H2SO4 Production Research Articles

Green Synthesis of Sulphuric Acid Based on "Geber's Method": A Detailed Aspen Plus Simulation

Sulfuric acid (H2SO4) has a wide range of applications, but its current synthesis route via the contact process negatively impacts the atmospheric environment with harmful gaseous pollutants. Thus, based on the non-random two-liquids (NRTL) thermodynamic method, this study presents a detailed Aspen Plus V8.8 simulation of the green synthesis route of H2SO4 based on Geber's method developed already in the 18th century. The research investigates the efficiency and energy dynamics of the process through the analysis of key process parameters such as reactor's heat duty, vapor fraction, and molar extent of reaction in the selected configuration, using green vitriol (FeSO4∙7H2O) as a natural raw material. This study presented a novel manufacturing route that resulted in H2SO4 of 85.76% purity (33.71 kg/h), considering the chosen parameter space. The results highlight the impact of reactant component molar yield and fractional conversion of iron (II) sulfate (FeSO4) on heat duty and the optimal molar extent for maximizing H2SO4 production in a series of equilibrium reactors. In addition, appropriate operational parameters for the synthesis process were carefully specified, offering a pathway towards sustainable and eco-friendly H2SO4 production, which should emit zero greenhouse gases. Further optimization of the reactor conditions, can help maximize the yield of H2SO4, while minimizing energy consumption and byproduct formation. Developing advanced wastewater treatment units to purify the wastewater stream containing trace amounts of H2SO4 and dissolved sulfur trioxide (SO3) can mitigate environmental impact and ensure compliance with regulatory standards.

Experimental study and modelling of continuous SO2-depolarized electrolysis in hybrid sulfur cycle for hydrogen production

SO2-depolarized electrolysis (SDE) is the key process in the hybrid sulfur cycle for green hydrogen production, but the detailed SDE characteristics including products generation, current efficiency variation, and side reactions are unclear. Herein, a continuous SDE process was experimentally conducted and theoretically modelled. The H2 and H2SO4 production was accelerated and the current efficiency for both electrodes was improved with a proper increase in current density (50−100 mA/cm2) or temperature (293−318 K), but further increasing current density to 150 mA/cm2 or temperature to 333 K led to a negative trend because of the anode corrosion or declined SO2 solubility. The increasing initial H2SO4 concentration (10−40 wt%) facilitated the cathodic H2 production and current efficiency, while negatively influenced the anodic SO2 conversion. The parasitic reactions occurred at cathode consumed H2 and resulted to the cathodic current efficiency well below 100%. A rigorous mathematical regression model correlating the production rates of H2 and H2SO4 with current density, temperature, and initial H2SO4 concentration was developed, and combined with the analysis of variance, current density was suggested the biggest factor affecting products generation in SDE process. These findings demonstrate a practical avenue for efficient SO2 conversion and H2 production in SDE process of hybrid sulfur cycle.

Effect of industrial alkene ozonolysis on atmospheric H2SO4 formation

This study has employed the master chemical mechanism (MCM) to investigate the influence of the ozone oxidation pathways in the atmospheric formation of H2SO4 from short-chain olefins in industrialized areas. In-situ H2SO4 formation data were obtained using a high-resolution chemical ionization time-of-flight mass spectrometer, and the simulated H2SO4 concentrations calculated using updated parameters for the MCM model exhibited good agreement with observations. In the simulation analysis of different reaction pathways involved in H2SO4 formation, hydroxyl radicals were found to dominate H2SO4 production during the daytime, while olefin ozone oxidation contributed up to 65% of total H2SO4 production during the night-time. A sensitivity analysis of the H2SO4 production parameters has revealed a high sensitivity to changes in sulfur dioxide, and a relatively high sensitivity to olefins with fast ozonolysis reaction rates and bimolecular reaction rates of resulting stabilized Criegee Intermediates. A high relative humidity promotes daytime H2SO4 formation, but has an inhibiting effect during the night-time due to the different dominant reaction pathways.

Conversion of low-rank coal and sewage sludge into syngas for H2SO4 production and straw hydrolysis.

