Sulphur Recovery Unit

Semi-passive bioremediation is a promising strategy to mitigate persistent low volume mine-impacted wastewater containing high sulphate concentrations. Building on the proof of concept demonstration of the hybrid linear flow channel reactor (LFCR), capable of simultaneous biological sulphate reduction and partial sulphide oxidation with elemental sulphur recovery, the impact of key operating parameters, such as temperature, on process performance is critical to real-world application. Temperature fluctuates seasonally and across the diurnal cycle, impacting biological sulphate reduction (BSR) and partial sulphide oxidation...

In this study, we assess the effects of volumetric flow and feed temperature on the performance of a spiral-wound module for the recovery of free acid using diffusion dialysis. Performance was evaluated using a set of equations based on mass balance under steady-state conditions that describe the free acid yield, rejection factors of metal ions and stream purity, along with chemical analysis of the outlet streams. The results indicated that an increase in the volumetric flow rate of water increased free acid yield from 88% to 93%, but decreased Cu2+ and Fe2+ ion rejection from 95% to 90% and 91% to 86%, respectively...

Anaerobic digestion of nitrogen (N) rich substrates might be hindered when ammonia (NH3 ) formation reaches toxic levels for methanogenic microorganisms. One possible strategy to avoid inhibiting conditions is the removal of NH3 from digestate by stripping and scrubbing technology and by recirculating N depleted digestate back to the digester. This study aimed to i) monitor the performance (mass and energy balances) of a full scale digestate processing cascade that includes an innovative vacuum side stream NH3 stripping and scrubbing system, ii) assess the production cost of ammonium sulphate (AS) solution and iii) evaluate its fertiliser quality...

The coronavirus disease (COVID-19) has become a global pandemic affecting many countries, including Singapore. Previous studies have investigated the relationship of air pollutant levels and meteorological factors with respiratory disease risk and hospital admission rates. However, associations between air pollutant concentrations and meteorological factors with COVID-19 infection have been equivocal. This study aimed to assess the association between core air pollutant concentrations, meteorological variables and daily confirmed COVID-19 case numbers in Singapore...

An integrated hydrometallurgical process was used for the zinc leaching and purification from a zinc ore containing 9.75 wt% zinc. The zinc minerals in the ore were hemimorphite, willemite, and calcophanite. Main gangue minerals were quartz, goethite, hematite, and calcite. Central composite design (CCD) method was used to design leaching experiments and the optimum conditions were found as follows: 30% of solid fraction, 22.05% sulphuric acid concentration, and the leaching temperature of 45 °C. The PLS containing 35...

A fluorometric assay is described for the determination of Cd(II) in environmental and agricultural samples. It is making use of a molecularly imprinted polymer (MIP) and aptamer as dual recognition units, while carbon quantum dots (co-doped with sulphur and nitrogen) and gold nanoparticles (SN-CQD/Au) act as the fluorophores. The aptamer-modified MIP was placed on an SN-CQD/Au-modified indium tin oxide glass electrode. Cd(II) was detected with high selectivity by the recognition sites of the aptamer in the MIP...

The target load concept is an extension of the critical load concept of air pollution inputs to ecosystems. The advantage of target loads over critical loads is that one can define the deposition and the point in time (target year) when the critical (chemical) limit is no longer violated. This information on the timing of recovery requires dynamic modeling. Using a well-documented dynamic model, target loads for acidic deposition were determined for 848 surface waters across Finland, Norway, Sweden, and the United Kingdom for the target year 2050...

The objective of this paper is to present the model-based optimization results of an anaerobic granular sludge internal circulation reactor. The International Water Association Anaerobic Digestion Model No. 1 extended with phosphorus (P), sulfur (S), and ethanol is used to describe the main biological and physico-chemical processes. The high-rate conditions within the reactor are simulated using a flow + reactor model comprised of a series of continuous stirred tank reactors followed by an ideal total suspended solids separation unit...

INTRODUCTION: Four employees at a chemical plant sustained extensive chemical burns following the explosion of a pipeline containing 100% sulphuric acid. We describe the management of these patients from the initial ED triage through to discharge from hospital in life and limb threatening chemical burns. METHODS: Four patients who sustained chemical burns to the torso and extremities are reviewed. Data was retrieved from patient case notes and operating theatre logbooks...

A site-specific study is carried out to assess the suitability of froth flotation for desulphurization of reactive mine tailings at the Musselwhite Mine, Northern Ontario, Canada, to prevent acid mine drainage (AMD). The results from pilot scale flotation tests on an Outokumpu flotation unit are presented, which confirm that froth flotation is effective to reduce sulphide contents of tailings. The factors affecting the treatment effectiveness, such as the froth depth, air flow rate, pulp density and impeller speed are studied...

