Sulfur removal, from fuel

Zhang, S., Zhang, Z.C., Novel properties of ionic liquids in selective sulfur removal from fuels at room temperature. Green Chem., 4, 376-379, 2002. 

MacFarland, B.L. Boron, D.J. Deever, W. Meyer, J.A. Johnson, A.R. Atlas, R.M. Biocata-lytic sulfur removal from fuels applicability for producing low sulfur gasoline. Crit. Rev. Microbiol. 1998, 24 (2), 99-147. 

Biodesulfurization is a process that removes sulfur from fossil fuels using a series of enzyme-catalyzed reactions.Biodesulfurization is another alternative processing method that has some similarity to the above-mentioned oxidative desulfurization, in that both methods oxidize sulfur atoms in the sulfur-containing compounds. Certain microbial biocatalysts have been identified that can biotransform sulfur compounds found in fuels, including ones that selectively remove sulfur from dibenzothiophene-type heterocyclic compounds. " Biocatalytic sulfur removal from fuels may have applicability for producing low sulfur gasoline and diesel fuels. 

The plant is designed to satisfy NSPS requirements. NO emission control is obtained by fuel-rich combustion in the MHD burner and final oxidation of the gas by secondary combustion in the bottoming heat recovery plant. Sulfur removal from MHD combustion gases is combined with seed recovery and necessary processing of recovered seed before recycling. 

Future legislation will stimulate burner development in the areas of carbon monoxide, NOx and particulate generation. Techniques will include flue-gas recirculation, staged combustion, and additives to reduce the NOx and more sophisticated controls. Controls over the sulfur generated do not affect burner design greatly since the sulfur dioxide is a natural product of combustion and can only be reduced by lower fuel sulfur contents or sulfur removal from the exhaust gases. 

Atlantic Richfield Company, Arco has developed several conventional technologies for sulfur removal from coal and ashes and for manufacturing oil-coal mixed fuels, prior to becoming involved in BDS. Their patent entitled, Biodesulfurization of carbonaceous materials [16] was developed for the coal application, but nevertheless was extrapolated for application to petroleum desulfurization as well. 

Solutizer Also spelled Solutiser. An early process for removing sulfur compounds from fuel oil by solvent extraction with alkaline sodium isobutyrate. Developed by Shell Development Company. 

In the context of the desirability of removing sulfur compounds from fuels, a bacterial strain has been identified that will metabolize thianthrene to water-soluble products under aerobic conditions (83MI5). A thermophilic organism, Sulfolobus acidocaldarius, removed 38% of the sulfur, as measured by sulfate release, in 4 weeks at 70°C (87MI2). 

The replacement of conventional catalytic processes for purification of mixtures by processes involving extraction with ionic liquids has also been envisioned. For example, the extractive removal of sulfur compounds from fuels has shown promising leads for high selectivity for aromatic sulfur compounds, and removal of such compounds has been a major challenge in conventional heterogeneous hydrodesulfurization catalysis (27,296). 

Much of the sulfur contained in a crude oil remains with the tar, asphalt or coke after refining. As crude prices rise, even this residuum becomes valuable as a feedstock for cracking to make lighter products. This involves deep desulfurization. Whether the coke is burned as a fuel or used for anodes, desulfurization will take place before or after combustion or processing. Sulfur removal from coke plants is a currently feasible process. 

It is also doubtful that the industry will be in a position for many years to come to undertake sulfur removal from residual fuels solely to improve product quality. A number of consumer industries demand low sulfur fuel oils, but these special requirements can at present be met more appropriately by selection of crude rather than by adoption of desulfurization processes. In general industrial use, it is corrosion and atmospheric pollution that are the main disadvantages of high sulfur content. But there is no sign yet of the development of a cheap desulfurization process, the cost of which can be substantially offset by the gain in efficiency resulting from permissible lower stack temperatures or by the elimination of flue gas scrubbing equipment previously necessary for reduction of sulfur dioxide content. 

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Removal of sulfur compounds from fuel oils is usually accomplished at the refinery. Although most of the sulfur in oil is in the high boiling fraction, some middle distillates have high sulfur contents. A better understanding of the chemistry of sulfur compounds in oil will also facilitate their efficient removal. 

