Analysis of the Application of High – Temperature Glass Wool in Thermal Power Plants

Due to the special circumstances of thermal power plants, the materials used in certain parts of the power plants must have the functions of high – temperature resistance and heat preservation, such as boiler walls, flue gas ducts, electrostatic precipitators, hot air ducts, steam pipelines, and various thermal pipelines. These materials can also reduce heat loss, save energy, and improve economic benefits. Therefore, they are widely used in various thermal power plants and have achieved good results.

I. Characteristics of High – Temperature Glass Wool

High – temperature glass wool insulation material is a lightweight, durable, and high – performance high – temperature insulation material composed of uniform, slender, and elastic glass fibers and special high – temperature adhesives.

 

1. The heat – preservation of high – temperature glass wool is achieved because its fibers are uniformly slender and arranged perpendicular to the heat transfer direction, which can effectively prevent heat transfer and thus reduce heat loss.
2. Due to its lightweight feature, it is convenient to install. During construction, it can be cut according to design requirements with an ordinary paper cutter.
3. The uniform and slender fibers ensure a tight interweaving. Common insulation materials, after being used for a period of time or being vibrated, may be stretched due to fiber disconnection, resulting in voids and an increase in heat loss over time. However, this does not occur with high – temperature glass wool.
4. The material is weakly alkaline and has no corrosive effect on equipment and pipelines.
5. High – temperature glass wool is composed of slender glass fibers and contains no slag balls. Compared with other types of insulation materials, it will not break when soaked in water or rained on. Its moisture absorption rate is less than 0.2% of its mass, and its heat – preservation performance remains unchanged after being dried. Moreover, the material is non – toxic and harmless to the human body.
6. Its fire – non – combustibility is generally Class A.

II. Technical Requirements and Application Effects of Glass Wool in Thermal Power Plants

 

1. When the medium temperature is higher than 350°C, high – temperature – resistant insulation materials should be selected. When it is technically and economically reasonable, a composite insulation structure can also be selected.
2. For the insulation layer materials of special – shaped parts such as valves and elbows, lightweight insulation materials or insulation coatings can be selected.
3. For pipelines with an outer diameter less than 38mm, ordinary aluminosilicate fiber ropes are preferably selected as the insulation layer materials.
4. For low – temperature equipment and pipelines in humid environments (such as trenches), hydrophobic materials are preferably selected as the insulation layer materials.

(I) Technical Conditions of Glass Wool for Power Plants

2. Glass wool is divided into two categories according to the production process: flame method (represented by x below) and centrifugal method (represented by y below). Alkali – free glass wool is divided into three types according to the average fiber diameter of glass wool in GB/T 13350, as shown in the following table:Table 1 Average Fiber Diameter of Glass Wool
   

   Types of glass wool	average fiber diameter
   No. 1	≤5.0
   No. 2	≤8.0
   No. 3	≤11.0

   The physical properties of glass wool shall comply with the provisions of Table 2b.

   Table 2 Physical properties of glass wool

   Types of glass wool	Thermal conductivity (average temperature 70 ± 5 ℃) W/(K)	Thermal load shrinkage temperature ℃	Safe use temperature ℃
   1	0.041(40)	≥400	≤300
   2	0.042(64
   3	0.042(64)

   Note: Average temperature = (medium temperature + surface temperature of thermal insulation structure) 2

   When all kinds of products have waterproof requirements, the quality moisture absorption rate should not be more than 5%, and the hydrophobic rate should not be less than 98%. The slag ball content of cotton used in products: No. 1x should be equal to or less than 1.0%, No. 2x and No. 3x should be equal to or less than 4.0%, and No. y should be equal to or less than 0.3%.

   (2) Use effect

   The use effect in the boiler. A thermal power plant has a 200MW unit boiler, and the temperature of the primary air duct reaches 350 ° C, and the temperature of the hot air duct at the outlet of the air preheater also reaches 390 ° C. High-temperature glass wool products are compared with aluminum silicate cotton products. When the thickness of the insulation layer is the same, however, the temperature of the outer surface of the insulation layer of high-temperature glass wool products is 2 ° C -6 ° C lower than that of aluminum silicate cotton products, and it has been used for a long time at 350~ 390 ° C without any problems. Another example is the boiler wall of a 350MW generator set in a power plant. Its primary and secondary air ducts and flue ducts are all insulated by high-temperature glass wool products. After the equipment is put into operation, the surface temperature of each part is tested, and the results are shown in Table 3. From the data, it is concluded that the thermal insulation effect meets the requirements, and the difference between the surface temperature and the ambient temperature does not exceed 25 degrees Celsius.

