The apparatus of low-concentration coal mine methane (LCM) combustion, from experimental scale to industrial scale, is necessary for the large volume of LCM. In this paper, an experimental system has been set up for the LCM combustion to validate the corresponding numerical model. Following this, the revised burner, with increased inlet diameter and burner length, was used to study the combustion characteristics numerically based on the reliable model. Results indicated that the temperature distribution exhibits a one-dimensional nature evidently and the temperature discrepancy among different inlet diameters is negligible with the adiabatic wall. However, the temperature discrepancy is apparent when the heat loss of the wall is considered, which shows the importance of heat preservation outside the burner wall. As the burner diameter increases, the total temperature increases and appears to be more homogeneous with the heat loss wall. In addition, NO emissions decrease gradually and CO emissions increase rapidly with the increasing of the diameter. When the inlet diameter triples, the NO emissions decrease by 31.4% and the CO emissions increase by a factor of 11. With the increasing of the burner length, the temperature, NO emissions, and CO emissions at the burner outlet decrease when the heat loss of the wall was not ignored. In addition, the NO emissions and CO emissions decrease by 18.6% and 22.7-fold, respectively, when the length triples. The velocity limit of different equivalence ratios, together with the temperature distribution and pollutant emission at different scales, should be considered systematically when the large-scale burners are designed.