Perforated Spiral-Insert Catalytic Tube for Enhanced CO Catalytic Oxidation: CFD Modeling and Parameter Optimization

To address the challenge of efficient catalytic elimination of carbon monoxide (CO) generated from spontaneous coal combustion in goaf and blasting operations in underground coal mines under low-velocity laminar flow conditions, we propose a perforated spiral-insert catalytic tube. The design inserts a spiral vane with surface micro-holes into a straight tube; the vane surface and internal pore walls are coated with a CuMnOx catalyst. A porous medium equivalent model describes the flow and catalytic reaction characteristics in the perforated region. A three-dimensional Computational Fluid Dynamics (CFD) model coupling flow, mass transfer, and surface catalytic reactions is developed. After grid independence verification, three sets of L9 orthogonal experiments systematically investigate the effects of inlet velocity, helix pitch, vane height, opening ratio, and pore diameter on CO conversion and flow resistance. Range analysis, variance analysis, and the comprehensive performance factor are used for multi-objective optimization. PEC results show that inlet velocity is the primary factor affecting both conversion and comprehensive performance, and its dominance is independent of the number of vanes. At a low velocity of 0.2 m/s, the four-vane configuration achieves a maximum conversion of 51.07%. For a balanced trade-off between conversion and flow resistance, four vanes with a high opening ratio, large pore diameter, and large helix pitch yield the best comprehensive performance. If low resistance is the primary goal, two vanes with a high opening ratio achieve a resistance of only 0.29 Pa and a per-unit-resistance conversion efficiency of 97.72 Pa−1. A further predicted optimal combination is validated by simulation, achieving a conversion of 64.96%, confirming the effectiveness of the parameter optimization. Under low-velocity conditions, the flow resistance of this design is only about 0.3–1.3 Pa, allowing passive operation using the natural negative pressure of the extraction pipeline. The design offers modular replaceability of the catalyst insert and operates without external power input beyond the natural negative pressure of the pipeline under the simulated low-velocity conditions, providing a theoretical basis and parameter optimization method for in situ CO catalytic elimination in coal mines.