Adsorption Equilibrium of Volatile in Condensed ModePolyethylene Process

In this paper n-hexane is chosen as typical volatile in condensed mode polymerization process, and the adsorption equilibrium of volatile in polyethylene pva‘ticles is studied through experiments at different temperatures, pressures and particle diameters. It is found that more adsorbed quantity of volatile at equilibrium can be obtained with lower temperature, higher pressure and smaller particle diameter. Under polymerization conditions,the adsorbed quantity at equilibrium is more strongly affected by temperature than by pressure, and if the diameter distribution of particles is very wide the effect of diameter on the adsorbed quantity must be taken into consideration.With theoretical analyses a model is proposed for calculating the adsorbed quantity of volatile at equilibrium.     

生物通风修复多种有机污染物体系的模拟分析

针对多污染物体系的生物通风修复过程，对生物通风（bioventing, BV）操作中的空气注入方式，单井修复还是多井修复及生物降解作用用BIOVENT软件进行了模拟，系统研究了各种操作条件对修复效果的影响。模拟研究结果表明：BV修复现场采用间歇注入的操作方式，其处理效果与连续注入方式相似，且可减小操作费用；在受污染区域小的现场采用单井修复较为合适，而当受污染区域远大于单井影响半径时，应采用多井修复才能够达到较好修复效果；BV修复前期宜使用较大空气速率来加快挥发性有机污染物的挥发速率，后期则宜采用较小空气速率以充分利用微生物降解作用去除土壤中残留污染物。     

高温陶瓷过滤管性能退化建模及实时寿命预测

高温陶瓷过滤管由内部孔径较大的支撑体和外部孔径较小的过滤膜双层结构构成,在实际应用中,存在大量粒径较小的粉尘颗粒,会穿过过滤膜沉积到支撑体内部,脉冲反吹无法有效清除. 因支撑体内颗粒沉积及管壁外残余粉尘层不断压缩,使陶瓷过滤管渗透率不断下降,残余压降逐渐增加。本工作基于高温陶瓷过滤管壁内颗粒沉积特性及残余粉尘层压缩不可直接观测的特点,结合贝叶斯估计理论,利用过滤管运行期间采集的残余压降数据,提出一种基于状态空间模型的过滤管性能退化建模方法。该方法能融入最新采集到的残余压降数据,实时对模型参数进行更新,可对陶瓷过滤管的剩余寿命进行实时预测,同时对陶瓷过滤管剩余寿命的失效概率密度分布及陶瓷过滤管的退化状态变化率进行预测。对某高温试验装置及壳牌煤气化装置中的陶瓷过滤管残余压降分析表明,预测剩余寿命准确率随残余压降数据增加而逐渐增加,后期预测准确率高于95%,且陶瓷过滤管退化状态变化率逐渐变小,与陶瓷过滤管残余压降前期增加快后期增加慢的现象一致。     

Desorption of VOC from polymer adsorbent in multistage fluidized bed

The desorption process of volatile organic compounds(VOC) from a polymer adsorbent in counter-current multistage fluidized bed was studied. And a mathematical model considering the mass transfer dynamics was developed, which was validated from experiment data. The gaseous ethyl acetate mass transfer was discussed, and the limiting step is the intraparticle mass transfer of the desorption process. The value of intraparticle mass transfer coefficient is between 1.85 × 10~(-6) and 1.38 × 10~(-5) m·s~(-1) under temperature of 100–160 °C. Experiments under different operating conditions were carried out. The effects of operating conditions such as gas–solid flow ratio,gas inlet temperature and total stage number of multistage fluidized bed on outlet VOCs concentration and desorption efficiency were discussed. The maximum outlet VOCs concentration and corresponding desorption efficiency of the multistage fluidized bed desorber was calculated under different gas inlet temperatures and total stage numbers.     

