Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Reexamination Certificate
2000-08-31
2001-09-11
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
C162S031000, C422S185000, C048S1970FM
Reexamination Certificate
active
06287415
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an arrangement in a soda recovery boiler, comprising in the lower part of the recovery boiler at least one melt chute for discharging molten salt from the recovery boiler during operation, the chute being provided with a discharge opening connected with the furnace of the recovery boiler.
BACKGROUND OF THE INVENTION
For checking and/or repairing the bottom of a soda recovery boiler, its bottom has to be emptied of the molten salt existing therein. As far as present soda recovery boilers are concerned, this is done by melting a pile of material accumulated at the bottom until the surface of the melt lies on the same level as the normal melt chutes of the soda recovery boiler. After this, plenty of soda melt still remains at the bottom of the recovery boiler, which melt solidifies when it is cooled and must be removed by dissolving it in water or by crushing mechanically. The solution has to be pumped out and the crush has to be moved away from the bottom of the boiler by some method. The diluted solution and the crush leaves the circulation of chemicals and the chemicals are not recovered. This takes time and is difficult and, additionally, causes corrosion at the bottom of the soda recovery boiler. As to the present soda recovery boiler, there is no other practical alternative to empty the bottom of the boiler at the moment. For that reason, a remarkably long time has to be reserved for emptying at a maintenance stop.
SUMMARY OF THE INVENTION
The object of this invention is to provide a solution by which a soda recovery boiler could be emptied in a simpler and easier way and more rapidly than according to the known solutions. The arrangement of the invention is characterized in that the arrangement comprises at least one separate outlet connected with the furnace of the recovery boiler and positioned below the discharge opening of the normal melt chute in the height direction of the recovery boiler in such a way that, for emptying the recovery boiler, the molten salt and/or a washing liquid can be removed through the outlet to a level below the lower edge of the discharge opening of the normal melt chute.
The essential idea of the invention is that a separate outlet is arranged in the recovery boiler, the outlet being situated substantially lower down than the normal discharge openings of the melt chute of the recovery boiler. During normal operation of the soda recovery boiler, such an outlet would be completely closed and would not be opened until for the time of a stop of the recovery boiler, when the bottom of the recovery boiler shall be emptied for checking and/or repair, for instance. The essential idea of a preferred embodiment of the invention is that the outlet is provided with a separate outlet chute through which the molten salt coming from the outlet and the previous washing liquid can be led forward. The essential idea of a second preferred embodiment is that the outlet chute has a structure essentially similar to the structure of the normal melt chutes. In accordance with a third preferred embodiment, the outlet chute is for instance water-cooled and connected to the same cooling system as the other melt chutes. An advantage of the invention is that, by means of a simple and advantageous melt chute, preferably found to be good and functional also in practice and particularly intended for discharge, it is possible to empty the bottom of the recovery boiler as effectively as possible without having to dissolve and pump a cooled and solidified and thick salt layer in a laborious manner. Another advantage of the invention is that such an outlet chute is easy to mount in soda recovery boilers already in use. In addition, the molten salt coming through the outlet chute can easily be led to dissolution and recovery of chemicals.
REFERENCES:
patent: 4708324 (1987-11-01), Goodspeed
patent: 5635095 (1997-06-01), Kleinfeld
patent: 5800773 (1998-09-01), Beveridge et al.
patent: 5976319 (1999-11-01), Paju et al.
patent: WO 99/27180 (1999-06-01), None
Hakulinen Aki
Makela Jaakko
Ruohola Tuomo
Salmi Kalle
Kvaerner Pulping Oy
Nguyen Dean T.
Rockey Milnamow & Katz Ltd.
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