An in-process monitoring stage
Trend: the areas where online chromatography is used are expanding

In the past two years, process chromatography has increasingly be-come an area of focus. And not just in the petrochemical industry either—for example, the pharmaceutical industry too is looking to use it to exercise direct influence over the process, to improve the end-products.

Maximum product yield, the highest product quality and operational safety, together with economical handling and use of scarce resources, are the buzzwords currently being bandied about at European chemical production plants. Help is to be provided by ever better process analysis, which delivers highly accurate predictions regarding material composition, concentration or purity of one or several product flows, at intervals measured in seconds or minutes, and at the trace level just as much as at the highest concentrations. Using this information, it should be possible to regulate processes better. Whilst traditional laboratory analysis can now provide a full analysis of all the desired parameters, it still remains a truly time intensive solution. Generally, the results come too late for the processes to be optimized in the light of them. The difficulty is that not all laboratory analyses can be converted into online measurement processes. Frequently, their successful transfer is preceded by many long years of development. Gas chromatography has made the leap from laboratory tool to online process technology, and is being further developed down that route.

More efficient use
“We observe major interest in process chromatography in the oil and gas sectors, in the refineries, and in the petrochemical and chemical industries. Given the high prices of primary energy, our customers are interested in more efficient use of raw materials. Measurements are taken upstream, for example in the gas treatment plants at the gas extraction point, during transportation and in the liquefaction plants,” comments Dr. Frank Diedrich, Head of Process Ana-lytics at Siemens Automation and Drives (A&D), describing the current interest. “In the oil refineries, the sulfur limits are being reduced, and the chromatography devices help to achieve high yields through optimized process management. We are also seeking high levels of interest in the environmental field (where chromatographic measurements are used to monitor the discharge of organic substances from flares and cooling towers) in order to achieve the medium-term limits specified for ozone.” “The petrochemical industry is currently showing the biggest interest in online gas chromatography,” is also the opinion of Dr. Roger Ingemey, Analytical Sales & Operations at ABB Automation. The background to this is the constantly raised bar for requirements to reduce sulfur content in fuels of all kinds. Until recently, it was normal only to use offline laboratory testing procedures to measure low sulfur contents in fuels. “Only very few online process analyzers are able to carry out precise and reliable measurements of the total sulfur content, given today’s suggested or prescribed low limits. This situation has changed with the technology used by ABB in its PGC2007 total sulfur analyzer,” explains Ingemey. This device is a gas chromatograph with an oxidation chamber to measure total sulfur. In contrast to other methods, it uses a flame photometric detector (FPD) which has proven its qualities in practical use. The ABB PGC2007 demonstrates above-average levels of replicability and reproducibility. Despite this, its developers are not standing still. Ingemey is convinced that “to keep ‘on the trail’ of the legal limits, which are continuing to fall, we are still required to invest heavily, especially in the aspects of operational safety for today’s process chromatography.”
Emersons new process gas chromatograph, the Model 700, combines the latest technology with a robust build. “Every process gas chromatograph we supply undergoes at least one 24h climatic chamber test with a test gas. With the external temperature range moving from –18 °C to 55 °C or –20 °C to 60 °C, the specifications are checked and this high “out of the box” quality is guaranteed,” says Dr. Achim Zajc at Emerson Process. “The emphasis is on a compact build with standard components (GC columns, screw connections etc.), which can be replaced separately as needed and which are not disposable items, as is the case with micro gas chromatography.” The contact furnace facilitates stable and precise measurements directly in the field and requires neither expensive protective rooms or airconditioning or a compressed air feed. These features result in enormous savings on installation and operating costs. At the same time, chromatography can improve the process in a quite targeted manner, as Diedrich indicates: “When processing bioalcohol and isobutylene to make the fuel additives ETBE and MTBE, the products being dosed needed to be measured in a total of six sample flows as well as for the composition of the intermediate and end-product. Using the Maxum II devices platform, we were able to combine different detectors with flexible furnace configurations and solve the complex measurement challenges using just two devices. Thanks to the fast cycle times and the problem-free interleaving of the individual sample flows, we were able to make critical process improvements.”
From the lab into practice
At Shimadzu, we are currently seeing increased demand in R&D, for example in the monitoring of research reactors, and for quality control in the petrochemicals and chemicals industries. “We are concentrating on automated sample preparation and analysis of liquid samples using gas chromatography and fluid chromatography, and are working on making analysis techniques from laboratory analysis usable for online chromatography as well,” reports Dr. Franz Kramp at Shimadzu . The AOC-5000 Online System is based on a robotic system which can be adapted for a wide variety of sample extraction and injection technologies. Since this is a popularly-used autosampler in laboratory chromatography too, the switch from lab applications to automatic online metering is possible without any noteworthy change. The AOC-5000 Online System works without using valves. This makes it particularly suitable for the metering of reactive and surface-active substances which cannot be recorded without problems using standard systems. “One example is quality control in the manufacture of reactive and/or sensitive substances. Especially with surface-active substances, standard solutions with fluid dosing valves have proven to be unusable,” Kramp reports. It is only the advent of injection-based dosing using the AOC-5000-Online System which has made automated measurements with the desired reliability possible.”
While gas chromatography applica-tions are established for process monitoring, there are generally only one-off solutions for in-process HPLC. The Baychromat from Bayer, a flexible process analysis system is looking to change this. Integrated automated sample preparation means that all stages to prepare the process sample can be carried out online and in a short period. With the help of the integrated ARTS Analyzer Result Transfer Software, it is a simple matter to connect the device to any of the current process control systems. This then opens up the whole field of gas and fluid chromatography. “For the polymer industry, online mole mass determination using gel permeation chromatography (GPC) offers the possibility of being able to improve product qualities significantly, says Hans Tups at Bayer Technology, looking at the possible uses. “Currently there is also increased interest from the pharmaceutical industry in the Baychromat. The integrated sample preparation in particular makes it possible to characterize the course of the reaction where there are syntheses of intermediates and active substances, cyclically and in near time.” This sees the pharmaceuticals industry following the FDA’s PAT Initiative. In its guidance document “PAT—A Framework for Innovative Pharmaceutical Development, Manufacturing, and Quality Assurance”, the FDA encourages pharmaceutical product manufacturers to make use of innovative process analysis. This will enable critical process parameters which are relevant to quality to be monitored online during production and to be adjusted if necessary. “The possibilities for integrated sample preparation in the Baychromat opens up new options for online analysis in environmental monitoring, for substance-specific trace analysis down to the low ppb range, as is shown in the feasibility studies for PAKs,” Tups adds. “ The focus of our development work is in the pharmaceutical biotechnology field. Given the specific requirements of the biomolecules, modifications in sample preparation and in the Baychromat’s analysis module (cooling, low pressures, etc.) are required.
Summary: as well as the new areas of use, the devices themselves offer a lot of freedom in respect of the design. Overall, the trend is towards even smaller values to be measured, but also towards better ease of use, as Dietrich confirms. “We want to become more sensitive, with new trace detectors, and to make the chromatography faster. The starting points for this are further expansion of parallel chromatography and the micro–GC being used on-site, directly at the extraction point.” But a further key focus for development will be on making the complex technologies easier for the user to operate.