Coal Gasification Waste Research Articles

Enhancing flotation recovery of residual carbon from gasification waste by mixing hydrophobic powder with diesel as collector

Coal gasification fine slag (CGFS) is a solid waste containing residual carbon and ash generated during the coal gasification process, and the separation of the two components is the essential way to realize its environmental pollution reduction and resource value increase. Froth flotation is the preferred method for separating CGFS, but there is a barrier of low carbon recovery in this process due to the extensive adsorption of collector by the well-developed pores on residual carbon. In this study, a sufficiently simple yet innovative collector, a mixture of hydrophobic powder and diesel, was proposed in an attempt to break the bottleneck. Flotation experiments with common diesel and this novel collector were performed respectively, and FTIR, XPS, and SEM-EDX were employed to analyze the collector action mechanism. Flotation results revealed that the novel collector could significantly improve the residual carbon recovery; test results demonstrated that the novel collector could increase the hydrophobic functional group content on the fine slag surface, and the hydrophobic powders in this novel collector mainly appeared at the pore openings of the flotation concentrate. The essence of the mechanism is that the hydrophobic powders play a dual role of blocking pores and providing adsorption sites, thus facilitating the spreading of diesel on the carbon surface and promoting its floatability. The study can provide creative ideas for the efficient disposal of coal gasification waste.

Selected Critical Raw Materials in Waste from Coal Gasification in Poland

In an effort to identify new sources of critical raw materials (CRMs) possibility of recovering selected CRMs from Polish coals, chars, and ashes resulting from the combustion of coals and chars was investigated. The samples were collected from pilot fluidized bed gasification systems. The search for CRMs in coal gasification wastes has not been widely reported before. The study used 2 bituminous coal and 1 lignite sample; the concentration of individual critical raw materials (CRMs) was analyzed using the ICP-MS method. The obtained results were compared with Clarke values in coal ash and in the Earth’s crust, and with the adopted cut-off grade. As shown by the analysis, the highest concentrations of CRMs can be found in fly ash, mainly in samples from the eastern part of the Upper Silesian Coal Basin. This applies mostly to Be, Cs, or Sb due to the fact that their concentrations were found to be higher than the Clarke value in the Earth’s crust; the mentioned fly ashes could be used as potential sources of critical elements if appropriate recovery technologies are developed. In addition, the tested materials have elevated Se, Pb, Ni concentrations, but their recovery is currently not economically viable. Compared to the currently adopted cut-off grade levels, there are no critical elements in the analyzed coal gasification waste that could be recovered.

Measurements of the leachability of potentially hazardous trace elements from solid coal gasification wastes in China

Solid wastes from commercial coal gasification plants are a significant environmental issue in China because of the large quantities produced. In recent years, with the rapid development of coal gasification technologies in China, more and more coal gasification residues are being disposed of in landfills because of the low utilization of the residues. In the present study, the column leaching procedure M1314 developed by the U.S. Environmental Protection Agency was used to evaluate the potential for environmental pollution by potentially hazardous trace elements (Be, V, Mn, Cr, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Hg, Th, and U) in the coarse and fine gasification residues from two plants using General Electric (GE) and Gaskombinat Schwarze Pumpe (GSP) coal gasification technologies in northwest China. The potentially hazardous trace elements in the residues show different release patterns with the liquid–solid ratio increasing. The cumulative leached concentrations of the potentially hazardous trace elements from the coal gasification residues were generally low, and only Mo in the leachate of GSP fine residue was moderately soluble. V in the GSP coal gasification residues showed an increasing leachability in the leaching procedure. As, Se, Mo, Sb, and Tl in some leachates exceeded their thresholds in Level III of the Chinese Quality Standard for Groundwater and/or the Maximum Contaminant Levels of the U.S. National Primary Drinking Water Regulations. According to the risk assessment code, Se in the GE fine residue and Mo in the GE and GSP fine residues had medium risk to the ecosystem. Those data indicated that the potential for environmental pollution by those elements from coal gasification plants should be given consideration.

