Numerical Simulation of Heat Transfer Process and Heat Loss Analysis in Siemens CVD Reduction Furnaces

The modified Siemens method is the dominant process for the production of polysilicon,yet it is characterised by high energy consumption.Two models of laboratory-grade Siemens reduction furnace and 12 pairs of rods industrial-grade Siemens chemical vapor deposition(CVD)reduction furnace were established,and the effects of factors such as the diameter of silicon rods,the surface temperature of silicon rods,the air inlet velocity and temperature on the heat transfer process inside the reduction furnace were investigated by numerical simulation.The results show that the convective and radiant heat losses in the furnace increased with the diameter of the silicon rods.Furthermore,the radiant heat loss of the inner and outer rings of silicon rods was inconsistent for the industrial-grade reduction furnace.As the surface temperature of the silicon rods increases,the convective heat loss in the furnace increases,while the radiative heat loss remains relatively constant.When the inlet temperature and inlet velocity increase,the convective heat loss decreases,while the radiant heat loss remains relatively constant.Furthermore,the furnace wall surface emissivity increases,resulting in a significant increase in the amount of radiant heat loss in the furnace.In practice,this can be mitigated by polishing or adding coatings to reduce the furnace wall surface emissivity.

Ammonia-induced CuO/13X for H_(2)S removal from simulated blast furnace gas at low temperature

Blast furnace gas(BFG)is an important by-product energy for the iron and steel industry and has been widely used for heating or electricity generation.However,the undesirable contaminants in BFG(especially H_(2)S)generate harmful environmental emissions.The desulfurization of BFG is urgent for integrated steel plants due to the stringent ultra-low emission standards.Compared with other desulfurization materials,zeolite-based adsorbents represent a viable option with low costs and long service life.In this study,an ammonia-induced CuO modified 13X adsorbent(NH_(3)–CuO/13X)was prepared for H_(2)S removal from simulated BFG at low temperature.The XRD,H_(2)-TPR and TEM analysis proved that smaller CuO particles were formed and the dispersion of Cu on the surface of 13X zeolite was improved via the induction of ammonia.Evaluation on H_(2)S adsorption performance of the adsorbent was carried out using simulated BFG,and the results showed that NH_(3)–CuO/13X-3 has better breakthrough sulfur capacity,which was more than twice the sulfur capacity of CuO/13X.It is proposed that the enhanced desulfurization performance of NH_(3)–CuO/13X is attributed to an abundant pore of 13X,and combined action of 13X and CuO.This work provided an effective way to improve the sulfur capacity of zeolite-based adsorbents via impregnation method by ammonia induction.

Direct reduction swelling behavior of pellets in hydrogen-based shaft furnaces under typical atmospheres

Hydrogen-based shaft furnace process is gaining more and more attention due to its low carbon emission, and the reduction behavior of iron bearing burdens significantly affects its operation. In this work, the effects of reduction degree, temperature, and atmosphere on the swelling behavior of pellet has been studied thoroughly under typical hydrogen metallurgy conditions. The results show that the pellets swelled rapidly in the early reduction stage, then reached a maximum reduction swelling index (RSI) at approximately 40%reduction degree. The crystalline transformation of the iron oxides during the reduction process was the main reason of pellets swelling. The RSI increased significantly with increasing temperature in the range of 850-1050℃, the maximum RSI increased from 6.66%to 25.0%in the gas composition of 100%H_(2). With the temperature increased, the pellets suffered more thermal stress resulting in an increase of the volume. The maximum RSI decreased from 19.78%to 17.35%with the volume proportion of H_(2) in the atmosphere increased from 55%to 100%at the temperature of 950℃.The metallic iron tended to precipitate in a lamellar structure rather than whiskers. Consequently, the inside of the pellets became regular, so the RSI decreased. Overall, controlling a reasonable temperature and increasing the H_(2) proportion is an effective way to decrease the RSI of pellets.

Outlier screening for ironmaking data on blast furnaces

Blast furnace data processing is prone to problems such as outliers.To overcome these problems and identify an improved method for processing blast furnace data,we conducted an in-depth study of blast furnace data.Based on data samples from selected iron and steel companies,data types were classified according to different characteristics;then,appropriate methods were selected to process them in order to solve the deficiencies and outliers of the original blast furnace data.Linear interpolation was used to fill in the divided continuation data,the Knearest neighbor(KNN)algorithm was used to fill in correlation data with the internal law,and periodic statistical data were filled by the average.The error rate in the filling was low,and the fitting degree was over 85%.For the screening of outliers,corresponding indicator parameters were added according to the continuity,relevance,and periodicity of different data.Also,a variety of algorithms were used for processing.Through the analysis of screening results,a large amount of efficient information in the data was retained,and ineffective outliers were eliminated.Standardized processing of blast furnace big data as the basis of applied research on blast furnace big data can serve as an important means to improve data quality and retain data value.

