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Temperature Control

temperature flow variable speed pump vsd control valve control exothermic reaction

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#1 Mahdi1980

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Posted 15 April 2019 - 10:22 PM

Hi everyone,

 

I am going to control the temperature of a highly exothermic reaction via cooling water. The cooling water passes through the tubes located inside the reactor vessel to keep the temperature constant when the reaction is carried out.

I am not sure in such case if it is suitable to control the temperature by a control valve at the upstream of cooling coil or a variable speed pump will be more reliable to control the temperature of the process gas.

 

Although energy consumption is important, the system is pilot and we are not concerned about the cost of energy and most issue is having the best control on the process temperature.

Following the controlability, the initial cost might be also an important point to compare the VSD pump and control valve.

 

The cooling pipe size is 1" or 1 1/2" and the flow and head of the cooling pump can be considered around 5 m3/h and 10 mW respectively.

 

I appreciate your idea if you have some similar experiences.

 

 

Mahdi



#2 breizh

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Posted 16 April 2019 - 12:27 AM

Hi Mahdi ,

To me the most important is to guarantee the flow of cooling water based on an energy balance . 

On a safety point of view do you consider a back up plan in case of power outage , pump failure, agitator broken to prevent run away reaction , do you have all the safety devices in place for pressure built up ?  I'm just worried when people think about pilot plant .

 

hope this is helping you on your project.

good luck.

Breizh



#3 thorium90

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Posted 16 April 2019 - 02:00 AM

Great point on the safety..

 

The video below is quite relevant and I think it would be very enlightening as well.

 

https://www.youtube....h?v=C561PCq5E1g

 

 



#4 breizh

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Posted 16 April 2019 - 03:20 AM

hi ,

In addition to my previous answer .

hope this is helping you.

Breizh

Attached Files



#5 Mahdi1980

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Posted 16 April 2019 - 09:01 AM

Hi Mahdi ,

To me the most important is to guarantee the flow of cooling water based on an energy balance . 

On a safety point of view do you consider a back up plan in case of power outage , pump failure, agitator broken to prevent run away reaction , do you have all the safety devices in place for pressure built up ?  I'm just worried when people think about pilot plant .

 

hope this is helping you on your project.

good luck.

Breizh

 

Hi Breizh,

Thanks for your post. Actually, I have considered almost all the safeties such as pressure safety valve, High temperature switch to disconnect the feed to the reactor and a flow switch on the cooling system. 

The reactor is fluidized bed, so no agitator is there. 

My main focus is already on the suitable control of the temperature.

 

Regards 

Mahdi



#6 Bobby Strain

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Posted 16 April 2019 - 02:04 PM

May we ask what is the reaction temperature?

 

Bobby



#7 Mahdi1980

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Posted 16 April 2019 - 02:20 PM

May we ask what is the reaction temperature?

 

Bobby

600 K



#8 Bobby Strain

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Posted 16 April 2019 - 04:04 PM

Commercial operations with fluid beds and cooling, like acrlonitrile, make use of steam generating coils. This gives much better temperature control. Control is by varying the steam generation pressure.

 

Bobby



#9 breizh

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Posted 16 April 2019 - 09:26 PM

hi,

To add to Bobby's suggestion :

 

https://www.aiche.or...ep/20141121.pdf

 

hope this is helping you.

 

Breizh 



#10 Mahdi1980

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Posted 16 April 2019 - 10:50 PM

hi,

To add to Bobby's suggestion :

 

https://www.aiche.or...ep/20141121.pdf

 

hope this is helping you.

 

Breizh 

Hi Breizh,

and thanks for the file.



#11 Mahdi1980

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Posted 16 April 2019 - 10:59 PM

Commercial operations with fluid beds and cooling, like acrlonitrile, make use of steam generating coils. This gives much better temperature control. Control is by varying the steam generation pressure.

 

Bobby

Thanks Bobby for your advice. I saw such system in some industrial plant. However, it does not make sense to me.

I mean the control mechanism is unclear for me.

You mean when the cooling water comes through the coil in the reactor, it totally converts to steam?

The water pressure at the inlet of the coil might be at least 3 barg, so to be converted to a 3 bar steam it shall take the heat of reaction to reach 130-140 C water at dew point and take the remaining heat of reaction to convert from saturated water to the saturated steam.

Is it really happen? am I right?

Then how shall I control the temperature by the steam pressure? Can you explain more?

 

Mahdi


Edited by Mahdi1980, 16 April 2019 - 11:00 PM.


#12 Bobby Strain

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Posted Yesterday, 03:14 PM

The cooling tubing is arranged as in a boiler. A separator at the top and a mud drum at the bottom. Risers and downcomers. It operates as a natural thermosyphon with partial vaporization. But you need an experienced professional to help you.

 

Bobby






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