7 replies to this topic

[Jackwill]

So I need to design the heating and cooling system for a batch plant (pharmaceuticals).

Majority of the unit operations are jacketed vessels (reactors, filters etc.)
How can I heat up and cool down a single operation?
For example, I need to heat up 'reactor 1' to 100 degrees then gradually cool it down to -10 degrees.
I was thinking of using dowfrost as the heat transfer fluid as it has a big temperature range so could do both, but how exactly would the dowfrost be heated up to 100 degrees?

For the cooling process some sort of chiller/fridge could be used.

Are there better options I haven't thought of?

Beginner chemical engineering student so please spare my lack of knowledge.

Kind regards
J. Will

[samayaraj]

Hi jackwill,

 

Find attached the sketch for easy understanding.

 

Heating:

 

You can use LP steam/ pressurized hot water/ electric heater to heat the heat transfer fluid. In general, plants have LP steam with that you can heat it comfortably. If you do not have LP steam, economic way is go for hot water generator or electric heater. There may be a problem with electric heater, as the surface temperature of heater is of high degree and it may oxidize the heat transfer fluid. Check for compatibility with electric heater.

 

Cooling & chilling:

 

While bringing the hot fluid to -10 deg. C, you cannot do it directly with a chiller. Before that, you need a cooler to cool the fluid from 100 deg. C to room temperature then you have to admit it into the chiller. You can use either water cooler/ air cooler as cooler.

Attached Files

•  heating and cooling system.png   10.98KB   6 downloads

Edited by samayaraj, 16 February 2016 - 02:00 AM.

[Jackwill]

X

Thanks for your response. I was thinking of having two separate loops, one for heating and the other for cooling.

Also, if I were to use LP steam directly to heat the reactor through the jacket, would there be contamination in the jacket when the cooling fluid is put through? If so, is there any way to overcome this?

[samayaraj]

You cannot admit steam in place of heat transfer fluid for heating. Heat transfer fluid should be a separate loop. If not, oil carry over will be there in condensate or more moisture content will present in heat transfer fluid which will freeze during chilling.

[samayaraj]

In another way, you need to have special reactor where steam and heat transfer fluid will pass in different loops. Like a helical coil, two different coils placed inside or outside the reactor.

Edited by samayaraj, 16 February 2016 - 01:40 PM.

[Art Montemayor]

Jack:

 

First some advice for a young, ambitious Chemical Engineering student:
Never take any criticism, or corrections from a senior engineer as negative input or an insult to your intelligence or ability.  All criticism you receive from an experienced engineer comes as willing information oriented to your self improvement and success.  Our experienced Forum members dedicate their time and effort for that expressed purpose, hoping that you take in their contribution as a positive addition to your knowledge and experience.

 

Now for my contribution.

• You are dealing with unsteady state heat transfer.  I assume you are well aware of this type of heat transfer operation or have already been introduced to it.
• You heat up a batch operation with a heating fluid that is compatible with the fluid being heated and the availability and cost of the heating fluid operation.  If your fluid being heated is heat sensitive, you choose a heating medium that will produce the required results;
• You cool down a heated batch by using a fluid that is compatible with the desired cooling range sought.  For example, if you want to cool your batch down to ambient temperature, you use cooling water or perhaps ambient air.  If you seek to cool down to a further temperature, you use a refrigerated fluid such as a glycol water solution (or pure glycol) circulated through a refrigeration unit.  You can circulate your heating/cooling fluid through internal coils or a jacket.  In the case of ambient air, you would use a recirculating pump and an external cooling coil.
• We don't know what "dowfrost" is.  Do you mean Dowtherm?  In any event, your heating operation can be done with either an internal coil or the vessel jacket.  The cool down temperature depression can be done gradually and controlled by using an external pump with an external heat exchanger using a refrigerant.  The actual type of heating/cooling system that you decide on should comply with your Scope of Work - which defines your objectives, obstacles, limitations, guidelines, and critical points to employ in the design.

