Novel approach for low CO₂ intensity hydrogen production from natural gas

Abstract

Hydrogen from natural gas with CO2 capture can be a key transition technology to a low carbon energy system due to the abundance of natural gas and the possibility to...

CO2 Capture and Enhanced Hydrogen Production Enabled by Low-Temperature Separation of PSA Tail Gas: A Detailed Exergy Analysis

“…Reforming processes for natural gas generate syngas with CO 2 content typically in the range of 15-25 mol% after the water-gas shift reactions [21]. This range is considerably below what is viable for the partial condensation and separation of liquefied CO 2 , but the use of hydrogen-selective separation processes such as pressure-swing adsorption or hydrogen-selective membranes can produce tail gas or retentate gas with highly favourable conditions, with respect to CO 2 fraction [4,[31][32][33].…”

“…The tail gas separation cycle in consideration is part of a hydrogen production process with integrated CO 2 capture and a capacity of 500 tons of hydrogen per day, as previously documented in [4]. A process flow diagram is given in Figure 7.…”

“…A pre-reformer first converts higher hydrocarbons in the natural gas feed to methane, before the feed is further heated and mixed with a fraction of the CO 2 -depleted tail gas recycled from the gas separation section, and then sent to the main reformer. The tail gas recycling to the ATR reactor represents a difference from the process documented in [4], where tail gas is recycled only to the water-gas shift section. After cooling in a steam generation section, the syngas passes through a high-and low-temperature water-gas shift reactor (HT-WGS and LT-WGS, respectively) to increase the carbon monoxide to CO 2 conversion, and correspondingly, the hydrogen production.…”

“…Chemical solvents, despite being a mature technology, are arguably inefficient energy-wise and can even have negative exergy efficiency in pre-combustion applications [3]. To better exploit the high CO2 concentrations that reforming processes can provide, an innovative solution was proposed by Straus et al [4], in which a PSA unit is combined with a low-temperature tail gas separation process for CO2 capture and recirculation of CO, methane, and hydrogen to the upstream water-gas shift reactors and reformer. This solution can achieve a very high global CO2 capture ratio and simultaneously very high plant efficiency [4].…”

“…To better exploit the high CO2 concentrations that reforming processes can provide, an innovative solution was proposed by Straus et al [4], in which a PSA unit is combined with a low-temperature tail gas separation process for CO2 capture and recirculation of CO, methane, and hydrogen to the upstream water-gas shift reactors and reformer. This solution can achieve a very high global CO2 capture ratio and simultaneously very high plant efficiency [4]. The high efficiency can partly be explained by a reduction in the parasitic energy requirement for separating the syngas into hydrogen and CO2.…”