12 replies to this topic

[AJ KHAN]

Hello,

I have just started my professional career. It is the second week of my job at an industry trying to extract essential oil using super critical CO₂. They have problems with their product's quality and quantity, while I am having problems in understanding the causes of their problems.

Suppose we have fluid in a vessel (Vessel A) with inside Pressure 120 bar… When we open the valve, the fluid starts to flow into another vessel (vessel B) that was hitherto empty. Due to the Pressure gradient, the fluid flows with a certain velocity into vessel B. But the pressure difference would gradually decrease as the system tries to maintain equilibrium, hence the velocity would also decrease.

1. When I open the valve, the temperature drops suddenly, due to Joule Thomson effect… How can I calculate and control that?

2. What can I do if I want to maintain the Pressure in Vessel A above 100 bar at all times, while the Pressure in vessel B should not exceed 40 bar. I also want to maintain temperatures in both vessels at a desired value.

3. The fluid flowing from Vessel A to B is super critical CO₂ that is carrying oil with it. The intention is to bring the Pressure and Temperature in vessel B, anywhere below critical of CO₂ (i.e. 31 ^oC and 74 bar)… How should I design that separator?

4. I want to ask about knock-out drums used for flash distillation, they have an inlet diverter. What does it do? How can one calculate the right shape and dimensions of an inlet diverter for a particular requirement? (The intention is to drop the Pressure below critical of supercritical CO2, with essential oil mixed in it, so that CO₂ becomes gas and liquid oil is settled at the bottom.)

Regards,
AJ

[Art Montemayor]

AJ:

I consider this topic a very important one due to the nature of your being a young graduate confronted with an important production problem that will surely impact on your early career. This importance has made me dedicate some time and effort in trying to understand your description of the problem and subsequently contributing my experience in dealing with this type of process problem. However, I have not been able to form a required, detailed description of what the problem is and how it is affecting your ability to cope with it and resolve it. Allow me to offer you some “fatherly” advice on what you are confronting:

• You state that your employer has “quality and quantity” problems and that you have problems in understanding the causes of these problems. However, you fail to specifically identify in a detailed and concise manner WHAT –exactly – these problems are. Like too many young graduates today, you are exhibiting a lack of ability to communicate your dilemma or your problems. I earnestly advise you to work as fast as you can on your communicating skills. Without the ability to communicate accurately and concisely (as an engineer should), you will suffer in your career development.
• Describe to us (using sketches, sample calculations, a simplified PFD – or a P&ID) your existing process and its operating conditions – both actual and what they are expected to be. If the process has operated better or worse in the past, state it as such. Give us some historical background. Tell us what you believe is operating wrongly and why. Especially be cognizant of any safety or hazardous process conditions you might be aware of or suspicious of.
• Study and review the attached Excel workbook that I have prepared for you. Note that I have sketched what appears to be your first “hypothetical” question. I (or anyone else) cannot resolve your question because it is insufficient in basic data. You completely fail to identify the thermodynamic states of the process. You don’t tell us the temperatures! You are now in a real, down-to-earth industrial environment. This is a serious, business profit scenario that must be successfully resolved - quickly and efficiently. You are no longer in a classroom environment debating hypothetical problems. This is a “make it – or – break it” situation that you are being called upon to help with or to resolve. This is a real engineering challenge for which you have been hired. You must gather ALL the facts and data related to the fully identified and recognized problem(s) facing you and communicate these facts.
• You have taken a smart and practical step in seeking immediate and experienced help through this Forum. However, you haven’t helped yourself much by keeping us starved of Basic Data. By not helping us with data, you have hurt yourself. FIX THIS COMMUNICATING PROBLEM – for your own sake.
• Note in my sketch that I show ONE METHOD of controlling the process – but I can’t be sure because you fail to identify the desired (or required) fluid state (or phases) that should be maintained – and whether the process is steady state or batch. You must FULLY DEFINE THE PROCESS if you are to succeed in obtaining help or a resolution to the problems you face. You fail to tell us if you are flashing the supercritical CO₂ down to a liquid CO₂ state or into a fully CO₂ vapor state. You mention flash distillation, but you fail to tell us what this step plays in your process and whether it is involved in the process or not. If it is, is the process steady state – or batch? Once again, tell us ALL the process conditions and descriptions – preferably with a detailed PFD and P&ID. If you can’t share proprietary information, then tells us that; but TELL US.

