• Energy Research

A techno-economic analysis of a natural gas combined cycle integrated with a pre-combustion CO2 capture process based on the Ca-Cu process has been carried out. An extensive calculation of the balances of the entire power plant has been done, including the results obtained from a 1-D pseudo homogeneous model for the fixed bed reactors that compose the Ca-Cu process. Moreover, a methodology developed by the authors is here presented for calculating the cost of the electricity produced and of the CO2 avoided. This methodology has been used to perform the economic analysis of the Ca-Cu based power plant and to optimize the size of the Ca-Cu reactors and the pressure drop in critical heat exchangers. An electricity cost of 82.6 €/MWh has been obtained for the Ca-Cu based power plant, which is 2.2 €/MWh below the benchmark power plant based on an Auto Thermal Reformer with an MDEA absorption process for CO2 capture. The improved performance of the Ca-Cu based power plant in terms of electric efficiency and reduced capital cost expenditure is the reason for the reduced electricity costs. Moreover, a lower cost of CO2 avoided is also obtained for the Ca-Cu plant with respect to the benchmark (80.75 €/tCO2 vs. 85.38 €/tCO2), which features 89% of CO2 capture efficiency.

A combined reactor and particle model was developed with which the effect of mass and heat transfer limitations inside the oxygen carrier particles on the axial concentration and temperature profiles in packed bed CLC could be correctly accounted for. It was concluded that during the oxidation cycle, the relevance of heat transfer limitations is negligible, but that resistances due to internal diffusion may play a significant role. This effect was found to be even stronger with the reduction cycles, where the effectiveness of the oxygen carrier particle was affected by higher activation energies and a low reaction order. With these models, more reliable predictions of the axial concentration and temperature profiles in packed bed CLC can be given, which are necessary to arrive at a proper design and a quantitative assessment of the suitability of packed bed CLC.

From a permeability and selectivity perspective, supported thin-film Pd–Ag membranes are the best candidates for high-purity hydrogen recovery for methane-hydrogen mixtures from the natural gas grid. However, the high hydrogen flux also results in induced bulk-to-membrane mass transfer limitations (concentration polarization) especially when working at low hydrogen concentration and high pressure, which further reduces the hydrogen permeance in the presence of mixtures. Additionally, Pd is a precious metal and its price is lately increasing dramatically. The use of inexpensive CMSM could become a promising alternative. In this manuscript, a detailed comparison between these two membrane technologies, operating under the same working pressure and mixtures, is presented. First, the permeation properties of CMSM and Pd–Ag membranes are compared in terms of permeance and purity, and subsequently, making use of this experimental investigation, an economic evaluation including capital and variable costs has been performed for a separation system to recover 25 kg/day of hydrogen from a methane-hydrogen mixture. To widen the perspective, also a sensitivity analysis by changing the pressure difference, membrane lifetime, membrane support cost and cost of Pd/Ag membrane recovery has been considered. The results show that at high pressure the use of CMSM is to more economic than the Pd-based membranes at the same recovery and similar purity.

In this work, the oxidation reaction of high loaded CuO-based materials was investigated under atmospheric and pressurized conditions. The oxygen transport capacity of the materials was firstly tested in the TGA and no losses greater than 5% were observed along 100 oxidation/reduction cycles. The kinetic parameters governing the oxidation reactions of the selected CuO-based materials were determined using a shrinking core model with chemical reaction control. The experimental results suggested that a SCM with chemical reaction control is able to predict the oxidation conversion of high loaded CuO-based materials in powder and pellet form. On the other hand, the effect of total pressure on materials reactivity was analyzed. The kinetic parameters obtained under atmospheric conditions were applied to fit the experimental data obtained under pressurized conditions. The results confirmed that the pressure has not an important effect on the oxidation kinetics of high loaded CuO-based materials and the parameters obtained at atmospheric pressure can be applied to study the oxidation under pressurized conditions.

Chemical looping combustion is a promising technology for power production with integrated CO2 capture. High overall efficiencies can be reached, if the CLC reactors are operated at elevated pressures and high temperature, which can be accommodated in packed bed reactors. More possible oxygen carriers can be selected if the desired temperature rise for power production is achieved in a two stage chemical looping combustion (TS-CLC) process. In this work, the TS-CLC configuration using copper and manganese based oxygen carriers has been integrated in a complete power plant based on coal gasification (IG-CLC). An extensive energy analysis based on the combined use of a packed bed reactor modeling tool and a complete process simulation has been undertaken. An economic estimation of the reactors capital cost has also been carried out. From the material and energy balances the IG-CLC with one stage nickel-based CLC process results in a net electric efficiency of 41.1% on low heating value basis. In case of TS-CLC, efficiencies of 40.3%–40.8% have been obtained. This demonstrated that IGCC (integrated gasification combined cycles) adopting a TS-CLC process can also achieve high efficiency compared to conventional CO2 capture technologies. Although a larger reactor volume is required for TS-CLC, the total estimated investment costs are a factor two lower, because the oxygen carriers are much cheaper.

Abstract To enable the investigation of the hydrodynamics of gas–solid fluidized bed reactors at high-temperatures and reactive conditions, a new non-invasive experimental technique has been developed, based on the extension of Particle Image Velocimetry (PIV) coupled with Digital Image Analysis (DIA) using dedicated high-temperature endoscopes for image recording and laser illumination. The new endoscopic-laser PIV/DIA technique (ePIV/DIA) allows to determine simultaneously information from the emulsion and bubble phase with high spatial and temporal resolution in a pseudo-2D columns. The ePIV/DIA technique with single-source laser illumination has first been thoroughly validated at cold-flow conditions by comparison with a standard PIV/DIA technique with LED-illumination, showing very good agreement of the results in terms of particle velocity and solids mass flux profiles. The technique has subsequently been applied to fluidized beds in the bubbling fluidization regime at elevated temperatures to demonstrate its unique possibilities to measure detailed bed hydrodynamics at elevated temperatures.

In this paper the influence of the desulfurization method on the process efficiency of an integrated gasification chemical-looping combustion (IGCLC) systems is investigated for both packed beds and circulating fluidized bed CLC systems. Both reactor types have been integrated in an IGCLC power plant, in which three desulfurization methods have been compared: conventional cold gas desulfurization with Selexol (CGD), hot gas desulfurization with ZnO (HGD) and flue gas desulfurization after the CLC reactors (post-CLC). For CLC with packed bed reactors, the efficiency gain of the alternative desulfurization methods is about 0.5-0.7% points. This is relatively small, because of the relatively large amount of steam that has to be mixed with the fuel to avoid carbon deposition on the oxygen carrier. The HGD and post-CLC configurations do not contain a saturator and therefore more steam has to be mixed with a negative influence on the process efficiency. Carbon deposition is not an issue for circulating fluidized bed systems and therefore a somewhat higher efficiency gain of 0.8-1.0% point can be reached for this reactor system, assuming that complete fuel conversion can be reached and no sulfur species are formed on the solid, which is however thermodynamically possible for iron and manganese based oxygen carriers. From this study, it can be concluded that the adaptation of the desulfurization method results in higher process efficiencies, especially for the circulating fluidized bed system, while the number of operating units is reduced.