Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1989-03-17
1990-06-26
Nozick, Bernard
Gas separation
Means within gas stream for conducting concentrate to collector
55 95, 55255, 55256, 552574, B01D 4700
Patent
active
049368788
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for cleansing gases from solid, liquid and/or gaseous impurities. The invention also relates to apparatus for carrying out the method.
The invention is particularly intended for use as a passive emergency system capable of being activated in the event of an accident or in the event of interruptions in operations in, for example, nuclear power plants, chemical industries or other industries where such circumstances may result in the release of airborne contaminants dangerous to the health The invention, however, can also be applied under normal operating conditions, for instance, in a plant or manufacturing process.
The invention, both with regard to function and construction, has been developed in response to the very special requirements placed on an emergency safety system. Such a system shall be capable of standing in permanent readiness for a period of at least ten years, and must be capable of instant activation to full effect in the event of an emergency. It is highly beneficial if the emergency system is able to function automatically and independently, in the absence of operating personnel and power input.
Very specific requirements are placed on emergency systems for nuclear power stations and intended for extracting radioactive particles and gases from substances that are released as a result of a breakdown in operation. The following conditions are examples of those conditions which can be required of such an emergency system:
no electric power supply
no active control and monitoring by operating personnel
long endurance in the absence of power input
total endurance for several days
capable of absorbing gas and extracting dust particles
high degree of efficiency within widely varying rates of flow.
These requirements are fulfilled with a safety system that comprises a very large stone-bed filter. In this case, dust is extracted through physical phenomenon, sedimentation and diffusion, wherewith particles but have a size in the order of 0.5-10 .mu.m are only slightly affected. Such a filter is consequently relatively large and considerably expensive. Despite this, such filters have poor extraction efficiency with regard to the very finest particles, particularly in regard of particles beneath 0.5 micron. The filter also has poor efficiency with regard to gas separation, the gas in this case being adsorbed on the stone material
Distinct from such known filters, the present invention proposes the use of wet cleansing apparatus, using a liquid into which the contaminated gas is guided to a location beneath the surface of said liquid. The separator or filter will then function as a water seal which when no overpressure prevails in the space or chamber connected to the gas cleanser, holds said space isolated from the surrounding atmosphere.
In order for wet cleansing apparatus to be efficient, it is necessary for the liquid and gas to be thoroughly mixed together in the apparatus. Thus, the cleansing liquid must be dispersed throughout the gas in the form of fine liquid droplets and/or the gas must be passed through the liquid in the form of small gas bubbles. Furthermore, the cleansing efficiency of wet cleansing apparatus into which the gas is introduced beneath the surface of the liquid bath is highly dependent on the rate of flow, and a good cleansing effect is only obtained within a relatively narrow flow range. This presents particular problems in some cases, since an emergency system must be capable of dealing with flow rates of varying magnitudes, without needing to be monitored or controlled actively. There is proposed in DE-PS- 228 733 a cleansing system in which the incoming gas flow is divided into a plurality of part flows which are directed in fine jets against impingement or striking surfaces. This system, however, has the aforesaid drawback of having low efficiency at small rates of flow, since in this latter case the gas bubbles through the liquid in relatively large bubbles and is relatively unaffected.
US-A-3 216 181 (c.f.FIG. 4), US-A 3 520
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patent: 404621 (1889-06-01), Hibbert
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Gustavsson Lennart
Johansson Lars-Erik
Lindau Leif
Flakt AB
Nozick Bernard
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