Sulphur removal

TSR(l) [Trace sulphur removal] A process for removing sulfur compounds from naphtha so that they will not poison catalytic reformers. A proprietary solid absorbent is used. Developed by the Union Oil Company of California and first commercialized in 1983 at the Unocal oil refinery in San Francisco. 

Tan [71] devised a rapid simple sample preparation technique for analysing polyaromatic hydrocarbons in sediments. Polyaromatic hydrocarbons are removed from the sediment by ultrasonic extraction and isolated by solvent partition and silica gel column chromatography. The sulphur removal step is combined into the ultrasonic extraction procedure. Identification of polyaromatic hydrocarbon is carried by gas chromatography alone and in conjunction with mass spectrometry. Quantitative determination is achieved by addition of known amounts of standard compounds using flame ionization and multiple ion detectors. 

The bed material normally consists initially of an inert material, such as sand or ash, of particle size between 500 and 1500 xm. This gradually becomes replaced by ash from the coal and additives used for sulphur removal. Ash is continuously removed from the bottom of the bed and, in addition, there is a considerable carry-over by elutriation and this flyash must be collected in cyclone separators. Bed depths are usually kept below about 0.6 m in order to limit power requirements. 

In reactions of this kind not only is the sulphur removed from the hydrocarbon but the hydrogen of the water (steam) becomes intimately involved in the overall process. Indeed the reaction is the combination of the thermal cracking shown in the fire flood example and the water gas reaction between the produced coke and steam. 

Another difference between Co and Fe is their sensitivity towards impurities in the gas feed, such as H2S. In this respect, Fe-based catalysts have been shown to be more sulfur-resistance than their Co-based counterparts. This is also the reason why for Co F-T catalysts it is recommended to use a sulphur-free gas feed. For this purpose, a zinc oxide bed is included prior to the fixed bed reactor in the Shell plant in Malaysia to guarantee effective sulphur removal. Co and Fe F-T catalysts also differ in their stability. For instance, Co-based F-T systems are known to be more resistant towards oxidation and more stable against deactivation by water, an important by-product of the FTS reaction (reaction (1)). Nevertheless, the oxidation of cobalt with the product water has been postulated to be a major cause for deactivation of supported cobalt catalysts. Although, the oxidation of bulk metallic cobalt is (under realistic F-T conditions) not feasible, small cobalt nanoparticles could be prone to such reoxidation processes. 

The dithioketal can be reduced directly to the hydrocarbon by hydrogenation over the sulphur-removing catalyst Raney nickel ... 

It should be remembered, however, that in this case, as in the charring of wood, in proportion as watery vapor traverses the incandescent mass, so a loss of the carbonaceous substance is sustained. This will be evident from, tbe above formula but the importance of having the sulphur removed from the coke, especially when destined to be used in the smelting of iron,... 

Structure-reactivity 21,581 Sulphur removal from terpenes201 Sulphated zirconia 479... 

Gas oil 100 000 tonnes Catalytic hydrogenation process for sulphur removal. 

The best way to remove sulphur compounds is to convert the organic sulphur species to H2S over a hydrodesulphurization catalyst. The next step is sulphur removal with an absorbent. The same catalyst can usually convert any organo-chloride species to give HC1 and also act as an absorbent for most problematic metal species. A second absorbent is used for chloride removal70. 

It is important that the sulphur removal absorbent be positioned downstream of the chloride absorbent. This is because HC1 reacts with active phases in the zinc oxide absorbent and irreversibly chemically binds the chloride into the absorbent. The resulting structural changes block the porous structure and reduce sulphur absorbent capacity. Since the HC1 absorbent has a very sharp absorption profile, frequently a layer of absorbent is placed on top of the sulphur absorbent within the same vessel. This design can help reduce capital costs70 (see Figure 5.9). 

A second important poison is AS2O3 but its poisoning effect is much less than that of sulphur [17], The mechanism of AS2O3-poisoning is based on the formation of an alloy with nickel. The arsenic typically originates from the solutions used in carbon dioxide wash of the catalyst or is present as an impurity in some zinc oxide sulphur removal beds. Also silica is mentioned as a pore mouth poison by physically blocking the entrance to the pore system by which the catalyst activity is decreased [18],... 

