Recovery boiler dissolving tank steel structure optimization
Moisio, Santeri (2024)
2024
Konetekniikan DI-ohjelma - Master's Programme in Mechanical Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2024-11-21
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202411049808
https://urn.fi/URN:NBN:fi:tuni-202411049808
Tiivistelmä
The purpose of this thesis is to optimize the steel structures of 19 different size recovery boiler dissolving tanks. To optimize the structures, dissolving tank costs are studied to know which costs are the most significant and which should be emphasized in the optimization process. Design restrictions are studied and defined for the steel structure. Moreover, optimization algorithms are studied and tested before the final optimization.
The cost research was conducted using equations and general estimates from relevant literature and by interviewing three relevant European companies. Two different size dissolving tank steel structures from previous projects were studied from the cost and strength calculation point of views.
There are design restrictions based on geometry and strength calculations. The beams in the structure are restricted by their physical size. The beams and plates also have restrictions based on the maximum allowed bending stresses and displacements. The steel structures were divided into smaller entities for analysis. The 3D-models of the two different size dissolving tank steel structures were modified for this work using SolidWorks and FE-analyzed using Ansys. The structures were analyzed with three different load cases to see which ones cause the largest stresses and displacements. To avoid having to analyze all 19 steel structures with a time-consuming FE-analysis, the FEA-results of the two structures were compared to basic beam and plate equations to form simplified equations to calculate the rest of the steel structures.
As a result of this thesis, a system for optimizing the steel structures was developed. Excel based workbook with cost and strength calculations was created including the optimization algorithms coded with Excel VBA. The final optimization was conducted in two phases, first with Exhaustive Search and then with Particle Swarm Optimization. Depending on the dissolving tank size, the optimized steel structure was from 2 to 11 % cheaper compared to the benchmark.
The optimization process for steel structure presented in this work considers the four most significant cost factors: material, factory assembly, transportation, and on-site assembly. Design restrictions are based on general steel design rules. The results are not exact but directive since many simplifications and estimations were made to costs and design restrictions. On the other hand, due to these decisions it can be a useful and applicable optimization tool for multiple different kinds of steel structures.
The cost research was conducted using equations and general estimates from relevant literature and by interviewing three relevant European companies. Two different size dissolving tank steel structures from previous projects were studied from the cost and strength calculation point of views.
There are design restrictions based on geometry and strength calculations. The beams in the structure are restricted by their physical size. The beams and plates also have restrictions based on the maximum allowed bending stresses and displacements. The steel structures were divided into smaller entities for analysis. The 3D-models of the two different size dissolving tank steel structures were modified for this work using SolidWorks and FE-analyzed using Ansys. The structures were analyzed with three different load cases to see which ones cause the largest stresses and displacements. To avoid having to analyze all 19 steel structures with a time-consuming FE-analysis, the FEA-results of the two structures were compared to basic beam and plate equations to form simplified equations to calculate the rest of the steel structures.
As a result of this thesis, a system for optimizing the steel structures was developed. Excel based workbook with cost and strength calculations was created including the optimization algorithms coded with Excel VBA. The final optimization was conducted in two phases, first with Exhaustive Search and then with Particle Swarm Optimization. Depending on the dissolving tank size, the optimized steel structure was from 2 to 11 % cheaper compared to the benchmark.
The optimization process for steel structure presented in this work considers the four most significant cost factors: material, factory assembly, transportation, and on-site assembly. Design restrictions are based on general steel design rules. The results are not exact but directive since many simplifications and estimations were made to costs and design restrictions. On the other hand, due to these decisions it can be a useful and applicable optimization tool for multiple different kinds of steel structures.