chemical engineering research and design 88 (2010) 1342–1350 Contents lists available at ScienceDirect Chemical Engineering Research and Design journal homepage: www.elsevier.com/locate/cherd Arrangement of primary and secondary reformers for synthesis gas production Hadi Ebrahimi a,* , Alireza Behroozsarand a,b , Akbar Zamaniyan a a Department of Natural Gas Conversion, Gas Research Division, Research Institute of Petroleum Industry (RIPI), Olyempic Bolevar, Azadi Sport Complex, Tehran 14665-1998, Iran b Department of Chemical Engineering, Sahand University of Technology, Tabriz 651335-1996, Iran abstract In order to produce synthesis gas (syngas), four reforming processes including two stand-alone primary and sec- ondary reformers and two combined configurations are investigated. With changing operating parameters and arrangement of the reformers (i.e. stand-alone, parallel, and series), the syngas may be obtained for different appli- cations such as methanol, Fischer-Tropsch (FT), and ammonia synthesis. After study of several arrangements, the selected cases are simulated. Due to the shift some reforming duty from the primary reformer to the secondary one, the primary size and the total fired duty are reduced. The Non-Sorting Genetic Algorithm II (NSGA-II) optimization method is applied for the problem based on the practical point of view. It is shown that the parallel case is preferable in accordance to the high productivity object. For an optimum point, parallel case has 58% of productivity of syngas more than that of series one. However, the series configuration consumes lower fuel (361.1kmolh -1 , in comparison to the parallel case with 437.19) and releases lower amount of CO 2 emission. It is shown that the series arrangement has an average of 13.22% of released CO 2 molar flow less than that of parallel arrangement. Crown Copyright © 2010 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. Keywords: Primary reformer; Secondary reformer; Syngas; Process simulation; Optimization 1. Introduction Both diesel and methanol, two gas-to-liquid (GTL) products, need synthesis gas (syngas), a combination of hydrogen and carbon monoxide with different ratios of H 2 /CO (near 1 for GTL-iron). In fact a considerable amount of total investment of a GTL plant is accounted for syngas generation (Wilhelm et al., 2001). Demand for cleaner fuels drives the increasing of global interest in the GTL process for producing diesel with very low sulfur content and methanol synthesis. The diesel fuel as a product of GTL processes has a higher octane number in com- parison to conventional diesels. This gives better performance and low aromatic and sulfur contents. Moreover, the new proposed optimized GTL processes based on the syngas feed can reduce the CO 2 emission to the environment by recycling the CO 2 , studied by some authors (Basini, 2005; Iijima et al., 2004; Sheppard and Yakobson, 2003; O’Rear and Brancaccio, 2005; Minta et al., 2008). ∗ Corresponding author. Tel.: +98 21 447395x2398; fax: +98 21 44739716. E-mail addresses: ebrahimih@ripi.ir, hadi.ebrahimi@kit.edu (H. Ebrahimi). Received 24 October 2009; Received in revised form 14 February 2010; Accepted 24 February 2010 Production of H 2 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 N 2 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 cat- alytic section. The catalytic fixed bed not only adjusts the H 2 /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 combus- tion chamber by oxygen or air (as an oxidant). Steam to carbon 0263-8762/$ – see front matter Crown Copyright © 2010 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. doi:10.1016/j.cherd.2010.02.021