AOD过程基本的数学模拟

针对AOD(氩氧脱碳)过程提出了一个新的仿真模型,模型考虑了局部的变化,但仍然保证了计算的高效性。一个新的思路就是把AOD转炉作为流股区的活塞流反应器和熔池与表面熔渣的连续搅拌池反应器的组合来模拟。这种方法比之以前的模型有很多优点。首先,它提供了考虑气泡在流股中上升过程局部变化条件的有效方法。因为变量更少,相对于计算流体动力学(CFD)模型,这种构造使其能够非常高效地运算。模型的验证也更容易,因为它具有可被试验确定的特征。将模型与两种不同的试验(高Cr和低Cr钢种)情况进行了对比,结果表明,模型对脱碳和Cr行为的预测很好。利用模型输出结果可以获得主导机制的信息,更为重要的是何种元素主要参与氧的反应。模型给出了不同成分的元素如何在喷嘴附近区域首先发生氧化,之后又在熔渣上浮过程中被部分还原。模型同时包含了对氮行为的模拟,因此可以系统地用于优化脱氮。     

Water modelling study of fluid flow and mixing characteristics in bath during AOD process

Abstract

The fluid flow and mixing characteristics in the bath during the argon–oxygen decarburisation (AOD) process have been investigated on a water model of an 18 t AOD vessel blown through two annular tube type lances of constant cross-sectional area. The geometric similarity ratio between the model and its prototype (including the lances) was 1 : 3. Based on theoretical calculations of the parameters of the gas streams in the lances, the gas blowing rates used for the model were determined fairly precisely. Thus, sufficiently full kinematic similarity between the model and its prototype was ensured. The influence of the gas flowrate and the angle included between the two lances was examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during blowing, and there was no obvious dead zone in the bath, resulting in excellent mixing and a short mixing time. The gas flowrates, particularly that of the main lance, had a key influence on these characteristics. However, the gas jet of the sublance had a physical shielding effect on the gas jet of the main lance, and mixing efficiency could be improved by a suitable increase in the gas blowing rate of the sublance. The angular separation of the two lances also had a marked influence on the flow and mixing in the bath. An excessively large or small separation of the two lances would reduce the stability of blowing and would also be unfavourable to mixing. The optimum range of separation is 60–100° under the conditions of the present work. The relationships between the mixing time and the gas blowing rate, the stirring energy, the modified Froude numbers for the main lance and sublance, the lance arrangement, etc. have been obtained.     

A physical modelling study to determine the influence of slag on the fluid flow in the AOD converter process

A 1:4.6 scale physical model of a production argon oxygen decarburisation (AOD) converter was used to study the influence of top slag on the AOD process. Specifically, the gas penetration depth, fluid flow and slag behaviour under different nozzle diameters, nozzle numbers and gas flow rates were studied. The results show that the relative gas penetration depth generally increases linearly with an increased gas flow rate and a decreased nozzle size. Furthermore, the slag thickness increases linearly with an increased gas flow rate. In addition, the open-eye size was found to increase exponentially with an increased gas flow rate. Overall, three kinds of fluid flow patterns were found in the experiments: (i) a counter-clockwise rotation, (ii) a clockwise rotation and (iii) a double circulation with the plume in the middle of the converter. A counter-clockwise rotation was most common for the current experimental conditions.     

润滑剂添加量对铁基混合粉末工艺性能的影响

本文以硬脂酸锌和石墨作为润滑剂,研究了添加量对铁基混合粉末流动性和松装密度以及压制性能的影响。结果表明,当硬脂酸锌添加量为0.2%~0.6%时可以改善铁基混合粉末的流动性和松装密度,流动性能较原混合粉末提高2.2%~17.4%,松装密度能提高136.6%~149.3%,添加量超过0.6%时效果不明显。添加0.2%~1.0%的硬脂酸锌,粉末压缩性逐渐增加,添加量超过1.0%时,压缩性变差。同时添加硬脂酸锌与石墨时,随着石墨添加量的升高,混合粉末的松装密度和压制性能不断降低。     

