Study On Key Technologies Of Digital Simulation Of Calciner Based On Virtual Prototyping Technology

According to the fact that although the building material manufacturing industry is large in scale, but it has problems of high energy consumption and pollution. In this thesis, a reinforced suspension precalciner of 2500t/d is taken as an example to simulate its internal working process based on virtual prototyping technology.Virtual prototyping technology is a digital design method base on virtual prototype. By build the virtual prototype of calciner, the internal working process can be simulated in all respects and provide a convenient and intuitionistic CAD plat for optimization of calciner design.The flow field in precalciner system is very complex as well as the reactions of fuel combustion and raw materials decomposing, which are influenced by each other and taken place in suspension of the air flow. The simulation technology based on computational fluid dynamics (CFD) can accurately predict the flow, heat transfer, combustion, chemical reaction and multiple phase flow. It is also a good method to predict the internal process in calcnier.In this thesis, a numerical model is presented of the flow and transport processes taking place in an industrial RSP calciner of 2500t/d. First, it's the feature of its internal flow field is measured by cold model test. According to the results of cold model test, the flow field is simulated by k-εtwo equation turbulence models. Movement of raw material and coal particle is simulated by the particle stochastic trajectory model. This model is capable in simulating particle with complicated experience. It also enables to simulate coupling interaction between gas phase and particle phase, turbulence diffusion of particle is also regarded in this model. Non-premixed combustion model is adopted in simulating coal combustion; the model of Kobayashi is used for devolatilization model; radiation of the combustion is expressed with the P-1 radiation model and kinetic/limited diffusion rate model is adopted for char combustion. The method of probability density function (mixture fraction/PDF) is used for the chemical reaction models in coal combustion. In this way, the distributions of fluid velocities, temperatures and concentrations of the reactants and products as well as the trajectories of particles and their interaction with the gas phase are calculated. On the base of these results the calcination rate can be determined by contractive cylinder and sphere model.The simulating result predicts the flow field, the particle movement and the coal combustion, which is coincident with the flow tendency. The result provides useful information for analyzing the kinetics regulation and reaction in precalciner, and also allow estimations to be made and conclusions to be drawn that help in the optimization of a given calciner.Petroleum coke is the main byproduct of the oil refining industry. It is regarded as an economical alternative fuel for the pulverized coal in high energy consumption cement production. The present article is devoted to introduce the research works on make use of petroleum coke as a substitutional fuel of calciner, which consists of two major parts. In the first part, the basic properties of the petroleum coke and its characteristics of grindability, devolatilization, ignition and combustion were investigated by serials of experiment. And in the second part, a numerical model was also presented to simulate the combustion processes taking place in an industrial reinforced suspension calciner. The results of study show that petroleum coke is a suitable fuel for RSP calciner.As the environment protection is held in high regard today, the regulation for the NOx emission for cement industry is much stricter. In this thesis, the mechanism of NOx generation is deeply discussed. In the simulation of thermal NOx and fuel NOx, the influence of turbulence is taken into consideration and time-mean reaction rate is solved by probability density function (PDF) method. The simulation result can predict the distribution of the NOx in the calciner and the measure to reduce the NOx emission is put forward for RSP calciner.