Integrated FCC riser—regenerator dynamics studied in a fluid catalytic cracking pilot plant

In this paper a dynamic simulator of the fluid catalytic cracking (FCC) pilot plant, operating in the Chemical Process Engineering Research Institute (CPERI, Thessaloniki, Greece), is presented. The operation of the pilot plant permits the execution of case studies for monitoring of the dynamic responses of the unit, by imposing substantial step changes in a number of the manipulated variables. The comparison between the dynamic behavior of the unit and that predicted by the simulator arise useful conclusions on both the similarities of the pilot plant to commercial units, along with the ability of the simulator to depict the main dynamic characteristics of the integrated system. The simulator predicts the feed conversion, coke yield and heat of catalytic reactions in the FCC riser on the basis of semi-empirical models developed in CPERI and simulates the regenerator according to the two-phase theory of fluidization, with a dilute phase model taking account of postcombustion reactions. The riser and regenerator temperature, the stripper and regenerator pressure drop and the composition of the regenerator flue gas are measured on line and are used for verification of the ability of the simulator to predict the dynamic transients between steady states in both open- and closed-loop unit operation. All the available process variables such as the reaction conversion, the coke yield, the carbon on regenerated catalyst and the catalyst circulation rate are used for the validation of the steady-state performance of the simulator. The comparison between the dynamic responses of the model and those of the pilot plant to step changes in the feed rate and preheat temperature reveals the ability of the simulator to accurately depict the complex pilot process dynamics in both open- and closed-loop operation. The dynamic simulator can serve as the basis for the development of a model-based control structure for the pilot plant, alongside its use as a tool for off-line process optimization studies.     

The Control of Selected Micro‐Organisms During the Malting Process

The micro‐organisms associated with malt have an important influence on quality parameters. Although it was not possible to eliminate the growth of micro‐organisms entirely during the malting process, it was possible to control particular groups by applying some simple procedures. A three steep schedule was associated with increased fungal growth which was not observed when a two steep schedule was used. Fungal proliferation could also be reduced by the use of hop beta‐acids. The use of sodium hypochlorite, potassium hydroxide, hydrochloric acid and hop beta‐acids reduced or eliminated E. coli. The most effective means of controlling total micro‐flora was an alternate acid/alkaline wash. There was no evidence that a correlation existed between growth site and microbial loading for the years studied. Furthermore, whilst many of the barley associated micro‐organisms were able to secrete brewing related enzymes, the activities of these were too low to have any significant effect during mashing.     

Developing Tadpole Xenopus laevis as a Comparative Animal Model to Study Mycobacterium abscessus Pathogenicity

Mycobacterium abscessus (Mab) is an emerging, nontuberculosis mycobacterium (NTM) that infects humans. Mab has two morphotypes, smooth (S) and rough (R), related to the production of glycopeptidolipid (GPL), that differ in pathogenesis. To further understand the pathogenicity of these morphotypes in vivo, the amphibian Xenopus laevis was used as an alternative animal model. Mab infections have been previously modeled in zebrafish embryos and mice, but Mab are cleared early from immunocompetent mice, preventing the study of chronic infection, and the zebrafish model cannot be used to model a pulmonary infection and T cell involvement. Here, we show that X. laevis tadpoles, which have lungs and T cells, can be used as a complementary model for persistent Mab infection and pathogenesis. Intraperitoneal (IP) inoculation of S and R Mab morphotypes disseminated to tadpole tissues including liver and lungs, persisting for up to 40 days without significant mortality. Furthermore, the R morphotype was more persistent, maintaining a higher bacterial load at 40 days postinoculation. In contrast, the intracardiac (IC) inoculation with S Mab induced significantly greater mortality than inoculation with the R Mab form. These data suggest that X. laevis tadpoles can serve as a useful comparative experimental organism to investigate pathogenesis and host resistance to M. abscessus.     

Genotypic characterization of Brochothrix thermosphacta isolated during storage of minced pork under aerobic or modified atmosphere packaging conditions

A total of 306 colonies were isolated from the selective medium for Brochothrix spp., during the spoilage of minced pork stored at 0, 5, 10 and 15°C and packed aerobically and under modified atmosphere packaging conditions (MAP). Brochothrix biodiversity was assessed by Pulsed Field Gel Electrophoresis (PFGE), and representative strains were further analysed by Rep-PCR using primer (GTG)(5) and Sau-PCR with primers SAG(1)and SAG(2). Although, different results were obtained from the different methods, a significant diversity among isolates recovered from aerobic conditions was observed. On the contrary, isolates from MAP showed a lower degree of heterogeneity. The storage conditions affected the Brochothrix diversity, the strains isolated in the initial stage being different from the ones present at the final stage of storage at chill temperatures. A representative number of isolates, based on the results of the clustering by molecular methods, were subjected to 16S rRNA gene sequencing, revealing that all belonged to Brochothrix thermosphacta.     

