Analysis of Products Generated from the Thermal and Catalytic Degradation of Pure and Waste Polyolefins using Py-GC/MS

The possibility of transforming waste plastics into valuable hydrocarbons via catalytic cracking and reforming is attracting increasing interest. Pyrolysis coupled with Gas Chromatographic separation and Mass Spectrometry detection (Py-GC/MS) has been used in this work to study the product selectivity of various catalysts in the conversion of pure and residual polyethylene samples into hydrocarbon products. Five acid solids of comparable aluminium contents but different textural and acid properties were tested as catalysts, including three zeolites (standard ZSM-5, nanocrystalline n-ZSM-5 and Beta) and two mesostructured solids (Al-MCM-41 and Al-SBA-15). Thermal cracking of the pure and residual polymers generated a similar range of products to each other, with a high proportion of linear paraffins and olefins of varying lengths. The presence of zeolitic materials resulted in complete elimination of heavy linear products, an increase in the light hydrocarbon fraction and a marked selectivity towards the formation of single-ring aromatic species, particularly benzene, toluene and xylene. Aromatic formation was particularly notable with the small crystal size n-ZSM-5 (aromatic selectivity up to 53.9%) and less marked in the case of standard ZSM-5 (up to 36.4%) and Beta zeolite (up to 35.0%). Mesostructured catalysts like Al-MCM-41 and Al-SBA-15 favoured the production of light C₂–C₅ hydrocarbons (up to 57.9%) while the formation of aromatic products was significantly lower than with zeolitic materials. The paper examines the extent and the causes for this product selectivity and discusses its connection with the acid and textural properties of each catalyst. It was also observed that, under the experimental conditions employed, the products generated were not significantly affected by the nature and origin of the polymers employed.     

高寒地区热水锅炉锅内加药水处理

通过热水锅炉内加药水处理的工作实践帮对易产生结垢的原因分析,提出了高寒地区热水锅炉锅内加药水处理的可行性和具体实施方案。     

湿热环境下配电自动化终端的腐蚀失效分析

目的解决配电自动化终端在湿热环境下的腐蚀失效问题,保障配网自动化系统的安全运行,延长配电自动化终端的使用寿命。方法分别选用三台架空终端FTU作为研究对象,研究配电自动化终端在湿热环境下的腐蚀失效特点,并提出针对性防护措施。采用SEM和EDS表征方法展开配电自动化终端的腐蚀失效分析。结果由EDS数据结果发现,相比较于轻微腐蚀区域,腐蚀区域的氧含量均大幅增加,且出现硫元素和氯元素,表明腐蚀环境主要是含硫和氯的潮湿环境。航空插头表面覆盖镍和铜两层镀层,腐蚀后的试样表面不仅检测到铜,有的甚至检测到基材铁,说明腐蚀后镀层已逐步失效,部分基材裸露,且已开始腐蚀。结合SEM发现,样品表面有大量颗粒粗大的腐蚀产物,且明显看出镀层已被破坏。结论材料腐蚀失效主要是由于高温度、湿度、含氯及硫等大气环境加速终端设备腐蚀,以及镀层被破坏或漏镀等问题造成基材裸露,腐蚀进一步深入发展。因此,根据湿热环境下配电自动化终端的腐蚀特点,提出针对性的防护措施。保障配网自动化系统的安全运行的同时,延长配电自动化终端的使用寿命,为今后的实证测试提供可靠依据。     

济钢210t转炉钢水罐热修除尘系统的设计及应用

介绍了钢水罐热修除尘系统的自主开发,除尘技术的设计,详细阐述可移动抽风罩、抗结露袋除尘器、覆膜玻璃纤维膨体纱等技术特点,以及整个除尘系统的控制技术,仅供同行参考借鉴。     

Cardiovascular Load During Summer Work of Two Age Groups of Van-Rickshaw Pullers in West Bengal,India

