Gas separation: processes – Deflecting – Centrifugal force
Reexamination Certificate
2003-02-06
2004-10-12
Chiesa, Richard L. (Department: 1724)
Gas separation: processes
Deflecting
Centrifugal force
C055S346000, C055S349000, C055S434100, C055S434400, C055S459100, C422S146000, C422S147000
Reexamination Certificate
active
06802890
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for separating particles from hot gases.
Thus, the invention relates to a centrifugal separator assembly and a method of separating particles in a centrifugal separator assembly attached to a fluidized bed reactor, for separating solid particles from gas exhausted from the reaction chamber of the fluidized bed reactor, which separator assembly comprises a vortex chamber, which is in a horizontal direction, defined by vertically-extending outer walls formed of planar water tube panels, the inside of the walls being provided with a refractory lining and defining a gas space in the vortex chamber, in which at least one vertical gas vortex is established, at least one inlet for introducing gas into the gas space from the reaction chamber, at least one outlet for discharging purified gas from the gas space, and at least one outlet for discharging separated solid particles from the gas space.
The present invention relates especially to centrifugal separators utilized for separating solid particles from the process and product gases of fluidized bed reactors, especially, circulating fluidized bed reactors used for combustion or gasification of carbonaceous or other fuels.
It is generally known how the inlet and outlet ducts of a centrifugal separator should be arranged so as to make the flue gas entering through the inlet duct produce a vertical gas vortex. Conventional centrifugal separator assemblies include one or more centrifugal separators, i.e., cyclones, defined by an outer wall having a shape of a right circular cylinder, and a conical bottom. The cyclones of a fluidized bed reactor are traditionally manufactured as uncooled structures provided with a refractory lining, though the walls of the fluidized bed reactor itself are generally formed of cooled water tube panels. When connecting an uncooled particle separator to a cooled reaction chamber, it is necessary to consider varying thermal motion and use such arrangements that enable relative motion, even if the arrangements are expensive and susceptible to damage. Cylindrical cyclones have also been manufactured as structures formed of wafer tubes, whereby the temperature difference between the cyclone and the cooled reactor chamber remains small. However, to provide a water tube wall construction of a cylindrical form and to connect it to the surrounding constructions requires a lot of manual labor and is, therefore, expensive.
U.S. Pat. No. 4,880,450, for example, discloses a method by which a cooled cylindrical cyclone can be connected to the furnace of a fluidized bed boiler and to the heat recovery section thereof. The cylindrical upper section of the cyclone comprises water or steam tubes attached to each other, the inner surface of which is covered with insulative material. The separator according to this patent can be connected to a cooled environment without separate elements enabling relative motion, but the construction requires a lot of effort and is, therefore, expensive.
U.S. Pat. No. 5,281,398 discloses an arrangement in which particles are separated from hot gases in a centrifugal separator, the vortex chamber of which is composed of planar water tube panels. Thus, the gas space of the vortex chamber is polygonal in horizontal cross section, preferably quadrate or rectangular. This kind of separator is inexpensive to manufacture and can easily be connected to a reactor furnace formed of similar wall panels, whereby a compact unit is established. Traditionally, the gas volume of a separator vortex chamber is cylindrical, as the cylindrical space interferes with maintenance of the gas vortex velocity to as small a degree as possible. The invention disclosed in U.S. Pat. No. 5,281,398 is, however, based on the fact that a gas vortex can also be established in a space polygonal in cross section. In a cylindrical separator, the particles separated by centrifugal forces are driven to the vortex circumference and flow downwardly along the inner walls of the vortex chamber. Appropriate operation of a polygonal separator is based on the fact that the corners of the gas space enhance the separation of the particles and serve as suitable flow-down areas for the separated particles.
U.S. Pat. No. 4,615,715 discloses an assembly in which a cylindrical cyclone manufactured of abrasion-resistant material is disposed inside a cooled enclosure which is quadrate in cross section. In this arrangement, the shape of the gas space is ideal for maintaining the vortex velocity. Nevertheless, the manufacture of the water tube panels for the separator enclosure can be automated, and the separator can straightforwardly be connected to a cooled environment. In the arrangement according to this patent, the relatively large space between the annular inner space and the quadrate outer enclosure is filled with suitable material. The problem with this material is that it serves as a heat insulator and increases the weight and heat capacity of the separator. Thus, it increases the temperature of the separator's inner wall during operation and adds to its thermal inertia. Large and rapid changes of temperature can cause damage to the material in the intermediate space, which adds to the maintenance and repair costs. Therefore, the changes of temperature in the separator need to be sufficiently slow, which fact is to be considered when changing the capacity of a plant and especially during start-ups and shut-downs. Further, the innermost surface of the material has to be very abrasion-resistant and, therefore, the filling of the intermediate space is done by a special multi-layer technique. This however, adds to the construction costs and makes the separator structure complicated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved centrifugal separator assembly and a method of separating particles from hot gases.
In particular, it is an object of the present invention to provide a compact centrifugal separator assembly and a method of separating particles, which assembly is less expensive to manufacture and the degree of particle separation of which method is high.
Moreover, it is an object of the present invention to provide a method of separating particles and a centrifugal separator apparatus with minor need for maintenance, which apparatus can, preferably, be connected to a cooled reaction chamber.
In order to achieve these and other objects, a centrifugal separator assembly, as set forth in the claims, is provided.
Thus, it is characteristic of the centrifugal separator assembly according to the present invention that the vertically-extending outer walls of the vortex chamber form at least one corner, the angle between the sides of which exceeds ninety degrees, the corner being rounded by a refractory lining on the inside of the outer walls.
In order to achieve the objects, a method of separating particles, as set forth in the claims, is also provided.
Thus, in one aspect according to the present invention, the gas exhausted from the reaction chamber of a fluidized bed reactor is, in the vortex chamber, brought to hit at least one corner rounded by a refractory lining on the inside of the outer walls, the angle between the vertically-extending outer walls of which corner exceeds ninety degrees.
The arrangement according to the present invention combines the advantages of planar cooling surfaces and a rounded gas space and avoids the disadvantages of thick refractory layers by providing the outer wall of the vortex chamber with a polygonal horizontal cross section, in which at least some of the angles are more than ninety degrees.
Separators according to U.S. Pat. No. 5,281,398, in which the gas space of the vortex chamber is a polygon in horizontal cross section, operate flawlessly in normal operating conditions. It has been discovered, however, that a particularly advantageous construction can be provided for new generation gas separators by using gas velocities and separator design standards that differ from
Chiesa Richard L.
Fitzpatrick ,Cella, Harper & Scinto
Foster Wheeler Energia Oy
LandOfFree
Method and apparatus for separating particles from hot gases does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for separating particles from hot gases, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for separating particles from hot gases will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3330279