Fe/S混合粉体的机械化学反应

采用振动磨样机进行FeS2的机械化学合成,利用X射线衍射和扫描电镜技术研究FeS2的机械化学反应过程。结果表明:整个反应过程没有检测到FeS,反应产物为FeS2;Fe/S体系的机械化学反应有中间相非晶产物FeS2生成,从非晶FeS2到结晶产物FeS2结构的形成并没有随化学转变的结束而完成,而是发生了一定的滞后;Fe/S体系的机械化学反应属于非平衡机制;提高研磨转速,只能缩短机械化学反应的发生时间,而不会改变整个机械化学反应趋势。     

氮气保护下铝基烧结含油轴承烧结工艺优化研究

通过粉末冶金技术制备质量分数为7.5%的含铜铝基烧结含油轴承试样,研究了在氮气保护下不同烧结温度以及烧结时间对试样的微观结构和综合性能的影响,优化得到最佳烧结工艺。研究结果表明,当烧结温度超过537℃时,烧结试样发生局部熔化,液相开始生成;随着烧结温度升高和烧结时间的延长,烧结试样的尺寸收缩率以及压溃强度不断提高而含油率不断减小。当烧结温度为560℃、烧结时间为120 min时,烧结试样拥有良好的综合性能,压溃强度和含油率分别为151.3 MPa和16.7%,呈最佳烧结状态。     

Mathematical modelling of decarburisation and degassing during vacuum circulation refining process of molten steel: mathematical model of the process

Based on the mass and momentum balances in the system, a new mathematical model for decarburisation and degassing in the vacuum circulation refining process of molten steel has been proposed and developed. The refining roles of the three reaction sites, i.e. the upsnorkel zone, the droplet group and steel bath in the vacuum vessel, have been considered in the model. It was assumed that the mass transfer of reactive components in the molten steel is the rate control step of the refining reactions. And the friction losses and drags of flows in the snorkels and vacuum vessel were all counted. For the refining process of molten steel in a 90 t multifunction RH degasser, the parameters of the model have been discussed and more reasonably determined.     

Effect of snorkel shape on the fluid flow during RH degassing process: mathematical modelling

A mathematical model was developed to investigate the effect of snorkel shape on the recirculation rate and the erosion of the lining refractory during RH degassing process. A particle image velocimetry technique was used to measure the velocity distribution in a water modelling experiment. The calculated results were well validated with the measured ones. In the mathematical model, the interfaces between the molten steel and the gas phase, and the motion of argon bubbles were simulated and tracked using VOF?+?DPM model by which the argon bubbles were treated as the discrete phase in the molten steel and the top gas phase, and the top gas phase was treated as a second continuous phase. It was found that the recirculation rate of the molten steel with oval snorkels was significantly larger than that with round snorkels. For round snorkels, the optimum gas flow rate was 1800?L?min^?1 and it was 2800?L?min^?1 for oval snorkels. Furthermore, the volume distribution of the argon in the radial direction of the up-snorkel with oval snorkels was much more homogeneous than that with round snorkels. Meanwhile, the predicted maximum wall shear stress showed that the bottom and the sidewall of the ladle with round snorkels were more seriously eroded than that with oval snorkels. Therefore, the oval snorkel was beneficial to improve the service life of the RH degasser.     

Group productivity and process: Pure and mixed reward structures and task interdependence.

Conducted 2 experiments in which triads participated in multitrial block-stacking tasks that allowed for objective measures of productivity and process. In Exp I with 210 undergraduates, the task was executed either interdependently in the form of a single tower or individualistically in the construction of 3 separate towers. Reward points were distributed equally (cooperative), in relation to contribution (independent), or only to the most productive group member (competitive). Results indicate that cooperative and independent systems were associated with greater productivity than competitive systems only under conditions of high task interdependence, and that there was no relation between reward system and productivity for the individualistic task. In Exp II with 154 undergraduates, independent and competitive allocations were each combined in varied proportions with cooperative allocation to examine the effects of mixed reward systems on productivity and process. Results show that even a modicum of competitive reward led to lowered efficiency and productivity. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Iron ore reduction/cementation: experimental results and kinetic modelling