冷冻干燥过程强化中冷冻阶段优化的研究进展

冷冻干燥产品质量高,但时间长、能耗高。本文综述了冷冻干燥过程强化中冷冻阶段的优化方法,控制冷冻速率、调节冰晶成核和退火处理可以获得大而均匀的冰晶从而提高升华干燥阶段速率,但物料内部比表面积的减小会降低解吸干燥阶段速率,这类常规的冷冻阶段优化方法对弱吸湿性的物料有一定的强化效果。有机溶剂具有较高的蒸气压,作为共溶剂时可以增加传质推动力,但较低的有机溶剂残留量要求阻碍了其进一步应用。“初始非饱和多孔介质冷冻干燥”的技术思想是将液体物料首先制备成具有一定初始孔隙的冷冻物料,然后再进行冷冻干燥。物料具有的初始孔隙为水蒸气的迁移提供了便捷的通道,而且纤薄的固体基质也有利于结合水的解吸,可以同时强化升华干燥阶段和解吸干燥阶段。该技术思想是过程低消耗和产品高质量的完美结合,为解决冷冻干燥过程速率低的问题提供了新的方案。     

袋式过滤器过滤初期阶段滤袋压力特性的实验研究

针对袋式过滤器过滤初期阶段的压力特性,选用高密度聚乙烯粉料进行了实验分析,主要考察过滤速度和入口浓度对滤袋压降的影响。实验结果表明,在过滤初期阶段滤袋的压降上升趋势很明显,这种压降的增大主要来自于残余压降;滞留在滤料内的粉尘改变了滤料内部的流道结构,从而导致了滤袋残余压降的不断升高;过滤速度和入口浓度的增加均可使残余压降增大。最后通过压降组成的分析,提出了滤袋总压降的计算模型。     

硫酸盐制浆过程中硫的分布与变化规律

本文研究了兴安落叶松硫酸盐制浆过程中流在蒸煮液、溶出木素和残余木素中的分布及变化情况。结果表明，蒸煮过程中蒸煮液的活性碱和硫化钠浓度不断下降，硫化度则不断上升，活性碱与硫化钠的消耗主要发生在初始脱水素阶段．溶出木素的含硫量在初始脱木素阶段量最高，随着蒸煮反应的进行，其百分含量逐渐下降，但绝对量却不断上升。蒸煮结束时，约占总用硫量1／5的硫与溶出木素结合在一起。木片或纸浆的含硫量与木素的硫化速率和残余木素的含量密切相关。在残余脱木素阶段，残余木素的硫化对木素的说除已没有促进作用。     

气相法聚乙烯冷凝模式操作的模拟研究(Ⅰ) 反应器运行状态的分析

建立了气相法聚乙烯冷凝模式操作反应器的两相模型 .模型涉及气泡相和乳化相中的热量和质量守衡、乳相和泡相之间的热量传递和质量传递、乳相中的聚合反应以及乳相中粒子的停留时间分布等 .通过模型研究了常规操作和冷凝操作时操作变量和反应器运行状态变量之间的关系 .模型模拟结果与工业的常规操作和冷凝操作数据符合较好 .得到了冷凝操作时时空收率、低温区域、聚合物灰分等的变化规律以及催化剂特性对冷凝操作的影响规律 .提出了适合于冷凝操作的催化剂类型     

Kinetics and chemical reactions of acetaldehyde stripping and 2‐methyl‐1,3‐dioxolane generation in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) resins were air stripped at temperatures from 160 to 190°C to monitor changes that occur during reduction of residual acetaldehyde (AA) concentrations. During this process diffusion and generation of AA, 2‐methyl‐1,3‐dioxolane (2MD), ethylene glycol (EG), and water occurred as the molecular weight and crystallinity increased through complex chemical reactions involving polymerization, formation of by‐products, and some degradation at higher temperatures. This process was characterized in terms of time and temperature of stripping, with determination of residual concentrations of AA and other less volatile compounds such as 2MD and EG. Residual AA concentrations continually decreased from their initial values, while concentrations of 2MD decreased initially, then increased, and later decreased with time. Empirical rate constants for resin solid‐state polymerization were determined at the air‐stripping temperatures, and free EG concentrations as well as intrinsic viscosity, density, crystallinity, and color were monitored to aid in studying the kinetics of AA removal. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

A non-Markovian model of desorption

The desorption kinetics of small hydrocarbon molecules in a low-density polyethylene (LDPE) film has been simulated via the continuous time random walk approach. A scaling relation between the amount of penetrant remaining in the film during the final stage of the process and the time has been obtained. A constant scaling exponent was obtained for various hydrocarbon penetrants in LDPE. The mutual relation between phenomenological and statistical models has been exploited.     

