Temperature Lag Research Articles

Effect of high temperature tempering on the phase composition and structure of steelmaking slag

Abstract Blast furnace slag and steelmaking slag, as the main accessory products of iron and steel smelting, are piled up in large quantities due to their huge output, high treatment difficulty and low comprehensive utilization rate, which has a serious impact on the land and environment. In order to improve the comprehensive utilization of steelmaking slag, low basicity blast furnace slag was added to the existing steel slag for quenching and tempering. The influence of basicity on the chemical composition and phase precipitation of mixed slag was analyzed. In the research process, the phase composition and morphology of blast furnace slag and steel slag of Baotou Steel were analyzed using FactSage7.1 thermodynamic calculation software, ZEISS high-resolution scanning electron microscope (SEM), modern fast high-resolution Bruker energy dispersive spectrometer and AMICS-Mining automatic mineral analysis software. The results show that the mineral phase composition of blast furnace slag is mainly calcium aluminum yellow feldspar and that of steelmaking slag is mainly dicalcium silicate(C2S), magnesium-iron phase solid solution, rose pyroxene and calcium iron aluminate. When the basicity of the mixed slag is 2.0, it can effectively inhibit the formation of non-cementitious mineral anorthite and promote the formation of better cementitious mineral C2S. At the same time, it is found that the melting temperature of mixed slag decreases with the increase in Al2O3 content.

Environmental Drivers of Amphibian Breeding Phenology across Multiple Sites

A mechanistic understanding of phenology, the seasonal timing of life history events, is important for understanding species’ interactions and the potential responses of ecological communities to a rapidly changing climate. We present analysis of a seven-year dataset on the breeding phenology of wood frogs (Rana sylvatica), tiger salamanders (Ambystoma tigrinum), blue-spotted salamanders (Ambystoma laterale), and associated unisexual Ambystoma salamanders from six wetlands in Southeast Michigan, USA. We assess whether the ordinal date of breeding migrations varies among species, sexes, and individual wetlands, and we describe the specific environmental conditions associated with breeding migrations for each species/sex. Breeding date was significantly affected by species/sex identity, year, wetland, and the interactions between species/sex and year as well as wetland and year. There was a great deal of variation among years, with breeding occurring nearly synchronously among groups in some years but widely spaced between groups in other years. Specific environmental triggers for movement varied for each species and sex and changed as the breeding season progressed. In general, salamanders responded to longer temperature lags (more warmer days in a row) than wood frogs, whereas wood frogs required longer precipitation lags (more rainy days in a row) than salamanders. Wood frogs were more likely to migrate around the time of a new moon, whereas in contrast, Ambystoma salamander migration was not associated with a moon phase. Ordinal day was an important factor in all models, suggesting that these amphibians require a latency period or similar mechanism to avoid breeding too early in the year, even when weather conditions appear favorable. Male wood frogs migrated earlier than female wood frogs, and male blue-spotted salamanders migrated earlier than female A. laterale and associated unisexual females. Larger unisexual salamanders migrated earlier than smaller individuals. Differences in species’ responses to environmental cues led to wood frogs and A. laterale breeding later than tiger salamanders in colder years but not in warmer years. This suggests that, as the climate warms, wood frog and A. laterale larvae may experience less predation from tiger salamander larvae due to reduced size differences when they breed simultaneously. Our study is one of few to describe the proximate drivers of amphibian breeding migrations across multiple species, wetlands, and years, and it can inform models predicting how climate change may shift ecological interactions among pond-breeding amphibian species.

The critical condition and kinetics of interaction between residual char and slag in the coal slagging gasifier

Due to low gasification reactivity of carbon feedstock and improper discharge operation, residual char is often found in bath of moving bed slagging gasifier, which affects the carbon conversion and slag discharge significantly. Moreover, the critical condition of interaction between char and slag determines whether char can be wrapped and consumed by slag in bath, while kinetics of interaction affects consumption rate of residual char wrapped by slag. In this work, the critical condition and kinetics of interaction between residual char and slag were investigated in terms of wetting behavior and carbothermal reaction. Results show that the increase of temperature not only lowers the contact angle between the slag and char, but also be beneficial to carbothermal reaction, thus, high temperature can improve wetting behavior at the slag/char interface. According to different factors that affect wettability during heating, the curve of contact angle between char and ash can be divided into three stages. Besides, it was found that the coal char with low graphitization degree is easy to be wrapped by ash with high SiO2/Al2O3 ratio, and quantitative relation between wrapped temperature and property of slag and char was established to predict critical condition of interaction. In addition, a limit of carbothermal reaction in thermodynamics was observed, and non-isothermal kinetic equations of carbothermal reaction were established, which can provide guidance for slag discharge operation of moving-bed slagging gasifier.

