RESTORATION OF TECHNICAL CONDITION OF COKE OVEN BATTERIES BY HOT REPAIRS OF REFRACTORY BRICKWORK
Hot heating walls rebricking to the various depth down to complete rebricking has been recently recognized as the most effective method of repair.
СJSC "OKOS" introduces both abroad and in Russia restoring technical condition of coke oven batteries of any production capacity by means of hot repair of refractory brickwork and equipment.
Advantages of the given technology are as follows:
- Extend the life of coke oven batteries to 7-12 years, subject to the rules of technical operation of coke ovens.
- Coke Oven Battery is not taken for repair in full scope, as it happens during cold repair, which lasts about 12 months. Only separate worn out chambers, which require repair are taken for repair whereas other chambers of the battery provide coke production.
- During the repair of such coke ovens, the worn out parts of anchorage (flash plates, door frames, parts of anchor columns, tie-rods) and refractory brickwork are replaced. Technical condition of parts of refractory brickwork and anchorage not subject to replacement does not deteriorate in the process.
- Due to the reduction in consumption of refractories, materials and equipment at hot repair of coke oven batteries according to the hot repair technology of LLC “OKOS”, in comparison to cold repair, great economic efficiency is achieved.
Depending on the scope of repair and standard sizes of coke oven batteries the cost of hot repair makes 30-40% of the cost of similar cold repair.
Safety of the adjacent walls is achieved due to (750 - 850оС) temperature maintenance in heating walls during the repair, thus excluding modification transformations of silica.
The basic problem in using of silica refractories in hot repairs is maintenance of durability and gas tightness of a continuous vertical joint between the old and new brickwork portions due to deformations at heating, caused by significant thermal linear expansion of silica 1,2-1,4%.
Due to this, repairs of coke oven batteries’ brickwork are carried out in some countries using modules of fused quartz, having small thermal expansion coefficient 0,2-0,3% - the so-called non-expanding refractories (modules).
So, «Vanocur Refractories» U.S. offers rebricking of the end verticals of heating wall by non-expanding refractory modules of its own manufacture (MCB-27) within ten 10-hour working days.
To reduce expenses on repairs and increase service life of coke oven batteries a hot repair method has been developed combining the processes of laying and heating up of laid silica.
In this case:
- ordinary shaped silica brick and straight brick is used;
- laying is executed with design bricks bonding at each course, including the joint of old and new parts;
- partial heating up and expansion of brickwork layers takes place continuously owing to heat conductivity and radiant heat exchange from the adjacent heated walls and the rest part of the repaired walls;
- final heating up of the repaired wall is carried out within 3-5 days vs. 8-10 days;
- residual growth of brickwork (at final heating up to working temperatures after repair) is insignificant, that provides durability and gas tightness of the executed new brickwork.
The best results of realization of hot repairs combining the processes of brickwork laying and partial heating up of laid brickwork are achieved under the following conditions:
- silica brick of high quality is used for repair;
- repair is carried out at one wall simultaneously;
- the depth of rebricking should not be less than 4 verticals, including silica and fireclay vertical flues roofing and ovens roofing zones;
- during repair of heating wall the oven’s sole bricks and damaged bricks of the lower courses of the end part of heating wall should be replaced (as well as in coking chamber).
Repair technology allows keeping safe refractory brickwork of adjacent heating walls and regenerators, execution of the accelerated heating up of the repaired wall and developing them up to the designed production capacity.
Engineering principles on heat insulation and ventilation of working zone allow carrying out repair all-year-round in any climatic conditions.
Complete rebricking of heating wall, including heating up, is carried out within the period not exceeding 25 days.
Two adjacent walls can be rebricked simultaneously, which significantly reduces the overall repair time.
Efficiency of this method of repair was often confirmed during the repairs carried out by LLC “OKOS” in Russia (coke oven batteries with chambers up to 7 meters in height) and at steel plants of India, Czechia and China.
The international application under the PCT (№ PCT/RU2010/000337) for coke oven hot repair method has been completed.