Novel Flexibilizer for Cement Rotary Kiln Bricks

Computational fluid dynamics (CFD) has been used to study the devolatilization and combustion of large particles of shredded scrap tire “rubber” and pulverized pine wood “biomass” in a rotary cement kilns. The CFD model constitutes of modeling the hydrodynamics within the rotary kiln, heat transfer, devolatilization and co-combustion of rubber and biomass blends. Equivalent particle diameters of 1 mm and 2 mm for biomass and rubber, respectively, were used to simulate the process conditions and co-combustion in cement rotary kilns. The ratios of biomass substitution were varied from 5% to 20% on mass basis. The effect of the percentage of biomass content on the temperature distribution and devolatilization rate as well as wall heat transfer rate are presented. Results indicate that up to 20% biomass blend provides improved combustion characteristics compared with combustion of scrap tire alone. Further, the devolatilization rate was found to improve remarkably when scrap tire is blended with biomass. Most importantly, the biomass blend was found to increase the flame spreading and penetration, consequently improving the wall heat transfer rate, therefore providing favorable conditions for heat transfer to the cement clinker. The present study provides additional knowledge for future investigations on the use of biomass residues and some industrial wastes as alternative fuels for rotary cement kilns. That is, the use of alternative fuels in rotary cement kilns has a potential for economic improvement and environmental sustainability.

The object of research is high-temperature thermal units – rotary kilns. Rotary kilns are used in various industries. The specified equipment has high energy consumption, which is due to the operating conditions of the kiln units in compliance with a number of technological requirements for thermal conditions. At the same time, the problem of high energy intensity is aggravated by the low level of useful energy resources. One of the most problematic places is the thermal and operational characteristics of rotary kilns, as well as the use of lining with increased thermal resistance.Physical and mathematical models are used. It is proposed to calculate a rotary kiln for the production of cement with a size of 5x185 m and a capacity of 75 t/h. A mathematical model is obtained for computer simulation of technological processes in rotary cement kilns. The possibilities of reducing fuel consumption by increasing the thermal resistance of the lining of a rotary kiln are considered. The most energy-intensive zones are determined and the effect on the thermal efficiency of using additional thermal insulation in various energy zones in a rotary kiln is analyzed. Calculations and the results of a numerical experiment are presented. The most rational areas for the use of lining with additional thermal insulation are determined. It is found that with the integrated application of the proposed method, fuel consumption in a thermal unit can be reduced by 9 %. And an increase in the thermal resistance of the lining installed in high temperature zones will increase the energy efficiency of the thermal unit. A significant advantage of this method is the fact that an increase in kiln productivity does not require additional fuel consumption, an increase in temperature, or an increase in the enthalpy of combustion products.In the future, it is planned to study the mechanism for establishing a heat-insulating layer in the refractories of the lining, determining their optimal thermal efficiency and stress-strain state to eliminate the possibility of destruction. As well as determining the optimal structural form of the refractory and the cell with thermal insulation.

10 - Rotary Kiln Minerals Process Applications

In this research, the implementation of shell of kiln problem has been discussed. The results are analysed in detail in this research for fatigue life for the shell of a kiln. In this work, the shell of the kiln has been modelled by Solid Works. This simulation showed how the most relevant aspects of the developed work presented in this paper can contribute to the state-of-the-art of the analysis of fatigue life of rotary cement kiln technique with innovative ideas and strategies. It also reviews that the obtained results achieve the proposed objectives. Based on the FEA the transfer matrices and overall transfer equation are developed to calculate natural frequencies, and response overall motion equation is established for response analysis. Due to the dimensionality of the problem addressed, the research specification has to set limits to the applicability of the research by selecting only mechanical load problems in rotary cement kiln tasks and goal-seeking to predict the fatigue life simulation investigated. From the simulation, model and boundary conditions are defined. Crack growth behaviour in the rotary kiln was predicted.

Rotary cement kilns are used for converting calcineous raw meal into cement clinkers. In this paper, we discuss and evaluate possible ways of reducing energy consumption in rotary cement kilns. A comprehensive one-dimensional model was developed to simulate complex processes occurring in rotary cement kilns. A modeling strategy comprising three submodels, viz. a model for simulating the variation of bed height in the kiln, a model for simulating reactions and heat transfer in the bed region, and a model for simulating coal combustion and heat transfer in the freeboard region, was developed. Melting and formation of coating within the kiln were accounted for. Combustion of coal in the freeboard region was modeled by accounting for devolatilization, finite-rate gas-phase combustion, and char reaction. The simulated results were validated with the available data from three industrial kilns. The model was then used to understand the influence of various design and operating parameters on kiln performance. Several ways of reducing energy consumption in kilns were then computationally investigated. The model was also used to propose and to evaluate a practical solution of using a secondary shell to reduce energy consumption in rotary cement kilns. Simulation results indicate that varying kiln operating variables, viz. solid flow rate or RPM, can result only in small changes in kiln energetics. Use of a secondary shell over the kiln and energy recovery by passing air through the annular gap between the two appears to be a promising way to achieve significant energy savings. The developed model and the presented results will be useful for enhancing the performance of rotary cement kilns.