Thermodynamic analysis of vanadium distribution behavior in blast furnaces and basic oxygen furnaces

Abstract Production data from a vanadium (V)-containing titaniferous magnetite (VTM) smelting blast furnace (BF) ironmaking plant and a V-recovering basic oxygen furnace (BOF) shop were collected over a period of 1 year. The corresponding thermodynamics was analyzed in terms of V reduction in the BF operation and V oxidation in the BOF operation. The thermodynamic calculations were performed using the software Multi-Phase Equilibrium (MPE), in which generalized central atom model was introduced into the description of molten slag and applied for the slag database. The effects of operating conditions on V distribution ratios between slag and hot metal/semi-steel were analyzed and compared with the plant data. The simulated results could reproduce the variation of V distribution ratios with slag temperature and composition and provide the guidance for operators to control V distribution behavior for the better process operation.

On the thermo-vibrational response of multi-layer viscoelastic skin tissue to laser irradiation

This paper investigates temperature and vibration responses of human multi-layer skin tissue to laser irradiation. Due to the viscoelastic property of skin, a standard linear solid model known as the Zener model with two relaxation times with dual phase-lag heat conduction model has been used to describe the temperature and displacement in a one-dimensional form. The obtained differential equations have been discretized in the weak form to balance thermal and vibrational energies. The extracted time-dependent ordinary differential equations have been solved numerically by integration over time. The investigations are based on the effect of four relaxation times of temperature, heat, strain, and stress with laser effect in the form of a single step or repeated pulses on the behavior of the skin. By examining their results, the effect of phase lags has also been discussed, showing that the heat phase lag has a complex impact on thermal response and depends on the type of laser radiation. The phase lag of temperature reduces the temperature change rate, and the strain phase lag spreads the displacement at later times, gives inertia to the system, and dampens the system's vibration.

Plant–atmosphere heat exchange during wind machine operation for frost protection

To mitigate spring frost damage, fruit farmers use wind machines to mix warm overlying air down to the vegetation. Up to this point, studies on wind machine efficiency have focused on air temperatures. The temperature of different plant organs during operation remains unknown, while critical for the actual degree of frost damage. With Distributed Temperature Sensing we measured vertical in-canopy air temperature profiles in a pear orchard in the Netherlands and thermistors were installed to determine the plant tissue temperatures. We found that to optimize wind machine operation, it is important to consider two effects of a wind machine: (1) mixing of stratified air above and into the canopy layer and (2) erosion of the leaf boundary layer to facilitate plant–air heat exchange. We show how foliage reduces plume penetration to the ground with distance to the wind machine. Due to this blocking at least 15 rotations (∼ 75 min) are needed for optimal mixing. Leaf temperatures lag behind air temperatures, due to strong radiative cooling. We found that over the rotation cycle of a wind machine the temperature difference between leaf and air is variable as convective warming repeatedly dominates over radiative cooling. This is different for flowers and shoots due to different heat capacities. Thin flower petals store little heat and are almost in direct equilibrium with air temperature changes. Shoots, with their higher heat capacity and lower surface/volume ratio, store more heat during the day that is slowly released at night. This discrepancy between plant and air temperature should be considered for frost damage prediction.

