Emerson TCL Principles of Operation, Schematic of Sample Conditioning System and Analyzer

MODEL TCL	SECTION 2
	PRINCIPLES OF OPERATION

SECTION 2. PRINCIPLES OF OPERATION

Total chlorine by definition is the iodine pro- duced in a sample when it is treated with potassium iodide at a pH between 3.5 and 4.5. Typically, acetic acid (or vinegar) is used to adjust the pH.

The total chlorine analyzer consists of a sam- ple conditioning system, which injects the reagent into the sample, and a sensor and analyzer, which measure the amount of iodine produced. Figure 2-1 shows the sample condi- tioning system. The sample enters the sample conditioning enclosure and flows to an over- flow sampler from which the sample pump takes suction. Excess sample drains to waste. At the same time, the reagent pump draws reagent, a solution of potassium iodide in vinegar, from the reagent carboy and injects it into the suction side of the sample pump. The sample and reagent mix as they pass through the pump, and total chlorine in the sample is converted to the chemically equivalent amount of iodine. The flow rates are 11 mL/min for the sample and 0.2 mL/min for the reagent.

FIGURE 2-1. Schematic of Sample Conditioning

System and Analyzer.

The treated sample next enters the flow cell. Bubbles injected into the flow cell produce turbulence, which improves the stability of the reading. A membrane-covered amperometric sensor in the flow cell measures the concentration of iodine. The analyzer receives the raw signal from the sensor and displays the concentration of total chlorine. Display units are ppm (mg/L) chlorine as Cl2. The treated sample leaves the flow cell and drains to waste along with the excess sample.

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