Introduction to fire-resistant and heat-insulating knowledge

Here is an introduction to the material specifications and construction standards for the refractory materials used in the furnace of the NAPP thermal power plant, which is quite useful. Standards for selecting and applying refractory materials (castables) in the furnace of NAPP’s CFB boilers: I. Technical standards for selecting refractory materials (castables) for CFB boiler furnaces: Service temperature: 1650 ℃ Density: 2.7 g/cm3 Compressive strength: 100 N/mm2 Erosion resistance: 8 ASTM C-704 Linear deformation rate: -0.2 % Porosity: 20 % Thermal conductivity: 1.7 W/mK Method of application: Sheet formwork + self-flow pouring II. Construction standards for refractory materials (castables) in CFB boiler furnaces: 1. Construction must be carried out under the supervision of professional engineers. 2. When the casting material arrives at the site, it must be dry and free of lumps before mixing. Materials that are not in use temporarily should be stored in a dry, moisture-proof, and fire-resistant place. 3. The clean water used for mixing the castable has a pH value of 6–8; the amount of water added is strictly controlled in accordance with the technical specifications for refractory material installation (provided by the manufacturer). Clean the mixer thoroughly before use. 4. Pour the casting material into the mixer and stir for 5 minutes before removing it; the stirring time should be no less than 5 minutes and no more than 20 minutes. 5. The mixed casting material should be used up within 30 minutes (material that has hardened cannot be used), and it is advisable to pour it to the specified thickness in one go. 6. Vibration tamping: Use vibration rods with a diameter of φ20mm or φ25mm; when using them, it is necessary to insert them quickly, pull them out gently, and move them slowly. The vibration time should not be too long, as this can cause the upper layer of aggregates to separate from the binder, affecting the quality of the cast material; generally, it is sufficient when the surface is flat, with no obvious settlement, and some slurry is present. 7. Precautions: In the water wall area surrounding the furnace chamber, there are numerous openings such as the return material port, secondary air inlets, slag discharge pipe openings, return gas pipe openings, temperature and pressure measurement ports, and access holes. For the metal fittings and structural components in all holes, except that the diameter of the hole at the pressure measurement tube should be identical to the inner diameter of that tube, the diameter of the holes at the locations where tubes pass through should be equal to the outer diameter of those tubes. Moreover, all such tubes must be coaxial with the construction holes. For the pipes mentioned above with a diameter greater than 159 mm, petroleum asphalt should be applied in a thickness of 1.5 mm prior to construction ； Pipes with a diameter of less than 159 mm should be coated with petroleum asphalt to a thickness of 1 mm. On the flat steel of the diaphragm wall at the return valve openings, air duct openings, slag discharge pipe openings, and return air pipe openings, additional pins can be welded on as needed based on the site conditions; or some pins can be welded onto the sealing box plates. These pins can be lengthened or shortened as required to secure the wear-resistant cast material in the areas surrounding these openings. These pins should also be coated with petroleum asphalt before installation. Inside the sealing box of the exterior wall at the wall-penetrating opening area, lining material with the same performance as that of the working surface in that area shall be installed in accordance with the construction drawings. For work around the pipe outlet, it is necessary to check the installation and acceptance documents for the structural components of the pipe outlet prior to commencing work, and only proceed with construction after it is confirmed that they meet the requirements specified in the structural construction drawings. The return material port, manhole, return gas port, and the transition section of the dense phase zone are special areas that must be given careful attention during construction. During construction, work must be carried out carefully and meticulously, following the detailed plans approved through technical discussions. When working on these areas, the inspection department should be notified; only after each stage of construction has been verified as correct can the next stage proceed, and records of the inspections for concealed works must be kept. When carrying out construction on the coal feed port, the following points should be noted: 1. Protection of the metal of the coal feed port must be considered. 2. The working environment at the coal feeding port is harsh, so vibration damping must be thorough. 3. Smooth and unobstructed exports. The construction of the secondary air nozzles is crucial and must be taken seriously; it is necessary to ensure that the size and orientation of the nozzles are correct, with no debris inside them. Special attention should be paid to the distance between the edge wind cap and the side walls; it must not be too large to avoid the formation of fluidization dead zones ； It shouldn’t be too close either, as that could block the air cap opening. 8. Construction inspection and acceptance: After construction is completed, the surface should be free of honeycombing or pitting, without any shrinkage cracks or fissures, and without pores that exceed the specified limits; the levelness must meet the acceptance requirements. 9. Curing: a. Demold after 24 hours of natural curing. b. When the temperature is below 150°C, it is possible to introduce hot water or hot steam at an appropriate temperature into the water wall tubes for curing; by controlling the amount of water (steam) supplied and replacing it at appropriate times, the temperature can be regulated. c. Once the temperature reaches 150°C, bed-type ignition oil guns are used for baking, with the temperature rise controlled in accordance with the ‘Furnace Heating Curve’ provided by the refractory material supplier.

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“DLT 777-2012 Refractory Materials for Boilers in Thermal Power Plants”. There are few standards for refractory materials in China, with provincial standards and enterprise standards being the most common; this is one of the rare national standards, issued last year.

There is a standard specification for lined pipes in the chemical industry; it’s quite standardized, and there are many parameters related to the lining material used