Desulphurization Rate Research Articles

Study on Sulfur Control Technology for Non-Oriented Electrical Steel

In cognizance of the problems of low desulphurization rate for hot metal, large sulfur-recovery in converter, as well as high sulfur content in products when producing non-oriented electrical steel with vanadium-content hot metal, countermeasures have been carried out. Sulfur content in non-oriented electrical steel is decreased obviously with the study on technologies of desulphurization for hot metal with vanadium & titanium, sulfur-recovery control in converter, and desulphurization in RH refining process as well. The results of industrial tests show that the rate of w（S）≤0.008 % is as high as 100 %, and the rate of w（S）≤0.005 % reaches 91.43 %. And besides, sulfur mass fraction is 0.004 2 % on average (0.001 9 %~0.006 9 %).

Study on Desulphurization Technology in RH Refining for Electric Steel

To develop the desulphurization technology for electric steel, desulfurizer using for electric steel in RH refining process has been studied. Meanwhile, key technologies such as converter end-point control, modification of ladle slag in secondary refining process, as well as desulphurization technology in RH refining process are studied deeply. Industrial tests show that desulphurization rate in RH refining process is as high as 28% for electric steel, and the ratio which sulfur content below 0.005% is as high as 70%.

Study on the Kinetics of Phosphor-Gypsum Pyrolysis

In this paper, an Infrared Sulfur Analyzer is set to measure the desulphurization degree during thermal decomposition of phosphor-gypsum, which provides a much quick, convenient, continuous and accurate method. It might be considered as an effective way to study kinetics of phosphor-gypsum (or phosphogypsum) thermal decomposition (or pyrolysis). With the help of this method, the desulphurization degree and desulphurization rate of broadly constituted phosphor-gypsum samples in the temperature range of 1250-1400°C were studied. The experimental results show that the desulphurization degree increase with the rising of temperature in the range of 1250-1300°C quickly, however, this increase is not obvious when the temperature is above 1300°C. Besides, the corresponding regression equations are obtained. The decomposition degree of phosphor-gypsum could be judged according to the regression equations mentioned above.

Vegetable oil effect on gasoil HDS in their catalytic co-hydroprocessing

The effect of the presence of triglycerides on the catalytic hydrodesulfurization (HDS) of gasoil and the hydrogen consumption reactions have been studied during catalytic hydroprocessing of gasoil–palm oil mixtures at conventional hydrotreatment conditions over a commercial CoMo/γ-Al2O3 catalyst. The experiments were performed at a pressure of 33bar, three temperatures (310°C, 330°C and 350°C), and three values of WHSV (0.7h−1, 1h−1 and 1.4h−1). Desulphurization rates decreased with palm oil content from 0 to 5% but they did not change with a further increase to 10%. Hydrogen consumption rates were not affected by the presence of the vegetable oil molecules. Simple power law formal kinetics has been applied to simulate the desulphurization and hydrogen consumption rates of the gasoil–palm oil mixtures.

Desulphurization of some low-rank Turkish lignites with crude laccase produced from Trametes versicolor ATCC 200801

In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.

Study on coal bio-magnetizing desulphurization

Coal Bio-desulphurization is a kind of new technology of coal resource effective and reasonable utilization. The bio-magnetizing technology was used in coal desulphurization bacterium Thiobacillus ferrooxidans cultivate in this paper, the effect of magnetization and non-magnetization culture on the growth of the desulphurization bacteria was investigated. Using the magnetizing cultivate China coal-series and non-coal-series Thiobacillus ferrooxidans to remove the pyrite sulfur from coal was studied. The result shows that the magnetizing environment growth for mineral chemical nutrition desulphurization bacterium Thiobacillus ferrooxidans has obvious promote role, magnetizing cultivate coal-series Thiobacillus ferrooxidans the maximum desulphurization rate of Thiobacillus ferrooxidans is 86.16% under bioleaching of 24 d and coal sample size of 0.075 mm, compared with non-coal-series Thiobacillus ferrooxidans desulphurization rate is 82.56%. The magnetizing cultivate coal-series Thiobacillus ferrooxidans has a better removing efficiency for pyrite from coal.

