ENHANCEMENT OF SERVICE LIFE OF BY-PRODUCT-COKING INDUSTRY UNITS
1. FULL WALL REBUILDING OF COKE OVENS HEATING WALLS; PARTIAL REBRICKING OF HEATING WALLS TO VARIOUS DEPTHS
The technology of this repair allows:
- to keep safe the refractory brickwork of heating walls adjacent to the repaired ones by keeping 850-950 °С temperature during the repairs, thus preventing silicon oxide structural transformations in the silica bricks;
- to execute accelerated heating up and commissioning of heating walls after repair;
- to minimize reduction of the production volume.
- Engineering solutions for thermal insulation and ventilation of the working area allow carrying out the repairs all year round in any climatic conditions.
Main advantages:
- Extending service life of coke oven batteries up to 7-12 years, provided the coke oven technical operation rules are abided by;
- Prompt re-commissioning of the rebuilt heating walls;
- Achieving high economic impact due to minimal loss of coke production.
In such case:
a) Ordinary silica refractory brick is used;
b) Laying is executed with design bricks bonding at each course including the junction of old and new sections of brickwork;
c) Partial heating up and expansion of brickwork takes place continuously owing to heat conductivity and radiant heat exchange from the adjacent heated walls and the rest part of the repaired wall;
d) Final warming up of the repaired wall up to the operating temperature is carried out within 3-5 days;
e) A minor residual growth of brickwork to reach the operating temperature value ensures durability and gas tightness of the brickwork.
2. REPAIR OF THE CORBEL AREA AND REGENERATORS ZONE INCLUDING REPLACEMENT / CLEANING OF CHECKER BRICKS;
Cracks or brickwork joints gaps often occur in ovens which have been in operation for a long-time, in the brickwork of a gun flue zone, gas riser ducts as well as in the regenerators' walls separating the flows. Checker brickwork fusing occurs during heating of ovens lacking the air or those with major cross-flows of crude gas from coking chambers into the heating system; whereas blast furnace dust deposition on the checker bricks surfaces causes an increased resistance of checker brickwork when heating the ovens with blast furnace gas.
Repair of the corbel area and regenerator zone with replacement / cleaning of checker brickwork allows to:
- Restore normal thermal mode of COB operation (i.e., achieving uniformity of temperature distribution throughout the heating system of heating walls along the entire battery length);
- Restore normal hydraulic mode of COB operation, (i.e., maintaining values of gas pressure in the oven’s sole and suction in various parts of the heating system as prescribed by the production procedures).
3. PREVENTIVE REPAIR OF COKE OVEN BATTERY REFRACTORY BRICKWORK
3.1. REPAIR OF HEATING WALLS DAMAGED PORTIONS BY:
- CERAMIC WELDING
Ceramic welding is a method to restore refractory lining of industrial ovens without shutting them down and cooling by creation of a high-temperature synthesis of refractory material on damaged hot surface of refractory brickwork, resulting in formation of a built-up ceramic layer. This technique is based on applying a ceramic powder (a mixture of refractory fillers, metal powders and special additives) onto the area to be repaired. Ignition of the powder occurs only on hot surface of the oven. Exothermic reaction takes place at about 2500 °C and results in crystalline bonding of the applied mass with oven's refractory brickwork.
Main advantages:
- Durability of the repaired portions of brickwork due to the affinity of chemical, mechanical and physical properties of the applied powder to those of the mended refractory brickwork;
- Efficiency, simplicity and ease of repair due to minimal cost of materials and manpower, as well as performing the work on the running ovens;
- Minimal disruption of ovens production cycle and avoiding the negative impact of deep cooling and decarbonization of the refractory brickwork.
- GUNITING
Guniting is the process of applying a repair mixture, coat after coat, onto a very hot repaired surface using high air pressure. The process is done by a guniting machine (concrete gun).
Material used for guniting is called a guncrete mix / gunned concrete.
