Patent Application
20100139492
The present invention relates to cyclone units for use in separating contaminants from flue gases.
More specifically, the present invention refers to cyclone units for use in separating gaseous contaminants such as sulfur dioxide, NOx, CO2 and solid contaminants from flue gases and to processes utilizing the same.
The present specification inter alia is directed to a modification of and improvement on the cyclone separator described and claimed in Israel Patent No. 120,907 and corresponding European patent 971,781.
As described in EP971781, cyclone separators are widely used in industry for dry and wet cleaning of polluted air and can be generally divided into two groups.
The first group is based on imparting vortical motion to the fluid entering the cleaning vessel and separation of the solid particles therefrom by virtue of centrifugal force. This group combines mechanical collectors, e.g., ordinary cyclones, multi cyclones and rotary dust collectors.
The second group is based on filtration of the air or on induced precipitation or gravitational settling of a solid particulate, without, however, involving the fluid within the cleaning vessel into the vortical movement. The industrial equipment relevant to this group includes bag filters and electrostatic precipitators.
The performance of existing particle collectors is evaluated according to the ultimate particle size of the solid particulate which can be separated by a collector.
The mechanical cyclone separators have many advantages; they are versatile, low-cost devices that operate in a continuous mode without the necessity of frequent maintenance measures. These devices have been successfully used for a very long time (as early as 1886), as stand-alone units or in combination with other types of separators.
The main factor affecting the separation of solid contaminants from flue gases in cyclone separators is the velocity of the gaseous phase or its acceleration which is a function of the velocity. Two main forces affect a particle moving in a rotating flow. These forces are a centrifugal force and a drag force along the line of flow. The centrifugal force, Fc, is proportional to the particle mass mp and to the square of the tangential velocity, Vt, of the particle or of the spinning gas which are almost the same and is inversely proportional to the radius of curvature, r, of the particle trajectory according to the formula:
F
c
=m
p
V
t
2
/r (1)
The velocity of the spinning gas flow is assumed to have only a tangential component, and this type of flow is usually of the form:
Vtrn=const (2)
Typical velocities in high efficiency cyclones are about 15-20 m/sec.
These velocities were found to be insufficient for removing very small sizes of dust of less than about 10-20 microns.
Several patents, i.e., SU 1468609; SU 975099; and DE650640 tried to improve the separation of fine dust by cyclone separators, however it should be emphasized that in spite of this, the problems of cost effectiveness and the efficient separation of fine dust, have not been solved.
In EP000971781B1 there is taught a device which dramatically improves the separation of fine dust by cyclone separators, which improvement is achieved by incorporating very effective swirling means of intense vortical motion, said vortical motion being characterized by a linear velocity of the gaseous stream of about 60-100 m/sec, and preferably of about 60-70 m/sec.
Surprisingly, the equipment described in EP000971781B1 has now been found to be very effective even in wet separation, i.e., when adding a liquid to the cyclone separator, for removing fine dust and especially for separating gaseous contaminants such as sulfur dioxide, NOx, and CO2 from a gaseous stream such as flue gas.
It is important to note that it was not self evident that the cyclone separators described in EP 0971781B1 for removal of particulate matter from air and other gases would be effective for the removal of gaseous contaminants, especially sulfur dioxide, from flue gases. In the case of particle removal in a cyclone unit the main objective or challenge is to achieve good separation between the gas phase and the particles by means of physical dynamics. In other words, the objective taught and achieved in said patent was to maximize the difference between the motions of the gas and those of the particles inside the cyclone unit and thereby to achieve separation between these two elements. In contradistinction, in the case of removal of gaseous contaminants, especially sulfur dioxide from flue gases, the main objective is to achieve an effective mixing between the liquid and the gaseous phases, and thereby to achieve an efficient contact between an active element, such as an alkaline compound in the aqueous phase and the sulfur dioxide in the gaseous phase, in order to have higher kinetics.
However, despite the improvements obtainable by using the cyclone separator as described in EP 0971781 B1 it has been found that the contact between the liquid and the gaseous streams is still ineffective even when using advanced nozzles.
In addition, to the need in a major improvement in the contact between the incoming liquid and gaseous streams, there is a need for a good separation between these two streams after the contact, in order not to have high content of liquid droplets in the outgoing treated gaseous streams.
Therefore, the problem of producing cyclone units for use in effective wet separation of fine particles and especially of gaseous contaminants has not yet been solved by the prior art, and there is still a need for a new and improved device which will ensure efficient and economical mixing and separation between the two streams, i.e., for wet removal separation of solid and gaseous contaminants such as sulfur dioxide, NOx, and CO2 from flue gases.
Thus the object of the present invention is to provide for a new and improved cyclone unit which will sufficiently reduce and/or overcome the above mentioned drawbacks.
In particular, the main object of the present invention is to provide a new and improved cyclone unit suitable for efficient wet separation of fine particles and especially of gaseous contaminants.
A still further object of the present invention is to provide for a new and improved cyclone unit producing very efficient contact between the gaseous and the liquid incoming streams. Thus, this very efficient contact improves the kinetics of the reaction between the substrates in both phases. As a result, environmental pollution declines by using a reduced amount of chemicals for absorbing the above mentioned contaminants.
A still further object of the present invention is to provide for a new and improved cyclone unit producing very efficient separation between the treated gaseous and liquid outgoing streams after the contact. Thus, this very efficient separation reduces the content of liquid droplets in the outgoing treated gaseous streams.
