Fluid-dynamic study on a multi-stage fluidized bed column for continuous CO2 capture via temperature swing adsorption

Adsorption based processes have a great potential to significantly reduce the overall costs of CO2 separation from stack flue gas as compared to currently available technologies. One of the main challenges in the development of these processes is certainly the provision of adequate adsorbents. Hence, in the last decade a great effort has been put into screening and testing of various adsorbent materials. However, beside the identification of suitable adsorbent materials it is of equal importance to develop suitable reactor designs that allow for effective and most cost efficient utilization of these materials and so far only little work has been attributed to this subject. Nevertheless, it was shown that for thermodynamic reasons it is essential to provide counter-current contact between adsorbent and gas streams in order to allow for efficient operation of any Temperature Swing Adsorption (TSA) CO2 capture process. It was further highlighted that effective heat transfer with the used adsorbent material is necessary as the reported values of their corresponding adsorption enthalpies are typically rather large. Please click Additional Files below to see the full abstract

A multi-stage fluidized bed system for Continuous CO2 capture by means of temperature swing adsorption – First results from bench scale experiments

Temperature swing adsorption processes have been proposed as an alternative to common amine scrubbing processes for CO2 capture from stack flue-gas streams, as they have the potential to reduce the overall capture costs significantly. In the recent years, researchers have put a great effort into the development of highly selective CO2 adsorbent materials with sufficiently large CO2 transport capacities and cyclic operating stability. However, comparably little work has been attributed to the development of suitable reactor designs or to the experimental study of continuously operated temperature swing adsorption (TSA) processes that utilizes those adsorbent materials. The authors of this work most recently introduced a reactor system that allows for effective and efficient operation of the TSA process. The system comprises two interconnected multi-stage fluidized bed columns that enable counter-current contact of adsorbent and gas streams in both columns whilst allowing for effective heat management through indirect heat exchange in each stage. Based on the proposed reactor design, a fully integrated bench scale unit (BSU) has been constructed and put into operation to deliver a proof of concept and to further study the process experimentally (see Figure 6). Each of the BSU columns comprises five fluidized bed stages that are operated in the bubbling bed regime. Transport of solids between the two columns is carried out in two transport loops consisting of a screw conveyor, a riser and a gravitational gas/solids separator each. An amine-functionalized solid sorbent selectively adsorbs CO2 in the adsorber at low temperature and is subsequently regenerated in the desorber column at higher operating temperature, before it is returned to the adsorber. This work presents results obtained from the first continuous CO2 capture experiment within the unit. Please click Additional Files below to see the full abstract

Impacts of soil conditions and light availability on natural regeneration of Norway spruce Picea abies (L.) H. Karst. in low-elevation mountain forests

& Key message Natural regeneration of P. abies (L.) H. Karst. may reach high densities in lower mountain elevations. The highest densities were found in sites with moderate light availability, with low pH, and not near the riverbank. However, age-height classes differed in the predicted magnitude of response, but were consistent in response directions. Mosses and understory species typical of coniferous forests were positively correlated with regeneration density. & Context Norway spruce Picea abies (L.) H. Karst. in Central Europe is at risk under climate change scenarios, particularly in mountain regions. Little is known about the impact of environmental factors on the natural regeneration of P. abies in lowelevation mountain forests. & Aims We aimed to assess impacts of distance from the riverbank, soil pH, and light availability on natural P. abies regeneration. We hypothesized that (1) natural P. abiesregeneration would depend on light availability and soil pH and (2) there are understory plant species which may indicate the microsites suitable for natural regeneration of P. abies. & Methods The study was conducted in the Stołowe Mountains National Park (SW Poland, 600–800 m a.s.l.). We established 160 study plots (25 m2 ) for natural regeneration, light availability, soil pH, and understory vegetation assessment

Chemical Looping Pilot Plant Results Using a Nickel-Based Oxygen Carrier

A chemical looping pilot plant was designed, built and operated with a design fuel power of 120 kW (lower heating value, natural gas). The system consists of two Circulating Fluidized Bed (CFB) reactors. Operating results are presented and evaluated for a highly reactive nickel-based oxygen carrier, total system inventory 65 kg. The performance in fuel conversion achieved is in the range of 99.8% (CH4 conversion) and 92% (CO2 yield). In chemical looping reforming operation, it can be reported that thermodynamic equilibrium is reached in the fuel reactor and that all oxygen is absorbed in the air reactor as soon as the global stoichiometric air/fuel ratio is below 1 and the air reactor temperature is 900°C or more. Even though pure natural gas (98.6 vol.% CH4) without steam addition was fed to the fuel reactor, no carbon formation has been found as long as the global stoichiometric air/fuel ratio was larger than 0.4. Based on the experimental findings and on the general state of the art, it is concluded that niche applications such as industrial steam generation from natural gas or CO2-ready coupled production of H2 and N2 can be interesting pathways for immediate scale-up of the technology