Improper selection of cylinder material at the expansion joint of the return leg of CFB boiler, insufficient reserved expansion gap, unreasonable structural form, single anchor form, etc., lead to a high defect rate of refractory castable materials, frequent damage, and even return of material The phenomenon of red burning of the leg cylinder and carbonization failure of the material seriously affects the operation of the unit, reduces the operational reliability of the unit, and directly affects the economic operation of the boiler.
(1) The inner cylinder of the original expansion joint is made of 16Mn steel, and the operating temperature is -20 to 475°C. The operating temperature of the return leg is 800 to 900°C, which is higher than the operating temperature of 16Mn steel. It cannot adapt to the working conditions and the material is over-temperature operated for a long time. It will eventually become carbonized and fail.
(2) The reserved expansion gap between the inner cylinder and the outer cylinder is insufficient, and the limited expansion causes local deformation of the expansion joint, causing the refractory castable material to fall off.
(3) The original refractory material is supported by an annular bracket. When the annular bracket thermally expands, it is restrained by the inner cylinder and deforms downward. The refractory material cannot be effectively supported and eventually falls off.
(4) The original anchors are Y pins, which are arranged staggered every 150mm. There is no steel mesh at the end of the pins, so that the refractory materials cannot form a whole. The failure of individual pins will cause the local refractory materials to loosen, and there is no reliable connection between adjacent refractory materials. Contact, eventually falling off.
2. Solution to the falling off of the refractory castables and wear-resistant material of the expansion joint of the boiler return leg
1. Replace the inner cylinder material of the expansion joint with 1Cr18Ni9Ti, leave a 50mm expansion allowance, and weld the refractory bracket. The steel plate butt welds are to be grooved at 30°, and the welding rod model A302 with a diameter of 3.2mm is used. The welding current is 90~110A to ensure full penetration in the thickness direction of the material. The refractory material bracket is changed from an annular shape to a dispersed support arrangement of 150mm×200mm×12mm steel plates. The steel plate material is 1Cr18Ni9Ti and reinforced with triangular plates of the same material. This not only avoids large stress deformation caused by thermal expansion of the annular plate, but also effectively supports the refractory materials; The bracket fillet welds are all fully welded, and the welding leg height is 10mm.
2. The anchor material is 310S. Make accurate 10mm×300mm pins, arrange them staggered every 100mm, fully weld the roots, and weld the 100mm×100mm steel grid at the ends. Reserve 3mm labyrinth expansion joints every 500mm to meet the needs of refractory materials. Expanding demand. The welding rod is A402 model, the welding current is 90~110A, the welding seam direction is full, the anchor welding must be firm, there should be no cracks and slag inclusions, and it should be perpendicular to the guard plate. The surface should be painted with 1~2mm thick asphalt paint and cast with thermal insulation. Before material construction, two layers of 20mm aluminum silicate fiber boards are pasted on the backing board, with staggered seams between the layers. When constructing the insulating castables, manual laying methods are used. During construction, the thickness must be 148mm at one time. Do not construct in layers. Use special tools to compact and then calender, and tap and compact the surrounding construction joints. Weld 100mm×100mm steel mesh of accurate 6mm and 310S material to enhance the fixation of wear-resistant castables. All grab nails should be painted with asphalt paint before plastic construction.
3. Construction with wear-resistant plastic refractory castables. After the plastic is laid on the construction components, use a wooden hammer or rubber hammer to pound it tightly. The joints between blocks should also be pounded and compacted to make the joints tight, and the surfaces should be calendered and flattened. The joints between the construction site and the original wall should ensure a smooth transition and should not be concave or protruding. Use aluminum silicate fiberboard soaked in aluminum phosphate solution to seal the expansion joints to avoid air channeling during boiler operation, which may cause burning damage to the non-metallic compensator.
