Time Reduction for Batch transfer by using a pump

[pradeepbarola]

Refer to the attached image

Overview
The feed to V12 comes from distillation unit, where batch production rate is 16 Ton/day and at 220 degC. At first it is cooled to 160 degC in V12. Now this bulk is transferred from V12 to V18 using N2 gas pressure. All the transfer lines are jacketed (steam is used) to maintain the temperature. Once the receiving is completed (transfer takes 3-3.5 hrs) V18 outlet is opened and the pastillation unit is started (throughput=500kg/hr)

Process Description
1. Pastillation unit is stopped and V18 is de-pressurized to atmosphere, and vent is closed after that.
2. V12 is pressurized upto 1.5 atm using N2 gas, V12 uptake valve is opened and melt is transferred from V12 to V18
3. At the end N2 is taken through the transfer line and V18 develops about .5/.7 bar pressure.
4. V18 receiving valve is closed
5. V12 vent is opened.
6. Pastillation unit is started.
Problems faced
1. It takes around 3-3.5 hours for V12 to V18 transfer.
2. Pastillation unit can be started only after the transfer(as it is pressurized only after the transfer is complete)
Questions
1. Eliminate this 3-3.5 hr delay, and start the pastillation unit as soon as there is sufficient bulk in V18.
2. What should be the operation mode, batch or continuous. What should be the capacity of the gear pump for the purpose ?

Proposed Solution
Using a gear pump to transfer the bulk from V12 & V18

Challenges
1. Softening point for this bulk is around 90 degC. If a pump is used a big challenge is to avoid chocking in pump internals.
2. Once there is no material on the suction side, remaining material in the transfer lines can`t be pumped.
3. Making a control logic for pump operation(When will it transfer to V18 or V12 depending on the level in V18)
a. Refer to the attached pic for control logic
i. If the vessel V18 outlet is open it has to be pressurized using N2 gas, which will in turn put back pressure in the transfer line.

Addressing the challenges: Suggestions needed
1. Either provide continuous heating to the pump, to maintain the temperature well above softening point.(Cost of Heating (24X7) !)
2. Using a recirculation line from the pump discharge to the V12 vessel.(24X7 pump energy consumption !)
3. To avoid loses in transfer line, using N2 gas to transfer the material at the end of transfer. This N2 will increase the pressure in V18 as well.(advantageous)
These are the solutions thought at the beginning of this project, please provide your comments on this and also suggest if something better comes to your mind.
Kindly let me know for any queries regarding the process.
Thanks in advance 

 

[rollingstein]

Why cannot you feed from V12 directly to pastillation unit? What's the role of V18?

2. Once there is no material on the suction side, remaining material in the transfer lines can`t be pumped.

Can't pump be sited very close to V18? Then very short line length remains after pump.

 

[rollingstein]

V12 is pressurized upto 1.5 atm using N2 gas, V12 uptake valve is opened and melt is transferred from V12 to V18

Can't you pressurize V12 to a higher pressure?

What is the line size and line length? Even with, say, a 4 inch line I'm getting velocities barely 4 ft/sec even if you wanted to pump out the whole 15 m3 tank in half an hour.

That seems an eminently feasible flow velocity for a liquid. Without knowing your viscosity and density the rest is hard to know.

Your description sounds like you are working with something that will have viscoelastic properties. True?

 

[pradeepbarola]

Thanks for the reply.
Yes it is viscoelastic, basically vulkanox, a rubber melt.

If the pump is kept closed to V18, losses would be too much(friction + drop across the filter) ans moreover preference is to keep the piping network same where the pump discharge would be joined to N2 uptake line, close to V12.( If you could suggest something better, I am open to that).

Details for pipe size and length I can provide you in a day.

V18 is used as a buffer vessel, reasons for keeping the same, I can confirm you in a day as well. Keeping low pressure for N2 is because of the compressor capacity.

Now there are three options
1) Sending the melt from V12 directly to the pastillation unit.
2) Using higher pressure N2(need to check for the feasibility & cost impact)
3) Using a pump(then there would be added problems as I mentioned in the write-up)

Please provide you comments on this.

Have a nice day :)

 

[alphy]

Thank you for providing the overview and process description of the current batch transfer system. I understand the importance of optimizing processes to increase efficiency and reduce time. I have reviewed the challenges faced and the proposed solutions, and I have some suggestions that may help address the challenges and improve the overall process.

1. Eliminating the 3-3.5 hour delay:
To eliminate this delay, I suggest using a gear pump to transfer the bulk from V12 to V18. This will significantly reduce the transfer time compared to using N2 gas pressure. The gear pump can also be operated continuously, allowing for a continuous flow of material from V12 to V18. This will eliminate the need to wait for the transfer to be completed before starting the pastillation unit.

2. Operation mode and capacity of gear pump:
Based on the process description, it seems that a continuous operation mode would be more suitable for this process. This will ensure a continuous flow of material and eliminate the need for starting and stopping the process. As for the capacity of the gear pump, it would depend on the flow rate required for the pastillation unit. The gear pump should be able to handle the required flow rate and also have some extra capacity in case of any fluctuations in the process.

Addressing the challenges:
1. Softening point:
To avoid choking in the pump internals, I suggest using a gear pump that is specifically designed to handle viscous materials. This will ensure smooth operation and prevent any blockages in the pump.

2. Remaining material in transfer lines:
To address the issue of remaining material in the transfer lines, I suggest using a recirculation line from the pump discharge to the V12 vessel. This will ensure that all the material is transferred from V12 to V18 without any losses.

3. Control logic:
To control the operation of the pump, a level sensor can be installed in V18 to monitor the level of material. The pump can be set to start automatically when the level in V18 reaches a certain point, and it can be set to stop when the level decreases. This will ensure a continuous flow of material without any manual intervention.

Additional suggestions:
1. Heating:
To maintain the temperature above the softening point, I suggest using a heating jacket around the gear pump. This will provide continuous heating to the pump and prevent any blockages due to the low temperature.

2. N2 gas for transfer:
Using N2 gas to transfer the