Abstract

Iron ore reduction and iron cementation by H₂-CH₄-Ar gas mixtures were investigated in a laboratory isothermal fixed bed reactor in the temperature range 600-925°C. Iron ore was first reduced to metallic iron by hydrogen, then metallic iron was carburised to cementite by methane. Increasing temperature and hydrogen content accelerated the reduction process. However, for >55 vol.-%, the effect of H₂ content was not significant. Methane had almost no effect on the reduction process. Increasing temperature increased the rate of iron cementation and also the rate of free carbon deposition. Optimum conditions for cementite formation were: temperature 750°C and reducing/carburising gas contents of 40-55 vol.-%H₂ and 35 vol.-%CH₄. Under these conditions, reduction of iron ore to cementite was completed in ~15 min. A two interface grain model and a volume reaction model were used to simulate the process of iron ore reduction and iron cementation. The simulated results for both reduction and cementation were consistent with the experimental data.     

Mathematical modelling of decarburisation and degassing during vacuum circulation refining process of molten steel: application of the model and results

The mathematical model for decarburisation and degassing in the vacuum circulation refining process of molten steel, proposed and presented earlier, has been applied to the refining process of molten steel in a multifunction RH degasser of 90 t capacity. The decarburisation and degassing processes in the degasser under the RH and RH‐KTB operating conditions have been modelled and analysed using this model. It was demonstrated that for the RH and RH‐KTB refining processes, the results predicted by the model are in good agreement with some plant data. The mean contributions of the three refining sites in six circulation cycles to decarburisation are 10.5 – 11.6, 37.4 – 38.0 and 50.5 – 52.1 % of the overall amount of decarburisation, respectively. The KTB operation can markedly accelerate the decarburisation of molten steel. Using the top blowing oxygen of 6 min with the flow rate of (600 ‐ 1000) m³(STP)/h, the initial carbon mass content of the liquid steel for the RH refining process may be increased to (550 ‐ 700) · 10‐⁴ from 400 · 10‐⁴ %. And the treatment time needed for reducing the carbon mass content in the steel to a level of ≤ 20 · 10‐⁴ % may be shortened over 3 ‐ 4 min. The effectiveness of decarburisation and degassing cannot be obviously improved by increasing the lifting argon blow rate to 900 from 600 I(STP)/min under the operating modes examined in the present work.     

Review of Therapeutic experiencing: The process of change.

Reviews the book, Therapeutic experiencing: The process of change by Alvin R. Mahrer (1986). This book is designed as a how-to book for experiential psychotherapy. It is an attempt to synthesize the various theories of the experiential therapies into one coherent theory which is different from other schools of therapy. The book is organized into eight sections and an introduction. This book is a well-organized presentation of a therapeutic modality. It should prove useful to therapists who work in this modality, as well as to students wishing to understand this modality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Therapeutic experiencing: The process of change.

Reviews the book, Therapeutic experiencing: The process of change by Alvin R. Mahrer (1986). This is the third in a series of books on Mahrer's approach to experiential therapy. In this volume Mahrer describes the four major change processes that occur in his form of experiential therapy. The book is organized around these four processes with a chapter explaining the theoretical principles and rationale for each process followed by a chapter introducing methods for implementing the process. This is a challenging book for any who practice some form of experiential therapy and for those interested in humanistic/existential approaches. More research on the principles of this approach will be needed to convince many of the utility of the proposed change processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Therapeutic experiencing: The process of change.