Main advantages:
- Fast mending of such defects as cracks, cavities, minor through-wall burn holes and undercuts of refractory brickwork, joints between the reinforcing frames and end-flue wall parts; cracks and leakages in regenerator walls;
- Efficiency, simplicity and ease of repair due to minimal cost of materials and manpower, as well as performing the work on the running ovens;
- Minimal disruption of ovens production cycle and avoiding the negative impact of deep cooling and decarbonization of the refractory brickwork.
3.2. RESTORATION OF OVENS SOLES BY GROUTING AND/OR REBRICKING
Repair of the ovens’ soles, depending on their condition is made by grouting, guniting or in case of considerable defects by method of rebricking / replacing of the sole plates.
RESTORATION OF THE OVENS’ SOLES BY METHOD OF GROUTING:
Restoration of the ovens soles by grouting is done using a dedicated NIKA ceramic mixture, which represents a carefully dosed blend of refractory materials and fine particles of metal fuel and oxidizer.
The method is as follows:
Powder is initially mixed with water to achieve a well-balanced suspension. Suspension is poured onto a clean sole surface using special ladles. As a result, mixture spreads on the sole surface filling the defects. Exothermic reaction where the temperature reaches 2000 ÷ 2500 °C begins after drying and heating the mixture up to ~ 750 °C. Exothermic reaction results in the ignition and melting of ceramic mixture, submelting of silica brickwork of the oven’s sole chamber and filling the defects by finally forming a flat and smooth surface.
RE-PAVING OF SOLE PLATES:
Replacement of sole plates is done if they are heavily worn-out or damaged by the pusher ram or coke mass, causing difficulties in coke pushing or ovens sticking. Oven sole is replaced from the door sill up to the point where the old and new sole plates are flush, to ensure proper coke pushing.
3.3. SUPPLY OF CERAMIC POWDERS AND CERAMIC WELDING MACHINES
- MEGA-K: ceramic mixture for mending silica brickwork of coke ovens silica brickwork by method of ceramic welding;
- NIKA: ceramic mixture intended for restoration of ovens’ sole surfaces by method of synthesis of refractory material in the combustion wave. HAVE NO ANALOGS ABROAD;
- BARRIER: ceramic powder used for sealing of micro-cracks of heating walls of coke oven batteries;
- MEGA-CHAMOTTE: ceramic mixture used for repairs of refractory lining of industrial ovens;
- MAKS: ceramic welding machine used for repair of refractory lining of industrial ovens.
Tight laboratory control of all repair materials guarantees unvarying high quality of supplied products. All repair materials are protected by RF patents and have appropriate safety certificates.
4. REPAIR OF COKE OVEN BATTERY BRACING EQUIPMENT
Reinforcing equipment is an important structural element – operating reliability and service life of coke oven batteries depends on its condition. Reinforcement provides solidity and density of coke oven battery brickwork, reduces the impact of mechanical stress on the brickwork at ovens charging and coke pushing while in operation.
Equipment for the reinforcement of brickwork of modern coke oven batteries includes:
- reinforcing flash-plates and frames;
- main anchor columns/buckstays;
- small interim anchor columns/buckstays;
- flash-plates or reinforcing beams embedded into the walls of regenerators;
- flash-plates reinforcing the walls of sole channels;
- springs;
- upper and lower longitudinal anchor tie-rods;
- longitudinal tie-rods.
Constant inspection and maintenance of the reinforcement equipment, timely adjustment and maintenance are essential for keeping of coke oven battery in working condition.
5. OPERATION OF COKE OVEN BATTERIES AND COKE DRY COOLING PLANTS
Reliability and durability of coke-making and by-product facilities, quantity and quality of coke produced, recovered coke oven gas and by-products depend to a large extent on the proper operation of these facilities.
Technical assistance in operation of coke-making and by-product facilities is focused on:
- Achieving maximum production capacity;
- Improving products quality;
- Reducing emissions to the ambient air and water basin;
- Enhancing service life of the main production assets;
- Improving industrial discipline of the operators and their abidance to the safety regulations;
- Reducing energy costs in coke production through the following:
* improving the ovens heating system;
* introducing the advanced operation level;
* adjusting and upgrading operation of units and mechanisms;
* technical training and upgrading of skills of the operation & maintenance personnel.