浅析直纺长丝熔体输送及分配系统

简要介绍了直纺长丝熔体输送及分配系统,讨论了不同设备配置和分配方案对熔体输送及分配系统的影响,并对熔体温度的控制方案进行了说明,为直纺长丝熔体输送及分配系统的工艺方案选择提供依据.     

直纺涤纶长丝熔体输送温度波动原因及处理

洛阳石油化工总厂聚酯装置采用杜邦技术；直纺涤纶长丝装置采用日本东丽公司技术。从聚酯终聚釜出来的熔体经过熔体冷却器、熔体过滤器后送至长丝装置的熔体分配四通阀，再经3台熔体增压泵增压后送至12条长丝生产线。从熔体四通阀至12条生产线的分配管线之间的熔体管道的保温热媒是长丝装置的3台热媒脱过热器提供。熔体输送温度一般控制在285℃左右。2000年开工至今，曾经发生熔体输送系统温度较大的波动，熔体温度较大的波动影响产品质量，甚至可能造成增压泵跳停事故。     

PP-R双螺杆挤出熔体输送和降解行为的研究

对无规共聚聚丙烯(PP-R)在ZSK-300型双螺杆挤出机中熔体输送特性和热降解行为进行了研究,计算了ZSK-300的最大挤出量．分析了熔体输送流场;并对加料量、熔体流动指数、助剂量、熔体温度等工艺操作条件对熔体输送和降解行为的影响进行了讨论。结果表明,加料量的改变需要适当调整加热温度：粉料熔体流动指数的微小波动,对挤出物的质量和挤出过程的稳定性没有影响;降低熔体挤出温度,可明显降低PP-R的热氧降解。     

吸湿排汗抗菌POY135 dtex/72 F涤纶 长丝生产工艺探讨

银系PBT载体抗菌母粒通过低露点干空气加温干燥、螺杆挤压熔融、注射泵计量进入熔体管道和PET熔体进入高效动态混合器,混合均匀抗菌改性PET熔体输送至纺丝箱体计量、冷却、上油、卷绕等。采用"十"字形喷丝孔,纺制吸湿排汗抗菌POY涤纶长丝,研究纺丝工艺条件对吸排抗菌涤纶长丝指标的影响,经过试验,采用纺丝箱体281℃、风压30 Pa、卷绕速度2 875 m/min得到性能良好的吸排抗菌POY涤纶长丝。     

熔体直纺涤纶长丝装置熔体输送系统的工艺设计

以24头/位熔体直纺涤纶长丝装置为例,探讨了装置中熔体输送系统的设计技术要点和设计方法。结果表明:熔体输送系统的设计中,确保管道长度、管径以及熔体的流速、平均停留时间、压力降和温升等在最佳值或合理的范围,才能满足纺丝生产要求;在熔体输送配管中间增加增压泵,可使聚酯熔体进入计量泵前的熔体压力在6 MPa以上;聚酯熔体在输送过程中,除了压力降引起温升变化外,熔体通过增压泵和计量泵也会引起温升变化,可在增压泵后加装熔体冷却器将熔体温度控制在280~292℃。     

直纺32头43 dtex/72 f涤纶FDY细旦丝生产

采用熔体直纺工艺路线,对32头纺FDY 43 dtex/72 f细旦涤纶长丝的生产工艺技术进行了研究,着重介绍了直纺装置侧吹风条件下熔体输送工艺及纺丝组件过滤要求、喷丝板孔径选择、缓冷器温度影响、侧吹风冷却条件、热辊拉伸等生产工艺技术,通过设备改造与工艺条件的控制,成功在侧吹风装置上开发出32头细旦FDY涤纶系列长丝产品,品质优良。     

对PET短纤维直接纺丝熔体输送工艺条件的探讨

根据ＨＶ系列年产１．５万ｔ涤纶短纤维的生产实践，结合传热和流体输送的有关理论，对连续聚合直接纺丝装置的熔体输送过程的熔体停留时间、熔体温度控制和熔体压力设定等方面进行了系统讨论，提出熔体在输送管道中的停留时间应根据温度和熔体特性决定；熔体温度可用静态混合器来调节；用输送过程的熔体热降解程度和熔体温度分布及变化作为评价熔体输送系统优劣的标准。     

涤纶长丝装置改纺锦纶长丝

将涤纶长丝装置改纺锦纶长丝 ,着重介绍了装置的切片输送加料系统、纺丝部分的单体抽吸装置及熔体预过滤器、卷绕头部分的电器仪表和压缩空气系统等设备的改造 ,改造后的装置可生产 90～ 186dtex锦纶长丝 ,且 POY合格品率大于等于 99.8%。     

