Desulfurization Process Research Articles

Ultrasound-assisted extractive-catalytic removal of micro-organic pollutants in liquid hydrocarbon fuels using highly active ZnO nanoparticles supported zinc-substituted phosphotungstate

To produce ultra-low sulfur diesel (ULSD), it is necessary to remove compounds such as 2-methylthiophene and 3-methylthiophene that cannot be isolated by conventional industrial methods. This paper presents, a phosphotungstate catalyst improved with zinc atoms placed on the surface of super active zinc oxide nanoparticles and is able to switch between two phases using a hydrophobic ionic liquid (transfer agent). Here, is a description of the synthesis of the α-keggin type hybrid nanocatalyst and its application for the removal of 2- methylthiophene and 3-methylthiophene. The nanocatalyst was subjected to various characterization techniques, including Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) Surface Area Analysis, Barrett-Joyner-Halenda (BJH) pore size and volume analysis and Energy-dispersive X-ray analysis(EDAX). The optimized conditions for the ultrasound-assisted extractive-catalytic oxidative desulfurization (UA-ECODS) process were determined using a statistical design, specifically the Box-Behnken design (BBD), which was proposed as a plan for designing experiments and studying the behavior of the parameters. The optimal conditions, which encompass four parameters, namely ultrasonic time, reactor temperature, amount of nanocatalyst, and oxidant concentration, are archived as 14.43 min, 40.52 °C, 86.27 mg catalyst, and 24 % H2O2 Respectively. The results indicated that the removal efficiency was higher for 2- methylthiophene than 3-methylthiophene. The paper concludes that the UA-ECODS method utilizing the synthesized nanocatalyst is a promising and effective approach for desulfurizing of liquid hydrocarbon fuels.

Mechanistic Evidence for Hg Removal from Wastewater by Biologically Produced Sulfur.

A significant quantity of biologically produced sulfur (BPS) is generated as a by-product of chemical and biological desulfurization processes applied to landfill gas treatment. The beneficial upcycling of BPS has seen limited use in the environmental context. The effectiveness and underlying mechanism of BPS as an adsorbent for removing Hg2+ from both solution and wastewater were elucidated based on experiments encompassing surface characterization, adsorption isotherms, kinetics, and thermodynamics. The BPS exhibited remarkable efficacy in removing Hg2+ from solution, with the Langmuir model accurately describing the adsorption process and showing a maximum adsorption capacity of 244 mg g-1. Surface analysis through X-ray photoelectron spectroscopy and scanning electron microscopy revealed that Hg2+ complexed with sulfide on BPS surfaces, forming stable HgS. The adsorbed Hg was strongly retained in BPS, with less than 0.2% of the adsorbed Hg desorbed by strong acids. Adsorption kinetics followed the double-exponential first-order model, showing an initial rapid adsorption phase wherein 75% of the initial Hg2+ was removed within 5 min, followed by a slower adsorption rate. The thermodynamic parameters suggested that adsorption of Hg2+ by BPS was a spontaneous and endothermic process. Additionally, BPS effectively removed Hg2+ from wastewater, showing preference for Hg over other co-existing metals. These findings underscore the potential of BPS as an effective adsorbent for Hg2+ removal from wastewater.

Desulphurisation of waste rubber powder using mechanochemical method and the influence on modified asphalt

The desulfurization treatments are vital for recycling waste rubber powder (WRP). The mechanochemical method accelerates desulfurization activation of additives, enhancing WRP's surface roughness and activity. This study employed mechanochemical desulfurization to produce desulfurized waste rubber powder (DWRP) modified asphalt. Variables like desulfurizer content, mixing temperature, and time were examined during the desulfurization process. Results revealed that organic disulfide (OGDS) had minimal impact on rubber's main chain but significantly affected sulfur cross-linked bonds. Optimal desulfurization conditions for OGDS were determined: 3.0% content, 140°C temperature, and 30 min mixing time. Scanning electron microscopy illustrated the destructive micromorphology of DWRP, featuring irregular surfaces with numerous holes or protrusions. DWRP-modified asphalt exhibited enhanced properties: a 44% increase in 5°C ductility, a 57% reduction in 180°C viscosity, and a 75% decrease in segregation softening point difference.