Eckart and co-workers have published a series of papers on laboratory studies of biodesulfurization of petroleum and petroleum fractions. The ability of various aerobic mixed cultures to desulfurize Romashkino crude oil (1.69 wt.% S) was addressed by Eckart et al. (21). After 5 days of incubation at 30°C in sulfur-free mineral medium with oil as sole source of carbon and sulfur, approximately 55% of the total sulfur was recovered in the aqueous phase from two of the most active cultures. In another study, gas oil (1.2 to 2 wt.% S), vacuum distillates (1.8 to 2 wt.% S) and fuel oil (up to 4 wt.% S) were used as sole carbon and sulfur sources for the oil-degrading microorganisms (36). The addition of an emulsifying agent was required to enhance desulfurization. Sulfur removals of up to 20% from the gas oil, 5% from the vacuum distillates, and 25% from the fuel oil were observed after 5 to 7 days of incubation. In a later study (37). approximately 30% of the sulfur was removed from fuel-D-oil by a mixed population of bacteria. The removal of benzothiophene, dibenzothiophene and naphthobenzothiophene was shown by high resolution MS analysis. Hydrocarbon degradation was observed in each of these studies. For example, in the latter study with fuel-D-oil, the decreases in the n-alkane and aromatic content were 59% and 14%, respectively. 

Precombustion control involves removal of sulfur compounds from fuel prior to combustion. Control during combustion employs techniques to minimize the formation and/or release of SO2 and N0X during the combustion process. Finally, SO2 and N0X can be removed from the combustion flue gas using various postcombustion control methods. This chapter discusses the potential of mitigating acid deposition through precombustion cleaning of coal to remove sulfur compounds. 

Finnerty, W.R., Symposium on Microbial Processes for Metals Accumulation and Sulfur/Nitrogen Removal from Fuels. American Chemical Society, Las Vegas, Nevada, August 1980. 

Olsen, C., Krenzke, L.D., and Watkins, B. Sulfur removal from diesel fuel optimizing HDS activity through the SMART catalyst system. Proceedings of the Fifth International Conference on Refinery Processing, AIChE Spring National Meeting. New Orleans, LA, 2002. 

Watanabe, S., Ma, X.L., and Song, C.S. Selective sulfur removal from liquid hydrocarbons over regenerable Ce02-Ti02 adsorbents for fuel cell applications. Preprints of Papers—American Chemical Society, Division of Fuel Chemistry, 2004, 49, 511. 

Scheme 2 Basic principle of the S Zorb Sulfur Removal Technology process developed by Phillips Petroleum for sulfur removal from liquid fuel at elevated temperatures under low H2 pressure.

A number of hydrocarbon separations have been intensely studied and piloted in recent years and commercialization is expected soon. Pervaporation is expected to be one of a number of proven options for sulfur and benzene removal from fuels and olefin/ paraffin separations. These plants will use robust, specially engineered polymer membranes, installed in large-scale tubular modules. 

J. D. Carter, T. Krause, J. Mawdsley, R. Kumar, and Michael Krumpelt, Sulfur Removal from Reformate, presented at the DOE Fuel Cells for Transportation National Eaboratory R D Meeting, June 6-8, 2001, Oak Ridge, TN. 

FDP fluid-bed reactor system, the sulfur removal from the Pittsburgh Seam coal has been about 85%. These results are encouraging because they indicate that char from the Hydrane reactor may be an acceptable fuel to provide the plant s energy and steam requirements without complicated sulfur removal systems and without exceeding air quality restrictions on atmospheric release of sulfur compounds. 

One method of sulfur removal from refinery streams is by hydrodesulfurization (HDS) in the refineries. This step also directly impacts the characteristics of low sulfur diesel fuels, such as density, aromatics content, cetane number, and cloud point. The magnitude of these changes will depend upon the type and setup of refinery HDS units. However, in the end some refractory compounds in fuel, e.g., 4,6-diraethyl dibenzothiophene, are very resistant to desulfurization, owing to the inaccessibility of the organically bound sulfur atom. Lower pressure HDS units which can work satisfactorily at 350 rag/kg sulfur levels, may have difficulty achieving reduction to 50 or 10 rag/kg sulfur level. 

Lin L., Zhang Y., Kong Y. 2009. Recent advances in sulfur removal from gasoline by pervaporation. Fuel 88 1799-1809. 

Joshi, J.B. and Y.T. Shah. Kinetics of Organic Sulfur Removal from Coal by Oxydesulfurization. Fuel (in press). 

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