Quantificational indexes for design and evaluation of copper staves for blast furnaces

The quantificational and normative design is the precondition of improving the design of copper staves for blast furnaces. Based on a 3-dimensional temperature field calculation model, from the view point of heat transfer and long campaigns note with the core of forming accretion, the forming-accretion-ability （FAA） and the rib hot surface maximum temperature difference （ATmax） as quantificational indexes to direct and evaluate the design of copper staves for blast furnaces were presented. The application of the two indexes in design essentially embodies the new long campaigns in the stage of design. With the application of the two indexes, good results can be obtained. Firstly, it was suggested that the rib height of a copper stave can be reduced to 15 mm, which is a new method and theory for the reduction of copper staves. Secondly, the influence of insert on FAA and ATmax, is decided by the volume of insert. According to this, the principle of design for the hot surface geometry of copper staves was put forward that the ratio of the rib hot surface to the copper stave hot surface （abbreviated as the ratio of rib to stave） must be maintained in the range of 45% to 55%; for the present copper stave with a 35-40 mm thick rib, the ratio of rib to stave in the range of 50% to 55% can optimize the design of copper staves; for the copper stave with a smaller rib thickness, for example 15 ram, the ratio of rib to stave in the range of 45% to 50% can optimize the design of copper staves. It can be summarized that the thicker the rib thickness, the larger is the ratio of rib to stave. 2008 University of Science and Technology Beijing. All rights reserved.

Numerical Investigation of Fuel Dilution Effects on the Performance of the Conventional and the Highly Preheated and Diluted Air Combustion Furnaces

This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and the highly preheated and diluted air （1273 K with 10% O2 and 90% N2） combustion （HPDAC） conditions using an in-house computer program. It was found that by applying a combined diluted fuel and oxidant instead of their uncombined and/or undiluted states, the best condition is obtained for the establishment of HPDAC＇s main unique features. These features are low mean and maximum gas temperature and high radiation/total heat transfer to gas and tubes; as well as more uniformity of theirs distributions which results in decrease in NOx pollutant formation and increase in furnace efficiency or energy saving. Moreover, a variety of chemical flame shape, the process fluid and tubes walls temperatures profiles, the required regenerator efficiency and finally the concentration and velocity patterns have been also qualitatively/quantitatively studied.

Numerical analysis on Joule heating of double-loop channel induction furnaces

In order to investigate Joule heating power,a three-dimensional finite element model(FEM) was developed to predict Joule heating power in the channels of double-loop inductor. The simulated results were compared with experimental data from low load trials for a 400 kW inductor. The results,such as power factor and Joule heating power,show reasonable correlation with experimental data,and Joule heating rate reaches the maximum at the corners and the minimum at the centre of the cross-section area. With increasing relative permeability of iron core,length of coils,current frequency and resistivity of metal melt,the power factor and Joule heating power change. It is concluded that current frequency,the resistivity and length of the coil play a critical role in determining the power factor and Joule heating power,whereas relative permeability of the magnetic core shows no significant influence on them.

Improvement of fuel consumption and maintenance of heating furnaces using a modified heating pattern

This article studies the transient heat conduction in a slab when passing through various sections of the furnace, and focuses on the thickness of the scale layer formed on the slab. The transient heat conduction behavior of a slab in various sections of the heating furnace is analyzed using the Laplace transformation method, including the pre-heating zone, the first heating zone, the second heating zone, and the soaking zone. The heating pattern of the furnace is then modified to reduce fuel consumption. The simulation results show that the scale layer formed on the slab significantly influences the quality of the hot rolled coil formed, and how the furnace parameters affect the efficiency of the furnace and the quality of the coil.