Effect of CeO2 Content on Melting Performance and Microstructure of CaO-Al2O3-SiO2-MgO Refining Slag

CeO2 can be applied to refining slag to minimize the size of inclusions, speed up the deoxidization process, and adsorb Al2O3 inclusions. The impact through which CeO2 content affects slag’s melting efficiency is still uncertain. The thermal analyzer was used to measure the thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) curves of the slag melting process. According to the study results, with the increase in CeO2 content, the melting temperature of slag decreased first and then increased. The slag’s melting point fell from 1364 °C to 1324 °C and then rose to 1503 °C. XRD and SEM were used to analyze the CaO-Al2O3-SiO2-MgO-CeO2 slag’s microstructure. The mineral-phase structure of CeO2-containing refining slag was primarily composed of Ca2SiO4 and 3CaO·Al2O3, MgO, SiO2, CaO·Al2O3, and Ca8Ce6Al6O26. The proportion of 3CaO·Al2O3, CaO·Al2O3, and Ca2SiO4 decreased as the rare-earth-oxide content increased, while the proportion of Ca8Ce6Al6O26 increased. FactSage was used to estimate the equilibrium-phase compositions of slags with various compositions, and a model for predicting melting points was carried out by a linear regression model. Results were obtained through the analysis of equilibrium-phase composition and crystal structure transformation. The main reasons for the melting point decrease were the change of degree of polymerization and the decrease in contents and complete melting temperature of high-melting-point Ca3Al2O6 and Ca2SiO4 compounds. The latter increase in melting point was due to the number of Ca8Ce6Al6O26 compounds and precipitation temperature increases and the complexity of the structural-network increases.

Oxidation Enhancement of Gaseous Elemental Mercury Using Waste Steel Slag under Various Experimental Conditions

In this study, the oxidation characteristics of elemental mercury were assessed based on the input gas environment, temperature, and particle size distribution of the steel slag. Experiments were performed at room temperature, 100 °C and 200 °C, under air and simulated gas environments. The oxidation reaction of elemental mercury was conducted using steel slag samples of 1 mm, 2.36 mm, and 4.75 mm at various conditions. From the basic characteristic analysis of the steel slag, it was found that the steel slag exhibits a similar composition to that of fly ash, and it can be utilized as an oxidizing agent. Results show that regardless of the temperature and the particle size distribution of steel slag, the oxidation reaction of elemental mercury rarely occurred in the air environment. However, in the case of the HCl gas environment, it was observed that the smaller the steel slag particle size, the stronger the oxidation reaction. It is believed that the oxidation efficiency of the steel slag increased as the contact area between the gas and particles increased. The oxidation reactivity was nearly two times higher in the temperature range of 100 °C to 200 °C than it was at room temperature. It is advised that further research be undertaken in order to determine the precise temperature range at which the oxidation reaction occurs.

Control of Copper Content in Flash Smelting Slag and the Recovery of Valuable Metals from Slag—A Thermodynamic Consideration

To determine slag properties and the factors influencing these properties for optimization of operating conditions in the copper flash smelting process, the composition and microstructures of the quenched smelting and converting slags have been analyzed. Thermodynamic software FactSage 8.2 has been used to investigate the effects of matte grade, SO2 partial pressure, and the Fe/SiO2 ratio on the liquidus temperature and the copper content of the smelting slag. The possibility to recover valuable metals from the smelting and converting slags through pyrometallurgical reduction by carbon is also discussed. It was found that the flash smelting slag temperature is usually higher than its liquidus temperature and the copper (1.2% Cu) is mainly present in the slag as dissolved copper. In the copper flash smelting process, the copper content in the slag can be decreased by decreasing the Fe/SiO2 ratio and temperature. In pyrometallurgical slag reduction, most Cu, Mo, and Ni can be recovered as an alloy. The conditions of recovery such as the ratio of smelting slag to converting slag, temperature, and reduction extent have been discussed.

Influence of Fly Ash on the Fluidity of Blast Furnace Slag for the Preparation of Slag Wool

