Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods
Ontology highlight
ABSTRACT:
SUBMITTER:
PROVIDER: S-EPMC10795124 | biostudies-literature | 2024 Jan
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Chloropropanols, one of the major contaminants in food, and the corresponding esters or glycidyl esters (GEs) are of great concern in terms of product safety due to their potential carcinogenicity. During heat processing, glycerol, allyl alcohol, chloropropanol esters, sucralose, and carbohydrate in mixed foodstuffs are probable precursors of chloropropanol. The standard analytical techniques for chloropropanols or their esters are GC-MS or LC-MS following sample derivatization pretreatment. By comparing modern data against that five-year-old before, it appears that the levels of chloropropanols and their esters/GEs in food products have somewhat decreased. 3-MCPD esters or GEs may yet exceed the permitted intake set, however, especially in newborn formula which requires particularly stringent regulatory measures. Citespace (6.1. R2) software was employed in this study to examine the research focii of chloropropanols and their corresponding esters/GEs in the literature.
| S-EPMC9943786 | biostudies-literature
Project description:Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the use of XRF to rapidly identify the spatial extent of contamination, Hg stable isotope fractionation to identify sources and transformation processes, and solid-phase characterization (XAFS) to evaluate Hg forms. The understanding of Hg bioavailability for methylation has been improved by methods such as sequential chemical extractions and porewater measurements, including the use of diffuse gradient in thin-film (DGT) samplers. These approaches have shown varying success in identifying bioavailable Hg fractions and further study and field applications are needed. The downstream accumulation of methylmercury (MeHg) in biota is a concern at many contaminated sites. Identifying the variables limiting/controlling MeHg production-such as bioavailable inorganic Hg, organic carbon, and/or terminal electron acceptors (e.g. sulfate, iron) is critical. Mercury can be released from contaminated sites to the air and water, both of which are influenced by meteorological and hydrological conditions. Mercury mobilized from contaminated sites is predominantly bound to particles, highly correlated with total sediment solids (TSS), and elevated during stormflow. Remediation techniques to address Hg contamination can include the removal or containment of Hg contaminated materials, the application of amendments to reduce mobility and bioavailability, landscape/waterbody manipulations to reduce MeHg production, and food web manipulations through stocking or extirpation to reduce MeHg accumulated in desired species. These approaches often rely on knowledge of the Hg forms/speciation at the site, and utilize physical, chemical, thermal and biological methods to achieve remediation goals. Overall, the complexity of Hg cycling allows many different opportunities to reduce/mitigate impacts, which creates flexibility in determining suitable and logistically feasible remedies.
| S-EPMC6980986 | biostudies-literature
Project description:Torrefaction/carbonization integrated with steam gasification of agricultural biomass for gas production and tar reduction was not investigated. The aim of this study was to evaluate the influence of the torrefaction/carbonization severity on H2-enriched syngas production and tar reduction during steam gasification of wheat straw (WS). The torrefaction/carbonization experiments were initially performed at 220-500 °C to examine the effect of pretreated temperature on the fuel properties of torrefied/carbonized WS. Then, the gasification temperature (700-900 °C) was optimized at 900 °C in terms of gas formation behaviors. Afterward, steam gasification of raw and torrefied/carbonized WS feedstocks was conducted. WS carbonized at 500 °C (WS-500) possessed the highest H2 concentration (54.21 vol%) and syngas purity (85.59%), while the maximum H2/CO molar ratio (1.83), high carbon conversion efficiency (90.33 C%) and cold gas efficiency (109.24%) were observed for WS torrefied at 280 °C. Notably, the cumulative gas yield, H2 yield, and syngas yield respectively reached 102.68 mmol/g, 55.66 mmol/g, and 87.89 mmol/g from steam gasification of WS-500. In addition, the carbonized WS feedstocks, especially WS-500, revealed a lower tar content. Simply put, integrating torrefaction/carbonization with steam gasification provided a novel and effective route to manufacture H2-enriched syngas with extremely low tar content from agricultural biomass.
| S-EPMC9518206 | biostudies-literature
Project description:The wastewater from underground coal gasification (UCG) process has extremely complex composition and high concentrations of toxic and refractory compounds including phenolics, aliphatic and aromatic hydrocarbons, ammonia, cyanides, hazardous metals and metalloids. So, the development of biological processes for treating UCG wastewater poses a serious challenge in the sustainable coal industry. The aim of the study was to develop an innovative and efficient wetland construction technology suitable for a treatment of UCG wastewater using available and low-cost media. During the bioremediation process the toxicity of the raw wastewater decreased significantly between 74%-99%. The toxicity units (TU) ranged from values corresponding to very high acute toxic for raw wastewater to non-toxic for effluents from wetland columns after 60 days of the experiment. The toxicity results correlated with the decrease of some organic and inorganic compounds such as phenols, aromatic hydrocarbons, cyanides, metals and ammonia observed during the bioremediation process. The removal percentage of organic compounds like BTEX, PAHs and phenol was around 99% just after 14 days of treatment. A similar removal rate was indicated for cyanide and metals (Zn, Cr, Cd and Pb). Concluded, in order to effectively assess remediation technologies, it is desirable to consider combination of physicochemical parameters with ecotoxicity measurements. The present findings show that wetland remediation technology can be used to clean-up the heavily contaminated waters from the UCG process. Wetland technology as a nature-based solution has the potential to turn coal gasification wastewater into usable recycled water. It is economically and environmentally alternative treatment method.
