Desulphurization Reaction Research Articles

Desulphurisation and Inclusion Behaviour of Stainless Steel Refining by Using CaO–Al2O3 Based Slag at Low Sulphur Levels

The deep desulphurisation behaviour and steel cleanliness of stainless steel refining in the low sulphur content period (below 45 ppm [%S]) by using the current lime-fluorspar based slag and an optimized lime-alumina slag have been studied and compared. The desulphurisation effect was discussed based on the calculated sulphide capacity of slags and the equilibrated sulphur distribution ratio between the slag and steel. The sulphur evolution during the treatment was predicted with a previously developed kinetic model. The influence of slag chemistry on the compositional evolution of the steel and inclusions was discussed through thermodynamic considerations with respect to deoxidation and desulphurisation reactions. The sulphur content in the inclusions was predicted using the dissolved sulphur in the steel and their oxide chemistry. An equivalent steel cleanliness and desulphurisation effect was obtained with lime-alumina based slag as with lime-fluorspar based slag both in laboratory and industrial tests for low sulphur content stainless refining.

Preparation of bagasse ash/CaO/ammonium acetate sorbent and modelling their desulphurization reaction

The influence of siliceous and hydration agents additives on the preparation of calcium-based sorbents for dry flue-gas desulphurization at low temperature was studied. The key reaction variables investigated are: quantity of bagasse ash, hydration temperature, quantity of ammonium acetate and hydration time. Their effect on the surface area of the sorbent was determined and a central composite design was used as a statistical tool. A polynomial model was established to correlate the sorbent preparation parameters to the sorbent surface area. The desulphurization experiments performed with the thermogravimetric analyser indicate higher SO2 removal when bagasse ash and ammonium acetate are used. The kinetics of desulphurization reaction was fitted using the unreacted shrinking core model and the results show that the rate-limiting step was diffusion over the product layer.

Zinc Incorporated Hydroxyapatite Catalysts: Preparation and Characterization

Ca-hydroxyapatite was freshly prepared by precipitation method and used as a support material for preparing zinc catalysts. The catalysts were prepared by two different techniques: incipient impregnation and ionic exchange. The freshly prepared zinc catalysts were characterized via X-ray diffraction pattern, Fourier transform infra-red spectroscopy, differential scanning calorimeter, and thermo-gravimetric analysis. The replacement of Ca2+ by Zn2+ for the catalyst prepared by the ionic exchange method and the formation of Zn oxide species after impregnation were confirmed by X-ray diffraction patterns. The evaluation of the catalytic activity of Zn-hydroxyapatite catalysts were investigated toward oxidative desulphurization reaction of gas oil. The results show that the sulfur removal reached 88.5 wt% over ionic exchanged zinc catalyst under mild conditions.

Experiment and Micro-Mechanism Research of Fe<sub>2</sub>O<sub>3</sub> Catalysis in Flue Gas Desulphurization in Magnetically Fluidized Bed

A new method of FGD-MFB was presented and the FGD-MFB experiment results showed the efficiency of the FGD-MFB could be improving not only with the enhancing of the intensity of the magnetic field, but also with the decreasing of the diameters of the magnetic particles: When the mean diameter of the magnetic particles(dp) is 220μm, the intensity of the magnetic induction(B) is 40mT,the ratio of the Ca(OH)2 and SO2 (Ca/S) is 1.85, the temperature of flue gas in inlet(T0) is 250°C, the desulphurization efficiency is up to 85.93%. Its micro-mechanism may be that Fe2O3 as an active center changed the formation laws of the desulfurization reaction and the magnetic field affected the characteristics of product and gas diffusion characteristics through by varying micro pore structure and surface layer and, which improve the utilization of calcium and the efficiency. To analyze the catalytic effect of the magnetic field and the magnetic particles on the desulphurization reaction , the instruments of EDAX、FEM and XRD were utilitzed.

Evaluation of limestones for the purposes of desulphurisation during the fluid combustion of brown coal

Laboratory tests of the reactivity of two limestones used for desulphurization of fluidized bed boilers showed that the desulphurization capacity of their calcinates do not yet correspond to routinely applied opinions on the absolute content of CaO in the limestone. Limestone with lower CaO content desulphurised the combustion gas more. This was caused by the fact that the desulphurization reactions of combustion gas are significantly negatively affected by the reaction of CaO with ballast oxides of ash and limestone. The amount of ballast oxides in both limestones rises along with the decrease of the particle size. When choosing proper limestone for the given power equipment it is necessary to respect these side effects. It is useful to pre-select and optimise the distribution the limestone particles according to the nature of the burnt coal. Thereby it is possible to reduce the consumption while complying with the SO2 emission limits.