This study investigates the potential of using sewage sludge and low-rank coal for the sustainable production of sulfuric acid, which can then be used for the hydrolysis of straw through ASPEN PLUS simulation. Pyrolysis and gasification processes were used to convert sewage sludge and low-rank coal into syngas, which were then purified and oxidized to produce H2SO4 and NH3 gas. The pyro-gasification enhanced syngas yield. The effects of key process parameters such as temperature, steam-to-biomass ratio, equivalence ratio, and feedstock composition on the yield and composition of syngas and H2SO4 coupled with minor parameters like pressure were investigated. The simulation was conducted over the temperature and pressure range of 400 - 900°°C and 70 - 150kPa respectively. While the steam-to-biomass ratio and equivalence ratio were respectively varied from 0.66 - 1.65 and 0.14 - 0.35. Part of the 1012.88kg/h of H2SO4 produced was used to hydrolyze straw, producing glucose as a valuable feedstock for biorefineries. About 3989.10kg/h of NH3 was produced. Results showed that the use of sewage sludge and low-rank coal as feedstocks for syngas production can be a sustainable and cost-effective alternative to traditional fossil fuels. The resulting H2SO4 can also be used for various other applications, such as in the production of fertilizers and detergents. Overall, this study agrees with the literature, demonstrates the potential of integrating biomass and waste resources for the sustainable production of high-value chemicals and fuels, and contributes to the field of sustainable chemical and energy production while addressing environmental and economic considerations.

Surface‐Plasma Interactions at Europa in Draped Magnetospheric Fields: The Contribution of Energetic Electrons to Energy Deposition and Sputtering

AbstractWe calculate the time‐varying spatial distribution of energetic magnetospheric electron influx onto Europa's surface by combining a hybrid model of the moon's draped electromagnetic environment with a relativistic particle tracer. We generate maps of the energetic electron influx patterns at four distinct locations of Europa relative to the center of the Jovian magnetospheric current sheet. For a full synodic rotation of Jupiter, these results are applied to constrain the averaged number and energy influx patterns as well as the O2 sputtering rates associated with energetic electron precipitation. We also determine the relative contributions of magnetospheric ions and electrons to surface erosion and exospheric genesis at Europa. Our major results are: (a) Except for a small region near Europa's downstream apex, the moon's entire surface is exposed to heavy irradiation by magnetospheric electrons. (b) The spatial distribution of energetic electron influx onto Europa's surface is only slightly modified by field line draping and the induced magnetic field from the moon's subsurface ocean. (c) The contributions of magnetospheric electron and ion impacts to energy deposition onto Europa's surface are of the same order of magnitude. (d) Within uncertainties, impinging magnetospheric electrons and ions make similar contributions to O2 sputtering from Europa's surface. (e) The spatial distribution of electron energy influx and the observed concentrations of sulfuric acid (H2SO4) are only weakly correlated, suggesting that energy deposition by magnetospheric electron impacts is not a necessary agent for H2SO4 production within Europa's surface.

Optimized Production of High Purity Sulphuric Acid via Contact Process

Sulphuric acid (H2SO4) is of immense importance to the chemical industry and humanity. The use of Aspen Plus modeling, simulation, and optimization via the contact process has enabled the production of grade sulphuric acid. Notably, the research findings highlight the sensitivity of water flow rate to the maximization of H2SO4 production. Through these methods, a production capacity of around 8 tons per day was achieved, with a purity level of 98.9%. This achievement significantly contributes to meeting the demand for sulphuric acid in various industries. Moreover, exploring alternative sourcing methods, such as utilizing elemental sulphur, offers the potential for further optimizing H2SO4 production. The benefits of improving H2SO4 production extend beyond the chemical industry. Sulphuric acid finds applications in agriculture, petroleum refining, pharmaceuticals, and metal processing. Enhancing the production process ensures a reliable supply for these sectors. In summary, sulphuric acid is indispensable to the chemical industry and humanity at large. Aspen Plus modeling and optimization techniques have successfully improved the production of high-grade sulphuric acid, resulting in increased capacity and purity. Exploring alternative sourcing methods further enhances production possibilities. These advancements have wide-ranging implications, benefiting multiple industries and driving progress in sectors reliant on sulphuric acid.

