Fischer-Tropsch refining

Energy carriers, such as coal, natural gas and biomass, can be converted by Fischer-Tropsch technology into synthetic crude (syncrude). Fischer-Tropsch derived syncrude can then be refined to transportation fuels, such as motor-gasoline, jet fuel and diesel fuel. These fuels meet the same specifications as crude oil derived transportation fuels. Conventional refining technologies have to be adapted to deal with Fischer-Tropsch syncrudes, because they differ significantly from crude oil with respect to composition. Some of the key differences are the high concentration of oxygenates and olefins and absence of sulphur in Fischer-Tropsch syncrude. Imposing a crude oil refining methodology on syncrude can lead to unwieldy and expensive refineries. Yet, despite an abundance of literature of Fischer-Tropsch synthesis, there is little literature that deals with the refining of Fischer-Tropsch syncrude. The present study investigated current refining practice for both crude oil and Fischer-Tropsch syncrude in order to identify fundamental differences in their refining focus and conversion behaviour. This was followed by a critical evaluation of the compatibility of syncrudes from high temperature Fischer-Tropsch (HTFT) and low temperature Fischer-Tropsch (LTFT) synthesis with the chemistry and catalysis of various conversion processes. The conversion processes that were evaluated include isomerisation, oligomerisation, etherification, alkylation, metathesis, hydrogenation, hydroisomerisation, hydrocracking, catalytic cracking, coking, thermal cracking, catalytic reforming and dehydration. The recommendations from the technology evaluation provided the foundation for the development of Fischer-Tropsch syncrude based refinery designs. Refinery designs were developed to determine configurations that would maximise the production of on-specification motor-gasoline, jet fuel and diesel fuel respectively. It could be shown that less complex refinery designs were required to refine Fischer-Tropsch syncrude to motor-gasoline and jet fuel, than were required for crude oil refining. It was also shown that on a molecular level Fischer-Tropsch syncrude is unsuited for maximising the production of Euro-4 type diesel fuel. The present study illustrates the advantage of considering fundamentals in developing refineries specifically for Fischer-Tropsch syncrude, rather than imposing crude oil design practises on Fischer-Tropsch syncrude refinery designs.Thesis (PhD (Chemical Engineering))--University of Pretoria, 2008.Chemical Engineeringunrestricte

Responses of selected biota after biostimulation of a vegetable oil spill in the Con Joubert Bird Sanctuary wetland: A pilot study

An investigation on the effect of a vegetable oil spill was conducted on the biological diversity of the Con Joubert Bird Sanctuary wetland in South Africa before and after biostimulation with different concentrations of fertilizer during 2008. Biostimulation responses were analyzed 30 days after different concentrations of fertilizer were applied to the freshwater wetland at three selected sampling sites. The Con Joubert Bird Sanctuary wetland showed a high degree of contamination after a vegetable oil spill, resulting in a large volume of vegetable oil in the sediment and water column, respectively. Vegetable oil contents differed at each sampling site before biostimulation and each site showed variable responses after biostimulation. In this study, biostimulation results displayed a high yield of microbial activity and vegetable oil degradation at site one and two respectively. However, the degradation of the high vegetable oil concentrations within the sediments at sampling site 3 may have been hampered or retarded by the polymerized state of the vegetable oil. The phytoplankton, protozoan, macroinvertebrates and microorganisms assemblage were affected and showed little improvement at site 3, even after biostimulation with the high fertilizer concentration of 800 g/m2, in comparison to sites 1 and 2 which showed greater biological activities and degradation of vegetable oil.Keywords: Biostimulation, vegetable oil spill, fresh water wetlandAfrican Journal of Biotechnology Vol. 12(4), pp. 385-39

Zeolites as Catalysts for Fuels Refining after Indirect Liquefaction Processes

The use of zeolite catalysts for the refining of products from methanol synthesis and Fisher–Tropsch synthesis was reviewed. The focus was on fuels refining processes and differences in the application to indirect liquefaction products was compared to petroleum, which is often a case of managing different molecules. Processes covered were skeletal isomerisation of n-butenes, hydroisomerisation of n-butane, aliphatic alkylation, alkene oligomerisation, methanol to hydrocarbons, ethanol and heavier alcohols to hydrocarbons, carbonyls to hydrocarbons, etherification of alkenes with alcohols, light naphtha hydroisomerisation, catalytic naphtha reforming, hydroisomerisation of distillate, hydrocracking and fluid catalytic cracking. The zeolite types that are already industrially used were pointed out, as well as zeolite types that have future promise for specific conversion processes

An assessment of the ecological integrity of Reed Pans on the Mpumalanga Highveld

