Research On Application Of Bluff Burner For Down-fired Boiler

With the great growth of energy consumption,the environmental pollution issues become more and more serious.Nowadays,the new energy utilization technology plays a very important role in energy engineering.Coal-fired electricity generation is one of China's major energy uses,but the utilization efficiency of coal burning is relatively low,especially when anthracite is used as combustion coal.The storage of anthracite reserves is very rich in China,but because of its low volatile content,high devolatilization temperature and low ignition speed,it is hard to be ignited or to burn up which results in lower efficiency of coal combustion.This paper introduces the main burning modes of anthracite,and analysis the advantages of the W-Shaped combustion mode compared with four corner tangential combustion in burning anthracite coal and also analyses the common unstable combustion problem appears of W-Shaped combustion mode.To solve this common issues,this paper introduces the improve technology,and analyses the steady burning mechanism of recirculation zone which produces when swirl burner is installed of bluff body device.In this paper,FLUENT software is used as a numerical simulation tool to the swirl burner applied in a W flame boiler as the research object.The simulate results of temperature field,velocity field,pathline and O2 concentration distribution under full load condition and low load condition is compared when a single burner is installed without or with bluff body structure.Compared to no bluff body condition,the following feature can be discovered while the burner is installed with bluff body: the temperature rises faster;the velocity gradient is larger;heat exchange is much intensely;the pulverized coal injection is ignited faster and quickly participate in combustion;the pathline clearly shows the return flow rolling up of high temperature flue gas feature.The compare result proves that the recirculation zone can be produced after the burner nozzle when the burner is equipped with a bluff body,so that the high temperature flue gas can be rolled up and the combustion of anthracite can be stabilized.Meanwhile,this paper uses a W-flame boiler as an actual example in which the study burner is applied and is burning with ultra low volatile anthracite in Vietnam.While the operation,it appears the following problems.The boiler is in unstable combustion situation and its fly ash is with high carbon content and the boiler efficiency is relatively low.Through the burner installation of bluff body structure solves these problems.The result of this example illustrates the steady burning positive affection of the bluff body burner in industrial applications.The positive significance of bluff body burner is proved.Based on the numerical simulation and industrial research of the bluff body burner,the design of using the bluff body device for the burner is determined.At present,the project is in the design stage.The research of this paper will provide some reference for the actual operation of the boiler in the future.