Effects of Different Raw Materials and Additions on Wave Transparency of Alumina Fiber Products

Fiber products for microwave kilns were prepared using alumina fibers with alumina contents of 72 mass%and 80 mass%,and calcined alumina powder(4-6μm)as the main raw materials,silica sol as the binder,and cationic starch as the flocculant.Effects of different raw materials and their additions on the wave transparency of fiber products were researched.The results show that as the alumina fiber(72%)addition increases,the heating rate of the samples first decreases and then increases,and the corresponding wave transparency of the sample first increases and then decreases.When the alumina fibers addition is 40 mass%and the alumina powder addition is 30 mass%,the prepared microwave kiln lining material has a higher mullite content,which improves the wave transparency of the sample.The sample prepared from alumina fibers with an alumina content of 80%has a suitable glass-mullite phase ratio,performs lower overall dielectric constant and good wave transparency,and is a suitable lining material for microwave kilns.

Multi-Objective Adaptive Optimization Model Predictive Control:Decreasing Carbon Emissions from a Zinc Oxide Rotary Kiln

The zinc oxide rotary kiln,as an essential piece of equipment in the zinc smelting industrial process,is presenting new challenges in process control.China’s strategy of achieving a carbon peak and carbon neutrality is putting new demands on the industry,including green production and the use of fewer resources;thus,traditional stability control is no longer suitable for multi-objective control tasks.Although researchers have revealed the principle of the rotary kiln and set up computational fluid dynamics(CFD)simulation models to study its dynamics,these models cannot be directly applied to process control due to their high computational complexity.To address these issues,this paper proposes a multi-objective adaptive optimization model predictive control(MAO-MPC)method based on sparse identification.More specifically,with a large amount of data collected from a CFD model,a sparse regression problem is first formulated and solved to obtain a reduction model.Then,a two-layered control framework including real-time optimization(RTO)and model predictive control(MPC)is designed.In the RTO layer,an optimization problem with the goal of achieving optimal operation performance and the lowest possible resource consumption is set up.By solving the optimization problem in real time,a suitable setting value is sent to the MPC layer to ensure that the zinc oxide rotary kiln always functions in an optimal state.Our experiments show the strength and reliability of the proposed method,which reduces the usage of coal while maintaining high profits.

A Model for Predicting the Erosion Rate Induced by the Use of a Selective Catalytic Reduction Denitrification Technology in Cement Kilns Flue Gas

Selective catalytic reduction(SCR)is a technology by which nitrogen oxides are converted with the aid of a catalyst into diatomic nitrogen and water.It is known that the catalyst can be easily eroded if a cement kiln with a high-dust content is considered.To understand this process,numerical simulations have been carried out considering a single catalyst channel in order to study the collision and erosion of fly ash and catalysts at meso scale.Based on a response surface methodology,the effects of five factors on the erosion rate have been studied,namely,the catalyst particle velocity,the particle size,the particle concentration,the incidence angle and the catalyst porosity.The results show that the influence of particle velocity,particle size and particle concentration is statistically significant and the particle size and incidence angle have a significant effect on the erosion rate.A quadratic polynomial prediction model for the erosion rate of honeycomb catalysts in cement kiln SCR reactors is finally proposed to support the future optimization of these systems.

Research on Remote Fault Detection System of Ceramic Kiln Based on 5G and IoT Technologies

In order to overcome the defects of the existing technology that the detection of ceramic electric kiln faults takes a long time and costs a lot,an electric kiln control and fault detection device was designed.The working process of the device includes detection module,control module,start⁃stop module and switch module.The detection module detects the resistance circuit and sends a fault signal to the control module.The control module generates stop signal and fault information according to the fault signal,and starts the electric kiln when the fault signal is not received within the preset time.The start⁃stop module can monitor the internal temperature of the electric kiln and control the closing status of the switch module.The switch module is used to control the connection status of AC power and each resistance circuit in the kiln.Based on the 5G DTU or 5G module,the control module could send the information to mobile terminal under the ultra⁃reliable and low⁃latency communication(uRLLC)technical characteristics of 5G communication.

传染病流行期间定点收治医院医疗废弃物的“闭环式”管理

介绍传染病流行期间定点收治医院医疗废弃物的“闭环式”收、储、运模式,以及气化式回转窑无害化处理的工艺特点,为其他医院的医疗废弃物处理提供参考。

An Innovative Process for Direct Reduction of Cold bound Pellets from Iron Concentrate with a Coal-based Rotary Kiln

Successfully developed an innovative process of direct reduction of cold bound pellets from iron ore concentrate with a coal based rotary kiln, in comparison with the traditional direct reduction of fired oxide pellets in coal based rotary kilns , possesses such advantages as: shorter flowsheet, lower capital investment, greater economic profit, good quality of direct reduced iron. The key technologies , such as the composite binder and corresponding feasible techniques were employed in practice. A mill utilizing this process and with an annual capacity of 50 thousand ton DRI has been put into operation.

