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Capture and fixation of sulfur ( )
Abstract
Sulfur is evolved by most copper extraction processes. The most common form of evolved sulfur is sulfur dioxide (SO2) gas from smelting and converting. It must be prevented from reaching the environment. Most smelters capture a large fraction of their SO2. It is almost always made into sulfuric acid, occasionally liquid SO2 or gypsum. This chapter describes off-gases from smelting and converting, manufacture of sulfuric acid from smelter gases, and recent and future developments in sulfur capture.
... Большинство процессов извлечения меди сопровождается выделением серы, а наиболее распространенной формой выделяющейся серы является газообразный диоксид серы (SO 2 ), образующийся при плавке и конвертировании [3]. Процесс улавливания и фиксации серы необходим в первую очередь с целью недопущения попадания ее в окружающую среду. ...
The review, based on the publications by both Russian and international researchers, presents an analysis of the problems of existing technologies for smelting copper concentrates. Three main problems requiring solutions were identified and considered: increasing the efficiency of smelting copper sulfide-containing ores by reducing the copper content in slags obtained during the conversion process; increasing efficiency, including by obtaining an additional economic effect from waste disposal; reducing the harmful impact on the environment. It was stablished that trends towards the development of new efficient, environmentally friendly and cost-effective technologies are characteristic not only of the selected research object, but also of a number of other non-ferrous metals, such as lead and zinc.
In an ideal world in which sulphuric acid plant operators could have anything they wish for, many would request an acid plant that never experiences corrosion, never has gas leaks, and never needs catalyst screening. And yet that is not the reality. All sulphuric acid plant operators experience acid mist carryover from sulphuric acid towers at some stage. If this is not detected and corrected quickly, extensive damage can be caused to downstream equipment. Not all mist carryover issues arc related to poorly performing mist eliminators. This paper presents a review of the entire tower as a unit and discusses how process conditions, packing, acid distribution, mechanical factors, or mist eliminators affect the performance of the tower, a? well as early detection and troubleshooting tools and methods. © The Southern African Institute of Mining and Metallurgy. 2017.
With increasing use of oxygen enrichment and advances in smelting technology, SO> concentrations in smelter off-gases are increasing, which necessitates larger acid plant equipment and increases in capital and operating. To counteract the shortcomings in conventional acid plants, Chemetics provides two unique solutions: The Chemetics High Strength (CHS™) process and the Chemctics Pseudo Isothermal process utilizing the CORE™ reactor technology. In this paper we present a general outline of these two solutions and how they can be implemented in new or existing acid plants. © The Southern African Institute of Mining and Metallurgy. 2017.
The CSD from Palabora mining company's copper-plant in Limpopo, South Africa was characterized by particle size, chemical and morphological analyses. The dust from the electrostatic precipitator (EPS) attached to the reverberatory furnace was collected and used for this study. The results obtained showed that the dust contains particles mainly in the 53μm size fraction. As regards chemical composition, it is made up of about 18.02 weight % copper, occurring predominantly as cuprospinel and as chalcopyrite. The major impurities in the dust are 42.97, 11.69, 11.45 and 1.6 weight % of mullite, gypsum, silica and magnetite, respectively with traces of lead and bismuth. Morphologically, the particles range from spherical to irregular in shape, with close association occurring between these spherical minerals suspected to be copper and the tabular shaped minerals likely to be gypsum. Smaller copper particles, 1 to 2μm size, were also found embedded in larger spherical particles 8 to 10μm size. The results obtained thus strongly indicate that the CSD as-received is an ultra-fine, copper rich secondary resource that might have been formed in two stages of condensation. Furthermore, the results indicate that physical beneficiation of the CSD in this size fraction of 53μm may be difficult and solvent extraction with prior froth flotation and leaching may be required to efficiently extract the copper value in it.
To find some new desulfurizers for the smelter off-gas containing high levels of SO2, both the sulfur recovery performance and the regeneration performance of the sulfides of alkali metals and alkaline-earth metals were compared in both simulation and experiment. Although sodium sulfide(Na2S) showed a good sulfur recovery performance, its regeneration performance was poor due to the production of polysulfides. Calcium sulfide(CaS) was a feasible option of the desulfurizer because both its sulfur recovery performance and regeneration performance were satisfactory. CaS was prepared after the reduction of the commercial CaSO4(Red-Ca), the flue gas desulphurization gypsum(Red-FGD), the phosphogypsum(Red-P) and the titanogypsum(Red-Ti), respectively. The results showed that the performances of Red-Ca and Red-FGD were quite similar and both of them were distinctly better than Red-P and Red-Ti. According to XRF analysis and XRD patterns, the impurities in Red-P and Red-Ti reduced the activity of CaS. Both the sulfur recovery performance of Red-FGD and Na2S in the presence of oxygen decreased comparing with the performance in the absence of oxygen while the decrease for Red-FGD was less than Na2S. Higher reaction temperature and lower space velocity could significantly enhance the sulfur recovery performance of Red-FGD. The sulfur recovery performance was very stable in the investigated NO concentration, i.e., 400-800 ppm. SEM photos indicated that some mesopores newly occurred in the reduction of the FGD particles but then the porosity decreased to some extent after the desulfurization.
