Method for decreasing occurrence rate of transverse cracks of boiler water walls

Abstract

The invention relates to a method for decreasing the occurrence rate of transverse cracks of boiler water walls. The method comprises the following steps, from wall temperature monitoring to hole expanding, that when a boiler and the water walls operate, the temperatures of the water walls on the four sides and water wall pipes are monitored correspondingly; a thermal deviation curve showing temperature distribution of the water wall pipes in the water walls on the four sides is drawn according to measured temperature data, and whether water wall pipes located in an overheat area exist or not is judged; and throttling holes corresponding to the water wall pipes located in the overheat area are expanded, wherein after hole expanding is conducted during one time of operation, wall temperature monitoring and overheat judging are conducted in the next time of operation, and throttling holes corresponding to the water wall pipes located in the overheat area are expanded after the water wall pipes located in the overheat area are judged to still exist. By adoption of the method for decreasing the occurrence rate of the transverse cracks of the boiler water walls, the occurrence area and probability of the transverse cracks of the water walls are substantially decreased, and the safety of the water walls is improved.

Description

technical field [0001] The invention relates to the field of boiler water cooling walls, in particular to a method for reducing the occurrence of transverse cracks in the boiler water cooling walls. Background technique [0002] At present, there is a 4×660MW ultra-supercritical unit, which uses 4 HG-2000 / 26.15-YM3 ultra-supercritical once-through boilers with variable pressure operation. It adopts a П-type layout, a single furnace, and an improved low-NOx PM main combustion Device and MACT type low NOx staged air supply combustion system, wall type tangential combustion method, furnace adopts inner threaded tube vertical rising film type water wall, starting system with recirculation pump, one intermediate reheating. [0003] Among them, the furnace water wall adopts welded membrane wall and internal thread pipe vertical rising type; the lower header of the water wall adopts a small diameter header of φ219mm, and the throttle ring is moved to the inlet section of the water ...

AI Technical Summary

Problems solved by technology

[0005] However, after the actual operation, it was found that the water wall of this boiler had transverse cracks in several water wall tubes, most of which were located at the lower elbow of the middle header of the front wall water wall and below the elbow

The similar horizontal crack leakage problem of the water wall of the boiler will cause the unit to be shut down and affect the safe operation of the unit

Reasons for cracks: (1) The unreasonable design of the orifice of the water-cooled wall is unbalanced in the temperature field of the water-cooled wall, and the distribution of the combustion heat load does not match the flow rate of the medium in the tube, resulting in excessive thermal deviation of the temperature of the adjacent tubes of the water-cooled wall; (2) Water-cooled The structure of the header in the middle of the wall is unreasonable, resulting in local thermal stress; (3) The "superheat" fluctuates too much and the rate is too high, especially during the change of working conditions

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