粉煤气化工业装置煤粉黏附力表征及其流动性评价

气流床粉煤加压气化工艺中,煤粉颗粒粒径小、比表面积大,受颗粒间黏附力影响,煤粉在锁斗下料单元经常出现结拱架桥现象。本文以SE （Sinopec-ECUST）-东方炉气流床粉煤加压气化工艺为工业应用背景,以典型粒径特征的煤粉样品为研究对象,采用连续介质模型与颗粒间作用力分析相结合的方法,建模求解煤粉颗粒间的黏附力。通过对比不同样品的流动参数、颗粒间作用力及其与重力的相互关系,揭示了平均粒径及细颗粒含量对煤粉流动性和下料过程的影响,并在实验室可视化下料平台和工业装置下料单元对上述结果进行了验证。研究结果表明,随着平均粒径降低、细颗粒含量增加,煤粉流动性减弱,下料逐渐从结拱架桥过渡至无拱自由流。本文为改善入炉煤粉流动性、提高煤粉供料系统运行稳定性提供了有效的参考。     

Comparison of coarse coal dust sampling techniques in a laboratory-simulated longwall section

Airborne coal dust generated during mining can deposit and accumulate on mine surfaces, presenting a dust explosion hazard. When assessing dust hazard mitigation strategies for airborne dust reduction, sampling is done in high-velocity ventilation air, which is used to purge the mining face and gallery tunnel. In this environment, the sampler inlet velocity should be matched to the air stream velocity (isokinetic sampling) to prevent oversampling of coarse dust at low sampler-to-air velocity ratios. Low velocity ratios are often encountered when using low flow rate, personal sampling pumps commonly used in underground mines. In this study, with a goal of employing mine-ready equipment, a personal sampler was adapted for area sampling of coarse coal dust in high-velocity ventilation air. This was done by adapting an isokinetic nozzle to the inlet of an Institute of Occupational Medicine (Edinburgh, Scotland) sampling cassette (IOM). Collected dust masses were compared for the modified IOM isokinetic sampler (IOM-MOD), the IOM without the isokinetic nozzle, and a conventional dust sampling cassette without the cyclone on the inlet. All samplers were operated at a flow rate typical of personal sampling pumps: 2 L/min. To ensure differences between collected masses that could be attributed to sampler design and were not influenced by artifacts from dust concentration gradients, relatively uniform and repeatable dust concentrations were demonstrated in the sampling zone of the National Institute for Occupational Safety and Health experimental mine gallery. Consistent with isokinetic theory, greater differences between isokinetic and non-isokinetic sampled masses were found for larger dust volume-size distributions and higher ventilation air velocities. Since isokinetic sampling is conventionally used to determine total dust concentration, and isokinetic sampling made a difference in collected masses, the results suggest when sampling for coarse coal dust the IOM-MOD may improve airborne coarse dust assessments over “off-the-shelf” sampling cassettes.     

Elemental properties of coal slag and measured airborne exposures at two coal slag processing facilities

In 1974, the National Institute for Occupational Safety and Health recommended a ban on the use of silica sand abrasives containing >1% silica due to the risk of silicosis. This gave rise to substitutes including coal slag. An Occupational Safety and Health Administration investigation in 2010 uncovered a case cluster of suspected pneumoconiosis in four former workers at a coal slag processing facility in Illinois, possibly attributable to occupational exposure to coal slag dust. This article presents the results from a National Institute for Occupational Safety and Health industrial hygiene survey at the same coal slag processing facility and a second facility. The industrial hygiene survey consisted of the collection of: (a) bulk samples of unprocessed coal slag, finished granule product, and settled dust for metals and silica; (b) full-shift area air samples for dust, metals, and crystalline silica; and (c) full-shift personal air samples for dust, metals, and crystalline silica.

Bulk samples consisted mainly of iron, manganese, titanium, and vanadium. Some samples had detectable levels of arsenic, beryllium, cadmium, and cobalt. Unprocessed coal slags from Illinois and Kentucky contained 0.43–0.48% (4,300–4,800 mg/kg) silica. Full-shift area air samples identified elevated total dust levels in the screen (2–38 mg/m³) and bag house (21 mg/m³) areas. Full-shift area air samples identified beryllium, chromium, cobalt, copper, iron, nickel, manganese, and vanadium. Overall, personal air samples for total and respirable dust (0.1–6.6 mg/m³ total; and 0.1–0.4 mg/m³ respirable) were lower than area air samples. All full-shift personal air samples for metals and silica were below published occupational exposure limits. All bulk samples of finished product granules contained less than 1% silica, supporting the claim coal slag may present less risk for silicosis than silica sand. We note that the results presented here are solely from two coal slag processing facilities, and more in-depth air monitoring is needed to better characterize occupational exposure to coal slag dust, metals, and silica at similar facilities.     

