Numerical Simulation of Liquid Injection into an Anisothermal Dense Fluidized Bed

Fluidized beds are widely used in reactive industrial processes such as: olefins production, oil cracking or uranium fluorination because of their high efficiency mixing properties. In such processes, the chemical reaction is strongly dependent on the temperature and liquid is injected into the reactor in order to cool it. The experimental data of the time evolution of the gas temperature in an anisothermal dense fluidized bed with a liquid injection provided by INEOS is first compared with the results predicted by a simple model with an assumption of a perfectly mixed fluidized bed (uniform solid and temperature distribution in the bed). The results of this simple model show that the time evolution of the gas temperature is accurately predicted. Additionally, we point out that the wall-to-bed heat transfer plays a crucial role of the gas temperature in the bed. Then, we performed 3-D numerical simulations that let us investigate local interactions between phases and heat transfer with wall. The simulations show that the liquid evaporates quickly and the temperature is in a satisfactory agreement with the experiment data

3D Numerical Simulation of Catalyst Injection into a Dense Fluidized Bed

In this study, the injection of catalyst particles into a dense gas-solid fluidized bed reactor is investigated using the Euler/Euler approach. Numerical simulations of horizontal catalyst+gas mixture injection through a circular-sectioned nozzle have been performed in order to study the effect of the operating conditions of an injector on the flow hydrodynamics. The study is in the context of a larger project to optimize the nozzle geometry. The nozzle is composed of two annular sections, one outer and one inner. Catalyst is injected from the central section of the nozzle with a transport gas called here “gas 1”. Another gas is injected in the outer section: “gas 2”. The results show that the good dispersion of the catalyst depends highly on the ratio of the velocities in the outer and the inner sections of the nozzle

3D Numerical Simulation of Catalyst Injection into a Dense Fluidized Bed

International audienceIn this study, the injection of catalyst particles into a dense gas-solid fluidized bed reactor is investigated using the Euler/Euler approach. Numerical simulations of horizontal catalyst+gas mixture injection through a circular-sectioned nozzle have been performed in order to study the effect of the operating conditions of an injector on the flow hydrodynamics. The study is in the context of a larger project to optimize the nozzle geometry. The nozzle is composed of two annular sections, one outer and one inner. Catalyst is injected from the central section of the nozzle with a transport gas called here "gas 1". Another gas is injected in the outer section: "gas 2". The results show that the good dispersion of the catalyst depends highly on the ratio of the velocities in the outer and the inner sections of the nozzle

MLVA polymorphism of Salmonella enterica subspecies isolated from humans, animals, and food in Cambodia

<p>Abstract</p> <p>Background</p> <p><it>Salmonella </it>(<it>S</it>.) <it>enterica </it>is the main cause of salmonellosis in humans and animals. The epidemiology of this infection involves large geographical distances, and strains related to an episode of salmonellosis therefore need to be reliably discriminated. Due to the limitations of serotyping, molecular genotyping methods have been developed, including multiple loci variable number of tandem repeats (VNTR) analysis (MLVA). In our study, 11 variable number tandem-repeats markers were selected from the <it>S. enterica </it>Typhimurium LT2 genome to evaluate the genetic diversity of 206 <it>S. enterica </it>strains collected in Cambodia between 2001 and 2007.</p> <p>Findings</p> <p>Thirty one serovars were identified from three sources: humans, animals and food. The markers were able to discriminate all strains from 2 to 17 alleles. Using the genotype phylogeny repartition, MLVA distinguished 107 genotypes clustered into two main groups: <it>S. enterica </it>Typhi and other serovars. Four serovars (Derby, Schwarzengrund, Stanley, and Weltevreden) were dispersed in 2 to 5 phylogenic branches. Allelic variations within <it>S. enterica </it>serovars was represented using the minimum spanning tree. For several genotypes, we identified clonal complexes within the serovars. This finding supports the notion of endemo-epidemic diffusion within animals, food, or humans. Furthermore, a clonal transmission from one source to another was reported. Four markers (STTR3, STTR5, STTR8, and Sal20) presented a high diversity index (DI > 0.80).</p> <p>Conclusions</p> <p>In summary, MLVA can be used in the typing and genetic profiling of a large diversity of <it>S. enterica </it>serovars, as well as determining the epidemiological relationships of the strains with the geography of the area.</p

