Gas separation: processes – Electric or electrostatic field
Patent
1997-04-18
1999-12-21
Chiesa, Richard L.
Gas separation: processes
Electric or electrostatic field
055523, 096 69, 096 98, B03C 362
Patent
active
060034343
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for affecting droplets of liquid that are contained in a flow of gas. In addition, the present invention relates to an apparatus for carrying out this process.
In a large number of applications in which flowing gases are used, problems can be caused by droplets of liquid that are contained in the gas flow. Problems of this kind result, amongst other things, in gas turbines that operate with extremely high intake temperatures. In such applications, gas charged with particulate components, even of the smallest diameter, and condensation of gaseous harmful substances can lead to erosion and corrosion of the material in the turbine blades on a permanent basis. It is difficult to remove dust because dust particles become sticky at temperatures above 700.degree. C. On the transition to even higher temperatures, the melting point of such particles is exceeded, so that it becomes necessary to remove liquids. In principle, all types of dust separators are suitable for removing droplets, for example filtering separators, electro-separators, and cyclone-type separators. separators. Preferably, however, laminar and centrifugal separators are used to remove droplets. When this is done, the flow of gas is forced to change direction; the droplets of liquid do not conform to this change, and are thus deposited on a wall and removed from the flow of gas. However, it is not possible to remove the smallest droplets out in this way. It is a known fact that it is extremely difficult to remove droplets of liquid from a gas phase as their diameters become smaller, in particular when their diameters become less than 10 .mu.m. Attempts have been made to facilitate the collision and coagulation of droplets by means of a special gas guidance system it order to be able to remove the correspondingly large droplets in a simpler manner. It is preferred that electrofilters be used for this purpose, although these cannot be used in the temperature ranges discussed above.
DE 87 01 718 U1 describes an apparatus removing droplets from a gas phase that is essentially independent of temperature; in this apparatus, a magnetic field is generated in one area of the flow by applying electrical voltages. Appropriate magnetic or static charges are described in DE 11 37 980 A1 and in DE 31 51 125 A1. However, the processes and apparatuses described therein are not suitable for use in the range of very high temperatures, neither are they suitable for every kind of droplet. In particular, however, these known processes are not suitable for acting on droplets with diameters that are smaller than 10 microns.
This also applies to the apparatus that is described in DE 15 21 696 A1, which proposes that an electrical field be built up by connecting parts of a flow cross section to a source of power. Particles in the flow of gas will be prevented from striking metal surfaces or semiconductor surfaces in such a way as to damage them, since the particles are deflected onto a crystalline substance by the electrical field, so that they are retarded very powerfully and, optionally, subjected to an electrochemical reaction. In principle, this process, too, is not suitable for all kinds of small droplets, nor can it be used at any high temperatures, since the current supply lines have to be taken into consideration and because of the fact that--like all other known processes--it is not energy efficient because of the additional power requirement.
Proceeding from this prior art, it is the task of the present invention to describe a process for acting on droplets of liquid contained a flow of gas, which is simple and economical to manufacture, can be used in extremely high temperature ranges, and can be used to act upon droplets of liquid that are smaller than 10 .mu.m. In addition, the present inventions describes an apparatus for carrying out this process.
SUMMARY OF THE INVENTION
The inventive method for affecting liquid droplets in a gas stream is characterized by the steps of flowing a gas
REFERENCES:
patent: 4035164 (1977-07-01), Taylor
patent: 4225323 (1980-09-01), Zarchy et al.
G. Mayer-Schwinning et al; Neuere ... Nebeltropfchen; 1980; pp. 375-383.
H. Salmang et al; Kermik; 1983; pp. 181, 205 unwelt & technik; Apr. 1989; p.44.
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