Some Very Useful References

  1. Faanes, A.; Skogestad, S.; “pH-neutralization: Integrated Process and Control Design”, Comp. & Chem. Engr., 28, 1475-1487, (2004).
  • Discusses control related design issues and their importance in industry.
  1. Henson, M.A.; Seborg, D.E.; “Adaptive nonlinear control of a pH neutralization process”; IEEE Transactions on Control Sys. Tech., 2(3), 169-182, (1994).
  2. Discusses an adaptive nonlinear control strategy for benchscale pH neutralization. Provides experimental evaluations and discussion as to why an adaptive nonlinear controller performs better than a non-adaptive nonlinear controller or a regular PI controller.
  1. Hjelm, S.; “pH Neutralization Operation Manual and Preliminary Testing” Handout (2004).
  2. Describes how to perform the experiment using the laboratory system and computer software. It’s the manual for the lab, need I say more?
  1. Kim, D.K.; Lee, K.S.; Yang, D.R.; “Control of pH neutralization process using simulation based dynamic programming”, Korean J. of Chem. Engr., 21(5), 942-949, (2004).
  • Discusses the problem of dimensionality for the dynamic optimization approach for controlling nonlinear systems with linear models as the size of the system increases. The Neuro-Dynamic Programming approach is presented as a superior method for a pH neutralization process.
  1. McMillan, G.K.; “Methods of controlling pH”; Chem. Processing, 60(7), 58-61, (1997).
  • Discusses importance of pH and has a table that summarizes some “best” practices for minimizing pH maintenance.
  1. Mwembeshi, M.M.; Kent, C.A.; Salhi, S.; “A genetic algorithm based approach to intelligent modeling control of pH in reactors”, Comp. & Chem. Engr., 28, 1743-1757, (2004)
  • Presents genetic algorithm (GA) based linear internal model control for “global” pH reactors. Discusses how they are designed for improving control in highly nonlinear neutralization reactors.
  1. Ogunnaike, B.A; Ray, W.H.; Process Dynamics, Modeling, and Control, New York, Oxford University Press, 461-557, (1994).
  • Process Dynamics and Controls Text.

Recommendations

  • Come in prior to experimentation to make the acid, base, and buffer solutions so that experimentation can begin right away during lab. Make sure to allow the solutions about a half hour to mix by circulating them through the system.
  • Take care when first making the acid, base, and buffer solutions since errors in calculating mixture molarities will severely affect the experimental results.
  • In order to avoid wasting laboratory time, perform a 2 sample calibration on the reactor probe. Errors were often encountered when only a 1 sample calibration was performed.
  • A 1 sample calibration is recommended for the waster tank pH probe since it was found to be effective and wastes less buffer solution
  • The reactor mixer should be operated at low speed when vessel level is low to avoid creating a vortex at the bottom, which would cause level reading inaccuracy.
  • Never allow pH electrode to dry
  • Make sure waste tank has pH between 5 and 9 before emptying.
  • Do not allow waste tank volume to exceed 28 gal. At this volume, an automatic waste tank mechanism will turn on warning that the level is too high and will close all inlet and outlet valves.
  • Holding tank power switch must be on at all times during operation; however, make sure to turn off when calibrating waste tank pH probe.