Questions of Suppliers concerning procurement part No. 4: System of flue
gas analyzers for laboratory application.
Question 1: Is it necessary to supply SO2 analyser with analysis method UV fluorescence or would it be
possible to offer analyser with NDIR analysis method (the same like for CO-CO2 module)? Analysers with
UV fluorescence method are used in ambient air quality measurements! UV fluorescence analysis method
is not compliant with any standard methods for Emission measurement => it is much more efficient to
add SO2 module into the NDIR analyser with CO + CO2 measurement.
Answer: We would like to mention that the main purpose of procuring the system of flue gas analysers
is to purchase an equipment intended for investigation of combustion processes of different kind of
biofuel and solid recovered fuel. Therefore the range of emissions and its’ concentrations could be very
variable. To be sure that we will be able to detect the emissions in quite wide concentrations range we
worked out technical specification of equipment that could operate in wide range of detection, would be
sensible and would apply detection method, which has the lowest interference from other possible
emissions. In this case the UV fluorescence method for SO 2 analyses in combustion products meets our
basic requirements for the equipment. According to the literature of measuring technique, our own
experience and experience of other similar laboratories, UV fluorescence and NDIR methods are most
suitable for SO2 analyses. However UV fluorescence method has advantages when low values of SO 2 are
measured and has wider measuring ranges.
We should particularly mention that all analyzers (except CO and CO 2) should operate individually
(separately) and not be part of each other, in order to have independent operation in case if one or
another analyser has encountered technical problems, or is under technical supervision or repair.
Question 2: Would it be possible to offer heated line with 4/6 mm tube instead of 6/8 mm? Solution
with 4/6 mm is better because of shorter response time. 6/8 mm heated line doesn’t provide any
advantages.
Answer: It is possible to offer either 4/6 mm or 6/8 mm heated line, however this choice should not
interfere in reliable and appropriate function of the whole offered system.
Question 3: Our solution doesn’t need any additional pump except if distance is longer than 50 m. Could
you specify the length of heated line? Is it possible to omit additional pump (item 3) case if the length of
heated line will be shorter than 50 m?
Answer: We have doubt that it will be possible to control and supply the flue gas for five analysers with
one pump due to different inlet conditions of every analyser. The relevant answer is presented below in
an answer to question 5.
Question 4: Whether data acquisition system and software for data collection and data acquisition shall
be delivered together with the equipment?
Answer: The data acquisition system and software for data collection is not required in the tender
technical specification.
Question 5: Quantity of sample probes, sample lines and analyser protection cabinets:
In our opinion it is not recommended to integrate all requested analysers into one common analyser
protection cabinet. We would like to suggest to apply 2 cabinets, the first one for integration of the "hot"
analysers (FID and Chemiluminescence) and the second one for the cold path of analysers (NDIR, UV
and paramagnetic).
Reasons:
The hot 19"-analysers cannot be mounted one onto the other compactly because of the need of heat
dissipation from hot surfaces. In summary we would have to implement 3 housings into the analyser
protection cabinet, each of them consisting hot parts:
- Housing of the FID analyser (177 mm high, hot surface);
- Chemiluminescence analyser (133 mm high, hot surface of the converter);
- 19"-Module of pumps and ozone scrubber (approx. 222 mm high, hot surface of the ozone scrubber).
It is recommended to install the 19"-Module of pumps and ozone scrubber at the bottom of the cabinet
and the analysers at a comfortable height but with a suitable space between both analyser housings for
safe heat dissipation.
If the cold analytical path consisting of 3 analysers, a sample gas cooler, a sample pump, filters and
valves, would be integrated also into this protection cabinet then it would be very tight and overloaded.
We fear that the heat dissipation would not be possible. This could be a problem.
Please, advise the quantity of cabinets.
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It will be difficult to use one single sample probe and one sample line to feed all analysers from one
source because of 4 different sample pumps (1 pump of the FID, 2 pumps of the Chemiluminescence
analyser and a global sample gas pump for the cold analysers) will have an influence one to the others.
This could also be a problem.
Please, advise, if one probe is mandatory or if 2 probes are requested.
Answer: We have not specified integration schemes of analysers into common system due to possible
variety of analysers and this task is left for own decision of supplier or producer of the system. Technical
specification of the system contains only basic requirements in accordance to measurements, which
should be performed by the system. In this particular case we require that analysers integrated in such
system would operate properly and reliably as long as possible without any failure caused by incorrect
design of the system. Your point of view on system design by separating it in to two separate cabinets
with two separate sample lines and probes is reasonable and acceptable. However, other suppliers may
suggest other acceptable and reliable solutions for integration of analysers.
Question 6: Protection class of the analyser mounting cabinet:
Please advice, which kind of analyser mounting cabinet is mandatory for all bidders. This item is not
described in the specification of the tender. In principle, there are some different solutions which can be
realized:
- 19"-rack(s) without side walls, without backside wall, without front door, without swing frame;
- 19"-rack(s) with side walls, but without backside wall, without front door, without swing frame;
- 19"-cabinet(s) with side walls, with backside wall, with swing frame, without front door;
- 19"-cabinet(s) with side walls, with backside wall, with swing frame, with front door made of steel (IP
54);
- 19"-cabinet(s) with side walls, with backside wall, with swing frame, with front door made of glass
(IP54).
Please, note that a cabinet with IP54 must be cooled by an electric air conditioning unit.
Answer: Basic requirements for analysers mounting cabinet or cabinets are:
- XX"-rack(s) with side walls, but without backside wall, without front door, without swing frame (IP20)
Question 7: Analysis method for SO2 analysis:
The specified UV fluorescence method is a typical emission monitoring method, mainly applied in the
USA. Only one analyser is able to measure in the higher ppm range (Teledyne Model 6400EH). All other
known analysers are designed for ppb ranges and small ppm ranges only and cannot be applied for this
tender. Common methods of SO2 analysis used in Europe are NDIR and NDUV. These methods are used
in thousands of emission monitoring systems in European countries. A lot of European manufacturers are
producing NDIR analysers. NDIR analysers are robust, very stable over a long time and need only low
maintenance efforts. Disadvantages of NDIR and NDUV are the limited possibility to measure low values
of SO2 and the limitations concerning the measuring ranges (depends on the internal optical path length
in the sample cell).
Answer: This question is already analyzed in answer to Question 1.
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