Development, Validation And Implementation Of Multiple Radioactive Particle Tracking Technique

Computer Automated Radioactive Particle Tracking (CARPT) technique has been successfully utilized to measure the velocity profiles and mixing parameters in different multiphase flow systems where a single radioactive tracer is used to track the tagged phase. However, many industrial processes use a wide range of particles with different physical properties where solid particles could vary in size, shape and density. For application in such systems, the capability of current single tracer CARPT can be advanced to track more than one particle simultaneously. Tracking multiple particles will thus enable to track the motion of particles of different size shape and density, determine segregation of particles and probing particle interactions. In this work, a newly developed Multiple Radioactive Particle Tracking technique (M-RPT) used to track two different radioactive tracers is demonstrated. The M-RPT electronics was developed that can differentiate between gamma counts obtained from the different radioactive tracers on the basis of their gamma energy peak. The M-RPT technique was validated by tracking two stationary and moving particles (Sc-46 and Co-60) simultaneously. Finally, M-RPT was successfully implemented to track two phases, solid and liquid, simultaneously in three phase slurry bubble column reactors

Bio-Energy Production from Anaerobic Digestion of Animal and Farm Wastes

Track II: Transportation and BiofuelsIncludes audio file (20 min.)US produces annually huge amount of animal and farm wastes (e.g. only cow manure in amount of about 1.8 billion tons). These wastes can be valuable source of renewable energy besides overcoming the environmental problems caused by them such as greenhouse gas effect of methane emission of 22 times worse than carbon dioxide, surface and ground water contamination, odor, dust, ammonia leaching, etc. In this project we systematically studied the process, kinetics, microorganisms interaction and population, and the effects of design and operating parameters on reactor design and scale up of cow manure digestion for bioenergy production and for wastes treatment by developing and implementing advanced imaging, visualization and computational techniques such as computational fluid dynamics (CFD), novel multiple radioactive particles tracking technique (MRPT), novel dual source computed tomography (DSCT), and microbiology imaging techniques. New design and conditions of anaerobic digesters that can reduce significantly the inactive volume and improve the digesters performance have been identified and recommended. In addition, for the first time, the energy produced has been related to the energy introduced in order to maximize the energy output while minimizing the energy input through the mixing power consumed. It is hoped that the findings will be applied in the field to promote bioenergy production and eliminate major environmental pollution problems

Airlift bioreactor for biological applications with microbubble mediated transport processes

Airlift bioreactors can provide an attractive alternative to stirred tanks, particularly for bioprocesses with gaseous reactants or products. Frequently, however, they are susceptible to being limited by gas–liquid mass transfer and by poor mixing of the liquid phase, particularly when they are operating at high cell densities. In this work we use CFD modelling to show that microbubbles generated by fluidic oscillation can provide an effective, low energy means of achieving high interfacial area for mass transfer and improved liquid circulation for mixing. The results show that when the diameter of the microbubbles exceeded 200 µm, the “downcomer” region, which is equivalent to about 60% of overall volume of the reactor, is free from gas bubbles. The results also demonstrate that the use of microbubbles not only increases surface area to volume ratio, but also increases mixing efficiency through increasing the liquid velocity circulation around the draft tube. In addition, the depth of downward penetration of the microbubbles into the downcomer increases with decreasing bubbles size due to a greater downward drag force compared to the buoyancy force. The simulated results indicate that the volume of dead zone increases as the height of diffuser location is increased. We therefore hypothesise that poor gas bubble distribution due to the improper location of the diffuser may have a markedly deleterious effect on the performance of the bioreactor used in this work

IMPROVED BIOMASS UTILIZATION THROUGH REMOTE FLOW SENSING

The growth of the livestock industry provides a valuable source of affordable, sustainable, and renewable bioenergy, while also requiring the safe disposal of the large quantities of animal wastes (manure) generated at dairy, swine, and poultry farms. If these biomass resources are mishandled and underutilized, major environmental problems will be created, such as surface and ground water contamination, odors, dust, ammonia leaching, and methane emission. Anaerobic digestion of animal wastes, in which microorganisms break down organic materials in the absence of oxygen, is one of the most promising waste treatment technologies. This process produces biogas typically containing {approx}65% methane and {approx}35% carbon dioxide. The production of biogas through anaerobic digestion from animal wastes, landfills, and municipal waste water treatment plants represents a large source of renewable and sustainable bio-fuel. Such bio-fuel can be combusted directly, used in internal combustion engines, converted into methanol, or partially oxidized to produce synthesis gas (a mixture of hydrogen and carbon monoxide) that can be converted to clean liquid fuels and chemicals via Fischer-Tropsch synthesis. Different design and mixing configurations of anaerobic digesters for treating cow manure have been utilized commercially and/or tested on a laboratory scale. These digesters include mechanically mixed, gas recirculation mixed, and slurry recirculation mixed designs, as well as covered lagoon digesters. Mixing is an important parameter for successful performance of anaerobic digesters. It enhances substrate contact with the microbial community; improves pH, temperature and substrate/microorganism uniformity; prevents stratification and scum accumulation; facilitates the removal of biogas from the digester; reduces or eliminates the formation of inactive zones (dead zones); prevents settling of biomass and inert solids; and aids in particle size reduction. Unfortunately, information and findings in the literature on the effect of mixing on anaerobic digestion are contradictory. One reason is the lack of measurement techniques for opaque systems such as digesters. Better understanding of the mixing and hydrodynamics of digesters will result in appropriate design, configuration selection, scale-up, and performance, which will ultimately enable avoiding digester failures. Accordingly, this project sought to advance the fundamental knowledge and understanding of the design, scale up, operation, and performance of cow manure anaerobic digesters with high solids loading. The project systematically studied parameters affecting cow manure anaerobic digestion performance, in different configurations and sizes by implementing computer automated radioactive particle tracking (CARPT), computed tomography (CT), and computational fluid dynamics (CFD), and by developing novel multiple-particle CARPT (MP-CARPT) and dual source CT (DSCT) techniques. The accomplishments of the project were achieved in a collaborative effort among Washington University, the Oak Ridge National Laboratory, and the Iowa Energy Center teams. The following investigations and achievements were accomplished: Systematic studies of anaerobic digesters performance and kinetics using various configurations, modes of mixing, and scales (laboratory, pilot plant, and commercial sizes) were conducted and are discussed in Chapter 2. It was found that mixing significantly affected the performance of the pilot plant scale digester ({approx}97 liter). The detailed mixing and hydrodynamics were investigated using computer automated radioactive particle tracking (CARPT) techniques, and are discussed in Chapter 3. A novel multiple particle tracking technique (MP-CARPT) technique that can track simultaneously up to 8 particles was developed, tested, validated, and implemented. Phase distribution was investigated using gamma ray computer tomography (CT) techniques, which are discussed in Chapter 4. A novel dual source CT (DSCT) technique was developed to measure the phase distribution of dynamic three phase system such as digesters with high solids loading and other types of gas-liquid-solid fluidization systems. Evaluation and validation of the computational fluid dynamics (CFD) models and closures were conducted to model and simulate the hydrodynamics and mixing intensity of the anaerobic digesters (Chapter 5). It is strongly recommended that additional studies be conducted, both on hydrodynamics and performance, in large scale digesters. The studies should use advanced non-invasive measurement techniques, including the developed novel measurement techniques, to further understand their design, scale-up, performance, and operation to avoid any digester failure. The final goal is a system ready to be used by farmers on site for bioenergy production and for animal/farm waste treatment