Li Zhonghua, Li Guangjian, Jiang Jianfei, Wang Jinyang analyzed and studied the problems in the thermal insulation and sealing of Russian-made 230t/h boiler imported from Pingdingshan Group Power Plant with different environmental standards, difficulties in material purchase, and construction difficulties, and changed the design of Russia. , Selection of domestic insulation seal materials and the corresponding construction program, saving investment and speed up the construction schedule. The results show that the improved boiler insulation and sealing performance is good.
Insulation sealing boiler furnace top sealing furnace wall Insulation Pingmei Coal Group No. 1 boiler is a 230t/h ultra-high pressure natural circulation drum boiler imported from Russia Siberian Power Equipment Factory. The boiler insulation and sealing are designed in accordance with the Russian environmental standards, the required refractories Most insulating materials, insulation materials, plastering materials (sealing paints) and other auxiliary materials are produced in Russia. Domestic purchases are very difficult and operation and maintenance are extremely inconvenient. Moreover, the insulation and sealing structures designed by Russia are also very difficult for Chinese construction. In order to speed up the construction progress, reduce investment, and save foreign exchange, the factory decided to change Russia’s thermal insulation and seal design according to China’s environmental standards, choose domestically-available insulation sealing materials that are easy to purchase, and facilitate improved construction programs.
1 Improvements 1. Furnace part of the furnace wall Since the furnace adopts a membrane-type water-cooled wall and the furnace wall is well protected by the water-cooled wall, this part of the furnace wall should be primarily considered for thermal insulation. The insulation material is made of perlite-insulated concrete and foam. asbestos. In order to make the insulation material and the water-cooled wall together, fastening bolts are arranged on the water-cooled wall sheet tube. The entire insulation layer is finally sealed with a 0.8mm special aluminum alloy corrugated board. In order to make no gaps between the insulation layers, they are integrated to reduce convective heat loss, and high-temperature adhesives are applied between the insulation layers. The high-temperature binder is an aluminum sulfate product and forms a ceramic after sintering at a high temperature.
1.2 The top of boiler wall There are a large number of tube bundles passing through the top of the furnace wall, and it is in a positive pressure state. It is also necessary to consider the walking of the top personnel. The insulation and sealing of the furnace top wall must have a certain strength. In order to make the top sealing performance good, designed according to zero air leakage rate.
A layer of 50mm thick, high-temperature, micro-expandable, plastic refractory material is applied to the ceiling tube. The tube bundles that pass through the ceiling are sealed in boxes designed by Russia. The first layer in the box is a high-temperature micro-expanded refractories, and the thickness is 50mm. The second layer is silicon. Acid aluminum refractory fiber, thickness 50mm, filled with a layer of 50mm thick aluminosilicate plate with polyvinyl acetate emulsion.
The top of the furnace adopts a large shell-type centralized insulation instead of dispersion and insulation. Therefore, the pipe and header of the furnace top part do not need to be insulated individually, and the whole roof is covered with a 60mm X60mmX50mmlCr13 network board. A layer of 50mm thick aluminosilicate refractory fiber is laid on the network board, and then three layers of waterproof foam asbestos boards with a thickness of 50mm are laid. The foamed asbestos boards are dislocated by means of dislocations. Lastly, 40mm thick perlite insulation concrete was used. Inside the barbed wire (size 20mmX20mmX1.0mm galvanized), 20mm trowel layer was applied, and a layer of glass cloth was applied to the polyvinyl acetate emulsion. In order to make the insulation material more firm, use d5 pins to fix, apply aluminum sulfate high temperature adhesive between each insulation layer.
1.3 The corners of the fold angle and the bottom wall of the seam at the bend angle and the bottom wall are due to the thermal expansion change, which is the place where the high-temperature flue gas is most likely to emerge. Therefore, the heat preservation and sealing at the place are not to guarantee the water wall and The free expansion of the bottom wall, 3mm expansion joints in the middle of the refractory concrete, plugged with aluminum silicate. After the back side of the sealed steel plate is filled with foamed asbestos, it is used together with the bottom wall and furnace corner furnace walls.