Optimal operability by design in a methanol reforming-PEM fuel cell autonomous power system

Enhanced process operability through suitable design decisions and control structure selection is achieved for a methanol reforming – proton exchange membrane (PEM) fuel cell autonomous power system. Two alternative flowsheet configurations are formulated and evaluated based on their ability to compensate for the effects of multiple simultaneous disturbances, such as catalyst deactivation, on the integrated power system. A previously developed disturbance sensitivity control (DiSc) framework, investigates the optimal steady-state response of a multi-variable control system applied to the process. The overall performance is assessed based on the steady-state effort required by the system controls to maintain specific targets at the desired set points. The sensitivity analysis utilizes non-linear models that accurately calculate the steady-state contribution of a set of potential manipulated variables toward satisfying the control objectives optimally. A steady-state controllability index that encompasses the relative variation of the system controlled and manipulated variables from desired operating points and the system efficiency expressed in terms of mass of fuel per generated kWh are utilized for the overall assessment of the process flowsheet operability. The design analysis framework enables the identification of process flowsheets and control structures that ensure high efficiency, improved behavior under disturbance influence, and efficient handling of system interactions.     

Modifying a dental ceramic by bioactive glass via the sol–gel route: Characterization and bioactivity investigation

The modification of a widely used dental ceramic by a bioactive glass via sol–gel method resulted in the fabrication of novel dental ceramic composites with bioactive behavior. The presence of leucite (Lt), apatite (Ap), various calcium silicate phases (CS) and a glassy aluminosilicate matrix were detected, while after sintering the predominance of wollastonite (W) among the other calcium silicate phases was observed, along with further crystallization of apatite. Concerning the bioactivity, the onset of the apatite formation was directly dependent on the bioactive glass amount, while a delay of the sintered specimens compared to the raw powders was also observed.     

Variation in the composition of Cretan avocado cultivars during ripening

The effect of ripening on the chemical characteristics of fruits of the avocado (Persea americana) cultivars Ettinger, Fuerte and Hass was investigated. A study of some quality parameters of these main avocado cultivars grown on the island of Crete was performed. As the fruit ripened, a decrease in the moisture content was observed, with a high degree of correlation for all the cultivars. At the same time an increase in the fat and protein contents was measured. The content of total sugars was high in the unripe fruit but decreased during ripening. The fatty acid composition of the oil extracted from the fruit pulp was determined by gas chromatographic analysis. The oil of the edible portion of the fruit was rich in oleic, palmitic, linoleic and palmitoleic acids, while stearic acid was present in small quantities. During the ripening process the amount of palmitic acid decreased and that of oleic acid increased in all the cultivars. The ratio of polyunsaturated to saturated fatty acids, which is considered as an indicator of the nutritional value of the fruit, was also calculated. No significant differences were observed between the cultivars. Principal component analysis was also performed to examine the relationship among the quality variables of the cultivars. From these data, Fuerte was considered to be the cultivar with the best characteristics. Copyright © 2004 Society of Chemical Industry     

ISCOMs vaccine against experimental leishmaniasis

The major surface glycoprotein (gp63) of Leishmania major incorporated into the immunostimulating complexes (ISCOMs) was used to protect Balb/c mice against experimental infection. Two intraperitoneal vaccinations with low doses of gp63 into ISCOMs (gp63-ISCOMs) induced protective immunity in vaccinated mice as indicated by reduced inflammation and suppressed lesions after experimental challenge. An augmented IgG-specific secretion and a specific switching towards the IgG2a isotype was observed in the serum of vaccinated mice. Gp63-ISCOMs primed spleen cells restimulated in vitro with soluble Leishmania antigen (SLA) or live parasites displayed strong gp63-specific proliferative responses and secreted high levels of interleukin-2, interferon gamma and interleukin-10 but not interleukin-4. No delayed type hypersensitivity response to either SLA or LV39 was detected. These data indicate that gp63-ISCOMs induced a protective immunity in the susceptible Balb/c mice against Leishmania challenge, modulating the immune response towards a Th1 rather than Th2 type.     

Nutritional considerations in children undergoing bone marrow transplantation

Bone marrow transplantation is often associated with multiple organ failure which is usually reversible. Oral mucositis and dysphagia, vomiting, diarrhoea, protein losing enteropathy, transient exocrine pancreatic impairment, hypoalbuminaemia, biochemical trace element and mineral deficiencies are all common following transplantation and have profound nutritional consequences. Malnutrition affects negatively the clinical outcome. Nutritional support is provided to malnourished patients and those who suffer deterioration in nutritional status despite the provision of dietetic counselling. Only a few randomised studies comparing enteral with parenteral nutrition after transplant exist. Both enteral tube feeding (in the absence of mucositis) and parenteral nutrition are effective in maintaining nutritional status. However, enteral nutrition is associated with a better nutritional response and fewer complications than parenteral. With existing enteral and parenteral nutrition regimens close monitoring of trace element and mineral status is required.