Chemical absorption of carbon dioxide with asymmetrically heated polytetrafluoroethylene membranes

In this study, the absorption of carbon dioxide using an absorbent composed of 2-amino-2-methyl-L-propanol (AMP) + monoethanolamine (MEA) + piperazine (PZ) in asymmetric and symmetric polytetrafluoroethylene (PTFE) membrane contactors was investigated. Experiments were conducted using various gas flow rates, liquid flow rates, and absorbent blends. CO(2) recovery increased with increasing liquid flow rates. The mean pore size of PTFE membrane reduced via heating treatment. An asymmetric membrane had a better CO(2) recovery than a symmetric membrane. For the asymmetric membrane, placing the smaller pore-size side of the membrane in contact with the liquid phase, reduced the level of wetting of the membrane. The membrane mass transfer coefficient and durability of the PTFE membrane were enhanced by asymmetrically heating.     

Passive monitoring of nitrogen dioxide in urban air: a case study of Durban metropolis, South Africa

To devise and implement strategies to manage the quality of urban air, a metropolis needs air pollution data on which an air quality management plan can be formulated. Although air pollutants can come from several sources, many reports suggest that nitrogen dioxide from motor vehicle emissions is the major contributor to air pollution in cities. Since vehicles stop or move slowly through traffic intersections, concentrations of nitrogen dioxide (NO(2)) are expected to be relatively high at these sites. Inexpensive Ogawa passive samplers were placed at selected traffic intersections in the Durban Metropolis to trap the NO(2) which was then analysed by a sensitive laboratory-based method. The data obtained by this method was compared with data from sophisticated system comprising an active sampler cum on-line chemiluminescence detector. The sampling was done over a twelve month period to cover all seasons. Statistical analysis of the data showed that there was no significant difference between the means for the two methods. This study has established that an Ogawa passive sampler may be used as an economical and reliable collector for NO(2) in ambient air under varying climatic conditions. Further, the analysis method using a UV-Visible spectrophotometer was sensitive enough to detect NO(2) at the 10-20 ppb level. The cost of the method should be well within the budgets of most municipalities and it would motivate them to develop policies to alleviate traffic congestion.     

二氧化碳回收技术进展

CO2的过量排放对全球的气候变暖有着不可推卸的责任,同时CO2又是一种重要的碳资源,对它的回收和利用将具有很大的经济效益和社会效益。CO2回收的方法主要是膜吸收法、变压吸附法、化学吸收法和低温分离法,特别是离子液体对CO2的吸收,为CO2的减排提供了良好的手段。     

Hazards from carbon dioxide capture, transport and storage

Carbon capture and storage (CCS) is a developing technology which raises a number of issues in terms of safety. CCS involves a chain of processes comprising capture of carbon dioxide, transport and injection into underground storage. In work carried out for the IEA Greenhouse Gas R&D Programme, a number of high-level hazard identification (HAZID) studies have been performed with the help of industry experts. The HAZIDs considered a carbon capture and storage chain involving capture, pipeline transport and injection. HAZID has been performed at a high-level for such a CCS chain with three types of capture technology and using pipeline transport. It is hoped that the results of the HAZID studies will be of use to those carrying out CCS projects, but should not be a substitute for them carrying out a full suite of integrated hazard management processes. A number of example hazards have been described to raise awareness of the range of hazards in a CCS process and to identify barriers which could prevent, minimise, control or mitigate CCS hazards. Bow-tie diagrams have been produced to record the information from this study and to organise it in a systematic way so that it is far less likely that contributors to and mitigators of hazards will be missed. The diagrams are available in Excel spreadsheet format so that they can be used as the starting point for development by specific CCS projects. CCS technology is still advancing and a number of knowledge gaps in terms of safety have been identified which require further development.     

气体二氧化氯的光降解规律研究

为研究气体二氧化氯的光降解规律,利用自行设计的光降解装置,考察不同波长光源、温度和气体二氧化氯初始质量浓度对其降解速率的影响,同时以暗室降解作为参比试验。结果表明:分别在365 nm紫外光、日光、254 nm紫外光以及400～700 nm荧光照射下,相同初始质量浓度的气体二氧化氯的降解速率逐渐下降;当温度在15～25℃范围变化时,相同初始质量浓度的气体二氧化氯的日光降解速率基本相同;不同质量浓度的气体二氧化氯在日光照射下,降解速率随气体质量浓度的增加而增大。因此,对气体二氧化氯的光降解起主要作用的波长是在365 nm附近的紫外光;温度对其降解速率基本没有影响;在日光照射下,气体二氧化氯的降解速率与质量浓度的一次方成正比,属于一级反应,其半衰期与初始质量浓度无关,仅与反应速率常数k有关,半衰期约为63 min。     

Electricity-driven ammonia oxidation and acetate production in microbial electrosynthesis systems

