Tritium concentrations in the atmospheric environment at Rokkasho, Japan before the final testing of the spent nuclear fuel reprocessing plant

This study aimed at obtaining background tritium concentrations in precipitation and air at Rokkasho where the first commercial spent nuclear fuel reprocessing plant in Japan has been under construction. Tritium concentration in monthly precipitation during fiscal years 2001-2005 had a seasonal variation pattern which was high in spring and low in summer. The tritium concentration was higher than that observed at Chiba City as a whole. The seasonal peak concentration at Rokkasho was generally higher than that at Chiba City, while the baseline concentrations of both were similar. The reason for the difference may be the effect of air mass from the Asian continent which is considered to have high tritium concentration. Atmospheric tritium was operationally separated into HTO, HT and hydrocarbon (CH₃T) fractions, and the samples collected every 3 d-14 d during fiscal year 2005 were analyzed for these fractions. The HTO concentration as radioactivity in water correlated well with that in the precipitation samples. The HT concentration was the highest among the chemical forms analyzed, followed by the HTO and CH₃T concentrations. The HT and CH₃T concentrations did not have clear seasonal variation patterns. The HT concentration followed the decline previously reported by Mason and Östlund with an apparent half-life of 4.8 y. The apparent and environmental half-lives of CH₃T were estimated as 9.2 y and 36.5 y, respectively, by combining the present data with literature data. The Intergovernmental Panel on Climate Change used the atmospheric lifetime of 12 y for CH₄ to estimate global warming in its 2007 report. The longer environmental half-life of CH₃T suggested its supply from other sources than past nuclear weapon testing in the atmosphere.     

When is a soil remediated? Comparison of biopiled and windrowed soils contaminated with bunker-fuel in a full-scale trial

A six month field scale study was carried out to compare windrow turning and biopile techniques for the remediation of soil contaminated with bunker C fuel oil. End-point clean-up targets were defined by human risk assessment and ecotoxicological hazard assessment approaches. Replicate windrows and biopiles were amended with either nutrients and inocula, nutrients alone or no amendment. In addition to fractionated hydrocarbon analysis, culturable microbial characterisation and soil ecotoxicological assays were performed. This particular soil, heavy in texture and historically contaminated with bunker fuel was more effectively remediated by windrowing, but coarser textures may be more amendable to biopiling. This trial reveals the benefit of developing risk and hazard based approaches in defining end-point bioremediation of heavy hydrocarbons when engineered biopile or windrow are proposed as treatment option.     

加入多孔球形颗粒微生物燃料电池的性能研究

设计了一个典型的双室微生物燃料电池,并考察了在阳极室加入多孔球形颗粒条件下对人工合成污水产电性能的影响。实验发现,加入多孔球形颗粒后,最高电压从不加颗粒的253 mV提高到280 mV,持续产电时间从5.5 d提高到8 d,COD去除率从78%提高到82.6%。进一步的实验发现,加入多孔球形颗粒后,系统内阻从286Ω降低到199.4Ω,最大功率密度从78.6 mW/m2提高到114.3 mW/m2。结果表明,微生物易于在多孔球形颗粒上附着和生长,颗粒通过均匀搅拌与阳极表面产生持续碰撞,有利于胞外电子传递到阳极,这一过程大大减小阳极的内阻,增大电池的输出电压进而增大输出功率,从而显著提高电池的产电性能。     

燃料乙醇行业环境污染控制评价指标体系的构建

在分析我国燃料乙醇行业基本信息的基础上,根据其原料特性、生产规模、生产技术、污染控制措施、环境管理等方面的特点,筛选出合适的指标,构建多层次燃料乙醇行业环境污染控制评价指标体系。运用层次分析法确定指标权重分值,建立燃料乙醇行业环境污染控制评价模型,并选取国内燃料乙醇典型企业进行调研,结合行业现状对该指标体系做出合理性和可行性分析。     

Fluid bed gasification – Plasma converter process generating energy from solid waste: Experimental assessment of sulphur species

Often perceived as a Cinderella material, there is growing appreciation for solid waste as a renewable content thermal process feed. Nonetheless, research on solid waste gasification and sulphur mechanisms in particular is lacking. This paper presents results from two related experiments on a novel two stage gasification process, at demonstration scale, using a sulphur-enriched wood pellet feed.Notable SO₂ and relatively low COS levels (before gas cleaning) were interesting features of the trials, and not normally expected under reducing gasification conditions. Analysis suggests that localised oxygen rich regions within the fluid bed played a role in SO₂’s generation. The response of COS to sulphur in the feed was quite prompt, whereas SO₂ was more delayed. It is proposed that the bed material sequestered sulphur from the feed, later aiding SO₂ generation. The more reducing gas phase regions above the bed would have facilitated COS – hence its faster response. These results provide a useful insight, with further analysis on a suite of performed experiments underway, along with thermodynamic modelling.     

