| The The pulverized coal burner has become the preferred equipment for aggregate drying in asphalt pavement construction because it can produce high temperature eddy current,complete combustion,smoke and dust elimination,high efficiency and energy saving,and reduce labor intensity in a short time.However,how to coordinate the high efficiency combustion technology and low NOx emission technology is the main problem in the design of pulverized coal burner.The key to reduce NOx generation and emission is to control the temperature of combustion area,but low temperature combustion affects the combustion rate of pulverized coal.At the same time,the high temperature of the dried aggregate is easy to cause asphalt aging,and the low temperature will make the asphalt coated aggregate uneven affect the quality of the pavement.Therefore,it is particularly important to carry out targeted research on the control mechanism of relevant parameters and system realization based on the multi-stage multi nozzle air supply guiding structure specially designed by the aggregate drying pulverized coal burner,focusing on how to improve combustion efficiency and reduce NOx generation and emission.In this paper,the pulverized coal burner of LB2000 asphalt mixing plant is selected as the research object,aiming at the constant flame temperature,combustion economy and safe operation of the burner,and taking the air volume and pulverized coal volume as the main control quantity,the flame temperature and oxygen content of flue gas of the pulverized coal burner are controlled.The main contents of this paper are as follows:1.Based on the engineering requirements of aggregate drying process for the flame temperature of pulverized coal burners,a mathematical model of flame temperature control is established.The flame temperature control system of pulverized coal burner is established by using MATLAB software.By comparing and analyzing two algorithms of common PID control and self-adaptive fuzzy PID control,it shows that the self-adaptive fuzzy PID plays a significant role in flame temperature control,which can reduce the flame fluctuation of pulverized coal combustion and enhance the anti-interference ability.2.The oxygen content and flame temperature of flue gas will be affected by controlling the ratio of air volume and coal powder.However,the oxygen content of flue gas is an important indicator of combustion efficiency.Because the pulverized coal burner is a multivariable control system,the fuzzy decoupling control algorithm is used to analyze the simulation results through the Simulink platform,which weakens or eveneliminates the correlation between the oxygen content of flue gas and the flame temperature,and effectively controls the oxygen content of flue gas.3.According to the general requirements of pulverized coal burner,the control system of pulverized coal burner is determined.Combined with the high temperature and high radiation working environment of the pulverized coal burner,the current sensor is used instead of the voltage sensor in the selection of the hardware of the pulverized coal burner.In order to overcome the characteristics of high energy consumption and low control sensitivity of the damper,the primary air and secondary air volume of frequency control,as well as the selection of flame temperature and oxygen content detector of flue gas under high temperature conditions are selected.The simulation results show that the self-adaptive fuzzy PID control method has a remarkable effect on controlling the flame temperature of the pulverized coal burner.Through the fuzzy decoupling control of the air volume and the pulverized coal quantity,the oxygen content of the flue gas is controlled at 4.5%.S7-300 PLC can be directly equipped with thermocouple module,and frequency control can be used to make the pulverized coal burner work more stable.The research methods and conclusions of this paper have certain reference significance for the development of aggregate drying pulverized coal burner. |
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