Auto‐thermal chemical looping combustion of sulphur with Fe2O3 oxygen carriers for sulphuric acid production: Thermodynamics

AbstractChemical looping is a novel fuel conversion and material separation technology. It can be applied to obtain sulphur through selective oxidation of H2S. Further, chemical looping combustion (CLC) of sulphur can generate SO2 with a high concentration without NOx formation. The high SO2 concentration is adjustable and facilitates large‐scale H2SO4 production. In this study, we examined the thermodynamics of the CLC of sulphur for H2SO4 production, which has not been reported previously. We analyzed the effects of reactor temperature and sulphur to Fe2O3 oxygen carrier (OC) ratios on sulphur allotrope transformations and on the distributions of reaction products. Moreover, the reactors were operated auto‐thermally. Based on this design, we examined the effects of fuel reactor (FR) and air reactor temperatures on the minimum recirculation of the OC, as well as the gas and solid products and heat released from the air reactor. Our results showed that the CLC of sulphur with Fe2O3 OC could occur through an auto‐thermal process. The FR in a sulphur CLC system should be operated over a temperature range of 800–950°C, with an Fe2O3 OC recirculation between 45 and 143 kg/kgS(s). Furthermore, when the FR was operated in the auto‐thermal mode, we achieved 100% SO2 conversion. The findings of this study may be applied to reactor design for large‐scale H2SO4 production through CLC of sulphur.

High Gas-Phase Methanesulfonic Acid Production in the OH-Initiated Oxidation of Dimethyl Sulfide at Low Temperatures.

Dimethyl sulfide (DMS) influences climate via cloud condensation nuclei (CCN) formation resulting from its oxidation products (mainly methanesulfonic acid, MSA, and sulfuric acid, H2SO4). Despite their importance, accurate prediction of MSA and H2SO4 from DMS oxidation remains challenging. With comprehensive experiments carried out in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at CERN, we show that decreasing the temperature from +25 to −10 °C enhances the gas-phase MSA production by an order of magnitude from OH-initiated DMS oxidation, while H2SO4 production is modestly affected. This leads to a gas-phase H2SO4-to-MSA ratio (H2SO4/MSA) smaller than one at low temperatures, consistent with field observations in polar regions. With an updated DMS oxidation mechanism, we find that methanesulfinic acid, CH3S(O)OH, MSIA, forms large amounts of MSA. Overall, our results reveal that MSA yields are a factor of 2–10 higher than those predicted by the widely used Master Chemical Mechanism (MCMv3.3.1), and the NOx effect is less significant than that of temperature. Our updated mechanism explains the high MSA production rates observed in field observations, especially at low temperatures, thus, substantiating the greater importance of MSA in the natural sulfur cycle and natural CCN formation. Our mechanism will improve the interpretation of present-day and historical gas-phase H2SO4/MSA measurements.

V2O5/TiO2 acting as both oxygen carrier and catalyst for chemical looping oxidation of H2S at a low temperature

Chemical looping oxidization of H2S at a low reaction temperature was investigated. A V2O5/TiO2 oxygen carrier produced by sol–gel method was employed, and experiments were performed in a fixed bed. Effects of reaction temperature (150-250℃), H2S inlet concentration (1000–4000 ppm) and cycles on H2S conversion behavior were investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the oxygen carrier property. Finally, the S conversion pattern and role of oxygen carrier during the proposed chemical looping route were identified. Thermodynamic analysis and experimental results confirmed the proposed elementary sulfur production during reduction stage and a significant SO2 production during oxidization stage. Experimental results confirmed the proposed elementary sulfur production during reduction stage and a significant SO2 production during oxidization stage. At 150 ℃, the selectivity of SO2 during reduction stage is less than 5%, and the fraction of the converted H2S to S is higher than 95% in the present condition. XRD and XPS results supported that V5+(V2O5) was reduced to V4+(VO2) by the continuous feeding H2S. During oxidization stage, the V2O5/TiO2 material acted as both oxygen carrier and catalyst to produce SO2 for further H2SO4 production.

