In the circulating fluidized bed boiler, the concentration of solid materials in the circulating fluidized bed boiler is several tens to hundreds times higher than that of the pulverized coal boiler. Due to the high particle concentration in the boiler and the high operating wind speed, the flue gas flow rate is larger and the particles are more The coarseness causes the refractory material to be subjected to continuous scouring and abrasion of a large amount of solid materials, so the wear prevention problem of the refractory material should be given special attention. The installation of the refractory wear-resistant structure is the key to the normal and safe operation of the unit. In the construction process of refractory castables, it is greatly affected by various aspects, so it must be controlled in all aspects. Refractory castables are critical for storage, inspection, installation of heat-resistant steel bars, installation of expansion joints, installation and installation of wood molds, mixing, vibrating, baking, etc., and must be constructed in strict accordance with procedures. I will talk about the matters needing attention during construction on several key points.
1. Selection and storage of refractory materials
There are many types of refractory materials used in circulating fluidized bed boilers, and different types of materials are used in different parts. Low-quality refractory materials cannot be selected at low prices. After the materials enter the factory, the sorting is neatly stacked and there are obvious signs. Refractory materials are strictly prohibited from moisture, and moisture-proof measures should be taken. At the same time, it should be noted that if the validity period of the boiler castable has exceeded this period, it should be tested and used only after the test is passed.
2. Inspection of refractory materials
After the materials arrive at the site, the materials are inspected in time, and the indicators meet the technical requirements; pay attention to the production time and expiration date of the products, and materials exceeding the expiration date are forbidden to use. After the materials enter the site, we will organize experienced furnace technicians in time to make test blocks according to the information provided by the manufacturer and the Ministry of Electric Power's "Quality Inspection and Evaluation Standards for Thermal Power Construction". The refractory material can be used only after it has passed the effective inspection report.
3. Installation of heat-resistant steel bars
After the heat-resistant steel bar is put into the scene, the spectrum analysis is carried out in time to check whether the material meets the requirements. In order to ensure that the heat-resistant steel bars are arranged neatly and beautifully, the position of the steel bars is arranged according to the design distance, and the longitudinal and horizontal lines are laid by the design distance according to the design distance. The heat-resistant steel bars are welded to the fire surface of the equipment at the joints of the line, and are arranged into a steel mesh. Before welding, the welded joint between the heat-resistant steel bar and the metal shell is polished with a sanding machine to remove the rust and paint to ensure good welding and no welding defects.
4. Installation of expansion joints
The furnace wall structure of circulating fluidized bed boiler of Sichuan Baima 1*300MW demonstration power station is designed by France ALSTON Company. The boiler is designed with a working seam. The working seam is designed to be smaller than the area of 1 m * 1 m. The structure of the working seam is arranged in the wrong tooth, and in the fire surface of the castable, the working seam has a groove of 10 mm high and a width of 20 mm, and is in the furnace. Fill the 2mm ceramic plate between the working seams in the middle of the wall. The working seam can compensate for the micro-expansion of the refractory castable at high temperatures and prevent surface cracking of the castable. Therefore, the construction of the refractory castable cannot be carried out in a large-area construction, but is divided into a plurality of smaller working areas, and the area of each block is less than 1000 mm*1000 mm, that is, the maximum pouring area is not more than 1 m2. This kind of design and construction is difficult. In order to ensure the wrong working seam, several layers of the castable construction layer are poured, and each layer is jumped and separated. The remaining part must be removed before the wooden mold can be removed for further construction. low. At the same time, effective measures should be taken to ensure the shape of the work seam in the wood mold configuration.
5, wood mold configuration and installation
The quality of the casting quality depends on the configuration and installation of the wood mold. Due to the wide pouring surface and irregular shape of the castables of the circulating fluidized bed boiler, the work of making and installing wood molds is large and difficult. Therefore, it is necessary to organize high-level woodworkers with strong technical skills and experience to carry out construction. Templates should be made from qualified materials, and the surface of the wood mold should be clean and smooth, otherwise the template will become stuck or become porous at the point of contact. Since some of the structures are curved, after the wooden mold is made into a finished product, it is inevitable that there is a place where the seam is not strict. At this time, a layer of a wide tape is required to be adhered.
