On-line Measurement of mercury in concentrated (50%) caustic soda with the PA-2 (left), the sample passes a specially designed dilution system (right).
Installation in a chlorine-alkali plant.
The mercury process analyzer PA-2 is used for continuous monitoring of mercury concentrations in industrial processes. Applications include effluent and quality control in chlorine-alkali plants, monitoring of scrubber water of waste incinerators and power plants, control of industrial sewage and purification plants, quality control of sulphuric acid, drinking water. Special version also for concentrated caustic solutions (NaOH, KOH).
The PA-2 Systems come with either the VM-3000 or the UT-3000 photometer to meet different requirements regarding accuracy and sensitivity of measurements:
0,1 ... 1 µg/l to 0...10 mg/l
0,01 ... 1 μg/l to 0,1 ... 10 μg/l
Thanks to its GoldTrap, the UT-3000 is able to measure mercury in ultra trace concentrations ( ppt range).
In practice mercury analysis sample matrices very often show different and variable compositions. Depending on the chemical process the forms of mercury differ: elementary, ionic, dissolved as a salt, as an organic compound or as insoluble sulfide.
The PA-2 offers a variety of sample pretreatment procedures to allow highly precise determination of total mercury in all these samples, with the results from the PA-2 showing very good correlations with standard laboratory analyses.
High flexibility is achieved by the modular structure of the sample pretreatment module. This allows the user to choose from the different digestion methods, for example:
The integrated heated reaction module boosts sample digestion. The duration of reactions can be adapted to the need of your application by employing reaction coils of different lengths.
The detection of mercury contained in the sample occurs in an optical cell made of fused silica (Suprasil). In a first step mercury is reduced to the elementary state by means of tin(II)chloride or NaBH4. Subsequently mercury is stripped from the aqueous phase with an air stream and carried into the optical cell. Here the UV absorption measurement is conducted at a wavelength of 253,7 nm.
This analytical technique called "cold vapor atomic absorption spectroscopy (CVAAS)" shows extreme sensitivity and selectivity. It has been reliable and proven for many years. In contrast to the occasionally recommended atomic fluorescence method the analytical technique utilized by the PA-2 is extremely low in interference and does not require an amalgamation step nor expensive noble gas as a carrier.
To provide optimum protection against corrosive environments all parts of the PA-2 Mercury Analyzer are enclosed in an industrial-grade cabinet made of fibreglass-reinforced polyester (protection class IP 66; NEMA 4X; etc.).
The electronic circuitry is shielded from the wet chemical section by a chemically resistant wall.
periodically the instrument switches from the sample stream to a calibration solution to check any deviation from the reference value. A status signal is generated if the value measured is out of range.
the zero line of the analyzer is adjusted automatically after a preset period of time.
Precipitations like manganese dioxide are dissolved by an automatic rinse step which makes manual cleaning superfluous.
The PA-2 is operated via a waterproof membrane keypad. All inputs required are selected in a readily understandable menu shown on the graphical display.
The following data are available at the serial interface (RS 232 / USB):
Thanks to the bidirectional interface (option), operational functions like "Zero Adjustment", "Calibration Check" and "Start Measurement" can be triggered externally.
Data displayed during continuous measurement mode
The results of the measurements are displayed in real time and output as analogue 4-20mA signal.
The measurement data can also be fed to a control system or a plotter.
RS 232 / USB outputs enable export of data to a PC or laptop.
The PA-2 is equipped with sensors to detect malfunctions of the system and triggers an alarm for the operator. The following functions/malfunctions are checked and indicated:
These features permit reliable unattended operation.
Malfunctions are reported to the user both optically and via a status signal.
The PA-2 is not a laboratory analyzer simply converted for process applications but has especially been designed for operation under harsh industrial conditions. The number of parts subject to wear has been minimized and particularly durable components have been chosen for use in critical locations. This results in extended maintenance intervals. The stripping unit is based on an aerosol-free principle and the need for cleaning the optical cell is particularly low.
UV absorption (CVAAS),
Wavelength = 253,7 nm
Principle of preconcentration:
(PA-2 Gold only):
Amalgamation on gold surface, thermal desorption by rapid heating (MI GoldTrap)
Electrodeless low-pressure mercury lamp (EDL)
Reference beam method
Fused silica (Suprasil),
Length approx. 230 mm,
heated, approx. 55°C
approx. 1 minute
compressed air, filtered, approx. 30l/h, 1 bar
Tin-II-chloride or Sodiumhydroborate
approx. 3l / week for each reagent
HCl or H2SO4, KMnO4 or H2O2 or Fenton's Reagenz or NaClO3; depending on sample composition
via waterproof membrane keypad
Graphical LC display with background illumination
according to NAMUR 64 recommendations
Fibreglass-reinforced polyester for use in highly corrosive environment - Reagent storage cabinet made of chemically resistent plastic material
IP 66 (EN 60529/ NEMA 3; 3R; 4; 4X; 12; 13)
230 V / 50 Hz (115 V / 60 Hz option)
750 VA max. (PA-2 Gold, heating peak)
approx. 62 x 78 x 33cm (W x H x D)
approx. 50 kg
As a leading supplier of high precision analytical equipment, we strive at all times to offer top quality solutions. Our products are manufactured according to the ISO 9001 quality regulations.