Clean products from coal gasification waste by flotation using waste engine oil as collector: Synergetic cleaner disposal of wastes

Synergetic cleaner disposal of coal gasification waste and waste engine oil is urgent, as the harmfulness to environment and lacks of clean and efficient technique. In this work, coal gasification fine slag was divided to two clean products without byproducts or wastes by flotation using waste engine oil as flotation collector, achieved the goals of “Carbons Recycle” and “Waste Disposal by Waste”. The waste engine oil improved the flotation property of the −0.5 mm fraction coal gasification fine slag, thereby a flotation concentrate with a loss-on ignition of 88.86 wt% and recovery of 92.13 wt% was produced at the waste engine oil dosage of 3 kg/t. The main components of waste engine oil were hydrocarbons, esters, and heteroatom-containing species, as confirmed by gas chromatography/mass spectrometry. The mechanism of flotation using waste engine oil as a collector for the coal gasification fine slag particles was examined via the measurement of contact angles and wrap angles. The qualified tailings (i.e. flotation tailings and +0.5 mm fraction coal gasification fine slag) with loss-on ignition of less than 5 wt% were also obtained to the standard for direct utilization in building materials. Economic evaluation indicates that the net profit would reach 12309.46 USD/h, with a coal gasification fine slag raw capacity of 400 t/h. This work demonstrates that the application of waste engine oil in coal gasification fine slag flotation is feasible, efficient, economical, and eco-friendly, and it has potential industrial application prospects.

Potential of decarbonized coal gasification residues as the mineral admixture of cement-based material

This paper studied the feasibility of the decarbonized coal gasification waste residues as the admixture of cement-based materials, and discussed the influence of coal gasification coarse slag (CGS) and fine ash (CGA) on the fluidity and compressive strength of cement mortar as the admixture based on the study of physical and chemical properties of the two types of particles. The analysis of the mechanism of coal gasification waste residue on cement hydration was carried out through analysis of the phase characteristics and microstructure, as well as thermal analysis of the cement-coal gasification waste residue mixture hydration product. The results showed that CGA had a negative influence on the fluidity of cement mortar although its particle morphology was mostly spherical, while CGS was conducive to the fluidity. Also, with a strength activity index of 100.9%, CGA had better pozzolanic reactivity than CGS whose strength activity index was 82.7%. XRD experimental results showed that the adding of CGA and CGS greatly reduced the content of calcium hydroxide in the cement hydration products. The fact was that there was no obvious calcium hydroxide in the hydration product when the amount of replacement cement was 30% after 28 days of hydration. Moreover, SEM results showed that the original morphologies of CGA and CGS were severely damaged in the later period of hydration. Therefore, the synergistic use of CGA and CGS may have a good effect on the fluidity and strength of cement-based materials.

Influence of phosphate ions on pit initiation and growth on the stainless steel – 316L in chloride contaminated simulated coal gasification wastewater (CGW) environment

The influence of phosphate ions on the pitting corrosion of stainless steel type 316L was investigated with electrochemical and thermo-chemical methods. DC polarization measurements showed that the pitting could occur spontaneously above 72 °C on SS-316L in chloride containing simulated coal gasification waste water (CGW). Addition of phosphate ions above critical pitting temperature (CPT) in the simulated CGW retarded the oxygen reduction reactions, reduced the pitting frequency and impeded the pitting growth considerably. EIS study revealed that the PO43− ions enhanced the pitting resistance of SS-316L by absorbing and modifying the passive film through the interaction with the hydrated Fe species. XRD analysis of SS-316L surface exposed in simulated CGW containing PO43− ions at 170 °C further confirmed the existence of iron phosphate in the surface corrosion layer.