Using fly ash as the modifier, blast furnace slag was modified to prepare slag wool, fulfilling the goal of using one type of waste to make use of another type of waste, and it is of great significance for the comprehensive utilization of industrial bulk solid wastes and resource recycling. In the process of forming fiber from blast furnace slag, fluidity is the key factor affecting the smooth formation of fiber from slag. To explore the changes in the fluidity of modified blast furnace slag, the temperature-dependent viscosity of modified blast furnace slag with different amounts of fly ash added was measured, and the effects of fly ash addition on the viscosity, fluidity, and activation energy of particle migration, and slag structure of modified blast furnace slag were investigated. The results indicated that with the increase in the amount of fly ash added, in the high-temperature region (>1324 °C), the viscosity of modified blast furnace slag increases gradually, the fluidity decreases gradually (i.e., the fluidity becomes worse), and the suitable fiber-forming temperature range gradually widens. When the fly ash addition increases from 5% to 25%, the trend of the activation energy of slag particle migration is as follows: increase, decrease, increase significantly, decrease. When the addition of fly ash is less than 20%, the SiO2 content and slag temperature jointly affect the breakage and reorganization of oxygen bridge bonding in the silicon-oxygen tetrahedron in the slag structure. When the addition of fly ash increases to 25%, the slag temperature dominates the breakage of oxygen bridge bonding in the silicon-oxygen tetrahedron in the slag structure. When using fly ash as the modifier to prepare slag wool, from the perspective of slag fluidity and process operability, the optimum addition amount of fly ash is 15%.

The melting performance blast furnace slags with high alumina content

With a view to understanding the performance of the blast furnace slag with high Al2O3 content, the effects of w(MgO)/w(Al2O3), w(CaO)/w(SiO2), and w(Al2O3) on the melting performance (melting characteristic temperature and melting heat) of the blast furnace slag with high Al2O3 content were investigated by the differential scanning calorimeter (DSC) method. Experimental results indicate that melting end temperature (Tend) for almost all the slags has no obvious change with the increase of w(MgO)/w(Al2O3), w(CaO)/w(SiO2) and w(Al2O3) of the slag will raise Tend of the slag. When (w(MgO)/w(Al2O3), R, and w(Al2O3) are high, the melting onset temperature (Tonset) of the slag increases with the increase of any variables. When w(CaO)/w(SiO2) is low, Tonset of the slag decreases with the increase of w(Al2O3). w(MgO)/w(Al2O3), w(CaO)/w(SiO2), and w(Al2O3) within the scope of this study and all these factors lead to the increase of the slag melting heat.

Development of waste heat recovery technology from steel slag

The temperature of molten steel slag produced by the steelmaking process is 1500°c~1700°c, and the total amount of energy contained is considerable. Therefore, the efficient recovery and utilization of sensible heat of steel slag has always been the focus of attention of the metallurgical field all over the world. However, at present, the average recovery rate of waste heat resources per ton of steel in China's iron and steel industry is less than 26%, while the sensible heat recovery rate of various molten slag (including steel slag) is only 1.6%. There are huge room and a broad market for improvement.

Understanding the relationship between weather variables and intake in beef steers.

The relationship between weather variables and dry matter intake (DMI) in beef steers was examined using daily intake data from 790 beef steers collected through a computer-controlled feeding system in nonsummer months. Daily data were condensed into weekly averages (N = 13,895 steer-weeks). The variables considered to predict DMI (2.50 to 23.60 kg/d) were body weight (197 to 796 kg), dietary net energy for maintenance (NEm; 0.79 to 2.97 Mcal/kg), ambient temperature (-23.73 °C to 21.40 °C), range of temperature (2.79 °C to 19.43 °C), dew point (-27.84 °C to 14.34 °C), wind speed (2.08 to 6.49 m/s), solar radiation (30.8 to 297.1 W/m2), and 2-wk lag (average of previous 2 wk's values) and monthly lag (average of previous 4 wk's values) of each weather variable. Toeplitz variance-covariance structure for repeated measures was used to determine the model to predict DMI, while accounting for the effects of body weight, dietary NEm, and other variables in the model. Two-week lag of ambient temperature interacted (P ≤ 0.005) with 2-wk lag of range of temperature, monthly lag of wind speed, 2-wk lag of solar radiation, and dew point to predict DMI. Interactions (P = 0.0001) between 2-wk lag of range of temperature vs. dew point and monthly lag of wind speed vs. 2-wk lag of solar radiation were also detected. This study reports important weather variables associated with differences in DMI of growing and finishing steers and will help improve the accuracy of DMI prediction equations for beef cattle. Improvements in the accuracy of predicting DMI should give producers better tools to plan and execute efficient feeding management programs. The R2 of the overall model was 0.8891.

