Cost Effective CO2 Reduction in the Iron & Steel Industry by Means of the SEWGS Technology: STEPWISE Project

In the STEPWISE project, the Sorption Enhanced Water-Gas Shift (SEWGS) technology for CO2 capture is brought to TRL6 by means of design, construction, operation and modelling a pilot installation in the Iron and Steel industry using Blast Furnace Gas (BFG). This advanced CO2 removal technology makes use of regenerative solid adsorbents. The STEPWISE project represents the essential demonstration step within the research, development and demonstration trajectory of the SEWGS technology. This project will further reduce the risks associated with scaling up the process

High-temperature pressure swing adsorption cycle design for sorption-enhanced water-gas shift

Sorption-enhanced water–gas shift (SEWGS) combines the water–gas shift reaction with in situ adsorption of CO2 on potassium-promoted hydrotalcite (K-HTC) and thereby allows production of hot, high pressure H2 from syngas in a single unit operation. SEWGS is a cyclic process, that comprises high pressure adsorption and rinse, pressure equalisation, and low pressure purge. Here, results are presented of a SEWGS cycle design study, based on recently developed expressions for the interaction of CO2 and H2O with K-HTC. It is shown that during the cycle, steam adsorbs in the rinse step and desorbs during the subsequent reduction in pressure, thereby improving the CO2 purity in the column and thus enhancing the efficiency of the rinse. A parameter study based on numerical simulations shows that the carbon capture ratio depends mainly on the purge steam to carbon feed ratio, whereas the CO2 product purity depends mainly on the rinse steam to carbon feed ratio. An optimisation yields a SEWGS cycle that consumes significantly less steam than cycle designs previously reported in the literature

High-temperature pressure swing adsorption cycle design for sorption-enhanced water-gas shift

Sorption-enhanced water–gas shift (SEWGS) combines the water–gas shift reaction with in situ adsorption of CO2 on potassium-promoted hydrotalcite (K-HTC) and thereby allows production of hot, high pressure H2 from syngas in a single unit operation. SEWGS is a cyclic process, that comprises high pressure adsorption and rinse, pressure equalisation, and low pressure purge. Here, results are presented of a SEWGS cycle design study, based on recently developed expressions for the interaction of CO2 and H2O with K-HTC. It is shown that during the cycle, steam adsorbs in the rinse step and desorbs during the subsequent reduction in pressure, thereby improving the CO2 purity in the column and thus enhancing the efficiency of the rinse. A parameter study based on numerical simulations shows that the carbon capture ratio depends mainly on the purge steam to carbon feed ratio, whereas the CO2 product purity depends mainly on the rinse steam to carbon feed ratio. An optimisation yields a SEWGS cycle that consumes significantly less steam than cycle designs previously reported in the literature

A novel reactor configuration for packed bed chemical-looping combustion of syngas

This study reports on the application of chemical looping combustion (CLC) in pressurized packed bed reactors using syngas as a fuel. High pressure operation of CLC in packed bed has a different set of challenges in terms of material properties, cycle and reactor design compared to fluidized bed operation. However, high pressure operation allows the use of inherently more efficient power cycles than low pressure fluidized bed solutions. This paper quantifies the challenges in high pressure operation and introduces a novel reactor concept with which those challenges can be addressed. Continuous cyclic operation of a packed bed CLC system is simulated in a 1D numerical reactor model. Importantly, it is demonstrated that the temperature profiles that can occur in a packed bed reactor as a result of the different process steps do not accumulate, and have a negligible effect on the overall performance of the system. Moreover, it has been shown that an even higher energy efficiency can be achieved by feeding the syngas from the opposite direction during the reduction step (i.e. countercurrent operation). Unfortunately, in this configuration mode, more severe temperature fluctuations occur in the reactor exhaust, which is disadvantageous for the operation of a downstream gas turbine. Finally, a novel reactor configuration is introduced in which the desired temperature rise for obtained hot pressured air suitable for a gas turbine is obtained by carrying out the process with two packed bed reactor in series (two-stage CLC). This is shown to be a good alternative to the single bed configuration, and has the added advantage of decreasing the demands on both the oxygen carrier and the reactor materials and design specification

CLC in packed beds using syngas and CuO/Al2O3: model description and experimental validation