Bayesian Network is one of the most efficient and reliable method in data mining, and Bayesian Network structure learning is a key link in the process of Bayesian Network research. Aiming at the problem of the classic Hill-Climbing algorithm is easy to fall into local optimum and low in efficiency, establishing the Most Weight Supported Tree by calculating the mutual information, and combining the Most Weight Supported Tree and the simplified Hill-Climbing algorithm, proposes a new improved Bayesian Network structure learning algorithm. Comparing with the classic Hill-Climbing algorithm and K2 algorithm, the simulation experiments shown that the improved algorithm not only can obtain a high accuracy rate model, but improve the efficiency of building model. Based on the improved algorithm and combined with JiDong cement's cement rotary kiln operating data, we can establish the fault diagnosis model of cement rotary kiln and realize a precise and rapid fault diagnosis.

Article analyses modern machine vision-based approaches of the rotary kiln monitoring and control which reduces energy consumption and improve clinker quality. Article describes fuzzy advising control unit developed by the authors. It based on sintering zone state assessment, the kiln rotation period and the relative change of the exhaust gases temperature. Advising control rule base for rotary cement kiln of wet technological process is developed. Structure of fuzzy control system is proposed on the basis of advising control unit. It is applicable both independently and as a part of the existing rotary kiln control systems.

Granular materials flow is discussed by different models. These models are 2D and each of them includes some special effects of two phase flow. For simulating the 3D flow of granular materials in rotary kilns, a model based on finite volume method (FVM) is presented which includes axial and rotational motion and also all of the effects of two phase flow such as: viscosity effect, particle size, rotating velocity of kiln, kiln tilt, etc. This method is used according to a real kind of rotary kiln and hypothetical clogging inside of kiln. The simulation results in both 2D and 3D views are presented in this article. These results are compared with Kramer’s model and they are acceptable. Also in this simulation, granular flow over the clogging is reviewed by using hypothetical clogging in the rotary cement kiln.

Numerical modeling of a rotary cement kiln with improvements to shell cooling

Portland cement is produced by one of the most energy-intensive industrial processes. Energy consumption in the manufacture of Portland cement is approximately 110–120 kWh ton−1. The cement rotary kiln is the crucial equipment used for cement production. Approximately 10–15% of the energy consumed in production of the cement clinker is directly dissipated into the atmosphere through the external surface of the rotary kiln. Innovative technology for energy conservation is urgently needed by the cement industry. In this paper we propose a novel thermoelectric waste-heat-recovery system to reduce heat losses from cement rotary kilns. This system is configured as an array of thermoelectric generation units arranged longitudinally on a secondary shell coaxial with the rotary kiln. A mathematical model was developed for estimation of the performance of waste heat recovery. Discussions mainly focus on electricity generation and energy saving, taking a Φ4.8 × 72 m cement rotary kiln as an example. Results show that the Bi2Te3–PbTe hybrid thermoelectric waste-heat-recovery system can generate approximately 211 kW electrical power while saving 3283 kW energy. Compared with the kiln without the thermoelectric recovery system, the kiln with the system can recover more than 32.85% of the energy that used to be lost as waste heat through the kiln surface.

In this paper, based on analysis of the chemical and physical processes of clinker formation, a heat flux function was introduced to take account of the thermal effect of clinker formation. Combining the models of gas−solid flow, heat and mass transfer, and pulverized coal combustion, a set of mathematical models for a full-scale cement rotary kiln were established. In terms of commercial CFD code (FLUENT), the distributions of gas velocity, gas temperature, and gas components in a cement rotary kiln were obtained by numerical simulation of a 3000 t/d rotary kiln with a four-channel burner. The predicted results indicated that the improved model accounts for the thermal enthalpy of the clinker formation process and can give more insight (such as fluid flow, temperature, etc,) from within the cement rotary kiln, which is a benefit to better understanding of combustion behavior and an improvement of burner and rotary kiln technology.

A theoretical analysis on combustion intensification for blended coal in rotary cement kiln

In order to solve the problem that the temperature field in cement rotary kiln can not be monitored in real time,this paper proposes a novel soft-sensing method for temperature field in rotary kiln based on mechanism-and-data-driven.This paper firstly uses the CFD (Computational Fluid Dynamics) technology to establish a finite element model of the rotary kiln to simulate the combustion process in the kiln,and calculates the temperature field in the kiln under the different conditions of temperature of secondary wind,feed coal amount,and velocity of swirl and axis wind.Then, the BPNN (BP Neural Network)is trained using the data set obtained from the numerical simulation of the finite element model, thereby obtaining a soft-sensing model of the temperature field in the kiln.The method can predict the temperature distribution in the kiln in real time by several measurable variables in the field,and the visualization of temperature distribution in rotary kiln is given.

Energy audit and waste heat recovery from kiln hot shell surface of a cement plant

Significant developments in automatic regulation of the burning process in rotary cement kilns have occurred in the last decade, but general application of control devices has proceeded slowly. Indeed, neither the real import of the subject nor the extent of the progress is yet widely appreciated, though there are sufficient installations of various equipment to demonstrate the worth of a scientific approach to a problem which has been a typical rule-of-thumb operation. This paper discusses achievements in the field through reference to diagrams, charts, and illustrations in order to bring about a more universal understanding and to establish a background for additional thought which may encourage further experimentation. Moreover, although the discussion pertains especially to cement-clinker burning, the same basic principles of control are applicable to many other manufacturing processes employing rotary kilns.