RESTORATION OF TECHNICAL CONDITION OF COKE OVEN BATTERIES WITH HEIGHT OF CHAMBERS 7,0 M AT VISAKHAPATNAM STEEL PLANT (VIZAG STEEL), INDIA
Coke oven batteries №№1, 2, 3 with volume of chambers 41,6 m³, were commissioned at VSP in 1989, 1991 and 1992 respectively.
In September, 1998 coke manufacture began to drop down due to the failure of reinforcing units of the batteries and destruction of refractory brickwork. The age of the batteries by that time was 9, 7 and 6 years respectively.
The process of the productivity decline and emergency conditions at coke oven batteries continued till June, 1999. By that time three batteries had 97 operating ovens only out of 201 ovens as per the design, the number of coke pushings per day had decreased down to 110, instead of normal 250. Half of the operating ovens were incompletely charged.
After careful inspection of coke oven batteries and analysis of the situation the experts of LLC “OKOS” developed and offered the program of rehabilitation of coke oven batteries and fast increase of coke productivity to the VSP management. This program was adopted by the VSP management and material resources were allocated for realization.
Such strategy of realization of repair allowed VSP:
- to restore serviceability of all ovens at Coke Oven Batteries №№1, 3 by July, 2000;
- to shut down Coke Oven Battery №2 for cold repair;
- to achieve required volume of coke manufacture and to keep it at a level of 250 oven-pushings per day, by April, 2001;
- to carry out preventive repairs of refractory bricklaying by various types of guniting which provide operation of coke ovens up to their planned time of repair.
Cold repair of the top structure of Coke Oven Battery №2 with partial repair of the inclined flue zone and regenerators, with partial replacement of reinforcing units and equipment was executed within 11 months as per the technology and schedules developed by the experts of LLC "OKOS".
During repair new solutions on reinforcing of refractory brickwork were applied, - complete replacement with reinforcement of service platform from the coke side.
At repairs of refractory brickwork of Coke Oven Batteries №№ 1, 3 several methods of repair were tested – repair of end parts of heating walls, half of the heating wall and rebricking of the heating wall throughout the whole length.
Repair was performed primarily on the unhealthiest ovens not by a sequenced-flow-group method.
By the results of the repair works carried out at VSP the following conclusions can be drawn:
Realization of "hot" repairs of complete heating walls and “end” parts of heating walls to the various depth has allowed to restore serviceability of coking chambers at Coke Oven Batteries №№1;3 without significant losses in coke production and deterioration of condition of refractory brickwork of "buffer" walls and inclined flue zones and to achieve the required volume of coke production at VSP at the given stage.- Maximum preservation of coke production, increase of repair rate, reduction of repair costs were achieved at the execution of "hot" repair by the line method –one wall at a time.
- The operating experience shows that "hot" repair of complete heating walls can increase the battery’s service life before its complete rebricking by 10-12 years.
- End parts of heating walls repaired by a "hot" method, can work not less than 9 years under normal operating conditions till complete rebricking or reconstruction of the battery at strict performance of routine preventive measures to ensure the integrity of the joints of old and new brickwork (ceramic welding, gunning, etc.).
- After realization of the "cold" repair of coke ovens’ top structure the remaining old refractory brickwork of the inclined flue zone, regenerators’ zone and ovens sole level can operate for another 12-15 years.
- As a result of teamwork of Indian and Russian experts of LLC “OKOS” many problems at coke oven batteries (undercharging, oven sticking, incompliance with sanitary regulations on emissions) have been solved. The condition of coke oven batteries has been considerably improved. The level of operation and equipment maintenance became significantly high. Coke manufacture has reached its planned production capacity. Conditions were created (production level) to shut down Coke Oven Battery №2 for cold repair.