熔体三通阀的在线维护及检修

由于直纺长丝对聚酯熔体的质量要求较高,同时也是为了延长纺丝组件的使用周期,在熔体输送系统中增加了一套熔体过滤器。　　仪征化纤股份有限公司9万ｔ聚酯熔体直纺长丝装置熔体过滤器采用美国ＭＥＭＴＥＣ公司生产的连续过滤器。1台熔体过滤器有2套过滤腔体,一用一备。当过滤器使用一段时间后,由于滤芯微孔被熔体杂质堵塞,其进出口压差超过一定数值时就需要手动切换,过滤器启用备腔,而另一腔内过滤器滤芯拆卸清洗。　　熔体过滤器通过进出口手动三通阀进行切换。三通阀阀体为特种不锈钢制造,阀芯采用压力平衡结构,切换采用单侧手动执行…     

聚酯熔体输送泵轴承故障分析

齿轮泵在聚酯生产装置中被广泛用作熔体输送设备,其运行工况不适当,会直接影响泵的运行稳定性。从生产实践的角度,结合齿轮泵的选型要求,对后接直纺长丝的聚酯熔体输送泵频繁发生轴承抱轴故障的原因进行了分析,并提出了相应的解决方法。     

Thermal oxidation of self‐degradable composite films based on low‐density polyethylene

The effect of the structure of composite extrusion films based on a mechanical blend of low‐density polyethylene and poly(hydroxybutyrate) on the service characteristics and the kinetics of thermooxidative destruction was investigated. The aggregate state of the polymers affected the value of the boundary surface in the blend films. An increase in the latter affected the conformation states of both polymers in the blends. In this case, the strength decreased, the steam permeability increased, and the thermooxidative destruction of the polyethylene matrix during the beginning stages was accelerated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1392–1396, 2004     

Calculation of the hydrothermal long-term stability of zeolites in gas-desulphurization and gas-drying processes

The hydrothermal regeneration of water-loaded zeolitic molecular sieves in the technical processes of gas-desulphurization and gas-drying is affected by the strong attack of water molecules on the framework of the adsorbent, which results in a loss of crystallinity, corresponding decrease of sorption capacity, an increase in diffusion resistance, and finally a loss of efficiency. The destruction of a NaCa5A molecular sieve has been investigated experimentally at temperatures between 843 and 943 K and for various partial pressures of water vapour. Model equations describing the decrease of crystallinity have been obtained to discuss the dependence of the zeolite destruction on temperature, loading with water and period of treatment. For an actual process of gas-desulphurization the long-term stability of the adsorbent has been calculated and conclusions have been drawn.     

Cerium(IV)-mediated electrochemical oxidation process for destruction of organic pollutants in a batch and a continuous flow reactor

The mediated electrochemical oxidation (MEO) process with Ce(IV) and nitric acid as the oxidizing medium was employed for the destruction of various model organic pollutants in batch and continuous organic feeding modes. A near complete destruction was observed for all the model organic pollutants studied. The effects of organic concentration, temperature, concentration of Ce(IV), concentration of nitric acid and feeding time on the organic destruction efficiency were investigated. Under the experimental conditions of 80 °C and 0.95 M Ce(IV) in 3 M nitric acid, nearly 90% destruction was achieved based on CO₂ production and 95% based on TOC and COD nearly for all the organic compounds studied in batch organic addition. In the case of continuous organic addition with in situ electroregeneration of Ce(IV) by the electrochemical cell a good destruction efficiency was obtained. For long term organic feeding (120 min) the destruction efficiency was found to be 85% based on CO₂ evolution and 98–99% based on TOC and COD analyses. A model was proposed for calculating the CO₂ formation constant during the continuous process of organic addition. The model predicted a steady state CO₂ evolution pattern for the destruction process during continuous organic feeding. The experimental results obtained confirmed the predicted trends for the destruction process. The changes in enthalpy, entropy, activation energy and free energy for EDTA degradation were found to be 26.7 kJ/mol, −230 J/(mol·K), 29.7 kJ/mol, and 118 kJ/mol respectively.     