Experimental and simulation assessment to mitigate the emission of sulfide toxic gases and removing main impurities from Zn + Pb + Cu recovery plants

Abstract An integrated novel approach employing the Taguchi method and Aspen Plus software has been applied to evaluate a new configuration for the industrial process of Zn + Pb + Cu recovery from sphalerite ore, in order to minimize the toxic gas emission. The optimum operating condition achieved by the Taguchi method has been used as initial data for the process simulation. The impact of operating parameters on the process performance is considered. The optimum condition for the conversion of sulfide toxic gases to H2SO4 have been found to be: acid concentration of 0.867 mol/L, reaction temperature of 120 °C, stirring speed of 400 rpm, leaching time of 120 min, sulfide ore particle size of 0.01 mm; solid-to-liquid ratio of 30 wt%, additives amount of 50 kg/ton and oxygen pressure of 200 psi. Under optimum condition, H2SO4 production from sulfide toxic gases is 99%, the removal percentage of Fe, Co, Mn, Ni and Cd impurities is 99% and the recovery percentage of Zn + Pd + Cu is more than 97%.

Characterization of PBI/Graphene Oxide Composite Membranes for the SO2 Depolarized Electrolysis at High Temperature

In this work, polybenzimidazole (PBI) membranes with different graphene oxide (GO) contents (0.5, 1.0, 2.0, and 3.0 wt %) as organic filler have been prepared. The X-ray diffraction confirms the incorporation of the filler into the polymeric membrane. The composite GO-based PBI membranes show better proton conductivity at high temperature (110–170 °C) than the pristine one. Moreover, the hydrophobicity of the PBI membranes is also improved, enhancing water management. The chemical stability demonstrates the benefit of the incorporation of GO in the PBI matrix. What is more, the composite PBI-based membranes show better phosphoric acid retention capability. For the first time, the results of the SO2-depolarized electrolysis for hydrogen production at high temperature (130 °C) using phosphoric acid-doped polybenzimidazole (PBI) membranes with the different GO contents are shown. The benefit of the organic filler is demonstrated, as H2SO4 production is 1.5 times higher when the membrane with a content of 1 wt % of GO is used. Moreover, three times more hydrogen is produced with the membrane containing 2 wt % of GO compared with the non-modified membrane. The obtained results are very promising and provide open research for this kind of composite membranes for green hydrogen production by the Westinghouse cycle.

Research on possible sulfuric acid (H2SO4) production using sulfur/sulfur-containing feedstocks from Dung Quat refinery

This paper analyses the possibility for H2SO4 production using sulfur/sulfur-containing feedstocks from Dung Quat Refinery in terms of market, technology and economic efficiency. Domestic production of H2SO4 currently does not meet the domestic demand, the shortfall must therefore be compensated by imports. It is forecast that the domestic market will lack about 464 thousand tons of H2SO4 by 2025. The H2SO4 production project with a capacity of 200 thousand tons per year is proposed to go into operation in 2025. In the case of indirect production of H2SO4 from H2S rich gas through the intermediate sulfur product, the project has an estimated total investment cost of USD 143.2 million, its IRR will be around 3.2%, its NPV@13.2% will be USD 55.1 million and the total payback period will be 14 years and 4 months. In case of using H2S rich gas directly as feedstock, the project has an estimated total investment cost of USD 102.4 million, its IRR will be around 16.3%, its NPV@13.2% will be USD 15.7 million and the total payback period will be 5 years and 5 months.

Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

Abstract. Reaction of stabilized Criegee intermediates (SCIs) with SO2 was proposed as an additional pathway of gaseous sulfuric acid (H2SO4) formation in the atmosphere, supplementary to the conventional mechanism of H2SO4 production by oxidation of SO2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in H2SO4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase H2SO4, OH radicals, SO2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of H2SO4 via SO2 oxidation by the SCIs. Assuming the validity of a steady state between H2SO4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the H2SO4 formation during the day could be explained by the reaction of SO2 with OH. During the night the oxidation of SO2 by OH radicals was found to contribute only about 10 % to the H2SO4 formation. The accuracy of the derived values for the contribution of OH + SO2 reaction to the H2SO4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH + SO2 reaction rate coefficient. The contribution of the SO2 oxidation by SCIs to the H2SO4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). The estimated concentration of the sum of SCIs was in the range of (1–3) × 103 molec. cm−3. During the day the reaction of SCIs with SO2 was found to account for about 10 % and during the night for about 40 % of the H2SO4 production, closing the H2SO4 budget during the day but leaving unexplained about 50 % of the H2SO4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SO2 oxidation by SCIs may represent an important H2SO4 source in VOC-rich environments, especially during nighttime.

Resource utilization of natural pyrite (FeS2) as the tailings after flotation of natural sphalerite (ZnS) for reclaiming high concentrations of gaseous Hg0 from Zn smelting flue gas

Reducing Hg emissions from Zn smelting flue gas (Zn-SFG) is rigorously stipulated by the Minamata Convention. Currently, a little natural pyrite (FeS2) as the tailings after flotation of natural sphalerite (ZnS) is often regarded as solid wastes and discarded; therefore, another utilization of these natural FeS2 is preferable. In this study, magnetic pyrrhotite (Fe1-xS), formed by heat treatment of natural FeS2, was exploited to reclaim gaseous Hg0 from Zn-SFG. Magnetic Fe1-xS displayed outstanding ability to capture gaseous Hg0 due to the formation of surface new unsaturation coordination sites for gaseous Hg0 physical adsorption. Additionally, magnetic Fe1-xS can be separated magnetically from Zn-SFG after gaseous Hg0 capture owing to its acceptable magnetism. Furthermore, both the abundant S resources emitted from the transformation of natural FeS2 to magnetic Fe1-xS and those in magnetic Fe1-xS after gaseous Hg0 capture can be used for H2SO4 production. Moreover, the vast majority of gaseous Hg0 in Zn-SFG can be ultimately reclaimed as liquid Hg0 by the condensation unit in Zn smelteries. Therefore, magnetic Fe1-xS offered unparalleled advantages in gaseous Hg0 recovery from Zn-SFG, double as a feasible method for fully exploiting the resource utilization value of natural FeS2 as the tailings after flotation of natural ZnS.

Metal extraction from spent lithium-ion batteries (LIBs) at high pulp density by environmentally friendly bioleaching process

Spent lithium-ion batteries (LIBs) are more hazardous due to the presence of several toxic metals such as cobalt, lithium, nickel, manganese, etc. as well as electrolytes such as LiPF6, LiBF4, or LiClO4. However, these spent LIBs are the secondary source of metals that can be extracted and reused in many ways to decrease their potential environmental risks. Metal extraction from the mixture of LiCoO2-based spent LIBs at a high pulp density by bioleaching is challenging because of microbial inhibition due to high metal toxicity and substrate (iron) limitation. In the present study, we have investigated the bioleaching of a mixture of LiCoO2-based LIBs at high pulp density (100 g/L) using cost-efficient autotrophic bacteria Acidithiobacillus ferrooxidans. By increasing the biogenic H2SO4 production in the culture media, as well as replenishing the bacterial culture for three cycles, we could recover 94% cobalt and 60% lithium in 72 h at 100 g/L pulp density. The X-ray diffraction (XRD), Scanning electron microscope (SEM), and Inductively coupled plasma - optical emission spectrometry (ICP-OES) analysis of LIB powder before and after bioleaching confirmed that more than 90% cobalt leached out from the LIB powder. This bioleaching process is an environmentally friendly way of extracting metals from the mixture of LIBs in gadgets and can be used for all types of spent LIBs.