• MES was constructed for simultaneous ammonia removal and acetate production. • Energy consumption was different for total nitrogen and ammonia nitrogen removal. • Energy consumption for acetate production was about 0.04 kWh/g. • Nitrate accumulation explained the difference of energy consumption. • Transport of ammonia and acetate across the membrane deteriorated the performance. Microbial electrosynthesis (MES) is an emerging technology for producing chemicals, and coupling MES to anodic waste oxidation can simultaneously increase the competitiveness and allow additional functions to be explored. In this study, MES was used for the simultaneous removal of ammonia from synthetic urine and production of acetate from CO₂. Using graphite anode, 83.2%±5.3% ammonia removal and 28.4%±9.9% total nitrogen removal was achieved, with an energy consumption of 1.32 kWh/g N for total nitrogen removal, 0.45 kWh/g N for ammonia nitrogen removal, and 0.044 kWh/g for acetate production. Using boron-doped diamond (BDD) anode, 70.9%±12.1% ammonia removal and 51.5%±11.8% total nitrogen removal was obtained, with an energy consumption of 0.84 kWh/g N for total nitrogen removal, 0.61 kWh/g N for ammonia nitrogen removal, and 0.043 kWh/g for acetate production. A difference in nitrate accumulation explained the difference of total nitrogen removal efficiencies. Transport of ammonia and acetate across the membrane deteriorated the performance of MES. These results are important for the development of novel electricity-driven technologies for chemical production and pollution removal.     

CO2泡沫混凝土碳封存潜力分析

CO₂捕集、利用与封存是碳中和技术体系的重要组成部分,混凝土在大规模吸收CO₂方面具有巨大的发展潜力.为了掌握CO₂泡沫混凝土的碳封存潜力,分析了CO₂泡沫混凝土的固碳机制,建立了CO₂泡沫混凝土固碳能力的数学模型,估算了CO₂泡沫混凝土的固碳和储碳能力.结果表明,CO₂泡沫混凝土碳封存能力的99%以上是由混凝土骨架的化学碳化方式完成的,而泡孔的储碳能力较弱;按照30%碳化率估算,我国每年生产的混凝土在全生命周期内的碳封存量平均为2.18亿t,超过大兴安岭林区森林1 a的碳汇;近5年,我国CO₂泡沫混凝土的碳封存潜力为5.80亿t ·a^-1,在煤电一体化矿区的固废和废气资源化利用方面具有很好的应用前景.CO₂泡沫混凝土在凝固前的稳定性是下一步要重点解决的技术难题.     

硫酸法钛白粉“三废”治理与利用的研究进展

介绍了硫酸法钛白粉生产工艺和污染物产生环节，详细阐述了生产废气、废液和废渣的特性和种类，从污染物综合治理的角度分析了“三废”治理的技术路线，重点阐述了煅烧尾气、酸解尾气和酸性废水治理措施以及废酸和硫酸亚铁的综合利用情况。     

超临界二氧化碳在环境保护中的应用

超临界CO2具有气体的低粘度、高扩散系数和液体的高密度特性，且具有化学惰性，无毒、无腐蚀性，临界状态容易实现，是一种性能优良的环境友好溶剂。文章概述了超临界CO2在去除环境污染物、取代传统工艺助剂或溶剂以减少有机物和废水排放以及分析测试等方面的应用。     

Reduction in global habitat loss from fossil-fuel-dependent increases in cropland productivity

Terrestrial biodiversity loss and climate change, driven mainly by loss of habitat to agriculture and fossil fuel (FF) use, respectively, are considered among the world's greatest environmental threats. However, FF-dependent technologies are currently essential for manufacturing synthetic nitrogen fertilizers (SNFs) and synthetic pesticides (SPs) critical to increasing agricultural productivity, which reduces habitat loss. Fossil fuel use increases CO₂ levels, further enhancing agricultural productivity. Based on estimates of global increases in yields from SNFs, SPs, and atmospheric CO₂ fertilization, I estimated that FF-dependent technologies are responsible for at least 62.5% of current global food production (GFP) from cropland. Thus, if FF use is eschewed in the future, maintaining current GFP means croplands would have to increase from 12.2% of global land area (GLA) excluding Antarctica to 32.7%. The additional 20.4% of GLA needed exceeds habitat lost currently to cropland (12.2% of GLA) and cumulative conservation areas globally (14.6% of GLA). Thus, although eliminating FF use could reduce climate change, its unintended consequences may be to significantly exacerbate biodiversity loss and indirectly increase food costs, reducing food security which, moreover, disproportionately affects the poor. Although it may be possible to replace SNFs and SPs with FF-free technologies, such substitutes have not yet been demonstrated to be sufficiently economical or efficient. In the interim, meeting global food demand and keeping food prices affordable would increase habitat conversion and food prices. These trade-offs should be considered in analyses of climate change policies.