Search

Abstract: A fluidized bed zero valent iron (ZVI) reactor was designed for nitrogen monoxide (NO) removal with typical flue gas temperatures based on ZVI's strong reducing abilities. Three different parameters: [...]

Solar thermochemical processes require the development of a high-temperature solar reactor operating at 1000-1500[degrees]C, such as solar gasification of coal and the thermal reduction of metal oxides as part of a two-step water splitting cycle. Here, we propose to apply 'an internally circulating fluidized bed' for a windowed solar chemical reactor in which reacting particles are directly illuminated. The prototype reactor was constructed in a laboratory scale and demonstrated on C[O.sub.2] gasification of coal coke using solar-simulated, concentrated visible light from a sun simulator as the energy source. About 12% of the maximum chemical storage efficiency was obtained by the solar-simulated gasification of the coke. [DOI: 10. 1115/1.2807213] Keywords: solar chemistry, solar chemical reactor, internally circulating fluidized bed, coal gasification, solar hydrogen

Propylene glycol-based aircraft deicing fluid (ADF) is sprayed on aircraft during cold weather to remove ice and snow or prevent ice formation. A large fraction of the fluid typically falls to the pavement where it mixes with stormwater. Since airport stormwater containing ADF can exert a high biochemical oxygen demand, biological treatment may be required. The objective of this study was to determine and compare the rates of ADF chemical oxygen demand (COD) removal in anaerobic complete-mix stirred tank reactors (CMSTRs), anaerobic filters (AFs), and anaerobic fluidized bed reactors (FBRs) treating acidified and nonacidified propylene glycol ADF at temperatures between 35 and 11[degrees]C. The AF and FBRs were initially operated in a continuous-flow mode. Subsequently, kinetic data were collected when the reactors were operated in batch mode. Maximum specific removal rates of 0.93, 0.30, and 0.045 g COD per g volatile solids per day were determined at temperatures of 35, 24, and 11[degrees]C, respectively. The rates of acidified and nonacidified ADF COD removal were not significantly different. An Arrhenius equation temperature correction coefficient ([theta]) of 1.11 was determined. The most significant increase in overall COD removal rates (mg COD/L-day) were a result of biomass immobilization and increased biomass concentration in AFs and FBRs. Final COD concentration in the CMSTR were chronically high (circa 700 mg/L), and did not decline after five additional days of batch reaction time, whereas no chronically high final COD concentrations were observed in AFs and FBRs. CE Database keywords: Fluidized beds; Kinetics; Aircraft; Biodegration; Ice control.

This paper examines the influence of bed segregation on the performance of an anaerobic fluidized bed bioreactor (AFBR) using both an integrated mathematical model previously described in Part I of this study, and experimental data obtained from a laboratory-scale AFBR continuous flow system and batch serum vial tests. Local hydrodynamics within the bed are shown to determine mixing intensities and patterns of bioparticles thereby controlling biofilm thickness and composition along the bed height. Results of the model simulations and the experimental data indicate that shallow biofilms that allow full substrate penetration are dominantly populated with faster growing micro-organisms. The internal mass transfer resistance in thicker biofilm significantly influences population distribution resulting in the increase of population of slower growing micro-organisms in a deeper layer of the biofilm. The serum bottle tests also confirm that microbial distribution inside a multispecies biofilm is determined by the hydrodynamic condition of the reactor. This study illustrates the importance of hydrodynamic regimes in the AFBR, and demonstrates the impact of bed segregation on bioparticle properties and total system performance. CE Database keywords: Mathematical models; Cisterns; Fluidized beds; Waste treatment; Simulation.

An integrated mathematical model for propylene glycol (PG) degradation in an anaerobic fluidized bed bioreactor is described. Special attention is put on biomass distribution, bed expansion, and bed segregation, associated with the biofilm accumulation process. In order to interpret the segregation of the bed during the initial development of the biofilm, the model postulates various mixing intensities along the bed height and thereby different exchange rates of microbial cells between the biofilm and the bulk liquid. The model incorporates stoichiometry of PG methanization, hydrodynamics, and reaction kinetics for elucidating microscopic interaction among microbial trophic groups inside the biofilm as well as the macroscopic behavior of the reactor such as bed expansion. A biofilm diffusion mechanism is also taken into account focusing on the spatial distribution of multiple species of micro-organisms. Employing moving boundaries makes the model flexible in computation, which permits simplifying the implementation of the biofilm accumulation and the bed expansion phenomena. CE Database keywords: Mathematical models; Cisterns; Fluidized beds; Waste treatment.

An aerobic fluidized bed reactor process with internal media cleaning to control attached biomass thickness was developed. Biomass control was achieved by the periodic creation of a turbulent zone within a specially designed cylindrical screened region surrounding the effluent port. A screen washer aided in keeping the cylindrical screen clean. A bed lifter produced turbulence throughout the bed to allow individual media particles to enter the cleaning zone for the removal of excess biofilm. The reactor system operated continuously without excessive biomass buildup on the support media and without the need for external media cleaning or recovery. Four analytical methods - systematic scanning electron microscope (SEM) analyses, granular activated carbon drained density, phospholipid analyses, and fluorescein diacetate activity (FDA) measurements - were modified/developed for use in characterizing the microbial population attached to the media of the fluidized bed. The SEM analyses was valuable for monitoring changes the cleaning cycle caused to the biofilm. Phospholipid and FDA analyses were found to have potential for use as design and monitoring tools of the process.

Design and operation of modified reverse-flow reactor (MRFR), which be use to treat gaseous pollutant from chemical plants, is presented.