Aerosols in the E3SM Version 1: New Developments and Their Impacts on Radiative Forcing

AbstractThe new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department of Energy has significant new treatments of aerosols and light‐absorbing snow impurities as well as their interactions with clouds and radiation. This study describes seven sets of new aerosol‐related treatments (involving emissions, new particle formation, aerosol transport, wet scavenging and resuspension, and snow radiative transfer) and examines how they affect global aerosols and radiative forcing in E3SMv1. Altogether, they give a reduced total aerosol radiative forcing (−1.6 W/m2) and sensitivity in cloud liquid water to aerosols, but an increased sensitivity in cloud droplet size to aerosols. A new approach for H2SO4 production and loss largely reduces a low bias in small particles concentrations and leads to substantial increases in cloud condensation nuclei concentrations and cloud radiative cooling. Emitting secondary organic aerosol precursor gases from elevated sources increases the column burden of secondary organic aerosol, contributing substantially to global clear‐sky aerosol radiative cooling (−0.15 out of −0.5 W/m2). A new treatment of aerosol resuspension from evaporating precipitation, developed to remedy two shortcomings of the original treatment, produces a modest reduction in aerosols and cloud droplets; its impact depends strongly on the model physics and is much stronger in E3SM Version 0. New treatments of the mixing state and optical properties of snow impurities and snow grains introduce a positive present‐day shortwave radiative forcing (0.26 W/m2), but changes in aerosol transport and wet removal processes also affect the concentration and radiative forcing of light‐absorbing impurities in snow/ice.

Efficient and industrial production of H2SO4 from sulfur sludge by acidophilic cells in a membrane bioreactor via optimizing process

A large amount of sulfur-bearing hazardous wastes, including sulfur sludge, are generated in the production and processing of oil/natural gas/coal gas/biomass gas, which are difficult to dispose of with traditional processes, such as incineration or landfills. In the present work, a homemade membrane bioreactor (MBR) with an efficient volume of 10 m3 was utilized to continuously and efficiently remove sulfur (S0) from sulfur sludge and produce sulfuric acid (H2SO4) by using chemoautotrophic acidophilic cells on an industrial scale for the first time. The bio-oxidation process was also modelled and optimized by using response surface methodology. The quadratic models describe the causal relationships between the production rate of H2SO4 at pH 1.0 or the time required for the pH to decrease to 1.0 and three important control parameters (temperature, aeration rate and stirring velocity). The MBR maintained high-density growth of cells (≈2.1 × 109/mL) throughout the entire operational period due to the excellent interception performance, establishing a basis for efficient sulfur removal and H2SO4 production. Under the optimized process controls of 33.6 °C for the temperature, 3.1 m3/min for the aeration rate and 83 rpm for the stirring velocity, a high production efficiency of H2SO4 at pH 1.0 (≈850 L/h) is obtained. Accordingly, the sulfur removal efficiency and sulfur residual concentrations reached 93% and 4.1% after 20 days of contact, respectively. The current study demonstrates that the MBR is suitable for industrial scale operations, for continuous and efficient sulfur removal and for production of H2SO4 from sulfur-bearing hazardous wastes. The green microbial means not only save very expensive disposal expense of sulfur-bearing hazardous wastes but also gain benefits through the manufacture of valuable H2SO4, displaying great business value and wide application prospect.

Remediation of Black Sea ecosystem and pure H2 generation via H2S-H2O co-electrolysis in a proton-conducting membrane cell stack reactor: A feasibility study of the integrated and autonomous approach

