组合涂覆SCR催化剂的扩缩通道蓄热体传热脱硝性能的数值模拟

蜂窝蓄热体表面涂覆中温钒基SCR催化剂(V₂O₅-WO₃/TiO₂)，可实现余热回收和烟气脱硝双重功效，但钒基催化剂在烟气出口侧的低温区脱硝效果不理想。新型纳米多孔结构的铜基SCR催化剂(5%CuO-40%HPW/Popcarbon)能在低温条件下高效工作。通过在现有钒基SCR蜂窝蓄热体低温侧表面涂覆这种铜基催化剂，并借助扩缩通道强化传热传质进一步提高复合蓄热体传热和脱硝性能。在对Fluent软件二次开发基础上，采用多孔介质方法描述催化层烟气SCR脱硝，建立烟气-空气切换条件下复合SCR蜂窝蓄热体内非稳态传热脱硝的数值模型。借助该模型，探究催化剂涂覆方案和结构参数对复合蓄热体传热和脱硝性能的影响。结果表明：扩缩角为15°的组合涂覆型SCR蓄热体具有良好整体性能，其能量回收率(ERR)和脱硝效率(η)分别比涂覆单一钒基催化剂的直通道蜂窝蓄热体提升10.1% (58.2% vs 48.1%)和26.7% (92.4% vs 65.7%)。本研究结果可为工业锅炉的节能和氮氧化物(NO_x)减排提供参考。

A numerical simulation of on heat transfer and denitrification performances for regenerators with expansion and contraction channels coated by SCR catalysts

The dual effects of waste heat recovery and flue gas denitrification was obtained by coating Vanadium SCR catalysts of medium temperature (V2O5-WO3/TiO2) on honeycomb regenerators, however, the denitrification performance of Vanadium catalysts is unsatisfactory in the low temperature zone approaching flue gas outlet. Novel Copper-based SCR catalysts of nano porous structure (5%CuO-40% HPW/Popcarbon) were reported to work efficiently under the condition of low temperature. In the current work, to obtain better heat transfer and denitrification performances, the novel Copper-based SCR catalysts are applied to the low-temperature surface of honeycomb regenerators coated with Vanadium catalysts, and expansion and contraction channels are employed to strengthen the heat and mass transfer rates in composite regenerators. With the secondary development of Fluent software, the numerical model of novel composite SCR honeycomb regenerators is established, where the SCR denitrification of flue gas in porous catalyst layers is coupled with the unsteady conjugate heat transfer with air and flue gas flowing through regenerators alternately. With the current model, the effects of catalyst coating scheme and structural parameters on the thermal and denitrification performances are explored for the novel composite regenerators. Numerical results show that the composite SCR honeycomb regenerators with an expansion and contraction angle of 15° can generate a good overall performance, whose energy recovery ratio (ERR) and denitrification efficiency (η) are 10.1% (58.2% vs 48.1%) and 26.7% (92.4% vs 65.7%) higher than those of straight-channel regenerators coated with a single Vanadium-based catalyst, respectively. The results of this study can provide a reference for energy saving and reducing nitrogen oxide (NOx) emissions in industrial boilers.