The dust removal system is mainly composed of a fan, an electric butterfly valve, a rotary valve, a dust collector, a dust conveying device, a pipe, a valve, etc. Under the attraction of the fan, the dust-containing gas will enter the bag dust collector after the flue gas temperature drops. The dust in the flue gas is removed with a cloth bag, and the purified gas is discharged into the atmosphere from the chimney. Along with the accumulation of dust, the pressure difference increases gradually. When the pressure difference increases to the set value, the dust removal bin will be dusted from bin to bin, and then the dust will be discharged one by one and transported regularly.
The dust removal control system can realize the following functions: to realize high precision intelligent detection of temperature signal and pressure difference signal; to realize temperature control, ash cleaning control and ash unloading control; to have manual / automatic, pressure difference / compulsive control function; It has the functions of historical data storage, real-time data dynamic display, printing and alarm for all the control and detection analog quantity, and can realize parameter setting and remote control in the upper computer for all the controls. The process flow can be dynamically displayed on a computer screen.
Structure and configuration of control system.
According to the characteristics of dust removal control, the dust removal automatic control system is divided into three parts, which are field level (detection instrument, sensor and execution device), lower computer (PLC) and upper computer. The system uses PLC as slave computer to process analog and on-off signals directly, and industrial control computer as upper computer, and uses configuration software to establish a friendly real-time operation interface to communicate with the lower computer. The field instrument mainly detects the process parameters and the running state parameters of the equipment, PLC and distributed I / O through the data scanning to collect the signal and carry on the data processing, then sends the control signal to the spot execution equipment according to the control request to complete the control function. On the one hand, the host computer receives the input signal of PLC, on the other hand, according to the control requirements, it sends control instructions to PLC to monitor the process and realize the function of process data management.
Ash cleaning control.
Ash cleaning control can be achieved according to the needs of manual / automatic control, pressure / forced control. The PLC first judges the control mode of the system, that is to say, the system chooses the forced mode or the differential pressure mode, if the forced mode is chosen, then judges whether or not the ash is cleaned according to the forced cleaning signal; if the system chooses the pressure difference control, The dust-clearing signal is effective only when the differential pressure of the dust collector reaches the set value. If the automatic cleaning mode is selected, after the cleaning signal is effective, the control system will clear the ash in turn for each storehouse. The cleaning process includes two processes: reverse blowing and settling. The times of these two processes and the running time of each process can be set according to the technological requirements.
For high-temperature flue gas purification systems such as furnaces and kilns, temperature control is related to the safety and life of the equipment. If the flue gas temperature entering the dust collector is too high, it will burn out the filter bag or shorten the filter bag life; if the flue gas temperature is too low, the phenomenon of condensation will occur, causing dust to harden on the filter bag, leading to difficulties in cleaning ash, and the resistance of the dust collector will continue to rise or even form a vicious circle. The system is paralyzed. In addition, when the flue gas temperature is too low, the fan load will increase, and the fan motor will be overloaded. Therefore, the temperature must be controlled. The system adjusts the mixing air volume by adjusting the opening of the electric butterfly valve, and realizes the adjustment of the temperature by controlling the air volume. The temperature control strategy is as follows: when the inlet temperature is greater than the fixed value, the electric butterfly valve should be opened immediately; if the temperature is on the high side, the valve should be opened if the temperature is too high and has a rising tendency; and the valve should be opened according to the inlet temperature value to adjust the opening degree of the air mixing valve. If the temperature is on the low side and has a downward trend, turn off the valve properly. The PID algorithm is adopted in the control system. The selection of the proportion, integral and differential constants of the controller is decided by the model of the controlled object and the required optimal objective function.
The upper computer of the system is industrial control computer, which communicates with PLC through industrial Ethernet. The communication medium is optical fiber, which is composed of network card, switch, photoelectric conversion module and PLC communication module. At the same time, the system can be connected with other process control processes in the workshop to form a two-level network to realize the production management. The screen monitor is programmed by Siemens WINCC configuration software with friendly interface. The operator can monitor the whole production process through HMI, and has the alarm and print functions such as parameter setting, each control screen, curve, historical data, print management and so on.
Single check and system debugging.
Single check refers to the operation and debugging of a single device, which is the basis of system debugging. Including all the sensor components, detection instrument output, display is normal, parameter adjustment is correct, motor, hydraulic coupling, fans, valves and other executive devices, start, running state is normal. Monitor their running on the PLC program and HMI, solve the problems in time, prepare for the next step of system debugging. System debugging is the debugging of the entire control system after the end of the single debugging, under the normal operation conditions of all the equipment. Including all the system control, interlocking conditions of the debugging, HMI control procedures and debugging of the monitoring program.
At the end of the system debugging, the system enters the trial operation phase. The trial operation is to complete the debugging of the automatic monitoring system under the working conditions with load. Including the adjustment of some important control parameters in the system. For example, under different operating conditions of electric furnaces, the air volume of the straight row system and the roof cover is different, and the theoretical value and the actual value are always somewhat different, so it is necessary to adjust the rotational speed of the supercharged fan and the main fan under the actual production conditions. It can not only meet the requirements of dust removal, but also save energy.
是否正确，电机、液力偶合器、风机、阀门等执行装置，启动、运行状态是否正常。在PLC程序和HMI上监控它们的运行，出现问题及时排除，为下一步系统联 调做好准备。系统调试是在单体调试结束后，所有设备运行正常的条件下，对整个控制系统进行的调试。包括系统中所有控制、联锁条件的调试，PLC控制程序的 调试及HMI监控程序的调试等。