Effect of Nitrogen Alloying on Sulphur Behaviour during ESR of AISI M41 Steel

In this work, the effects of nitrogen alloying, physical properties and chemical composition of slag used in electro‐slag refining (ESR) on phosphorus and sulphur contents of AISI M41 high speed steel have been studied. The experiments were conducted with two high speed steel grades which were melted in an induction furnace (IF). The first grade is the standard AISI M41 high‐speed steel and the second one is nitrogen alloyed M41 (denoted M41N). The produced ingots were ESR remelted under three grades of calcium fluoride based slag. Results showed that the ESR process has no effect on the phosphorus content in steel but it is a good tool in removing sulphur. This study shows that a high desulphurization rate can be achieved by ESR process by optimizing slag properties where the viscosity and oxidation reactions play an important role in sulphur removal. Nitrogen alloying was found to retard sulphur removal.

PROJETO E OTIMIZAÇÃO DE REATOR DE DESSULFURAÇÃO DO GUSA ATRAVÉS DE MODELO DE TRANSPOSIÇÃO DE RESULTADOS

The hot metal desulfurization has been speeded up by adoption of lime-Mg process. In this process, the magnesium is used to reduce the oxygen content in the hot metal to almost zero, increasing the deS power of the lime, thus explaining the efficiency of such process. In the present study, preliminary experiments were carried out in cold models, using rotating lance, which resulted in a better material distribution. The rotating lance tested in the hot metal desulphurization plant of Usiminas’ Steel Plant 1 promoted a 18% increase in the desulphurization rate, a 54% decrease in temperature drop during the treatment, as well as a reduction of metal splash occurrences. It was applied a transposition model, whose criteria takes into account the equipment dimensions and the mass flow rate of the desulphurization material. In order to evaluate the applicability of the this model, the results of hot metal desulphurization obtained in a 100 kg atmospheric induction furnace were transposed to a 160 t torpedo car. The theoretical desulphurization results were very close to the measured values. It was possible, from these results, to predict the desulfurization rate, the material consumption and the treatment time, which can indicates the technical and economical viability of the rotating lance.

Assessment of ettringite from hydrated FBC residues as a sorbent for fluidized bed desulphurization ☆

The performance of synthetic ettringite as a sorbent in fluidized bed desulphurization has been assessed and compared with that of a commercial limestone. Experiments have been carried out in a bench scale fluidized bed reactor under simulated desulphurizing (steadily oxidizing) combustion conditions. Sorbent performance has been characterized in terms of desulphurization rate, maximum sulphur uptake and attrition propensity. Fluidized bed sulphation experiments have been complemented by microstructural characterization of solid samples, accomplished via X-ray diffraction analysis, scanning electron microscopy and sulphur mapping of cross-sections of particles embedded in epoxy resin. Experimental results show that both the rate and the maximum extent of sulphur uptake by ettringite significantly exceed those of the limestone. Maximum degree of free calcium utilization is 0.58 for ettringite compared with 0.27 for the limestone. Sulphation tests also indicate that attrition propensity of ettringite is larger than that correspondingly observed for the limestone. Microstructural characterization indicates that sulphation of ettringite takes place evenly throughout the particle cross-section, whereas sulphation of limestone mostly conforms to a core-shell pattern. Along a parallel pathway, the rate and yield of ettringite formation by hydration of fly ash from a utility fluidized bed boiler have been assessed. Formation of ettringite in these experiments appears to be quantitative upon curing of ash at 70 °C for times up to 4 days.

A model of reoxidation from the top slag and the effect on sulphur refining during vacuum degassing

A 2‐dimensional fluid‐flow model covering 3 phases (steel, slag and gas) has been augmented to include thermodynamic equations to study simultaneous reoxidation and desulphurization, including macro kinetic behaviour. The numerical simulations were isothermal. Predicted steel and slag component concentrations were compared with plant data from vacuum degassing and the agreement was found to be quite good. When the initial FeO content in the slag was increased, the predicted desulphurization rate decreased, the final sulphur content in the steel increased, and aluminium loss increased. When the temperature was increased, the predicted aluminium loss decreased somewhat. The effect of changes in temperature on the predicted final sulphur content was influenced by the initial FeO content in the top slag. The results show that the model can be used for future work on the dynamic modelling of slag/metal reactions if the initial FeO content is less than 3–4% (by weight).