Reviews the book, Therapeutic experiencing: The process of change by Alvin R. Mahrer (1986). In one sense, Mahrer makes the reviewer's task easy by summarizing in his introduction such key points as the purpose of his book, its scope, and its intended readership. Mahrer has two stated purposes: one is "to show how to do experiential therapy" and the other is "to build upon the various members of the experiential family and to propose a single theory of experiential psychotherapy complete with its own methods of bringing about therapeutic change." There are three conditions, however, which must be met in order to enable the reader to do experiential therapy. The first is that the reader is familiar with and sympathetic to existential-humanistic thinking. It is to all such therapists, as well as to their patients, that this book is addressed. The other two conditions that must be fulfilled in order to undertake experiential therapy are that the reader understands how to start each experiential therapy session and knows how to listen experientially. These latter two conditions are the subject of an earlier book by Mahrer, Experiential Psychotherapy: Basic Practices, which is thus basic reading for anyone intending to apply the method described in the current volume, as these two conditions together comprise the essential first of five steps that constitute each experiential psychotherapy session. The current volume picks up the method only at step two, "carrying forward of potentials for experiencing," and covers the remaining steps as well: "experiencing the relationship with deeper potentials, experiential being of the deeper potentials, and being/ behavioral change." In Therapeutic Experiencing , Mahrer stipulates that the patient should have a minimum of three hundred sessions, distributed over a 3-year period, and return for therapeutic work every two years or so for about 10 to 15 sessions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Alcoholism treatment: Context, process, and outcome.

Reviews the book, Alcoholism treatment: Context, process, and outcome by Rudolf H. Moos, John W. Finney, and Ruth C. Cronkite (see record 1990-98391-000). The research of Moos, Finney, Cronkite, and colleagues, which is summarized in the present volume, has been pivotal in drawing attention to the role of extratreatment factors in the alcohol recovery process. Their work demonstrates the limited influence of patient- and treatment-specific characteristics in predicting long-term outcomes and shows that extratreatment, contextual factors such as life events, family and social resources, and coping responses, add significantly to the prediction of outcomes as long as 10 years after treatment. These findings raise important questions about the utility of treatment outcome studies that focus exclusively on treatment-produced behavior change and that ignore the broader life context in which treatment is administered. The book details the empirical bases of these conclusions and summarizes the authors' 10-year outcome evaluation of five inpatient and residential alcohol treatment programs. Although the work of Moos and colleagues has been instrumental in directing attention toward contextual variables, their measurement and data-analytic practices are probably inadequate to explicate thoroughly how life contexts influence the drinking patterns of individual problem drinkers over time, which are the kinds of data that will best inform the development of interventions to enhance natural contingencies that promote abstinence. Without exception, their follow-up measures were discontinuous and yielded only summary indices of subjects' drinking behavior and functional status on the life context variables. This and other limitations regarding measurement and conceptualization notwithstanding, the Moos et al study stands as a landmark investigation revealing the critical influence of life context factors on the lengthy process of recovery from alcoholism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Learning process in psychoanalytic supervision: Complexities and challenges.

Reviews the book, Learning process in psychoanalytic supervision: Complexities and challenges by Paul A. DeWald (see record 1987-97784-000). This book is a wonderful contribution to the field of supervision. It is the only book available that presents the actual supervision sessions of one ongoing supervisee with one long-term psychoanalytic patient as they were transcribed. DeWald also offers a review of the supervisory literature, his view of the supervisory process, his supervisory reports, and a chapter from the supervisee discussing her experience. The book is refreshing in that the supervisor does not present himself as perfect, and he does acknowledge mistakes he made in the comments after each set of process notes. There are some criticisms of the book to be made. First, the reviewer was not able to determine the frequency of the patient's sessions or the supervisory sessions. Second, the author's framework is classically Freudian. While this is not a problem, it is important that the reader be aware of the point of view. Third, the author seems ambivalent about the role of the patient's ethnicity and culture in her neurotic stance. These comments aside, Learning process in psychoanalytic supervision is an excellent book, and certainly one any supervisor would want to read. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central neurocytoma: one associated with a fourth ventricular PNET/medulloblastoma and the second mixed with adipose tissue

We report two cases of central neurocytoma; one located in the right lateral ventricle and associated with a distinctly separate primitive neuroectodermal tumor (PNET)/medulloblastoma of the fourth ventricle, and the other admixed with fat cells and arising from the left lateral and third ventricles with extension into the corpus callosum. We discuss that concurrent occurrences of PNET and adipose tissue are not fortuitous events, but an evidence that neurocytomas and PNETs originate in the residual germinal pool from common progenitor cell rests recapitulating features of developing neurons and with a potential for mesenchymal differentiation.