Influence of MnO_2 Mineralizer on the Crystal Structure,Properties of SiC Kiln Furniture Bonded with Fine Silicon Powder

The properties of SiC kiln furniture bonded with fine silicon powderare related to the bonder’s crystal structure. At high temperature, it will crystallize ina-cristobalite with great bulk effect. MnO2 mineralizer can make a-cristobalite convertto a-tridymite whose bulk effect is small. The crystal structure and its amount were investigated with XRD technique. The influence of different amounts of MnO2 on thecrystal structure and polycrystal transformation, and that of crystal structure on theproperties of kiln furniture were studied. The best proportion of MnO2 added was determined to be 2.0%.

Effects of Municipal Sewage Sludge on Fixation of Cr,Ni,Cu,and Zn during Co-processing of Heavy Metal-containing Waste in Cement Kilns

Cement raw meal with MSS and different heavy metals was blended to examine the fixation ratios, chemical species, and cement crystalline phases in clinkers. The results showed that blending MSS could decrease the fixation ratio of Cr, Ni, Cu, and Zn in the produced clinker by 5% to 25%. And Cr, Cu, and Zn were mainly incorporated into clinkers as metal silicates, Ni was mainly solubilized in Mg O to form magnesium nickel oxides, and the transition phases were mainly metal aluminum oxides as indicated by X-ray diffraction. The reduction of fixation ratios was likely attributed to the presence of impure elements, such as sodium and phosphorus in MSS. In addition, high concentrations（eg, 1.7 wt%） of chlorine in MSS led to metal chloride formation that could vaporize Cu, Cr, Ni, and Zn. To summarize, introducing MSS would decrease the fixation ratios of heavy metals due to the presence of impure elements, such as sodium and phosphorus and chlorine.

Grate-kiln pelletization of Indian hematite fines and its industrial practice

Indian hematite fines normally have a high iron grade and minor impurities; they are usually used as sinter fines for feeding into a blast furnace. In this work, the grindability properties of two kinds of Indian hematite fines and the roasting behaviors and induration characteristics of pellets made from these fines were revealed through experiments involving dry ball milling and small-scale and pilot-scale tests. In addition, the microstructures of the particles of ground India hematite fines and fired pellets were investigated using optical microscopy. On the basis of the results, a grate-kiln production line with an annual output of 1.2 Mt of oxidized pellets was established in India. This pellet plant operates stably and reliably, further confirming that preparing high-quality pellets with Indian hematite fines pretreated by dry ball milling is an industrially feasible process. ? 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Increasing Plant Availability by Mechanical Checking of the Cement Rotary Kiln Axis

A periodic check of the cement rotary kiln axis is needed withinthe framework of preventive ma- intenance for maintaining high plantavailability. The fourth generation 'KAS-4' measuring system wasdevel- oped by Wuhan University of Technology in 1999. The system canbe carried out with rotating or stationary kiln plant. The same istrue of the measurement of tire and supporting roller diameters, theclearance of tires, the po- sition of rollers, the machining of tiresand rollers, the slops of roller surfaces, the deflection of gear,the axis of kiln. The system has been applied to the measurement for10 set of cement rotary kiln in China.

Improvement of geotechnical properties of sabkha soil utilizing cement kiln dust

Improvement of properties of weak soils in terms of strength,durability and cost is the key from engineering point of view.The weak soils could be stabilized using mechanical and/or chemical methods.Agents added during chemical stabilization could improve the engineering properties of treated soils.Stabilizers utilized have to satisfy noticeable performance,durability,low price,and can be easily implemented.Since cement kiln dust(CKD) is industrial by-product,it would be a noble task if this waste material could be utilized for stabilization of sabkha soil.This study investigates the feasibility of utilizing CKD for improving the properties of sabkha soil.Soil samples are prepared with 2% cement and 10%,20% or 30% CKD and are tested to determine their unconfined compressive strength(UCS),soaked California bearing ratio(CBR) and durability.Mechanism of stabilization is studied utilizing advanced techniques,such as the scanning electron microscope(SEM),energy dispersive X-ray analysis(EDX),backscattered electron image(BEI) and X-ray diffraction analysis(XRD).It is noted that the sabkha soil mixed with 2% cement and 30% CKD could be used as a sub-base material in rigid pavements.The incorporation of CKD leads to technical and economic benefits.

