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News Release from: Applikon Analytical | Subject: Cyanide monitoring in steel
Edited by the Processingtalk Editorial
Team on 04 February 2008
Determination of cyanide in steel
industry water
The production of steel involves many different materials and procedures: after top gas purification the scrubbing water contains dissolved cyanide, which must be monitored before any discharge
The production of steel involves many different materials and procedures In order to achieve a smooth, reliable production process and obtain a good product quality, the materials and procedures have to be controlled very thoroughly
This article was originally published on Processingtalk on 29 Nov 2007 at 8.00am (UK)
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One important component in the steel production is process water that is used for cooling the blast furnace and for washing and cleaning of the top gases (blast-furnace gases).
After top gas purification the scrubbing water contains dissolved cyanide and the water can only be returned to the public sewage if the cyanide concentration is below the legal limits.
The ProcessLab setup described here offers a measurement and monitoring solution and provides various options for reacting to any situation.
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With the aid of the input/output controlled, the measured analytical values are easily transferred to the process control centre in the form of 4-20 mA analogue signal.
On the basis of these values, all further process steps are initiated and controlled automatically in the process control centre.
General features of the ProcessLab system.
* Automated measurement of cyanide using the standard addition technique.
* Autonomous action if the cyanide level exceeds a given limit.
* Ready for analysis at any time (24 h).
* Less consumption of CN - containing chemicals due to result on request.
* Analysis time approx 5 minutes per sample.
* Automated monitoring of reagent levels.
The determination of the cyanide content is based on the standard addition method using an ion-selective cyanide electrode (cyanide ISE).
Prior to the first analysis the system is preconditioned using a method which flushes the tubing and the titration vessel.
For the determination ProcessLab automatically transfers a defined amount of water sample into the titration vessel and then a Dosino takes an aliquot (10 mL) in sample loop.
The remaining sample is discharged and the titration vessel rinsed.
Next 15 mL TISAB solution (NaOH, 0.1 mol/L) is transferred into the titration vessel as auxiliary reagent and then the sample is transferred from the loop back to the vessel.
The cyanide content of the water sample is calculated by the standard addition method from the potential measurements performed after each addition of cyanide standard solution.
The amounts of cyanide contained in the treated process waters are normally so small that they are below the detection limit of the ion-selective cyanide electrode.
To obtain a measuring solution whose cyanide content is in the usable linear region of the cyanide ISE, a known amount of cyanide standard solution is added to the original water sample.
This means that at the start of the determination, the measuring solution contains cyanide ions of an unknown but very low concentration from the water sample as well as the exactly known amount of cyanide ions from the standard solution.
After the determination, this known amount of cyanide ions added in step 1 has to be subtracted from the result obtained.
The cyanide concentration of the measuring solution is determined by the standard addition method by adding further cyanide standard solutions.
For further information visit the processlab website.
Literature:.
Dr Haider, Christian (2004) Monograph: Electrodes in potentiometry Metrohm No 8.015.5013.
Metrohm instructions for use: Ion-selective electrodes (ISE) No 8.019.1476.
For further information please contact Metrohm UK. Request a free brochure from Applikon Analytical ...
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