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Coal America’s Energy Future phần 2

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và nhiên liệu NOX có nguồn gốc từ nitơ hữu cơ bị ràng buộc được tìm thấy ở các mức độ khác nhau trong tất cả các than. Kiểm soát của các khí thải NOX được thực hiện trong đơn vị PC / CFB thông qua một sự kết hợp trong lò kiểm soát của quá trình đốt cháy và hệ thống giảm đốt. | Overview of Nitrogen Oxides Nitrogen oxides are byproducts of the combustion of virtually all fossil fuels. The formation of NOx in the combustion process is a function of two reactions sources thermal NOx originates from the nitrogen found in the air used for combustion and fuel NOx originates from organically bound nitrogen found at varied levels in all coals. Control of NOx emissions is accomplished in PC CFB units through a combination of in-furnace control of the combustion process and post-combustion reduction systems. Combustion NOx Control Advanced low NOx pc combustion systems widely used today in utility and industrial boilers provide dramatic reductions in NOx emissions in a safe efficient manner. These systems have been retrofitted to many existing units and are reducing NOx emissions to levels that in some cases rival the most modern units. The challenges are considerable given that the older units were not built with any thought of adding low NOx systems in the future. Low NOx combustion systems can reduce NOx emissions by up to 80 from uncontrolled levels with minimal impact on boiler operation and they do so while regularly exceeding 99 efficiency in fuel utilization. Low NOx firing systems are standard equipment on new PC units. Advanced low NOx systems start with fuel preparation that consistently provides the necessary coal fineness while providing uniform fuel flow to the multiple burners. Low NOx burners form the centerpiece of the system and are designed and arranged to safely initiate combustion and control the process to minimize NOx. An overfire air OFA system supplies the remaining air to complete combustion while minimizing emissions of NOx and unburned combustibles. Distributed control systems DCS manage all aspects of fuel preparation air flow measurement and distribution and flame safety and also monitor emissions. Cutting-edge diagnostic and control techniques using neural networks and chaos theory assist operators in maintaining .