Preparation of a new high-efficiency resin deodorant from coal gasification fine slag and its application in the removal of volatile organic compounds in polypropylene composites

Deodorizing materials are often restricted from large-scale industrial production due to the high preparation cost. By utilizing the simple acid leaching technology, this study made use of the coal gasification fine slag (FS) as raw material to prepare a cost effective FS-based deodorant (FSD) with a specific surface area of 393 m2 g−1 and a pore volume of 0.405 cm3 g−1. The propane adsorption test on FSD showed the maximum adsorption capacity to be as high as 121.61 mg g−1 at 273 K. The partition coefficient values at 10% and 100% breakthrough (BT) for FSD to adsorb propane were 1.5 × 10−3 and 3.2 × 10−4 mol kg−1 Pa−1, respectively. Furthermore, the FSD was applied in the removal of volatile organic compounds (VOCs) pollutants from polypropylene resin (PP). It showed that the deodorizing effect of the FSD was nearly three times as good as the commonly used zeolite deodorants, which was able to decrease 50 percent of the VOCs volatilization amount in PP resin. Moreover, the FSD can better strengthen the mechanical properties of PP resin. This work provides a new method for the industrial production of deodorants as well as a new direction for the recycle of coal gasification wastes.

Nitrite accumulation performance of aerobic MBBR treating Lurgi coal gasification waste water by adjusting pollutant load and DO concentration

An aerobic moving bed biofilm reactor (MBBR) was adopted to treat Lurgi coal gasification waste water (LCGW) in about 10 months. The pollutant load and dissolve oxygen (DO) concentration were adjusted by trying to maximize the accumulation of in the MBBR for LCGW treatment. The highest accumulation proportion was 73.9%, but was not stable with influent chemical oxygen demand (COD) and DO concentrations of around 1000 and 1.5 mg/L, respectively. Around 1500 mg/L of influent COD concentration and 1.5 mg/L of DO concentration were proper operation conditions for the aerobic MBBR to achieve relatively stable accumulation, with ratio at 53% and ratio at just 4.3% in the effluent. More specifically, free ammonia concentration and DO concentration affected accumulation much more obvious than phenols concentration. The activity and quantity of nitrifying bacteria growth in suspended sludge and biofilm of the MBBR were monitored simultaneously to explain the variations of accumulation performance under different operation conditions.

Determination of biological removal of recalcitrant organic contaminants in coal gasification waste water

Coal gasification waste water treatment needed a sustainable and affordable plan to eliminate the organic contaminants in order to lower the potential environmental and human health risk. In this paper, a laboratory-scale anaerobic–aerobic intermittent system carried out 66 operational cycles together for the treatment of coal gasification waste water and the removal capacity of each organic pollutant. Contaminants included phenols, carboxylic acids, long-chain hydrocarbons, and heterocyclic compounds, wherein the relative content of phenol is up to 57.86%. The long-term removal of 77 organic contaminants was evaluated at different hydraulic retention time (anaerobic24 h + aerobic48 h and anaerobic48 h +aerobic48 h). Contaminant removal ranged from no measurable removal to near-complete removal with effluent concentrations below the detection limit. Contaminant removals followed one of four trends: steady-state removal throughout, increasing removal to steady state (acclimation), decreasing removal, and no removal. Organic degradation and transformation in the reaction were analysed by gas chromatography/mass spectrometry technology.

Purification of coal gasification combined with brewery waste waters in upflow anaerobic sludge blanket digesters

Laboratory-scale upflow anaerobic sludge blanket (UASB) digesters containing granular sludge adapted to brewery effluent were fed increasing concentrations of artificial coal gasification (CG) waste water in brewery effluent and were effective at purifying this combined waste water up to a CG effluent concentration of 15%. At higher CG waste water concentrations and flow rates, performance declined rapidly.

Mutagenic potential of binary and complex mixtures using different enzyme induction systems.

