The circulating floating bed reactor: effect of particle size distribution of the carrier on ammonia conversion

2000 ◽  
Vol 41 (4-5) ◽  
pp. 393-400 ◽  
Author(s):  
J.M. Garrido-Fernandez ◽  
R. Méndez ◽  
J.M. Lema ◽  
V. Lazarova
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
G Protein ◽  
Biomass Concentration ◽  
Biomass Accumulation ◽  
Ammonia Removal ◽  
Operating Conditions ◽  
Nitrification Rate ◽  
Ammonia Conversion ◽  
Biomass Activity

Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier with different size distribution were operated to study the effect of the particles size of the carrier on biomass accumulation and nitrification performance. Operating conditions were similar in the three systems: ammonia concentrations around 50 mg-N–NH4+/ L, ammonia loading rates up to 1.2 kg N–NH4+/m3·d and temperatures between 14 and 27°C. Accumulation of nitrite was observed until day 65th. This w as result both of the inhibition of nitrite oxidation by free ammonia until day 20th and the insignificant accumulation of a biomass with low nitrite oxidising capacity between days 20 and 65th. Ammonia conversion rate and removal efficiency were higher in the reactor with lower particle size, R3 (nitrification rate of 1.1 kg N–NH4+/m3·d and ammonia removal of 97% at 16°C), than in R2 or R1 (nitrification rate of 1.0 kg N–NH4+/m3·d and ammonia removal of 90% at 16°C). The better efficiency in R3 was obtained as a result of the higher specific surface of the biofilm developed. Biomass activity was similar in the three reactors (2.2 and 1.12 g N/g protein · d at 30 and 15°C, respectively). Both the biomass evolution with time and biomass retention in the systems was practically not influenced by the size of particle. Biomass concentration of 1.2 g protein/L was retained in the carrier and up to 20% of the newly produced biomass was retained in the CFBRs.

Effect of Particle Size Distribution on the Deep-Bed Capture Efficiency of an Exhaust Particulate Filter

2014 ◽  
Author(s):  
Sandeep Viswanathan ◽  
Stephen S. Sakai ◽  
Mitchell Hageman ◽  
David E. Foster ◽  
Todd Fansler ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Deposition ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Particulate Emissions ◽  
Filter Loading ◽  
Particle Sizer ◽  
The Impact

The exhaust filtration analysis system (EFA) developed at the University of Wisconsin – Madison was used to perform micro-scale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark-ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of particle size distribution on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.

Hydrodynamics of Multiple Size Particles in a Liquid Fluidized Bed Classifier

2003 ◽  
Author(s):  
Dinesh Gera ◽  
Madhava Syamlal ◽  
Thomas J. O’Brien
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Volume Fraction ◽  
Fluid Model ◽  
Operating Conditions ◽  
Particle Sizes ◽  
Two Fluid Model ◽  
Predicted Values

A two fluid model is extended to an N-phase, multi-fluid model, in which each particulate phase represents a collection of particles with identical diameter and density. The current N-phase model is applied to a fluidized bed classifier with six different particle sizes to investigate the effects of different operating conditions—fluidizing liquid flow rate, feed voidage, and particle size distribution in the feed stream—on the particle size distribution inside the classifier and the discharge streams. The predicted volume fraction of different particle sizes is compared with the experimental data reported by Chen et al. (2002) for two columns, 191 mm and 292 mm in diameter, each having different geometries and containing glass beads of different sizes fluidized with water. A fairly good agreement is observed between the measured and predicted values for mono- and poly-dispersed systems.

Simulation of a periodic anaerobic baffled reactor (PABR): steady state and dynamic response

2002 ◽  
Vol 45 (10) ◽  
pp. 81-86 ◽  
Author(s):  
K. Stamatelatou ◽  
G. Lyberatos
Keyword(s):  
A Priori ◽  
Operation Mode ◽  
Biomass Concentration ◽  
Biomass Accumulation ◽  
Operating Conditions ◽  
High Rate ◽  
Organic Loading Rate ◽  
Experimental Conditions ◽  
Anaerobic Baffled Reactor ◽  
Reactor Dynamics

The Periodic Anaerobic Baffled Reactor (PABR) is a novel high-rate configuration for wastewater treatment. The reactor resembles an ABR with the compartments arranged in a circular manner. The feeding and effluent points are periodically set in different compartments by proper manipulation of valves that determine the flow pattern. This way of feeding makes the reactor response oscillating and gives the PABR a great flexibility in the operation mode. A 15 litre PABR was operated on a gelatin based medium under steady and variable organic loading rate. The experimental conditions were simulated using a mathematical model whose primary feature was that each compartment was considered as a two-section tank, each section with a different biomass concentration in them. The degree of biomass accumulation was determined indirectly by the operating conditions and the reactor dynamics and was not set a-priori.