Study on dry desulfurization performance of modified HNTs

The production characteristics of coking industry determine that the coke quenching process has the characteristics of complex pollutant composition, high purification difficulty and serious environmental pollution. SO2 is one of the main pollutants in coke dry quenching tail gas, which is easy to cause serious harm. Dry desulfurization process is the use of particles or powder desulfurizer to remove SO2. The hydroxyl groups on the surface of Halloysite nanotubes make the active components of catalytic reaction fixed on the nano-scale surface or in the lumen, which can produce more selective and active catalytic materials with good catalytic performance. In this study, HNTs were modified by molten salt etching method. The functionalized halloysite and chitosan were cured by chemical precipitation method to prepare halloysite chitosan nanospheres desulfurizer, and its application performance and reaction mechanism in SO2 removal were explored.

New Approach for Sulfidation Process in Packed Bed with Hi-Fuel A310 Sorbent—Thermodynamical Studies

This paper presents tests related to the reactivity of commercial Hi-Fuel sorbent toward H2S (H2S/N2 mixture) in a packed bed at 300 °C. The sorbent used for breakthrough test was characterized before and after test by ESEM-EDX, FTIR-ATR, Raman, and elemental analyses. Testing reveals that the commercial sorbent contains two compounds reacting with H2S: ZnO and ZnCO3. According to thermodynamical studies, the reactivity of ZnCO3 at 300 °C is privileged (KR = 9.5 × 108) than ZnO (KR = 6.6× 106). In addition, the reaction of H2S with ZnCO3 induces a volume decrease, which promotes the movement of gas through the newly formed layer. The properties of this sorbent thus hold a good potential for the desulfurization process of gases polluted with H2S. We observed that the maximum sulfidation rate was reached on the surface of the sorbent and showed a maximum conversion of 27%.

New Composite Mesoporous Nano-Catalysts for Clean Fuel Produced by the Oxidative Desulfurization Process

New Composite Mesoporous Nano-Catalysts for Clean Fuel Produced by the Oxidative Desulfurization Process

Investigation of iron oxide supported on activated coke for catalytic reduction of sulfur dioxide by carbon monoxide

In view of the low utilization rate of by-product in limestone-gypsum wet flue gas desulfurization process, a method of catalytic reduction of SO2 to elemental sulfur was proposed. In this work, supported iron catalyst using activated coke as supporter was prepared and characterized. Moreover, the performance of SO2 reduction using CO as reducing agent at various Fe loadings, temperatures, gaseous hourly space velocities and CO/SO2 molar ratios was studied. Research shows that, compared with other metals, the highest catalytic activity is achieved over Fe-based catalyst. The iron sulfide is the main active component during the catalytic reduction reaction, hence the catalyst needs to be presulfided before use. The micropores of activated coke become more abundant after loading Fe, whereas excessive increase of Fe loading may bloke the mesopores and weaken the catalytic activity. Higher reaction temperature, lower GHSV and a stoichiometric molar ratio are conducive to the improvement of SO2 conversion and S yield. The catalytic performance at lower temperatures was further improved by loading Co. When the Co loading is 4 wt%, the SO2 conversion rate reaches 90.9% at 400 °C because loading Co enhances the redox performance of the catalyst surface. The findings are instructive for the development of cost-effective carbon-based catalysts for resource recovery of sulfur.

Aerobic Oxidative Desulfurization by Supported Polyoxometalate Ionic Liquid Hybrid Materials via Facile Ball Milling.

With the increasingly strict limitations on emission standards of vehicles, deep desulfurization in fuel is indispensable for social development worldwide. In this study, a series of hybrid materials based on SiO2-supported polyoxometalate ionic liquid were successfully prepared via a facile ball milling method and employed as catalysts in the aerobic oxidative desulfurization process. The composition and structure of prepared samples were studied by various techniques, including FT-IR, UV-vis DRS, wide-angle XRD, BET, XPS, and SEM images. The experimental results indicated that the synthesized polyoxometalate ionic liquids were successfully loaded on SiO2 with a highly uniform dispersion. The prepared catalyst (C16PMoV/10SiO2) exhibited good desulfurization activity on different sulfur compounds. Moreover, the oxidation product and active species in the ODS process were respectively investigated via GC-MS and ESR analysis, indicating that the catalyst can activate oxygen to superoxide radicals during the reaction to convert DBT to its corresponding sulfone in the fuel.

