Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO_2-MgO-Al_2O_3-Cr_2O_3 system

Synthetic slag samples of the CaO-SiO2-MgO-A1203-Cr203 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction （XRD） and scanning electron microscopy （SEM） equipped with energy-dispersive spectroscopy （EDS）, as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250℃ with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.

Biliary stent combined with iodine-125 seed strand implantation in malignant obstructive jaundice

BACKGROUND Malignant obstructive jaundice is mainly caused by cholangiocarcinoma.Only a few patients are indicated for surgical resection,and the 3-year survival rate is<50%.For patients who are not eligible for surgery,biliary stent placement can relieve biliary obstruction and improve liver function and quality of life.However,restenosis after biliary stents has a poor prognosis and is a clinical challenge.Biliary stent combined with iodine-125(125I)seed implantation can prolong stent patency and improve survival.AIM To evaluate the safety and efficacy of biliary stent combined with 125I seed strand implantation in malignant obstructive jaundice.METHODS We enrolled 67 patients between January 2016 and June 2018 with malignant obstructive jaundice and randomized them into a biliary stent combined with 125I seed strand treatment(combined)group(n=32)and biliary stent(control)group(n=35).All patients underwent enhanced computed tomography and magnetic resonance imaging and were tested for biochemical and cancer markers.Twelve patients underwent pathological examination before surgery.All patients were followed up by telephone or clinical visit.Postoperative liver function improvement,postoperative complications,stent patency time,and survival time were compared between the two groups.Prognostic risk factors were evaluated.RESULTS Technical success was achieved in all patients in both groups.Postoperative liver function improved significantly in all patients(total bilirubin,direct bilirubin,alanine aminotransferase,and aspartate aminotransferase decreased significantly in all patients,the P values were less than 0.05).There was no significant difference in preoperative or postoperative indexes between the two groups for changes in total bilirubin(P=0.147),direct bilirubin(P=0.448),alanine aminotransferase(P=0.120),and aspartate aminotransferase(P=0.387)between the two groups.The median stent patency time of the combined group was 9.0±1.4 mo[95%confidence interval(CI):6.3-11.8 mo],which was significantly longer than the that of the control group(6.0±0.3 mo,95%CI:5.5-6.5 mo,P=0.000).The median survival time of the combined group was 11.0±1.4 mo(95%CI:8.2-13.7 mo),which was significantly longer than that of the control group(7.0±0.3 mo,95%CI:6.4-7.6 mo,P=0.000).Location of obstruction and number of stents were independent risk factors affecting prognosis.CONCLUSION Biliary stent combined with 125I seed strand implantation is safe and effective in malignant obstructive jaundice and improves stent patency time and median survival time.

Endpoint temperature prediction of molten steel in RH using improved case-based reasoning

An improved case-based reasoning （CBR） method was proposed to predict the endpoint temperature of molten steel in Ruhrstahl Heraeus （RH） process. Firstly, production data were analyzed by multiple linear regressions and a pairwise comparison matrix in analytic hierarchy process （AHP） was determined by this linear regression＇s coefficient. The weights of various influencing factors were obtained by AHP. Secondly, the dividable principles of case base including ＂0-1＂ and ＂breakpoint＂ were proposed, and the case base was divided into several homogeneous parts. Finally, the improved CBR was compared with ordinary CBR, which is based on the even weight and the single base. The results show that the improved CBR has a higher hit rate for predicting the endpoint temperature of molten steel in RH.

Hybrid Model of Molten Steel Temperature Prediction Based on Ladle Heat Status and Artificial Neural Network

Aiming at the characteristics of the practical steelmaking process, a hybrid model based on ladle heat sta- tus and artificial neural network has been proposed to predict molten steel temperature. The hybrid model could over- come the difficulty of accurate prediction using a single mathematical model, and solve the problem of lacking the consideration of the influence of ladle heat status on the steel temperature in an intelligent model. By using the hybrid model method, forward and backward prediction models for molten steel temperature in steelmaking process are es- tablished and are used in a steelmaking plant. The forward model, starting from the end-point of BOF, predicts the temperature in argon-blowing station, starting temperature in LF, end temperature in LF and tundish temperature forwards, with the production process evolving. The backward model, starting from the required tundish tempera- ture, calculates target end temperature in LF, target starting temperature in LF, target temperature in argon-blo- wiag station and target BOF end-point temperature backwards. Actual application results show that the models have better prediction accuracy and are satisfying for the process of practical production.

