Journal of Chongqing University (Natural Science Edition) finite element analysis of spherical joints of blast furnace top gas pipelines 蹇 Kailin", Zhu Xichun, Lin Baoru (College of Civil Engineering and Architecture, Chongqing University, Chongqing 400044, China) Out of the law of stress distribution, the safety of the spherical shell

Journal of Chongqing University (Natural Science Edition) finite element analysis of spherical joints of blast furnace top gas pipelines 蹇 Kailin", Zhu Xichun, Lin Baoru (College of Civil Engineering and Architecture, Chongqing University, Chongqing 400044, China) The law of stress distribution is published, and the safety of the spherical shell is evaluated.

39: A 2500m3 blast furnace of a plant is planned to adopt a spherical node structure at the intersection of the top gas pipeline. The structure is large and complex in total, and the connecting ball has an inner diameter of 5500mm and a thickness of 30mm. Four uniformly distributed risers with an inner diameter of 2000mm are inclined upwardly to the center of the ball with an axis of 45*, and a down tube with an inner diameter of 3000mm. It is led out from the top of the ball in the 45 direction, descending to the gravity dust collector, and a discharge tube having an inner diameter of 1500 mm is led out from the dome in 20 directions and supports the release valve platform. The spherical shell and pipe are made of steel and the inner surface is sprayed with a 50 mm thick insulation layer. The normal working pressure of the spherical shell is 0. It is normal pressure. When the normal working, the furnace gas temperature is <600 °C when the accident is 200, the normal temperature is when the wind is off, the seismic fortification intensity is 7 degrees, and the basic wind pressure is 600Pa. The highest recorded in the 31 years. The temperature is 38. The low temperature is 10. The structure is beautiful and the connection is compact. It can ensure the airflow is smooth and the construction is convenient. It can also reduce the overall height of the gas pipeline and save the blast furnace floor space. In the intersection of the blast furnace top gas pipelines, the spherical joint structure is adopted, which is the first time in China. Obtain the stress and strain distribution law of the new structure under design load, study the edge effect of the intersection of gas pipe and spherical shell, and identify the problems that should be paid attention to in design and construction, which is crucial to the success of design and application. of.

1 Finite element calculation of spherical joint shell 1.1 Finite element mechanical model of spherical shell calculation Since the length dimension of the riser and the downcomer is much larger than the diameter of the spherical shell, the spherical shell is simulated by the shell element, and the pipeline is separated by the tube unit. However, the pipe and the spherical shell are intersected. In order to ensure the accuracy of the spherical shell stress calculation and to facilitate the division of the grid and the application of the load, the length of the pipe connected to the spherical shell is also a small length and is also simulated by the shell element. The entire structure is divided into 2261 nodes, 2688 shell units and 47 tube units. Its entire structural grid is shown in Figure 1. It is a grid diagram of a small section of a pipe that is separated by a shell element and a shell unit that intersects the spherical shell.

The overall grid spherical shell and small section of the pipeline grid: 199SH2r02 situation maximum equivalent stress (Mpa) position no wind no earthquake windy no earthquake windy earthquake no wind no earthquake windy no earthquake left rear descending tube and spherical shell junction Same as above (when the wind direction is the maximum in the X direction), the same as above (when the wind direction and the seismic force are both in the X direction), the wind has the earthquake. The left rear descending tube and the spherical shell are the same as above (when the wind direction is +Y direction) The maximum stress is the same as above (when the wind direction and the seismic force are both in the +Y direction) 12 boundary conditions. Since the whole structure is supported by 4 ascending pipes, the downcomers are connected with the gravity dust collector, and the 4 risers are viewed from the lower part. As the solid support end, the part connecting the down pipe and the gravity dust collector is replaced by equal rigidity, and then the bottom part is regarded as the fixed end treatment, that is, the translational and rotational degrees of freedom of the three directions are constrained.