The above recommendations are given in general, written form.  For a more specific, engineered description with details and critical information you need to generate at least a PFD (Process Flow Diagram) or, preferably, a P&ID (Piping and Instrumentation Diagram.  If you are unfamiliar with these drawings, it is about time to jump in and get immersed in them because they constitute the main means of engineering communications you will be involved in should you graduate as a Chemical Engineer.  If you want our member to critique and comment on your PFD or P&ID, generate these on an Excel Spread Sheet so that they can make their comments and notes directly on the sketches.

 

[samayaraj]

Jackwill,

 

You got exactly what is actually required from Mr. Art. Thanks a lot Mr. Art for guiding young engineers.

 

The sketch I have given you is the spark to start the work. With this scheme, select the appropriate heating/ cooling/ refrigeration units and basic equipment such as pump, heat exchanger etc to make process flow diagram and add detailed descriptions & instruments etc to PFD to make piping & instrumentation diagram. To support you, refer Coulson & Richardson's Chemical Engineering Vol-6 for energy balance, flow sheeting & P&ID. Start your work and submit your PFD/ P&ID in forum for review. We will guide you.

[Jackwill]

Jack:

 

First some advice for a young, ambitious Chemical Engineering student:
Never take any criticism, or corrections from a senior engineer as negative input or an insult to your intelligence or ability.  All criticism you receive from an experienced engineer comes as willing information oriented to your self improvement and success.  Our experienced Forum members dedicate their time and effort for that expressed purpose, hoping that you take in their contribution as a positive addition to your knowledge and experience.

 

Now for my contribution.

• You are dealing with unsteady state heat transfer.  I assume you are well aware of this type of heat transfer operation or have already been introduced to it.
• You heat up a batch operation with a heating fluid that is compatible with the fluid being heated and the availability and cost of the heating fluid operation.  If your fluid being heated is heat sensitive, you choose a heating medium that will produce the required results;
• You cool down a heated batch by using a fluid that is compatible with the desired cooling range sought.  For example, if you want to cool your batch down to ambient temperature, you use cooling water or perhaps ambient air.  If you seek to cool down to a further temperature, you use a refrigerated fluid such as a glycol water solution (or pure glycol) circulated through a refrigeration unit.  You can circulate your heating/cooling fluid through internal coils or a jacket.  In the case of ambient air, you would use a recirculating pump and an external cooling coil.
• We don't know what "dowfrost" is.  Do you mean Dowtherm?  In any event, your heating operation can be done with either an internal coil or the vessel jacket.  The cool down temperature depression can be done gradually and controlled by using an external pump with an external heat exchanger using a refrigerant.  The actual type of heating/cooling system that you decide on should comply with your Scope of Work - which defines your objectives, obstacles, limitations, guidelines, and critical points to employ in the design.

The above recommendations are given in general, written form.  For a more specific, engineered description with details and critical information you need to generate at least a PFD (Process Flow Diagram) or, preferably, a P&ID (Piping and Instrumentation Diagram.  If you are unfamiliar with these drawings, it is about time to jump in and get immersed in them because they constitute the main means of engineering communications you will be involved in should you graduate as a Chemical Engineer.  If you want our member to critique and comment on your PFD or P&ID, generate these on an Excel Spread Sheet so that they can make their comments and notes directly on the sketches.

 

 

Jackwill,

 

You got exactly what is actually required from Mr. Art. Thanks a lot Mr. Art for guiding young engineers.

 

The sketch I have given you is the spark to start the work. With this scheme, select the appropriate heating/ cooling/ refrigeration units and basic equipment such as pump, heat exchanger etc to make process flow diagram and add detailed descriptions & instruments etc to PFD to make piping & instrumentation diagram. To support you, refer Coulson & Richardson's Chemical Engineering Vol-6 for energy balance, flow sheeting & P&ID. Start your work and submit your PFD/ P&ID in forum for review. We will guide you.

 

Thanks for your inputs, I have taken your feedback on board and managed to sort out the problem.