M.Sc.Mpumalanga, “the place where the sun rises”, sets the scene for one of the rarest wetland types in South Africa. They are formed on one of the last remnants of the ancient African land surface, contain peat and together with a variety of other pan types make up the Mpumalanga Lakes District. Of these approximately 320 pans, only ±2.3% are reed pans. These endorheic wetlands are unique from other pan types and peatlands in South Africa and support an abundant biodiversity. They perform vital functions such as water storage, filtering out impurities and carbon fixation, which prevents an excess release of CO2 into the atmosphere. There is very little known about these endorheic wetlands and thus they are constantly being threatened by various activities such as agriculture, livestock and mining. The objectives of this study were to determine the spatial and temporal variation of macroinvertebrate community structures of reed pans and the environmental factors, such as water quality, responsible for the maintenance of these structures; to determine the best method for sampling aquatic invertebrates in reed pans; as well as to determine the relationship between aquatic invertebrates and the water, sediment and habitat quality of a reed pan. Together with this the amphibian diversity as well as the occurrence of other biotic components was determined. Four reed pans were assessed during four different seasons over a one year period to account for the different hydrological extremes. Sub-surface water samples were analyzed for their suspended solid content, nutrient levels, metals and chlorophyll-a concentrations as well as in situ water quality parameters. Sediment samples were analyzed for metal concentrations, organic carbon and water content, as well as sediment size distribution. Invertebrates were collected using the following sampling techniques: aquatic light trap, terrestrial light trap, emergent trap, sweep net, plankton net, as well as benthic sampling using an Eckman grab

A comparative exotoxicological study of two major South African river systems : a catchment scale approach for improved risk assessment and environmental management through the integration of abiotic, biotic, biochemical and molecular endpoints

Thesis (PhD)--Stellenbosch University, 2016.ENGLISH ABSTRACT: Along with the prosperity of humankind, the inevitable increase in developments to support this often results in water resources becoming repositories for the waste generated by such progress. To ensure sustainable development, anthropogenic impacts need to be properly assessed and anticipated in order to respond accordingly to mitigate such events. With the Mokolo River being at the center of plans to exploit the largest remaining coalfield in South Africa, this study was initiated to improve our understanding of the range of expected water resource impacts that may occur, by taking lessons learned from the upper Olifants River system, which has been severely impacted by coal mining for more than a century. The aim of this study was to conduct a comparative ecotoxicological study at a catchment scale on both the Mokolo River and upper Olifants River systems. Study sites in the upper Olifants and Mokolo rivers, their major tributaries, as well as major impoundments were selected and assessed seasonally for a number of years. Water and sediment samples were analyzed for various constituents, whilst biological samples (invertebrates and fish) were also sampled to gain perspectives on the impact of pollution at molecular, cellular and community levels. Lastly, a case study to examine the potential use of rehabilitation measures on ecological infrastructure to mitigate the potential impact of acid mine drainage (associated with coal mining activities) was conducted. Important abiotic ecosystem drivers were identified, whilst the influence of the tributaries and impoundments on the main stream rivers were determined. The major exposure routes of bioaccumulation were found to be through the dietary uptake of contaminated sediment and algae. The use of the fresh water crab, Potamonautes warreni, provided an excellent model organism to study the fate, transport and impact of pollution and also to monitor various degrees of molecular and cellular impacts. In contrast to the general use of fish as bioindicators, the use of aquatic invertebrate community structures and freshwater crabs proved more useful to characterize the ecosystem integrity of these systems, detect turnover and determine the links with possible contaminants. From the various biochemical and molecular markers used, several endpoints proved useful in monitoring chronic impacts on biota, which may be used as early warning indicators, whilst others are linked to acute anthropogenic impacts. A significant improvement in water quality occurred after the wetland rehabilitation case study, including increased productivity, reduced toxicity (embryotoxicity and teratogenicity) and changes in the biotic community structures. Therefore, the benefit of the rehabilitation of ecological infrastructure to mitigate the impact of coal mining associated pollution was proven. Overall, the use of a comparative catchment approach, employing both an impacted and less impacted river system, proved extremely useful and valuable to support the future management of the Mokolo River in the face of ever increasing land use activities. This catchment scale comparative study is a rare and unique opportunity which few studies are able to utilize to assess the likely impacts of future land use change.AFRIKAANS OPSOMMING: Tesame met die welvaart van die mensdom, veroorsaak die onvermydelike styging in ontwikkelings om dit te ondersteun dikwels dat waterbronne bewaarplekke word vir afval wat gegenereer word tydens die vordering. Ten einde volhoubare ontwikkeling te verseker, is dit nodig om antropogeniese invloede behoorlik te evalueer en te verwag om sodoende dienooreenkomstig te reageer op sulke gebeurtenisse, sodat die impak verminder kan word. Met die Mokolorivier wat te midde is van planne om die grootste oorblywende steenkoolveld in Suid-Afrika te ontgin, is hierdie studie geïnisieer om ons begrip van die omvang van die verwagte waterbron impakte wat mag voorkom, te verbeter deur te leer uit vorige ervarings in die boonste Olifantsrivier, wat erg geraak is deur steenkoolmynbou vir meer as 'n eeu. Die doel van hierdie studie was om 'n vergelykende ekotoksikologiese studie te doen op 'n opvangsgebied skaal op beide die Mokolo- en boonste Olifantsriviere. Studie areas in die boonste Olifants- en Mokoloriviere, hulle hoof sytakke en damme is gekies en seisoenaal geassesseer vir 'n aantal jare. Water en sediment monsters is ontleed vir verskillende parameters, terwyl biologiese monsters (invertebrata en visse) ook versamel is om die uitwerking van besoedeling te bepaal op 'n molekulêre, sellulêre en gemeenskapsvlak. Laastens was 'n gevallestudie gedoen om die potensiële gebruik van rehabilitasie van ekologiese infrastruktuur om die impak van suur mynwater (geassosieer met steenkoolmyn aktiwiteite) te verminder, ondersoek. Belangrike abiotiese ekosisteem drywers is geïdentifiseer, terwyl die invloed van die sytakke en damme op die hoofstroom riviere bepaal was. Die grootste blootstellingsroetes van bioakkumulering is gevind om deur die opname van gekontamineerde sediment en alge te wees. Die gebruik van die varswater krap, Potamonautes warreni, is 'n uitstekende modelorganisme om die lot, vervoer en impak van besoedeling te bestudeer, asook om verskillende grade van molekulêre en sellulêre impakte te monitor. In kontras met die algemene gebruik van visse as bio-indikators het die gebruik van akwatiese invertebraat gemeenskapstrukture en varswater krappe bewys dat dit meer bruikbaar is om ekosisteem integriteit te beskryf, omsette te bepaal, asook die verbintenisse met moontlike besoedeling te bepaal. Vanuit die verskillende biochemiese en molekulêre biomerkers wat gebruik is, het verskeie eindpunte bewys om nuttig te wees in die monitering van kroniese impakte op biota, wat gebruik kan word as vroeë waarskuwingsindikators, terwyl ander gekoppel is aan akute antropogeniese impakte. Daar was 'n beduidende verbetering in die waterkwaliteit na die rehabilitasieproses van die vleiland, insluitend 'n toename in produktiwiteit, verminderde toksisiteit (embriotoksisiteit en teratogenisiteit) en verandering in die biotiese gemeenskapstrukture. Hierdeur was die nuttigheid van die rehabilitasie van ekologiese infrastruktuur om die impak van steenkoolmyn geassosieerde besoedeling te verminder, bewys. Dus, die gebruik van 'n vergelykende opvangsgebied benadering, deur die gebruik van beide 'n besoedelde en onbesoedelde rivierstelsel, is baie nuttig om die toekomstige bestuur van die Mokolorivier te ondersteun in die aangesig van toenemende antropogeniese aktiwiteite. Hierdie vergelykende studie op opvangsgebied skaal is 'n seldsame en unieke geleentheid wat min studies in staat is om aan te wend om die waarskynlike impak van veranderings in toekomstige grondgebruik te evalueer.Doctora

