Numerical Simulation Of The Coal Combustion And NO For Mation In A Precalciner

Precalciner is the key equipment of the new type dry-process cement production system, 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, are taken place in suspension of the air flow. For these reasons, it is difficult to research the precalciner system. At the same time, developing low NOX technology and low NOX equipment have become the inexorable trend with strict NOX emission standards. Precalciner is a key equipment to implement the low NOx technology. Therefore, it is significant to study the flow distribution of coal combustion as well as NOX formation mechanism and control technology for cement precalciner product system.Advance in NOX formation and control in the world was analyzed in this paper. CFD numerical simulations of three-dimensional turbulent flow in 1000t/d Spouting Precalciner were studied by using FLUENT software. The chemical and physical processes of clinker formation were analyzed in detail. Combining with models of coal combustion and NOx formation, a set of mathematical models for the precalciner was established. Besides, mechanism of NOx formation and reduction were deeply analyzed in this dissertation. Temperature,ammonia injection and divided coal,were considered to NOx removal efficiency.Through the simulation, the following conclusion can be got: Coal was embedded in the space below after entering the precalciner with air - fume flow, the best region of coal cobustion was in the lower part of the body, and temperature is distributed in the precalciner pipe , export temperature was higher. The distribution of temperature was almost uniform, NO was formed around the district of coal combustion, thermal NO and fuel NO were two formation ways and the fuel NO was the main type of NO way in a precalciner. Besides, when ammonia was injected from the bottom of the precalciner, the NO emission was reduced obviously. The NO removal efficiency could reach eighty nine percent with eight percent concentration of ammonia in the flue gas. The formation of NO can be reduced through divided coal, also the furnace temperature field is more uniform.The simulating result is coincident with the flow tendency. The result provides useful information for analyzing the kinetics regulation and reaction in the precalciner, and also gives important theoretical basis for structure optimizing and practical operation parameter selecting of the precalciner. The reference is provided for the study of the coupling of coal combustion and calcium carbonate decomposition as well as the development of NO removal technique.