Van-rickshaw is a popular mode of transport of people and merchandise in developing countries. The purpose of this study was to assess the effect of age on cardiovascular load of van-rickshaw pullers in the summer season (March-June) in real situations. In 142 participants, divided into 2 age groups (25-40 and 41-55 years), cardiovascular load was assessed on the basis of working and partial recovery heart rate (HR), predicted maximal HR, working maximal HR, average working HR, percentage of reserved HR, sum of recovery heart beats, percentage of recovery, relative and net cardiac cost, etc. Except for percentage of recovery, all parameters differed significantly between the groups and were significantly correlated with age. As this activity is very stressful, it places a heavy demand on the cardiovascular system. Therefore, age is an important factor for sustainability of the work, especially in a hot environment. Some ergonomic interventions are necessary to reduce cardiovascular load.     

基于氮吸附、压汞联合试验的CO2致裂对煤岩孔隙的影响

煤岩中的孔隙结构特征对瓦斯运移和富集有着至关重要的影响。为了研究CO₂致裂对煤岩孔隙的影响,利用低温氮吸附试验与压汞试验相结合的方法对致裂前后的煤岩孔隙变化进行定量表征,并使用扫描电镜、现场致裂后煤岩瓦斯抽采分别从定性和宏观上反映CO₂致裂对煤岩孔径分布和孔隙结构特征的影响。结果表明,CO₂致裂会迫使煤岩中微孔、小孔孔隙结构改变,从墨水瓶形孔转变为开放型孔隙,各孔径段孔容有所增长扩张,致裂主要迫使孔径在10 000~100 000 nm的孔隙有较为明显的发育扩张。煤岩中存在渗流孔隙和扩散孔隙,致裂后渗流孔体积和百分比呈现先增长后逐步降低的现象,扩散孔体积变化趋势与渗流孔一致,但其百分比先降低后逐步回升。通过扫描电镜、现场测定及计算等辅助手段从宏观方面反映出CO₂致裂对孔隙有明显作用,对消除煤与瓦斯突出有积极效果。     

乙烯装置裂解炉操作的危害分析及对策

分析识别乙烯装置裂解炉操作中的危害因素,制定了确保裂解炉安全运行的对策.     

天津市热镀锌企业清洁生产审核实践探索

以热镀锌企业清洁生产审核为例,归纳审核技术要点,总结了天津市第一批重点企业实施清洁生产审核的经验。     

中国南北过渡带生态系统碳储量时空变化及动态模拟

山地是全球变化的敏感地带,对生态安全与发展具有重要作用,山地生态系统服务变化和生态环境承载力是地理学与生态学的研究热点。以中国南北过渡带的主体秦巴山地为研究对象,采用CA-Markov模型与InVEST模型模拟和预测（2000—2040年）不同土地利用情景下秦巴山地生态系统碳储量变化,运用热点分析（Getis-Ord G_i^*）探讨秦巴山地生态系统碳储量的空间分布差异。结果表明：（1）2000—2040年,研究区土地利用/土地覆被变化主要是耕地、林地、草地和建设用地。（2）2000—2020年,碳储量增加1.12×10⁷ t;2020—2040年自然增长情景下,碳储量损失剧烈,减少50.24×10⁷ t;生态保护情景下,碳损失幅度明显变弱,减少29.52×10⁷ t,说明采取生态环境保护政策,能够有效控制碳储量减少。（3）土地利用/土地覆被与生态系统碳储量的变化呈现显著的一致性,土地利用数量变化决定了生态系统碳储量的质量和空间分布格局。（4）随着海拔抬升,碳储量呈现出“先增后减”的趋势;随着坡度升高,碳储量呈现出“W”型变化趋势。（5）热点分析结果显示,2000—2020年间,碳储量热点区和冷点区零散分布在研究区内;2040年自然增长情景下,碳储量冷热点分布范围有逐渐变大的趋势;2040年生态保护情景较2020年,秦巴山地生态系统碳储量的冷热点分布范围整体变化不大。