Chemical Reaction Mechanism of Sintering Flue Gas Desulphurization with Pyrolusite Slurry

With the beginning of the characteristics of sintering flue gas, the thermodynamics and chemical reaction mechanism of sintering flue gas desulphurization with pyrolusite slurry were analyzed and discussed in the paper. Results shown that the main chemical reaction was oxidation-reduction reaction of sulfur dioxide and manganese dioxide with a high reaction velocity and desulphurization efficiency at the first stage. The reaction speed and the desulphurization efficiency decreased gradually and Mn2+ is used as catalyst in the desulphurization reaction with the proceeding of chemical reaction and decreasing of PH value of solution.

Effect of Desulfurization Ash with Different Calcium Sulfite Content on Performance of Cement Based Materials

According to the desulphurization reaction temperature and the content of calcium sulfite, FGD ash is simulated, that is the ordinary fly ash mixed with different weight percentage of CaSO3·1/2H2O is followed by drying at 100°C. And then by the experiment of workability, strength, sulfate resistance and rebar corrosion, the effect of the fly ash with different of CaSO3·1/2H2O on material properties are studied. The results show that: compared with ordinary fly ash, the desulphurization ash contained 4~12% CaSO3·1/2H2O can improve workability, but it has a 4% threshold, over critical value, the improving ability declined; secondly increasing the content of CaSO3·1/2H2O in desulphurization ash can decrease strength, and while the effect of 7 day strength is higher than 28 days’; Thirdly, with the increase of calcium sulfite, the desulphurization can decrease resistance to sulfate attack , especially for more than content of 8% CaSO3·1/2H2O , but it is harmless for steel rebar.

Research for Using Iron & Steelmaking Zinc Laden Dust to Desulphurisze Hot Metal

AbstractIn order to promote recycling of zinc laden dust, desulphurizing hot metal using the dust has been researched on a laboratory scale and the possibility of developing a new desulphurization (De‐S) method has been evaluated. The thermodynamic data of the Zn‐O‐S system has been determined with an electrochemical cell. The results indicate that ZnS sublimes at a temperature between 1450 and 1460 K. Directly as a result of this phase change the driving force for desulphurization with Zn or ZnO increases with increasing temperature beyond this sublimation temperature, thus potentially making Zn based reagents useful for high temperature desulphurization reactions. Feasibility reactions were also performed to confirm that ZnO can effectively react with FeS (1473 to 1653 K) or with Fe‐Csat‐S (1473‐1673K) to remove S. There is therefore potential for the utilization of ZnO laden waste dust or granular zinc as additional or alternative reagents for desulphurization. This paper provides a theoretical basis and the feasibility for granular Zn (and/or ZnO) replacing granular Mg for desulphurizing hot metal.

Intensification of hydrodesulphurization process with a structured bed spiral mini-reactor

The procedure followed for the study of the characteristics of the intensification of catalytic hydrodesulphurization process with a structured bed spiral reactor is presented in the current work. This procedure consists of two parallel experimental methods investigating the mechanisms involved in the operation of the reactors. The first method aims at the study of the process mechanisms with mock up experiments at ambient conditions using systems with inorganic or organic liquids, water or heptane, and oxygen or nitrogen as gas phase. The second one focuses on the mechanisms at reaction conditions using simple model reactions, like benzene hydrogenation. The studied mechanisms with the methods followed are the fluid dynamic characteristics of the operation of spiral reactor, flow regime, axial dispersion and mass transfer limitations. The mass transfer limitations were also studied with desulphurization experiments taking into account the impact of the inhibitors hydrogen sulphide and ammonia on the desulphurization reaction.

Hydrogenative desulphurization of thienopyrrolizinones: An easy and selective access to ( Z)-phenethylidenepyrrolizinones with in vitro cytotoxic activity

Attempts in view to dearomatize some previously reported tripentones with potent antineoplastic activities led in thiophene series to an unexpected hydrogenative desulphurization reaction. The resulting ( Z)-phenethylidenepyrrolizinones were tested in vitro over human epidermoid carcinoma KB cell line. The results of this biological evaluation indicated that the tricyclic core of our model can be cleaved with a partial respect of the activity.

Kinetic Models Study of Hydrodesulphurization Vacuum Distillate Reaction

This study deals with kinetics of hydrodesulphurization (HDS) reaction of vacuum gas oil (611-833) K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 – 650) K, medium vacuum gas oil (650- 690) K, heavy vacuum gas oil (690-727) K and very heavy vacuum gas oil (727-833) K. The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643) K,liquid hourly space velocity range (1.5-3.75) h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt. The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea), enthalpy of activation ( H*) and entropy ( S*) were calculated based on the values of rate constant (k2) and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.

