Liquid heaters and vaporizers – Miscellaneous
Patent
1990-12-12
1992-03-31
Favors, Edward G.
Liquid heaters and vaporizers
Miscellaneous
110245, 110347, 16510416, B09B 300, F22B 100
Patent
active
050998013
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for operating a fluidized bed combustor on coal basis in which comminuted coal is fed into a fluidized bed and burned with the bedding material. The invention furthermore relates to a fluidized bed combustor with a conveyor to feed the coal and with a nozzle bottom on which a fluidized bed consisting of bedding material is positioned during operation.
According to the present state of technology, coal is burned in fluidized bed combustion systems for steam and/or electricity generation (Siemens-Energietechnik 2 (1980), Issue 7, pp. 231-235). This results in two significant advantages. First, the combustion in the fluidized bed occurs at relatively low temperatures so that in comparison with known combustions using dry or even wet ash relatively little nitrogen oxide is formed Second, the combustion in the fluidized bed places relatively low requirements on the used coal, i.e. even a relatively roughly ground coal with high ash content may be burned without problems. "Ash" here means the incombustible substances contained in the coal, such as sand, clay, salts, metal compounds, etc.
When operating a fluidized bed combustor, coal is used which is ground to a grain size specific to the fluidized bed. It is fed to the fluidized bed, i.e. in most cases via the free space located above the fluidized bed. It is then mixed homogeneously with the bedding material. This bedding material consists both of sand and ash particles which were added to the fluidized bed with the coal, and of migrating coal particles.
A disadvantage here is that, in particular in the case of discontinuous ash removal, the fine-particle bedding material in the fluidized bed is continuously reduced because of flue-dust removal with the flue gas. The rough grain content increases steadily and settles during longer operation on the nozzle bottom of the fluidized bed. This again results in the obstruction of individual nozzles which feed the carrier air. As a consequence, locally differing zones with little or no air throughput at all are generated, as well as zones with increased air throughput. This significantly impairs the temperature homogeneity of the fluidized bed which is required for the removal of the generated heat, e.g. via a heat exchange system. In addition, temperature streaks form above the areas with increased air throughput in the free space of the fluidized bed combustor. These are narrow, long-stretched structures which are above the softening point of the ash. This results in slagging of the free space, e.g. in the form of nests. These slaggings may make it necessary to take the fluidized bed combustor out of operation. It is therefore important to balance the temperature distribution as evenly as possible over the entire fluidized, bed so that no slag deposits may form.
SUMMARY OF THE INVENTION
The invention has the task of providing a process of the above described type which makes it possible to operate a coal-based fluidized bed combustor without problems even over a longer period. In addition, a fluidized bed combustor of the above described type shall be provided which will make it possible to avoid the formation of slag over a longer period.
According to the invention the first task is solved in that part of the bedding material is removed from the bottom region of the fluidized bed continuously or discontinuously, is then preferably cooled, subsequently processed to a predetermined maximum grain size which is specific to the fluidized bed, and is then recycled to the fluidized bed.
According to the invention the second task is solved by a system characterized by which is located in the bottom region of the fluidized bed; preferably located behind the removal mechanism; maximum grain size specific to the fluidized bed; the fluidized bed.
The invented suggestion attempts to no longer adjust the optimum grain size range of the bedding material of a fluidized bed combustor by way of grinding the added fresh coal, but rather to achieve this through (prefer
REFERENCES:
patent: 4111158 (1978-09-01), Reh et al.
patent: 4227488 (1980-10-01), Stewart et al.
patent: 4421036 (1983-12-01), Brannstrom et al.
patent: 4505209 (1985-03-01), Strohmeyer, Jr.
patent: 4776288 (1988-10-01), Beisswenger et al.
patent: 4815418 (1989-03-01), Maeda et al.
Kelly et al., "Industrial Application of Fluidized-Bed Cogeneration System", Chemical Engineering Process, 80:1, 35-40 (U.S.A. Jun. 1984).
Petzel Hans-Karl
Scholl Gerhard
Stadie Lothar
Creighton Wray James
Favors Edward G.
Saarbergwerke Aktiengesellschaft
Siemens Aktiengesellschaft
LandOfFree
Process for operating a coal-based fluidized bed combustor and f does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for operating a coal-based fluidized bed combustor and f, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for operating a coal-based fluidized bed combustor and f will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2251617