CATALYTIC ACTIVITY OF METAL-BASED IONIC LIQUIDS IN OXIDATIVE DESULFURIZATION

Effective desulfurization techniques are required due to the operational and environmental difficulties caused by sulfur compounds found in petroleum fuels. The use of Fenton catalysts in the oxidative desulfurization of petroleum fuels is examined in this work. Evaluating the viability and effectiveness of Fenton catalysts in lowering sulfur concentration while maintaining fuel quality is the main goal. Promising outcomes are found in laboratory tests using hydrogen peroxide (H2O₂) and ferrous iron (Fe³⁺) as catalysts. Fenton catalysts focus on sulfur compounds and transform them into forms that are soluble in water, making the process of separating them from the fuel easier. This procedure offers a more environmentally friendly and financially feasible desulfurization option because it works in milder circumstances than other techniques. The results provide a viable path for the development of sustainable fuel and have ramifications for greener energy sources and environmental legislation. There has been a growing interest in ionic liquids (ILs) as innovative materials for functional desulfurization. Based on their definition and fundamental structure, metal-based ionic liquids (MILs) are divided into three categories in this critical article: metal chloride MILs, metal oxide MILs, and metal complex MILs. To enhance the oxidative desulfurization (ODS) process, MILs have both the oxidation and absorption sites for intramolecular adsorption and oxidation. A noteworthy characteristic of MILs in ODS is biomimetic catalysis, which serves to enhance oxidation performance by triggering molecular oxygen. Hydrogen peroxide or oxygen combined with the available water, together with metal oxide and metal complex ions, create a Fenton-like reaction that transforms hydrophobic organic sulfur (SO2) or hydrophilic sulfoxide/sulfone (Seroxide), or sulfur acid, respectively. Promising approaches for developing environmentally friendly and highly effective desulfurization procedures for large-scale applications are also given. Keywords: supported ionic liquid catalyst (SILC), hydrogen peroxide, catalytic oxidative desulfurization, copper (I) chlorocomplexes.

Remarkable Catalytic Performance of MoO(O2)2 Loaded in NH2‐UiO‐66 for Oxidative Desulfurization of Fuel Oil

AbstractA highly efficient oxidative desulfurization composite catalyst NH2‐Uio‐66‐Mo has been prepared and applied in the catalytic oxidative desulfurization. It was elucidated that Mo6+ could increase the oxygen vacancies and active sites on the catalyst and increase the pore size of UiO‐66. Meanwhile, the removal rate of dibenzothiophene (DBT) reached 99.2 % after 60 min under optimal conditions and remained above 90 % after 5 cycles, showing the composite catalyst's remarkable catalytic performance and satisfactory reusability NH2‐UiO‐66‐Mo. In addition, kinetic studies revealed that the desulfurization process can present a pseudo‐first‐order kinetic process. The apparent activation energy was 10.6 kJ/mol. Finally, in combination with oxides, possible oxidation pathways were identified.

Peptide and Protein Desulfurization with Diboron Reagents.

In this Letter, we report a direct and robust desulfurization method employing water-soluble phosphine, specifically tris(2-carboxyethyl)phosphine hydrochloride (TCEP), and tetrahydroxydiboron (B2(OH)4), which serves as a radical initiator. This innovative reaction exhibits compatibility with a diverse array of substrates, including cysteine residues in chemically synthesized oligopeptides and cyclic peptides, alkyl thiols in bioactive molecules, disulfides in commercial proteins, and selenocysteine. We optimized the reaction conditions to minimize the formation of undesired oxidized and borylated byproducts. Furthermore, the refined desulfurization process is executed after native chemical ligation (NCL) in a single pot, streamlining the existing synthetic approaches. This demonstrates its potential applications in the synthesis of complex peptides and proteins, showcasing a significant advancement in the field.

