Hydrogen production through sorption enhanced steam reforming of natural gas: Thermodynamic plant assessment

A detailed and comprehensive simulation model of a H-2 production plant based on the Sorption Enhanced Reforming (SER) process of natural gas has been developed in this work. Besides thermodynamic advantages related to the shift of reforming equilibrium, SER technology features an intrinsic CO2 capture that can be of interest in environmentally constrained economies. The model comprises natural gas treatment, H-2 and CO2 compression, as well as H-2 purification with an adsorption unit that has been integrated within the SER process by using the off-gas for sorbent regeneration. A complete thermal integration has been also performed between the available hot gas streams in the plant, so that high pressure steam is generated and used to generate power in a steam cycle. A comprehensive comparison with conventional H-2 production technologies based on fired tubular reforming (FTR) has been made by defining a proper set of performance indexes. The investigation allowed to set the optimal design parameters and operating conditions of the SER plant and conclude that a better hydrogen production efficiency can be attained when reactors are designed for atmospheric pressure operations rather than pressurized (3 bar) conditions. The SER plant with optimized design parameters (reformer operating temperature at 923 K and a steam-to-carbon ratio in the initial charge around 2) shows considerable improvements on the carbon capture ratio (around 99% for the SER case vs. 85% for the FTR case) and on the natural gas to hydrogen conversion efficiency (by around 15 percentage points) in comparison to the FTR based process featuring CO2 capture. On the whole, a higher natural gas to hydrogen conversion efficiency by 9-15 percentage points, or by 3-6 percentage points when considering credits for steam and electricity import/export, have resulted for the SER plant operating at atmospheric pressure in comparison to the conventional hydrogen production process. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.