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Flow Modelling of a FCC Slide Valve
for Oil Refinery Systems - 2

Simulation of the temperature field

Problem set-up

In order to verify the steel integrity, a two dimensional simulation of the valve thermal behaviour has been performed by using a spectro-element package. Six different lumped materials were used to model the valve heat conduction and temperature field: three high resistance refractory cements, two stainless steels, and one steel, as shown in the table below:

0	High density refractory lining + V anchors	2234	952	1.7
1	Carbon steel SA 516 Gr. 70	7860	544	38.5
2	Stainless steel Tp 304H ( t=732 oC )	8000	544	25.8
3	Stainless steel Tp 304H ( t=345 oC )	8000	544	22.3
4	High density refractory lining + X mesh	2640	865	3.7
5	Abrasion resistant refractory lining + X mesh	3132	887	7

The high density refractory lining is a very good insulating material and is used for lining the body valve in order to preserve it from the fluid temperature (around 1000 K). A different anchorage method is used depending on the valve position: V anchors or X mesh. The abrasion resistant refractory lining is less effective as an insulating material but it has shown very good wear resistant properties and it is used to line the most vulnerable zones. Its placement should be dictated by the flow field knowledge.

The SA516 Gr. 70 carbon steel is used for the body valve. Because of its properties it cannot reach a temperature higher than 620K. For the internal parts of the valve a high temperature resistant material like the stainless steel Tp 304H must be used.

To calculate the temperature field, two convective heat transfer coefficients were assumed for the valve internal surface - one for laminar zones and one for turbulent zones. Another convective coefficient was assumed for the external body which was supposed to be placed in a warm environment at 311 K.

Results

The temperature field in figure 1 demonstrates a correct design of the valve.

FIG. 1 - Fluid flow influence on valve body temperature

The maximum temperature in the internal surface of the steel was above the admitted 620 K. A critical zone of the valve is in the welded junction between the internal cone, where all the internal parts are fixed, and the valve body. Figure 1 shows a homogeneous temperature field, thus the thermal stresses are smaller in that zone.

Copyright © REMOSA spa 1998-2001 Last updated on May 18, 1998