高速电镀锌用铅系阳极的破损

采用动电位曲线以及扫描电镜的方法描述了阳极的电化学行为和阳极膜的表现形貌,阳极的破损速率是用失法表示的。从试验结果来看,氧析出过电位对阳极的破损速率存在着一定的影响。     

The photocatalytic destruction of the cyanotoxin, nodularin using TiO2

Titanium dioxide (TiO₂) photocatalysis has been used to initiate the destruction of nodularin, a natural hepatotoxin produced by cyanobacteria. The destruction process was monitored using liquid chromatography–mass spectrometry analysis which has also enabled the identification of a number of the photocatalytic decomposition products. The reduction in toxicity following photocatalytic treatment was evaluated using protein phosphatase inhibition assay, which demonstrated that the destruction of nodularin was paralleled by an elimination of toxicity.     

Investigation on curing and destruction of crosslinked modified phenolformaldehyde polymers

Curing and destruction of crosslinked phenolformaldehyde polymers modified with a varying quantity of polycaprolactam were studied by means of IR and ESR spectra and by derivatography. In the curing process of the polymers, hexamethylenetetramine was found degrading, with formation of dimethyleneimine, and other groups causing spatial crosslinking of the polymers. Incorporation of nitrogen in the polymer chains was proved by means of IR spectra and elemental analysis. The activation energy of destruction was determined by the thermogravimetric curves, and it varied in the range of 25 to 32 kcal/mol. On the ground of the investigations made, it was presumed that in hardening and destruction of the polymers under study a definite role was played also by free-radical processes. An evidence of this was the presence of free radicals in the products during hardening and destruction as well as the kinetic data—the low activation energy of destruction.     

Effect of Shell Material on the Detonation of an Explosive Charge

The effect of shell material (copper and silicon carbide) on the detonation of a cylindrical explosive charge was analyzed. The wave patterns in the detonation products and the shells are substantially different, which is due to different sound velocities and the rapid destruction of the ceramic under explosive loading. The wave pattern at the explosive/ceramic interface was found to be affected by desensitization of the explosive due to its loading by an advancing wave from the shell side, resulting in a decrease in pressure, blurring of the detonation front, and an increase in particle velocity. Throughout the process, there is a continuous increase in the time of explosive decomposition near the interface between the explosive and the ceramic shell. An extended region with a constant pressure close to the Chapman–Jouguet pressure was observed on the axis of symmetry behind the detonation front of the explosive charge in the ceramic shell.     

Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process

The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant. The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III) concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction. The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction in the MEO process.     

Mediated electrochemical oxidation of phenol in continuous feeding mode using Ag (II) and Ce (IV) mediator ions in nitric acid: A comparative study

Mediated electrochemical oxidation (MEO) process is one among the latest treatment technologies for the destruction of toxic organic pollutants under ambient temperatures and at atmospheric pressure. The process is a further extension of the conventional electrochemical treatment for the removal of toxic organics with powerful mediator oxidants in acidic medium. In this report the experimental results of using silver and cerium as mediator ions were compared with respect to their electro-oxidation behavior within the limitations of each mediator metal ion and their destruction efficiencies were compared for destructing phenol in continuous feeding mode. The following conclusions were drawn: (i) the optimum nitric acid concentration was found to be 8 and 3 M and the optimum temperature was found to be 60 and 80 °C for silver and cerium electro-oxidations, respectively; (ii) in the case of Ag (II)-MEO of phenol the maximum destruction efficiency achieved was 98% at 70 °C based on CO₂ evolved; (iii) for Ce (IV)-MEO of phenol the maximum destruction efficiency achieved was 93% at 90 °C based on CO₂. The results may provide baseline information on the use of suitable mediator metal ion in treating the target organic wastes by MEO process.     

Nutritional qualities of soya protein as affected by processing

The nutritional qualities of soybean proteins are basically determined by amino acid patterns, amino acid availabilities (digestibility) and contents of biologically active components. Of these factors, the last two are most affected by processing conditions, whereas amino acid analysis is least affected, although it too may be modified in those cases in which soybean proteins are fractionated. In the preparation of the large variety of soya products presently available, soybeans are subjected to many different processes, all of which are discussed. Heat treatment appears to be the process which most affects protein nutritional quality; generally, quality first increases with heat treatment due to inactivation of biologically active factors, passes through a maximum and then decreases due to destruction and/or inactivation of essential amino acids such as cystine and lysine. Other processes affect protein nutritional quality to different degrees, inasmuch as they affect amino acid analysis, digestibility and content of biologically active components. When soybean proteins are used to extend animal proteins, supplement other vegetable proteins, or in vegetable protein mixtures, nutritional quality of the combined proteins appears to be affected in the same manner as that of soya proteins alone.