1.4 Seam and Water Wall Joints 1.4.1 Between the ceiling and front water wall seams The roof and front water wall seams are exposed to high temperature due to the relative change in thermal expansion between the ceiling tubes and the water wall. Is the most critical part of the seal.
As shown, 1Cr18Ni9Ti high-temperature alloy sealing steel plates with a thickness of 2 mm are used at the seams to prevent the smoke from escaping. Taking into account the free expansion of the former water-wall and ceiling pipes, the sealing steel plates are joined by lap joints with a lap length of not less than 50mm. To enhance insulation and sealing, a layer of 50mm high-temperature micro-expandable plastic refractory material is first applied on the sealing steel plate. Then, it is filled with silicic acid fiber and then used together with the front wall and ceiling furnace wall.
1.4.2 Roof and side water wall and back wall joints 1.5 Superheater section The furnace wall superheater section furnace wall includes a horizontal flue duct, left and right side wall cladding, and back wall cladding. Since these superheaters and membrane water wall have the same place, there are sheets welded between the tubes, so the furnace wall construction here is the same as the hearth section of the furnace wall, but the first layer of perlite insulation concrete thickness is changed to 30. 1.6 boiler steam The insulation of the steam drums of bags, pipelines and ancillary equipment was not designed. In order to achieve the insulation requirements, three layers of 50mm thick foam asbestos were laid on the outer wall of the steam drum. The first layer is a foam asbestos blanket, which is attached to the drum wall with polyvinyl acetate emulsion. The second and third floors are made of waterproof foam asbestos sheet and compressed to 140mm thickness after construction. All layers of foamed asbestos are disjoined by pressure-stitching and pasted with polyvinyl acetate emulsion. The outer layer is stretched with a 20mmX20mmX1.6mm galvanized wire mesh and stretched 10mm before sealing with a 0.8mm thick aluminum alloy plate.
Pipe insulation design within the scope of the boiler body: water supply pipe, down pipe, liaison pipe, external cyclone separator, self-cooled, etc. using asbestos products to keep warm; spray desuperheater, steam header and its steam pipe, blowing The gray steam pipes are insulated with microporous calcium silicate products. The specific construction process is carried out according to the improved plan.
2 Improved insulation verification calculation In order to achieve the desired results when analyzing and researching improvement plans, we adopted http:// many reasonable suggestions for engineers with extensive construction experience. In addition, the boiler insulation and sealing performance is not only related to the design, but also depends largely on the construction quality. In order to further improve and improve the insulation and sealing performance of the improved boiler, the calculation and calculation results of the improved insulation plan show that the improvement plan completely meets the design requirements.
Furnace wall insulation calculation calculation: the first insulation layer thickness of the concrete 3 = 0.04m second insulation foam asbestos thickness 1 = 0. 15m average sheet temperature ti = 420 °C air average temperature "=15.6 °C average wind speed w = 1.734m/s air heat release coefficient assumes that the temperature between the first and second layers t2= 374°C, the outer surface temperature of the insulation layer t3=26...
First insulation layer average temperature tq, 1 Second insulation layer average temperature, 2 == 200°C First insulation layer thermal conductivity Thermal conductivity of second insulation layer Check the temperature between the first and second floor: Calculated and assumed values In line with the improvement requirements.
3 Improvement Effect By improving the insulation and sealing of the boiler, the material investment can be reduced by 20%, which greatly reduces the construction difficulty and speeds up the construction progress. After the boiler was put into operation, the results showed that the heat preservation and sealing effect had been very good, and it was better than the Russian design level and improved the boiler efficiency. It was praised by the production operation and maintenance personnel. At the same time, through the improvement and construction of the heat preservation and sealing scheme, we have also accumulated experience in how to introduce the technical improvements of imported units according to China's national conditions.
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