Application of Acoustic Agglomeration to Reduce Fine Particle Emissions from Coal Combustion Plants
Removal of fine particles (smaller than 2.5 μm) from industrial flue gases is, at present, one of the most important problems in air pollution abatement. These particles, which are hazardous because of their ability to penetrate deeply into the lungs, are difficult to remove by conventional separation technology. Sonic energy offers a means to solve this problem. The application of a high-intensity acoustic field to an aerosol induces agglomeration processes which changes the size distribution in favor of larger particles, which are then easier to precipitate with a conventional separator. In this work, we present a semiindustrial pilot plant in which this process is applied for reduction of particle emissions in coal combustion fumes. This installation basically consists of an acoustic agglomeration chamber with a rectangular cross-section, driven by four high-power and highly directional acoustic transducers of 10 and/or 20 kHz, and an electrostatic precipitator (ESP). In the experiments, a fluidized be...
Basic and theoretical operation of ESPs
In electrostatic precipitators (ESPs) the separation of particles from flue gases is based on electrical means. The separation process can be divided into five essential steps which are schematically illustrated in Figure 3.1: 
 
1. 
 
generation of charge carriers (section 3.2); 
 
 
 
 
2. 
 
charging of the particles (section 3.3); 
 
 
 
 
3. 
 
deflection and separation of the particles (sections 3.4, 3.5); 
 
 
 
 
4. 
 
dust deposition (section 3.6); 
 
 
 
 
5. 
 
dust removal (section 3.7). 
 
 
 
 
 
 
In most applications the steps are not as isolated as represented here, but the steps can happen all in one operational section. These are the so-called single-stage precipitators, which are the most important configurations for industrial processes (Figure 3.2a). In so-called two-stage precipitators steps 1/2 are executed separately from steps 3/4/5, i.e. in the first stage the ions are produced and the particles are charged while in the second stage the particles are collected and removed (Figure 3.2b). The two-stage configur- ations are only used in small-scale applications as, for example, clean room technology. Since single-stage precipitators have a far greater industrial significance than two-stage ESPs, the discussions will be confined to the first. However, most of the presented subjects and equations can be equally applied to two-stage configurations.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.