LAR Process Analysers QuickTOC ultra - Proceeding; Advantages; The Measurement Principle of the Tconly Method

12 Instruction Manual QuickTOC
®
ultra
IECEx 12E5119
2 Operating Principle of the Analyser
2.6 The Measurement Principle of the TConly Method LAR | PROCESS ANALYSERS AG
bustion gasses are then cleaned by the filters. Then the CO
2
concentration is determined in a NDIR de-
tector and output as the TOC.
2.5.2 Advantages
The direct method is recommended for determining the TOC when the concentration of the anorganic
carbon is considerably greater than the concentration of the organic carbon. Furthermore, the direct me-
thod is recommended when it is known that the sample contains hardly any volatile carbon, and thus
cannot be lost during the purging process:
TOC = NPOC + POC/VOC
(POC/VOC = 0)
TOC = NPOC + 0
TOC = NPOC [mg/l C]
Summing up the advantages of the TOC-Direct Method:
• Quick measurement results are available under 90 seconds after stripping.
• For the Multi-Stream-Measurement, there is no addition of measurement times, enabling sample
concentrations to be determined quicker overall.
• Prevention of impurities from organic substances in the sample vessel, and possibly in the sample
tubes, because adding acid has a kind of cleaning effect.
• Lower consumption of reagents (1% HCl). Only 5 to 6 litres are used in six weeks at measurement
frequency of 12 minutes.
2.6 The Measurement Principle of the TConly Method
2.6.1 Proceeding
First, the sample is transferred into the sample vessel via the inlet by the help of a peristaltic pump, be-
fore the sample is injected into the ceramic furnace via the injection system.
The sample oxidises completely to CO
2
at 1,200°C in the ceramic furnace. After the oxidation a carrier
gas, which flows continuously through the ceramic furnace, transports the measurement gas to a cooler.
The water vapour produced by oxidation is condensated out by the cooler, and remaining corrosive com-
bustion gasses are then cleaned by the filters. Then the CO
2
concentration is determined in a NDIR de-
tector and output as the TC.
2.6.2 Advantages
The TC only method is the correct choice when the concentration of the organic carbon is considerably
greater that the concentration of the anorganic carbon, especially when the anorganic fraction can be
Notice
Depending on the application, hydrochloric acid concentrations between 3 %
and 5 % can be used.
Please contact your local partner or the Technical Support of LAR
(Chapter 15 on page 283) before using other concentrations.
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