Sulfur Recovery Research Articles

Use of La-Co@NPC for Sulfite Oxidation and Arsenic Detoxification Removal for High-Quality Sulfur Resources Recovery in Desulfurization Process.

Ammonia desulfurization is a typical resource-recovery-type wet desulfurization process that is widely used in coal-fired industrial boilers. However, the sulfur recovery is limited by the low oxidation rate of byproduct (ammonium sulfite), leading to secondary SO2 pollution due to its easy decomposability. In addition, the high toxic arsenic trace substances coexisting in desulfurization liquids also reduce the quality of the final sulfate product, facing with high environmental toxicity. In this study, nitrogen-doped porous carbon coembedded with lanthanum and cobalt (La-Co@NPC) was fabricated with heterologous catalytic active sites (Co0) and adsorption sites (LaOCl) to achieve sulfite oxidation and the efficient removal of high toxic trace arsenic for the recovery of high-value ammonium sulfate from the desulfurization liquid. The La-Co@NPC/S(IV) catalytic system can generate numerous strongly oxidizing free radicals (·SO5- and ·O2-) for the sulfite oxidation on the Co0 site, as well as oxidative detoxification of As(III) into As(V). Subsequently, arsenic can be removed through chemical adsorption on LaOCl adsorption sites. By using the dual-functional La-Co@NPC at a concentration of 0.25 g/L, the rate of ammonium sulfite oxidation reached 0.107 mmol/L·s-1, the arsenic (1 mg/L) removal efficiency reached 92%, and the maximum adsorption capacity of As reached up to 123 mg/g. This study can give certain guiding significance to the functional material design and the coordinated control of multiple coal-fired pollutants in desulfurization for high-value recovery of sulfur resources.

Comparison of oxidation absorption and reduction absorption process for sulfur recovery tail gas treatment of natural gas treatment plants in China Part Ⅰ: Technical section

BackgroundChina's newest SO2 emission policy for the natural gas industry forced natural gas treatment plant to add sulfur recovery tail gas treatment unit. In this context, the oxidation absorption process has been applied for the first time in Sichuan Basin. However, the advantages and disadvantages of this process compared with the traditional reduction absorption process have not been reported. MethodsThe two processes were compared from the technical angle in this paper. The data of one plant in Sichuan Basin was selected as the simulation condition. Significant findingsThe calculation results showed good agreement with plants data. The solution circulation amount of oxidation absorption process were 19 and 18.52 m3/h, which were just 20 %∼25 % of that for reduction absorption process. Meanwhile the acid gas returned amount was only about 14 % of reduction absorption process. However, the main process gas flow was 1.5 times of reduction absorption process. Regarding the utility consumptions, the oxidation absorption process had more advantages in electricity consumption, but it was inferior in fuel gas and circulating water consumption.

(Electro)catalytic oxidation of sulfide and recovery of elemental sulfur from sulfide-laden streams

MnxOy coated over TiO2 nanotube array substrate was doped with Mo and polyaniline (PANI) and applied for electrochemical desulfurization of concentrated sulfide (HS−) solutions at basic pH, typical of biogas scrubbing solutions and industrial wastewater. Mo and PANI co-dopants significantly enhanced the anode activity towards sulfide oxidation and ensured its complete stability even in highly corrosive sulfide solutions (e.g., 200 mM HS−). This was due to the increased electrochemically active surface area, improved coating conductivity and reduced charge transfer resistance. The (electro)catalytic oxidation of HS− demonstrated robust performance with very limited impact of different operational parameters (e.g., dissolved oxygen, anode potential, HS− concentration). Due to the formation of elemental sulfur (S0) layer at the anode surface at basic pH, longer term anode usage requires its periodic removal. Chemical dissolution of S0 with toluene allows its rapid removal without affecting the anode activity, and easy recrystallization and recovery of pure sulfur.