1.3 The load shall be calculated for each single load as follows: the weight of the spherical shell and the pipe, the weight of the insulation material sprayed on the spherical shell; the weight of the relief valve platform: the temperature change at the drop pipe and the discharge pipe: Absolute temperature rise is 100*C, absolute temperature drop is a wind load: basic wind pressure is 600Pa, acting along the horizontal plane X, Y; seismic load: the seismic action is equivalent to static load, applied as follows: The horizontal seismic force of the falling pipe and the spherical shell is 110KN, the bending moment is 1070KN*m, the horizontal seismic force of the four rising pipes and the spherical shell is 161KN, the bending moment is 1630KN*m, and the venting tube and the spherical shell phase The horizontal seismic force is 51KN and the bending moment is 264KN*m. When these loads are applied to the structure, it is necessary to multiply the corresponding load partial coefficient: 1.20 for the dead load and 1.00 for the live load. The seismic load is taken as 1.30. Under the blast furnace off-state and normal working conditions, the load on the structure is different. Therefore, the stress generated on the structure is calculated for each individual load, and then the load combination is combined to obtain the stress distribution of the spherical shell under various load combinations. The load combinations considered are: blast furnace state of the wind, a spherical shell and no internal pressure of the pipeline, the absolute temperature drop of the structure is taken as a 50. and all other loads are included.

In normal working condition, the inner shell of the spherical shell and the pipeline has internal pressure, and the absolute temperature rise of the structure is taken as 100. It is included in all other loads.

The following three load combinations are considered for the above two load states: no wind and no earthquake, no wind and no earthquake, and wind and earthquake.

For the combination considering seismic action, the load combination coefficient is taken as follows: both wind and earthquake effects are considered in both directions of X and Y.

1.4 Calculation results of the spherical shell The spherical shell bearing part is steel. Therefore, after the static calculation by the finite element program, the equivalent stress value of each point is given by the fourth strength theory, and the stress cloud of the spherical shell is drawn to make the spherical shell. The stress distribution is clear at a glance.

The stress cloud diagram of the spherical shell in the presence of wind and earthquake under normal working conditions is given. For the sake of brevity, the maximum equivalent stress of the spherical shell in various states is listed in Table 1. It can be seen that the spherical shell stress under each working condition is not large, and it occurs at the edge of the boundary between the left rear descending tube and the spherical shell.

Under normal conditions, there is a wind and earthquake. The bottom view of the stress distribution of the spherical shell can be seen from the above results. The stress of the spherical shell is the largest when there is no wind and no earthquake, but it does not reach the bending limit of the material.

Table 1 Maximum equivalent stress of the spherical shell Blast state of the wind Normal working condition Upward pipe load condition Down pipe Left front left rear right front right rear no wind no earthquake one 79. Windy no earthquake one 95. Windy earthquake no wind no Earthquake - 93.46 Wind, no earthquake, wind, earthquake, 128. 2 Finite element calculation of gas pipeline system 2.1 Finite element mechanical model of pipeline system calculation In order to more accurately analyze the stress on the pipeline, the pipeline was specially calculated by finite element method. The spherical shell (ie, the spherical node) in the center of the gas pipeline system is regarded as a concentrated mass, and the four ascending tubes, descending tubes and dissipating tubes are respectively delivered to the center of the sphere at a certain angle, that is, the concentrated mass portion, together forming a space tube Frame structure. Using the tube unit simulation in the SAP5 program, a total of 58 tube units, 59 nodes. The boundary conditions are the same as the aforementioned spherical shell mechanics model. Except for the weight of the spherical shell as the concentrated force, the other loads are the same as the spherical shell mechanical model.

2.2 Calculation results of gas pipeline system Table 2 The maximum combined stress (MPa) of the pipeline system is calculated by the same load combination of the pipeline system. The axial force of each pipe element, the shear force, bending moment and torque value in the two local coordinate directions are obtained. At the same time, the combined stress of each unit is calculated. The maximum stress values ​​of the pipes in the state of rest and normal operation are given here, as shown in Table 2.

3 Conclusions Through the finite element calculation of the spherical joint of the blast furnace top gas pipe, the stress distribution law of the structure is obtained; the intersection of the descending pipe and the spherical shell is abruptly shaped due to the sudden change of shape; the spherical joint is combined with various applied loads. Next, the upper spherical surface is pulled and the lower portion is pressed. After the internal pressure is applied, the upper spherical tensile stress is faster and longer; the finite element calculation results show that the spherical joint is feasible at the intersection of the pipelines. The diameter of the spherical shell is 5500mm, and the wall thickness is 30mm. Under the unfavorable combination of various loads, the entire structural stress is less than the design strength, which can ensure safe use.

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Chemical name
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