Process Integration of an Autothermal Reforming Hydrogen Production System with Cryogenic Air Separation and Carbon Dioxide Capture Using Liquefied Natural Gas Cold Energy

The autothermal reforming (ATR) process for hydrogen production saves considerable energy for the reaction compared with endothermic steam methane reforming (SMR). However, it requires a supply of pure oxygen, for which an air separation unit (ASU) is needed; this hinders the adoption of ATR in industrial applications because of both the high capital and operating costs. At the same time, in liquefied natural gas (LNG) regasification terminals, the cold energy from the regasification process is typically wasted. Coincidentally, the temperature of this waste cold energy matches that required for ASU operation. Thus, in this paper, a novel ATRprocess is proposed in which an ASU and LNG regasification are integrated in order to make use of the cold energy as an operating utility and achieve hydrogen production from the LNG. For the sake of comparison, the proposed system and a conventional SMR process are optimized using a genetic algorithm to evaluate and benchmark its performance. With an LNG feed stream of 827.5 kmol/h, the optimal case of the proposed system produces 2508.0 kmol/h hydrogen gas with a purity of 99.2%; the exergy destruction is reduced by 18.6% and its overall exergy efficiency is approximately 25.4% higher than that of the SMR process. Also, an economic evaluation is performed using the net present value (NPV) as an indicator. The NPV of the proposed system is 338.9 million USD, which is 72.6% higher than that of hydrogen production with the SMR process from LNG.