Thermal cracking of oils from waste plastics

Thermal cracking of decomposed waste plastic oil produces a good yield of olefins. The solvent extraction of such waste plastic oil seems to be efficient for increasing gas yields and recycling monomers. To assess the potential of monomer recovery from municipal waste plastics, the oils were cracked using a laboratory-scale quartz-tube reactor. The waste plastic oils were provided by two commercial plants of the Sapporo Plastic Recycle Co. and the Dohoh Recycle Center Co. in Japan. A model waste plastic oil made in a laboratory was also examined. Yields of ethene, propene, and other products were measured at different temperatures. Two-step pyrolysis reduces coking compared with the direct thermal degradation of plastics. The raffinates from waste plastic oils extracted by sulfolane were also cracked. The primary products were almost the same as those from nontreated oils. The maximum total gas yield was 78wt%–85wt% at 750°C, an increase of about 20wt% compared with that of nonextracted oil. Solvent extraction removes stable aromatic hydrocarbons such as styrene, which is more coked than cracked.     

废塑料处理技术进展与展望

文章介绍了解决废塑料污染的几种方法，分析了目前我国废塑料回收利用技术的现状，并介绍作者在这方面进行的一些新的研究工作：（1）使用自制的催化剂完成了聚烯烃类塑料催化热解回收燃料油的小试，获得了较好的效果；（2）通过实验对发泡聚苯乙烯热解回收苯乙烯单体的工艺流程提出了优化操作条件。根据国内外实际，文章最后对废塑料回收利用提出了几点建议。     

小型废弃电器电子产品精细拆解与资源化利用初步探讨

随着工业化进程和社会生活的丰富,各种小型电器电子产品不断问世,相关废弃产品的拆解和资源化利用已经成为资源综合利用的重要课题.基于其分类与回收利用现状,就国内精细拆解与资源化利用问题进行了探讨,并以废弃手机为例,就处理原则、工艺流程设置和高值利用方法提出了一些建议.     

镁合金在笔记本电脑外壳材料替代中的环境协调性评价

本文应用生命周期评价，（life cycle assessment，LCA）方法，对镁合金以及塑料这两种笔记本电脑外壳进行了初步评价和比较，结果表明镁舍金能源消耗、温室效应方面为塑料的556．31％、383．30%。但在材料的性能、资源消耗、酸化效应、生态毒理、材料的再生性等方面明显优于塑料。     

杂质对废塑料裂解产物及污染物排放的影响

从垃圾中分选出的废塑料混有大量杂质,杂质对现有废塑料裂解工艺有直接的影响.针对这一问题,对混有厨余、纸、织物和渣土等杂质的废塑料裂解产物和污染物排放进行了研究.同时检测和分析了厨余、纸、织物和沙土等常见杂质所含N、Cl、S元素向裂解油、裂解气中的迁移规律.研究表明,厨余的混入将对裂解油的产物产生严重不利影响,如热值降低至27 MJ/kg,油品的含水率高达25%以及多环芳烃含量大大提高,因而应在分选过程中除去.厨余、织物和纸张等杂质的混入导致裂解气体中污染物浓度的显著上升.渣土的混入对气体产物有有利影响,对油品无明显不利影响.     

Optimization of the high-pressure, near-critical liquid-based microsortation of recyclable post-consumer plastics

High-pressure, near-critical liquids were used as float-sink separation media for the microsortation of polyolefin mixtures and PET/PVC mixtures. Near-critical carbon dioxide was used for the refinement of the polyolefins, and sulfur hexafluoride was used to separate post-consumer PVC from PET. Preliminary experiments indicated that there was no overlap in the density ranges of post-consumer HDPE, LDPE and PP containers. There was no overlap in the PET and PVC densities, with the exception of a single PVC packaging material with a density in the PET range. These initial results indicated that a float-sink separation was a viable means of microsortation. Separations of 91% LDPE (1/8′ beads)/9% PP (1/8′ chopped strands) resin mixtures and mixed post-consumer polyolefin flakes were then conducted in a laboratory-scale, 1-I batch apparatus. This apparatus not only permitted the observation of the separation, but also enabled the separated fractions to be removed from the high-pressure environment. The results indicated that LDPE purity of greater than 98.9% was obtained in 3 min or less if (a) the fluid density was 0.018 g/cm³ greater than the PP density and only 0.002 g/cm³ less than the LDPE density, thereby providing the greatest buoyancy force for the removal of the PP, (b) the fluid was recirculated upward through the bed of mixed plastics, facilitating the upward movement of the PP, and (c) the loading was kept at levels below 40% by volume. HDPE purity of 99% was also attained with clean, dry, post-consumer mixed plastic flakes. The loadings for these separations were very low, however, due to the difficulty in agitating the mixed bed of plastics using fluid recirculation. An economic analysis of these microsortation processes indicated that the value of the sorted plastics relative to the mixed feed must increase by approx. $0.08/lb for the CO₂-based separation and approx. $0.27/lb for the SF₆-based separation to justify the implementation of these high-pressure processes.     