The Modulation of Desulphurization Properties of Calcium Oxide by Alkali Carbonates

Kinetics of CaO desulphurization reaction and the effects of alkali carbonates on it have been investigated by thermogravimetric analysis. A grain model was applied successfully to describe the kinetic behavior of the reactions. The activation energy of surface reaction and that of the product layer diffusion were determined by using the model. It was found that the overall desulphurization rate was controlled initially by surface chemical reaction and, in a later stage, by product layer diffusion. Addition of alkali carbonates can decrease the activation energy of the surface chemical reaction, with increasing effectiveness in the order of potassium, sodium and lithium. Such a property of alkali carbonates has also been demonstrated on a raw coal. The process is discussed in terms of a working mechanism of solid-state ionic diffusion.

Mathematical Model of Hot Metal Desulphurization by Powder Injection

A macro kinetic analysis of the hot metal desulphurization with powder injection has led to that there are three basic parameters which determine the desulphurization rate, as well as the power utilization efficiency. They are the penetration ratio (PR) of injected powder into the melt, the residence time distribution (RTD) of injected powder in the bath, as well as the homogeneous mixing time (HMT) of the bath. Both PR and HMT have been experimentally determined with water modeling, while the RTD has been determined from either flow field information or experimental measurements of water model with stimulus-response method, arriving at the correlation formulas between the parameter and the injection operation variables as well as powder characteristics. This has enabled the development of a mathematical model to predict the desulphurization process.Based on further analysis of the mechanism and macro kinetics of the process, a mathematical model has been developed, with the three basic parameters being taken into account, to simulate the variation of [S] in hot metal with time. Water-model experiment results, flow field information and industrial data are used to determine the model parameters and verify the model, leading to the result that the prediction from the model agrees well with practical results. In addition to CaO and CaC2 powders, the use of granular Mg has been particularly included and emphasized in the model for its more and more popular application. The coupling effect of hot metal desulphurization by injection of magnesium-CaC2 mixture was discussed.

Biodesulphurization of Turkish lignites. 3. The effect of lignite type and particle size on microbial desulphurization by Rhodococcus rhodochrous

The effects of lignite type and lignite particle size on the rate of sulphur removal were studied. Biodesulphurization experiments were carried out with Mengen, Elbistan, Tunçbilek and Gediz lignites at the optimum growth conditions of Rhodococcus rhodochrous. The highest decreases in the total (25.3%) and organic sulphur contents (21.4%) were obtained with Gediz and Mengen lignites, respectively. Furthermore, increased desulphurization rates have been observed with smaller particle sizes. Reduction in particle size from 390 to 63 μm resulted in an increase in total sulphur and organic sulphur removal rates by factors of 2.8 and 19, respectively.

Physico-Chemical Characterization and Leaching of Desulphurization Coal Fly Ash

Fly ash produced by coal combustion using two types of desulphurization process were studied: a conventional pulverized coal boiler equipped with lime injection (PCL ash), and a circulating fluidized bed combustion boiler with limestone injection (CFBC ash). The ashes were characterized completely: granulometry, morphology, mineralogy, chemical composition and behaviour to water contact. Both PCL ash and CFBC ash present similar features: fine granulometry, presence of anhydrite phase and sulphate content. However, PCL ash also shows lots of spherical particles, unlike CFBC ash, and a much higher lime content, due to the lower desulphurization rate in PC boilers. Unlike CFBC ash, most of the trace elements in PCL ash show an inverse concentration-particle size dependence. Leachates obtained from both samples are rich in soluble salts [CaSO4 and Ca(OH) 2] and arsenic and selenium are prevented from solubilizing by high lime content. In wetted PCL ash, the formation of ettringite crystals stabilizes calcium and sulphate ions. Simultaneously, arsenate, selenate and chromate anions are trapped in the crystal. CFBC ash does not really harden because the lime content is too low. However, the leached selenium concentration is cut down in wetted CFBC ash samples. © 1996 ISWA

