The Research Of Petroleum Products Automatic Distillation-Measuring Instrument

Distillation range is a major indicator to express the liquid fuel evaporability. It can explain the boiling point range of liquid fuel and confirm the approximate content of light and heavy components in the oil. Therefore, as the important control indicator, distillation range has great significance in oil production, use and storage. Compared with foreign products, the domestic petroleum products distillation-measuring instruments need to be improved at measurement accuracy, measurement reliability and the test efficiency.According to the national standard GB/T6536and the ASTM D86proposed by American Society for Testing Materials, this paper designs a kind of petroleum products distillation-measuring system. The system, which consists of the main controller STM32F103RCT6and the secondary controller STM32F103C8T6, can complete the function of the temperature detection, temperature control and liquid level measurement. The system uses a16-bit analog-to-digital converter AD7705to measure the temperature of the oil vapor and control the oil distillation rate through the composition of the piecewise PID control algorithm and the normalized PID parameters tuning. With the4-channel analog-to-digital converter ADS7841to measure the temperature of the condensing tube and receiving room, it achieves the constant temperature control function through the PID control algorithm based on relay feedback auto-tuning. The method of combining the stepper motor and the photo detector can meet the requirements of the liquid level measurement and the distillation rate measurement. By the atmosphere measuring circuit, it is possible to carry out the distillation result correction. The system provides a wealth of information outputs and friendly operating environment through the touch screen with ModBus technology.Through the debugging, the instrument can greatly reduce the workload of the operator and avoid the error caused by artificial factors. The distillation rate control based on piecewise PID algorithm and the constant temperature control with PID parameters auto-tuning can improve the efficiency of petroleum products distillation-measuring. With the features such as stable, reliable and low-cost, this instrument has good application value and market prospects.