Numerical investigation of methane combustion in a pipe with turbulent flow is studied. The space discretization error is investigated quantitatively and qualitatively, using the Richardson extrapolation and profiles comparisons. Comparison of the profiles indicates that the solution converges to a grid-independent solution. The Richardson method gives unsatisfactory results to determine the grid error, because of the rigidity of the method. A second-order polynomial is used as an alternative to the Richardson method. The results are more stable and have a better goodness of fit. The results of the simulations are compared with those of a similar experiment and the corresponding analytical solution.