Flue Gas Sulfur Dioxide Concentration Of Intelligent Detection Apparatus

Sulfur dioxide disserves badly the environment as the main air pollutant . And the combustion process of the coal , petroleum etc is the main artificial pollution sources which discharges the sulfur dioxide, so it has very important meaning to measuring the concentration of sulfur dioxide in fume.The paper has analyzed the methods about measuring the concentration of sulfur dioxide and detector for concentration of sulfur dioxide in fume abroad and at home at present. Based on electrochemistry sensor of sulfur dioxide, we have developed a kind of low cost and high accuracy intellectual detector which can detect the concentration of sulfur dioxide in fume and can adapt to more abominable environment. The measuring principle, overall structure, hardware design, the realization of the software and design of the communication interface of the detector are provided in detail in the paper.The potentiostatic sensor 3SF CiTiceL of sulfur dioxide made by City Technology, which has three electrodes and outputs linear direct current, is applied in this paper. Potentiostatic instrument is used to control the voltage that the sensor needs. Because the output current signal of the sensor is very faint, the potentiostatic control and the disposal of current signal become very important, and deep research about these is described in this paper.The detector consists of fume route and circuit in the hardware. According to the characteristic of the sensor, the structure of two sensors in the fume route is adopted, and the temperature of fume is lowered naturally and the water in fume is got rid of fast by separator of gas and water. The hardware circuit design of System which is given in the paper, includes the circuit of detecting sulfur dioxide concentration, temperature and humidity; driver circuit of pump and valve; communication interface circuit; setting circuit of baudrate and address. Based on AT89C52 singlechip, the detector converts the faint current signal of sulfur dioxide sensor to voltage signal through I/V convertor and pre-amplifier, then through multi-range, highaccuracy A/D convertor, the signal of sulfur dioxide concentration is stored in the singlechip in the form of digital. In the system, we provide the general standard RS-232/485 serial interface, study the V/I converting circuit and have designed a 4~20mA linear current interface.We have probed into application in the embedded system of C language in software design, and have fully utilized the abundant library functions and strong data processing ability of C language. The software includes 3 parts: controlling, data processing and communication procedure.. In the paper, we give the method of checking form based on module 2 by searching the 16 bits Cyclic Redundancy Check Code (CRC-CCITT) . Experiments show that the dependability in system communication is guaranteed and the computational speed is greatly improved.In the detector, we adopt a series of anti-interference measure such as shielding, hardware and software filtering to satisfy the use in industrial environment.The focus of this paper is: the circuit design of potentiostatic instrument and signal processing for sulfur dioxide; the communication interface design and realization of the system software. At present, the circuit and software part of the detector have already been finished. By the software and hardware debugging, it is proved that all functions of the prototype of the detector can already be realized.This detector is suitable for concentration measuring in fume desulfurization project and other relatively sulfur dioxide measuring of high concentration, and the successful development has greater using value.