Chemically ubiquitylated histone H2B stimulates hDot1L-mediated intranucleosomal methylation

Numerous post-translational modifications of histones have been described in organisms ranging from yeast to humans. Growing evidence for dynamic regulation of these modifications, position- and modification-specific protein interactions, and biochemical crosstalk between modifications has strengthened the 'histone code' hypothesis, in which histone modifications are integral to choreographing the expression of the genome. One such modification, ubiquitylation of histone H2B (uH2B) on lysine 120 (K120) in humans, and lysine 123 in yeast, has been correlated with enhanced methylation of lysine 79 (K79) of histone H3 (refs 5-8), by K79-specific methyltransferase Dot1 (KMT4). However, the specific function of uH2B in this crosstalk pathway is not understood. Here we demonstrate, using chemically ubiquitylated H2B, a direct stimulation of hDot1L-mediated intranucleosomal methylation of H3 K79. Two traceless orthogonal expressed protein ligation (EPL) reactions were used to ubiquitylate H2B site-specifically. This strategy, using a photolytic ligation auxiliary and a desulphurization reaction, should be generally applicable to the chemical ubiquitylation of other proteins. Reconstitution of our uH2B into chemically defined nucleosomes, followed by biochemical analysis, revealed that uH2B directly activates methylation of H3 K79 by hDot1L. This effect is mediated through the catalytic domain of hDot1L, most likely through allosteric mechanisms. Furthermore, asymmetric incorporation of uH2B into dinucleosomes showed that the enhancement of methylation was limited to nucleosomes bearing uH2B. This work demonstrates a direct biochemical crosstalk between two modifications on separate histone proteins within a nucleosome.

Application of the sulphide capacity theory on refining slags during LF treatment

Sulphur has been reduced from 0.02wt% to 0.002wt% in 38 min average during 200 t ladle treatment in 2 # steel plant of Capital Steel. The sulphide capacity and equilibrium sulphur distribution of slags are calculated and compared with the measured values. The results show that the KTH model is a useful tool for the prediction of sulphide capacity and sulphur distribution during ladle treatment; the desulphurization reactions are completed nearly in thermo-equilibrium.

Effect of cerium sulphide particle dispersions on acicular ferrite microstructure development in steels

Of the phases found in wrought steels, cerium sulphide particles are notable in that they can be both stable at liquid metal temperatures and exhibit good lattice coherency with α iron. An investigation has been carried out to determine the effectiveness of cerium sulphide particle dispersions in nucleating intragranular acicular ferrite microstructures in steels. Vacuum melts of 50 kg have been manufactured of appropriate base steel compositions with varying additions of cerium (0·04–0·18%) and sulphur (0·01–0·04%). The work has shown that 0·02–0·12% cerium and 70–340 ppm sulphur may be retained in steels after deoxidation and desulphurisation reactions while oxygen can be reduced to <20 ppm. Resulting inclusions are largely spheroidal in shape and consist of several crystalline compounds, notably CeS, Ce3S4 and Ce2O2S. The inclusion numbers are of the order of 0·68–6·12 × 106 mm−3 with mean diameters of 0·63–1·70 μm. The densities of these inclusion dispersions are approaching those in weld metals where acicular ferrite is the dominant microstructure constituent. Significant volume fractions of acicular ferrite (up to 65%) have been obtained in steels after thermally cycling in a dilatometer and cooling at rates simulating transformation conditions ranging from high heat input welding to air cooling of forgings and water cooling of plate. A potential beneficial effect of acicular ferrite on mechanical properties in high heat input welding (heat affected zone grain refinement) and in thermo-mechanically processed steels (relaxed schedules) has been highlighted. A pilot plant billet cast of steel has shown the feasibility of achieving the required particle dispersions and acicular ferrite microstructure in tonnage steelmaking.

Diethynyl-thiophene adsorbed on Cu(1 0 0) investigated by NEXAFS and XPS

Studies on the chemical stability and interface interaction of diethynyl-thiophene (DET) condensed multilayer at 90K on Cu(100) are reported. The temperature influence in the multilayer and monolayer range has been investigated by means of near edge X-ray absorption fine structure (NEXAFS) spectroscopy at the C K-edge. The NEXAFS spectra were recorded at 90K, 150K, 200K, 245K and 298K. Comparison with X-ray photoemission spectroscopy (XPS) data, collected on DET at similar temperatures, has also been accomplished. NEXAFS spectra recorded for the multilayer show a strong similarity with those of our previous NEXAFS theoretical and experimental investigations in gas-phase. The multilayer spectra appear affected by the temperature from 90K to 155K, while after desorption a broadening of the main π* region occurs, indicative of interaction with the substrate. XPS data at the S2p core level suggests a partial desulphurization reaction that takes place at nearly room temperature with the S–C replaced by a Cu–C bond.

