Asphalt mixing station is a complete set of equipment used for batch production of asphalt concrete. Its main function is to produce asphalt mixture, colored asphalt mixture, etc., which has been widely used in road construction.But in the production process of asphalt mixture will produce noise, dust, asphalt smoke and other pollutants, serious pollution of the environment, threatening the health of workers.Therefore, under the background of building a resource-saving and environment-friendly society in China, it is very important to achieve energy saving and consumption reduction in the use of asphalt mixing stations.The following mainly from the impact of the three factors of asphalt mixing station, asphalt mixing station energy saving and consumption reduction measures were explored, in order to reduce the production cost of asphalt, improve the efficiency of mixing station.

Cold aggregate and combustion control

1.1 Water content and particle size of stone

Cold aggregate is the main raw material of asphalt mixing. Because the wet and cold raw materials can not meet the production requirements of asphalt mixing station, it is necessary to use the drying system of asphalt mixing station to dry and heat the stone.The wet and cold degree of raw materials is related to the working intensity of the drying system, the more wet and cold, the greater the workload, especially for some fine aggregates with strong water absorption.According to the study, the energy consumption of sewage treatment equipment stone increases by 10% for every 1% increase in the humidity and cold degree.Thus, the importance of water content control in stone.In the production process of asphalt mixture, it is necessary to take corresponding measures to control the humidity of stone.For example, in order to facilitate drainage, the general stone stacking site set a certain slope, and the ground for concrete hardening, the site must be spacious around, which is conducive to the full evaporation of water.In addition, the site should be set up to shade the canopy, in order to prevent water penetration of the stone when it rains.

In addition to the high humidity requirement of the stone, the drying system also has certain requirements on the particle size of the stone and the shape and regularity of the stone.During the operation of the cold aggregate drying system, the overflow work should be strengthened for the stone whose particle size qualified rate is less than 70%. The consequence of this is the waste of fuel.Therefore, the quality of cold aggregate must meet the quality requirements.The particle size and humidity of cold aggregate have clear specifications, and the particle size should be controlled within 2.36mm.The stone of different particle size is classified to reduce the workload of the drying system

1.2 Fuel selection

A large amount of heat energy will be consumed when heating and drying the wet and cold ore with high moisture content. Therefore, the drying system of asphalt mixing station must select the fuel according to the actual situation.Usually gas fuel (such as natural gas) and solid fuel (coal), these fuels are often used in the combustion performance is not very good, the heat can not be effectively utilized.Therefore, liquid fuels, such as heavy oil and diesel, should be used in the production of cold aggregate drying system.The so-called heavy oil is the fuel oil, the color is black, according to the classification criteria of the international convention, it can be classified into the sustainable oil.Heavy oil is widely used because of its low water content, few impurities, and relatively viscous, not volatile and other characteristics.The price of diesel oil is slightly higher than that of heavy oil, so from an economical and practical point of view, heavy oil is more selective.In addition, the choice of fuel for asphalt mixing station should consider the purity, moisture, combustion efficiency, viscosity and transportation of the fuel, and the fuel should be selected according to the actual situation.The fuel used in the past is heavy oil, which has a great negative impact on human body and the environment. Therefore, choosing the new fuel at the present stage for the purpose of saving energy and reducing consumption can not only reduce the cost, but also play the role of improving environmental benefits.

1.3 Modification of combustion system

To optimize and rebuild the existing fuel system, the main direction is the heavy oil supply pipeline and the addition of heavy oil tank.The first is the fuel addition part, which is equipped with two pneumatic three-way valves, if it can be changed to automatic switch between heavy oil and diesel, it will effectively reduce energy consumption.

1.4 Burner maintenance

(1) Air-oil ratio The feed ratio of air to fuel is maintained, namely, the air-to-oil ratio.The air-oil ratio has a great influence on the efficiency of the burner, so it is necessary to choose the appropriate air-oil ratio to ensure the heat supply while saving energy.

(2) Fuel atomization control The role of fuel atomizer is to improve combustion efficiency and optimize the burner.The atomization measure is a very important link in the combustion, and the appropriate fuel type should be selected according to the specifications of the atomizer used to improve the combustion efficiency.

