Slurry Phase Distillate process

Schaberg, P.W., et al., Diesel Exhaust Emissions Using Sasol Slurry Phase Distillate Process Fuels , SAE Paper 972898 presented at the International Fall Fuels Lubricants meeting Exposition,, 13-16 October, 1997, Tulsa, Oklahoma. 

Slurry bed reactors using heavy oil to support the catalyst have been tested and can operate over a wider range of operating conditions and feed gas compositions thm the fluid beds. Sasol has now developed an improved Sasol advanced Synthol (SAS) reactor to produce high-grade distillate. The Sasol slurry phase distillate process (SSDP) has been tested in a demonstration plant at Sasol 1 since 1993. The SAS reactor is said to use an iron-based catalyst similar to the one used in its original plants, whereas the SSDP process uses a cobalt catalyst. 

SPD [Slurry phase distillate] A process for making diesel fuel, kerosene, and naphtha from natural gas. Developed by Sasol and first commercialized in South Africa in 1993. A joint venture with Haldor Topsoe for the further development and commercialization of the process was announced in 1996. Commercialization in Nigeria was announced in 1998. 

SSPD [Sasol slurry phase distillate] A process for converting natural gas to diesel fuel, kerosene, and naphtha. Operated by Sasol in South Africa since 1993. Three stages are involved. In the first, natural gas is converted to synthesis gas by reforming. In the second, the synthesis gas is converted to waxy hydrocarbons in a slurry-phase reactor. In the third, the waxes are upgraded to middle distillates. See also Arge. 

The picture shows the Sasol Slurry Phase Distillate (SPD ) process plant, which converts at low temperatures synthesis gas to paraffins and specialty waxes. We express our gratitude to A. Buchanan and A. Rautenbach, both from Sasol, for kindly providing us with these figures. 

The FT process is well known and already applied on a large scale [9,10,11,12]. Currently, the two players that operate commercial Fischer-Tropsch plants are Shell and Sasol. In the Sasol and Shell plants gasification of coal and partial oxidation of natural gas, respectively, produce the syngas for the FT synthesis with well-defined compositions. Shell operates the SMDS (Shell Middle Distillate Synthesis) process in Bintulu, Malaysia, which produces heavy waxes with a cobalt catalyst in multi-tubular fixed bed reactors. Sasol in South Afirica uses iron catalysts and operates several types of reactors, of which the slurry bubble column reactor is the most versatile (i.e. applied in the Sasol Slurry Phase Distillate SSPD),... 

At present all the commercial Sasol FT units are operating with Fe-based catalysts, developed and manufactured in own facilities. The LTFT Cobased catalyst developed by Sasol Technology for the Sasol Slurry Phase Distillate (SPD ) process is being manufactured at a commercial plant in the Netherlands. 

Slurry-phase hydrocracking systems convert heavy vacuum residues however, these processes are not yet fully commercialized. The feed to this type of reactor is the petroleum residue plus a solid carrier (commonly known as additive). The purpose of the additive is to provide a surface for the deposition of converted asphaltenes and metals, as the residue is hydrocracked. Slurry reactors operate at high temperature and pressure, and residue conversions higher than 90% (Kressmann et al., 1998). Unfortunately, these units produce poor-quality, hydrogen-deficient distillate and vacuum products that cannot be used as fuel, unless blended with something else, for example, coal or heavy fuel oil, due to their high content of sulfur and metals (Ancheyta and Speight, 2007). 

Solids may be processed continuously or semicontinuously by pumping slurries or by using lock hoppers. An example is the separation of insoluble polymers by floatation with a variable-density SCF. For liquid feeds, multistage separation may be achieved by continuous counter-current extraction, much like conventional liquid-hquid extraction. The final produces may be recovered from the extract phase by a depressurization, a temperature change, or by conventional distillation. 

The continuous polycondensation process consists of four main process units, i.e. (1) slurry preparation vessel, (2) reaction unit, (3) vacuum system, and (4) distillation unit. The molar EG/TPA ratio is adjusted to an appropriate value between 1.05 and 1.15 in the slurry preparation vessel. In most industrial processes, the melt-phase reaction is performed in three up to six (or sometimes even more) continuous reactors in series. Commonly, one or two esterification... 

The MRH process is a hydrocracking process designed to upgrade heavy feedstocks containing large amount of metals and asphaltene, such as vacuum residua and bitumen, and to produce mainly middle distillates (Sue, 1989). The reactor is designed to maintain a mixed three-phase slurry of feedstock, fine powder catalyst and hydrogen, and to promote effective contact. 

The most advanced two-stage process involves close coupled operation with a disposable slurry catalyst (typically iron and/or molybdenum) added with the feed coal and an integrated hydrotreater to treat the distillate condensed from the gaseous phase from the... 

Evaporators are used to increase the concentration of relatively non-volatile dissolved or suspended components in a solution or slurry (the liquor) by evaporating portions of the liquid phase using energy supplied by a medium, often steam. The dissolved or suspended components do not appear in the vapor phase to a substantial extent. (If they do, the process is referred to as distillation.)... 

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