Simulation and multi-objective optimization of Claus process of sulfur recovery unit

Although natural gas can provide energy with minimum greenhouse gas emissions compared to other fossil-derived fuels, the sulfur removal is the major challenge associated with its use in various applications. In this work, sulfur recovery unit was simulated using the Aspen HYSYS. The environmental, energy, and economic analyses of the process based on special criteria (profit (PBT), weighted global warming potentials (WGWP), and energy consumption (NQ)) were analyzed. After consideration of the sensitivity analysis of the process, the single and multi-objective optimizations were carried out by integrating the HYSYS simulations with MATLAB codes with the Genetic Algorithm method. Feed temperature, feed molar flow rate, combustion air temperature, and reboiler temperature are decision variables in this work. The results show that with increasing the feed temperature, the energy consumption decreases, so, the cost of energy decreases. Also, with increasing the feed temperature, and reduction of consumed energy, the equivalent CO2 emission (which is calculated based on total energy consumption) reduces, so, WGWP decreases. Maximization of PBT, Minimization of WGWP, and Minimization of NQ were considered as the single objective optimizations, separately. Optimum values of decision variables were found. For multi-objective optimization, three different cases were considered: Case 1 (Max. PBT and Min. WGWP), Case 2 (Max. PBT and Min. NQ), Case 3 (Min. WGWP and Min. NQ). In all these cases, it can be found Pareto optimal frontier. The results show that the feed molar flow rate and air combustion temperature variables have more effect than other variables.

Enhancement of anaerobic ammonia oxidation process composed of mixed sludge without additional deoxidation by sulfur autotrophic denitrification under mainstream conditions

The practical application of anaerobic ammonia oxidation (anammox) process is hindered because of its strict demand of an anaerobic environment. Due to the slow growth cycle of anammox bacteria and the high cost of wastewater deoxidation, it is difficult to improve the contribution rate of denitrification in anammox pathway. Sulfur oxidizing bacteria (SOB) consume oxygen in the process of oxidizing sulfur elements to provide a better anaerobic environment for anammox bacteria, and sulfur autotrophic denitrification can also remove nitrate produced during the anammox process for deep nitrogen removal. The analysis of cell hydrophobicity and EPS secondary structure were consistent, which showed that the biofilm of A-SAD (anammox- sulfur autotrophic denitrification) system exhibited stronger adhesion and a more stable structure. The functional genes of ammonia oxidation (amoA) and nitrite oxidation (nxrA) were reduced by more than 90 %, implying that SAD provided a favorable anaerobic environment for anammox and reduced the cost of deoxidation in actual operation. The relative abundance of Candidatus_Kuenenia increased nearly threefold, becoming the dominant anammox bacteria in low substrate environment, while other anammox bacteria almost disappeared. The increase of the relative abundance of Thiobacillus and Desulfovibrio were beneficial to the transformation of S0 into bio-sulfur (Bio-S0) through redox, which provided the possibility for the recovery and utilization of sulfur. This experiment provides a comprehensive understanding of the nitrogen and sulfur conversion mechanism for the deoxidation and sulfur recovery of anammox in practical applications.

Neural Correlates of Object-Extracted Relative Clause Processing Across English and Chinese

Abstract Are the brain bases of language comprehension the same across all human languages, or do these bases vary in a way that corresponds to differences in linguistic typology? English and Mandarin Chinese attest such a typological difference in the domain of relative clauses. Using functional magnetic resonance imaging with English and Chinese participants, who listened to the same translation-equivalent story, we analyzed neuroimages time aligned to object-extracted relative clauses in both languages. In a general linear model analysis of these naturalistic data, comprehension was selectively associated with increased hemodynamic activity in left posterior temporal lobe, angular gyrus, inferior frontal gyrus, precuneus, and posterior cingulate cortex in both languages. This result suggests the processing of object-extracted relative clauses is subserved by a common collection of brain regions, regardless of typology. However, there were also regions that were activated uniquely in our Chinese participants albeit not to a significantly greater degree. These were in the temporal lobe. These Chinese-specific results could reflect structural ambiguity-resolution work that must be done in Chinese but not English object-extracted relative clauses.