Classification of volatile products evolved during temperature-programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP)

Temperature programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP) was investigated. The aim of this research was to determine the volatile product distribution and product evolution rate of co-processing of LDPE with PP. A series co-pyrolysis operation was performed with LDPE and PP using a 1:3, 1:1, 3:1 total carbon ratio of LDPE to PP. A fixed bed reactor was used to pyrolyse small sample of LDPE and PP mixture under an inert gas flow (argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analyzed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. n-paraffins and 1-olefins in aliphatic fraction of co-pyrolysis products were classified as a carbon number. In addition, the recovery of total organic carbon as an organic volatile product was determined. The assessments were based on incorporating the results on temperature-programmed pyrolysis of LDPE and PP. The effect of co-processing of LDPE with PP was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. Conversion into volatile hydrocarbons was found to be higher, with the increasing PP ratio in the co-pyrolysis operation.     

Polyethylene exposed to liquid propane: Sorption and permeation kinetics and mechanical properties

Data obtained by sorption and permeation measurements of liquid propane in medium-density polyethylene were analyzed with an analytical diffusion model, assuming a constant diffusion coefficient, and a numerical model, based on the free volume theory of Fujita. The stress-strain properties of propane-swollen medium-density polyethylene were recorded in an Instron tensile tester. The sigmoid sorption curves (modeled here for the first time) were adequately described using nonstationary boundary conditions. The numerical model was capable of representing sorption, desorption, and permeation data, whereas the analytical technique gave satisfactory results only for sorption/desorption data in the initial, transient stage. The difference between diffusion coefficients determined from sorption and desorption measurements and the time dependence of the modulus-solute concentration relationship can be explained by assuming a relaxation of constrained amorphous chain segments. The penetrant-induced structure rearrangement is, according to differential scanning calorimetry measurements, confined to the amorphous phase.     

吸收稳定系统解吸塔双股进料工艺的探讨

以石家庄炼油厂技术改造为背景，通过正交设计法与模拟计算相结合，对解吸塔双股进料工艺进行了分析。结果表明：该工艺最佳操作条件为加热股流量取２／３，进料温度９０℃，进料位置Ｎ＝１０。在此操作条件下的双股进料工艺与原工艺模拟结果比较表明：能耗比原不加热单股进料工艺降低了３９％，解吸气量比原加热单股进料工艺降低了５６％。     

UNIPOL聚乙烯装置开车过程中静电状态下冷凝操作的应用

阐述了UNIPOL聚乙烯装置开车期间,反应器内有静电时,进行冷凝态切换的过程。工业应用结果表明,通过充分的技术准备,制定详细的切换步骤,严密的生产操作,可以在开车初期注水控制静电的状态下,成功使反应器进入冷凝操作模式,极大的提高了开车成功率,迅速地恢复了生产的稳定。     

新无卤膨胀型阻燃剂的应用与研究

建立分阶段无卤膨胀阻燃新模型,燃烧初始,温度较低阶段以气相阻燃作用为主,燃烧后程凝聚相阻燃作用为主,避免了不同阻燃机理的相互干扰,通过前期释放大量不燃气和后期形成致密膨胀炭层,解决了阻止熔滴和玻纤增强材料的“烛芯”难题。在聚丙烯中的应用实验表明阻燃性能良好,添加24%阻燃达到UL94-V01.6mm,燃烧过程无滴落,炭层致密,比传统IFR热释放速率峰值下降30%;在玻纤增强体系,25%达到UL94-V01.6 mm,30%GFFRPP机械性能比传统IFR提高10%~15%。同时在弹性体TPE中进行应用实验,实验表明阻燃性能良好,添加28%,达到UL94V-0,氧指数32%、稳定通过VW-1测试;与传统APP阻燃体系对比,产品相容性好,表面光滑,无白点。     

