Problem with cooling of the reaction vessel – urgent (risk of cooling water entering the heating coil at 280°C)
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This post was last edited by sdwfsgyykai on 2018-9-3 at 15:38. The conditions are as follows: it is a slurry-bed reactor equipped with an agitator inside; it is heated through internal steam coils, and the operating temperature is around 390°C. However, when shutting down the reactor, since there is no means to cool it down, is it possible to direct the steam pipeline into water at 20°C in order to cool it? Would this cause any damage to the equipment? The interior of the equipment is made of 316L stainless steel, while the exterior is lined with carbon steel. I would appreciate some guidance – due to special manufacturing processes, feeding material into the reactor is not possible after it is shut down.
A semi-jacket can be installed on the outside of the equipment. Why is there a process in which high temperatures need to be suddenly reduced to low temperatures? Is it really necessary to cool it down so quickly? Stainless steel has a higher linear expansion coefficient compared to carbon steel; such a rapid temperature change can easily cause the weld to be damaged
I don’t want to achieve rapid cooling; I’d like to lower the temperature at a rate of 15°C per hour. But for now, the only option is to use industrial air on the coil – its specific heat is low, so it can carry very little heat. It seems that water injection is the only alternative, but I’m worried about potential damage to the equipment
If it is only for emergency cooling, considering installing a water spray system on the outer wall of the reactor is an option
It’s not an emergency cooling process; I want to control the cooling rate at around 15°C per hour. If spraying is used, what about insulation on the outside?
The temperature difference is too large; the equipment will get damaged
Cooling is achieved by condensate, or through external circulation with air cooling featuring a large heat exchange area. I’m not sure if it’s practical to use heat transfer oil for heating coiled tubes in your area
The risk is high for the following reasons: The operating temperature of the material is 390°C, which is quite high. If steam is introduced directly to the steam coil at 20°C to cool the material, the water will vaporize rapidly. Moreover, the steam coil itself is of a slender design, which leads to a mixture of steam and water flow; this in turn results in what is known as water hammer effect. The vibration of the coil becomes very severe； Additionally, there is a large temperature difference between the 20°C water and the material at 390°C; the equipment is made of 316L steel lined with carbon steel, and the expansion coefficients of these two materials differ, which results in certain stresses during the cooling process. The water hammer vibration, combined with the inherent stresses, and the fact that the coil is a small component, indeed result in a high risk. It is recommended to modify the equipment by setting up separate systems for heating and cooling (for example, one using coiled tubes and another using a jacket); steam should be used for heating, while circulating heat transfer oil should be used for cooling (to prevent boiling and thus avoid an increase in temperature as well as pressure buildup in the system due to the vaporization of the coolant)
1. Please first stop feeding material and adding steam. 2. Empty the contents. 3. Nitrogen purge. 4. Rinse in water. 5. Open the manhole. The above order is provided for reference