production of h2 and co from hydrocarbon gases (e.g. natural gas) is performed by two well-known "primary" and "secondary" reformers. steam methane reforming (smr) and autothermal reformer (atr) are two industrial examples of the primary and secondary reformers, respectively. each of which uses only special characteristics. on the other hand, the process of combined reforming utilizes both of primary and secondary tools for production of synthesis gas, as it is commonly practiced in ammonia manufacturing. for the case of methanol, atr is fed with nearly pure oxygen (99.5%) rather than air since the presence of excessive n2 in the syngas would overburden compression and retard the methanol production. the atr reformer consists of a partial oxidation (pox) chamber (usually non-catalytic medium) and a fixed bed catalytic section. the catalytic fixed bed not only adjusts the h2/co ratio, but also destroys any probable soot and precursor (e.g. ethylene and acetylene) that may be formed in the pox chamber. natural gas (ng) is partially oxidized in the combustion chamber by oxygen or air (as an oxidant). steam to carbon (s/c) ratio that is usually 0.6 in the oxygen-based case has been commercialized by haldor-topose company.