A method for analyzing the base reaction force of a desulfurization tower and optimizing the foundation

Abstract

The present invention extends the existing calculation method of steel chimneys to the field of desulfurization tower analysis, provides a method for analyzing the base reaction force of desulfurization towers and optimizing the foundation, obtains accurate wind loads using the same outer contour, and obtains relatively accurate horizontal seismic loads using a simplified equivalent method in which internal and external equipment is segmented and aggregated and added to the cylinder wall considering the increase in stiffness. The foundation optimization focuses on the guiding ideology of reducing the zero-stress area against overturning, increasing the counterweight, and reducing the amount of reinforcement and piles.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural design, and particularly relates to a method for analyzing the base reaction force of a desulfurization tower and optimizing the foundation. Background Art

[0002] As a tall and thin-shell cylindrical equipment, the mechanical analysis of a desulfurization tower is very complex. It often puzzles every supplier to provide accurate equipment base reaction forces to the design institute as a standard equipment or non-standard equipment supplier. Because the base reaction forces of tall equipment must consider the influence of horizontal wind and horizontal earthquake, and there are differences in wind and earthquake in different site conditions in different regions. How to quickly and simply obtain accurate tower bottom reaction forces according to specific projects for foundation design has always been a major problem in the industry.

[0003] Currently, when designing a desulfurization tower, equipment manufacturers only focus on the equipment itself, and the structure for installing the equipment is designed by the design institute. The calculation of the structure requires the equipment manufacturer to provide equipment loads. For small equipment, generally only parameters such as the self-weight of the equipment need to be provided. However, for tall and high equipment, due to different winds and design earthquakes in different regions and sites, the shear force and bending moment at the equipment base are quite different, and they must be calculated specifically for each project and then provided. These parameter calculations that are more specialized in building structures are very difficult for equipment manufacturers to handle, and many manufacturers estimate, that is, there are problems at the source of structural safety. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to simplify the complex and professional calculation of the desulfurization tower into a special "steel chimney", and use the relatively mature chimney calculation theory and software to quickly handle the problems of desulfurization tower design. The complex desulfurization equipment is simplified into a steel chimney with variable diameter, variable thickness, and variable material along the vertical direction, and the internal and external equipment and platforms are simplified into attached masses. Then, it is abstracted into a multi-particle vibration system arranged vertically for calculation according to the idea of designing a steel chimney.

[0005] The method for analyzing the base reaction force of a desulfurization tower and optimizing the foundation according to the present invention, wherein the calculation of the desulfurization tower refers to the steel chimney, and the calculation and analysis are carried out by using the methods and tools for calculating the steel chimney through simplified equivalent processing; the processing steps of the method include:

[0006] Step 1: Refer to the structural drawings of the desulfurization tower and abstract and simplify them into a mechanical model;

[0007] Step 2: Collect the weights and attachment positions of the internal and external attachments of the desulfurization tower; the attachments are loaded as additional loads at the corresponding heights and become part of the mass of the particles in the vertical multi-particle vibration system;

[0008] Step 3: Collect the data required for calculating the wind load for calculating the horizontal wind load;

[0009] Step 4: Collect the parameters of the temperature effect for the calculation of the temperature stress combination of the tower body, and review the design value of the strength of the cylinder wall;

[0010] Step 5: Obtain the axial force, shear force, and bending moment under the dead load, live load, wind load, and seismic load at the tower bottom, and perform combined calculation to configure anchor bolts and foundation;

[0011] Step 6: Perform internal force combination, try to design a natural foundation by increasing the counterweight. For the structural thickness calculation, the reinforcement is close to the minimum reinforcement ratio, and in other ranges, the concrete grade is reduced according to the counterweight for secondary pouring; when designing a pile-raft foundation, reduce the inner piles and increase the counterweight to design ordinary piles; when designing uplift piles, adjust the counterweight to reduce the cost of uplift piles.

[0012] Preferably, the method selects general finite element software or small calculation tools for simulation analysis; it can be calculated by general finite element software such as SAP2000, or the foundation reaction force and anchor bolt configuration can be obtained by using small calculation tools such as QY-chimney.

[0013] Preferably, in Step 2, the wet desulfurization slurry is not used for combined calculation as the live load of the tower body; in Step 5, the slurry at the bottom of the wet desulfurization tower needs to be used as the live load for foundation design and participate in the combination.