The objective of this work is to study the performance of the oxygen carrier in a packed bed with periodic switching between oxidizing and reducing conditions. In this paper the performance of CuO/Al2O3 as the oxygen carrier in a packed bed reactor with syngas as the fuel are investigated, while also studying the (possible) carbon deposition and the effect of sulphur impurities on the stability of the carrier. Both experiments and simulations are used in this work. Cyclic experiments (oxidation with air and reduction with syngas) have been carried out in a lab scale packed bed reactor with 13wt% CuO/Al2O3. The experimental results were well described by a 1D reactor model, provided that critical attention was given to the reaction rate for the complete reduction reaction, including a dramatic decrease in reaction rate at high solid conversions. Feeding syngas (pH2=pCO=0.1bar) resulted in 1.1% carbon deposition of the feed. Steam was proven to be more effective in reducing carbon deposition than CO2. Moreover, it has been found that CuO/Al2O3 catalyzed the water gas shift reaction and the reaction rate was not permanently affected by exposure to H2S, two key factors for CLC operation. The results of this work imply that CuO/Al2O3 is an effective oxygen carrier as the first packed bed reactor in a TSCLC process and that the developed model is able to describe the performance at larger scales accurately. © 2014 Elsevier Ltd

Reactivity of oxygen carriers for chemical looping combustion in packed bed reactors under pressurized conditions

For the design, scale-up, and optimization of pressurized packed bed reactors for chemical-looping combustion (CLC), understanding of the effect of the pressure on the reactivity of the oxygen carriers is very important. In this work, the redox reactivity of CuO/Al2O3 and NiO/CaAl2O4 particles at elevated pressures have been measured in a pressurized high-temperature magnetic suspension balance. The experiments have demonstrated that the pressure has a negative influence on the reactivity and that this effect is kinetically controlled. The negative effect of the pressure might be caused by the decrease in the number of oxygen vacancies at higher pressures. Moreover, the reactant gas fraction has been demonstrated as an important parameter, probably related to competition between different species for adsorption on the oxygen carrier surface. These effects have been included in the kinetic model leading to a good description of the experimental results. The impact of these findings on packed bed CLC applications with larger oxygen carrier particles has been investigated with a particle model that considers diffusion limitations and kinetics. It has been shown that the impact of diffusion limitations decreases with increasing pressure, due to the decrease in reaction rates and the increase in diffusion fluxes caused by Knudsen diffusion. The results have been validated by experiments with 1.7 mm NiO/CaAl2O4 particles. These results corroborate that the selection of larger particles because of pressure drop considerations does not lead to a large decrease in effective reaction rates, which is beneficial for packed bed CLC applications

Operation of fixed-bed chemical looping combustion

Chemical Looping Combustion is an alternative technology for CO2 capture. While most systems utilize dual circulating fluidized-beds, this work shows that fixed-bed Chemical Looping Combustion is a feasible configuration for this technology. The inherent separation of the CO2 from the depleted air stream gives a very low efficiency penalty, which is further improved by the possibility of using a pressurized fixed-bed system, a factor much more difficult to realize with circulating fluidized beds. A laboratory scale experimental system has been constructed for the purpose of validating a numerical model. The results from the numerical model have agreed well with experimental data over full oxidation-reduction cycles and will be presented in subsequent publications. The work briefly described here, and to be presented in detail in coming publications, forms a basis which proves feasibility, but also opens up several possibilities for further investigations needed to scale-up and eventually commercialize CLC for power generation with inherent CO2 capture

CLC in packed beds using syngas and CuO/Al2O3 : a model description and experimental validation

The objective of this work is to study the performance of the oxygen carrier in a packed bed with periodic switching between oxidizing and reducing conditions. In this paper the performance of CuO/Al2O3 as the oxygen carrier in a packed bed reactor with syngas as the fuel are investigated, while also studying the (possible) carbon deposition and the effect of sulphur impurities on the stability of the carrier. Both experiments and simulations are used in this work. Cyclic experiments (oxidation with air and reduction with syngas) have been carried out in a lab scale packed bed reactor with 13 wt% CuO/Al2O3. The experimental results were well described by a 1D reactor model, provided that critical attention was given to the reaction rate for the complete reduction reaction, including a dramatic decrease in reaction rate at high solid conversions. Feeding syngas (pH2 = pCO = 0.1 bar) resulted in 1.1% carbon deposition of the feed. Steam was proven to be more effective in reducing carbon deposition than CO2. Moreover, it has been found that CuO/Al2O3 catalyzed the water gas shift reaction and the reaction rate was not permanently affected by exposure to H2S, two key factors for CLC operation. The results of this work imply that CuO/Al2O3 is an effective oxygen carrier as the first packed bed reactor in a TSCLC process and that the developed model is able to describe the performance at larger scales accurately