LAR Process Analysers QuickTOC ultra - Proceeding; Advantages; The Measurement Principle of the TOC-Direct Method (NPOC-Method)

12E5119 Instruction Manual QuickTOC
®
ultra
IECEx 11
2 Operating Principle of the Analyser
2.5 The Measurement Principle of the TOC-Direct Method (NPOC-Me-
LAR | PROCESS ANALYSERS AG
2.4.1 Proceeding
First, the sample is transferred into the sample vessel via the inlet. From here, the sample is injected by
the injection system into the ceramic furnace.
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 condensed out by the cooler, and remaining corrosive. Com-
bustion gases are cleaned by the filters. The CO
2
concentration is determined in the NDIR detector dis-
played as TC.
Now the TIC is analysed. For this, the same sample is taken by the injection system from the sample
vessel and injected into the TIC reactor.
Inside the TIC reactor, the inorganic substances are expelled from the sample as CO
2
by introducing an
acid solution and aeration. Then the produced CO
2
-gas is condensed out again by the cooler, and the
gas produced is cleaned by filters and routed to the NDIR detector, which determines the TIC.
Once the TC and TIC are determined, the TOC is calculated using the following formula:
TOC = TC - TIC [mg/l C]
2.4.2 Advantages
In this method, no volatile organic components (POC / VOC) are expelled from the sample. Because all
particles can be measured, all of the TOC remains in the sample - meaning the TRUE TOC is measured
in this method. The considerably greater precision of the result has meant the TOC difference method
applied in the analyser has established itself in waste water analytics. This means the analyser allows
for speedy and accurate analyses of the TOC, TIC and TC parameters in consideration of the POC /
VOC.
Summing up the advantages of the TOC-Difference Method:
• Quick measurement results are available in under 3 minutes.
• For the Multi-Stream-Measurement, no additional of measurement time in needed, enabling sample
concentrations to be determined quicker overall.
• The entire TOC is determined (no loss of purgeable/volatile organics).
• High precision of result.
2.5 The Measurement Principle of the TOC-Direct Method (NPOC-
Method)
2.5.1 Proceeding
In the TOC direct method, the sample is first acidified externally with a strongly diluted hydrochloric acid
before it is moved into the sample vessel. There, CO
2
-free air (carrier gas) continually flows through the
sample. Because of the low pH value (< 2), the anorganics are removed from the sample and drained
off. At the end of this process, the sample only contains the NPOC (Non Purgeable Organic Carbon).
In the next step, the injection system transfers the sample from the sample vessel to the ceramic furnace,
which then completely oxidises to CO
2
at 1,200°C.
The water vapour produced by oxidation is condensated out by a cooler, and remaining corrosive com-