The fouling properties of SiO2-CaO-P2O5 system in high-temperature rotary kiln phosphoric acid process

Kiln phosphoric acid(KPA)technology could produce P2O5 with high purity and has been applied in thermal phosphoric acid industry;however the formation of fouling in the high-temperature rotary kiln restricts the stable and long-term operation.In this paper,the reaction of phosphate ores with gaseous P2O5 was investigated in a high-temperature reactor,and the Ca O-SiO2-P2O5 ternary phase diagram was analyzed to understand the fouling formation mechanism.The results showed that the low-melting-point products,such as Ca(PO3)2and Ca2P2O7,are responsible for the fouling in the KPA process.In addition,a small amount of impurities,e.g.,aluminum and iron,could facilitate the generation of the low-melting-point products and cause serious fouling.Based on the high-temperature SiO2-P2O5 and CaO-SiO2-P2O5 phase diagram analysis,the control of Si/Ca molar ratio(e.g.,Si/Ca=2.0)was found to avoid fouling formation in the kiln.These results could provide the operation parameters of reaction temperature and feeds composition to suppress the fouling in the kiln reactor for the phosphoric acid production in industry.

Present Synthesizing Situation and Application Mechanism of Hercynite in Cement Kilns

The magnesia -hercynite bricks offer a new lining to rotary cement kiln. They are well adopted and widely used in the high temperature zone of cement kiln, and have obtained good performance at rigorous and severe working conditions. The synthesis of hercynite requires a suitable atmosphere with proper O2 partial pressures which makes sure FeO can stably exist at the synthesizing temperature. Current industrial production of hercynite mainly adopts fused method. The other method, sinte- ring method, is not mature and needs further research. The magnesia - hercynite brick shows high hot toughhess, high adhesion strength to kiln crust, and good corrosion resistance to alkali salt in cement kilns. The mismatching of thermal expansion between magnesia and hercynite can improve the thermal shock resistance of the bricks, but the oxidation of partial Fe^2＋ , the high temperature solution, and low temperature exsolution of transgranular secondary spinel lead to cubical expansion, .formation of more cracks, and poor thermal shock resistance of the bricks.

Mathematic simulation of heat transfer and operating optimization in alumina rotary kiln

Based on the analysis of material motion in the axial direction, heat transfer and mass transport processes in a rotary kiln, and combining with pulverized coal combustion, material pyrogenation, cooling of furnace wall finally, and heat transfer and mass transport equations, the combined heat transfer mathematical model for alumina rotary kiln was built up. According to the in-site real operation parameters, the heat transfer mathematical model was solved numerically for an alumina rotary kiln to predict the temperature profiles of gas and material in the axial direction. The results show that as the excess air coefficient reduces from 1.38 to 1.20, the temperature of the sintering zone increases and the length decreases. However, as the excess air coefficient reduces from 1.20 to 1.10, the temperature of the sintering zone decreases and the length increases. When the mixed coal amount at the end of kiln is reduced from 68.6 kg/t to 62.0 kg/t and the burned coal amount at the head of kiln correspondingly increases from 155.3 kg/t to 161.9 kg/t, the sintering zone temperature increases and the length reduces. The suitable excess air coefficient and mixed coal amount at the end of kiln are recommended for the rotary kiln operation optimization.

Mathematical Model for the Rotary Kiln Process and Its Application

A mathematical model to predict the operation behaviours of the rotary kiln process and to describe the axial distribution of process variables along the length of the reactor has been developed in present work.The model is established based on the principle of mass and heat balance in the system under a steady state with the consideration of kinetic characteristics of the processes.Four examples of the simulation processes in a pi- lot kiln and 3 commercial kilns by using the present mathematical model are given in this paper.The good agreement between the predicted results and the measured data has been obtained.

A New Kind of Eco-Cement Made of Cement Kiln Dust and Granular Blast Furnace Slag

A research project wus conducted to manufacture eco-cement for sustainable development using cement kiln dust（ CKD ） and granular blast furnace slag（ GBFS ）. In the project, the burning process and minerul compositions of CKD dinker were investigated. Different minerulizers such as CaSO4 and CaF2 , sulfur and alkali corttent were coasidered. The strength of CKD and GBFS eco-cement were evaluated. The results indicate the CKD clinker can not only form ordinary cement clinker minerals such as C3 S, C2 S and C4 AF , but also form such high-reuctive minerals as C4 A3 S and C. A7 · CaF2 . The CKD and GBFS eco-cement will have the similar strength to the Portland cement grade 32.5 when blend proportion is properly applied.

Application of the Hand-instrument of Measurement of Tyre Gap and Diameter in Cement Rotary Kiln

This article is concerned with the cement rotary kiln, thehand-instrument of measurements of tyre gap and the outer diameter.The accuracy of measurements of tyre gap and diameter is less than ±1 mm. The hand-instrument wins two patents in China. It has beenapplied to the measurement for 16 sets of cement ro- Tary kiln inChina.

Modeling of Rotary Kiln in Cement Industry

Cement production is a highly energy-intensive process, and the rotary kiln is the most important part of the process. Having a comprehensive model of the kiln in order to reduce manufacturing costs, better performance can be created. In this paper, the influence processes in a simulated cement rotary kiln and operating parameters on the output of the study were to develop and validate the systems using the same batch. The followings were examined: solid phase, gas and coating temperature change in a rotary kiln.