Heat exchange – Intermediate fluent heat exchange material receiving and... – Solid fluent heat exchange material
Reexamination Certificate
1998-08-17
2001-03-27
Atkinson, Christopher (Department: 3743)
Heat exchange
Intermediate fluent heat exchange material receiving and...
Solid fluent heat exchange material
C165S294000, C165S296000, C165S101000, C422S146000
Reexamination Certificate
active
06206088
ABSTRACT:
The present invention relates to a heat exchanger system for a boiler having a circulating fluidized bed.
BACKGROUND OF THE INVENTION
Such a boiler includes, inter alia, the following elements shown diagrammatically in FIG.
1
:
a hearth C for burning the fuel in a circulating fluidized bed of particles, the walls of the hearth comprising vertical pipes in which an emulsion (liquid phase and vapor phase) of water circulates, which emulsion is produced by evaporation of water fed into the bases of said pipes;
a separator member S (in general a cyclone) which, at the top of the hearth, recovers the flue gas and the solid particles ejected from the top of the hearth and directs the flue gas and said particles to respective ones of two distinct ducts;
a first heat exchanger ET
1
often connected to the gas duct S
1
of the separator member S, the first heat exchanger being, for example, an economizer, a vaporizer, a superheater or a resuperheater; and
a dense fluidized bed ET
2
fed with particles from the separator member S, i.e. that is connected firstly to the particles duct S
2
of said separator member and secondly to the bottom of the hearth C (it is also possible to provide a dense fluidized bed ET
2
B that is fed with particles collected in the hearth C, i.e. connected firstly to the extraction duct of the hearth and secondly to the bottom of the hearth), the dense fluidized bed including a second heat exchanger whose inlet is connected to the outlet of the first heat exchanger ET
1
.
In general, the second heat exchanger is made up of a plurality of nests of tubes, each nest comprising a plurality of zigzag tubes arranged in parallel planes that are in general vertical. The coolant fluid, commonly steam, circulates in the nests, and the entire heat exchanger is integrated in a rectangular case.
Usually, the nests are disposed as follows: in succession starting from one wall of the case, a first nest optionally separated from the wall by a space without any zigzag tubes, then a second nest optionally separated from the first nest by a space without any zigzag tubes; the space between the first nest and the second nest may contain a physical separation such as a low wall or a partition; Any additional nests are arranged analogously, so that the last nest is optionally separated by a space without any zigzag tubes from that wall of the case which is opposite from the wall facing the first nest.
The feed duct for feeding the dense fluidized bed ET
2
with particles is thus connected to a wall of the case or to the empty space between the first nest and said wall, the particles being returned to the hearth C via the opposite wall or via an outlet connected to the empty space between the last nest and the opposite wall.
The intense mixing of the particles tends to make the temperature inside the case uniform. However, since the particles leave the case colder than when they were fed into the case, the temperature is not the same everywhere. The tubes situated in the vicinity of the particles inlet receive more heat than those which are close to the outlet.
In addition, when the power of the boiler increases, the power and therefore the size of the heat exchangers must increase. Unfortunately, temperature dispersion is related directly to the size of the rectangular case. Thus, the temperature of the steam produced by the first nest disposed at the particles inlet is greater than the temperature of the last nest disposed at the outlet, which is not desirable.
Furthermore, nests that all withstand the maximum temperature of the case are avoided because that would be a costly solution. Therefore as many types of nest are provided as there are nests in a heat exchanger, each type of nest being dimensioned for an operating temperature which corresponds to its place in the case. Thus, the many advantages of having a single manufacturing line are lost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a heat exchanger system which makes it possible to obtain a substantially uniform temperature at the outlets of all of the nests in the second heat exchanger.
According to the invention, the heat exchanger system includes a first heat exchanger followed by a second heat exchanger disposed in a dense fluidized bed, the second heat exchanger being made up of a plurality of nests of tubes disposed along the path of the particles in suspension in the dense fluidized bed. In addition, with the second heat exchanger being provided with at least two feeds situated on either side of its center, each of the feeds receives a distinct mixture of the input fluid and of the output fluid of the first heat exchanger, so that the temperature of the fluid fed into each of the nests is an increasing function of the distance between it and the inlet via which the particles are fed into the dense fluidized bed.
The differences in the temperatures of the particles in the fluidized bed are thus compensated by the differences in the temperatures of the fluids that feed the various nests.
An effective solution, from a thermal point of view, when the second heat exchanger comprises more than two nests, is to provide each of the nests with its own specific feed.
However, a cheap solution consists in making provision for the feeds of the nests to be connected to a common manifold.
Advantageously, the nests are made up of zigzag tubes disposed in vertical and parallel planes.
In addition, the path of the particles is perpendicular to the planes in which said zigzag tubes are disposed.
A preferred embodiment consists in choosing all of the nests to be identical.
Advantageously, at least one of the mixtures of the input fluid and of the output fluid of the first heat exchanger is formed by means of regulating valves connected to the inlet and to the outlet of the first heat exchanger.
However, it is possible to make provision for at least one of the mixtures of the input fluid and of the output fluid of the first heat exchanger to be formed by means of a regulating valve connected either to the inlet of the first heat exchanger or to the outlet thereof.
REFERENCES:
patent: 2518270 (1950-08-01), Barr
patent: 2852545 (1958-09-01), Jenny
patent: 3013773 (1961-12-01), Campbell et al.
patent: 3156538 (1964-11-01), Schneider
patent: 3814176 (1974-06-01), Seth
patent: 4127161 (1978-11-01), Clyne et al.
patent: 4515205 (1985-05-01), Kawata
patent: 4553502 (1985-11-01), Dreuilhe et al.
patent: 4601328 (1986-07-01), Tasaka et al.
patent: 4738309 (1988-04-01), Schilling
patent: 4945980 (1990-08-01), Umezawa
patent: 5297622 (1994-03-01), Brännström et al.
patent: 5369597 (1994-11-01), Bujak, Jr.
patent: 5855241 (1999-01-01), Aubry
patent: 5954000 (1999-09-01), Panos
patent: 0637569 (1962-03-01), None
patent: 1259787 (1961-03-01), None
patent: 1320230 (1963-05-01), None
patent: 403110390 (1991-05-01), None
Enault Christian
Gauville Pierre
Semedard Jean-Claude
Atkinson Christopher
GEC Alsthom Stein Industrie
Sughrue Mion Zinn Macpeak & Seas, PLLC
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