Refractory Lined Autoclave Finite Element Analysis

A refractory lined autoclave finite element analysis was performed for a client in the Chemical Industry. These types of processes often require the use of pressure, elevated temperature, and acids. To accommodate such harsh environments, refractory lined carbon steel vessels are used.

The composite design of the vessel includes refractory brick, mortar, membrane system and steel shell. The vessel is approximately 83 feet long and outer diameter of 16 feet. Inside the steel shell are three layers of refractory brick. Between the steel shell and outermost brick contains an elastomeric membrane, intended to accommodate geometric variations, as well as brick-to-shell differential thermal expansion.

The vessel is divided into a number of compartments, each with an associated agitator. The unit processes materials on a continuous basis. Both liquid and gas phases exist within the Autoclave. Various size nozzles are located on the bottom and top of the vessel for inlet and outlet of liquid and gas.

The important parameters in the design of the autoclave are temperature and stress. Each material of construction has unique properties with respect to temperature. Stresses in the various components of the Autoclave must be kept within certain limits to minimize the potential for a structural failure. The design evaluation method used for the steel shell was that of the ASME Boiler and Pressure Vessel Code. The refractory liner is a brittle material. Such materials, when subjected to multi-axial compressive stress states can have stresses that exceed the ultimate compressive stress.

Finite element analysis was used to determine structural integrity of the vessel under various operating conditions. Thermal and structural analyses were completed for each of the Autoclave finite element models. The thermal analyses were performed to determine the steady-state temperature distributions through the refractory lining, in the steel shell and the wall of vapor nozzle. These temperatures were used as thermal loads in the structural analyses, which also considered internal pressure and chemical expansion effects.

O’Donnell Consulting Engineers Performs Engineering Analysis on Various Materials including Steels, Alloys and Refractory.