   Table 3 Test data of various parts of boiler furnace of 3 500 MW unit

   location	Ambient temperature/℃ meter	Surface temperature/℃
   Forward hearth	33	42
   Behind the furnace	33	42
   primary wind	28	38
   secondary wind	28	39
   flue	28	32

   2. The effect of use in pipes. Use for heating pipes (go down to page 117)
   3. The frequency has also increased accordingly, mainly reflected in the formwork support and deep foundation pit engineering support, forming the fifth largest injury after the four major injuries. As a supervision engineer, we must conduct safety supervision of construction facilities, equipment and human behavior from different aspects according to the specific characteristics of project construction. Key safety supervision needs to be carried out, including:Temporary electricity use. As a supervision engineer, you should review the temporary electricity use plan for construction

      Whether it meets the requirements of mandatory standards and specifications, the goal is that the erection and installation of temporary electricity should ensure the safety of use and prevent the occurrence of electric shock accidents. For temporary electrical equipment, the safety protection meets the requirements of standards and specifications. The key control objects of safety supervision are electricity consumption, the correct choice of protection methods, the installation of line and electric box leakage protectors in accordance with regulations, the power supply voltage of on-site lighting and the protection requirements of external overhead lines.

      Work at heights. As a supervision engineer, he should check whether the erection of various safety signs and safety nets meets the requirements of mandatory standards and specifications, and check whether the relevant safety facilities are accepted. The goal is to ensure that the operators have basic safe working conditions to prevent falls from heights and object strikes. Safety supervision focuses on controlling the objects, such as holes and edge operations, climbing and suspended operations, operating platforms and cross operations, etc., and the safety and reliability of protective measures for working at heights under various conditions.
      Saffold erection. As a supervision engineer, should first review the scaffold erection safety measures and safety special project construction plan to meet the requirements of mandatory standards and regulations, and supervise the construction unit to implement. The goal is to make the scaffold meet the use requirements, load requirements and protection requirements, to prevent the occurrence of high falls and frame collapse accidents. Safety supervision focuses on the control of the scaffold member spacing, scissors, bracing and wall parts must meet the overall stability requirements, the working layer must not be overloaded and must ensure the stability of the scaffold dismantling process.
      On-site construction machinery. As a supervision engineer, you should check whether the acceptance of on-site construction machinery meets the requirements, especially the material hoist, which is the main vertical transportation machinery, should be paid more attention to. Its ultimate goal is that all kinds of construction machinery should be operated according to the performance and use requirements specified in its instructions to prevent mechanical injury accidents. As the frame structure of the material hoist, it must meet the requirements of the bearing capacity. The transmission mechanism must meet the requirements of the work operation. The hoist should have the necessary safety protection devices to prevent the occurrence of high falls, frame collapse and mechanical injury accidents. Safety supervision focuses on the acceptance of the hoist before use after installation. After confirming that it meets the requirements, it should be put into operation. All kinds of safety protection devices should be tested to confirm their reliability. Hoists should be used according to regulations. Operators must be familiar with the performance of machinery. Electric machinery should comply with electrical installation regulations. Overloading of lifting machinery is strictly prohibited. All kinds of machinery must be repaired and maintained according to regulations. Before use, it should be tested to confirm that it meets the requirements.
      Earthworks: whether the protective measures for obstacles on the ground are complete; whether the protective measures for underground concealed objects are complete; whether the protective measures for adjacent buildings are complete; whether the drainage and flood control measures in the site area are complete; whether the earth excavation is completeHigh-temperature glass wool blanket wrapping protection, because the surface temperature of the fire pipe can reach 300 ° C to 450 ° C, most local thermal power plants use high-temperature glass cotton blanket protection wrapping for heating pipes. The use of high-temperature glass wool on directly buried pipelines also has good results, as shown in Table 4 below.

      Table 4 Test data of multi-screen composite thermal insulation direct buried pipe

       

      project	Under normal pressure
      	The surface of the tube at the moisturizing tube bracket		The outer surface of the tube at the insulation layer of the Paugne tube
      	Average temperature/℃	Heat flux/(F · -2)	Average humidity/℃	Heat flow in degrees/(W-2)
      Medium 300 ℃	44	108	36	109
      Medium 250 ℃	32	90	29	50
      Medium 200 ℃	26	61	27	43

      Whether the safety production measures of the construction organization and construction machinery are complete and complete; whether the stability support measures and calculation books of the slope of the foundation pit are complete and complete; whether the safety protection measures around the foundation pit are complete and complete.

      Formwork construction: Whether the load value of the formwork structure design calculation book is in line with the actual project, and whether the calculation method is correct; the formwork design should include the strength of the supporting system itself and the building and ground bearing capacity of the supporting formwork, including the structural components and the supporting system. Whether the design of the connecting parts is safe and reasonable, whether the drawings are complete, and whether the safety measures in the formwork design are comprehensive.

      (III) Safety supervision at the completion acceptance stage

      Supervise construction units to implement product protection measures and safety precautions.
      Examine whether the labor safety and health facilities are built and delivered for use at the same time as the main project and the labor safety and health facilities inspection report.
      Review the project indoor environmental inspection report.
      Prepare construction project safety supervision report.
      After passing the acceptance, the relevant engineering safety supervision materials will be transferred.