A series of experiments was conducted to investigate the mutagenic potential of binary and complex mixtures in the presence and absence of inducible liver enzyme systems prepared with several different chemical inducers. Liver homogenate (S9, or 9000 x g supernatant) fractions were obtained from Sprague-Dawley rats induced with either Aroclor 1254 (AR), phenobarbital (PB), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or corn oil (UI). the mutagenic potential of test samples was measured with Salmonella typhimurium strain TA98 using each of the various S9 fractions. Test samples included benzo[a]pyrene (BaP), pentachlorophenol (PCP), a binary mixture of BaP and PCP, two five-component mixtures, a methylene chloride extract of wood preserving waste-amended soil, and a methanol extract of coal gasification waste. At a dose of 25 micrograms/plate, BaP produced 55, 83, 217, and 161 net revertants per plate with UI-, PB-, AR-, and TCDD-induced S9, respectively. The complex mixture extracted from the wood preserving waste-amended soil induced approximately equal responses with all four S9 mixes. At a dose of 250 micrograms/plate, the methanol extract of a coal gasification waste produced 56 net revertants using the uninduced S9; however, when Ar- and TCDD-induced S9 was used, 129 and 67 net revertants were observed, respectively. These data demonstrate the relative importance of the various induced cytochrome P-450 isozymes for the metabolism of mutagenic chemicals and complex mixtures.

Utilization of quantitative structure-activity relationships (QSARs) in risk assessment: Alkylphenols

Alkylphenols are a class of environmentally pervasive compounds, found both in natural (e.g., crude oils) and in anthropogenic (e.g., wood tar, coal gasification waste) materials. Despite the frequent environmental occurrence of these chemicals, there is a limited toxicity database on alkylphenols. We have therefore developed a “toxicity equivalence approach” for alkylphenols which is based on their ability to inhibit, in a specific manner, the enzyme cyclooxygenase. Enzymeinhibiting ability for individual alkylphenols can be estimated based on the quantitative structure-activity relationship developed by Dewhirst (1980) and is a function of the free hydroxyl group, electron-donating ring substituents, and hydrophobic aromatic ring substituents. We evaluated the toxicological significance of cyclooxygenase inhibition by comparison of the inhibitory capacity of alkylphenols with the inhibitory capacity of acetylsalicylic acid, or aspirin, a compound whose low-level effects are due to cyclooxygenase inhibition. Since nearly complete absorption for alkylphenols and aspirin is predicted, based on estimates of hydrophobicity and fraction of charged molecules at gastrointestinal pHs, risks from alkylphenols can be expressed directly in terms of “milligram aspirin equivalence,” without correction for absorption differences. We recommend this method for assessing risks of mixtures of alkylphenols, especially for those compounds with no chronic toxicity data.

Dynamically Formed Hydrous Zirconium (IV) Oxide—Polyelectrolyte Membranes: V. Non-Homogeneous Poly (Acrylic Acid—Covinyl Alcohol) Membranes: Rejection and Flux Properties and the Treatment of Coal Gasification Waste Water

A non-homogeneous poly(acrylic acid—covinyl alcohol) copolymer ( I) was synthesized. This copolymer was used as polyelectrolyte in a dynamically formed hydrous zirconium (IV) oxide—polyelectrolyte membrane. The resultant Zr(I) membrane gave salt rejection figures exceeding 99% and flux values of 2500 lmd. A set of these Zr(I) membranes was used to treat a coal gasification wastewater in a laboratory experiment, and the membranes rejected a wide variety of constituents satisfactorily.

Presence of an Unusual Methanogenic Bacterium in Coal Gasification Waste

Methanogenic bacteria growing on a pilot-scale, anaerobic filter processing coal gasification waste were enriched in a mineral salts medium containing hydrogen and acetate as potential energy sources. Transfer of the enrichments to methanol medium resulted in the initial growth of a strain of Methanosarcina barkeri, but eventually small cocci became dominant. The cocci growing on methanol produced methane and exhibited the typical fluorescence of methanogenic bacteria. They grew in the presence of the cell wall synthesis-inhibiting antibiotics d-cycloserine, fosfomycin, penicillin G, and vancomycin as well as in the presence of kanamycin, an inhibitor of protein synthesis in eubacteria. The optimal growth temperature was 37 degrees C, and the doubling time was 7.5 h. The strain lysed after reaching stationary phase. The bacterium grew poorly with hydrogen as the energy source and failed to grow on acetate. Morphologically, the coccus shared similarities with Methanosarcina sp. Cells were 1 mum wide, exhibited the typical thick cell wall and cross-wall formation, and formed tetrads. Packets and cysts were not formed.