Carbothermic Reduction of Zinc and Iron Oxides in Electric Arc Furnace Dust

The reduction of zinc and iron oxides from electric arc furnace dust （EAFD） by carbon was investigated at temperatures between 800 and 1300℃. The analytic technique employed includes chemical analysis, X-ray fluores- cence spectroscopy （XRF）, X-ray powder diffraction （XRD）, scanning electron microscopy （SEM） equipped with X-ray energy dispersive spectrometry （EDS）, and thermodynamic database FactSage 6.2. It was found that the reduction of zinc and iron oxides depends largely on Boudouad reaction. At 900℃, zinc exists in tested samples as ZnO, which is reduced in the temperature range of 1000--1 100℃. At 1 100℃, 99.11% of the zinc is evaporated. The metallization ratio of Fe is 79.19% at 1300℃, as the content of Fe2＋ is still 9.40%. A higher temperature is thus required for a higher reduction degree of Fe oxides by solid or gaseous carbon.

Case-based reasoning model based on attribute w&ghts optimized by genetic algorithm for predicting end temperature of molten steel in RH

Temperature control is the key of Ruhrstahl-Heraeus (RH) process in steelmaking plant. The accuracy of RH control model greatly affects the molten steel temperature fluctuation. To obtain RH control model with higher accuracy, an improved case-based reasoning (CBR) model based on attribute weights optimized by genetic algorithm (GA) was proposed. The fitness function in GA was determined according to the prediction accuracy of end temperature of molten steel in RH;then, GA is used to optimize all the attribute weights based on known case base. An improved CBR model that contains the optimized attribute weights was applied to predict end temperature of molten steel in RH, and the prediction accuracy wascalculated. Four methods, CBR based on attribute weights optimized by GA (CBR-GA), ordinary CBR, back propagation neural network (BPNN) and multiple linear regression (MLR) method were employed for comparison. The results show that in the error range of [- 3 ℃, 3 ℃],[- 5 ℃, 5 ℃],[- 7 ℃, 7 ℃] and [- 10 ℃, 10 ℃], the prediction accuracy of CBR-GA was improved by 19.99%, 28.19%, 27.11% and 16.3%, respectively, than that of MLR. Compared with BPNN, the prediction accuracy increased by 3.22%, 7.44%, 5.29% and 2.40%, respectively. Compared with ordinary CBR, the accuracy increased by 5.43%, 5.80%, 4.66% and 2.27%, respectively.

Temperature Holding Hood for Hot Charging of Continuous Casting Slab in Tangshan Iron and Steel Company

To improve the charging of high-temperature billets, it is crucial to produce them with zero defects and achieve effective insulation during their hot delivery. A mathematical model was developed based on the heat transfer characteristics of the billet during its hot delivery. The accuracy of the model was established by studying the thermal performance of the cover of the roller conveyer for small billets in Tangshan Iron and Steel Company. The results show that the cover of the roller conveyer of the continuous casting billet can effectively reduce the heat loss during the hot delivery of the billets, and the hot loading temperature was increased by 51.6 °C. The uniformity of the temperature of the casting billet section increased substantially. The temperature difference in the casting billet section was reduced by 120 °C. The heat preservation effects of temperature holding hoods of different materials were compared. It was found that the material of the temperature holding hood has slight effect on the heat preservation.

Improvement in the Hit Ratio of the Yield Strength of HRB400D Reinforced Bar

The hit ratio of the yield strength of HRB400 D reinforced bar(Tangshan Iron and Steel Co.) is low. In this study, the effects of [C], [Mn], [Si], and [V] on the yield strength and mechanism were investigated. The HRB400 D reinforced bar with a specification of 22 spiral was chosen. A narrow composition control was achieved by reducing the lower limit of the Mn content and the amount of the alloying elements; moreover, the hit ratio of the reinforced bar yield strength increased from 65.54% to 96.27%, enhancing product stability. The cost of the steel alloy reduced by 8.86 RMB/ton, improving the market competitiveness of the product.

Carbonation Behavior Assessment of RH Slag Batch after Aqueous Extraction at Environmental Pressure

In order to assess CO2 sequestration amount and carbonation degree for RH slag at surrounding pressure, carbonation process of RH slag batch in lab is investigated, and the parameters of carbonation degree and CO2 sequestration amount are the targets, and the relationship between both and relevant factors, such as CO2 flow, gas bubble size etc. is originally discussed. The carbonation degree increases when temperature increases before 60 oC, then decreases. Particle size has a positive effect on carbonation degree, and carbonation degree for 0.5 L/min is bigger than those for 0.1 L/min and 1.0 L/min. When small gas bubble generator is adopted, carbonation degree and CO2 sequestration amount is improved. The maximum carbonation degree and CO2 sequestration amount is 34% and 178.65 g/kgslag, respectively when 38 μm RH slag batch is carbonated for 90 min at 60 oC under the conditions that CO2 flow is 0.5 L/min and bubble size equals 5 mm. CaCO3 and MgCO3 phases exists through XRD analysis, showing that carbonation process is effective. Carbonation degree model is established assuming carbonation reaction occurs on the active surface of RH slag batch. This model fits very well by comparison between experimental results and model results.