The Research On The Coal Ash Detection Based On Passive Nuclear Level Meter

The coal is indispensable raw materials of thermal power plant in our country. Coal produces a large amount of ash by burning and ash is recovered and reused through ash handling system. Due to the coal ash contains radioactive nuclide that decay and releasey-rays. Using the characteristics of coal ash, passive nuclear material level meter can be used to monitor the height of coal ash in the ash bucket in the thermal power plant.Level measurement plays an important role in the industrial automation systems, it is one of the important measures to ensure the process production and production safety. Level measurement based on the ash of radioactivity is a kind of non-contact measurement, the y ray released by ash itself will be transformed into optical photon by scintillator, and then the photon signal will be transformed into amplified and irregular nuclear pulse signal by photomultiplier tube,so that the main chip can capture.Finally,according to the actual experiments, the mathematical relationships between level and nuclear radiation intensity is established.In this paper the principle of passive nuclear level measurement is researched,the effect of the interaction between material and y-ray is analyzed and the advantages and disadvantages of passive and active is analyzed,and also the hardware structure and working principle of the scintillation detector is analyzed, the shaping principle of hysteresis comparator for nuclear pulse is discussed deeply, and a kind of optimized algorithm of software filtering is put forward. Furthermore, the hardware architecture and software design of passive nuclear level system is shown in this research.On the hardware architecture, passive nuclear level meter includes pre-amplifier circuit, shaping circuit of nulera pulse, processing and controlling unit, wireless communication module. The signal output from the photomultiplier tube first of all to pass through the pre-amplifier circuit and is amplified without distortion, and the shaping circuit enables the function of signal shaping and amplification, then the signal is sent to the controlling uint for processing and the results of processing controls the output of the switch and 4-20mA current. At the same time Micro controller can communicate with the host computer by wireless. The system chooses STM8S105K6 as master chip, and some functions are simply described in this paper; output module includes analog output and digital output, the digital is converted to produce the current of 4-20mA, and output data from microcontroller is used to control relays drived by the transistor; data storage module is used to for computing and calibration-query system; display screen can be intuitive to provide users with the current level value. In the aspect of software, the initialization procedure and functional implementation process of each functional module are presented in details, the software implementation of PC is also shown in the form of flow chart, the software filtering algorithm is discussed deeply in the paper, a new filtering algorithm that combines a variety of filtering algorithms to achieve multi-level filtering is introduced. The code is written by C and G language.The system demarcate some important data through the actual test, various performance indicators are in line with the system design requirements, a feature-rich, manageable passive nuclear level system has come ture.