Influence of Arranging Tertiary Air on Aerodynamic Field in W-shape Flame Boiler

摘要

There are some obvious advantages of the W-shape flame boiler when anthracite and lean coal are burned .The factors of design and operation of this boiler will greatly influence boiler efficiency. W-shape flame burning technology will be widely used for the large amount of storage and consumption of anthracite and lean coal in China. So, it is very important to study all the factors which may affect combustion efficiency in W-shape flame boiler. This paper validates the DBC's (Dong Fang Boiler Co.Ltd) mended technology which is based on the W-shape flame boiler technology of FW (Foster Wheeler). The off gas that is used to transport pulverized-coal is sent to the furnace as tertiary air when the milling system changes from unit pulverized-coal system to indirect-firing system. This idea investigates the effect on aerodynamic field in furnace caused by the tertiary air. Results of the experiment show that the laying of tertiary air greatly influences the aerodynamic field. It is advantageous to organize W-shape air field in flame boiler when the tertiary air laid at the mid and lower furnace leans down with a small angle, because the road of main air flow is prolonged and the residence time of pulverized coal becomes longer. This angle is limited to be less than 15°the larger angle will causes slagging because the main airflow will sweep the furnace hopper. When tertiary air lies at the upside of furnace, the dual- v -shape flow field comes into being which can further prolong the road of main air flow and at the same time can make it easier for the pulverized coal ignition zone to be a high temperature area. But, what will attract our attention is that the range of the ratio of momentum flux becomes smaller in the dual- γ -shape field. The paper provides some useful data in regard to the problems of sending tertiary air into furnace of W-shape flame boiler with indirect-firing system. Also, some consultations and references for designs and recreations of boiler are present in this paper.