Oxidation of high sulphur coal.9 3. Desulphurisation of organic sulphur by peroxyacetic acid (produced in situ) in presence of metal ions

A chemical oxidative desulphurisation method for coal organic sulphur has been presented using peroxyacetic acid produced in situ as an oxidant. Sulphur is removed to the extent 6.92–10.02 wt.% at 1–4 h while at 24 h, it increases to 13.41 wt.%. To understand the influence of metal ions on desulphurisation, each of six metal ions of variable valence states (Cu +, Ni 2+, Co 2+, Sn 2+, Pd 2+ and Sb 3+) was externally added. Lowest sulphur loss with Ni 2+ ion (2.26–9.46 wt.% at 1–4 h and 11.01 wt.% at 24 h) while highest desulphurisation with Pd 2+ ion (23.15–32.32 wt.% at 1–4 h and 32.75 wt.% at 24 h) are observed. Application of the pseudo-first order kinetics shows rate constants for all the systems in the range (0.70–6.78)×10 −5 s −1. The activation energy and frequency factor for these systems fall in the range (8.46–12.66) kJ/mol and (1.15–2.64)×10 −3 s −1, respectively. Low frequency factor represents an associated type of desulphurisation reaction involving intermediate activated complexes. The sulphur loss reaction is non-spontaneous in nature and proceeds with the absorption of heat. Occurrence of the reaction is due to the increase in randomness which is governed by the decomposition of activated complex to products and is influenced by the characteristic property of a metal ion. Study of model sulphur compounds (methionine and dibenzothiophene) reveals that the desulphurisation reaction under the experimental conditions is primarily due to aliphatic sulphur compounds. The method described here is simple with low-cost and easily available chemical, and therefore, has considerable technological interest.

Desulphurization of organic sulphur from coal by electron transfer process with Co 2+ ion

This paper reports the results of desulphurization of organic sulphur from a subbituminous Meghalaya coal by the electron transfer process accomplished with the metal ion Co 2+. The process was studied both in presence and absence of naphthalene which is used as an electron transfer agent. Temperature dependence on desulphurization unfolded that as the temperature is raised from 25 to 50 °C, there is increase in desulphurization performance. Model organic sulphur compounds study revealed that the desulphurization process is effective with aliphatic type of compounds. Infrared spectroscopic study revealed the release of easily removable sulphur compounds as the band intensities due to −S O and −SO 2 groups have declined considerably in their respective regions in the desulphurized coals. The degree of desulphurization is 28.5 wt.% in the presence of naphthalene and 24.6 wt.% in absence of naphthalene, both at 4 h and 50 °C. The sulphur extrusion process is continuous and application of a first-order kinetic model produced specific rate constants of the desulphurization reaction in the two systems, at different temperatures, which falls in the range of (1.3–2.9)×10 −5 s −1. The activation energy of the sulphur-loss reaction in the system containing naphthalene (26.8 kJ mol −1) is about 12% lower than that of the system without naphthalene (30.6 kJ mol −1). The frequency factor of the sulphur removal reaction in the systems have been found to be in the range of 0.8–3.2 s −1, suggesting low amount of successful collisions and an associated type of reaction. The desulphurization reaction is nonspontaneous in nature, proceeds with the absorption of heat and there is reduction in the degree of disorderliness in the system as predicted by the transition state theory.

Slag Emulsification during Liquid Steel Desulphurisation by Gas Injection into the Ladle

According to current practice, the desulphurisation of steel melts is mainly performed in the ladle with lime saturated top slags. The injection of argon gas into liquid steel provides for intensive mixing and accelerated sulphur transfer. During gas stirring treatment, an emulsification of top slag takes place. A numerical model describing the course of the desulphurisation reaction has been developed, which takes all relevant process parameters into account, including those of the emulsification effect. To check the validity of the model, operational tests have been performed on 185‐t‐heats. Results obtained from model calculations and operational tests show an excellent agreement.

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.

Thermodynamic and kinetic aspects of the desulphurisation reaction in secondary metallurgy

The desulphurisation of liquid steels with a refining ladle top slag is one of the most important processes of secondary metallurgy. But the process control is even now based on empirical rules. Deviations from the sulphur contents aimed at can often be observed in practice. An improvement of the process control supported by knowledge of the thermodynamics and kinetics of the desulphurisation reaction is of great importance, especially for the production of steels with very low sulphur contents.To investigate the removal of sulphur, operational trials were carried out in 185 t steel ladles. In the trials the stirring gas flow rate, the pressure on the bath surface and the steel composition were varied as process parameters. The obtained results show that ladle slags saturated with lime have a high sulphide capacity. The desulphurisation rate of steel melts increases if the specific stirring energy is enhanced by increasing the gas flow rate or reducing the pressure on the bath surface. In the case of production of Al/Si‐killed steel melts, a desulphurisation degree above 90 % can be obtained by a vacuum treatment within 10 minutes.