[0014] Preferably, in Step 1, the desulfurization tower is segmented according to different outer diameters, different wall thicknesses, and different materials. When the length of the segment with the same parameters is too large, it is further divided. The flexural stiffness of the tower body is calculated from the height, wall thickness, and outer diameter of each segment, and the desulfurization tower is simplified into a multi-particle vibration system with multiple concentrated masses along the vertical direction to calculate the dynamic characteristic values of the desulfurization tower;

[0015] Preferably, the internal and external attachments in Step 2 include maintenance platforms, stairs, and internal desulfurization equipment; these are used as additional loads and applied at different height segments, becoming part of the mass of the particles in the vertical multi-particle vibration system. The internal steel platform in the desulfurization tower has an impact on increasing the stiffness of the tower barrel, and the seismic force can be amplified by appropriately reducing the period; note: the wet desulfurization slurry cannot be used for combined calculation as the live load of the tower body; the relatively accurate base shear force and bending moment under horizontal earthquake can be obtained through horizontal earthquake calculation;

[0016] Preferably, in Step 3, find the ground roughness, basic wind pressure, and instantaneous wind speed at the project location, and it can be calculated according to QY-chimney can automatically calculate the wind pressure height change coefficient μ z 、wind shape coefficient μ s 、wind vibration coefficient β z and the judgment of the participation of lateral wind vibration in the combination; calculate the base shear force and bending moment of the desulfurization tower under the action of horizontal wind load;

[0017] Preferably, the parameters of the collection temperature in step 4 include the flue gas temperature in the tower, the highest temperature in summer, the lowest temperature in winter, the sunshine temperature difference, and the lowest daily average temperature difference.

[0018] Preferably, in step 6, the additional counterweight required for the basic anti-overturning design is cast in a second time with a reduced concrete grade according to the plain concrete design, ensuring that the foundation is only reinforced with the minimum reinforcement ratio. By reducing the number of inner piles, the vertical pressure on the outer piles is increased to reduce the counterweight and pile reinforcement.

[0019] Once the design institute or the EPC general contractor obtains the reaction force of the desulfurization tower base, they can proceed with the lower structure. If the desulfurization tower is seated on a subgrade foundation, a natural foundation should be considered first. Try to design the foundation counterweight and embedment depth, and control the proportion of the zero stress zone at the bottom of the foundation under anti-overturning. In areas with high foundation bearing capacity, generally, the method of increasing the foundation embedment depth and setting a foundation counterweight is adopted. The foundation can be designed as a thick circular plate (usually more than 2 meters thick) to meet the bearing capacity requirements. To reduce the cost, the thick circular plate is divided into a stressed plate thickness and a counterweight plate thickness along the thickness direction. The stressed plate thickness should be such that the calculated reinforcement ratio is close to the structural reinforcement ratio. The circular plate part for the counterweight has its concrete grade reduced and is cast as plain concrete without reinforcement in a second pour.

[0020] When the bearing capacity of the natural foundation cannot be met after increasing the counterweight and embedment depth, it is designed as a pile raft foundation. The outer piles should be as close as possible to the circumference where the anchor bolts are located. By adjusting the counterweight and reducing the number of piles inside the circular plate, the vertical pressure borne by the outer piles is increased, and ordinary piles that do not bear tension are preferably designed (the cost of ordinary piles is much lower than that of tension piles). When tension piles must be designed, optimizing the counterweight and the reinforcement ratio of the tension piles can reduce the cost.

[0021] Compared with the prior art, the present invention has the following effects: The present invention provides a method for calculating the reaction force of the base of standard or non-standard desulfurization towers or similar high-rise steel cylinder structures under different regional and site conditions, which can simply and quickly provide the seller for foundation design and give design techniques for reducing the foundation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of two desulfurization towers required to be designed for the EPC project of the flue gas purification of the coal-fired boiler in Yanggang Thermal Power, Guoyang County. SPECIFIC EMBODIMENTS

[0023] For the Anhui Guoyang Yanggang Cogeneration Project - 2, the EPC project of the flue gas purification of the coal-fired boiler in Yanggang Thermal Power, Guoyang County, requires the design of two desulfurization towers. The height of Tower 1 is 45.7 meters, and the height of Tower 2 is 80 meters. The construction methods of the lower parts with the same height are the same. Tower 2 is 80 meters high and Tower 1 is 45.7 meters high. The former has a slender chimney with a diameter of 3 meters and a thickness of 8 mm and a length of 39.3 meters at the top. The slurry volume in the desulfurization tower is 280 m 3, with a mass of approximately 336 t and a depth of 7.5 m. The empty tower of the 1# desulfurization tower is about 182 t, and the empty tower of the 2# desulfurization tower is about 220 t. The basic wind pressure in this area is 0.45 kN / m 2 ; the seismic fortification intensity is degree 7 (0.10g), group II; the site category is III. See the appendix for the outer contour, wall thickness, maintenance platform, ladder, etc. of the tower body Figure 1 . The calculation of the desulfurization tower refers to that of the steel chimney. Through simplified equivalent treatment, the methods and tools for calculating the steel chimney are used for calculation and analysis. After calculation and analysis by QY-chimney, the bottom reaction force of the tower can be obtained as shown in Table 1