Nipah Virus in Lyle's Flying Foxes, Cambodia

We conducted a survey in Cambodia in 2000 on henipavirus infection among several bat species, including flying foxes, and persons exposed to these animals. Among 1,072 bat serum samples tested by enzyme-linked immunosorbent assay, antibodies reactive to Nipah virus (NiV) antigen were detected only in Pteropus lylei species; Cynopterus sphinx, Hipposideros larvatus, Scotophilus kuhlii, Chaerephon plicata, Taphozous melanopogon, and T. theobaldi species were negative. Seroneutralization applied on a subset of 156 serum samples confirmed these results. None of the 8 human serum samples was NiV seropositive with the seroneutralization test. One virus isolate exhibiting cytopathic effect with syncytia was obtained from 769 urine samples collected at roosts of P. lylei specimens. Partial molecular characterization of this isolate demonstrated that it was closely related to NiV. These results strengthen the hypothesis that flying foxes could be the natural host of NiV. Surveillance of human cases should be implemented

CTX-M β-Lactamases in Escherichia coli from Community-acquired Urinary Tract Infections, Cambodia

The prevalence of CTX-M β-lactamases has reached a critical level, which highlights the need for study of their spread in developing countries

Understanding Human-Plasmodium falciparum Immune Interactions Uncovers the Immunological Role of Worms

BACKGROUND: Former studies have pointed to a monocyte-dependent effect of antibodies in protection against malaria and thereby to cytophilic antibodies IgG1 and IgG3, which trigger monocyte receptors. Field investigations have further documented that a switch from non-cytophilic to cytophilic classes of antimalarial antibodies was associated with protection. The hypothesis that the non-cytophilic isotype imbalance could be related to concomittant helminthic infections was supported by several interventions and case-control studies. METHODS AND FINDINGS: We investigated here the hypothesis that the delayed acquisition of immunity to malaria could be related to a worm-induced Th2 drive on antimalarial immune responses. IgG1 to IgG4 responses against 6 different parasite-derived antigens were analyzed in sera from 203 Senegalese children, half carrying intestinal worms, presenting 421 clinical malaria attacks over 51 months. Results show a significant correlation between the occurrence of malaria attacks, worm carriage (particularly that of hookworms) and a decrease in cytophilic IgG1 and IgG3 responses and an increase in non-cytophilic IgG4 response to the merozoite stage protein 3 (MSP3) vaccine candidate. CONCLUSION: The results confirm the association with protection of anti-MSP3 cytophilic responses, confirm in one additional setting that worms increase malaria morbidity and show a Th2 worm-driven pattern of anti-malarial immune responses. They document why large anthelminthic mass treatments may be worth being assessed as malaria control policies

Numerical Simulation of Liquid Injection into an Anisothermal Dense Fluidized Bed

International audienceFluidized beds are widely used in reactive industrial processes such as: olefins production, oil cracking or uranium fluorination because of their high efficiency mixing properties. In such processes, the chemical reaction is strongly dependent on the temperature and liquid is injected into the reactor in order to cool it. The experimental data of the time evolution of the gas temperature in an anisothermal dense fluidized bed with a liquid injection provided by INEOS is first compared with the results predicted by a simple model with an assumption of a perfectly mixed fluidized bed (uniform solid and temperature distribution in the bed). The results of this simple model show that the time evolution of the gas temperature is accurately predicted. Additionally, we point out that the wall-to-bed heat transfer plays a crucial role of the gas temperature in the bed. Then, we performed 3-D numerical simulations that let us investigate local interactions between phases and heat transfer with wall. The simulations show that the liquid evaporates quickly and the temperature is in a satisfactory agreement with the experiment data