A study on the activity recovery behavior of noble metal catalysts against sulfur poisoning

Various noble metals (Pt, Rh, Ru, and Pd) were supported on CeO2 to understand their sulfur-tolerant catalytic activity. The synthesized catalysts were applied to the water-gas shift reaction in the waste-to-hydrogen process with the injection of 500 ppm H2S. Among the samples, the PtCe catalyst showed the highest sulfur tolerance and recovery of catalytic activity. Considering the catalytic reaction results and physicochemical properties, the sulfur tolerance of the catalyst is affected by oxygen vacancies and redox properties, which are closely related to the interaction between the metal and the CeO2 support. In addition, the oxygen storage capacity concentration was used as an indicator for classifying the recovered catalyst and the non-recovered catalyst which had been poisoned by sulfur.

Investigation of oxy-fuel combustion for methane and acid gas in a diffusion flame

Co-combustion of methane (CH4) and acid gas (AG) is required to sustain the temperature in Claus reaction furnace. In this study, oxy-fuel combustion of methane and acid gas has been experimentally studied in a diffusion flame. Three equivalence ratios (ER = 1.0, 1.5, 2.0) and CH4-addition ratios (CH4/AG = 0.3, 0.5, 0.7) were examined and the flame was interpreted by analyzing the distributions of the temperature and species concentration along central axial. CH4-AG diffusion flame could be classified into three sections namely initial reaction, oxidation and complex reaction sections. Competitive oxidation of CH4 and H2S was noted in the first section wherein H2S was preferred and both were mainly proceeding decomposition and partial oxidation. SO2 was formed at oxidation section together with obvious presence of H2 and CO. However, H2 and CO were inclined to be sustained under fuel rich condition in the complex reaction section. Reducing ER and increasing CH4/AG contributed to higher temperature, H2S and CH4 oxidation and CO2 reactivity. Hence a growing trend for CH4 and AG to convert into H2, CO and SO2 could be witnessed. And this factor enhanced the generation of CS2 and COS in the flame inner core by interactions of CH4 and CO2 with sulfur species. COS was formed through the interactions of CO and CO2 with sulfur species. The CS2 production directly relied on reaction of CH4 with sulfur species. The concentration of COS was greater than CS2 since CS2 was probably inhibited due to the presence of H2. COS and CS2 could be consumed by further oxidation or other complex reactions.

Electrochemical Hydrogen Sulfide Decomposition Using Proton Conducting Ceramic for Pure Hydrogen Production

Hydrogen sulfide (H2S) is a substance that occurs during the process of processing sulfur, which is abundant in fossil fuels such as oil and natural gas, into high-quality fuel. Due to its high toxicity, it is classified as harmful industrial waste and removal in the process of discharging is essential. Until now, refiners have used the Claus process and the Wet Sulfuric Acid (WSA) process, which reacts hydrogen sulfide with oxygen to release it in the form of water or sulfuric acid. These processes require a huge amount of heat energy and only aim to remove hydrogen sulfide, so they emit hydrogen atoms contained in hydrogen sulfide in the form of water and sulfuric acid. Because hydrogen is an eco-friendly energy source that has recently been in the spotlight, hydrogen sulfide can be a valuable resource if hydrogen can be extracted from hydrogen sulfide. In this study, an electrochemical process that decomposes hydrogen sulfide and obtains hydrogen from hydrogen sulfide, replacing the conventional hydrogen sulfide removal process was proposed. To achieve this goal, thermodynamics of this reaction was analyzed and a solid oxide electrochemical cell based on proton conducting ceramic was fabricated for operating at high temperature and using perovskite structured electrodes. Experiments were then conducted to decompose hydrogen sulfide using fabricated cells and found that about 40 ppm, 100 sccm of hydrogen sulfide was decomposed at 600 oC by applying 0.5 V, 0.57 mA/cm2. Through this, the feasibility of the process was confirmed, and the durability test and regeneration process of the anode electrode were proceeded to solve degradation caused by sulfur deposits. In this study, a process has been proposed to effectively produce hydrogen of high value as an energy source, as well as to remove industrial waste hydrogen sulfide. It is expected that waste disposal and energy source production can be simultaneously produced in a clean and efficient way if cell performance improvement, removal of sulfur poison, and large systemization are applied to oil refiners' processes.

