What are the options for reducing nitrogen oxide emissions in lime kilns
The lime kiln produces nitrogen oxides during the production process, mainly from the thermal NOx generated by the reaction between nitrogen and oxygen in the air during high-temperature fuel combustion. It is crucial to adopt effective emission reduction technologies to achieve environmental standards and sustainable development.
The current technological path is mainly divided into two categories: combustion process control and end of pipe treatment. Combustion control is the core of source emission reduction. By using staged combustion technology and adjusting the fuel to air ratio, a local reducing atmosphere is created in the kiln, which can effectively suppress the generation of NOx. Low nitrogen burners reduce the production of thermal NOx by finely controlling the mixing process of fuel and air, thereby lowering the local peak temperature of the flame. In addition, optimizing process parameters such as calcination temperature and excess air coefficient are also economically effective auxiliary means.
When source control cannot meet strict emission standards, end of pipe treatment technology is essential. Selective non catalytic reduction technology involves injecting an amino reducing agent into the flue gas within a specific temperature window to react with NOx and generate nitrogen gas. This technology is suitable for the medium temperature range and has a lower investment cost. Selective catalytic reduction technology, under the action of a catalyst, enables efficient reaction between the reducing agent and NOx at lower temperatures, resulting in extremely high denitrification efficiency, reaching over 90%, making it the mainstream choice to meet ultra-low emission requirements.
The selection of technology requires comprehensive consideration of factors such as initial emission concentration, target emission value, investment and operating costs, and adaptability to kiln operating conditions. Building a multi-level technological combination from source control to end of pipe treatment is a feasible strategy for achieving deep denitrification of lime kilns.
