Furnaces – Process
Reexamination Certificate
1999-09-08
2001-04-10
Ferensic, Denise L. (Department: 3749)
Furnaces
Process
C110S298000, C110S278000, C110S268000, C110S281000, C110S327000, C126S174000, C126S175000
Reexamination Certificate
active
06213031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of cooling a grate for a furnace and to a grate for a furnace. Grates of the generic type are used in furnaces, e.g. of refuse-incineration plants. The cooling is effected for the purpose of increasing their useful life by reducing the scaling of the grate material under the action of the combustion heat.
2. Discussion of Background
Thus it is known, for instance, from DE-A-44 09 992 to cool a grate bar by water which is directed through a passage which is run in the longitudinal direction from the rear end of the grate bar up to the tip and back through the grate bar. The effect of this type of cooling is restricted by the convective heat transfer and by the heat-absorption capacity of the water, as results from its thermal capacity and the temperature range available. The temperature of the cooling water must be kept below the boiling point, a factor which requires a relatively high velocity of flow to be maintained in the entire volume. The manufacture of the grate bars is thus inevitably relatively complicated and the cooling arrangement which maintains the cooling-water circulation is costly.
EP-B-0 621 449 discloses a similar design of a grate, in which, however, the grate bars of one row are in each case replaced by a continuous grate plate. Here, sufficient cooling with relatively low heating of the cooling water is ensured by large cross sections of flow, but this again requires a large cooling-water flow rate, which in turn can only be maintained by an expensive cooling arrangement.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to specify an effective method of cooling a grate as well as a grate which is especially suitable for the cooling method according to the invention.
In the method according to the invention, the cooling liquid fed to the grate is converted essentially completely into vapor upon contact with the grate, as a result of which it can draw off very large quantities of heat at a low consumption, since both the heat transfer is substantially improved and the heat quantity absorbed during the vaporization is far greater than could be absorbed by mere heating in the liquid state of aggregation. The vapor produced need not be recirculated, but may flow off, for instance, into the region situated below the grate. This permits the use of grates and cooling arrangements of very simple construction. Nonetheless, the heat absorbed by the vapor may be at least partly recovered in the course of the heat recovery from the flue gas.
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Kunzli Max
Millard John
Serck-Hanssen Peter
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Ferensic Denise L.
Rinehart K. B.
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