The emission of sulphur oxides during the combustion of coal is one of the causes of an environmental problem known as acid rain. Biodesulphurisation technology applied as a method to remove sulphur before coal combustion was investigated in this work. The desulphurisation abilities of three specific bacterial strains including Rhodococcus erythropolis IGTS8, R. erythropolis X309 and Shewanella putrefaciens strain NCIMB 8768 have been evaluated. R. erythropolis IGTS8 and X309 were found to be able to remove both inorganic and organic sulphur from model compounds and coal samples. Their abilities to remove sulphur from benzothiophene were observed for the first time. A novel desulphurising bacterium, S. putrefaciens was also found to be able to remove inorganic and organic sulphur from coal samples. The bacterium, however, lost its ability to remove organic sulphur from model compounds during the investigation. R. erythropolis IGTS8 presented the greatest desulphurisation efficiency among the three bacterial strains. Nevertheless, the desulphurisation activity of R. erythropolis IGTS8 was too low for an economical coal biodesulphurisation process as it removed only 32.0% of total sulphur in bituminous coal, and 21.1% of total sulphur in anthracite coal. Alternatively, coal biodesulphurisation can be carried out in inexpensive conditions by using the bacteria inherent in the coal itself. The type of coal has an important effect on desulphurisation efficiency since the sulphur reduction in bituminous coal, which is in a lower rank than anthracite, was greater than the sulphur reduction in anthracite coal. This work also developed and evaluated the analytical methods used in the field. A HPLC method was developed to detect the desulphurisation metabolites of model compounds. The techniques for measuring sulphur in coal were improved.

No description available.

No description available.

<p> </p><p>In order to optimise the ladle treatment mass transfer modelling of aluminium addition and homogenisation time was carried out. It was stressed that incorporating slag-metal reactions into the mass transfer modelling strongly would enhance the reliability and amount of information to be analyzed from the CFD calculations.</p><p> </p><p>In the present work, a thermodynamic model taking all the involved slag metal reactions into consideration was incorporated into a 2-D fluid flow model of an argon stirred ladle. Both thermodynamic constraints and mass balance were considered. The activities of the oxide components in the slag phase were described using the thermodynamic model by Björkvall and the liquid metal using the dilute solution model. Desulphurization was simulated using the sulphide capacity model developed by KTH group. A 2-D fluid flow model considering the slag, steel and argon phases was adopted.</p><p> </p><p>The model predictions were compared with industrial data and the agreement was found quite satisfactory. The promising model calculation would encourage new CFD simulation of 3-D along this direction.</p><p> </p>

Sulphur dioxide (S02) is an atmospheric pollutant that has the ability to negatively impact on local vegetation, farming activities and human health. South Africa's coal fired power stations release this pollutant into the atmosphere during the combustion of coal. Current coal fired power stations operating in South Africa are not required to install any form of S02 removal equipment however, the new Air Quality Act to be implemented in South Africa could change this situation. The use of Fluidised Bed Technology with the addition of limestone or dolomite (sorbent) has the ability to absorb and convert S02 from a gaseous phase into a solid phase for easy disposal. The objective of this study was to evaluate potential commercial sorbent sources in South Africa that could potentially be used for the reduction of S02 released into the atmosphere during fluidised bed combustion of coal. Eight commercially mined sorbents within a two hundred kilometre radius of large economically mineable coalfields were selected. The study was divided into two parts in order to identify any possible links between the physical and chemical composition of the sorbents and their performance under fluidised bed combustion conditions. In Part 1, the chemical composition of the sorbents was determined by X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) analysis. The sorbents hardness property was determined by Hardgrove Grindability Index (HGI) testing. The physical structure of the sorbent was analysed by both Petrographical and Scanning Electron Microscope (SEM) analysis of the original/parent sorbents. In Part 2, S02 absorption capability by the sorbents was determined through batch tests conducted in a 1.6m high stainless steel, 10kW electrically heated Atmospheric Fluidised Bed Reactor (AFBR). Three different bed temperatures (800, 850 and 900°C) and three different particle size ranges (425-500, 600-710 and 850-lOOOllm) were tested for each of the eight sorbents. The highest Maximum Sulphur Retention for all of the sorbents was found to occur at a temperature of 850°C and at the smallest particle size tested, 425-500llm. The best desulphurisation sorbent of the eight sorbents tested was found to be Sorb1 with a S02 Maximum Sulphur Retention of 92.30% and a Removal Efficiency of 84.54%. Additional tests were also performed on the sorbents to get a better understanding of their desulphurisation ability. For the area calculation on the performance test graphs, it was found that the sorbent that produced the best S02 removal efficiency was not necessarily the sorbent that had the highest maximum sulphur retention. For varying quantities of sorbent added to the AFBR, it was found that each sorbent had an optimum quantity that produced the best removal efficiency. However, for desulphurisation beyond certain limits any further increase in the amount of sorbent added to the AFBR resulted only in a marginal increase in the sorbent's S02 removal. The calcium and magnesium composition of the sorbents was found to have no noticeable influence on the sorbents ability to reduce S02. The silica and inherent moisture content of the sorbent showed signs whereby an increase in their compositions produced an increase in desulphurisation. The Hardgrove Grindability Index of the sorbents indicated that the softer the sorbent, the better the S02 reduction. The petrographical analysis performed on the eight sorbents showed no obvious reason for the difference between the sorbents ability to remove S02. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.