Regulatory Requirements for Land Disposal of Coal Gasification Waste and Their Implications for Disposal Site Design

Abstract The regulatory requirements applicable to the land disposal of solid wastes from coal gasification plants are reviewed from the standpoint of disposal site design and design performance evaluation. After consideration of the design flexibility allowed under existing regulations, three approaches to disposal site design are analyzed, and the state-of-the-art approach is determined to be the preferred one. This approach utilizes the data generated through systematic laboratory and field studies and can be adapted to a range of regulatory requirements, site- and technology-specific considerations, and different levels of environmental protection. A program to develop the data base for use in the state-of-the-art design approach is recommended. The program emphasizes generation of lsquo;real world’ data on long-term leaching characteristics of the waste, the capacity of soils to attenuate leachate, and correlation of the attenuation capacity with key soil parameters.

Coal gasification waste disposal—the impact of regulation

AbstractConversion of coal to synfuels is expected to produce a broad range of solid wastes requiring disposal and, inevitably, proliferating Government regulation. Where do we stand now?

Acute toxicity of leachates from coal gasification and liquefaction solid wastes to the fathead minnow, Pimephales promelas

Abstract Ninety‐six hour static bioassays were conducted with one‐to‐six‐day‐old fathead minnow fry to determine the acute toxicity of leachates generated from Lurgi gasification ashes, an H‐Coal liquefaction residue and an SRC‐I liquefaction residue. LC‐50 values, their 95% confidence intervals and the amount of dilution necessary to eliminate mortality during the 96‐hour bioassays were determined. Leachates that were generated from the solid wastes at four pH levels and under anaerobic and aerobic conditions were analyzed for approximately 40 chemical constitutents. Nineteen of the constitutents were found to exceed recommended water quality criteria levels in some of the samples at pH values between 2.3 and 11.3. All eight leachates, including the unadjusted pH leachate, generated from the Lurgi ash of an Illinois No. 6 coal contained concentrations of Ca, F, Li, Mn, Pb, SO4 and Sb which exceeded recommended water quality levels. Leachates produced from the gasification ashes were not acutely toxic at ...

Process for power generation from wet air oxidation with application to coal gasification waste waters

Process for power generation from wet air oxidation with application to coal gasification waste waters

Comparative toxicity of solid waste leachates to Daphnia magna

The comparative acute and chronic toxicities of municipal, industrial, coal-fired power plant, and synthetic fuel solid waste leachates to the aquatic invertebrate Daphnia magna were determined. Seventeen leachates were laboratory-derived by extraction with 0.5 N acetic acid, and one, an arsenic-contaminated groundwater, was naturally derived. The acute toxicity 48-h LC 50 estimates (concentrations of the test materials that killed 50% of the test organisms in 48 h) ranged from 0.0005% for a dye waste leachate to > 100% (i.e., undiluted) for a coal gasification waste leachate. The most toxic leachates were derived from a dye waste, a plater's waste, and the arsenic-contaminated groundwater, and the least toxic were from a soybean process cake waste and a coal gasification waste. Of the 16 leachates used in the 28 day chronic toxicity tests, only the arsenic-contaminated groundwater and a municipal sewage sludge significantly affected D. magna reproduction. The former material at 1.0% concentration and the sludge at 0.1% caused about an 88% reduction in the numbers of young produced by exposed females compared with controls. Generally, the industrial waste leachates were more toxic than those from the power plant and synthetic fuel wastes. Because its presence in the test materials interfered with interpretation of the results, acetic acid may not be an appropriate extraction medium for preparation of leachates.