Physiological adsorption of Sulfolobus acidocaldarius on coal surfaces

The adsorption of Sulfolobus acidocaldarius on bituminous coal surfaces and the respiration rate during adsorption at 70° C were enhanced at pH 1.0–2.0, in comparison with those at pH 3.0–5.0. The maximum number of bacterial cells adsorbed per unit area of coal attained a maximum (1.4 × 1011 cells/m2) at pH 2.0. The rate of desulphurization at pH 2.2–2.5 was higher than at other pHs tested. Micrographs of S. acidocaldarius obtained by TEM and SEM indicated that the cells were adsorbed to the coal surfaces by extracellular slime. Specific inhibitors of membrane-bound ATPase (NaF, 20 mm) and respiration (NaN3, 1 mm; KCN, 1 mm) had pronounced effects on suppressing adsorption. The amount of S. acidocaldarius adsorbed decreased when the coal particles were leached in advance with 2.0 m HNO3. These facts lead to the conclusion that the adsorption of S. acidocaldarius on coal surfaces requires physiological activity relatd to respiration or energy conversion.

The role of microwave irradiation in coal desulphurization with molten caustics

The rate of coal desulphurization was promoted by microwave irradiation with a molten mixture of NaOH and KOH. To investigate the role of microwave irradiation, the rate of penetration of molten caustics into a porous body was measured using a graphite tip which was inert to the molten caustics. When the graphite tip was impregnated with surfactants by immersing in an aqueous alkaline solution, the penetration rate increased without microwave irradiation. The desulphurization rate of coal samples pretreated by this procedure also increased without the use of microwaves. These findings suggest that microwave irradiation facilitates the contact between coal and the molten caustics, and that the rate determining step is not chemical reaction but mass transfer of the molten caustics into the coal matrix.

Hydrotreating of Qaiyarah deasphalted residue

Qaiyarah reduced crude (QRC), which constitutes 70.5 wt% original crude oil, was deasphalted with n-pentane under specified conditions. The deasphalated oil (64.4 wt% of QRC) with sulphur content 4.2 wt% was hydrotreated on commercial Co-Mo-alumina catalyst on a trickle-bed reactor. The temperature varied from 340–400 °C with liquid hourly space velocity (LHSV) ranging from 0.69–2.9 h −1. Hydrogen pressure was kept constant through the experiment at 8.0 MPa, with a hydrogen/oil ratio of about 300 v/v. The hydrodesulphurization reaction of the deasphalted oil followed second-order kinetics. Desulphurization rate constants were calculated using a second-order equation ( k) and a model comprising two parallel first-order reactions ( k 1 and k 2). The apparent activation energy ( E a ) was calculated based on the values of k, k 1 and k 2. A study of the change in saturates, aromatics and polar aromatics of feedstock and hydrotreated products during the hydrotreatment process indicates that the saturates increase significantly while the aromatics plus polar aromatics decrease.

Kinetics of catalytic hydrodesulphurization of a deasphalted oil and of the asphaltenic and non-asphaltenic fractions of a petroleum residue

The kinetics of the catalytic hydrodesulphurization of a deasphalted oil, obtained from the atmospheric residue of the Greek Thasos crude oil, as well as of the asphaltenic and non-asphaltenic fraction of the residue were investigated. A batch recycle trickle bed reactor was used for the desulphurization experiments, which were carried out at a pressure of 50 bar and temperatures in the range of 350 – 400°C. A second order kinetic equation describes very well the desulphurization rates of both the deasphalted oil and the non-asphaltenic fraction of the residue. The activation energy was found to be 19 kcal (mol −1 S) in both cases and the values of the rate constants were identical. The desulphurization rates of the asphaltenic fraction of the residue are well described by a third order kinetic equation. The activation energy was calculated as 53 kcal (mol −1 S). The effect of the presence of asphaltenes on the hydrodesulphurization rates of the non-asphaltenic molecules is discussed and a qualitative model for the hydrodesulphurization reactions of asphaltenes is presented.

