Numerical Analysis of Slag Carry-Over during Molten Steel Draining

Slag carry-over during the draining of molten steel from a teeming ladle is numerically studied here. Two-phase isothermal transient 3D Computational Fluid Dynamics simulations were employed to simulate the draining process. Two nozzle diameters, two nozzle positions and three slag heights were considered. From mass balances, the slag carry-over in terms of mass flow rate was obtained for each of the above variables. Besides, the draining times of the teeming ladle were estimated from theoretical considerations and CDF simulations, and compared.

The Carry-Over of Mycotoxins in Products of Animal Origin with Special Regard to Its Implications for the European Food Safety Legislation

At present, carry-over research in mycotoxins experiences a change in focus. We reviewed the state-of-art knowledge regarding carry-over in aflatoxins, ochratoxin A, Fusarium toxins, patulin, ergot and citrinin. The common cooccurrence of mycotoxins demands for employment of multi-toxin analysis and poses a new challenge in reliable health hazard assessment. Synergies in adverse mycotoxin effects call for a revision of various guidance levels in feed. We found a lack of risk assessment regarding carry-over of rare mycotoxins and metabolites usually considered negligible.

Analysis of Maximum Liquid Carrying Capacity Based on Conventional Tubing Plunger Gas Lift

China’s unconventional gas fields have a large number of low-productivity and low-efficiency wells, many of whichare located in remote and environmentally harsh mountainous areas. To address the long-term stable productionof these gas wells, plunger-lift technology plays an important role. In order to fully understand and accurately graspthe drainage and gas production mechanisms of plunger-lift, a mechanical model of plunger-liquid column uplift inthe plunger-lift process was established, focusing on conventional plunger-lift systems and representative wellboreconfigurations in the Linxing region. The operating casing pressure of the plunger-lift process and the calculationmethod for the maximum daily fluid production rate based on the work regime with the highest fluid recovery ratewere determined. For the first time, the critical flow rate method was proposed as a constraint for the maximumliquid-carrying capacity of the plunger-lift, and liquid-carrying capacity charts for conventional plunger-lift withdifferent casing sizes were developed. The results showed that for 23/8 casing plunger-lift, with a well depth ofshallower than 808 m, the maximum drainage rate was 33 m3/d;for 27/8 casing plunger-lift, with a well depth ofshallower than 742 m, the maximum drainage rate was 50.15 m3/d;for 31/2 casing plunger-lift, with a well depthof shallower than 560 m, the maximum drainage rate was 75.14 m3/d. This research provides a foundation for thescientific selection of plunger-lift technology and serves as a decision-making reference for developing reasonableplunger-lift work regimes.

More stressful event does not always depress subsequent life performance

Climate change has led to a substantial increase in intensity and duration of heat waves worldwide.Predicting the ecological impacts of hot events should incorporate both immediate and potential carry-over effects in different intensities of heat waves. Previous studies suggested that higher heat dose in early life stage of insect generally decreased immediate survival and depressed adult reproduction through carry-over effects, or unchanged adult performance through recovery effects. However, our previous study showed a different pattern, in which longer heat exposures in larval stage did not always decrease but sometimes increase the subsequent adult maturation success in the diamondback moth. We speculated that it might be another important pattern in the carry-over effects vs. heat dose, and conducted experiments using a global pest, Plutella xylostella. Our present results suggested that heat exposures in early life stage reduced the immediate survival and produced general declines with significant zigzag fluctuating patterns in subsequent body size and reproduction as exposure durations increased. The similar patterns were also validated in other insect taxa and other stresses by reanalyzing the experiment data from literatures. The finding highlights the importance for differentiating the biological effects and consequences of changes in heat dose at fine scales;daily exposure hours of a hot day should be considered to predict population dynamic under climate change.

Analysis of Sludge Settling and Rising Behavior in Sewage Treatment Plant in Kuwait

All wastewater treatment plants in Kuwait utilize the activated sludge processes in the removal of organic matter and nutrients from domestic sewage.The efficiency of solid liquid separation in the activated sludge system is determined by the ability of sludge constituents to remain flocculated and to settle fast.In Kuwait’s wastewater treatment plants,solids separation problems may occur in activated sludge system,such as bulking sludge,which affects the quality of the secondary effluent.The main aim of this paper is to study and analyze sludge settling and rising behavior in the activated sludge process of Jahra sewage treatment plant.The results indicated that clarifier effluent has significant suspended solids carry-over,which is eventually removed in the sand filtration process.In addition,test results showed poor settlement of clarifier sludge.The poor sludge settling is related to insufficient oxygen level in the aerators.Suggestions were made to raise oxygen level particularly in the aeration unit.

Development of vibration style ladle slag detection methods and the key technologies

Ladle slag carry-over detection technology (SCDT) is of important practical significance to steel continuous casting production (CCP),which can effectively improve the casting blank quality,increase molten steel yield ratio,and protract the service life of tundish.The current SCDT realization methods and their application circumstance were summarized,and their main problems during the course of factual production were pointed out.The difficult technical points of detection principle,digital signal processing for vibration style SCDT development were described.To aim at the problems of vibration style SCDT,such as low recognition stability and long applied adjustment time,its key technologies including water model experimental platform establishment,two-phase sink vortex entrapment mechanism,forced vibration response of shroud nozzle and steel stream shock vibration signal processing optimization were analyzed deeply,and the corresponding research route and advices were given.

Non-Metallic Inclusions in HSLA Steel-Origin,Detection and Refractory Systems to Improve Cleanness

HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of 【 10 ppm.Macro inclusions of 】 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of 【 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.