16


Analytical Instrumentation


Interference-free Sulphur Analysis in Fuels


Dr. Stefan Jezierski, application chemist, Analytik Jena AG, Konrad-Zuse-Str. 1, 07745 Jena Email info@analytik-jena.com Web www.analytik-jena.com Tel +49 (0) 36 41 77-70


There is no question that fuels need to be monitored. During the combustion of carbon fuels, not only the carbon dioxide focused on in public discussions, but also other combustion products arise. In addition to various nitrogen oxides, sulphur oxides are of particular interest. If sulphurous organic substances are combusted, SO2


environment is of vital interest. A major introduction of SO2


from dissolving in water, one of the main causes of acid rain. Especially in Europe, this has caused multiple problems in nature and the environment, agriculture, as well as building damage during the 80s of the 20th century. Thus the intensive control of SO2


as potent toxin, especially in the catalytic converters found in private cars in industrial nations. Furthermore, sulphuric acid (H2 is through the combustion of fossil fuels. Whereas large plants, such


as power stations, often have fl ue gas desulphurisation equipment, the emission from smaller contributors, such as heating systems in houses or cars, must be controlled through the fuel itself. The limit values for sulphur content of fuels for transport were signifi cantly reduced in recent years. In the year 2009 a 100 percent market penetration of sulphur-free fuel (< 10 ppm) was implemented in the European Union, and other industrial and industrialising nations are adapting to these limits. [1] Reductions for other fuel types are being planned. The sulphur content for maritime fuels in the North Sea and Baltic Sea, for example, as well as in the English Channel, is currently being reduced to 0.1% (presently 1.5). The same limit values will apply from that date onwards for the US and Canadian coasts. For the remaining EU waterways a limit of 0.5% (presently 4.5%) is being introduced. [2]


The safe monitoring of the sulphur content in various fuels is therefore a basic requirement for laboratories working in the various sectors of petrochemistry or refi neries. For this purpose they also need a powerful analysis technology that can analyse both the end products and their raw materials.


For the detection of SO2 in combustion gases, detection using fl uorescence induced by ultraviolet


light has been proven to be successful. These UVF detectors have the advantage of measuring the SO2


content in a fl owing gas across a large measuring range. The advantage of UV fl uorescence


compared to other detection methods is its high sensitivity, longterm stability and high applicative fl exibility. This is countered by the problem of cross-sensitivity to nitrogen monoxide (NO) which has a fl uorescence within similar wavelengths.


Experimental All measurements were performed using an elementary analyser from the multi EA®


Sulphur Detection in Fuels


An important requirement for analysis equipment in petrochemistry is the largest possible dynamic measuring range to allow for the analysis of both, raw or intermediate products, often heavy loads and end products with very low concentrations. Table 1 shows an example of this kind of analysis. Two production steps of bio diesel from wood oil were analysed. The raw product had an intensive colour and rather viscous consistency. It was analysed analogue to a solid in the horizontal mode. It was found that the concentration of sulphur in this raw material is rather high with 2400 ppm. The refi ned end product, on the other hand, a clear liquid of low viscosity, could be measured in a vertical furnace position. The sulphur content of less than 5.5 ppm is clearly below the statutory limit values, so that this product may be used as fuel additive or pure.


The high measuring range of the multi EA® 5000


permits the monitoring of the entire production process and can be used for different matrices arising.


Table 1: Sulphur content of bio diesel from wood oil Bio diesel (wood oil)


5000 series.


Dependent on the sample matrix and based on the double furnace option, a horizontal or vertical method could be used. The device also has an integrated gas box for controlling the gas supply as required.


For the horizontal method the multi EA® 5000 (fi g. 1) was equipped with an automatic boat


feeder. This controls, in combination with a fl ame sensor, the feed parameters autonomously and independently of the matrix and thus guarantees the complete conversion of the analytes. The combustion takes place in a two-zone combustion tube. During the fi rst phase the analytes are pyrolised in an argon atmosphere. These pyrolysis gases are passed to the second zone of the combustion tube where they are incinerated at 1050°C in a pure oxygen atmosphere. This produces SO2


O2+R-S ✰SO2


from sulphurous organic compounds in accordance with the following equation: +CO2


+ H2 O The analysis gases are passed to the UVFD module after drying and purifying.


The UV fl uorescence detector used achieves a measuring range of max. 10,000 ppm and min. 5 ppb in sulphur without having to take recourse to rather lengthy procedures, such as “trap and release”.


Quantifi cation took place via a calibration using suitable standards. To this end di-benzo-thiophene was dissolved in ultrapure isooctane. From a 1000 ppm stock solution dilutions in isooctane of up to 50 ppb concentrations were prepared. To prepare a calibration graph, these standards were analysed using the same methods as for the subsequent analytes.


The different fuel types were supplied for combustion either vertically (highly volatile analytes) or horizontally dependent on their viscosity. In both methods the MMS5000 was used for automatic sample supply. Equipped with a syringe, it can dose these liquids. In combination with a gripper the samples can be handled as if they were solids. The control of the analyser and analysis of results took place using the device software.


Raw material End product


Different Refi ned Fuels


The following table shows the results for different fuel samples. The high precision of the results also means that a reliable result is available after only a few repeat measurements. All Diesel samples were measured horizontally as liquid in this case, the other samples vertically.


Table 2: Sulphur content in different refi ned fuels Sample


Bio diesel A Bio diesel B


Bio diesel C Bio diesel D Bio ethanol A Bio ethanol B Bio ethanol C Diesel A Diesel B


Gasoline A Gasoline B


Figure 1: multi EA® 5000 by Analytik Jena


is generated, provided there is suffi cient oxygen supply. This compound acts SO3


) results entering the


TS ± SD [ppm] 2.430 ± 77.8 5.43 ± 0.07


TS ± SD [ppm] 2.98 ± 0.02 0.93 ± 0.01


0.86 ± 0.06 0.872 ± 0.02 0.73 ± 0.01 1.12 ± 0.02 0.70 ± 0.01 1.61 ± 0.03 1.64 ± 0.02 7.79 ± 0.11 5.82 ± 0.02


AUGUST / SEPTEMBER • WWW.PETRO-ONLINE.COM


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52