Investigation on the relationship between hearth wall erosion and deadman permeability for large blast furnaces

In this study, the relationship between hearth wall erosion and deadman permeability was investigated based on the change in the hearth bottom and hearth sidewall temperatures. Additionally, the operation practice for controlling hearth wall erosion in the large No. 1 blast furnace at Baosteel was also investigated. The reasons for the decrease in the permeability of deadman coke were analyzed, and measures for improving the permeability of deadman coke and controlling hearth wall temperature rising were described. The results show that a decrease in deadman coke permeability is the main reason for refractory temperature increase and hearth wall erosion. This indicates the importance of monitoring changes in hearth working conditions and taking appropriate measures to maintain sufficient permeability of the deadman and balance the hot metal flow and drainage of slag. At this rate, the decline in the hearth bottom temperature and fast rising of the hearth wall temperature can be restrained.

Corrosion Mechanism of Alumina-magnesia Dry Materials for Smelting Manganese/chromium Steel in Coreless Medium Frequency Induction Furnaces

Alumina-magnesia dry materials are widely used in induction furnace linings, but they show different kinds of damage when melting different kinds of alloy steel. In this paper, the chemical composition, phase composition, and microstructure of the post-use dry materials for the working liners melting different kinds of steel were evaluated. Furthermore, the corrosion mechanism of the steel on the furnace lining materials was comprehensively analyzed. The findings reveal a significant ability of the Mn element in the molten steel to diffuse and penetrate into the refractories. Mn oxidizes to form MnO at the steel-refractory interface, and then forms a liquid phase with Al_(2)O_(3). The Cr element is dissolved into corundum and spinel of the refractories, resulting in lattice defects and structural damage of the materials. TiO2reacts with Al_(2)O_(3) to form Al_(2)TiO_(5), which plays a crucial role in preventing crack formation and propagation. Part of Ti4+dissolves into magnesia-alumina(MA), densifying the materials. TiO2also slows down the reaction between the Cr element and refractory components, further improving the corrosion resistance of the materials.

Temperature Prediction of Aluminum Alloy Work-Pieces in Aging Furnaces Based on Improved Case-Based Reasoning

The temperature of aluminum alloy work-pieces in the aging furnace directly affects the quality of aluminum alloy products. Since the temperature of aluminum alloy work-pieces cannot be measured directly, a temperature prediction model based on improved case-based reasoning (CBR) method is established to realize the online measurement of the work-pieces temperature. More specifically, the model is constructed by an advanced case-based reasoning method in which a state transition algorithm (STA) is firstly used to optimize the weights of feature attributes. In other words, STA is utilized to find the suitable attribute weights of the CBR model that can improve the accuracy of the case retrieval process. Finally, the CBR model based on STA (STCBR) was applied to predict the temperature of aluminum alloy work-pieces in the aging furnace. The results of the experiments indicated that the developed model can realize high-accuracy prediction of work-pieces temperature and it has good application prospects in the industrial field.

Calculations of Heat Transfer in Torch Furnaces by Gas Volume Radiation Laws

The results stemming from the calculation of heat transfer in torch furnaces by the laws, relating to radiation from solid surfaces and gas volumes are analyzed. The article presents the laws for radiation from gas volumes and the procedure for calculating heat transfer in torch furnaces, fire boxes, and combustion chambers, elaborated on their basis. The example of heat transfer calculation in a torch furnace is given, and it is significantly non-uniform in nature. Non-uniformity of heat flux distribution on heating surfaces is given. According to the results of calculations, a new furnace is designed to decrease the non-uniformity of ingot heating, fuel rate, and increase the furnace capacity. The calculation results of the distribution of heat fluxes on the heating surfaces are given in changing torch geometric dimensions. These results are confirmed by experimental studies.

Digital Kilns and Furnaces——the Development Direction of Industrial Kilns and Furnaces in the 21st Century

The digital manufacturing theory is applied to the special manufacturing equipments——industrial kilns and furnaces; the concept of digital kilns & furnaces is put forward. The present status of research and application for digital technologies in fuel industrial kilns & furnaces is also introduced. Then,take the case of gas fuel kilns & furnaces,their main key technical issues are discussed. Digital kilns & furnaces as an important constituent of the digital equipments are the crucial base of the digital manufacturing. The value of research on digital kilns & furnaces and the application prospect are undoubted. It will improve product quality,reduce the manpower cost,enhance product market competitive ability,promote comprehensively tradition industries such as ceramics,metallurgy industry,and so on.

Status and Progress of Refraetories for Aluminum Smelting Furnaces

Status and state-of-the-art progress on research,development and application of refractories for aluminum smelting furnaces and holding furnaces were reviewed and discussed in the present paper.The main types of aluminum smelting furnaces and smelting processes,and the service conditions of refractories and the requirements for refractory lining were also described and discussed.

