SUMMARY: A control system for an experimental anaerob biogas reactor for production of biogas (methane) fed with leachate from apple waste is presented. The control system is used to stabilize the gas production by controlling the H2 concentration of the gas. Industry standard PI (proportional plus integral) control is used to adjust continuously the reactor feed flow to keep the measured H2 concentration at the concentration setpoint. The controller is tuned from a mathematical model of the process in the form of a transfer function estimated from a stepresponse experiment on the process. The feed flow range demanded by the controller is in the very lower end of the range of the feed pump, causing problems with obtaining the demanded flow. Satisfactory pump control is obtained with Pulse-Width Modulation where the pump is controlled as a binary (On/Off) device with the average flow being equal to the demanded flow. The noisy H2 measurement signal is smoothed with a lowpass filter before being connected to the controller. Remote Internet-based access to the lab PC is implemented.
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