Appendices

15.6 Appendix E – Two-cell Applications

Ion Exchange

Ion exchange operations can achieve especially precise control using the conductivity ratio of two points with each bed. Ratio measurement accounts for feedwater variations when the upstream point is measured at the cation bed inlet. With the upstream point in the bed as shown for following stages, it can identify exhaustion before breakthrough.

INLET

CELL 2

 

 

 

 

 

 

 

 

CELL 2

 

CELL 2

 

CELL 1

CELL 1

 

CELL 1

DI WATER

 

 

 

 

CATION BED

 

ANION BED

 

MIXED BED

Reverse Osmosis

Reverse Osmosis efficiency is monitored by comparing inlet and outlet conductivity (or TDS). Automatic calculations of Percent Rejection or Percent Passage are provided. If readout is in resistivity, cell locations are interchanged. Temperature readout assists with normalized performance comparisons.

CELL 2

RO UNIT

FEED

CELL 1

PERMEATE

 

CONCENTRATE

Percent Passage =

Cell1 x100

Typical Range is 0 to 20%

 

Cell2

 

Percent Rejection = (1- Cell1 ) x100

Typical Range is 80 to 100%

 

Cell2

 

Conductivity/Resistivity/TDS Difference

Conductivity/Resistivity/TDS difference using redundant cells on critical processes can provide a valuable diagnostic capability. If the difference in measurements exceeds the alarm points, an operator is summoned for corrective action. Monitoring may be switched to the alternate cell during maintenance. For deviation in either direction, two different

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UDA2182 Universal Dual Analyzer Product Manual

January 2009

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Image 224
Honeywell UDA2182 Appendix E Two-cell Applications, Ion Exchange, Reverse Osmosis, Conductivity/Resistivity/TDS Difference