(3) keep good shape of combustion flame under normal circumstances, the burner jet flame shape should be as follows: burner jet flame center in burner the center of the drying cylinder, the formation of the flame length should be about a third of the burner drying cylinder length, jet flame should be symmetrical distribution, and won’t touch the burner of a drying cylinder wall, normal flame ejected won’t give out sound, also won’t appear jump phenomena.Relative to the position of the nozzle, the flame baffle may affect the length and diameter of the flame, generally 1.5mm.When the flame baffle is close to the nozzle of the burner, the length of the flame will increase and the diameter will decrease at the same time. As long as the distance between the nozzle and the flame baffle is slightly moved, the correct flame shape can be obtained.

(4) do a good job of drying drum insulation work usually asphalt mixing station drying drum surface heat loss range of 5% ~ 10%, in order to effectively reduce the heat loss of drying drum wall, reduce the consumption of fuel, generally adopted method is to dry drum in the asphalt mixing equipment coated with a layer of insulation material.

Insulation of asphalt tank, finished product silo and pipeline

Equipment insulation measures as one of the energy-saving and consumption reduction methods in asphalt mixing station is very important, such as hot aggregate warehouse, finished product storage warehouse, drying drum and heavy oil pipeline, all need to lay insulation layer.The commonly used method is to use the skin to attach 5 ~ 10cm thick insulation cotton ring to the asphalt tank, pipeline or valve and other equipment to form a insulation layer to reduce heat loss.At the same time, due to the service life cycle of the insulation layer, weathering, aging and other phenomena should be repaired in time.

Application of frequency conversion technology in motor drive system

Asphalt mixing plant used in the motor drive for electric energy consumption greatly, the consumption of a large part of the reason is that the asphalt mixing plant equipment and other construction machinery and equipment matching problems between, therefore, it is necessary to scientific and reasonable arrangement, construction machinery to ensure the optimum combination of mechanical equipment, reduce the problems such as frequent downtime, idling, to develop its productive forces, in order to improve the work efficiency, reduce the cost.

3.1 Use frequency conversion technology to control the finished material conveying system

The role of the winch to drive the conveying system is to transport the finished material. In the process of operation, the motor is basically in high voltage operation, which causes the increase of current and the consumption of electricity is inevitably larger.But when it stops, it will produce a larger impact because of its fast speed, which will cause a waste of electric energy.Therefore, the introduction of frequency control technology in the winch driven conveying system, in the whole operation process to start low frequency, transport high frequency, brake low frequency three mode conversion, the correction of the whole high pressure operation mode, can effectively reduce power consumption.

3.2 Frequency conversion technology is used to control the induced draft fan motor

The purpose of induced draft fan is to increase gas pressure and exhaust gas with the help of external energy.Its operation is also inseparable from electricity, and the electricity consumption of its motor in the asphalt mixing station, yes, up to 20% of the total energy consumption.Just like the transport mode of finished material, the working mode of induced draft fan is rigid and always in a fixed working state. The demand for air volume varies in each stage of gas exhaust, so it will inevitably cause unnecessary energy consumption to exhaust gas in a general mode.Therefore, the inverter numerical control technology is introduced into the control of induced draft fan motor, and the high and low frequency conversion is carried out according to the actual requirements of the work, which can not only meet the requirements of the work, but also reduce the power consumption.

3.3 Use frequency conversion technology to control the asphalt circulating pump

The asphalt cycle cycle of the Malian MAC320 asphalt mixing station is 45s/ batch, that is, the mixing time of 15s, plus 30s of the recharging cycle time.Although the asphalt circulating pump is required to work at full load when mixing, but the recharging cycle process is not required, but now the circulating pump is always at full load when working, so the wear and tear of the equipment and the loss of electrical energy will inevitably increase.Therefore, frequency conversion numerical control technology can also be used in this system. High frequency transmission can be selected to meet the requirements of full load of the motor when mixing, and low frequency transmission can be selected when recharging, so as to not only meet the requirements of asphalt production, but also reduce the use of electricity and equipment wear as far as possible.

4 conclusion

To sum up, the asphalt mixing station causes too much energy consumption in the process of operation, which is inconsistent with the trend of social energy conservation, emission reduction and sustainable development.If you want to do a good job in energy conservation and consumption reduction for asphalt mixing plant, the staff can use cold aggregate combustion control and the drying cylinder heat preservation work, and frequency conversion technology in the three ways of motor driver, the energy consumption of asphalt mixing plant effectively control, asphalt mixing station system, comprehensive energy saving work, create a good economic benefit and social benefit, so as to improve the competitiveness of the asphalt mixing plant.