Key intermediates of the chemical value chain such as hydrogen cyanide and synthesis gas are produced in high temperature tube bundle reactors. Process intensification plays an essential role toward a more sustainable production of these compounds. In this contribution the tube bundle arrangement is optimized for the case study of hydrogen cyanide production. Using physics-based model reduction, the bundle reactor is modeled in two dimensions. Gas layer emissivity and tube total view factors are identified as crucial parameters for radiative heat transfer in the furnace. Using an equidistant spacing of 0.052 m, the average yield of HCN is improved by 0.5% and the variance of tube yields is reduced. Overall, staggered arrangements are superior to aligned bundle arrangements. Based on these findings, rule-of-thumb-type tube bundle design heuristics can be derived for any specific furnace design having a potentially large impact on the economic and ecologic footprint of these processes. (C) 2019 Elsevier Ltd. All rights reserved.