This article critically reviews the literature on iron-based catalysts for the high-temperature water–gas shift (HT-WGS) reaction. The reaction mechanism, reaction intermediates, rate-determining step, kinetics, active site, and promoters are covered. Unlike the low-temperature water–gas shift (LT-WGS) reaction by Cu/ZnO catalysts that has received intensive analysis with modern in situ and operando spectroscopy and DFT studies, the corresponding HT-WGS reaction by Fe-based catalysts still lacks a fundamental understanding because of the absence of modern catalysis studies of this important catalytic system. Given the role of the WGS catalysts on production of H2 for a hydrogen economy, it is imperative that the fundamental molecular-level understanding of the HT-WGS catalyst be advanced.

Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review

Water gas shift reaction for hydrogen production and carbon dioxide capture: A review

Adsorption equilibria and kinetics of six pure gases on pelletized zeolite 13X up to 1.0 MPa: CO2, CO, N2, CH4, Ar and H2

An evaluation of hydrogen production from the perspective of using blast furnace gas and coke oven gas as feedstocks

The steel industry is the main generator of CO2 among the different industrial sectors. That is why efforts are being made to reduce or avoid CO2 emissions by process optimisation or by Carbon Capture and Storage (CCS) processes. In the steel production by blast furnace technology, three main off-gases are generated, namely the Blast Furnace Gas (BFG), the Coke-Oven Gas (COG) and the Basic Oxygen Furnace Gas (BOFG). Many processes and technologies can be identified for their use, depending on the volume and composition of the steelwork off-gases. In the present work, a review and an analysis of several alternatives proposed during last years to use these off-gases are carried out, with a particular focus on thermochemical processes. Three main alternatives are considered: the thermal use of the gases, the recovery of valuable compounds for selling and the synthesis of a high-added value product. The possible implementation of these alternatives may conduct to improvements in energy efficiency of the steel making process with subsequent reduction of CO2 emissions.

A review of thermochemical processes and technologies to use steelworks off-gases

The world’s progression towards the Hydrogen economy is facilitating the production of hydrogen from various resources. In the carbon based hydrogen production, Water gas shift reaction is the intermediate step used for hydrogen enrichment and CO reduction in the synthesis gas. This paper makes a critical review of the developments in the modeling approaches of the reaction for use in designing and simulating the water gas shift reactor. Considering the fact that the rate of the reaction is dependent on various parameters including the composition of the catalyst, the active surface and structure of the catalyst, the size of the catalyst, age of the catalyst, its operating temperature and pressure and the composition of the gases, it is difficult to narrow down the expression for the shift reaction. With different authors conducting experiments still to validate the kinetic expressions for the shift reaction, continuous research on different composition and new catalysts are also reported periodically. Moreover the commercial catalyst manufacturers seldom provide information on the catalyst. This makes the task of designers difficult to model the shift reaction. This review provides a consolidated listing of the various important kinetic expressions published for both the high temperature and the low temperature water gas shift reaction along with the details of the catalysts and the operating conditions at which they have been validated.

A Review of the Water Gas Shift Reaction Kinetics

Average solid holdup in the axial direction was investigated in a liquid solid circulating fluidized bed riser (LSCFB), with liquids of different viscosities. The effect of operating parameters including; primary, secondary and total velocity, particle diameter and density was studied. Experiments were conducted using water and glycerol at different concentration having viscosities in the range 1–1.36 cp. The results indicated that the solid holdup in the riser was axially uniform for viscous liquids and increases with increase in auxiliary velocity. The average solid holdup decreases with increase in total velocity and increases with increase in viscosity for sand–glycerol, glass bead–glycerol system. The experimental measurements were compared with the existing holdup model prediction that varied linearly with viscosity. Further, a correlation was developed to estimate average solid holdup in the riser, and the performance of the expression was compared with the present experimental data.

Solid holdup in liquid solid circulating fluidized bed with viscous liquid medium

Viscosity Effects on Solid Circulation Rate in a Liquid Solid Circulating Fluidized Bed

Experiments were conducted in a liquid-solid circulating fluidized bed with different viscous liquids and particles to study the hydrodynamics, average solid hold up and solid circulation rate. The effects of operating parameters, i.e., primary liquid flow rate in the riser, auxiliary liquid flow rate, total liquid flow rate and viscosity of the liquid were studied for solids of different density and particle size. Results show that the circulating fluidization regime starts earlier for more viscous solutions because of the decrease in critical transitional velocity. The onset of solid holdup increases with an increase in liquid viscosity for sand and for glass beads. The solid circulation rate increases with an increase in total velocity and auxiliary velocity, and also increases with increasing viscosity.

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Solid holdup and circulation rate in a liquid-solid circulating fluidized bed with viscous liquid medium

Membrane reactor is a process intensified equipment that carries out both the reaction and separation in a single vessel. The equilibrium limited water gas shift reaction is an ideal reaction to be carried out in a membrane reactor as it improves the conversion of the reaction and reduces the space requirement for the reactor. Computational fluid dynamics offers a virtual prototyping of the reactor and helps in design, optimization, and scale-up of the reactor. To obtain pure hydrogen from the membrane reactor, the pressure of the reactor needs to be optimized. Hence the water gas shift membrane reactor is subjected to computational fluid dynamic analysis to understand the role played by pressure on the performance of the reactor using three different gas mixtures. The CO conversion and H2 recovery for the different operating pressures are simulated and the effects of pressure are discussed in this paper.

Muruganandam Loganathan

Papers

A Review of the Water Gas Shift Reaction Kinetics

Solid holdup in liquid solid circulating fluidized bed with viscous liquid medium

Viscosity Effects on Solid Circulation Rate in a Liquid Solid Circulating Fluidized Bed

Solid holdup and circulation rate in a liquid-solid circulating fluidized bed with viscous liquid medium

CFD Simulation of Water Gas Shift Membrane Reactor--Pressure Effects on the Performance of the Reactor