Based on the results of a thermal equilibrium, temperature and velocity distributions of the waste heat boiler were simulated. Results show that the gas flow doesn’t rush to the top intensely when the first baffle-board is set in the front of the radiation chamber. Flue gas is so strongly disturbed by the second baffle-board that its residence time is increased. These two baffle-boards enhance the heat transfer intensity in the radiation chamber. The relative error of simulation results to experimental is less than 10%.
Over many decades, numerous feasibility studies have demonstrated, that the production of sulphuric acid remains the most viable option of sulphur recovery from smelter off gas and abatement of SO(2) emissions to the atmosphere. This is particularly more pronounced as smaller but more concentrated off-gas flows are to be treated from smelters, and enhanced sulphuric acid processes become available. Off-gas handling systems represent a significant capital and operating cost burden to the metallurgical operation. Modern pyrometallurgical smelter processes for sulphide ores based on the use of oxygen-enriched air, produce relatively small off-gas flows with high SO(2) concentrations in the smelter gas of 30-60%-vol. of SO(2). This is a prerequisite for substantial cost reductions in the smelter off-gas handling and treatment system. As an alternative to sulphuric acid production, numerous scrubbing concepts with alkali or dual-alkali combinations as well as organic absorbents have been proposed. Also the reduction of the SO(2) to elemental sulphur has frequently been studied. Very few of those alternative processes have been built in industrial scale, but all were generally characterized by none-sustainable operation due to cost reasons, problems with issues related to chemicals used and by-products or poor availability. Thus the traditional concept of converting the SO(2) to sulphuric acid is most common, although regarded as uneconomic, but is at least a proven, environmentally sustainable and reliable way of sulphur gas processing. With the high acid price levels these days, operating companies are even able to generate significant revenue with their otherwise 'fatal, acid. Even though smelter gas is available at high SO(2) concentrations, in a conventional acid plant one would add large amounts of air to dilute the gas down to a suitable concentration of 12-13 (14)%-vol. SO(2). Dealing with higher SO(2) concentrations in smelter acid plants is not feasible, as the gas exit temperature of the catalytic oxidation step would exceed the allowable limit for the catalyst. Hence those conventional acid plants are characterized by the use of large equipment, i.e. high capital cost, high energy consumption and limited flexibility. The newly developed LUREC (R) process can handle off-gas with significantly higher gas concentrations, even in excess of 25%-vol- SO(2). It is entirely based on well-proven equipment and unit operations. The first industrial application, operating with 16-18%-vol, SO(2) will be presented in this paper, along with the fundamentals of the process. it will be demonstrated that the process requires inherently lower capital cost, fewer operating costs, and offers better energy recovery and lower emis-sions as compared to conventional design. While most existing smelter acid plants would have some built-in spare capacity, any significant increase of smelter capacity, say of 30%, can basically not be accommodated without installing an additional parallel new acid plant unit. An add-on LUREC (R) module can remove any such restriction, while simultaneously debottlenecking the existing acid plant. The paper also discusses the present status of the add-on technology for smelter acid plant expansions with respect to technical boundary conditions of different process alternatives as well as economic and environmental aspects. Application of the LUREC (R) process to modern smelter acid plants operating with high SO(2) gas concentration, will lead to a substantial reduction of the specific size of the gas processing equipment and equivalent savings in capital and operating cost. The LUREC (R) process is patented worldwide by OUTOTEC.
Recovery of bismuth and arsenic from copper smelter flue dusts after copper and zinc extraction was carried out by a hydrometallurgical process. The dusts were leached with a H2SO4–NaCl solution and precipitating bismuth and arsenic in the liquor was performed. The precipitate was leached with a 2 M sodium hydroxide solution and the obtained residue and liquor were used for preparation of sponge bismuth and sodium arsenic, respectively. The process parameters were preliminarily optimized and under the optimal conditions, the total recoveries of bismuth and arsenic are 90% and 42%, respectively. The purity of obtained sponge bismuth can reach up to above 90% under the optimal conditions.
In continuation of a previous study on a catalyst containing potassium and vanadium oxides, it is shown that the oxidation of SO2 on a sodium-potassium-vanadium catalyst also proceeds via rapid establishment of the equilibrium, SO2 + 2V5+ + O2− SO3 + 2V4+ (equilibrium constant K) and that the reaction of oxygen with V4+ is the rate-determining step. On the basis of this finding it has been derived that the reaction rate can be formulated as follows By means of isothermal and differential kinetic measurements on both types of catalysts mentioned above this expression has been checked and found correct. The value of the equilibrium constant K calculated from the kinetic experiments is in good agreement with that derived from analytical determinations.
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