Sulphur in char and char desulphurization by acid leaching and hydropyrolysis

Sulphur compounds volatilized during pyrolysis of acid-leached char were measured to determine characteristics of char desulphurization reactions. Pyrolysis of char in a hydrogen atmosphere (hydropyrolysis) produced a much higher concentration of thiophenic organics compared with that produced during pyrolysis in a nitrogen atmosphere. Hydrogen sulphide gas evolution, at progressively increasing pyrolysis temperature in a helium atmosphere, was measured on five char samples: untreated char, hydrochloric acid-leached char, and three model chars: a demineralized char and two demineralized chars incorporated with sulphur via reactions with elemental sulphur. Hydrogen sulphide gas evolution in untreated char and acid-leached char was found to peak in three temperature regions; the maxima are thought to relate to sulphur in different bonding environments. The amounts of hydrogen sulphide volatilized were much higher for acid-leached char than for untreated char. The gas evolved from each of the remaining three samples showed a single peak region corresponding closely to one of the three peak regions observed for the first two chars. The results of this study indicate that elemental sulphur was produced during hydrochloric acid leaching of the untreated char and suggested that the improved rate of desulphurization observed in the char that had been acid-leached before hydropyrolysis was due in part to the conversion of strongly bound mineral sulphur forms to more weakly bound sulphur forms that are predominantly elemental sulphur in character, and are more easily removed by hydrogen.

The Role of an Interfacial Product Layer in Magnesium Desulphurization of Molten Iron

The desulphurization kinetics of molten iron by magnesium vapour were studied using 60 kg heats of carbon-saturated iron at 1523K. Magnesium dissolution and desulphurization rates, as well as magnesium bubble size, were monitored over sulphur contents ranging from 0.0002 to 0.2% S. The magnesium dissolution mass transfer coefficient (0.046 ± 0.034mm s−1 for 30-mm dia bubbles) was independent of sulphur content and also lower than expected from potential flow theory. Thus the dominant magnesium activity probably held surfactant activity and inhibiting effects at constant levels. Moreover, it was concluded that continuous hydrodynamic shear on the magnesium sulphide coating prevented blockage of the bubble interface. Therefore, magnesium was free to dissolve in the melt in large quantities.Further analysis indicated that most of the desulphurization took place by precipitation on magnesium sulphide inclusions present in the bath: there was good agreement between the experimental rate constant and that predicted for diffusion to the number ofinc1usions observed chemically and metallographically. The “seed” magnesium sulphide inclusions were probably portions of the interfacial product layer stripped from the ascending magnesium bubbles. These particles were quickly eliminated from the melt by bubble and induction stirring, resulting in a steady-state number ofinc1usions. This allowed a pseudo-steady-state model to be developed. Résumé La cinétique de la desulfurisation du fer fondu par de la vapeur de magnésium a été étudiée en utilisant une charge de 60 kg de fer sature en carbone à 1523K. Les taux de dissolution du magnésium et de désulfurisation, ainsi que la taille des bulles de magnésium, ont été suivis pour des teneurs en souffre allant de 0.0002 à 0.2% S. Le coefficient de transfert de masse (0.046 ± 0.034mm s−1 pour la taille des bulles de 30 mm), par la dissolution du magnésium s'est montré indépendant de la teneur en soufre et plus faible que le permettait de prévoir la théorie du flux potentiel. Ainsi, l'activité dominante du magnésium avait probablement maintenue l'activité de surface et les effets inhibiteurs à des niveaux constants. De plus, il fut conclue que le cisaillement hydrodynamique continu sur l'enveloppe du sulfure de magnésium empêche le blocage de l'interface de la bulle. Par conséquent, le magnésium était libre de se dissoudre en grande quantité dans le bain fondu.Une analyse plus poussée a indiqué que la plus grande partie de la désulfurisation avait lieu par précipitation sur les inclusions de sulfure de magnesium présentes dans le bain. La concordance entre les constantes experimentales des taux et celles prevues pour la diffusion en raison du nombre d'inclusions observées chimiquement et par métallographie, était bonne. Les germes des inclusions de sulfure de magnésium étaient probablement des portions du produit de la couche interfaciale qui était enlevée lors de l'ascension des bulles. Ces particules furent rapidement éliminées du bain par les bulles et l'agitation magnétique, pour donner un numbre stationnaire d'inc1usions. Ceci permet de développer un modèle pseudo-stationnaire.