<p> An experimental evaluation of three desulphurisers for pig iron has been conducted. Sodium vapor, blast furnace slag enriched with cerium oxide and a rare earth alloy named misch metal have been used. </p> / Thesis / Master of Engineering (MEngr)

<p> A levitation apparatus has been constructed for investigating the behaviour of liquid iron drops containing sulphur, whilst suspended in a moving gas stream.</p> <p> To further this investigation, a source of iron-sulphur alloys, in form and size suitable for levitation, was required. Four methods for the preparation of the desired alloys were suggested, and each was experimentally examined in sequence.</p> <p> The first 2 methods involved the quenching of a liquid solution of sulphur in iron, to give a solid alloy. The well-known behaviour of sulphur, to segregate on solidification, was observed, and the non-uniformity of the resulting alloys could not be tolerated. The third method involved preparing a large number of individual iron-sulphur samples by allowing drops of iron to fall and quench on particles of sulphur or iron sulphide. The repeatability of the method was found to be unsatisfactory. In the final attempt a levitated liquid drop of iron was equilibrated in a gas mixture of hydrogen-hydrogen sulphide. This method was considered more successful than the earlier three, and has the advantage that the prepared alloy drop is levitated and at the desired temperature.</p> / Thesis / Master of Engineering (MEngr)

