用PLC实现两台水泵的互投

１概述制氧车间循环水系统是６５００ｍ３／ｈ制氧机和１００００ｍ３／ｈ制氧机空分流程的主要配套设备，担负着两套空分设备的冷却和空气预冷的重任。而冷水泵系统是冷却水在整个循环水回路循环的主要动力设备。因此，一旦冷水泵系统发生故障，就不能结合整个空分系统提供冷却水，不仅空气预冷系统的两级空气冷却无法实现扰乱空分工况，而且空分设备也会因运行温度过高而保护跳闸，整个空分装置就会瘫痪，影响氧气的正常生产。循环水系统中原有两套冷水泵系统，但在电气上设有自投的功能，即当工作泵出现故障时，需人工开启备用泵，时间往…     

浅析氮水预冷系统存在问题及处理措施

在10000Nm3/h制氧机氮水预冷系统工作过程中经常出现预冷系统换热效果差、冷冻水泵气蚀、水冷塔液位波动大、冷冻机故障等问题,通过分析预冷系统工作过程,查找故障因素并制定针对措施解决故障问题,提升预冷系统冷却效果及运行稳定性,从而降低机组能耗。     

增设空冷塔液位自动调节系统及阻力报警连锁系统

空冷塔是14000m3/h空分装置的重要组成设备,该设备对空透压缩过的空气进行冷却,使空气温度下降到12℃,冷却后的空气送到分子筛纯化系统除去杂质。空冷塔底部液位是一个十分重要的工艺参数,该液位的恒定是空冷塔长期运行的重要条件。原系统采用一套自动排水阀,一套就地手动排水阀对液位进行调节,一套翻板液位计对液位就地监视、中控室连锁。一旦液位异常,由于手动阀不能及时排水,无法保证液位恢复正常,加上翻板液位计性能差,连锁失控,很可能造成事故的发生,如分子筛带水等。这是生产上所不允许的。针对上述情况,对该系统做了如下改造:将翻板…     

涟钢22000m3／h空分设备自动化控制系统的设计与应用

涟钢22000m3／h空分设备,由杭氧制造。此项目于2005年5月投产,各项运行指标正常。22000m3／h空分设备的自动化控制采用了霍尼韦尔公司的PKS C200系统。自动化设计及控制范围广泛,包括循环水系统、原料空气过滤系统、空压机系统、空气预冷系统、分子筛纯化系统、增压膨胀机系统、精馏塔系统、氧压机系统、氮压机系统、贮槽及加压汽化系统。整个空分设备全部由DCS系统控制,完全实现了中央控制室的集中控制,其工艺流程如图l。     

12000 m3/h空分空气预冷系统改造

空冷塔、水冷塔、冷冻机、喷淋水泵等是大型空分空气预冷系统的重要组成设备,冷却水水质的好坏决定这些设备运行的稳定性、连续性。文章以12 000 m~3/h制氧机为例进行详细分析,并对该机组空气预冷的水系统进行了改造,改造后设备运行稳定,解决了水冷塔及冷冻机结垢的问题,延长了设备运行周期,降低生产成本。     

空分设备预冷系统的设计

介绍了预冷纯化系统的重要性,对一般空分装置的除杂、预冷系统性能的设计加以详尽阐述。空分设备预冷在成套流程中有举足轻重的作用,所以组织设计合理的预冷系统不仅可以满足流程需要,还可以使成套装置的投资与运行费用保持较好的合理性与经济性。     

空冷塔低温结垢原因分析及处理

分析了制氧机空气预冷系统低温结垢的原因,通过在低温水泵入口直接加阻垢缓蚀剂,解决了制氧空冷塔低温结垢的问题。     

预冷调节阀阻力释放策略对空分循环水降本增效的影响

空分装置主要包括循环水冷却器为凝汽器、压缩机级间冷却器和预冷系统。其中,凝汽器和级间冷却器均为管道内带压闭式流动,在满足流动的情况下,对供水压力的绝对数值不敏感;而预冷系统则需循环水与空气定压接触,属于开式换热,当供水压力降低时,调阀开度需增大,调阀的过流能力制约了系统供水压力的优化幅度。晋开二分公司与西安格睿能源动力科技有限公司合作,在研究空分装置运行原理和循环水使用特点的基础上,对空分装置预冷系统常温水和水冷塔补水调阀在不同控制压力下的变化趋势进行测算和评估,制定了预冷调阀阻力释放方案,通过实验释放了调阀阻力,并对水冷塔调阀降压实验中出现的不足进行改进,以期达到降本增效的目的。     

舞钢10000 Nm3/h制氧机组空气预冷系统低温结垢的分析与处理

针对舞钢制氧机组空气预冷系统出现的低温结垢问题,采用合理的水处理药剂及水质稳定技术,避免制氧循环水系统中的空冷塔、水冷塔等预冷系统关键设备发生结垢堵塞现象,实践证明所用水处理药剂及相应水处理技术效果良好,可以保障制氧循环水系统长周期安全稳定运行.     

马钢40000Nm^3／h制氧机组空气流量控制方案的改进

通过对马钢40000Nm^3／h制氧机组主空分系统工况波动原因的分析，改进了空气流量控制方案，使进冷箱空气量保持平稳，基本无波动，促证了整个空分系统工况的正常，从而使40000Nm^3／h制氧机组稳定运行。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.