One of the main challenges in wet scrubbing is to provide an effective contact between the liquid droplets and the gaseous stream. When using known-in-the-art cyclone separators, even by using advanced nozzles, large amounts of the liquid droplets are deposited on the inner walls of the cyclone separator and create a liquid layer that is removed from the surface by gas shear forces and droplets bigger than those produced by the nozzles are generated. The bigger droplets are less effective in removing contaminants from flue gases. Thus, chemical results are far from equilibrium.
The present invention proposes to introduce the liquid stream into an area in which the velocity of the gaseous stream is very high, thus the liquid droplets immediately enter the inner part of the cyclone separator and only a very small proportion of them will deposit on its inner walls or leave the system without contacting the gaseous stream.
This invention is particularly important for cyclone separators, having very effective swirling means which provide for intense vortical motion, being defined by a linear velocity of about 60-100 m/sec compared with known-in-the-art cyclone separators that having linear velocity of about 15-20 m/sec.
By introducing the liquid stream into an area where the velocity of the gaseous stream is very high, larger amounts of the liquid droplets enter the inner part of the cyclone separator. Thus this system is characterized by a contact between the liquid droplets and the gaseous stream which is much longer and thus extremely effective.
Another important challenge in wet scrubbing is to provide an effective separation between the treated gaseous and liquid outgoing streams after the contact.
In order to achieve this objective the present invention provides an improved cyclone unit comprising a kind of a barrier tool and/or, slit openings inside said cyclone, enabling said treated liquid to exit said unit in a predetermined direction while hindering said treated gaseous stream from flowing with it and instead directing said gaseous stream in a different direction.
Thus the present invention provides a cyclone unit for the removal of contaminants from flue gases by combination of a gaseous stream with an aqueous stream, comprising a housing defined by a cylindrical peripheral wall, by upper and lower extremities, and by a core element, said housing having a longitudinal axis and being provided with at least one inlet opening for receiving a gaseous stream and a plurality of inlet openings for receiving an aqueous stream there into, said cyclone unit further comprising at least one swirling means concentrically positioned and mounted within said housing coaxially with said longitudinal axis so as to provide a first annular space between an inner surface of the housing peripheral wall and the outer facing surfaces of said swirling means and to provide a second inner annular space between inwardly facing surfaces of the swirling means and said core element, said swirling means incorporating a plurality of slit-like elongated openings extending substantially tangentially with respect to said inner annular space so as to enable angular passage from said first annular space towards said second inner annular space, wherein said cyclone unit is characterized in that said openings for receiving said aqueous stream are located in said upper extremity, and are positioned to inject at least most of said aqueous stream into said passages. In preferred embodiments of the present invention said plurality of openings are associated with means for injecting a plurality of aqueous streams into a plurality of passages.
Preferably, said aqueous streams are injected by nozzles into said passages.
In some preferred embodiments of the present invention said swirling means are formed with a plurality of vanes, said vanes being arranged regularly along a circular path, tangentially with respect thereto and said passages are formed by open spaces between adjacent vanes.
In other preferred embodiments said swirling means is formed as a cylindrical ring provided with a plurality of spaced apart slit-like elongated openings forming said passages
In said other preferred embodiments, preferably said passages are formed by drilling said swirling means.
In especially preferred embodiments of the present invention there is provided a cyclone unit wherein the velocity of said gaseous stream inside said cyclone unit is between 20 m/sec and 120 m/sec., and preferably between 60 m/sec and 100 m/sec.
In a further aspect of the present invention said housing is formed as a hollow truncated cone, having a large base and a spaced apart small base, the large base thereof being in communication with the lower extremity of said housing, a pipe means being placed within said housing coaxially with the longitudinal axis thereof and constituting said core means wherein an uppermost extremity of the pipe means is located outside of the housing, and a lowermost extremity of said pipe means is located within the housing.
In a preferred embodiment of this aspect, there is provided a plate like tool which is connected inside said hollow truncated cone above said small base of said hollow truncated cone, coaxially with the longitudinal axis of said housing.
In another preferred embodiment of said aspect, said hollow truncated cone contains at least one longitudinal slit-like opening.
In an especially preferred embodiments of this aspect of the invention, said hollow truncated cone is connected to an external envelope means which is partially coating said hollow truncated cone yet leaving a space between them.
While the invention will now be described in connection with certain preferred embodiments in the following figures so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended Claims. Thus, the following figures which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of formulation procedures as well as of the principles and conceptual aspects of the invention.
In the drawings:
Referring now to
Referring now to
Said cyclone unit is characterized in that said openings (10) for receiving said aqueous stream are located in said upper extremity (4), and are positioned to inject at least most of said aqueous stream into said passages (37).
While not shown, there could be provided a plurality of openings of smaller diameter adjacent said passages in order to assure smaller droplets and openings need not be provided adjacent all the passages.
Referring now to
Said openings (10) are preferably associated with nozzles (not shown) which are positioned to inject said aqueous streams into said passageways.
In especially preferred embodiments, said unit is provided with a multiplicity of openings (10) each opening positioned to inject an aqueous stream into an adjacently positioned passageway for intermixing with a gaseous stream flowing there through.
Referring to
Referring to
As a result said treated liquid is exiting said hollow truncated cone through its said small base (16) and in addition, through at least one of longitudinal slit-like openings (44). The treated liquid that exits through at least one longitudinal slit-like opening enters said inner space (48) between said external envelope means (46) and the external wall (52) of said hollow truncated cone, combining with the treated liquid that has exited through said small base (16).
Referring to
As will be noted, referring to
Thus as seen in
Furthermore as will be seen in
In
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 178234 | Sep 2006 | IL | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IL2007/001080 | 9/2/2007 | WO | 00 | 12/2/2009 |