Flue gas desulphurisation (FGD) is a crucial method to minimise the SO2 emissions from industrial processes. The FGD system utilise an alkaline sorbent to remove SO2 from the flue gases. Calcium in form of limestone is a commonly used sorbent where gypsum is produced asa by-product. However, the limestone reactivity, along with impurities within the sorbent, can significantly influence the effectiveness of SO2 removal and the quality of the by-products. At Heidelberg materials Cement Sverige an intermediate product, raw meal (RM) 8, is used assorbent in the FGD and gypsum is used as setting retarder in the cement. The aim with this project is to examine if raw meal 7 or A-sten is a better sorbent than raw meal 8 with respect to consumption rate, gypsum quality and its effect on the cement properties, and economic viability. To accomplish this a theoretical study was performed along with data analysis. RM 7 and A-sten are both purer than RM 8 but the raw material cost for RM 7 is about 1.24 times the raw material cost for RM 8 and the production costs and transportation costs are greater for RM 7 than for RM 8. The raw material cost for A-sten is about 0.45 times the cost for RM 8 but is not produced on site. All sorbents contain magnesium which can react with sulphur and precipitate as epsomite or hexahydrite, which also acts as retarders, where epsomite retard the cement setting time significantly compared to gypsum. To calculate the consumption rate of raw meal and A-sten into the scrubber three different methods were used. The difference between the methods lies in the consideration of how the calcium and magnesium species in the sorbent react with sulphur, with all calcium and magnesium reacting with sulphur in method 1, method 2 take the mass fraction of sulphurcontaining species into consideration, and method 3 incorporating mole fractions of calcium and magnesium species as well as sulphur from the sorbent. The pH and SO2 emissions were analysed for two different time periods where the first analysed period shows a correlation between low pH and high SO2 emissions, while the latter analysed period lacks a clear pH-SO2 correlation. A correlation between a lower pH and a lower percentage of MgSO4⸱6H2O and MgSO4⸱7H2O in the slurry could be made. The calculated rawmeal flow rate for RM 8 is between 520 and 554 kg/h, depending on the method used. To achieve the same desulphurisation efficiency with RM 7 the flow was calculated to 499-538kg/h and 427-464 kg/h for A-sten. Given the comparable mass flow rates of RM 8 and RM 7 it is advisable to retain RM 8 as asorbent in the scrubber regardless of the higher magnesium content due the higher cost associated with RM 7. However, the epsomite content in the slurry should be considered when optimising sulphur in cement production. Using A-sten as sorbent would minimise the rawmaterial costs and result in purer gypsum slurry with a lower epsomite content. Operating with a purer sorbent can also enhance the efficiency of the FGD process, leading to lower SO2 emissions. The calculations in the report assume that calcium and magnesium in the different sorbents react similarly, further analysis of their reactivity is recommended for more accurate results. / Rökgasavsvavling är en avgörande metod för att minimera SO2-utsläppen från industriella processer. Rökgasavsvaling använder en alkalisk sorbent för att avlägsna SO2 från rökgaserna. Kalcium i form av kalksten är en vanligt förekommande sorbent där gips produceras som en biprodukt. Kalkstensreaktiviteten, tillsammans med föroreningar i sorbenten kan emellertid avsevärt påverka avsvavlingseffektiviteten och biproduktens kvalitet. På Heidelberg materials Cement Sverige används en mellanprodukt, råmjöl (RM) 8, somsorbent i avsvavlingsprocessen och gipset används som härdningshämmare i cementet. Syftet med detta projekt är att undersöka om råmjöl 7 eller A-sten är en bättre sorbent än råmjöl 8 med avseende på konsumtionshastighet, gipskvalitet och dess effekt på cementens egenskapersamt ekonomisk bärkraft. För att uppnå syftet genomfördes en teoretisk studie tillsammans med dataanalys. RM 7 och A-sten är båda renare än RM 8 men råvarukostnaden för RM 7 är cirka 1,24 gånger råvarukostnaden för RM8. Dessutom är produktions- och transportkostnaderna högre för RM7 än för RM 8. Råvarukostnaden för A-sten är cirka 0,45 gånger råvarukostnaden för RM 8, dock mals inte A-sten på plats. Alla sorbenter innehåller magnesium som kan reagera med svavel och fälla ut som epsomit eller hexahydrit, vilka också har en härdningshämmande effekt, där epsomit fördröjer cementens härdning signifikant jämfört med gips. För att beräkna konsumtionshastigheten för råmjöl och A-sten i skrubbern användes tre olika metoder. Skillnaden mellan metoderna är hur kalcium- och magnesiumarterna i sorbenten reagerar med svavel, där allt kalcium och magnesium reagerar med svavel i metod 1. Metod 2 tar hänsyn till massfraktionen av svavelhaltiga ämnen och metod 3 innehåller molfraktioner av kalcium- och magnesiumarter samt svavel från sorbenten. pH och SO2-utsläppen analyserades under två olika tidsperioder där den första perioden visar ett samband mellan lågt pH och höga SO2-utsläpp, medan den senare analyserade perioden saknar ett tydligt pH-SO2-samband. En korrelation mellan ett lägre pH och en lägre andel MgSO4⸱6H2O och MgSO4⸱7H2O i gipsslurryn skulle kunna göras. Det beräknade flödet av råmjöl för RM 8 är mellan 520 och 554 kg/h, beroende på vilken metod som används. För att uppnå samma avsvavlingseffektivitet med RM 7 måste flödet vara 499–538 kg/h och 427–464 kg/h för A-sten. Med tanke på de jämförbara massflödena för RM 8 och RM 7 är det lämpligt att behålla RM 8 som sorbent i skrubbern, trots den högre magnesiumhalten, på grund av de högre kostnaderna för RM 7. Epsomithalten i slurryn bör dock tas i beakting vid optimering av svavel i cementproduktionen. Att använda A-sten som sorbent skulle minimera råvarukostnaderna och resultera i en renare gipsslurry med lägre epsomithalt. Att använda med en renare sorbent kan också förbättra avsvavlingseffektiviteten, vilket leder till lägre SO2-utsläpp. Beräkningarna i rapporten förutsätter att kalcium och magnesium i de olika sorbenterna reagerar lika, ytterligare analys av deras reaktivitet rekommenderas för mer exakta resultat.

