Process control, automated proportional

Proportional-plus-integral control is the most generally useful control mode and therefore the one usually applied to automated process-control. Its major limitation is in processes with large dead-time and capacitance if reset time is faster than process dead-time, the controller-response changes are faster than the process, and cycling results. In these cases, derivative control is beneficial. 

Of course, the effort to achieve automation has to be in proportion to the resulting benefits, so the question is how to make a microprocess system automated with adequate effort. Can we just use standard process control systems from normal process automation for microprocess systems also. Or is the development of dedicated automation solutions just for microsystems required and feasible ... 

In the normal operation of the reactor the flow rate and composition of the HiS feed stream both fluctuate. In the past, each time either variable changed the required SO2 feed rate had to be reset by adjusting a valve in the feed line. A control system has been installed to automate this process. The H2S feed stream passes through an electronic flowmeter that transmits a signal Rt directly proportional to the molar flow rate of the stream, hi. When hf = 100 kmol/h. the transmitted signal R = 15 mV. The mole fraction of H2S in this stream is measured with a thermal conductivity detector, which transmits a signal R. Analyzer calibration data are is follows ... 

The X-ray analysis system for the EMA is a wavelength dispersive spectrometer with gas proportional counter detectors. In the SEM, an energy dispersive X-ray spectrometer with a Si(Li) detector is used. The entire electron and X-ray optical systems are operated under a vacuum of about 10 torr. Modem systems are completely automated with computer control of the instmment parameters, specimen stage movement, data collection and data processing. 

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