The Research And Development Of Self-ignition Temperature Detector For Hazardous Liquid Chemicals

The implementation of the EU REACH legislation forces the exporters of our country to provide the EU with dozens of physical and chemical parameters of the liquid chemicals such as self-ignition temperature. But the exploration of spontaneous combustion point detection device for liquid dangerous chemicals is very lack in our country. It makes the design and research of the self-ignition point detection device for liquid dangerous chemicals necessary. So the research is of important practical significance.Based on the detection principle and the method provided by the ASTM-E659 (2005) standard. Designes a self-ignition point detection device for liquid dangerous chemicals. Focus on the hardware circuit, temperature control method and the system software for in-depth research and careful design. The simulation of some core modules is carried out and the detection device is validated by test.The hardware circuit mainly includes the furnace chamber temperature detecting circuit, the combustion chamber temperature detecting circuit, heating control circuit and so on. Make AT89C51 single-chip microcomputer as the main control core. The furnace chamber temperature detecting circuit and the combustion chamber temperature detecting circuit basing on K type thermocouple realize the purpose of precise control for the furnace chamber temperature and the precise detection for the combustion chamber temperature. The heating control circuit use the SSR as the actuator to control the heating circuit switching on and off. Realizing the reliable control of the heating circuit. The design of alarm circuit and spontaneous combustion detection circuit realize the automatic detection of spontaneous combustion phenomenon and greatly reduces the test personnel’s labor intensity of focusing the mirror to observe the spontaneous combustion phenomenon. In addition, also designed the keyboard and display circuit,realizes the benign interaction between detection device and test personnel. Through the use of distinctive voltage chip components Power supply circuit achieved the stability output of different voltage.The pulse width modulation method is selected as the temperature control method to control the heater power. Calculating the duty ratio of a heating period through the digital incremental PID control algorithm. So obtained the proportion of connected time of the heating circuit in a heating period. so realize the purpose of controling the heating power.Based on the idea of modular design,developed the main program, the button detection program,the display program, A/D conversion program, Thermocouple linearization processing program, the progeam of PID control algorithm. All of these constitute the system software of the test device.The temperature detection module, display module,keyboard input module and other core module are simulated though the using of keil and Proteus software. We use the sold 93# gasoline, alcohol, acetic acid as the test material to do the preliminary detection test through the simple trial device.The simulation and test results show that the system hardware circuit design is reasonable, software code is correct,the system is of high precision and strong reliability.