KDN-1500/120Y型制氮设备冻塔原因分析及处理

KDN-1500/120Y型制氮设备停车检修后重新开车时,没有对分子筛进行加温再生而使用了工作时间较长且停运达48小时的分子筛吸附器,使水分进入空分塔造成冻塔故障。介绍故障发生的经过、现象和应对措施。     

粗氩冷凝器堵塞故障的处理

因为进分子筛吸附器的空气温度偏高,分子筛吸附器出口空气中二氧化碳含量超标,二氧化碳在粗氩冷凝器换热通道内积聚,造成粗氩冷凝器堵塞,制氩系统停运。介绍粗氩冷凝器堵塞时的参数变化情况和采取的加温措施。     

制氧工问题浅解(十七)

1．问:在使用周期不变的条件下,为什么启动阶段使用的一只分子筛吸附器要比正常运转时使用的一只加热速度快?答:分子筛吸附器(或干燥器)在再生加热时的速度快慢与吸附剂的吸水量多少、加温气体的干燥度、加温气体的气量大小等因素有关。其中吸附剂的吸水量多少,与使用时间、高压空气的温度和压力有关。使用时间越长,高压空气的温度越高和压力越低时都会使吸附器中的吸水量增加,因此,加温的时间就需延长。     

国外分子筛制氩情况介绍

本文介绍了国外分子筛制氩的几种流程、吸附器的设计、分子筛的再生和吸附气体的解吸,最后比较了国内分子筛制氩的差距。图7,表1,参考文献5。     

XKAr-3型制氩装置试车操作体会

本文介绍了XKAr－3型制氩装置两次试车操作的情况:试车前150米3/时制氧机的改进、粗氩塔和吸附器的启动与操作,以及分子筛吸附器的使用。     

制氧工问题浅解

1．问:改用分子筛吸附器净化空气应注意哪些问题?答:实践证明,将原用碱洗塔—干燥器清除二氧化碳、水份的净化方法改为用5A分子筛净化空气的方法是完全可行的。在改用分子筛吸附器时,对以下几个问题应引起注意:     

XKAr-3型制氩装置试车操作体会

介绍XKAr-3型制氩装置一次试车成功的情况。改进了主塔(增加塔板,改小筛孔),检修了空压机和膨胀机,高温活化了分子筛。侧重介绍了粗氩塔和分子筛吸附器的启动与操作,并对各种工况进行了较全面的分析。最后提及了分析取样、密封垫片、阀门开度等问题。     

氩吸附器使用中的一次事故处理

配150m~3/h制氧机分子筛制氩装置,因氩吸附器外简超压,使外筒膨胀,中、内筒压瘪,液空泄漏,无法生产。分析是中筒液空经小孔渗到外筒,加温时外筒抽空阀未订开,汽化超压所致。后自己加工组装了一组没有外筒的氩吸附器,运转证明是可行的。表1。     

“青氧”采用分子筛制氩新工艺

青岛氧气厂学习兄弟单位先进经验,采用分子筛制氩新工艺,于1977年5月1日生产出合格的纯氩。吸附器直径250毫米,有效高度4006毫米,其中5A 层离1503毫米,容积60立升,装φ2~3毫米全胶型5A分子筛43公斤。4 A层高2503毫米,容积98立升,装φ2~3毫米全胶型4 A分子筛85公斤。吸附器平均流速0．71厘米/     

分子筛吸附器均压阀控制程序改进

空分设备在运行过程中,分子筛吸附器均压过程易造成精馏系统压力波动,尤其是带制氩系统运行的空分设备,精馏系统工况波动较大,制氩系统工况也很难稳定。具体分析了分子筛吸附器均压过程引起精馏系统压力波动的原因,通过改进分子筛吸附器均压阀控制程序,减小了系统压力和气量的波动幅度,实现空分设备稳定运行。     

分子筛吸附器进水故障的分析与处理

介绍因空冷塔结垢水被带入 6 0 0 0m3 /h空分设备分子筛吸附器的故障现象、原因分析及处理措施 ;简述了防止此类故障发生的措施。     

分子筛纯化系统故障的不停机处理

介绍了近10年来不停机处理两套30000m3/h空分设备分子筛纯化系统故障的经验,具体分析了分子筛泄漏、切换阀不动作或动作不动位及吸附器运行程序混乱的处理方法。     

主塔及氩塔产品纯度下降的故障分析

在分子筛吸附器切换过程中进塔空气量和压力的变化 ,破坏了分馏塔工况 ,从而引起氩塔工况的破坏 ,说明恒流、恒压对全精馏无氢制氩空分装置的重要性     

仪表气漏入工艺管道导致空分装置停车

介绍了主换热器换热不良、主冷液面维持不住 ,空分装置被迫停车的故障现象及原因 ;通过分析 ,仪表气自保系统发生故障 ,使含有大量二氧化碳的仪表气串入分子筛吸附器后的工艺空气中 ,是导致主换热器换热不良的原因 ;并提出了几点操作上的教训     

