Tar analysis

There are interesting alternatives to the traditional tar analyses which are based on absorption in a solvent (impinger sampling trains). In this way, a quasi continuous tar quantification method has been developed at the University of Stuttgart [11]. It is based on the comparison of the total hydrocarbon content of the hot gas and that of the gas with all the tars removed. Hot gas from the gasifier is led directly to the analyser. Hydrocarbons are measured with a flame ionisation detector (FID). It considerably simplifies the experimental procedure compared to other methods described in literature. Sampling and analysis time is just two minutes. 

The comparison mentioned under 2. will result in knowledge on which method can reliably be used under which conditions. As other methods might be simpler (in terms of man-hours and equipment needed to perform the measurement) compared to the Guideline or produce online results on-site, we have named them shortcut methods . Examples of these methods are a) the solid phase adsorption (SPA) method developed by KTH (7], b) a number of solvent-free tar collection systems used by BTG, BEF, IGT [8-10] and c) the FID online tar analysing method under development at the University of Stuttgart (11,12]. Currently it is unknown under which conditions these methods give reliable results, for example it is unknown whether the SPA method can be used for updraft gasifier tars and at which conditions the solvent-free methods fail to collect ail tars, for instance as a result of aerosol formation. 

Harbin, B.A. and T.W. Stamey Automated data acquisition and processing of the FTC tar analyses 29th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 29, Paper No. 18,1975, p. 17, see www.ijrtdocs.com 510971828 -1828. 

The appHcation of modem methods of analyses such as gc, low ionization voltage mass spectrometry, high pressure Hquid chromatography (hplc), and nmr has greatly increased knowledge of coal-tar composition without materially altering the quaHtative picture. 

Tar. Before the development of gas chromatography (gc) and high pressure Hquid chromatography (hplc), the quantitative analyses of tar distillate oils involved tedious high efficiency fractionation and refractionation, followed by identification or estimation of individual components by ir or uv spectroscopy. In the 1990s, the main components of the distillate fractions of coal tars are deterrnined by gc and hplc (54). The analytical procedures included in the specifications for tar bulk products are given in the relevant Standardi2ation of Tar Products Tests Committee (STPTC) (33), ISO (55), and ASTM (35) standards. 

Mean tar concentrations on the Israeli coast of the Mediterranean Sea ranged from 884 to 4388 g m in 1975-76 (27). Chemical analyses indicated that 76% of the tar on Israeli beaches was weathered crude, 96% of it from Middle Eastern sources (28). Concentrations of tar on the beaches of Lebanon and Turkey appeared to be much lower than those at Alexandria, Egypt and Paphos, Cyprus, as a consequence of the orientation of these beaches relative to a site in the eastern Mediterranean Sea where dumping of oily sludge was permitted (27). 

Surface Analyses of Cobalt Catalysts for the Steam Reforming of Tar derived from Biomass Gasification... 

The surface analyses of the Co/MgO catalyst for the steam reforming of naphthalene as a model compound of biomass tar were performed by TEM-EDS and XPS measurements. From TEM-EDS analysis, it was found that Co was supported on MgO not as particles but covering its surface in the case of 12 wt.% Co/MgO calcined at 873 K followed by reduction. XPS analysis results showed the existence of cobalt oxide on reduced catalyst, indicating that the reduction of Co/MgO by H2 was incomplete. In the steam reforming of naphthalene, film-like carbon and pyrolytic carbon were found to be deposited on the surface of catalyst by means of TPO and TEM-EDS analyses. 

Figure 4.11 Mass spectrum of an archaeological sample made of a mixture of beeswax and birch bark tar from a residue sampled on a ceramic sherd from the Iron Age site of Grand Aunay (Sarthe, France). The spectrum was obtained by Dl El MS on a GCQ Finnigan device equipped with an ion trap analyser. Adapted from Regert and Rolando, 2002 (see colour Plate 1)...

Beck, C.W., Stout, E.C. and Janne, P.A. (1997). The pyrotechnology of pine tar and pitch inferred from qualitative analyses by GC-MS and carbon-13 NMR spectrometry. In Proceedings of the First International Symposium on Wood Tar and Pitch, Biskupin, Poland, ed. Brzezinski, W. and Piotrowski, W., State Archaeological Museum in Warsaw, Warsaw, pp. 181-192. 

Acknowledgments I thank Daniel A. Singleton for technical assistance, and Paul Donahue and Steven Dorn for NMR and MS spectral analyses. I also thank Reilly Tar and Chemical Co. for a generous sample of 4-(4-methylpiperidinyl)pyridine. 

Recently, Tor and co-workers have analysed the interaction between the cyclic analog 2 and the corresponding paromomycin derivative with the A-site sequence and also with the HIV TAR RNA fragment [47]. At pH 7.5, the decrease in affinity for the locked derivatives with respect to the parent aminoglycosides is 22-14 fold for the A-site and 11-2 fold for the HIV TAR sequence. The differences with respect to the natural ligands are significantly reduced at acid pH. 

The stractural and elemental analyses (contents of C, H and O) of biomass samples are given in Table 6.2. Table 6.3 shows the yields of products from three biomass samples by pyrolysis at different temperatures. As seen in Table 6.3, the pyrolysis process yields gaseous products, tarty hquid, and tar. In general, the yields of gaseous products from each run increase with increasing pyrolysis temperature. The yields of gaseous products from the pyrolysis increase from 34.4 to 43.9% for hazelnut shell, from 35.1 to 47.4% for tea waste and from 32.1 to 40.7% for spruce wood with increasing of temperature from 700 to 950 K. 

TG-FT-IR, Pyrolysis analyses were performed on the preliquefaction solids using thermogravimetric (TG) analysis with on-line analysis of the evolved products (including an infrared spectrum of the condensables) by FT-IR. The TG-FTIR method has been described previously (23-25). The Bomem TG/plus instrument was employed. A sample is continuously weighed while it is heated. A flow of helium sweeps the products into a multi-pass cell for FT-IR analysis. Quantitative analysis of up to 20 gas species is performed on line. Quantitation of the tar species is performed by comparison with the balance reading. 

Coal Derivatives. In attempting to extend this investigation to coal products, it was evident that not many isomeric analyses have been carried out. In the case of low temperature tar the predominant species reported have been normal olefins and normal alkanes. Branched alkane isomers are probably very low in concentration. However, limited data for high temperature coal tar (10) and for coal hydrogenation products (7, 12) indicate a close comparison of C7 alkanes with those from crude oil and the values predicted by the Fischer-Tropsch equation (Table III, top). A close comparison is notable also in the bottom part of Table III, which gives data for the Co and C7 naphthenes from high temperature coal carbonization, coal hydrogenation, and a crude oil. 

Liquids obtained from different petroleum reservoirs have widely different characteristics. Some are black, heavy, and thick, like tar, while others are brown or nearly clear with low viscosity and low specific gravity. However, nearly all naturally occurring petroleum liquids have elemental analyses within the limits given in Table 1-3. 

Wyoming subbituminous coal, whose analyses are given in Table II, was processed in both the PDU and a bench-scale reactor (BSR). The PDU is a 3 ton/day system while the BSR was designed for 3 lb/hr. The properties of tar produced in these two different systems under similar conditions were almost the same as shown in Table III. 

The tar used for this study was obtained from a series of BSR runs. The liquids were dissolved in acetone to filter off carried-over char fines. Acetone was stripped off in a one-plate distillation system. The analyses of this mixture of BSR tar are given in Table IV. The feed was stored at — 30°C, under a nitrogen blanket to minimize degradation. 

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