1 Project Summary
The dust removal project of a steel mill needs to set up a chimney according to the professional requirements of ventilation. The chimney height is 45 m, the diameter is 46m, and the highest temperature is 40C. Base wood wind pressure 0.35kN /m, ground roughness class B, earthquake fortification intensity 6 degrees, earthquake acceleration 0.05g, earthquake group is the first group, site category is class I.
2 Design Essentials of Free-standing Steel Chimney
2.1 Material Selection
Steel pancetta is divided into tower type, cable type, self-supporting pancetta. According to the engineering conditions, combined with the actual situation, this design uses steel chimney. The steel chimney, inspection platform and rotary ladder are all made of Q235B, whose quality should conform to the provisions of the current national standard GB/T 700 vegetarian structural steel.
2.2 Load and action
1) Load and action of chimney :a. Constant: structural weight, soil pressure, pulling force of wire. b. Live load: wind load, smoke temperature action, repair load, platform live load, seismic action, foundation settlement, etc
2) Wind load. a. The basic wind pressure of this project is 0.35kN /m. b. Self-supporting steel chimney, when the slope is not J2%, should be carried out according to the different conditions of the noord wind vibration check calculation; The Reynolds number, critical wind speed and wind speed at the top of the smoke plume for cross-wind vibration verification shall be calculated according to the formula in the Code for Design of Smoke Charts. When the Reynolds number is less than 3x10 and the wind speed at the top of the smoke diagram is greater than the critical wind speed, the subcritical transverse wind resonance load can not be calculated for the free-standing steel chimney. When the Reynolds number is no less than 3.5 x 10 and 1.2 times the wind speed at the top of the chimney is greater than the critical wind speed,
The resonant response should be checked. When the Reynolds number is no less than 3 x10 and no more than 3.5 10, the transverse resonance load may not be calculated. When checking the crosswind resonance, the most adverse resonance response that may occur under the condition that the wind speed is less than the basic design wind pressure should be calculated.
3) Seismic action. a. When the seismic fortification intensity is 6 degrees and 7 degrees, the vertical seismic action can not be calculated; when 8 degrees and 9 degrees, the vertical seismic action should be calculated. b. The horizontal seismic action can be calculated according to the mode decomposition response spectrum method stipulated in the current national standard GB50011 building resistance design code
2.3 Calculation Points
1) The relationship between the diameter d of the self-supporting steel chimney and the corresponding position height h should be determined after calculation according to the strength and deformation requirements, and should meet the requirements of hs30d: otherwise, measures should be taken, such as expanding the diameter of the lower part of the chimney or not taking shock absorption measures.
2) In the design of white vertical steel chimney, the following calculations should be made :a. Steel chimney strength calculation under the action of bending moment and axial force. b. Checking of local stability of chimney under bending moment and axial force. c. Check calculation of overall stability of steel chimney under small bending moment and shaft action. d. Calculation of maximum tension of ground bolt. e. Local compression of steel chimney bottom foundation should be calculated. f. Hole stress calculation of flue inlet.
3) The minimum thickness of the plain wall of the steel chimney should meet the following requirements :a. When the height of the smoke map is not more than 20 m, the minimum thickness of the plain alarm is 4.5 +. When the height of smoke map is greater than 20, the minimum thickness of simple wall is 6 +C. Where, C: is the corrosion thickness margin, C=2 mm when there is insulation layer; C=3 mm when there is no insulation layer.
4) When there are heat insulation requirements, steel smoke pipe should be equipped with heat insulation layer
In addition, due to multiple intensification, the project is less economical than conventional projects that are not overrun. Therefore, in the early stage of the project, the architectural design should try to avoid such serious irregularities as high elevation conversion and tower offset. Although this plan has been successfully realized through various measures, it has to be said that it is not a good choice.
Hebei Pude Yuelan Environmental Protection Equipment Co., Ltd. is an enterprise engaged in the development and production of industrial chimneys, the company focuses on the development and production of industrial chimneys.
Headquartered in Jingxian Development Zone, Hebei Province, the company has a registered capital of 60 million yuan, covers an area of 9.60000 square meters, of which the building area is 2600 square meters. The main products include self-supporting smoke, sleeve smoke, tower chimney, east smoke, cable smoke, stainless steel chimney, glass steel chimney, mobile compressed garbage bin, horizontal compressed garbage station, hook arm transfer truck, butt type garbage truck and dozens of products. The company has 128 employees, including 8 experts and engineers with master's degree or above, 60% of the employees with bachelor's degree or junior college degree, all kinds of technical personnel 26 people, 60 people special personnel, the company has a number of domestic offices and after-sales service institutions, can provide technical support and product services at any time.
The company's production equipment advanced, strong technical force. Has more than 50 sets of domestic advanced production equipment, including foreign, domestic CNC production lines 6; Hot-dip galvanizing adopts the galvanizing technology and process of Gimeco Company in Italy, and its technical level and production capacity are at the advanced level in China.
After years of development in chimney and municipal waste treatment equipment industry, the company has become a well-known brand in the industry. Through the cooperation with domestic and international design institutes, colleges and enterprises to continuously improve the enterprise's scientific research and development ability. And has cooperated with many universities and reached strategic cooperation with petrochina, Sinopec, Huadian, Huaneng and other enterprises.
In recent years, in order to solve the problem of large-caliber smoke, the company has established a technical cooperation relationship with Beijing Jiaotong University, and invested a lot of manpower and material resources to develop the "precast factory, on-site construction" steel corrugated chimney and urban waste environmental treatment products. At present, the pipe diameter range of the company's products is 0.5m-20m, and the annual production capacity is 660,000 meters.
The company always adhere to the "quality, user" of the enterprise purpose, do not ask for the number of projects, just do the project to make good quality principle, products have been promoted in the project use. Today, the company's products still maintain zero defects, zero complaints, zero accidents, by the owners, construction units of the consistent praise, and establish a long-term cooperative relationship.