Plastic and nonmetallic article shaping or treating: processes – Furnace lining formation or repair
Patent
1996-08-23
1998-11-10
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Furnace lining formation or repair
264 35, 266281, F27D 116
Patent
active
058338950
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention concerns a method for partially building and/or repairing at high temperatures industrial facilities comprising a structure made of refractory materials, particularly facilities operating by indirect heating with the aid of flues, such as batteries of coke ovens, according to which use is made of at least one prefabricated element made of refractory materials which is securely attached to said structure by reactive spraying, in of an oxygen-containing carrier gas stream, a mixture of particles capable of reacting exothermically with the oxygen and of particles a preferably refractory material.
BACKGROUND
Since in industrial facilities, as defined above, structures made of refractory materials, which are generally siliceous in nature and made of silica, must always be kept at a temperature above 300.degree. C. in order to prevent their weakening by polymorphic transformation, repair methods at high temperature have long been suggested for their repair. These methods may also be used for partial constructions of such facilities, in particular to modify an existing structure by adding a wall or a burned gas discharge pipe, for example.
Thus, bricks made of vitreous silica, which are characterised by a very low expansion coefficient, have been developed and employed conventionally in order to perform such repairs at high temperature. However, it was found that these repairs were not gas-tight, particularly in the case of batteries of coke ovens.
French patent FR 2541440-B1 (Glaverbel) corresponding to U.S. Pat. No. 4,542,888 (Robyn et al), describes a method of repair at high temperatures using, vitreous silica bricks of this kind and a ceramic welding method for producing the new masonry joints and also full recharging of the structure (GB 1.330.894 and GB 2.110.200 A by Glaverbel). With this method, the vitreous silica bricks preferably comprise a chamfer to facilitate making of the joints.
In another patent using the same ceramic welding method (DE 3643420 Al, Fosbel Europe), the full-thickness repair bricks are paired and then brought to the service temperature prior to filling the space between the old and the new masonry by ceramic welding without, however, fully recharging the zone repaired by ceramic welding.
Generally speaking, although vitreous silica bricks, when they are brought to a high temperature, start upon a slow process of crystallisation (into cristobalite and tridymite), they nonetheless keep their sensitivity to creep when they are subjected to a high-temperature charge.
This effect is observed in coke ovens where repairs of this type in the vicinity of the flues show well-known sagging after being in service for some time.
SUMMARY OF INVENTION
One of the essential aims of the present invention is to provide a new method for overcoming the aforementioned drawbacks jeopardise the reliability of this type of partial building or repair, and to do this in a relatively simple and economically sound manner.
To this end, according to the invention, use is made of a prefabricated element and a mullite-crystallised refractory product with an alumina content of 30-85%, preferably 50-80% alumina, and a mixture of particles capable of reacting exothermically with the oxygen and particles of a refractory material, the composition of which is such as to form in situ a refractory mass which is compatible with the composition of the aforementioned element and structure and which has a thermal expansion coefficient compatible with the coefficient of thermal expansion of the aforementioned element and structure to which said mass must be attached, with account being taken of the stresses to which the latter will be subjected under working conditions.
Advantageously, according to the invention, for the abovementioned spraying, use is made, as particles being capable of reacting exothermically with oxygen, of at least one of the products in the group formed by the following metals : Al, Si, Mg, Ca, Fe, Cr, Zr, Sr, Ba and Ti, and by compounds of these metals cap
REFERENCES:
patent: 2330129 (1943-09-01), Lucas
patent: 4452749 (1984-06-01), Kolvek
patent: 4489022 (1984-12-01), Robyn
patent: 4542888 (1985-09-01), Robyn et al.
patent: 4571318 (1986-02-01), Dudro
patent: 5002910 (1991-03-01), Robyn
patent: 5316268 (1994-05-01), Mantey
Database WPI, Week 9423, Derwent Publications Ltd., London, GB; AN 94-190505 & SU, A, I 806,119 (Belgorod Constr Materials Techn Inst) 20 Mar. 1993.
Derrington James
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