Monitoring Fluidization Dynamics for Detection of Changes in Fluidized Bed Composition and Operating Conditions

1999 ◽  
Vol 121 (4) ◽  
pp. 887-894 ◽  
Author(s):  
J. Ruud van Ommen ◽  
Jaap C. Schouten ◽  
Cor M. van den Bleek
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Pressure Fluctuations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Gradual Change ◽  
Monitoring Method ◽  
Superficial Gas Velocity

In many industrial applications of gas-solids fluidized beds, it is worthwhile to have an on-line monitoring method for detecting changes in the hydrodynamics of the bed (due for example to agglomeration) quickly. In this paper, such a method, based on the short-term predictability of fluidized bed pressure fluctuations, is examined. Its sensitivity is shown by experiments with small step changes in the superficial gas velocity and by experiments with a gradual change in the particle size distribution of the solids in the bed. Furthermore, it is demonstrated that the method is well able to indicate if a stationary hydrodynamic state has been reached after a change in the particle size distribution (a ‘grade change’).

Development of the Bed Particle Size Distribution in a Circulating Fluidized Bed Combustor

2005 ◽  
Author(s):  
Cornelis Klett ◽  
Ernst-Ulrich Hartge ◽  
Joachim Werther
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Calculated Data ◽  
Operating Conditions ◽  
Attrition Rate ◽  
Balance Model ◽  
Fluidized Bed Combustor

In the present work a particle population balance model for a circulating fluidized bed combustor (CFBC) is developed that allows a description of the fate of individual particles in terms of attrition and transport effects. Besides the operating conditions and the particle size distribution the residence time of particles in the system is considered in the modeling of abrasion and shrinking of particles. The model takes account of the fact that fresh particles have a higher attrition rate than particles which have stayed for some time already in the system. The model aims at the description of the dynamic adjustment of the particle size distributions in a given system. The model has been validated with experimental data from a pilot-plant combustor, i.e. a CFBC with an inner diameter of 0.1 m and a height of 15 m. A comparison between experimental and calculated data shows the applicability of the model.

scholarly journals Tailoring hydroxyapatite microspheres by spray-drying for powder bed fusion feedstock

2021 ◽  
Author(s):  
Pedro Navarrete-Segado ◽  
Christine Frances ◽  
David Grossin ◽  
Mallorie Tourbin
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Spray Drying ◽  
Laser Processing ◽  
Operating Conditions ◽  
Air Pressure ◽  
Final Particle ◽  
Powder Bed ◽  
Powder Feedstock

The present work deals with a study on the physical characteristics of hydroxyapatite microspheres produced by spray-drying process through different operating conditions. Obtained hydroxyapatite microspheres will be used as powder feedstock in powder bed selective laser processing additive manufacturing technologies where the flowability and the particle size distribution of the powder feedstock is of special importance. Spray air pressure and solid content of the slurries were the most influent parameters to control the final particle size distribution, while higher air pressure and temperatures gave the higher process recovery rate. The use of polyvinyl alcohol as organic binder increased the granules strength. The produced hydroxyapatite microspheres were found to fulfil the powder bed selective laser processing feedstock requirements, keeping the physico-chemical properties of the material. These promising results confirm the use of a spray dryer as an efficient method for the production of hydroxyapatite microspheres for powder bed selective laser processing.

Particle size distribution to design and operate an APT process for agricultural wastewater reuse

2006 ◽  
Vol 53 (7) ◽  
pp. 43-49 ◽  
Author(s):  
A. Chavez ◽  
C. Maya ◽  
B. Jimenez
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Contact Time ◽  
High Performance ◽  
Wastewater Reuse ◽  
Primary Treatment ◽  
Operating Conditions ◽  
High Rate ◽  
Treatment Objective

Total suspended solids is a parameter commonly used to operate and design coagulation–flocculation processes. Nevertheless, their application for an advanced primary treatment (a high performance but low dose demand coagulation processes coupled with a high rate sedimentator, sometimes called enhanced primary treatment) is not the best option to produce an effluent for agricultural irrigation. This paper compares the best operating conditions obtained using the TSS or the PSD (particle size distribution) as parameters to follow the efficiency. The treatment objective was to remove particles >20 μm, in such conditions that the effluent can contain organic matter and nutrients necessary for crops with a reduced number of helminth ova (with sizes between 20 to 80 μm). Using the TSS as parameter, the best coagulation (460 s−1, 60 s contact time and 300 μmolAl/L) and flocculation (20 s−1 with 15 min) conditions produced an effluent with 1.2 HO/L. To obtain a similar results but using operating conditions determined with the PSD at a three times lower coagulant dose can be employed (diminishing operating costs and reducing the quantity of sludge produced), and a reduction on energy consumption of around eight times can be reached. Best operating conditions defined using the PSD (160 s−1, 60 s contact time and 100 μmolAl/L) produced an effluent with <0.4 HO/L.

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