Of course, this reactive adsorption is favoured by removal of hydrogen from the reaction zone. When 80% of the hydrogen is removed in the membrane reactor, the H2S tolerance of the catalyst is about halve the tolerance when no hydrogen is removed from the reaction zone. A higher degree of sulphur removal from the feed stream should be accomplished when operating a membrane steam reformer. 

In the normal straight-through process, see Figure 1, the complete H2S stream is fed to a burner together with the amount of air required to bum one third of the H2S to SO2 to obtain the required gas mixture for the catalytic step of the process [2,5], The reaction temperature in this thermal step is about 1000-1400°C, and in this step 60 to 70% of the H2S in the gas is directly converted to elemental sulphur. The sulphur is condensed by cooling the gases first in a waste heat boiler, and after that in a sulphur condenser. After elemental sulphur removal the gas mixture is reheated to 250-300°C and fed to a catalytic converter. Three types of catalyst are currently used [5] ... 

Blicharz, M., Different Methods of Sulphur Removal from Gas from Non-ferrous Metal Works, paper read at Sulphur 88, Vienna, Austria, Nov. 6-9, 1988. 

Shimizu, T., Inagaki, M., and Furusawa, T. Effects of Sulphur Removal and Ammonia Injection on NO, Emission from a Circulating Fluidized Bed Combustor, in Circulating Fluidized Bed Technology III (Basu, P., Horio, M., and Hasatani, M., eds.), pp. 393-398. Pergamon Press, Oxford (1991). 

Aromatics reduction up to 10 vol. % is much more challenging than sulphur removal. If and when such a significant reduction is required a new reactor and separation system has to be added and integrated with the deep HDS unit. A proper sulphur resistant HDA catalyst such as Model 1-6 developed by ICERP can be used to attain a 10 % level of aromatics content in desulphurised blended feed up to 40 % CKGO with SRGO. 

One of the advantages of a TFBR is the ease with which the product separates from the catalyst the liquid waxes simply flow out of the catalyst bed. Also, if the reactor becomes contaminated with sulphur compounds, only the part of the catalyst bed closest to the reactant entrance will be de-activated, whereas with the SPR then, all the catalyst will be susceptible to poisoning. This disadvantage can be overcome by ensuring that sulphur removal processes for the syngas feedstock are wholly efficient. However, in contrast, there are a number of advantages of SPRs over TFBRs, which are as follows ... 

Biocatalysis/Genetic Engineering (Hydrogen-2 production, ethanol, Sulphur-removal)... 

Extracts from sediment, and sometimes also from soils, generally contain amounts of elemental sulphur, which, in addition to compromising the chromatographic separation, may damage the chromatographic column. The typical methods for sulphur removal are treatment with copper powder and/or mercury, " " which can be admixed directly to the sample during extraction or added to the extraction solution in a separate step. Copper powder is activated beforehand with HCl (18%) and washed with acetone and finally with -hexane. 

The mechanism of desulphurization of trisulphides by tris(dialkylamino)phos-phines is more complex than previously thought, e.g., the selectivity of central, rather than terminal, sulphur removal varies with the solvent polarity. Two reaction pathways are suggested to explain the results (Scheme 4). ... 

Fig. 12. Extraction and analysis of sterols from seawater. (1) At this stage, sulphur removal with an activated Cu-column may be necessary. The sample extracts may also be further purified by chromatography on silica gel (see Gagosian and Heinzer, 1979).

B. K. Tubbs and J. L., Smialek, Effect of sulphur removal on scale adhesion to PWA 1480. In Corrosion and Particle Erosion at High Temperatures, eds. 

The net effect of the oxygen and sulphur removal from the Na2S04 deposit on nickel oxidized in air is to increase the oxide-ion concentration, or the activity of Na20 in the Na2S04 as indicated in the equivalent reactions, shown in Equations (8.12) and (8.13),... 

In the early days of atmosphere control, town gas was used for the preparation of atmospheres however, being derived from coal, this inevitably involved the need for a plant for sulphur removal, and variation in analysis made consistent control of the atmosphere composition difficult. 

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