Detection of incipient self-ignition process in solid fuels through gas emissions methodology

The aim of this study is to propose an experimental methodology to detect incipient self-ignition processes in solid fuels. This methodology is based on the gases emissions of different solid fuels, varying the degree of compaction and the grain size of the materials. To achieve this goal, a procedure for the collection and analysis of the gases emitted by samples of various fuels has been developed, analysing the temperatures at which these emissions begin. The results obtained for different materials show that it is possible to detect incipient spontaneous combustion processes using measurements of CO and CO₂ emissions during heating process, and then to set alarm thresholds based on the concentrations of these gases. Those results have been compared with results from conventional thermogravimetry and differential scanning calorimetry tests and it is shown that the proposed methodology detect the self-ignition process start point in advance.     

Effect of solvent on the hydrothermal liquefaction of macro algae Ulva fasciata

Hydrothermal liquefaction is an attractive approach for the conversion of aquatic biomass like algae as it does not require the energy intensive drying steps. The objective of the study is to understand the effect of various solvents (H₂O, CH₃OH and C₂H₅OH) on product distribution and nature of products of hydrothermal liquefaction of macro algae Ulva fasciata (MAUF). Hydrothermal liquefaction of MAUF was performed using subcritical H₂O (300 °C) as well as supercritical organic solvents CH₃OH and C₂H₅OH (300 °C). The use of alcoholic solvents significantly increased the bio-oil yield. The bio-oil yield was 44% and 40% in case of liquefaction with CH₃OH and C₂H₅OH respectively whereas the bio-oil yield was 11% with H₂O. Use of alcoholic solvents converted the acids obtained in bio-oil to the corresponding methyl and ethyl esters. ¹H NMR data showed that use of alcoholic solvents (C₂H₅OH and CH₃OH) increased aliphatic content of bio-oil1 (ether/methanol/ethanol fraction). FTIR and SEM results showed the difference in the bio residue obtained using alcoholic solvents and H₂O. The results showed that liquefaction with supercritical alcohols is an effective way to produce functional hydrocarbons for chemical feedstock.     

On the effectiveness of mitigation strategies for cryogenic applications

The need for sustainable energy sources, as well as the current energetic crisis involving the majority of markets, has promoted the use of cryogenic liquefaction for the transportation and storage of natural gas (i.e., LNG). To guarantee the development of a robust and safe infrastructure, a complete understanding of the main phenomena occurring at low temperatures is paramount. In this sense, the largest grey areas are the characterization of the combustion at low-initial temperature and the interactions between water and cryogenic liquid. For these reasons, this work presents an experimental campaign on the possible mitigation strategies for the mitigation of consequences related to the accidental release of LNG. Particular emphasis was posed on the direct and indirect effects of water on cryogenic pool fire. The former resulted in a significant increase in the dimensions of fire (∼+50%) and burning rate (∼300%) with respect to the case with no direct contact between water and LNG, whereas the latter generated an abrupt decrease in the measured temperatures (<100 °C). The use of an emergency flare to empty an LNG tank was tested, as well. The spatial distribution of temperature was monitored along with the time to guarantee the safe operability of this equipment in the case of LNG combustion. The explanations for the observed phenomena and trends were provided, allowing for the development of safe procedures for the emergency response related to cryogenic fuels.     

Considerations for using alternative technologies in nutrient management on Cape Cod: Beyond cost and performance

Mitigating non-point source nitrogen in coastal estuaries is economically, environmentally, logistically, and socially challenging. On Cape Cod, Massachusetts, nitrogen management includes both traditional, centralized wastewater treatment and sewering as well as a number of alternative technologies. We conducted semi-structured interviews with 37 participants from governmental and non-governmental organizations as well as related industries to identify the barriers and opportunities for the use of alternative technologies to mitigate nitrogen pollution. The interviews were recorded, transcribed, and then analyzed using content analysis and rhetorical analysis. Cost and technical capacity to reduce nitrogen were the most discussed considerations. Beyond those, there were a slew of additional considerations that also impacted whether a technology would be installed, permitted, and socially accepted. These included: maintenance and monitoring logistics, comparisons to sewering, co-benefits, risk/uncertainty, community culture, extent of public engagement, permitting/regulatory challenges, and siting considerations. The insights about these additional considerations are valuable for transferring to other coastal areas managing nutrient impairments that may have not yet factored in these considerations when making decisions about how to meet water quality goals.     

北京地表水中三氟乙酸的测定

三氟乙酸是HFC-134a等氯氟烃替代品的降解产物,对植物和土壤微生物群落的生长有一定抑制作用。笔者建立了测定TFA质量浓度的实验方法:将样品中的三氟乙酸与硫酸二甲酯在浓硫酸介质中衍生为三氟乙酸甲酯(MTFA),利用MTFA的易挥发性,以顶空进样和气相色谱-质谱联用的方法检测样品中MTFA的质量浓度,进而得到环境水样中TFA的质量浓度。并应用该方法测定了北京部分地表水体中三氟乙酸的质量浓度。测定结果:北京青年湖水样和北海水样中的ρ(三氟乙酸)分别为78和93ng L,而北京大学自来水水样中ρ(三氟乙酸)低于方法检测限10ng L。      

Co-creating an alternative: the moral economy of participating in farmers’ markets

Growing dissatisfaction with the globalised food system, articulated on the behalf of both producers and consumers, has caused a variety of public debates surrounding the ethics of food production and consumption to become increasingly visible in society over the last two decades. Simultaneously, farmers’ markets (FMs) and other forms of direct marketing have experienced a noteworthy increase in participants, indicating an emerging demand for an alternative to conventional food networks, alternatives that are often perceived as providing a more just and moral relationship to food production and consumption. This study examines consumer and producer motivations for participation in FMs and opinions towards conventional and alternative agriculture in order to elucidate what (if any) values and morals are shared among producers and consumers. This study draws upon the theoretical framework of moral economy to understand whether these shared values suggest FM participants are working to co-create an alternative economy based on “moral” principles such as fairness, justice, and reciprocity. This mixed-methods study consists of consumer surveys (N?=?377) and semi-structured interviews with producers (N?=?17) from five FMs in the state of Delaware. The results suggest that producer and consumer motivations to participate in FMs, particularly a shared emphasis on social value, are indicative of a sense of moral economy. However, this moral economy is complicated by tension towards consumers and the alternative food movement more generally expressed on behalf of producers.     