The 4th International Exhibition on Refractories, Industrial Ceramics and Furnaces(RCF Expo'2003)Beijing, China, April 15-17, 2003In conjunction with China Refractories Seminar' 2003-Technology and Markets

Organizers and Sponsors: China Association of Refractories Industry The Chinese Society for Metals The Chinese Ceramic Society

TWO-DIMENSIONAL MATHEMATICAL MODEL OF COMBUSTION SPACE IN GLASS MELTING FURNACES

Under some assumptions and dividing the combustion space into several isothermal zones and isothermal surface elements, a two-dimensional mathematical model for combustion space in cross-fired glass melting furnaces was constructed. The finite element method and the Gauss integration were used to calculate direct ex-change areas, and a inverse matrix was used to obtained the total ex-change areas. The temperature distributions were obtained by itera-tions. Some results were presented to show the effects of the fire tem-perature distribution, the convective -heat transfer coefficients and the heat losses through crown surfaces on the temperature distributions.

Environmental-friendly Ramming Materials for Mud Package and Taphole of Large-scaled Blast Furnaces

The compositions, structures and properties of envi- ronmental-friendly ramming materials for mud package and taphole of large-scaled blast furnaces were studied. The results show that the formation of silica fibers makes structure of ramming materials dense. During the process of extruding mud and ramming materials, SiC is partly oxidized ; CaO , F% 03 and carbon penetrate towards the outer wall. The improvement of ramming materials can inhibit the penetration of molten slag, iron and carbon. The bulk density of environmental-friendly ramming ma- terials dried at 200 ℃ is 2.90 g · cm-3, the cold com- pressive strength of this kind of ramming materials dried at 200 ℃ is about 17. 0 MPa and fired at I 450 ℃ is about 39. 2 MPa.

Development and Application of Multi-phase Nitrides Bonded Silicon Carbide Lintel Blocks for Dry Quenching Furnaces

Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)as raw materials,and calcium lignosulfonate as the additive,batching,mixing,and molding on a vibration pressure molding machine,drying and then firing at 1420℃for 10 h in high-purity N2.The apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,and the linear expansion coefficient of the samples were tested.The phase composition and the microstructure of the samples at different nitriding depths(50,100,and 150 mm)were analyzed by XRD and SEM.The field application effects of the blocks were studied.The results show that:(1)the multi-phase nitrides bonded silicon carbide refractories can dynamically adjust their own phase composition and minimize structural and thermal stresses,improving the service life of key parts of dry quenching furnaces;(2)calcium lignosulfonate can improve the nitriding micro-environment of multi-phase nitrides bonded silicon carbide lintel blocks,successfully increasing the effective nitriding thickness of the blocks to 300 mm;(3)Sinosteel LI RR provides a unique concept in the design of materials and block types as well as the stable and scientific overall structure,promoting the industrialization process of dry quenching furnaces with long service life in China.

A Composite Model Predictive Control Strategy for Furnaces

Tube furnaces are essential and primary energy intensive facilities in petrochemical plants. Operational optimization of furnaces could not only help to improve product quality but also benefit to reduce energy consumption and exhaust emission. Inspired by this idea, this paper presents a composite model predictive control(CMPC)strategy, which, taking advantage of distributed model predictive control architectures, combines tracking nonlinear model predictive control and economic nonlinear model predictive control metrics to keep process running smoothly and optimize operational conditions. The controllers connected with two kinds of communication networks are easy to organize and maintain, and stable to process interferences. A fast solution algorithm combining interior point solvers and Newton's method is accommodated to the CMPC realization, with reasonable CPU computing time and suitable online applications. Simulation for industrial case demonstrates that the proposed approach can ensure stable operations of furnaces, improve heat efficiency, and reduce the emission effectively.

Technical Questions in Castables Innovation for Main Iron Trough in Large-scaled Blast Furnaces of WISCO

The technical .wtors of castables innovation of matin iron trough in blust furnaces of WISCO in recent ten years were analyed, and corrosion process of dense corundum, sub-white corundum and brown corundum aggregates in the castables for the main iron trough was researched. It is regarded tha.t there is no inevitable relation between castables properties and service life, and it must be considered that whether the normal technical in- dex in. the stan＆trd can be used as judgment basis. Based on the improvement of matrix, the service hfe （once throughput of hot metal ） of castables used in main iron trough increases from 90 000 tons to 140 000 - 180 000 tons ; the properties of different raw materials are Jidly applied, and structure improvement of iron trough and progress of material technique are very important reasons.