Improving the gas-solids contact efficiency in a fluidized bed of CO2 adsorbent fine particles

A modified CO(2) adsorbent is obtained by dry mixing of a Ca(OH)(2) fine powder as received with a commercial silica nanopowder. Silica nanoparticles form light agglomerates of size of the order of tens of microns, which are uniformly fluidizable. These agglomerates act as dispersants of the Ca(OH)(2) fine particles, which coat the nanoparticle agglomerates likely due to contact charging. Ca(OH)(2) particles (CO(2) adsorbent) are thus provided with a vehicle for uniform fluidization. In this way, the contact efficiency between the CO(2) adsorbent and CO(2) in the fluidized bed is greatly enhanced. Experimental results show that the improvement of Ca(OH)(2) fluidizability serves to enhance the carbonation reaction in the fluidized bed.     

The memory of granular materials

Granular materials exhibit a complex variety of fluid and solid collective regimes which has led researchers to consider them as a new state of matter all on its own. In this paper we investigate the behaviour of granular materials by means of Hurst rescaled range analysis. We analyse records in time of the angle of the slope of granular materials partially filling a rotating drum and records of the local backscattered light from fluidized beds. We show that the Hurst analysis is able to identify phase transitions as well as to characterize spatio-temporal structures. The influence of interparticle attractive interactions on the memory of granular materials is also investigated.     

Use of silica nanopowder to accelerate CO2 sorption by Ca(OH)2

Promising technologies have recently emerged to capture CO₂ from postcombustion flue gas and to enhance the production of hydrogen from natural gas by steam-methane reforming, on the basis of sorption of CO₂ by Ca-based powders. The rate of CO₂ sorption on Ca-based powders is limited by both carbonation kinetics and transport of CO₂ to unreacted sorption sites. Ca-based powders may exhibit cohesive aggregation, thus hindering gas–solids contact efficiency. In our work, we tested the sorption rate of powder samples prepared by dry mixing of a cohesive Ca(OH)₂ powder with a silica nanopowder used as additive. The silica nanopowder serves to improve the dispersibility of Ca(OH)₂. Consequently, when a CO₂ enriched gas and the modified sorbent are brought into contact, the rate of CO₂ sorption is enhanced in the initial fast phase of interest for practical applications.     

A Selective Chromogenic Probe for Mercury(II) and Cyanide in Aqueous Buffered Solution from a Cycloaddition Reaction of an Ynamine to Polycyclic Dithiolethiones

The synthesis of some new polysulfur‐nitrogen heterocycles by cycloaddition of an ynamine to bisdithiolothiazine ketothiones or dithiones is described and the interconversion between regioisomers is studied by DFT calculations, showing that the double bond isomerizes at room temperature. This series is a new selective and sensitive chromogenic probe for the naked‐eye detection of mercury(II) cation and cyanide anion in buffered (HEPES 0.05 M , pH 7.14) water/acetonitrile 1:1 mixture, with sub‐micromolar sensitivity, and constitutes the first example of a new class of colorimetric chemical probes for Hg²⁺ and CN^?.     

Statistical Properties of a System Consisting of a Superconducting Qubit Coupled to an Optical Field Inside a Transmission Line

The present work investigates the entropy and the excitation inversion of a coupled system that consists of a qubit represented by a Cooper pair box(CPB) interacting with a transmission line working as a circuit quantum electrodynamics(CQED). The proposed scheme uses the Buck-Sukumar model with a time dependent frequency in the presence of losses to study the evolution of the entropy and the excitation inversion of the system. We have shown that the CQED is much more sensitive to the presence of losses than the CPB. The results also show that it is possible to monitor properties of the subsystems through appropriate choices of the time-dependent parameters.     

Generalized transformation for decorated spin models

The paper discusses the transformation of decorated Ising models into an effective undecorated spin model, using the most general Hamiltonian for interacting Ising models including a long range and high order interactions. The inverse of a Vandermonde matrix with equidistant nodes [−s,s] is used to obtain an analytical expression of the transformation. This kind of transformation is very useful to obtain the partition function of decorated systems. The method presented by Fisher is also extended, in order to obtain the correlation functions of the decorated Ising models transforming into an effective undecorated Ising model. We apply this transformation to a particular mixed spin-(1/2, 1) and (1/2, 2) square lattice with only nearest site interaction. This model could be transformed into an effective uniform spin-S square lattice with nearest and next-nearest interaction, furthermore the effective Hamiltonian also includes combinations of three-body and four-body interactions; in particular we considered spin 1 and 2.