Effects of Different CaO/Al2O3 Ratios on the Phase Composition and Desulfurization Ability of CaO-Based Desulfurizers in Hot Metal

In response to the development of low-carbon smelting technology, reducing the use of fluor-containing materials in desulfurizers is an important research topic. The development of new-generation KR (Kambara Reactor) desulfurizers is shifting towards a higher Al2O3 content rather than CaF2, yet there is currently an absence of thorough and comprehensive mechanisms for desulfurization. Consequently, this research provides an extensive comparison using a specially constructed small-scale KR desulfurization hot model test, alongside FactSage simulation and SEM analysis (of desulfurization process). The findings indicate that at 1400 °C, for the desulfurization of molten iron, the capacity for desulfurization initially increases and then diminishes as the Al2O3 content in the KR desulfurizer rises. With Al2O3 content in the desulfurizer below 22 wt.%, the phase composition predominantly consists of C3A, employing a solid(slag)–liquid(metal) diffusion method for desulfurization. The optimal desulfurization capacity (Ls: 64.1) is observed when the Al2O3 content is 15 wt.%, attributed to the simultaneous presence of CaO particle precipitation and C3A. However, as the Al2O3 content reaches 20 wt.%, all the oversaturated CaO integrates into C3A, leading to a reduction in Ls from 64.1 to 10.7, thereby diminishing the desulfurization capacity by approximately sixfold. When Al2O3 exceeds 22 wt.%, the phase composition transitions from the C3A to C12A7 phase, and the desulfurization approach shifts from solid(slag)–liquid(metal) to liquid(slag)–liquid(metal) diffusion, with Ls decreasing to 23.4. This reduction is due to C12A7’s lower sulfur capacity compared to C3A and the absence of saturated CaO particle precipitation. Therefore, for Al2O3 to effectively replace fluorite in KR desulfurizers, a higher presence of C3A phases and CaO particle precipitation are essential. The desulfurizer must contain over 65 wt.% CaO and maintain Al2O3 levels at 10~16.2 wt.%.

Process for desulfurization and demineralization of low rank coal using oxidation assisted froth floatation technique

This study reports the desulfurization and deashing of Hangu coal by air oxidation assisted froth floatation technique applying performic acid (H2O2+HCOOH) as co-oxidant and Fe ions as catalysts in aqueous solution. This process led to the removal of up to 78.08% of total sulfur (TS) and 50.3% of ash at 60 °C, 30 min, a 2:2 ratio of H2O2+HCOOH (v/v), and 0.10% of Fe ions concentration. The sulfur and ash removal followed Fenton mechanism, wherein hydrogen peroxide (H2O2) dissociated into hydroxyl ions (OH-) and hydroxyl radicals (OH.), facilitated by the dissociation of ferrous ions (Fe2+). The reaction of HCOOH with OH. resulted in the formation of performic acid or peroxyl radical, selectively oxidizing sulfur compounds to sulfone and sulfoxide. In the subsequent phase, coal froth floatation was employed with the addition of surfactant i.e. Triton X-100 (TX-100) and collector i.e. diesel oil (DO), resulting in the removal of up to 49.83% of TS and 43.79% of ash. This was achieved under optimized conditions, specifically with a concentration of 400 ppm solution of TX-100 in the solution and a volume of 0.2 mL for DO. The emulsion of TX-100 and DO for the floatation of coal is a suitable option because TX-100 established polar interactions and hydrogen bonding with the oxidized functionalities of coal, whereas the hydrocarbons of diesel oil get attached to the unoxidized coal matrix through hydrophobic interaction. Onwards, simultaneous oxidation assisted by froth floatation in a two-step batch process at pre-optimized parameters resulted in TS and ash removal of 88.8% and 82.6%, and 62.2% and 39.3% in the froth and tailings, respectively. SEM, FTIR and XRD analyses revealed structural and morphological changes, modifications in chemical functionalities and mineralogical changes in the coal sample. The process can be scaled up for the up-gradation of low grade coal for industrial and power generation purposes.

Tailoring Type III Porous Ionic Liquids for Enhanced Liquid-Liquid Two-Phase Catalysis.

Porous Ionic Liquids (PILs) have gained attention but facing challenges in catalysis, especially in liquid-liquid two-phase reactions due to limited catalytic sites and hydrophilicity control. This work engineered a Type III PILs (PILS-M) using zeolitic imidazolate framework-8 (ZIF-8) confined phosphomolybdic acid (HPMo) as the microporous framework and N-butyl pyridine bis(trifluoromethane sulfonyl) imide ionic liquid ([Bpy][NTf2]) as the solvent. The PILS-M not only combines the advantages of traditional ionic liquids and microporous frameworks, including excellent extraction, high dispersion of catalytically active species, remarkable stability, etc., but also can make the inner surface of ZIF-8 turned to be hydrophilic that favors the contact between aqueous hydrogen peroxide oxidant and catalytically active sites for the promotion of catalytic performance in reactive extractive desulfurization (REDS) processes of fuel oils. This study demonstrates Type III PILs' potential as catalysts for sustainable chemical processes, offering insights into versatile PILs applications in diverse fields.

