【Weekly Topic】What requirements should the furnace wall structure of coal-fired boilers meet? (6.27~7.03)

The last edit to this post was made by zgj2405 on 2011-6-27 at 21:24. The furnace wall structure of coal-fired boilers should meet at least the following requirements: a) The rigid beams must be able to expand freely without affecting the expansion of the water wall, and the local structural connections of the ring beams must be reliable； b) During normal operation, there is no significant shaking of the furnace wall ； c) The furnace wall has good sealing and insulation properties ； d) At the design pressure of the furnace, there should be no unevenness, cracks, or smoke leakage in any part of the furnace wall.

The furnace wall structure of coal-fired boilers should meet at least the following requirements: fire resistance, insulation, heat retention, free expansion of structural components and water walls, and sealing.

This post was last edited and replied to by dongjiang1001 on 2011-6-26 at 17:14. Reply 1# zgj2405: The furnace wall is built directly on the boiler foundation; in other words, the weight of the furnace wall is borne directly by the boiler’s foundation. The furnace wall is generally composed of two layers: refractory bricks and red bricks. The furnace wall is thick, usually 500 mm thick, and is also quite heavy. The heavy furnace wall, being built directly on the boiler base and due to its large weight, has a limited height. When it is too high, it not only makes the furnace wall unstable but also, due to its limited strength at high temperatures, it generally should not exceed 10 m. If it exceeds 10 m, structural measures must be taken, such as using a simple metal frame to enhance its stability.

Reply to 1# zgj2405: The common faults of the furnace wall include coking, cracks, bricks being misaligned or falling off, the sealing asbestos rope being damaged, the furnace tubes getting stuck at the points where they pass through the wall, and metal structural components being damaged due to high temperatures. II. Quality requirements for furnace wall maintenance (1) Furnace wall of the combustion chamber: 1. The mortar should be dense, with joint gaps not exceeding 2–3 millimeters. 2. The fire-facing side should be smooth and flat, with a surface irregularity error not exceeding 3–5 millimeters. 3. The joint between the repaired furnace wall and the original one should be tight; there should be no gaps between them. (II) Furnace wall at the main and auxiliary nozzles: 1. The special-shaped bricks used for constructing holes must be free of damage or cracks, and the damage to their edges and corners shall not exceed 5 millimeters. 2. The unevenness of the holes made for masonry shall not exceed 2 millimeters. 3. The diameter error of the holes shall not exceed 5 millimeters. 4. The mortar should be dense, with joint gaps not exceeding 2–3 millimeters. 5. The junctions of the Masonry hole with the furnace walls on the upper and lower sides should be fitted with inclined bricks for secure fixation, and the gap at these junctions must not exceed 4 millimeters. (III) Gaps on both sides of the steam superheater: 1. A gap of 15 to 20 millimeters should be left at both ends of the side walls, and asbestos paper board or asbestos rope should be inserted there. 2. The mortar should be dense, with joint gaps not exceeding 3 millimeters. 3. The walls should be smooth and even, with any irregularities not exceeding 3 millimeters. 4. The joints of the two walls should be stacked in alternate layers; they must not meet end to end. 5. Expansion joints should be sealed with 20-mm asbestos rope. (IV) Slope wall of steam superheater: 1. The mortar should be full, and the joint gap shall not exceed 3 millimeters. 2. The surface of the furnace wall should be smooth and flat, with the variation in elevation not exceeding 5 millimeters. (V) Furnace wall expansion joints: 1. The expansion joints should be filled with three layers of asbestos rope, each 20–25 millimeters thick, and coated with asbestos putty to ensure a tight and leak-free seal. 2. During maintenance, do not drop broken bricks or debris into the expansion joints to avoid jamming.

I. Common faults of the furnace wall include coking, cracks, misaligned or detached bricks, damaged sealing asbestos ropes, hard objects getting stuck at the points where the furnace tubes pass through the wall, and damage to metal structural components due to high temperatures. II. Quality requirements for furnace wall maintenance (1) Combustion chamber furnace wall: 1. The mortar should be dense, with joint gaps not exceeding 2–3 millimeters. 2. The fire-facing side should be smooth and flat, with a surface irregularity error not exceeding 3–5 millimeters. 3. The joint between the repaired furnace wall and the original one should be tight; there should be no gaps between them. (II) Furnace wall at the main and auxiliary burners: 1. The special-shaped bricks used for drilling holes must be free of damage or cracks, and the damage to their edges and corners shall not exceed 5 millimeters. 2. The unevenness of the holes made for masonry shall not exceed 2 millimeters. 3. The diameter error of the holes shall not exceed 5 millimeters. 4. The mortar should be dense, with joint gaps not exceeding 2–3 millimeters. 5. The junctions of the Masonry hole with the furnace walls on the upper and lower sides should be fitted with inclined bricks for secure fixation, and the gap at these junctions must not exceed 4 millimeters. (III) Gaps on both sides of the steam superheater: 1. A gap of 15 to 20 millimeters should be left at both ends of the side walls, and asbestos paper board or asbestos rope should be inserted there. 2. The mortar should be dense, with joint gaps not exceeding 3 millimeters. 3. The walls should be smooth and even, with any irregularities not exceeding 3 millimeters. 4. The joints of the two walls should be stacked in alternate layers; they must not meet end to end. 5. Expansion joints should be sealed with 20-mm asbestos rope. (IV) Slope wall of steam superheater: 1. The mortar should be full, and the joint gap shall not exceed 3 millimeters. 2. The surface of the furnace wall should be smooth and flat, with the variation in elevation not exceeding 5 millimeters. (V) Furnace wall expansion joints: 1. The expansion joints should be filled with three layers of asbestos rope, each 20–25 millimeters thick, and coated with asbestos putty to ensure a tight and leak-free seal. 2. During maintenance, do not drop broken bricks or debris into the expansion joints to avoid jamming.

The furnace wall should have good sealing and insulation properties, and there should be no unevenness, cracks, or smoke leaks in any part of it

The furnace wall is built directly on the boiler foundation; that is, the weight of the furnace wall is borne directly by the boiler foundation. The furnace wall is generally composed of two layers: refractory bricks and red bricks. The furnace wall is thick, usually 500 mm thick, and is also quite heavy. The heavy furnace wall, being built directly on the boiler base and due to its large weight, has a limited height. When it is too high, it not only makes the furnace wall unstable but also, due to its limited strength at high temperatures, it generally should not exceed 10 m. If it exceeds 10 m, structural measures must be taken, such as using a simple metal frame to enhance its stability. Since industrial boilers are generally below 10–12 m, heavy furnace walls are used.