Paul C. Yue

Hydrogen Production by the Thermophilic Bacterium, Thermotoga neapolitana

Virtually all members of the order Thermotogales have demonstrated the ability to produce hydrogen; however, some members of this order produce considerably greater quantities than others. With one representative of this order, Thermotoga neapolitana, we have consistently obtained accumulation of 25-30% hydrogen with 12-15% carbon dioxide as the only other prominent product in the batch reaction. In contradistinction to information widely disseminated in the literature, we have also found that most members of this order tolerate and appear to utilize the moderate amounts of oxygen present in the gaseous phase of batch reactors (6-12%), with no apparent decrease in hydrogen production. Hydrogen accumulation has been widely reported to inhibit growth of Thermotogales. While this may be true at very high hydrogen tensions, we have observed log phase bacterial morphology (rods) even in the presence of 25-35% hydrogen concentrations. To maximize hydrogen production and minimize production of hydrogen sulfide, inorganic sulfur donors are avoided and the cysteine concentration in the medium is increased. We and others have demonstrated that different members of the order Thermotogales utilize a wide variety of feedstocks, including complex carbohydrates and proteins. Thus, it appears that organisms within this order have the potential to utilize a variety of organic wastes and to cost-effectively generate hydrogen.

The Continuous Flow Condensation Nucleus Counter. II

The original version of the continuous flow counter has been improved and redesigned to run automatically with a rotary sequencing valve and data processing system. As previously described, the counter was developed at the Environmental Measurements Laboratory for use with diffusion batteries because they require a constant flow of aerosol for particle size measurement. The automated system is used extensively for measurement of the concentration and particle size distribution of indoor and outdoor aerosols. The operating conditions are evaluated to determine the effect of temperature deviation and alcohol dilution. Laboratory measurements of both the dew point and the light transmission show the diameter of the alcohol drops to vary from 13 μm at nucleus concentration of 1000/cm3 to 5.5 μm at 300,000/cm3. A recent calibration shows the new counter to be nearly 100% efficient for condensation nuclei ranging from 90 to 5 nm in diameter.

Evaluation of a Backscatter Imaging LDV System and its Application to a Pilot-Scale Circulating Fluidized Bed

ABSTRACT This study focuses on the evaluation and application of a backscatter imaging LDV (laser Doppler velocimeter) system (BILS) built by TSI Inc. (Shoreview, Minn.). This nonintrusive instrument has the ability to record particle images and velocity data simultaneously. A series of validation tests was conducted prior to measuring particle velocity in a turbulent system. A set of experiments was conducted to measure terminal velocity and particle size for five different-size cuts of near-spherical, Nu-Pareil particles, and the results were compared with the standard drag curve, which showed good agreement. The imaging data were used to estimate the sphericity (Φ) of the particles. The data confirmed that Φ was close to 1 (0.98 < Φ < 0.99). The system was then used to measure particle velocity in a cold flow circulating fluidized bed at various operating conditions. The effect of operating conditions, such as superficial gas velocity and solids circulation rate, on the solids velocity was studied. The mean solids velocity near the wall was found to increase with increasing superficial gas velocity and decreasing solids circulation rate. The granular temperature was also estimated and was found to increase with increasing distance from the wall. The granular temperature was found to lie in the range of 0.1–1.0 m2/s2 for the operating conditions studied. The granular temperature calculations also showed that the flow of particles moving downwards was more ordered than the flow moving up.

Comparison of two identical continuous flow nucleus counters

Abstract A review of the literature on the comparison of identical nucleus counters showed that only Pollak counters exhibit a high degree of agreement. In view of the difficulties encountered by early investigators in obtaining good agreement, we subjected two Sinclair continuous flow nucleus counters to similar tests using room aerosol. Our results indicate that under normal operating conditions the continuous flow counters can agree to within 10% of concentration measurements. We also inferred from our measurements that these counters have good reproducibility.

Hydrodynamics of a Transport Reactor Operating in Dense Suspension Upflow Conditions for Coal Combustion Applications

A series of experiments were conducted in the 0.3-meter diameter, 15.45-m high cold flow circulating fluid bed (CFB) test facility at the National Energy Technology Laboratory (NETL) of the U. S. Department of Energy. Operation of the CFB demonstrated that high density conditions can be achieved throughout the entire riser with sufficiently high solid fluxes in a riser taller than what has been previously reported in the literature. Tests were conducted on Geldart type B, 60 μm diameter, glass beads at two different gas velocities (5.1 and 7.8 m/s). The riser’s axial solids fraction profile provided distinct characteristics that enabled us to differentiate between dense suspension upflow (DSU) and core annular flow regimes. The apparent solids holdup in the riser exceeded 7% when operating in DSU. A fiber optic probe was used to measure particle velocities near the wall 8.5 m above the solids entry. These measurements did not always record upward particle velocities when in DSU conditions. A number of possible reasons are identified and discussed. Solid fluxes greater than 250 kg/m2 -s for 5.1 m/s and 350 kg/m2 -s at 7.8 m/s appeared to be sufficient to achieve DSU conditions. The trend in the measured particle velocities near the wall was also consistent with these transitions. The transition from core annular conditions to DSU operations depended upon both gas velocity and solids flux and was in good agreement with an existing correlation found in the literature.Copyright

TOTAL PARTICLE MONITORING AND DETECTION

ABSTRACT One of the methods of detecting particles in the ultrafine size range (diameter <0.05 μm) is by condensation nuclei counters. Such condensation nuclei counters have a broad range of application including clean room monitoring, the characterization of contaminants in fossil energy process streams, and atmospheric monitoring. Based on the condensation of a saturated vapor, the method can amplify the size of the particles which are being studied by several orders of magnitude so that they can be detected by standard optical methods. However, the lower size limit of detectability is dependent on the proper choice of parameters that create the saturation conditions. This paper presents results of the counting sensitivity tests of two condensation-type counters (the Pollak and the Sinclair continuous-flow counters). The results indicate that these instruments should be operated close to the self-nucleation limit in order to ensure total particle counting.