Динамика кислотно-щелочных и окислительно-восстановительных условий в аллювиальных техногенно засоленных почвах таежно-лесной зоны

The alluvial technogenically saline soils on the territory of the Verkhnekamsk salt deposit in the Perm Region were examined. It was found that in the studied part of the valleys of small rivers, alluvial saline soils occupy tens of hectares. During the summer-autumn observation period in alluvial humus gley saline saturated soil (Gleyic Fluvisol (Loamic, Salic)) at a depth of 10-40 cm, reducing conditions prevailed (Eh from +200 mV to -250 mV), favoring the biochemical recovery of iron and sulfur. The reaction of the soil medium ranged from 6,5–7,8 pH. In alluvial gley salt marsh unsaturated soils during the summer-autumn period in a layer of 10-40 cm, an alternation of anaerobic and aerobic conditions (Eh from -50 mV to +550 mV) was noted; the reaction of the soil medium at a depth of about 10-20 cm ranged from 2,5–4,1 pH. The regression dependence of pH on the value of Eh has been established with a correlation coefficient of R = -0,84. Apparently, technogenically saline alluvial soils have the potential for the formation of sulfide compounds and their subsequent oxidation with the appearance of a sharp acid reaction of the soil medium. Keywords: TECHNOGENIC SALINIZATION, EH, PH, GLEYIC FLUVISOL (LOAMIC, SALIC)

Direct decomposition of hydrogen sulfide through microwave-induced discharge of graphitized bio-char

Direct decomposition of hydrogen sulfide (H2S) can be used to obtain high-purity hydrogen, thereby avoiding the waste of hydrogen resources by traditional Claus process. Microwave-induced discharge with spherical bio-char for H2S decomposition is proposed. The bio-char was treated by graphitization modification in presence of microwave heating and iron additive. The influences of graphitization parameters including iron loading and microwave irradiation time on the bio-char graphitization degree were studied. Subsequently, the modified bio-char was applied to induce microwave discharge, and the effects of graphitization parameters on discharge performance were discussed. Lastly, the attention was paid to investigate catalytic effect of microwave-induced discharge with the modified bio-char for H2S decomposition. The results showed the best graphitization degree of bio-char was achieved at iron loading of 6 mmol/g and microwave irradiation time of 60 min. The improvement of bio-char graphitization degree enhanced discharge intensity, thus promoting bed temperature. Microwave discharge exhibited a favorable catalytic effect on H2S decomposition, with initial and ending conversions at 97.4% and 83.2% in a two-hour test, respectively, because of synergistic effect of microwave discharge effect, microwave thermal effect and catalytic activity of the modified bio-char.

Effect of alkaline leaching of phosphogypsum on sulfate reduction activity and bacterial community composition using different sources of anaerobic microbial inoculum

