Liquid heaters and vaporizers – Miscellaneous
Reexamination Certificate
2002-09-05
2003-10-14
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Miscellaneous
C165S104160, C110S347000
Reexamination Certificate
active
06631698
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a circulating fluidized bed reactor in accordance with the pending claims.
In more detail, the invention relates to a circulating fluidized bed reactor, comprising a furnace, the lower part of which is provided with fluidizing gas nozzles for fluidizing bed material to be fed to the furnace, said furnace being defined by a substantially vertical and planar first wall; a particle separator for separating bed material from the gas discharged from the reactor; a return duct for bed material separated in the particle separator, arranged in connection with said first wall and having a lower part; a gas seal arranged in the lower part of the return duct, preventing gas from flowing from the furnace to the return duct; and a receiving space defined by a planar water tube wall, which receiving space may be said furnace, whereby the water tube wall is the first wall, or a space in gas flow connection with the furnace.
It is generally known to manufacture a gas seal of a loop seal type, an L-seal or a seal pot for the return duct of a circulating fluidized bed reactor. In all these cases, the return duct of the separator comprises a duct or a section filled with bed material circulating from the particle separator to the furnace, thus preventing furnace gas from flowing via the return duct to the separator. In conventional separator arrangements, the return duct is uncooled and apart from the furnace wall, wherefore, it has also been natural to arrange the gas seal to be an uncooled construction spaced apart from the furnace wall. It is inevitable, however, that joining uncooled structures to a cooled furnace results in temperature differences and thermal stresses reducing the durability and reliability of the equipment.
Published European patent document 0 082 673 discloses an uncooled gas seal vessel integrated in the wall of the lower part of an uncooled furnace. However, the disclosed arrangement is heavy, extending considerably far from the furnace, and, therefore, needs to be thoroughly supported. Furthermore, uncooled structures can easily get broken due to temperature differences, especially during the start-up and shutdown of the reactor.
U.S. Pat. No. 4,951,612 discloses a fluidized bed boiler having four separate gas seals integrated in the cooled outer wall of a cylindrical furnace. The structure of the gas seals is, however, not illustrated in detail.
U.S. Pat. No. 5,269,262 discloses a cylindrical fluidized bed boiler, having a cylindrical structure in the middle thereof, said structure comprising a particle separator, return duct and a multipart, partly cooled gas seal. In the given arrangement, the durability of the furnace wall reduces considerably at the return openings for circulating material and the wide solid wall surfaces between the openings interfere with the even distribution of the material in the furnace.
U.S. Pat. No. 5,281,398 discloses a new kind of a cooled particle separator for a circulating fluidized bed reactor with a cooled return duct integrated in the cooled wall of the furnace. Especially, in this kind of arrangement, it is advantageous to have a cooled gas seal arranged to communicate with the furnace wall. U.S. Pat. No. 5,341,766 discloses a gas seal of a gill seal type meeting said requirements, which gas seal comprises a number of narrow gaps and is integrated directly in the furnace wall. Practice has proved that the usability of a gas seal of a gill seal type is generally good, but in some special situations, its operation capacity may decrease.
U.S. Pat. No. 5,526,775 discloses a gill seal type gas seal between a return duct and the upper part of a heat exchange chamber, which heat exchange chamber is closely connected to a reactor chamber wall. The heat exchange number is in flow communication with the reactor chamber through a vertical discharge channel and one or more openings. U.S. Pat. No. 4,716,856 discloses a heat exchange chamber arranged in a bent wall section of a reactor, where a return duct leads hot material in a fluidized bed in the heat exchange chamber.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an apparatus, in which the above mentioned problems of the prior art have been minimized.
It is especially an object of the present invention to provide a circulating fluidized bed reactor, which has a space-saving gas seal integrated in the planar cooled boiler wall, without reducing the bearing capacity thereof.
Further, an object of the invention is to provide a circulating fluidized bed reactor, which has a light, durable and reliable gas seal.
It is also an object of the present invention to provide a circulating fluidized bed reactor, in which the distribution of the bed material recycled from the gas seal has been improved in the direction of the wall of the receiving space.
In order to achieve these objects, a circulating fluidized bed reactor is provided, the characterizing features of which are discussed in more detail below.
Thus, it is a characteristic of the circulating fluidized bed reactor in accordance with the present invention that a gas seal is arranged in connection with a water tube wall defining a receiving space in such a way that the horizontal cross-sectional width of the lower part of the return duct measured in the direction of the first wall is larger than the depth perpendicular to said width, and the gas seal has a seal structure comprising water tubes joined to each other and being formed by bending water tubes from the water tube wall defining the receiving space.
In a simple case, the lower part of the return duct of the separator is in direct connection with the furnace, whereby, according to the present invention, a gas seal may be arranged in connection with the furnace wall. In some cases, however, the return duct is joined to the furnace via a separate heat exchange chamber in such a way that the heat exchange chamber is in gas flow connection with the furnace and the gas seal is arranged upstream of the heat exchanger. In this case, a gas seal in accordance with the present invention may be formed in connection with the wall of the heat exchange chamber, which is in gas flow connection with the furnace.
It is apparent to those skilled in the art that a gas seal in accordance with the present invention may also be arranged in connection with another comparable cooled wall defining a space in gas flow connection with the lower part of the furnace. The present invention is described below in more detail in connection with the furnace wall, but it is to be understood that the description above also involves gas seals in connection with the walls of other spaces in gas flow connection with the furnace of a circulating fluidized bed boiler.
The gas seal in accordance with the present invention preferably comprises at least one seal channel arranged in the lower end of the return duct, said channel being defined by a front wall and a seal structure, which separates a distinct portion from the bed of circulating material being formed in the lower part of the return duct. The seal channel is preferably in flow connection with the return duct only at the lower part of the seal structure, and only at the upper part of the front wall in flow connection with return means formed in the water tube wall defining the furnace.
When the lower edge of the means joining the seal channel to the furnace, i.e., the return means, is located higher up than the upper edge of the means joining the seal channel to the return duct, the seal channel comprises a center part, which is in a horizontal direction totally surrounded by walls, and a bed of circulating material is formed in the seal channel. The bed surface is substantially flush with the lower edge of the return means. Thus, the bed material in the seal channel prevents gas from flowing from the furnace to the return duct.
In order to make the bed material flow from the return duct through the seal channel to the furnace, the bed material in the seal channel is
Hyppänen Timo
Kauppinen Kari
Fitzpatrick ,Cella, Harper & Scinto
Foster Wheeler Energia Oy
Wilson Gregory
LandOfFree
Circulating fluidized bed reactor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circulating fluidized bed reactor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circulating fluidized bed reactor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3125955