Stress analysis of O-element pipe after clearing of flue gas

článek v časopise - ostatní, Jost

angličtina

Equipment for cleaning of flue gas from undesired substances is used throughout power and other types of industry. This paper deals with damaging of O-element pipe designed to remove sulphur from the flue gases, i.e. damaging of the pipe after cleaning of the flue gas. This cleaning is conducted by spraying the water to the O-shaped pipe where the flue gases flow. Thus the sulphur binds itself onto the water and gets removed from the flue gas. Injection of cold water into hot flue gases, however, causes high stress on the inside of the pipe, which can gradually damage the O-element pipe. In this paper we are going to analyse initial injection of water into hot pipe all the way to stabilization of temperature fields and we shall determine the most dangerous places which shall be considered for low-cycle fatigue. Removing undesired harmful substances from flue gases is a very important industrial process that is constantly being subject to research activities in order to find out new methods of cleaning the flue gas. This is mainly caused by strict legislation on emission limits in developed countries. Among some of the undesired substances are sulphur dioxide, carbon monoxide, dioxins, solid substances, heavy metals, etc. Our Institute of Environmental and Process Engineering at Brno Technical University examined wet cleaning of flue gas when sulphur was removed and thus the content of sulphur dioxide in the flue gas was lowered. This experiment was carried out in O-element; we injected water into the flowing flue gas and the sulphur bound itself to the water and created sulphide. Since there was a temperature shock due to cooling of hot flue gas by cold water while carrying out this experiment, these pipes underwent a series of thermohydraulic and consequently stress analyses in order to determine its lifetime and how much it can be lowered by these experiments. Exhaust gases purification is interesting not only from chemical processes point of view, but also from mass change point of view as well as from thermal loading point of view. To solve the problem there was used the combination of computational methods so called FSI (Fluid Structure Interaction). The most demanding stage was two-phase flow simulation which takes place when cold water is injected into hot exhaust gases. It was very important to input correct values of computational model and different parameters. CFD results showed that heat exchange between exhaust gases and water drops took place almost immediately. It was also found out that this way of exhaust gases purification does not involve so high values of pressure drops and is more efficient compared to other types of purification. Determined thermal field distribution made it possible to find out stress state. This was done in ANSYS software for particular time moments. Stress changes were analyzed and the most loaded zones were determined. They were analyzed from low-cycle fatigue point of view further on. Components of stress tensor and their changes in particular zones were used for low-cycle fatigue analysis. Results showed that damage cumulation in all zones is neglectable. It is possible to state that for such loading conditions O-element will endure unlimited number of injections of water into flowing hot exhaust gases.

FSI analysis, O-element, pipe, stream mixing, head field, fatigue

NEKVASIL, R.

2008

3. 11. 2008

University of West Bohemia

Plzeň

1802-680X

Applied andComputational Mechanics

2

1

Česká republika

83

90

8