新疆某露天煤矿放射性水平调查及人员受照剂量评价

目的 对新疆某开采多年的伴生放射性大型露天煤矿的各场所γ剂量率水平和氡浓度水平进行调查和分析;并评价从业人员所受有效剂量。方法 采用便携式γ剂量率仪FH40G对矿区进行定点监测,利用连续测氡仪对场所内氡浓度水平进行24 h连续监测;并根据测量的γ剂量率和氡浓度估算人员受照剂量。结果 该露天煤矿γ剂量率范围为51.4～435.8 nGy/h,氡浓度24 h平均值为15～25 Bq/m³,人员年有效剂量范围为0.29～1.29 mSv/a。结论 各场所氡浓度水平较低,不需要采取补救行动;大部分场所人员受照剂量远远低于标准要求,排土场局部地区需要采取一定的防护措施。     

用SCGE法检测燃煤污染型砷中毒患者血细胞DNA的损伤作用

目的 探讨砷中毒的致癌机理及寻找灵敏、实用的ＤＮＡ损伤监测指标,方法 应用单细胞凝胶电泳法（ＳＣＧＥ）对贵州省兴仁县燃煤型砷中毒重病区１７５名砷接触者的血细胞ＤＮＡ损伤进行了检测,并分析了相关因素的影响。结果 砷能引起人体血细胞ＤＮＡ单逻断裂,其损伤发生早于临床表现,并与尿砷,发砷呈正相关关系,与皮肤损害进展一致,吸烟和氟的影响可加重睦ＤＮＡ的损伤作用,结论 ＳＣＧＥ具有灵敏、快速、简便等优点,可     

Kinetics Study of Al Extraction from Desilicated Coal Fly Ash by NaOH at Atmospheric Pressure

The most promising source of alumina in the 21st century is the coal fly ash (CFA) waste of coal-fired thermal plants. The methods of alumina extraction from CFA are often based on the pressure alkaline or acid leaching or preliminary roasting with different additives followed by water leaching. The efficiency of the alumina extraction from CFA under atmospheric pressure leaching is low due to the high content of acid-insoluble alumina phase mullite (3Al₂O₃·2SiO₂). This research for the first time shows the possibility of mullite leaching under atmospheric pressure after preliminary desilication using high liquid to solid ratios (L:S ratio) and Na₂O concentration. The analysis of the desilicated CFA (DCFA) chemical and phase composition before and after leaching has been carried out by inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). The morphology and elemental composition of solid product particles has been carried out by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). An automated neural network and a shrinking core model (SCM) were used to evaluate experimental data. The Al extraction efficiency from DCFA has been more than 84% at T = 120 °C, leaching time 60 min, the L/S ratio > 20, and concentration of Na₂O—400 g L⁻¹. The kinetics analysis by SCM has shown that the surface chemical reaction controls the leaching process rate at T < 110 °C, and, at T > 110 °C after 15 min of leaching, the process is limited by diffusion through the product layer, which can be represented by titanium compounds. According to the SEM-EDX analysis of the solid residue, the magnetite spheres and mullite acicular particles were the main phases that remained after NaOH leaching. The spheric agglomerates of mullite particles with non-porous surface have also been found.     

Genotoxicity of complex PAH mixtures recovered from contaminated lake sediments as assessed by three different methods.

Although human exposure generally occurs to mixtures of chemicals, limited toxicological information is available to characterize the potential interactions of the components of environmental mixtures. This study was conducted to compare the genotoxicity of chemically characterized polycyclic aromatic hydrocarbon (PAH) mixtures using in vitro and in vivo techniques. A total of three extracts (E1-E3) were selected from sediment samples collected from a lake adjacent to an abandoned coal gasification site. Sediments were collected on a grid moving downstream and away from the most likely source of PAH contamination, with E1 collected closest to the shore, E2 at an intermediate distance, and E3 furthest from the shore. The sediment samples were extracted in methylene chloride and methanol, dried, and redissolved in an appropriate solvent for evaluation in a battery of genotoxicity assays. Samples were evaluated for their ability to produce point mutations in bacteria and DNA adducts in vitro without metabolic activation or in vivo. Samples were also analyzed using GC/MS. Sample E1 had both the highest concentration of benzo(a)pyrene (BP) (46.5 ppm) and carcinogenic PAHs and, using 32P-postlabeling, induced the highest adduct levels overall in vitro and in vivo. Sample E2, which had a BP concentration of 14 ppm, induced the greatest number of revertants in the bacterial mutagenicity assay. Sample E3, which had the lowest level of carcinogenic PAHs and BP, induced the lowest adduct levels. However, E3 was capable of inducing a positive genotoxic response in bacteria (with S9), although the slope of the response at lower doses was less than that of E2. The in vivo data showed that the major adduct formed by E1 and E2 was a BP adduct. This information could not have been obtained with the Salmonella or in vitro postlabeling tests. Among internal organs, the extracts of all three samples induced the greatest adduct levels in the lung, similarly to previous complex PAH mixtures studied. These data demonstrate the limitations of predicting genotoxic or carcinogenic potential based on chemical analysis or a single biological test. The results suggest that mixture interactions, cytotoxicity and metabolism are likely to have an influence on the potential of a complex mixture of chemicals to produce a carcinogenic effect. In addition, the concentration of genotoxic PAHs and both in vitro and in vivo DNA adduct formations were decreased with increasing distance from the shoreline.     

Decrease in selenium status in relation to coal dust exposure

Selenium (Se) plasma levels were studied 222 coal miners to assess whether selenium is decreased in relation to coal dust exposure, taking age, alcohol, and tobacco consumption into account. Selenium levels decreased significantly with age and current tobacco consumption, among miners aged 34–50. Long-term and current exposure to coal dust were studied. The lowest Se values were observed for those with both long-term and current exposure (60.2 ng/ml), the highest for those never or slightly exposed (64.1 ng/ml); those with long-term exposure not currently exposed fell in an intermediate position (61.3 ng/ml). No relation was observed with alcohol consumption. The association of coal dust with low selenium remained significant after adjustment for age and smoking. © 1996 Wiley-Liss, Inc.