| S-EPMC10931533 | biostudies-literature
Project description:ContextComplex systems approaches can help to elucidate mechanisms that shape population-level patterns in diet and inform policy approaches. This study reports results of a structured review of key design elements and methods used by existing complex systems models of diet.Evidence acquisitionThe authors conducted systematic searches of the PubMed, Web of Science, and LILACS databases between May and September 2018 to identify peer-reviewed manuscripts that used agent-based models or system dynamics models to explore diet. Searches occurred between November 2017 and May 2018. The authors extracted relevant data regarding each study's diet and nutrition outcomes; use of data for parameterization, calibration, and validation; results; and generated insights. The literature search adhered to PRISMA guidelines.Evidence synthesisTwenty-two agent-based model studies and five system dynamics model studies met the inclusion criteria. Mechanistic studies explored neighborhood- (e.g., residential segregation), interpersonal- (e.g., social influence) and individual-level (e.g., heuristics that guide food purchasing decisions) mechanisms that influence diet. Policy-oriented studies examined policies related to food pricing, the food environment, advertising, nutrition labels, and social norms. Most studies used empirical data to inform values of key parameters; studies varied in their approaches to calibration and validation.ConclusionsOpportunities remain to advance the state of the science of complex systems approaches to diet and nutrition. These include using models to better understand mechanisms driving population-level diet, increasing use of models for policy decision support, and leveraging the wide availability of epidemiologic and policy evaluation data to improve model validation.
| S-EPMC6650152 | biostudies-literature
Project description:Lead contamination poses significant and lasting health risks, particularly in children. This study explores the efficacy of dried mycelium membranes, distinct from live fungal biomass, for the remediation of lead (Pb(II)) in water. Dried mycelium offers unique advantages, including environmental resilience, ease of handling, biodegradability, and mechanical reliability. The study explores Pb(II) removal mechanisms through sorption and mineralization by dried mycelium hyphae in aqueous solutions. The sorption isotherm studies reveal a high Pb(II) removal efficiency, exceeding 95% for concentrations below 1000 ppm and ∼63% above 1500 ppm, primarily driven by electrostatic interactions. The measured infrared peak shifts and the pseudo-second-order kinetics for sorption suggests a correlation between sorption capacity and the density of interacting functional groups. The study also explores novel surface functionalization of the mycelium network with phosphate to enhance Pb(II) removal, which enables remediation efficiencies >95% for concentrations above 1500 ppm. Scanning electron microscopy images show a pH-dependent formation of Pb-based crystals uniformly deposited throughout the entire mycelium network. Continuous cross-flow filtration tests employing a dried mycelium membrane demonstrate its efficacy as a microporous membrane for Pb(II) removal, reaching remediation efficiency of 85-90% at the highest Pb(II) concentrations. These findings suggest that dried mycelium membranes can be a viable alternative to synthetic membranes in heavy metal remediation, with potential environmental and water treatment applications.
| S-EPMC10977094 | biostudies-literature
Project description:Phosphate plays a chemically unique role in shaping cellular signaling of all current living systems, especially eukaryotes. Protein phosphorylation has been studied at several levels, from the near-site context, both in sequence and structure, to the crowded cellular environment, and ultimately to the systems-level perspective. Despite the tremendous advances in mass spectrometry and efforts dedicated to the development of ad hoc highly sophisticated methods, phosphorylation site inference and associated kinase identification are still unresolved problems in kinome biology. The sequence and structure of the substrate near-site context are not sufficient alone to model the in vivo phosphorylation rules, and they should be integrated with orthogonal information in all possible applications. Here we provide an overview of the different contexts that contribute to protein phosphorylation, discussing their potential impact in phosphorylation site annotation and in predicting kinase-substrate specificity.