Abstract The present work explores the feasibility of an integrated and autonomous scaled up process towards the remediation of the Black Sea ecosystem with simultaneous H2 generation through the co-electrolysis of rich H2S/H2O seawater mixtures. The core unit of the proposed process is a proton-conducting membrane cell stack reactor (electrolyzer), where H2S in excess H2O mixtures are fed at the anode and co-electrolyzed to protons (H+), which are transferred through the electrolyte to the inert exposed cathode towards H2 generation. The proposed scaled-up process aims towards a Black Sea water intake of up to 2000 tn/hr and involves four distinct operating steps, i.e.: i) pumping Black Sea water from 1 km depth (H2S∼14 ppm) and H2S concentration enrichment up to 1 v/v% H2S-H2O, ii) Η2 production through H2S-H2O co-electrolysis at 850 °C and 2 bar, iii) purification and separation of the proton-conducting electrochemical membrane reactor effluent (H2 and SO2) and iv) H2SO4 production from off-gases. Overall heat management is accomplished through a natural gas high pressure burner along with flue gas power recovery (combined cycle) and the process system is assessed in terms of operating flexibility, electrical/heat requirements and economic perspectives. As was revealed, the decreased concentration of H2S/H2O mixtures (from 1 to 0.1 v/v%) results in a higher H2 and H2SO4 generation at the expense of higher heating/electrical demands, whereas the variation on the Black Sea water intake (from 650 to 1950 tn/hr) can be appropriately adjusted to regulate the corresponding operating costs. Based on a parametric sensitivity analysis, it was revealed that a H2S concentration of 1 v/v% and a water intake flow corresponding to a hydrogen production of >40 kg/h can promise favorable financial perspectives. The minimum products sale values that ensure the feasibility of the process along with a flexible heat and energy autonomy were identified at 9.85 €/kg of H2, 0.45 €/kg of H2SO4 and 0.277 €/kWh of produced electricity. Partial subsidy on the total fixed capital investment can further result in a substantial improvement of the investment's operating profitability.

A quantitative approach to the influence of pyrite separation on Cu-processing tailings: a case study at Reps, Mirdita district, Albania

Sulfide-rich tailings are a well-known environmental threat due to their production of acid drainage (AD) and release of potential toxic elements (PTE) to the local environment. The presence of heterogeneous materials produces complex environmental signatures and complicates the quantitative prediction of contamination. The present work provides a method of quantifying such heterogeneities, starting from mineral processing data of the Reps, Mirdita (Albania) site. A quantitative flow sheet (QF) method was applied to a selected dump site of the Mirdita copper mining district where secondary pyrite separation had been used in the past. The site is subject to long-lasting (103 years) AD processes with significant release of PTE into the local environment. The tailings at the Reps site are divided into two classes based on the sulfide S content, respectively, represented by high-sulfide-content (S > 10 wt%) materials (hS) and low-sulfide-content (S < 3 wt%) material (lS). The reconstruction of the QF allowed us to identify the hS tailings as the discharge of single-flotation processing lines. This material accounts for about 82% of the total potential H2SO4 production, even though it represents < 20% of the entire tailing discard. The QF is a useful tool for the evaluation of heterogeneity and consequently for the modeling of waste management within abandoned sites and in working plants. Given a good quantification, heterogeneity can in fact support the setting of pyrite separation lines or the separate management of pyrite-rich tailing dumps.

Sulphuric acid production via Chemical Looping Combustion of elemental sulphur

A relevant objective of the sulphuric acid (H2SO4) production industry today is to obtain sulphur dioxide (SO2) gas streams with the highest possible SO2 concentration after the elemental sulphur combustion stage in order to reduce both capital and operating costs. A new technology, Chemical Looping Combustion (CLC), is able to generate gaseous streams that are highly concentrated in combustion products by means of oxygen transfer from air to the fuel using a solid oxygen carrier. This work proposes a new process for H2SO4 production via CLC and using elemental sulphur as fuel. An oxygen carrier with high sulphur resistance should be used for this purpose. The analysis of this process has brought promising results, such as the easy integration of the CLC system into the entire H2SO4 production plant and the confirmation that this is a process in which the energy potential of sulphur is exploited to a very high degree. Furthermore, the proof of concept was carried out by burning elemental sulphur in a 500Wth CLC unit with a high sulphur-resistant oxygen carrier based on iron oxide, Fe20γAl. This work presents the first ever results of elemental sulphur combustion by an oxygen carrier. Complete combustion of sulphur to SO2 was achieved, and no deactivation of the oxygen carrier was observed. Considering all the results obtained in this work, it can be concluded that the production of H2SO4 via CLC is a feasible technology which can provide a series of relevant techno-economic benefits in comparison with current industrial production process.