Stirring, pouring and rapping are a continuous process. The work should be continuous and the construction time should be controlled. The refractory material must be agitated to make the castables evenly mixed. Stirring is a very important process because it has a decisive influence on the quality of the lining. Good agitation ensures the properties of the refractory. The stirring equipment, the stirring time, and the amount of the stirring liquid added are all very important. If there is an error in this link, the refractory cast material for installation will not achieve the expected results.
1 Stirring equipment Refractory casting materials are usually stirred by an impeller stirrer, which ensures good mixing of the binder. Generally, the gap between the mixer blades in the country is 6-8 mm from the casing, and the aggregate of the refractory castable is generally less than 6 mm. The gap between the blades of the mixer and the casing is 2 mm to 3 mm, which is suitable for ensuring the full mixing of the materials. It is necessary to adjust and improve the blade clearance.
2 The mixing time of the refractory castables with different mixing time is different. Generally, the mixing time of the castables is 4 minutes, but some refractory materials have a stirring time of about 6 minutes, because the binder of the material requires a long time of stirring to fully mix.
3 Stirring sequence is to meet the uniform distribution of refractory material during the stirring process, dry stirring for 30 seconds to 60 seconds without water, and the refractory pouring material is dryly stirred before adding water, which can offset the drying which may be isolated during transportation. The influence of pouring materials. Then add 80% water. The remaining water should be carefully measured to add the best results. After mixing, perform a viscosity check to check if its current state can be used for installation.
The water used for the mixing of refractory castables should be sampled and sent for inspection. The quality requirements of the water for the stirred liquid should meet the technical specifications. However, the amount of water added must be within the specified range. Therefore, the dry moisture of the refractory castable and the appropriate water should be tested at any time. The water temperature, ambient temperature, and material temperature were measured every morning and afternoon and recorded.
The castable is tamped uniformly and densely. In addition to refractory spray coatings, all refractory casting materials must be rapping. The advantage of rapping (tamping) is to reduce the porosity of the installed refractory material to increase stress. With a plug-in rapper, the rapper should be removed slowly so that no holes are left on the refractory. If a large amount of refractory material is found to sag and many small bubbles are generated on the surface, the rapping is good. If boiling occurs, the rapping should be stopped because there is a risk of segregation.
The refractory material that has been stirred should be poured immediately. If the pouring area is too large for the refractory material to be poured into the continuous refractory layer, the casting area must be divided into zones, so that a working seam is provided to allow the interval between the first casting and the addition of the second refractory. No more than 20 minutes to ensure effective bonding between successive layers. The construction time of general materials is about 30 minutes. According to the technical requirements of the materials used in the construction control, the mixing of each material and the time from discharge to use (usually 30 minutes) are controlled; if the materials that have not been used up during this time are firmly rejected, it is not allowed to be re-constructed. Use, otherwise large cracks will appear on the surface of the wear layer when the oven is used. If this link is not controlled well, it will not only affect the quality of the construction, but also cause a lot of waste of materials.
8, demoulding, baking
The mold is removed after the castable has hardened. At normal temperatures, the module can usually be removed after 12 hours. The hammering sound test should be performed first before demoulding. If the crisp sound is hammered on the refractory lining material, it proves that the refractory material has been effectively hardened and the module can be removed.
Drying is strictly performed according to the refractory baking curve and the temperature is controlled. This step should be especially careful. Improper handling can damage the liner. The rate of heating depends on the type of refractory material, the thickness of the lining and the design characteristics.
Circulating fluidized bed boilers have a large amount of refractory and wear-resistant construction, many links, wide coverage, high quality requirements, and irregular internal structure of the equipment. The construction of refractory amorphous castables is the focus of the installation of circulating fluidized bed boilers, and it is also difficult. Therefore, it should be highly valued. Preparation of construction conditions should be sufficient, such as preparation of materials, qualified water sources for construction, production of wood molds, installation of metal parts such as heat-resistant steel bars, planning of material transportation channels, lighting, material storage, test block testing, special tool preparation, personnel training A series of work must be considered in advance, and the links between the various links must be carefully planned.