| S-EPMC4179730 | biostudies-literature
Project description:The correlation between thermochemical provenance and biochar functionality is poorly understood. To this end, operational reactor temperatures (spanning the reduction zone), pressure and product gas composition measurements were obtained from a downdraft gasifier and compared against elemental composition, surface morphology and polyaromatic hydrocarbon content (PAH) of the char produced. Pine feedstock moisture with values of 7% and 17% was the experimental variable. Moderately high steady-state temperatures were observed inside the reactor, with a ca 50°C difference in how the gasifier operated between the two feedstock types. Both chars exhibited surface properties comparable to activated carbon, but the relatively small differences in temperature caused significant variations in biochar surface area and morphology: micropore area 584 against 360 m2 g-1, and micropore volume 0.287 against 0.172 cm3 g-1. Differences in char extractable PAH content were also observed, with higher concentrations (187 µg g-1 ± 18 compared with 89 ± 19 µg g-1 Σ16EPA PAH) when the gasifier was operated with higher moisture content feedstock. It is recommended that greater detail on operational conditions during biochar production should be incorporated to future biochar characterization research as a consequence of these results.
| S-EPMC5014096 | biostudies-literature
Project description:Air gasification of poultry litter was experimentally investigated in a laboratory scale bubbling fluidised bed gasifier. Gasification tests were conducted at atmospheric pressure using silica sand as the bed material. This paper examines the effect of the equivalence ratio (ER) in the range of 0.18-0.41, temperature between 700 and 800 °C, and the addition of limestone blended with the poultry litter on the yield and composition of tar. An off-line solid phase adsorption method was employed in order to quantify tar compounds heavier than styrene, whereas lighter species such as benzene and toluene were measured by means of on-line micro gas chromatography. Total tar yields were in the range from 15.7 to 30.7 gtotal tar kgpoultry litter (dry and ash free basis) -1. These values are considered low with respect to the feedstocks with a higher organic fraction. It also needs to be noted that the yields of benzene and toluene were measured by on-line micro gas chromatography, a technique which inherently delivers higher tar values compared to commonly employed off-line techniques. By varying the ER, poultry litter blended with limestone showed a reduction in total tar yield whereas poultry litter on its own showed an increasing tar yield over the ER range tested. In the presence of limestone, polycyclic aromatic hydrocarbons (PAHs), heterocyclic compounds, toluene and benzene showed a tendency to reduce over the ER range tested. Since the ER also plays a crucial role in tar reduction, the reduction in tar cannot be unambiguously attributed to calcined limestone/lime (CaCO3/CaO). Increasing the temperature was shown to be effective for reducing the total tar yield but the amounts of polycyclic aromatic hydrocarbons increased. However, no definitive correlation could be established between limestone/lime catalytic activity for tar reduction and elevated gasification temperature, because there was no possibility to study their effects separately. The chemical composition of the tar arising from poultry litter is distinctive compared with conventional lignocellulosic fuels linked to the fact that poultry litter has a higher nitrogen content (≈6.5% w/w (dry and ash free basis)). Nitrogen-containing hydrocarbons such as pyridine, 2-methylpyridine, 2-methyl-1H-pyrrole and benzonitrile were identified in significant amounts. This study has demonstrated that poultry litter gasified in a bubbling fluidised bed yielded a product gas with relatively low tar content while its composition reflects the chemical nature of the feedstock.
| S-EPMC9063797 | biostudies-literature
Project description:Although the use of iron oxide nanoparticles (IONPs) has high potential in remediation and agriculture, a major hindrance to their use includes the risk of contamination of soil and water resources with underexplored effects of IONPs on biota. The fate, phytotoxicity and remediation potential of IONPs are investigated with soil column experiments using 7 nm-sized magnetite (Fe3O4) nanoparticles (magnNPs) and sunflower (Helianthus annuus). Control soil, magnNP-containing soil (10 g magnNPs per kg soil), copper-polluted soil (500 mg Cu per kg soil) and copper-polluted soil containing magnNPs (10 g magnNPs per kg soil and 500 mg Cu per kg soil) support sunflower growth for 57 and 95 days. In magnNP-exposed plants, the occurrence of magnNPs does not affect the growth of the vegetative aerial parts and photosynthetic efficiency. Decreased lipid peroxidation indicates an enhanced antioxidant enzymatic response of magnNP-exposed plants. In plants grown in Cu- and magnNP-Cu-soils, the physiological and biochemical impacts of excess copper are clearly identified, resulting in growth retardation, decreased pigment contents and photosynthetic efficiency, and increased lipid peroxidation and peroxidase (POD) activities. Based on magnetic susceptibility, a higher amount of magnNPs is detected after 57 days in the roots of magnNP-exposed plants (1400 mg kg-1) than in the roots of magnNP-Cu-exposed plants (920 mg kg-1). In the latter, magnNP internalization is likely hampered because of the plants' physiological responses to Cu toxicity. At the working Cu and magnNP concentrations, magnNPs neither decrease Cu accumulation in the plant tissues nor alleviate the overall growth retardation of sunflowers and certain phytotoxic effects induced by excess Cu. However, this study highlights several positive environmental aspects relative to magnNP use, including the harmless effects of magnNPs on sunflowers (1% magnNPs in soil) and the ability of magnNPs to influence Cu mobility in the soil (which could be even more pronounced at lower Cu concentration).
| S-EPMC9417463 | biostudies-literature