Preliminary Studies on Converting Agricultural Waste into Biodegradable Plastics—Part IV: Polysaccharide Containing Natural Materials

Corn distillers’ dry grain, corncob powder, hardwood powder, and sugar beet pulp were separately anionized by oxidation with sodium hypochlorite in aqueous solution. Solid reaction products instantly precipitated upon admixing each of the above-oxidized materials with soy protein isolate. Infrared spectra and differential scanning calorimetry supported the hypothesis that soy protein isolate complexed with all of the above-oxidized polysaccharides. Reaction products with either oxidized corn distillers’ dry grain or oxidized sugar beet pulp provided hard, brittle pellets with tensile strengths as high as 9.5 MPa, suggesting that these materials could be viable as biodegradable plastics.     

报废汽车内饰件塑料浮选技术研究

报废汽车内饰件塑料品种复杂、难以分选,为此,以分离汽车内饰件中4种主体塑料——PP(聚丙烯)、ABS(丙烯腈-丁二烯-苯乙烯)、PC(聚碳酸酯)、PVC(聚氯乙烯)为目标,利用实验室自制浮选设备,考察了浮选液流量、溶气罐压力、润湿液浓度等因素对浮选效果的影响. 结果表明:当溶气罐压力为0.22 MPa、浮选液流量为10 L/min、润湿液中ρ(单宁酸)为15 mg/L时,一级浮选PP、ABS、PC、PVC效果达到最佳,其中PP和ABS为上浮料,二者上浮率分别为100%和98.63%;PC和PVC为下沉料,二者下沉率分别为98.95%和100%. 当溶气罐压力为0 MPa、浮选液流量为6 L/min、润湿液中ρ(单宁酸)为10 mg/L时,二级浮选完全分离PP/ABS;当溶气罐压力为0.24 MPa、浮选液流量为10 L/min、润湿液采用10 mg/L单宁酸和10 mmol/L癸二酸二丁酯时,二级浮选分离PC/PVC效果达到最佳,PC上浮率为92.87%,PVC下沉率为91.41%. 通过二级浮选分离,PP、ABS、PC、PVC的最终分离率分别达到100%、98.63%、92.87%和91.41%,显示出该二级浮选工艺在报废汽车内饰件塑料分选方面具有较为广阔的应用前景.      

某电子垃圾拆解园周边农田土壤中多环芳烃的污染特征及风险评估

研究了某电子垃圾拆解园周边151个农田土壤样品中16种多环芳烃(PAHs)的污染特征和环境风险。结果表明,125个表层土壤样品中PAHs总质量浓度在149.0~2.0×104μg/kg,均值为1 805.5μg/kg,随着剖面土壤深度增加,PAHs含量总体呈递减趋势。通过来源解析,电子拆解园周围土壤中PAHs污染主要由废弃的电子电器元件的粗放燃烧和汽车尾气排放共同引起。土壤风险评估表明,7种类二噁英毒性PAHs的毒性当量(TEQPAH)在6.000×10-5~0.689pg TEQ/g,平均值为0.015pg TEQ/g;苯并(a)芘、二苯并(a,h)蒽、苯并(a)蒽、苯并(b)荧蒽、茚并(1,2,3-cd)芘致癌风险率超出百万分之一的样本比例分别为20.53%、6.62%、1.99%、2.65%、2.65%,其中采样点1、68两个点位表层土壤的苯并(b)荧蒽致癌风险率超过了万分之一。