Steady-state tests have been run on a neutralization tank, where pH is the controlled variable and w is the acid flow rate. The data follow the relationship shown in figure: You are asked to evaluate which type of valve (quick opening, linear, equal percentage) would best match the nonlinear gain relationship between pH and flow rate and give a nearly constant product, Assume a set point of pH = 7 and consider installed valve characteristics. Show appropriate plots for pH between 4 and 10 (note sensitivity to flow rate). If none of the valves is satisfactory, offer an alternative approach for pHcontrol.

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10 PH 6. 0. 3