During the last two decades, there is a common trend of increasing concentrations of dissolved organic carbon (DOC) in streams and lakes in Europe, Canada and the US. Different processes have been proposed to explain this trend and recently a unifying hypothesis was presented, concluding that declining sulphur deposition and recovery from acidification, is the single most important factor for the long-term DOC concentration trends in surface waters. If this recovery hypothesis is correct, the soil water DOC concentrations should increase as well...

The characterization and the agitation leaching of electric arc furnace dust (EAFD) by diluted sulphuric acid have been studied in Part I, as a separate article. The aim of the present research work (Part II) is the development of a purification process of the leach liquor for the recovery of high-purity zinc by electrowinning. The proposed hydrometallurgical process consists of the following four (4) unit operations: (1) Removal of iron as easily filterable crystalline basic sulphate salt of the jarosite type, at atmospheric pressure, by chemical precipitation at pH: 3...

Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO2 emissions are among the highest when burning coal for power generation. Therefore, the capture of CO2 from power plants may contribute significantly in reducing global CO2 emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO2 concentrations. After further conditioning, the highly concentrated CO2 is compressed and transported in the liquid state to, for example, geological storages...

Polycyclic aromatic sulphur heterocyclic (PASH) compounds, such as dibenzothiophene (DBT) and alkylated derivatives are used as model compounds in biodesulfurization processes. The development of these processes is focused on the reduction of the concentration of sulphur in gasoline and gas-oil [D.J. Monticello, Curr. Opin. Biotechnol. 11 (2000) 540], in order to meet European Union and United States directives. The evaluation of biodesulfurization processes requires the development of adequate analytical techniques, allowing the identification of any transformation products generated...

In the United Kingdom, as in other regions of Europe and North America, recent decreases in surface water sulphate concentrations, due to reduced sulphur emissions, have coincided with marked increases in dissolved organic carbon (DOC) concentrations. Since many of the compounds comprising DOC are acidic, the resulting increases in organic acidity may have the potential to offset the benefits of a decrease in mineral (sulphate) acidity. To test this, we used a triprotic model of organic acid dissociation to estimate the proportional organic acid buffering of reduced mineral acidity as measured in the 22 lakes and streams monitored by the UK Acid Waters Monitoring Network...

The United Kingdom Acid Waters Monitoring Network (AWMN) was established in 1988 to determine the ecological impact of acidic emissions control policy on acid-sensitive lakes and streams. AWMN data have been used to explore a range of causal linkages necessary to connect changes in emissions to chemical and, ultimately, biological recovery. Regional scale reductions in sulphur (S) deposition have been found to have had an immediate influence on surface water chemistry, including increases in acid neutralising capacity, pH and alkalinity and declines in aluminium toxicity...

The purification of municipal incinerator gases generates huge quantities of both fly ashes and used lime, containing high amount of heavy metals (Pb, Cd, Zn and Hg). The used lime is mainly contaminated by Pb and often considered as hazardous waste. This paper is related to a laboratory study on the performance of electrochemical techniques used to recover Pb from leachate produced during used lime decontamination. Two types of electrolytic units (monopolar and bipolar electrode cells) using different electrode materials were studied...

Aquatic acidification by deposition of airborne pollutants emerged as an environmental issue in southeastern Canada during the 1970s. Drawing information from the extensive research and monitoring programs, a sequence of issue assessments demonstrated the necessity of reducing the anthropogenic emissions of acidifying pollutants, particularly sulphur dioxide (SO2). The 1991 Canada-U.S. Air Quality Agreement (AQA) was negotiated to reduce North American SO2 emissions by approximately 40% relative to 1980 levels by 2010, and at present, both countries have reduced emissions beyond their AQA commitment...

Sulphur deposition in Sweden has decreased to less than half of the levels recorded in 1970 and now signs of recovery from acidification of surface waters are beginning to appear. We investigated time trends of water chemistry between 1985 and 1998 in 13 streams draining small forested catchments with generally shallow acid sensitive soils. At nine of the catchments, bulk deposition was monitored as well. Sulphate concentrations decreased in both stream water and deposition, although with somewhat smaller trends in stream water compared with deposition...

The green sulphur bacterium Chlorobium thiosulfutophilum was used to remove hydrogen sulphide from synthetic industrial wastewater and convert it to elemental sulphur in a fixed-film continuous-flow photosynthetic bioreactor. Twenty 150 mm x 3 mm ID Tygon tubes formed the active part of the reactor resulting in a total volume of 21.2 mL. Seven steady states were achieved under different experimental conditions using this tubular photo-reactor. Sulphide loading rates ranged from 111 to 328 mg/hL under influent flowrates of 9...