We can’t help you if you don’t help us help you. I have a lot of years working with all phases of CO₂. I can probably answer any question you have related to the process – but I (or any of our Forum members) can’t help you without receiving ALL the basic process data.

I am attaching some required process information on CO₂ for you to study or employ in your job. I sincerely hope I have made my points clearly and I await your response.

Attached Files

•  CO2 Properties - Union Engineering.pdf   5.9MB   166 downloads
•  SuperCritical CO2 Process.xls   195KB   92 downloads

[AJ KHAN]

Dear Mr. Art,
Thank you very much for your response and advice. I am attaching a PFD of my process and another an explanation of the process. I apologize for a late reply, I was preparing the data. I have many other questions, but at the moment I only need some help with the issues I mentioned in the document.
Kindly take a look at these documents, I would be thankful for your response.

Regards,
AJ

Attached Files

•  Dear Sir.doc   27KB   46 downloads
•  Doc1.doc   311.5KB   51 downloads

[Art Montemayor]

AJ:

Thank for responding to my request. This helps some in identifying what the issues and problems are. I have prepared the enclosed Rev 1 of the workbook I initiated. Please take the time to review it carefully and confirm or correct what I have depicted. Note that working in Excel is more efficient and concise than in a work processor. We can calculate, draw, and comment in Excel with ease and efficiently whereas in Word, we don’t have that latitude.

I basically cannot identify what phase equilibria zone you are working in. You failed to tell us the temperature that you are heating up the SuperCritical Fluid (SCF) up to. From the Temperature-Entropy Diagram I submitted to you, you can see that you have a defined zone for a supercritical fluid. You should know that zone by memory. From the T-S diagram, you can appreciate that if you are going to expand (throttle) the SCF to a lower pressure in order to generate a vapor, then you have to heat up the 110 barg CO₂ to at least 70 ^oC.

It is important for you to understand what I am referring to and that you completely follow the thermodynamic process that I describe. If you are weak in thermodynamics, then you have a serious problem in trying to attack this problem process.

Let me know your response.

Attached Files

•  SuperCritical CO2 ProcessRev1.xls   423.5KB   71 downloads

[AJ KHAN]

Dear Mr. Art,

Please take a look at the file attached, I have tried to explain and elaborate our process for super critical fluid extraction. I have also mentioned the problems we are facing.

Looking forward to your advice.

Regards,
AJ

Attached Files

•  SFE.xls   84.5KB   56 downloads

[Art Montemayor]

AJ:

I have reviewed your submitted workbook and have made my comments and corrections on it for your review and study. Please study it carefully. I believe you have a hard – but not complex – path ahead of you if you are to succeed in what you are faced with.

As a young grad, I believe you are in a position that requires careful and very cautious thinking, concentration, and seeking of expert help. I have only focused on the Process issues. I have not focused on the mechanical issues (such as the mechanical integrity and proper design of the process equipment) and would caution you on being very careful and safe in determining if your process equipment has been designed properly and safely. You must pay particular attention to the proper Maximum Allowable Working Pressure (MAWP) that applies to each piece of equipment. Study and determine how many safety relief devices your process requires – taking into consideration the possibility of excess process heating due to a process upset or heat failure to turn off. I cannot over-emphasize the importance of these safety issues.

Feel free to consult with this Forum for further help or guidance. But be SPECIFIC and furnish ALL the basic data in the future.

Attached Files

•  SFE Rev1.xls   122KB   55 downloads

[AJ KHAN]

Dear Mr. Art,
Thank you very much for your patience and attention. I apologize for the errors in my communication. Kindly take a look at the file attached with this message.