Application and Study of kiln temperature control system based on PLC

Kiln is a kind of main heat consuming equipment built with refractory materials to calcine materials and products. The temperature control of kiln directly affects the efficiency of the system, product quality and output. In order to produce the desired product output and quality, the kiln temperature must be controlled within a certain range to meet the process requirements. Due to the uncertainty and large lag of kiln temperature, the traditional control can not guarantee the constant temperature. Now taking the kiln temperature as the research object, the PID control based on PLC controller is adopted for the temperature. The results show that the PID kiln temperature control based on PLC has ideal effect and wide application prospect.

Effects of Al2O3 content on the properties of BF slag and suitable fluxing regime for BF ironmaking with high Al2O3 content

ABSTRACT The difficulty of smelting high-alumina iron ore is that the Al2O3 content in the slag is too high, affecting the smooth running of the blast furnace. This work employed a combination of physical experiments and thermodynamic calculations to investigate the effect of Al2O3 content on blast furnace slag properties, including phase transition, viscosity, liquidus temperature, and slag structure. The results showed that a spinel phase appeared when the Al2O3 content was increased from 15wt% to 17wt%, and the liquidus temperature and viscosity of the BF slag were of therefore increased. For 17wt% to 20wt% Al2O3 content, the viscosity, liquidus temperature, and the ratio of complex structure content to simple structure content increased rapidly owing to slag structure polymerisation. Additionally, the viscosity and liquidus temperature of high-alumina blast furnace slag were negatively correlated with TiO2 content, but positively correlated with basicity. At approximately 5wt% TiO2 content, Ti(C, N) with a high melting point appeared in the molten iron, resulting in a rapid increase in the viscosity. Thus, it is recommended that the TiO2 content in the slag be less than 5wt% when the high-alumina iron ore is the main raw material of BF.

Establishment and Application of a Predictive Growth Kinetic Model of Salmonella with the Appearance of Two Other Dominant Background Bacteria in Fresh Pork.

To better guide microbial risk management and control, growth kinetic models of Salmonella with the coexistence of two other dominant background bacteria in pork were constructed. Sterilized pork cutlets were inoculated with a cocktail of Salmonella Derby (S. Derby), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli), and incubated at various temperatures (4-37 °C). The predictive growth models were developed based on the observed growth data. By comparing R2 of primary models, Baranyi models were preferred to fit the growth curves of S. Derby and P. aeruginosa, while the Huang model was preferred for E. coli (all R2 ≥ 0.997). The secondary Ratkowsky square root model can well describe the relationship between temperature and μmax (all R2 ≥ 0.97) or Lag (all R2 ≥ 0.98). Growth models were validated by the actual test values, with Bf and Af close to 1, and MSE around 0.001. The time for S. Derby to reach a pathogenic dose (105 CFU/g) at each temperature in pork was predicted accordingly and found to be earlier than the time when the pork began to be judged nearly fresh according to the sensory indicators. Therefore, the predictive microbiology model can be applied to more accurately predict the shelf life of pork to secure its quality and safety.

Effect of Calcination Temperature of Dolomite on Properties of Self-insulation Wall Materials

The environmental pollution problem of Sinochem Chongqing Fuling Chemical Co., Ltd. is serious. Fuling District Party committee and Fuling District government relocated the chemical plant as a whole and started the ecological restoration project. However, the investigation found that soil covering greening failed to fundamentally eliminate the harm caused by phosphorus slag to the environment. Therefore, the resource utilization of phosphorus slag is imperative. The application of dolomite rich phosphorus slag in the construction industry not only improves the environment, but also reduces the production cost of self-insulation wall materials. In this experiment, dolomite rich phosphorus slag was calcined at 600 ℃, 700 ℃ and 800 ℃ respectively to obtain light calcined dolomite, which was mixed into modified fly ash cement composite mortar to prepare self-insulation wall material. The mechanical properties, water absorption, bulk density and thermal insulation of the specimens were tested after curing for 7 and 28 days respectively. The conclusions are as follows: when the calcination temperature of dolomite rich phosphorus slag is 700 ℃, the specimen has the best mechanical properties, the lowest water absorption, the largest bulk density and the best thermal insulation.

