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Gas Fraction Control System for a Gas Evolving Electrochemical Reactor

Gas Fraction Control System for a Gas Evolving Electrochemical Reactor. Craig E. Nelson - Consultant Engineer. Reactor Controller Functional Diagram. Cathodic (“Negative”) current. Electric “Eyes”. Standby. Standby Current Source. Bubble. Set Point. Counter – Anode – Ec – Red. +.

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Gas Fraction Control System for a Gas Evolving Electrochemical Reactor

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  1. Gas Fraction Control System for a Gas Evolving Electrochemical Reactor Craig E. Nelson - Consultant Engineer

  2. Reactor Controller Functional Diagram Cathodic (“Negative”) current Electric “Eyes” Standby Standby Current Source Bubble Set Point Counter – Anode – Ec – Red + Voltage Controlled Power Supply Loop Dynamics Circuit - Working – Cathode – Ew Blue-Green Parameter Extraction Circuit Sensor Support Circuit Block Diagram for “Bubbleostatic” Operating Mode

  3. Reactor Control System Block Diagram Current Drivers Power Supply Detection Parameter Extraction Standby Current Source I2 Standby Bubble Detector Support Circuit Voltage Controlled Current Source V1 Parameter Extraction Circuit V2 V3 V4 V5 I1 Signal Smoothing Circuit Loop Dynamics Circuit Controller Set point Iout Det1 Det2 Photons “PID” Loop Dynamics

  4. Requirements - Loop Dynamics • Controller should provide at least a second order transfer function • Controller should provide easy adjustability of the transfer function dynamics

  5. Loop Dynamics - The PID Controller

  6. Concept 1 – Absolute Amplitude Feedback Vout Integrate Input scaling and offset Output scaling and offset V1 V4 V5 Amplify Differentiate Vin Set point “PID” Dynamics

  7. Parameter Extraction • Accept signals from one or more concentration sensing sources • Pre-process the sensor signal as required • Extract various parameters from the concentration sensor as required • 4. Scale and offset the parameter signals as required

  8. Typical Bubbleogram 512 Samples

  9. Typical Bubbleogram Descriptive Statistics

  10. Power Spectral Density

  11. Autocorrelation

  12. Current Noise Signal Analysis

  13. Current “Noise” Signal

  14. Current “Noise” Power Spectral Density

  15. Current “Noise” PSD

  16. Current “Noise” Autocorrelation Functions

  17. Current “Noise” Autocorrelation

  18. Cross Comparison – Bubbleogram vs. Current Noise - Waveforms

  19. Waveforms Bubbleogram Current Noise

  20. Cross Comparison – Bubbleogram vs. Current Noise – Power Spectral Density

  21. Power Spectral Density Bubbleogram Current Noise

  22. Cross Comparison – Bubbleogram vs. Current Noise – Autocorrelation

  23. Autocorrelation Bubbleogram Current Noise

  24. System Control Parameter Extraction - Amplitude

  25. Concept 1 – Absolute Amplitude Feedback Input scaling and offset V1 V2 Signal Smoothing Absolute Value Vout Vin

  26. Concept 2 – Detrended Abs Amplitude Feedback mean(V2i …V2i+N) V2 = median(V1i … V1i+N) V3 Mean Estimator BUset Bubbles In BLset Var(V2i …V2i+N) V4 V1 V2 V5 = 1 if (V4 > BUset) Variance Estimator + LP Filter Boundary Alarm Generator Bubble Detector Detrender V6 = 1 if (V4 < BLset) V5 V6 V7 = Pu if (V5 =1) Integrator Preset V1 V2 V8 = Pl if (V6 =1) V7 V8 Median Filter Vset V9 V10 Integrator Cell Driver med(V2i …V2i+N) Vout

  27. The “Median” Filter

  28. Concept 2 – Bubble Rate Feedback Input scaling and offset V1 V2 Differentiator and Limiting Amplifier Pulse Rate to Amplitude Converter Vout Vin

  29. Cell Driver – Block Diagram Standby Mode Select DC Power Vin Cell Driver Power Amplifier V1 V3 V4 V6 Vout - Iout Current Sensor Input scaling V8 V2 V5 Standby Controller Cell Driver Feedback Network V7 Standby Current Set point Current Monitor

  30. Summary and Conclusions A system concept has been developed and presented A parameter extraction strategy has been presented These methods can be used to extract gas fraction information from gas bubble sensing devices

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