MODELING OF A DUSTED GAS FLOW CLEANING PROCESS USING A KINEMATIC MODEL OF THE INTERACTION OF DISPERSED PARTICLES WITH DROPLETS IN A WET SCRUBBER

A mathematical model is proposed for the scavenging process of the dispersed particles by droplets in a wet scrubber under excess spray density in Venturi tube within kinematic approach of the interaction of particles in countercurrent gas-dispersed flows, which refines the existing engineering model, taking into account the spatial size variation of the droplets, due to their coagulation with wet slurry droplets and uncaptured particles entering a wet scrubber from the Venturi tube. The results of calculations with the adopted mathematical model showed that in case of possibility to organize the spraying of a gas flow in a scrubber with 300–500 micron droplets aerosol at a specific spray density of about 1 liter/m3, a 1–2 meters wide layer of droplets ensures effective absorption of both uncaptured PM2.5 solid particles, and the slurry droplets from the Venturi tube. The ejection of the slurry droplets into a wet scrubber from the Venturi tube, and the associated increase in the size of the scrubber droplets due to coagulation with slurry droplets, does not noticeably affect the efficiency of the dusted gas stream cleaning. An adopted mathematical model was applied to calculate the capture of particles by droplets in cylindrical and conical scrubbers. Due to the increase in a residence time of the droplets upon increased velocity of the countercurrent gas flow, the efficiency of gas cleaning from dispersed particles in a conical scrubber appears to be higher than in a cylindrical scrubber. However, with an increase in the spray density above 2 liter/m3 and with droplet diameters greater than 1000 microns, the efficiency of the conical scrubber decreases, which is associated to an increase in the escape of a significant proportion of massive drops to the walls with a reduction in the scrubber reactor cross-section. Bibl. 21, Fig. 4.

Performance of Sulfide-Driven Fuel Cell Aerated by Venturi Tube Ejector

Hydrogen sulfide is frequently met in natural waters, like mineral springs, but mostly it is found in marine water with low renewal rate. The Black Sea has extremely high hydrogen sulfide content. It can be utilized in different ways, but the most promising one is direct conversion into electricity. This result can be attained by a sulfide-driven fuel cell (SDFC), converting sulfide to sulfate thus releasing electric energy up to 24 GJ/t. One of the most important problems is the mass transfer limitation on oxygen transfer in the cathode space of the fuel cell. This problem can be solved using a gas diffusion electrode or highly efficient saturation by oxygen in an ejector of the Venturi tube type. This work presents experimental data in laboratory-scale SDFC for sulfide conversion into sulfate, sulfite and polysulfide releasing different amounts of electric energy. Two types of aeration are tested: direct air blow and Venturi-tube ejector. Besides pure graphite, two catalysts, i.e., cobalt spinel and zirconia-doped graphite were tested as anodes. Experiments were carried out at initial sulfide concentrations from 50 to 300 mg/L. Sulfate, sulfite and thiosulfate ions were detected in the outlet solutions from the fuel cell. The electrochemical results show good agreement with the chemical analyses. Most of the results show attained high efficiencies of the fuel cell, i.e. up to 80%. The practical applications of this method can be extended for other purposes, like treatment of polluted water together with utilization as energy.

A Wet Gas Metering System Based on the Extended-Throat Venturi Tube

Although the use of a classical Venturi tube for wet gas metering has been extensively studied in the literature, the use of an extended-throat Venturi (ETV) tube has rarely been reported since its first proposal by J. R. Fincke in 1999. The structure of an ETV is very simple, but due to the complexity of multiphase flow, its theoretical model has not been fully established yet. Therefore, in this paper theoretical models have been developed for the convergent and throat sections of an ETV, and the gradients of front and rear differential pressures are derived analytically. Several flowrate algorithms have been proposed and compared with the existing ones. Among them, the iteration algorithm is found to be the best. A reasonable explanation is provided for its performance. The relationship between the differential pressure gradient and the flowrate relative error is also studied, such that the relative error distributions varying with ETV measured flowrates can be derived. The gas flowrate error of ETV increases with the liquid content whilst the liquid flowrate error of ETV decreases with the liquid content, and the relative errors of liquid flowrate are generally 2 to 3 times larger than that of the gas flowrate. Finally, the ETV tends to be more accurate than the classical Venturi tube. The ETV can be designed more compact under the same signal intensity due to its significantly higher velocity in the throat section.