Temporal pattern and risk factors for occurrence of Canine Rabies in Chennai

Rabies is one of the most important zoonoses resulting in a high case fatality rate in humans. Most of the human Rabies cases are due to dog bites which can be prevented by effective vaccination in dogs. Globally, epidemiological studies on understanding the seasonality and risk factors for occurrence in canines are limited. The present study aimed to understand the temporal pattern of Rabies occurrence in Chennai city of Tamil Nadu, India, and address the suggestive clinical signs for better clinical ante-mortem rabies diagnosis. Data of 598 suspected canine hippocampus brain smear samples with Seller's staining and/or FAT percent positivity of 71.57% (428/598) from March 2010 to February 2019 were included in this study. Cross-correlation between rabies cases and meteorological factors showed that maximum temperature (lag 15), morning relative humidity (lag 0 and lag 5) and evening relative humidity (lag 4) were significantly associated with rabies cases. Auto-Regressive Integrated Moving Average (ARIMA) model with exogenous variables (significant lags of meteorological variables) was used to fit the time series of canine Rabies in Chennai. In logistic regression analysis, the following risk factors were found to be playing a significant role in Rabies positivity viz., behavioural changes in dogs (P < 0.001), free-roaming, unprovoked biting, hyper salivation (P < 0.05), dog bite history and drop jaw (P < 0.01). Hence, the study results highlight the need for continuous surveillance of canine Rabies for devising and implementing future preventive strategies and is helpful to establish the above-identified risk factors as a criterion to help in clinical rabies diagnosis.

Geographical variation in the effect of ambient temperature on infectious diarrhea among children under 5 years

Understanding the geographical distribution in the association of temperature with childhood diarrhea can assist in formulating effective localized diarrhea prevention practices. This study aimed to identify the geographical variation in terms of temperature thresholds, lag effects, and attributable fraction (AF) in the effects of ambient temperature on Class C Other Infectious Diarrhea (OID) among children <5 years in Jiangsu Province, China. Daily data of OID cases and meteorological variables from 2015 to 2019 were collected. City-specific minimum morbidity temperature (MMT), increasing risk temperature (IRT), maximum risk temperature (MRT), maximum risk lag day (MRD), and lag day duration (LDD) were identified as risk indicators for the temperature-OID relationship using distributed lag non-linear models. The AF of OID incidence due to temperature was evaluated. Multivariable regression was also applied to explore the underlying modifiers of the AF. The geographical distributions of MMT, IRT, and MRT generally decreased with the latitude increment varying between 22.3–34.7 °C, −2.9–18.1 °C, and −6.8–23.2 °C. Considerable variation was shown in the AF ranging from 0.2 to 8.5%, and the AF significantly increased with latitude (95% confidence interval (CI): −3.458, −0.987) and economic status decrement (95% CI: −0.161, −0.019). Our study demonstrated between-city variations in the association of temperature with OID, which should be considered in the localized clinical and public health practices to decrease the incidence of childhood diarrhea.

Experimentally Implementing the Linear Nonisothermal Equation for Simultaneously Obtaining D- and z-Values of Salmonella Senftenberg in Skim Milk with a Differential Scanning Calorimeter

For bacteria with log-linear thermal inactivation kinetics in food, D-values are obtained in multiple isothermal inactivation experiments at different temperatures, and the z-value is obtained from these D-values. In a previous work, the cumulative lethality integral was mathematically solved in closed form when temperature in the food increased linearly with time. The solution revealed that each nonisothermal experiment could yield both D- and z-values, eliminating the need for getting multiple D-values to get a z-value. The present study reports on the first experimental implementation of this method of obtaining D- and z-values for Salmonella Senftenberg suspended in skim milk for which a differential scanning calorimeter (DSC) provided the required constant heating rate. The resulting D- and z-values were compared with those obtained from an isothermal method with capillary tubes. No significant differences in z-values were found between the two methods. The D-values also agreed but only after correcting the nonisothermal value for temperature lag in the DSC caused by the large sample size required. A 5 K/min heating rate was used in this comparison. Other rates were also investigated: 1, 3, 7.5, and 10 K/min. Although D- and z-values should be independent of DSC heating rate, heating rates of 1 and 10 K/min yielded values that were significantly different from the others; therefore, these rates cannot be recommended for use in this nonisothermal method.