Application of Reverse Flow Reactor for Vent Gas Emission Reduction in Catalytic Oxidation Unit at Purified Terephthalic Acid Plant

Abstract

PTA (Purified Terephthalic Acid) manufacturing process generates waste gases containing VOC (Volatile Organic Compounds) that have negative health effects, one of it is benzene. Catalytic oxidation method consists of a recuperative (need external energy to reach the reaction temperature) and reverse flow reactor (RFR) which uses the principles of auto thermal (requires no external energy). Fuel consumption for heating the feed gas is a major operating cost in the catalytic oxidation, so that the fuel reduction becomes important. The objective of this study is to assess the technical possibility of RFR to lower the fuel consumption; and to assess the operating conditions for autothermal conditions. The mathematical model consisted of the unsteady state mass and energy balances and was numerically solved using a software package of FlexPDE verion 6.32. The recuperative system was simulated in the steady state condition, while RFR with the same amount of catalyst was simulated in the unsteady state condition. As the key parameter, the switching time was varied to consider the performance of RFR. At various switching times and inlet concentrations, the autothermal was achievable even heat extraction was required to prevent the catalyst overheat. At the feed gas linear velocity of 1.2 m/s and the switching time of 7.5 s or higher, RFR provides energy saving that is equivalent to US$ 0.1208/ton feed gas up to US$ 0.7248/ton of feed gas compared to recuperative system.