Phosphogypsum (PG), a by-product of the phosphate industry, is high in sulfate, (SO42−), which makes it an excellent substrate for sulfate-reducing bacteria (SRB) to produce hydrogen sulfide. This work aimed to optimize SO42− leaching from PG to achieve a high biological reduction of SO42− and generate high sulfide concentrations for subsequent use in the biological recovery of elemental sulfur. Five SRB consortia were isolated and enriched from: IS (Industrial sludges), MS (Marine sediments), WC (Winogradsky column), SNV (petroleum industry sediments) and PG (stored Phosphogypsum). The five consortia showed reduction activity when using PG leachate (with water) as source of SO42− and lactate, acetate, or glucose as the electron donor. The highest reduction rate (81.5 %) was registered using lactate and the IS consortium (81.5 %) followed by MS (79 %) and PG (71 %). To enhance the concentration of leached SO42− from PG for future utilization with the isolated consortia, PG was treated with NaOH solutions (2 % and 5 %). SO42− release of 97 % was achieved with a 5 % concentration and the resulting leachate was further diluted to target a SO42− concentration of 12.4 g·L−1 for utilization with the isolated consortia. Compared to water leachate, a significantly higher reduction rate was registered (2 g·L−1 of SO42) using the IS consortium, demonstrating limited inhibition effect of sulfide− concentration on SRB functionalities. Moreover, metagenomic analysis of the consortia revealed that using PG as a source of SO42− increased the abundance of Deltaproteobacteria, including known SRB like Desulfovibrio, Desulfomicrobium, and Desulfosporosinus, as well as novel SRB genera (Cupidesulfovibrio, Desulfocurvus, Desulfococcus) that showed, for the first time, significant potential as novel sulfate-reducers using PG as a SO42− source.

Simultaneous removal of sulfide and bicarbonate from synthetic wastewater using an algae-assisted microbial fuel cell

ABSTRACT The anaerobic digestion (AD) process is one of the most practiced technologies for the remediation of organic waste and maximization of energy recovery in terms of biogas or biomethane. The presence of other gaseous components in biogas, e.g. CO2 and H2S, often makes its direct application in engines and electricity production unsuitable. This work aimed to develop and utilize an algae-assisted microbial fuel cell (AMFC) for the purification of biogas by removing both CO2 and H2S and simultaneous bioelectricity generation. In addition to biogas clean-up, elemental sulfur recovery and CO2 utilization for algae cultivation add value to the proposed AMFC process. Experiments were performed with both sulfide and bicarbonate in their dissolved form, in the respective anodic and cathodic chambers of the AMFC. The sulfide concentration was varied from 100 to 800 mg/l and the AMFC exhibited a sulfide removal efficiency exceeding 97% at all concentrations tested. The process efficiency dropped, however, at sulfide concentrations above 300 mg/l in terms of both sulfide removal and power output. The AMFC performed best at 400 mg/l sulfide by exhibiting a power density of 24.99 mW/m3 and sulfide removal efficiency of 98.87%. The system exhibited columbic efficiency (CE %) in the range of 7.85–80%. The total alkalinity representing CO2, carbonate and bicarbonate levels in the algae-based system was reduced by 49.54%. The electrical energy recovered from the AMFC was 0.1 kWh/m3 and the total energy recovery, which is the sum of the electrical and algal lipid energy, amounted to 7.25 kWh/m3.

Contextual Mixture of Experts: Integrating Knowledge into Predictive Modeling

This work proposes a new data-driven model devised to integrate process knowledge into its structure to increase the human-machine synergy in the process industry. The proposed Contextual Mixture of Experts (cMoE) explicitly uses process knowledge along the model learning stage to mold the historical data to represent operators' context related to the process through possibility distributions. This model was evaluated in two real case studies for quality prediction, including a sulfur recovery unit and a polymerization process. The contextual mixture of experts was employed to represent different contexts in both experiments. The results indicate that integrating process knowledge has increased predictive performance while improving interpretability by providing insights into the variables affecting the process's different regimes.