ZIF-67-derived Co@NC as an efficient catalyst for magnesium sulfite oxidation in the flue gas desulfurization process

Magnesium desulfurization is a wet flue gas desulfurization (WFGD) technology widely used in China, however, the low oxidation rate of magnesium sulfite (MgSO3), a byproduct of WFGD, causes the subsequent oxidation and crystallization process to require amount energy. Here, we prepared a cobalt-based nitrogen-doped porous carbon catalyst (Co@NC) using ZIF-67 as a precursor for the efficient catalytic oxidation of MgSO3 generated during magnesium desulfurization. The performance of Co@NC catalysts obtained at an optimal calcination temperature of 650 °C showed that the catalysts with oxidation rates up to 0.1332 mmol·L−1·s−1 of MgSO3 were considerably better than those previously studied, which outperformed the catalysts described in earlier research by a considerable margin. Further studies revealed that the Co@NC’s exceptional catalytic activity was attributed to both its special porous structure and the exposed active Co sites in the organic skeleton. The uniformly dispersed Co species act as the active sites of the Co@NC that can be fully contacted with the reactant. The presence of 0.5 g·L−1 Co@NC increases the MgSO3 oxidation rate by about 14 times compared to the noncatalytic benchmark. A practical tactic is furnished by this research for energy saving and emission reduction in the WFGD process, especially for the efficient oxidation and resource conversion of the by-product MgSO3.

Solar-powered commercial diesel fuel desulfurization: Exploring the factors affecting and recyclability of mesoporous Tl-doped TiO2 nanofiber photocatalysts

The study aims to fabricate mesoporous TiO2 nanofibers (NFs) with different thallium (Tl) doping ratios (1–2 wt%) using the solution electrospinning method and examine their photocatalytic oxidation activity in the desulfurization of commercial diesel fuel. The results show that the Tl doping restricted the transition of the anatase to rutile fraction, shifting it from an initial composition of 58.3% rutile and 41.7% anatase to a significantly altered state with only 2.4% rutile and 97.6% anatase. Additionally, Tl-doping resulted in a decrease in crystalline size (from 55.4 to 9.5 nm), a reduction in the band gap from 3.2 to 2.93 eV, and a decrease in the diameter of the nanofibers from 200 nm to 100 nm, compared to pristine TiO2 NFs. The most efficient photocatalyst, 1 wt% Tl-doped TiO2 NFs, demonstrated remarkable performance with 98.74% sulphur removal under Xenon lamp irradiation (450 nm, 500 Watts) for 90 min. Under sunlight, the photocatalytic oxidation activity in the desulfurization process resulted in a remarkable reduction of 99.2% in sulphur content, decreasing from 11500 ppm to 98 ppm. Notably, this photocatalyst demonstrated efficient oxidative photocatalytic desulfurization and maintained the recyclability of the solvent over eight cycles without any loss.

A sustainable approach for recovering copper and zinc from copper smelting flue dust: Paving the path for waste reduction

The recovery of metals without generating secondary waste is a critical focus in the management of hazardous copper smelting dust. To tackle the challenges associated with arsenic-containing solid waste and waste acid generated by traditional recycling processes, we propose a two-stage roasting process that prioritizes low-temperature roasting for arsenic removal, followed by high-temperature roasting for desulfurization of sulfates. This work focuses on the high-temperature desulfurization behavior of residue after arsenic removal. The changes in composition during roasting were analyzed using TG-DSC, XRD, and SEM. The results revealed that the reaction temperature and the addition of bituminite are pivotal in the desulfurization process. The optimal roasting conditions were obtained to be a reaction temperature of 700 °C and a roasting duration of 3 h. Subsequently, approximately 98.77% of copper and 97.17% of zinc could be leached under conditions of a leaching temperature of 80 °C, a reaction time of 4 h, a sulfuric acid dosage of 3 times the theoretical amount, and a liquid-to-solid ratio of 10:1. This process mitigates the generation and accumulation of arsenic-containing waste acid during copper electrodeposition in the traditional hydrometallurgical process of copper smelting flue dust. It lays the foundation for clean and efficient recovery and also provides insights for recycling other copper-containing wastes.