Regards,
AJ

Attached Files

•  SFE1.xls   14KB   32 downloads

[Art Montemayor]

AJ:

Please forgive my delay in responding. I have had trouble with adapting to the many changes Excel has done to their drawing capabilities in Excel 2007. They have ruined Excel 97 for me and it is exceedingly more difficult to draw now.

We are slowly getting closer to the crux of your problem now. Please refer to my comments and responses in the attached Rev2 of your workbook. Keep the same workbook and simply note the Revision on the title of the revised one. That is so much simpler and organized instead of creating new workbooks for the same thread.

I hope you can better understand how you should proceed in this challenge. Basically, you are doing the right step in first identifying exactly what your product is and what are its properties and limitations with respect to temperature. I highly suspect you will find that the higher pressures and temperatures in the supercritical zone will yield more efficient extraction. However, BE WARY AND VERY CAREFUL ABOUT MAKING SURE OF ALL YOUR EQUIPMENTS' PRESSURE AND TEMPERATURE LIMITATIONS. STAY SMART AND SAFE FOR YOUR SAKE AND THE SAKE OF YOUR WORKERS.

Attached Files

•  SFE Rev2.xls   896.5KB   60 downloads

[AJ KHAN]

Dear Mr. Art,
I am really grateful for your advice. I would keep in mind all your suggestions before making decisions in the future. I want to share with you a research paper on the extraction of fennel oil. Their process is slightly different from ours, they are using a continuous process.

I was wondering if the optimum conditions mentioned in their process would be similar to ours. What if we set-up our plant based on their method and findings? I hope that if we create a similar process, then the optimum conditions for our process would not be too different from their optimum conditions (we can use trial and error to trace the best option).
Kindly take a look at the attached file and let me know what you think.

Regards,
AJ

Attached Files

•  1223_ftp.pdf   105.86KB   52 downloads

[AJ KHAN]

I am also attaching an excel sheet... Kindly take a look at this too.

Attached Files

•  Flow Diagram Excel.xls   22KB   60 downloads

[AJ KHAN]

Dear Mr. Art,

You may also want to take a look at the file attached with this message. In it, is the correct PFD of the process used in the extraction of essential oils.

Kindly take a look at this and let me know what you think. My actual question is in the previous message.

Regards,
AJ

Attached Files

•  793_ftp.pdf   222.72KB   62 downloads

Edited by AJ KHAN, 18 June 2011 - 06:37 AM.

[Art Montemayor]

AJ:

Thank you very much for the excellent quality of the basic data and references that you are now furnishing. This type of concise, applicable, and detailed data is very useful and accurately communicates what your process should be like. You have done a good job of feeding us the necessary information to piece together the best suggestions for your process. I believe we now have a credible PFD and should proceed onto a heat and material balance. From the completed PFD we go directly to a P&ID.

I am presently pressed to give attention and entertain my grandchildren who are visiting us for the Summer time here in Texas - as is our yearly custom. I will work to put together a formal and detailed response to help and assist you in proceeding forward with your work. The Portuguese research is - as I am sure you will agree - of excellent quality and information. It will serve to be the main basis for your process design. I have transcribed the Reports from a scanned .pdf file into MS Word for Windows in order to make my comments and observations directly on the word processing document. I can't do that on the scanned copy. Please bear with me as I am sure now that we can definitely put together a serious, safe, and successful process design that will satisfy your boss and your desire to succeed in this challenge.

Once again, thank you. You will hear from me in the coming week.

[AJ KHAN]

Dear Mr. Art,
Wish you a happy time with your grandchildren. Whenever you get time, please guide me on the arrangements in the PFD also. Why did they install a Back Pressure regulator parallel to the pump? How do they manage to control and regulate Pressure in Extraction vessel and the two separators? For Temperature control, I think they have jacketed the vessels, am I right?

Enjoy your time and have fun.

Regards,
AJ