[0024] Analysis of the calculation results of this project will reveal that

[0025] 1. The horizontal overturning moment and shear force are for wind control, that is, the horizontal seismic effect is less than the wind effect; in high-intensity seismic areas such as Xichang and Shizuishan in Ningxia, it may be completely different

[0026] 2. The influence of horizontal earthquake on the 2# high tower is actually lower than that on the 1# low tower because there is a slender steel cylinder with a diameter of 3 m and a height of 39.3 m at the top of the 2# high tower, which increases the period and thus reduces the horizontal seismic force

[0027] 3. This project is a wet desulfurization tower. The self-weight of the slurry at the bottom of the tower should not be included in the combination during the calculation of the tower body. Otherwise, it will lead to a decrease in the overturning moment and fewer anchor bolts. The underground foundation design should consider the slurry weight as a live load and load it on the foundation for checking. Otherwise, the axial force including the live load combination will be too small, which may lead to an unsafe foundation

[0028] It can be seen that there are great differences between tall equipment and low equipment. The calculation of tall equipment under wind and seismic conditions is complex and cannot be ignored; due to different wind and seismic fortification intensities in different regions, the bottom reaction forces of the same equipment vary greatly in different regions and even different sites. When the same equipment is used in different projects, specific engineering analysis should be carried out to ensure safety and reliability

[0029] Table 1

[0030]

Claims

1. A method for analyzing the base reaction force of a desulfurization tower and optimizing the foundation, characterized in that: The calculation of the desulfurization tower refers to that of a steel chimney. Through simplified equivalent treatment, the methods and tools for calculating steel chimneys are used for calculation and analysis. The foundation is designed separately by counterweight and structure to reduce the cost; The processing steps of the method include: Step 1: Refer to the structural drawings of the desulfurization tower and abstractly simplify them into a mechanical model; Step 2: Collect the weights and attachment positions of the attachments inside and outside the desulfurization tower; the attachments are loaded as additional weights at the corresponding heights and become part of the mass of the particles in the vertical multi-particle vibration system; Step 3: Collect the data required for wind load calculation for horizontal wind load calculation; Step 4: Collect the parameters of temperature action for calculating the temperature stress combination of the tower body and review the design strength value of the cylinder wall; Step 5: Obtain the axial force, shear force, and bending moment under dead load, live load, wind load, and seismic load at the tower bottom, and combine the calculations to configure anchor bolts and the foundation; Step 6: Combine internal forces, try to design a natural foundation by increasing the counterweight, calculate the reinforcement of the structural thickness to be close to the minimum reinforcement ratio, and pour the second time with a reduced grade according to the counterweight in other ranges; when designing a pile raft foundation, reduce the internal piles and increase the counterweight to design ordinary piles; when designing tension piles, adjust the counterweight to reduce the cost of tension piles; In the first step, the desulfurization tower is segmented according to different outer diameters, different wall thicknesses, and different materials. When the length of the segments with the same parameters is too large, it is further segmented. The flexural stiffness of the tower body is calculated from the height, wall thickness, and outer diameter of each segment, and the desulfurization tower is simplified into a multi-particle vibration system with multiple concentrated masses along the vertical direction to calculate the dynamic characteristic values of the desulfurization tower; the internal and external attachments in the second step include maintenance platforms, stairs, and internal desulfurization equipment; the internal steel platform in the desulfurization tower has an impact on increasing the stiffness of the tower barrel, and the earthquake force is increased by appropriately reducing the period; relatively accurate base shear force and bending moment under horizontal earthquake can be obtained through horizontal earthquake calculation; in the third step, the ground roughness, basic wind pressure, and instantaneous wind speed at the project location are found, and the wind pressure height change coefficient of different segments is calculated , wind shape coefficient , wind vibration coefficient , to calculate the base shear force and bending moment of the desulfurization tower under the action of horizontal wind load; the parameters for collecting the temperature action in the fourth step include the flue gas temperature in the tower, the highest temperature in summer, the lowest temperature in winter, the sunshine temperature difference, and the lowest daily average temperature difference; in the sixth step, the additional counterweight required for the anti-overturning design of the foundation is cast in a second time with a reduced grade according to plain concrete design to ensure that the foundation is only reinforced with the minimum reinforcement ratio, and the vertical pressure of the peripheral piles is increased by reducing the number of internal piles to reduce the counterweight and pile reinforcement 2. The method according to claim 1, wherein: The method selects general finite element software or small calculation tools for simulation analysis.

3. The method according to claim 1 or 2, characterized in that: In Step 2, the wet desulfurization slurry is not combined and calculated as the live load of the tower body; in Step 5, the wet desulfurization slurry at the tower bottom needs to be included as the live load for foundation design in the combination.

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