New Technology for Control of N2O Emissions from Fluid Bed Combustors

该计划旨在开发一种控制流态化燃煤燃烧器N2O排放的新方法，包括向离开流态化床的烟道气中注入非常低水平的钠蒸汽。第一阶段工作的目标是：(1)证明在与燃煤沸腾燃烧器相关的条件下，钠注入可以基本上完全分解N2O；(2)获得化学动力学数据，以便与动力学计算的预测进行比较；以及(3)完成这一比较。实验室实验将在一个由四个子系统组成的系统中进行，即固定气体和蒸发液体混合系统、钠蒸发器、反应器和分析装置。将采用的反应堆由一根石英管组成，一段钢管伸入其中，主流气体通过产生的环空，氮-钠混合物通过钢管。分析系统将以N2O的NDIR仪器为中心，分析系列还包括CO分析器、脉冲荧光SO2分析器和化学发光NOx分析器。第一阶段研究的成功完成将为这一过程提供实验室规模的演示，并使人们对所涉及的化学物质有一个清晰的了解。为了燃烧低SOx和NOx排放的煤，人们在沸腾床燃烧技术上投入了大量的精力。不幸的是，这种技术方法导致产生大量的N2O排放，这是一个令人无法接受的严重缺陷，因为N2O既是一种温室气体，也是消耗臭氧层的主要贡献者。因此，开发一种解决这一问题的方法对燃烧煤的沸腾床燃烧器的可行性具有重要意义。

This program is aimed at development of a novel method of controlling N2O emissions from fluidized bed coal combustors, involving injection of sodium vapor at very low levels into the flue gas leaving the fluidized bed. The objectives of the Phase I effort are: (1) Demonstrate that sodium injection can cause substantially complete decomposition of N2O at conditions relevant to coal-fired fluid bed combustors; (2) Obtain chemical kinetic data for comparison with predictions of kinetic calculations; and, (3) Complete that comparison. Laboratory experiments will be carried out in a system consisting of four subsystems, a system for blending fixed gases and vaporized liquids, a sodium vaporizer, a reactor, and an analytical train. The reactor to be employed consists of a quartz tube into which a length of steel tubing projects, with the main flow gas going through the resulting annular space and the nitrogen-sodium mixture through the steel tubing. The analytical system will be centered around an NDIR instrument for N2O, with the analytical train also including a CO analyzer, a Pulsed Fluorescent SO2 analyzer, and a Chemiluminescent NOx analyzer. Successful completion of the Phase I studies will provide a lab-scale demonstration of the process and provide a clear understanding of the chemistry involved. Considerable effort has been expended on development of fluid bed combustion technology for burning of coal with low SOx and NOx emissions. Unfortunately, this technology approach leads to production of copious amounts of N2O emissions, an unacceptably serious drawback since N2O is both a greenhouse gas and a major contributor to depletion of the ozone layer. Accordingly, development of a means of dealing with this problem is of major importance to the viability of fluidized bed combustors for burning of coal.