Business before pleasure
Make more out of sample gas conditioning: How to Avoid Typical Errors and Problems – Regular measurements and controls have the reputation of an unloved compulsory task. They offer, if properly addressed, a big one Efficiency potential. That’s why it’s important to be serious about the topic from the start Take – for example, in the recovery and processing of sample gases
The author is the Managing Director of AGT-PSG Jörg Erens, Steinbach. Contact: Phone. 49-6171-975026
Notwithstanding the current political Situation and that Resignation of the US government from the Paris Climate Agreement has measuring emissions a significant importance to Compliance with climate protection goals. Only if the measuring technology is sufficient on a quality standard and according to agreed rules, is a reliable comparison of Values at all possible. Since emission measurements are almost always compulsory measurements required by the authorities, they are not always one of the favorite tasks on the part of the operators. Unlike process measurements for quality assurance, yield enhancement, or safety, environmental measurements are not an added value for businesses, and consequently, the willingness to invest is limited. With a wink, some operators have renamed the English abbreviation CEM (Continuous Emission Monitoring) to “Cry Every Morning”. But as is often the case in the funny statement, it is also a true core – so the requirements for measuring ranges and availability are constantly increasing. In order to increase the acceptance in handling and operation of these measurements, two points are essential:
- Optimization of the total costs when buying and operating the
- Reliable and reproducible readings
These goals can only be achieved if the interaction between analyzer and sample preparation works. The trend observed at the Achema, where possible, to measure measurements optically directly in the process (in-situ), necessitates the extraction of the sample (for example because of the pressure conditions or the dust load). According to an analysis by ABB, 70% of all errors in a measurement fall on the sampling, transport and preparation of the sample. This impressive number alone requires a detailed look at the individual aspects of sample preparation. In addition, choosing the wrong components or operating with the wrong settings can even lead to a falsification of the sample
The gas sampling is often carried out in extractive measurements via a probe. Their main task is the filtration of dust and other particles and the avoidance of condensate under consideration of the acid dew points. If it is not heated to the correct holding temperature (which may vary depending on the gas matrix), condensate will precipitate and lead to an uncontrolled washing out of SO2, NO2, HCL, H2S or NH3, which should be avoided under all circumstances. Analogous to the data processing, if the input quality from the primary sample preparation is poor, the subsequent measurement will not be able to give good results either. Two points often lead to massive problems with the gas extraction: on the one hand the housing and the heating of the probe itself and on the other hand the transition / connection of the heated line. Since the gas sampling probes are often installed far above the chimney, there are usually lower ambient temperatures than on the ground. But only with optimum heat transfer from the heating element and additional insulation can the condensate freedom be ensured even under extreme conditions. If the accurate heating of the probe is ensured, the transition to the heated analysis line can be another weak point:
It is essential to ensure that this is provided with an insulation, without which it can lead to the formation of cold spots and thus to condensation. A further weak point can be the heated analysis line: Only if the heating cables are led to the end of the cap, it can come here not only to below the acid dew point, but also to block or even the loss of gases. This is a situation that can be difficult to identify in practice, troubleshooting is very expensive in such cases.
The Chain must agree
The analysis result of a continuous Measurement is always reliable and accurately, though it has all the components in it the sample preparation are. Here comes Companies such as AGT-PSG have a special market position: these offer as a full-range provider to all components for gas processing from extracting to the transport right through to processing from one source.
The line is important
In the gas treatment, the most often underestimated component is the heated analysis line: Does it only in theory the task of removing gas from the gas for processing respectively, she has to get in the practice of a Series of challenges put, which one only can get with a long experience history. This are tasks like laying in long Length by the fireplace as holding the temperature from 180 ° C to 200 ° C on the entire route. As the only manufacturer of heated pipes, AGT-PSG has had production facilities for extruded and flexible pipes for more than 30 years – through this combination, the customer always gets the best technical solution for him. Another innovation that the medium-sized company developed in 2015 is now enjoying great demand: the PSG Hybrid line. It establishes the link between the gas sampling probe and the processing in the analysis room and can be configured so that all necessary components for the operation of the probe are brought along the pipeline: from the power supply via the temperature sensor to the calibration gas. With gas extraction in particularly dusty applications, a backwash is often used, which is used to blow out the filter. The PSG Hybrid also scores points here: the PTFE tube with a 12 mm outer diameter, which is heated to approx. 90 ° C to 100 ° C, eliminates the need to install additional pressure cylinders.
After heating is carried out during gas extraction and transport so that condensation does not occur, the sample gas is cooled during the preparation. However, this involves drying the gas by cooling due to the increasingly sensitive measuring cuvettes as well as the cross-sensitivity of the analytical methods with water. The sample gas cooler must provide the optimum from two disciplines: First, it is about a constant output dew point, which is often required at about 3 ° C. Since the water loadings of the gas can fluctuate due to environmental or process conditions, the heat exchanger must be able to react flexibly to these. A supposedly simple solution, namely to design a heat exchanger with a maximum cooling section, is countered by the second technical challenge: If the sample gas remains in the heat exchanger for a long time, the residence time with the condensate also increases and has a significant influence on the so-called leaching effect. Gas components such as SO2, NO2, HCL, H2S or NH3 combine with water and are washed out via the condensate – so that the gas composition after the cooler is no longer the same as it was before cooling down. To minimize this effect but nevertheless guarantee a constant low outlet dewpoint, AGT-PSG has developed a patented heat exchanger concept. The additional peculiarity of the solution lies in its modular design: From a simple 1-way sample gas cooler, it can be gradually expanded up to 4-gas paths, regardless of whether as “cabinet” version with bevelled display for better readability or as 19 “version. For especially demanding applications with very low measuring range of water soluble measuring gas components the heat exchanger and cooler concept has been developed further. Result is the MAK10 LC with especially low wash out ratio which drys measuring gas very carefully in two cooling stages and guarantees an even more stable low outlet dew point.