分子筛吸附器的自动切换控制系统

本文描述了分子筛吸附器自动切换控制系统用DCS控制的组态思路和方法 ,例举了该程序在实际中的应用。     

Distortion of ion structures by field asymmetric waveform ion mobility spectrometry

Field asymmetric waveform ion mobility spectrometry (FAIMS) is emerging as a major analytical tool, especially in conjunction with mass spectrometry (MS), conventional ion mobility spectrometry (IMS), or both. In particular, FAIMS is used to separate protein or peptide conformers prior to characterization by IMS, MS/MS, or H/D exchange. High electric fields in FAIMS induce ion heating, previously estimated at <10 degrees C on average and believed too weak to affect ion geometries. Here we use a FAIMS/IMS/MS system to compare the IMS spectra for ESI-generated ubiquitin ions that have and have not passed FAIMS and find that some unfolding occurs for most charge states. These data and their comparison with the reported protein unfolding in a Paul trap imply that at least some structural transitions observed in FAIMS, or previously in an ion trap, are not spontaneous. The observed unfolding is similar to that produced by heating of approximately 50 degrees C above room temperature, consistent with the calculated heating of ions at FAIMS waveform peaks. Hence, the ion isomerization in FAIMS likely proceeds in steps during the "hot" periods, especially right after entering the device. The process distorts ion geometries and causes ion losses by a "self-cleaning" mechanism and thus should be suppressed as much as possible. We propose achieving that via cooling FAIMS by the amount of ion heating; in most cases, cooling by approximately 75 degrees C should suffice.     

Thermal stability of polyethylene terephthalate (PET): oligomer distribution and formation of volatiles

Two ovenable PET (polyethylene terephthalate) samples were investigated under severe heating conditions and oligomers and volatile substances were analysed as potential migrants into foods. The samples were tested for migration into water, 3% acetic acid and 15% ethanol solution for 1 hour at 95°C. Overall migration and the specific migration of terephthalic acid, ethylene glycol and diethylene glycol were all very low. The plastics were heated at 150°C, 260°C and 270°C, for 5 minutes 30 minutes and 60 minutes. Oligomer analysis by LC/MS (liquid chromatography‐MS) showed that the concentration of the second series alicyclic oligomers increased up to 15‐fold on heating whereas the major oligomer fraction, the cyclic trimer, tetramer, pentamer and hexamer showed only minor concentration changes with heating. Volatiles evolved by the samples were trapped on a Tenax trap and identified by GC/MS (gas chromatography‐MS). They were few in number and low in concentration and none merited migration tests. It is concluded that even when tested up to melting point, PET plastics of this type have good temperature stability and are well suited for high‐temperature food contact applications. Copyright © 1999 John Wiley & Sons, Ltd.     

Ion exchangers and adsorbents — Versatile aids for the materials processing industry

Ion exchangers and adsorbers are available nowadays in such a wide range of universally applicable or specialist products that they are used extensively in chemical industry. New applications are discovered each year. Hence their originally predominant use in water treatment has meanwhile been extended and diversified by numerous further applications.     

Thermal swing adsorption refrigeration (heat pump)

A review of the possibilities of thermal swing adsorption processes for refrigeration and heat pumping is presented. Adsorbent-adsorbate pairs suited for such development are examined, and processes using adsorbers with or without temperature gradients are discussed. It is shown that these adsorptionbased devices have significant potentials provided the heat and mass transfer rates of the adsorption/ desorption steps can be enhanced. Possible ways of enhancing adsorber performances are explored.     

High temperature resistance of a very high volume fly ash cement paste

The physical and chemical changes taking place in a very high volume fly ash cement paste (FAN-4) following exposure to temperatures up to 1000 °C are presented. Tests were repeated with commercially available CEM II/A-M Portland composite-cement (MS). FAN-4 pastes showed impressive residual strengths after heat exposure which increased dramatically when heated previously at 800 or 1000 °C. This was in stark contrast to the MS paste, which showed a continual decrease in residual strength following heating and subsequent cooling. The increase in residual strength with FAN-4 paste coincided with a major shrinkage event, which was associated with sintering and the formation of the new mineral phases anorthite, gehlenite, wollastonite, diopside and albite. The MS cement formed generally non-hydraulic calcium silicate phases upon heating at ⩾800 °C. The differences in phase formation were linked to different starting elemental compositions. The FAN-4 paste was considerably richer in Si, Al, Fe and alkalis but poorer in Ca. The elemental composition of the binder phase will be an important factor to take into account when determining the high-temperature performance of future cements and concretes, which are likely to contain significantly higher contents of supplementary cementitious materials than is presently the case.