The ever increasing global demand for materials has placed aluminium as the world’s second most used metal, with world annual production currently >24 million tons. Consequently, the global alumina industry is perpetually striving to meet demands in conjunction with research, development and implementation of more efficient and sustainable processes and practises. Of specific concern for many proponents within the industry is that increased alumina production inadvertently results in increased Bayer Process-derived alkaline solid and liquid waste loads. Furthermore, in-house power generation at all Australian alumina refineries contributes to acid gas emissions, particularly SOx and NOx, both of which have environmental and anthropogenic impacts of global concern. The focus of this work is SO2 emission. SOx emission control measures can be achieved before, during or after combustion; the latter is termed flue gas desulphurisation (FGD). Commercially available FGD systems are dominated by once-through wet processes whereby the flue gas passes up through an absorbtion tower. The most favourable medium for industrial use is seawater, followed by limestone, and in some cases, a combination of both. However, the ever-increasing stringency of environmental emission legislation continues to inflict tighter controls on power production and is forcing industry to investigate alternative cost-effective FGD mediums. Therefore much research is currently dedicated to the utilisation of high volume, alkaline waste streams over manufactured sorbents. Modern environmental engineering approaches to waste product minimisation, neutralisation and/or reuse have lead to many new processes which change the view of many materials from waste product to environmental resource. Subsequently, this work examines the application of an isolated Bayer Process waste product, tricalcium aluminate hexahydrate (TCA6), as a FGD medium. Initial research assessed the dissolution behaviour and performance of the proposed medium with sulphuric acid, followed by batch reactor trials with a simulated flue gas. Data derived from this research indicated the suitability of TCA6 as a FGD medium and was subsequently applied to a preliminary model and proposed design parameters required for further pilot scale investigations. This work provides strong support for an economically viable and more sustainable approach to FGD for the alumina industry.

<p>The aim of this project is to investigate the possibilities of minimizing the sulphur content in Kraft lignin. Kraft lignin contains about 1.5 to 3% sulphur. The sulphur is believed to be present in lignin as inorganic sulphur, as elemental sulphur, as adsorbed polysulphide and/or as organically bound sulphur. For the determination of these different types of sulphur components, different approaches and methods were used. For the determination of inorganic sulphur, lignin was washed with water at pH 6 and pH 2 and the wash waters were analysed with ion chromatography (IC). For the determination of total sulphur content in the lignin, two methods were used; Schöniger combustion followed by ion chromatography (IC) and wet digestion followed by inductively coupled plasma (ICP). The elemental sulphur content in water-extracted lignin was determined after n-pentane extraction. ICP analysis was performed on the washed lignin.</p><p>Calcium present in the lignin may bind polysulphides and thus be a source of the observed sulphur. The lignin was thus ion-exchanged to remove any calcium. To further investigate how the sulphur content in lignin can be decreased, two different types of reactions were performed on lignin; oxidation and reduction. The oxidation reactions were made in sodium hydroxide with oxygen at different temperatures and time on both original and water-extracted lignin. The reduction reactions were made on water-extracted lignin with Raney nickel in three different solvent systems: methanol: water, acetone: water and sodium hydroxide.</p><p> </p><p>The original lignin contained 2.6% sulphur as determined by ICP. Washing lowered the content to 1.85% sulphur. By n-pentane extraction the elemental sulphur was lowered to a level of 1.82% sulphur, which was considered to be organically bound sulphur. Neither the ion exchange nor the oxidation lowered the sulphur content significantly.</p><p> </p><p>The reduction reactions successfully the organically bound sulphur from 1.82% to a level of 0.54%.</p><p> </p><p>The relative distribution of the sulphur content in the studied softwood lignin was as follows: about 29% as inorganic sulphur, about 1% as elemental sulphur and approximately 70% as organically bound sulphur, of which 49% could be removed by Raney nickel.</p>