Low NOx Emission Technology for CFB Boilers
High efficiency and low NOx combustion technology is realized by optimizing the combustion structure in the furnace, reasonable material circulation control, air-staged combustion and flue gas recirculation. It emphasizes the reasonable low oxygen classification of secondary air and the construction of ideal material bed fluidization under the condition of low primary air rate. Focusing on four aspects of optimizing the material fluidization inside the furnace, improving the characteristics of ignition and burnout, ensuring or improving the thermal efficiency of the boiler, optimizing the parameters of steam, water, air and flue gas, the following four technologies will be implemented.
Secondary air system transformation technology
It can realize air-staged combustion along the vertical and horizontal direction of the furnace, adjust the furnace temperature field so there will be no massive oxygen-rich high-temperature area or significant oxygen-poor area, and improve the evenness of furnace temperature and the reasonable combustion share distribution.
Flue gas recirculation modification technology
On the premise of ensuring fluidization efficiency, introduce the low-oxygen flue gas at tail end into the primary air system. This will reduce the oxygen content in the primary air and dense phase area, and also restrain the bed temperature, thus creating conditions for reasonable air classification.
Cyclone separator efficiency technology
It improves separation efficiency through inlet reshaping and center cylinder optimization, increases circulating ash amount to reduce bed temperature in dense phase area, enhances furnace outlet temperature, improves boiler load capacity and SNCR denitration efficiency indirectly.
Furnace bottom air distribution evenness technology
The technology specially optimizes the design of the air inlet mode of the furnace bottom air chamber, adjusts the air hood resistance distribution in different air volume distribution areas, improves the air distribution evenness, eliminates dust leakage in the air chamber, and solves the deviation of the operating bed material and the uneven bed temperature problem.
Low NOx emission technology for CFB boilers has been widely used in over 60 boilers with capacity ranging from 75t/h to 1025t/h till middle of 2020.