Hydrophilic functionalization of rhodium metallene for saving-energy hydrogen production and sulfur recovery

The use of thermodynamically more favorable sulfion oxidation reaction (SOR) to replace sluggish oxygen evolution reaction is an effective method for energy-saving production of hydrogen. Herein, we propose the synthesis of organic–inorganic hybrid through the modification of 1-hydroxyethylidene-1,1-diphosphonic acid on Rh metallene (HEDP-Rh metallene) as a bifunctional electrocatalyst for hydrogen evolution reaction (HER) and SOR. The modification of hydrophilic HEDP can effectively promote the water adsorption, thereby accelerating the mass/electron transfer at the interface. The HEDP-Rh metallene requires low overpotentials of 30 mV at 10 mA cm−2 for HER and 0.538 V at 100 mA cm−2 for SOR. In HER-SOR coupled reaction, HEDP-Rh metallene drives the current density of 100 mA cm−2 at 1.08 V for concurrent production of hydrogen and sulfur, highlighting energy-efficient hydrogen production and sulfur recycle.

Nickel-doped CuxO/Al2O3 catalyzes oxidation of H2S at near ambient temperature: Performance evaluation and mechanism exploration

A series of Ni-doped CuxO/Al2O3 catalysts were developed for catalytic oxidation of H2S, and catalytic conditions of Ni content, temperature and humidity were optimized by measuring H2S performance. The surface of the catalyst doped with Ni (2.5 wt%) exhibited three-dimensional (3D) nano-network structure, largest number of basic sites and oxygen vacancies (VOs). Ni-Cu synergistic effect improved desulfurization capacity of H2S by catalysts at near ambient temperature. 3D nano-network structure provided more sulfur storage space. Basic sites from NiO and VOs from CuxO effectively enhanced catalyst-H2S interaction by hydroxylating H2O, thus promoting dissociation and oxidation of H2S, eventually resulting in a high desulfurization capacity (334.3 mg/g). Desulfurization reaction product was mainly S (91.0%), and by-products were mainly sulfate and CuS. Additionally, our synthesized catalyst can realize sulfur recovery. Therefore, Ni-doped CuxO/Al2O3 is a promising H2S removal catalyst at low temperature.

Polymeric membranes for the oxygen enrichment of air in sulfur recovery units: Prevention of catalyst deactivation through BTX reduction

Polymeric membranes for the oxygen enrichment of air in sulfur recovery units: Prevention of catalyst deactivation through BTX reduction

Investigation and comparison of technologies and methods of sulfur recovery and production processes

Sulfur is found at the land's surface, in quarries, and as a natural sulfur resource. However, most of the part sulfur is obtained during the sulfur removal processes from crude oil or gas. These recovery processes are essential for the global energy resource market. Approaches to sulfur mining and recovering techniques are discussed and compared during the literature review and description analysis. Methods that are majorly used in the industry, their process flow diagrams, and principal of work are explained and compared relative to the modern methods of sulfur removal processes.

Streamlined methods for structural analysis and design of sulfur recovery facilities

Streamlined methods for structural analysis and design of sulfur recovery facilities

Analysis of Sulfur Recovery Unit (SRU) Refinery as Sulfur Emission Control Unit at PT X, Indonesia

PT X is an Indonesian oil and gas processing industry. Recognizing the potential harm posed by gas emissions from oil and natural gas processing, PT X is actively working to control air pollution. One of their initiatives involves the construction of a Sulfur Recovery Unit (SRU) refinery to reduce sulfur gas emissions, particularly from H2S, by converting them into liquid sulfur products. The SRU refinery effectively processes approximately 73% of the H2S gas emitted during production. In January 2023, air quality measurements were conducted on stack 94-F-403 SRU, revealing the following results: the average concentration of SO2 emissions was 14.69 mg/m3, and the average concentration of NO2 emissions was 3.04 mg/m3. These measurements indicate that both parameters fall below the quality standards set by the Indonesian Minister of Environment Regulation No. 13 of 2009, which defines acceptable emission limits for the oil and gas industry. Based on these findings, it can be concluded that the emissions from stack 94-F-403 SRU are classified as non-polluting, adhering to the Indonesian government's quality standards. PT X's commitment to environmental responsibility is evident through their implementation of the SRU refinery, which significantly reduces gas emissions and ensures compliance with regulatory requirements.