nozzle and valve from being clogged. When working, 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 line and check the line for leaks.
(5) Check whether the inlet protection device on the combustion and atomizing air blower is installed correctly, and whether the fan casing is not damaged or leaked. Observe the operation of the blades, if there is too much noise or vibration, adjust the blades to eliminate them. For blowers driven by belt pulleys, lubricate the bearings regularly and tighten the belts to ensure that the blowers can generate rated pressure. Clean and lubricate the joint of the air valve to see if the operation is smooth, and replace the parts if there is any obstacle in the operation. Determine whether the wind pressure meets the working requirements. If the wind pressure is too low, it will cause tempering, which will lead to overheating of the guide plate at the front end of the drum and the material shifting plate in the combustion zone. If the wind pressure is too high, the current will be too large, and the temperature of the bag will be too high or even scorched.
The development of automatic control burners has been serialized such as light oil machines, heavy oil machines, gas machines, and oil-gas dual-purpose machines. Reasonable selection and maintenance of the burner can save a lot of money and prolong the life of the combustion system. In recent years, in the face of the decrease in profit caused by rising oil prices, many asphalt mixing plant operators have begun to look for suitable alternative fuels to improve their competitiveness. Due to the special factors of its working conditions and the site of use, road construction machinery has always been biased towards the use of fuel oil burners. In the past few years, light oil was mostly used as the main fuel, but due to the continuous rise in the price of light oil, the cost has increased rapidly, and in recent years most of them have focused on the use of heavy oil burners. A cost budget comparison of light and heavy fuel oil models is now made for reference:
For example, the daily output of a 3000-type asphalt mixing plant is 1800t, and it is used for 120 days per year, and the annual output is 1800×120=216000t. Assuming that the ambient temperature is 20°, the discharge temperature is 160°, the moisture content of the aggregate 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=6.804 million yuan.
Heavy oil price: 1800-2400 yuan/t, four months cost 1800×1512=2.7216 million yuan or 2400×1512=3.6288 million yuan. After four months, the use of heavy oil burners can save 4.0824 million yuan or 3.1752 million yuan.
While the demand for fuel is changing, 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 construction units. However, there are many burner manufacturers and different brands. Only when the burner is selected properly can the above requirements be met.
1 Selection of different types of burners
1.1 The burner is divided into pressure atomization, medium atomization and rotor atomization according to the atomization method
(1) Pressure-type atomization is to deliver fuel to the oil nozzle through a high-pressure pump for atomization and then mixed with oxygen for combustion. It is characterized by uniform atomization, simple work, less consumables, and low cost. At present, most road construction machinery All choose this kind of atomization model.
(2) Medium atomization is through 5~8kg of compressed air or pressurized vapor pressure to the periphery of the oil nozzle and fuel for premixing and then combustion. It is characterized by low requirements for fuel (such as residual oil and other poor oil products), but There are many consumables and the cost is high. At present, this type of machine is rarely used in the road construction machinery industry.
(3) Rotor cup atomization is to use a high-speed rotor disc (about 6000 rpm) to remove the fuel from the atomization. It can burn poor oil products, such as high-viscosity residual oil, etc. However, the model is expensive, and the rotor disc is easy to wear, which requires high debugging. At present, the road construction machinery industry basically does not use this type of machine.
1.2 According to the machine structure, the burner can be divided into one-piece gun type machine and split gun type machine
(1) The integrated gun machine is a combination of fan motor, oil pump, chassis and other control components. It is characterized by small size and small adjustment ratio, generally 1:2.5. High-voltage electronic ignition system is mostly used, and the cost is low, but Higher requirements on fuel quality and environment. This type of equipment can be used for equipment with a material output of less than 120t/h and diesel fuel, such as the German "Weissout".
(2) The split gun machine is to divide the main engine, fan, oil pump group and control components into four independent mechanisms. It is characterized by large volume, high output power, mostly gas ignition system, relatively large adjustment, generally 1:4~1:6, even up to 1:10, low noise, and low requirements on fuel quality and environment. This type of machine is often used in road construction industries at home and abroad, such as "Parker" in the UK, "Tanaka" in Japan, and "ABS" in Italy.
1.3 Structural composition of the burner
The automatic control burner 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 the fuel to be completely burned. Different fuels have different air volume requirements. For example, under the standard pressure state of No. 0 diesel oil, 15.7m3/h of air must be distributed for each kilogram of oil to be completely burned. The heavy oil with a heat value of 9550Kcal/Kg needs to distribute 15m3/h of air in order to completely burn it.
(2) The fuel supply system must provide reasonable combustion space and mixing space for complete combustion of fuel. Fuel delivery methods can be divided into high-pressure delivery and low-pressure delivery. Among them, the pressure-type atomizing burner adopts high-pressure delivery mode, and the pressure requirement is 15-28bar. The rotary cup atomizing burner adopts a low-pressure delivery method, and the pressure requirement is 5-8bar. At present, the fuel supply system in the road construction machinery industry mostly adopts high-pressure delivery.
(3) Control system The road construction machinery industry uses burners with mechanical control and proportional adjustment due to the particularity of its working conditions.
(4) Combustion system The shape of the flame and the completeness of combustion basically depend on the combustion system. The flame diameter of the burner is generally required to be no more than 1.6m, and it is better to adjust it wider, generally set at about 1:4 to 1:6. If the diameter of the flame is too large, it will cause serious carbon deposits on the furnace tube. If the flame is too long, the temperature of the exhaust gas will exceed the standard, which will damage the dust bag, and will also burn the material or make the material curtain full of oil. Take the 2000-type mixing plant in our unit as an example: the diameter of the drying cylinder is 2.2m and the length is 7.7m, so the maximum diameter of the flame cannot exceed 1.5m, and the length of the flame is preferably adjustable within 2.5-4.5m.
2 Maintenance of the burner
(1) Pressure regulating valve Regularly check the fuel pressure regulating valve or pressure reducing valve to determine whether the surface of the lock nut on the adjustable bolt is clean and removable. If the surface of the screw or nut is dirty or rusty, the control valve needs to be repaired or replaced.
(2) Oil pump Check the oil pump regularly to determine whether the sealing device is intact and whether the internal pressure is stable, and replace the damaged or leaking sealing device. When using hot oil, check that all oil lines are well insulated.
(3) The filter installed between the oil tank and the oil pump must be cleaned regularly and checked for excessive wear, which can ensure the smooth arrival of fuel from the oil tank to the oil pump and reduce the possibility of potential component failure. The "Y" filter on the burner should be cleaned frequently, especially when heavy oil or residual oil is used, to prevent the nozzle and valve from being clogged. When working, 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 line and check the line for leaks.
(5) Check whether the inlet protection device on the combustion and atomizing air blower is installed correctly, and whether the fan casing is not damaged or leaked. Observe the operation of the blades, if there is too much noise or vibration, adjust the blades to eliminate them. For blowers driven by belt pulleys, lubricate the bearings regularly and tighten the belts to ensure that the blowers can generate rated pressure. Clean and lubricate the joint of the air valve to see if the operation is smooth, and replace the parts if there is any obstacle in the operation. Determine whether the wind pressure meets the working requirements. If the wind pressure is too low, it will cause tempering, which will lead to overheating of the guide plate at the front end of the drum and the material shifting plate in the combustion zone. If the wind pressure is too high, the current will be too large, and the temperature of the bag will be too high or even scorched.