Atmospheric SO2 pollutant prediction using mutual information based TCNN-GRU model for flue gas desulfurization process

Over the past several years, sulfur dioxide (SO2) has raised growing concern in China owing to its adverse impact on atmosphere and human respiratory system. The major contributor to SO2 emissions is flue gas generated by fossil-fired electricity-generating plants, and as a consequence diverse flue gas desulphurization (FGD) techniques are installed to abate SO2 emissions. However, the FGD is a dynamic process with serious nonlinearity and large time delay, making the FGD process modeling problem a formidable one. In our research study, a novel hybrid deep learning model with temporal convolution neural network (TCNN), gated recurrent unit (GRU) and mutual information (MI) technique is proposed to predict SO2 emissions in an FGD process. Among those technique, MI is applied to select variables that are best suited for SO2 emission prediction, while TCNN and GRU are innovatively integrated to capture dynamics of SO2 emission in the FGD process. A real FGD system in a power plant with a coal-fired unit of 1000 MW is used as a study case for SO2 emission prediction. Experimental results show that the proposed approach offers satisfactory performance in predicting SO2 emissions for the FGD process, and outperforms other contrastive predictive methods in terms of different performance indicators.

Hybrid modeling approach for natural gas desulfurization process: Coupling mechanism and data modeling via compact variable identification

The accurate process modelling in natural gas industry is beneficial for enterprises to increase potential profit and realize sustainable production. The integration of industrial data and first-principles computation is effective in hybrid process modelling. However, how to enhance their accuracy, robustness, and interpretability remains a challenge. Herein, a general framework integrating artificial intelligence algorithms and process mechanisms for natural gas desulfurization processes is proposed for accurate hybrid modelling. Firstly, the modelling is driven by the biased sulfur content target data generated by the mechanism model. Secondly, the general data information estimation of multivariate interaction and the independence test framework based on proxy data resampling are proposed based on the high-order information relationship. Then, based on Markov Blanket and causal feature selection principle, the compact variable recognition algorithm and the bias prediction model are further established. Finally, the industrial case of natural gas desulfurization is applied for method validation. On one hand, the prediction effect of the developed hybrid model (R2 0.9453, MAE 0.0982, MSE 0.0168, MAPE 0.03018) performs better than that of the mechanism model. On the other hand, it is indicated by the target deviation modelling that the proposed method can not only effectively reduce the excessive variables into 11 compact variables, which proves the effectiveness and accuracy of the proposed method, with the coefficient of determination R2 reaching 0.9152. Moreover, the rationality and interpretability of the proposed method is validated combining the process knowledge and some interpretability techniques. The contribution of this work is to provide an accurate, robust and interpretable method involving both process mechanism and realistic production data for the modelling for the natural gas industry.

Environmental compliance assessment for the desulfurization of sulfide mine waste tailings: A case study of Ok Tedi Mine, Papua New Guinea

The effective management of sulfide mine waste tailings is a complex task because of the potential for acid rock drainage to harm aquatic ecosystems. Although previous research has explored the environmental consequences of sulfide mine waste tailings and the potential advantages of desulfurization method, there is a lack of studies examining the environmental compliance of desulfurization efforts. To bridge this knowledge gap, a study was conducted at the Ok Ted Mine to evaluate the environmental compliance of the implemented desulfurization process. Ninety samples of sulfide tailing, desulfurized tailing, and sulfide concentrate were collected and analyzed for geochemical and physical properties. The acid-generating capacities were assessed using the Sobek's static test, whereas the particle size, pH, and recovery were evaluated for the overall performance of the desulfurization process. These findings indicated that the desulfurization process significantly reduced the acid-generating capacity and heavy metal concentrations of the sulfide tailings below the regulatory threshold levels. Therefore, the desulfurization approach employed at the Ok Ted Mine comply with the environmental regulaotry requirments. For further assessment, a study is recommended to evaluate the impact of desulfurization on the ecosystem to predict full extent of biodiversity recovery after mine life.