恒热流条件下亲疏水表面液滴蒸发特性

以恒热流方式结合高速摄影技术同步观察记录3 μl的小液滴在不同亲疏水表面的蒸发过程。通过一系列的对比实验观察记录了不同亲疏水表面液滴蒸发时接触角、接触直径、蒸发时间等的动态特性。从实验分析中可以看出亲水表面液滴蒸发速率比疏水表面上液滴蒸发速率快,并且随着热通量的增大,液滴蒸发速率增大。在恒热流条件下亲疏水表面液滴蒸发以CCR模式为主,在蒸发后期呈现混合蒸发模式,全程未出现CCA模式。     

The effect of short-chain branching on the thermolysis/reactive distillation of polyethylene

Thermolysis, coupled with reactive distillation, was investigated as a process to convert waste olefin-based polymers into value-added products. The degradation of two types of polyethylene, linear low and high density, was investigated. The initial molecular structure of the polymer was found to have a large effect on the rate of molecular weight reduction. The linear low-density polyethylene started to produce volatile products earlier and at a faster rate than the high-density polyethylene. Preferential scission of the side branches from the linear low-density polymer backbone was shown to be one of the first steps of the degradation mechanism. Once the branches were stripped from the linear low-density polyethylene, the degradation products were similar to those produced from high-density polyethylene. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1415–1421, 1999     

Desorption of residual monomer from PVC resins in a fluidized bed drier

The present study deals with the investigation of the desorption of vinyl chloride from various commercial and experimental suspension PVC resins in a laboratory fluidized bed drier simulating an industrial drier. The results show that PVC resins may differ widely in the rate at which the monomer is desorbed. The rate of diffusion of the monomer is a function of the drying time, the fluidization air temperature, the porosity, and the amount of glassy particles in the PVC. The residual monomer content decreases with increasing air temperature, drying time, and resin porosity. After 105 min of drying with hot air at 80°C, the residual monomer content in the grade with the highest porosity is reduced from 3400 to 2 ppm, whereas for the grade with the lowest porosity, it is reduced from 4300 to 172 ppm on a dry basis. It appears that the resins of the high molecular weight grades are more porous and the low molecular weight grades contain a high proportion of nonporous or glassy particles and, hence, the desorption rate is smaller in these grades. The proportion of glassy particles and the size of glassy domains are estimated in this study by applying the experimental desorption data at long times to a desorption model. The model is useful in differentiating the interior structure of various PVC grades. © 1994 John Wiley & Sons, Inc.     

聚乙烯技术新进展

评述了双峰聚乙烯技术,茂金属催化剂和采用液态冷凝技术的乙烯气相聚合工艺的新进展。介绍了生产双峰聚乙烯产品的各种双反应器工艺和单反应器工艺,指出双反应器工艺是目前国际上采用最广泛的工艺,而单反应器工艺目前仍处于开发试验中,是生产双峰聚乙烯产品未来发展方向。液态冷凝气相聚乙烯工艺利用冷凝液体的蒸发潜热及时移走反应热,极大地缓和了反应器散热问题,使得反应器单位体积的聚乙烯产量得到大幅度提高。将液态冷凝技术与超高活性的茂金属催化剂配合使用是当今研究的一个热点。     

Activated carbon cloth adsorption-cryogenic system to recover toxic volatile organic compounds

There is an emergent need to reduce the emissions of toxic volatile organic compounds (VOCs) to the atmosphere. One strategy to reduce the emissions of VOCs from point sources is to use air pollution control devices on the sources' discharge streams. This paper describes the development of a new activated carbon cloth (ACC) adsorption system that is integrated with cryogenic vapor recovery to reduce the amount of VOCs emitted to the atmosphere from point sources and provide for reuse of the VOCs that are recovered. Electrical current is used to regenerate the ACC. ACC adsorption followed by electrothermal regeneration results in formation of a concentrated organic vapor which is cryogenically condensed from the gas phase. Electrothermal desorption allows for careful control of the desorption time and the concentration profile of the desorbed VOC to allow minimal use of cryogen. Adsorption, followed by cryogenic treatment enables VOC sources to meet air quality control regulations while providing a high quality liquid VOC product for reuse.