Finite element 3D thermal and thermo-structural analysis of the catalytic cracking device for various operating modes of the reactor and the regenerator. Estimation of thickness of elements of structures; static and cyclic strength estimation
Area of expertise:
|Keywords||Reactor, regenerator, multilevel submodeling, thermal stress state, cyclic strength|
|Programs in use||SolidWorks, ANSYS|
In 2006-2007 Computational Mechanics Laboratory (CompMechLab) by JSC Neftehimproekt request executed multivariate analysis of 3D thermal and thermal-stress state of catalytic cracking device.
Catalytic cracking deviceis one of the major components of the oil-and-gas industry equipment complex. It participates in technological process of oil fractions splitting into base components of high-quality aviation and automobile gasolines.
Catalytic cracking device’s general view
This device consists of two basic elements: a reactor and a regenerator connected with catalyst pipeline.
The basic elements forming catalytic cracking device are cylindrical sidewalls, conic elements, bottoms and covers of different vessels and devices (made of steel) and also pipelines (catalyst pipelines), connecting pipes, compensators, stopper plugs and other devices working at high temperatures and pressures.
For perception of displacements caused by temperature the lens compensators of universal type are installed on catalyst pipelines.
Lens compensator with pantograph
While in service the device undergoes mechanical loads(wind load, internal pressure, dead weight and internal elements weight) and thermal stresses caused by technological process.
In the frameworks of the current project 3D geometrical, finite element (FE) and mathematical models considering all basic elements of the structure including reactor, regenerator, mixing chamber, suppression chamber, catalyst pipelines, compensators, constant effort support elements, pilot support elements, slide gatesand internal devices are developed and analyzed.
The fundamentally new hinged system's (with set stiff characteristics) computational model has been developed for correct compensators' work modeling. This model allows considering possible relative displacements and turns of catalyst pipelines' partsin the set directions (arising while device is in service).
For the structure 3D thermal stress state analysis there was used a FE shell model with two-layer structure: the external one is steel and the internal one is lining (concrete). Internal equipment's weight was modeled by means of point masses placed taking dimensions and areas of equipment's bearing or suspension into consideration.
Structure’s computational model with basic loading types indication
On the basis of developed FE models:
Device's elements (for various operating modes) 3D thermal stress state analysis is carried out, admissible thickness (satisfying strength conditions according to Russian standards and nuclear norms) are specified.
Catalytic cracking device flow under wind action
Total displacement distribution in the computational mode
Efforts and moments, acting in the areas of
- pilot support elements, of catalyst pipelines' connecting pipes attachment to the suppression chamber, reactor, regenerator cases;
- slide gates' connections with catalyst pipelines
The constructional and technological parameters, allowing reducing the level of the stresses arising in the most dangerous elements (in the view of strength) are specified. These are:
- stiffnesses of compensators providing the efforts' (acting upon connecting pipes while controlling admissible relative compensators' displacements and admissible efforts in pilot support elements) reduce;
- efforts, acting in flexible support elements;
- technological clearances in pilot support elements (while controlling admissible efforts in support elements).
Constant effort support elements arrangement and variation parameters
Using multilevel submodeling method the connecting pipes' strengthening elements' thicknesses (taking welded seams into consideration) are specified, the constant effort support elements' geometrical dimensions are selected, thermal stress state of the reactor's top part (taking welded seam in the area of plenum attachment to the case) is specified.
Models for the multilevel submodeling
The reactor top part cyclic strength analysis is performed for operating modes "Start-up - working mode-Stop" sequence.
Area of cyclic strength analysis (2nd level submodel)
Results of the analysis for the operating model