Mass,energy and material balances of SRF production process. Part 1: SRF produced from commercial and industrial waste

This paper presents the mass, energy and material balances of a solid recovered fuel (SRF) production process. The SRF is produced from commercial and industrial waste (C&IW) through mechanical treatment (MT). In this work various streams of material produced in SRF production process are analyzed for their proximate and ultimate analysis. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. Here mass balance describes the overall mass flow of input waste material in the various output streams, whereas material balance describes the mass flow of components of input waste stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. A commercial scale experimental campaign was conducted on an MT waste sorting plant to produce SRF from C&IW. All the process streams (input and output) produced in this MT plant were sampled and treated according to the CEN standard methods for SRF: EN 15442, EN 15443. The results from the mass balance of SRF production process showed that of the total input C&IW material to MT waste sorting plant, 62% was recovered in the form of SRF, 4% as ferrous metal, 1% as non-ferrous metal and 21% was sorted out as reject material, 11.6% as fine fraction, and 0.4% as heavy fraction. The energy flow balance in various process streams of this SRF production process showed that of the total input energy content of C&IW to MT plant, 75% energy was recovered in the form of SRF, 20% belonged to the reject material stream and rest 5% belonged with the streams of fine fraction and heavy fraction. In the material balances, mass fractions of plastic (soft), plastic (hard), paper and cardboard and wood recovered in the SRF stream were 88%, 70%, 72% and 60% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC), rubber material and non-combustibles (such as stone/rock and glass particles), was found in the reject material stream.     

化石燃料结构变化对大气中δ~(13)CO_2的影响

根据煤炭、石油和天然气等化石燃料的CO2排放量及其碳稳定同位素组成,用按比例叠加的方法逐年计算1860~1996年CO2化石燃料源的d13CO2(PDB),用简单全球碳循环模式研究该变化对大气d13CO2的影响,并将计算结果与CMDL近10年的监测数据进行对比.结果表明,化石燃料源的d13CO2在140年内下降了4.5,在碳循环模式中考虑这种动态变化之后,大气d13CO2的模拟结果与同期实测值的相关程度有较大提高.     

Combustion performance and emission characteristics on HCCI engine of waste plastic pyrolysis oil biodiesel blends with external PFI and vaporiser

ABSTRACT

Analysis of plastic oil obtained from waste plastic through pyrolysis process, as an alternative to biodiesel is presented in this paper. The HCCI engine is considered for experimental validation of combustion performance and emission characteristics. To accumulate pyrolysis oil as fuel, the design modifications were made in external mixture formation on the existing computerised 4-stroke, single cylinder, water cooled, direct injection kirloskar diesel engine connected with eddy current dynamometer to satisfy HCCI conditions. HCCI engine can be worked on wide assortment of fuels beginning from diesel to different blends (WPPO 5%,10%,15% and 20% by volume) of biodiesel .The designed additional device connected to the engine is utilised for fuel vaporisation and mixture arrangement. In the experimental study, the combustion results were initiate to be of 39.69 % higher Rate of Heat Release (RoHR) for biodiesel HCCI as compared with diesel HCCI. Higher brake thermal efficiency (BTE) was found 37 % without exhaust gas recirculation (EGR) at WPPO 20 % biodiesel blend. And also found 50 % and 65 % reduction in NOx emission and 18 % and 28 % reduction in smoke opacity are obtained for biodiesel vapour induction without EGR and biodiesel vapour induction with 15 % EGR as compared with diesel fuel. The CO (0.34 %), and UHC (2.15 %) emissions are increases with 15 % EGR, but the emissions are within the standard limits specified by the emissions standards.     

Catalytic conversion of waste tyres into valuable hydrocarbons

Tyre recycling has become a necessity because of the huge piles of tyres that represent a threat to the environment. The used tyres represent a source of energy and valuable chemical products. Waste tyres were pyrolysed catalytically in a batch reactor under atmospheric pressure. Calcium carbide was used as a catalyst to explore its effect on pyrolysis product distribution. The effect of temperature, amount of catalyst and time on the yields of the pyrolysed products was investigated. Char yield decreased with increase of pyrolysis temperature while total gas and liquid yields increased. The liquid fraction was obtained with boiling point up to 320 °C. The physical and chemical properties of the pyrolysed products obtained were characterized. The catalytic pyrolysis produced 45 wt.% aromatic, 35 wt.% aliphatic and 20 wt.% of polar hydrocarbons. The distillation data showed that ∼80% of oil has boiling point below 270 °C which is the boiling point for 50% of distilled product in commercial diesel oil. The oil fraction was found to have high gross calorific value; GCV (42.8 MJ kg⁻¹). Its Specific gravity, viscosity, Kinematic viscosity, freezing point and diesel index were also within the limits of diesel fuel. The char residues were studied to investigate their characteristics for use as a possible adsorbent. Surface area of char before and after acid demineralization was determined to determine the adsorptive features for waste water treatment.     

气化熔融处理生活垃圾时灰渣的熔融特性

弄清垃圾灰渣的熔融特性对于保证生活垃圾的气化熔融与液态出渣具有重要作用。针对重庆生活垃圾灰与无烟煤灰形成的灰渣,实验研究了在不同的燃料添加量及添加剂条件下灰渣的熔点与粘度,并结合炉温的变化,分析了不同条件对灰渣熔融及液态出渣的影响。结果表明,灰渣的熔点与粘度均随燃料添加量的增加而升高;向燃料比为10%的灰渣中加入添加剂后,灰渣的熔点降低幅度较小,其粘度却随碱度的增加而增大以至熔渣流动性变差;燃料比为40%时,灰渣熔点与粘度均随添加剂的加入而显著降低,且向渣中加入CaO使得灰渣碱度为1.2时灰渣熔点较低且粘度较小,有利于其熔融与液态出渣。