资源型城市统筹规划的思考与建议

以编制区域循环经济发展规划为主线,概述了我国循环经济发展的总体趋势和资源型城市经济转型试点的接续产业发展规划;探索性地提出制定循环经济产业基地集聚区建设规划的工作思路;强调发挥政府规划和投融资政策的引导作用,以及建立产业政策体系和激励机制的必要性。     

污泥酵制园林营养土好氧-厌氧交替法可行性分析

为研究好氧-厌氧交替法用于脱水污泥酵制园林营养土达到无害化、营养化、腐殖化(三化)目标的可行性,开展了好氧、厌氧、交替实验效果分析。结果表明:大肠菌群死亡率,酵温50℃时为80%,60℃时为95%;好氧、厌氧、交替,冬季最高酵温分别为52.5、29.5、52.2℃(夏季分别为62.5、41.8、64℃),大肠菌群达标所需时间好氧、交替均为8 d(冬)和3d(夏),厌氧28 d以上;平均碱解氮,厌氧0.859 g/kg>交替0.856 g/kg>好氧0.798 g/kg;20 d后平均有效磷,交替1.852g/kg>好氧1.692 g/kg>厌氧1.636 g/kg;20 d后平均有效钾:交替14.215 g/kg>好氧13.187 g/kg>厌氧11.945 g/kg;20d后平均腐殖质,交替10.510 g/kg>厌氧9.398 g/kg>好氧8.768 g/kg。分析可知,好氧法、交替法可使发酵污泥达到无害化,营养化、腐殖化指标交替法高于好氧法,交替法用于污泥酵制园林三化营养土可行,其控制参数需实验确定。     

民用固体燃料源的IVOCs排放特征及燃烧温度的影响

中等挥发性有机物(intermediate-volatility organic compounds,IVOCs)是近年备受关注的二次有机气溶胶的重要前体物,但目前急需包括民用固体燃料燃烧在内的源排放数据.本文选择两种成熟度不同的烟煤(灵武煤和徐州煤)和两种生物质(稻秆和松木)为研究对象,结合石英管式炉和稀释通道开展7个温度点(300～900℃,以100℃为间隔)的燃烧实验,采集和分析烟气中的IVOCs,探讨煤和生物质燃烧的IVOCs排放因子、组成以及燃烧温度的影响.结果表明,生物质燃烧的IVOCs平均排放因子[(483±182) mg·kg-1]比烟煤[(190±108) mg·kg-1]高2. 5倍;组成方面,生物质和煤的IVOCs均以剩余UCM占主导[分别为(81±11)%和(68±6)%],而生物质排放的正构及支链烷烃占比明显低于烟煤,但芳香烃略高;燃烧温度对两类燃料的影响存在显著区别:烟煤(以灵武煤为例)的IVOCs在500℃[(340±113) mg·kg-1]比900℃[(63±15)mg·kg-1]高5. 4倍,而生物质在400～500℃和800～900℃时呈现两个含量相当的峰值;随着燃烧温度提升,松木IVOCs中芳香烃的占比从1%增加到29%,剩余UCM则从92%降低到61%,烟煤的变化幅度则很小.进一步结合校正燃烧效率对两类燃料和燃烧温度影响IVOCs排放的机理进行了解释.     

含氧柴油对柴油机排放及细颗粒物碳质组分的影响

乙缩醛(1,1-diethoxyethane)与柴油互溶性好, 可替代乙醇作为生物质来源的柴油含氧添加成分. 生物柴油掺混可以提高乙缩醛和柴油混合燃料的闪点及含氧量. 在柴油发动机台架上, 考察柴油和2种含氧柴油(10%乙缩醛+90%柴油和10%乙缩醛＋10%生物柴油＋80%柴油)在2个固定转速不同负荷的5个工况点的排放特性, 分析了NO_x、HC、CO和PM_2.5排放情况, 并用DRI的碳分析仪分析了PM_2.5中的碳质组分.结果表明, 与普通柴油排放相比, 含氧柴油对NO_x排放速率的影响不大, 在某些工况点HC排放速率有较显著的增加. 含氧柴油降低了柴油机PM_2.5排放速率, 最大降低幅度29%. 从碳质组成上看, 含氧燃料降低了PM_2.5中总碳 (total carbon,TC) 的排放速率, 最大降低幅度24%. 含氧柴油的元素碳(elemental carbon,EC)排放速率普遍低于普通柴油; 有机碳(organic carbon,OC)的排放速率在发动机高转速工况时明显低于普通柴油; PM_2.5的OC/EC值在大多数工况下高于普通柴油. 3种燃料排放PM_2.5的碳质组成百分比相似, OC和EC主要为OC1和EC1. 含氧柴油降低了柴油机PM_2.5的排放速率, 颗粒物中OC的比例有所增加, 但对颗粒物的碳质组分组成没有明显的影响.