Can Fischer−Tropsch Syncrude Be Refined to On-Specification Diesel Fuel?

The interchangeable colloquial use of the terms “distillate” (boiling range) and “diesel fuel” (distillate meeting legislated fuel specifications), led to misleading perceptions about the suitability of Fischer−Tropsch syncrude for diesel fuel production. Two questions are addressed: Can Fischer−Tropsch syncrude be refined to diesel fuel, and which Fischer−Tropsch technology is best for maximizing distillate and ultimately diesel fuel production? The distillate yield that can be obtained from Fischer−Tropsch syncrude in an uncomplicated refinery employing only hydrocracking and/or oligomerization follows the order: Fe-LTFT > Co-LTFT > Fe-HTFT. Conversely, producing diesel fuel (not distillate) from Fe-HTFT syncrude is easier. On a molecular level, Fischer−Tropsch syncrude was found to be unsuitable for the production of EN 590:2004 diesel fuel in high yield. There is a trade-off between distillate density, cetane number, and yield, which is called the Fischer−Tropsch density−cetane−yield triangle. It is possible to meet any two of these three requirements without too much refining effort, but meeting all three with Fischer−Tropsch syncrude as feed material, is difficult. Strategies have been suggested to overcome the Fischer−Tropsch density−cetane−yield triangle and to improve the yield of on-specification diesel fuel. Some industrial implications for the standalone Fischer−Tropsch-based production of diesel fuel are discussed. High-temperature Fischer−Tropsch (HTFT) and low-temperature Fischer−Tropsch (LTFT) fuels refinery designs based on current refining technology to maximize EN 590:2004 diesel fuel are provided