21 replies to this topic

[ccjayesh]

I am going to design a liquid ammonia pipeline of 10km with 1000MT per Hour flow. Client is suggesting 'DRY' and 'WET' concepts and I have to evaluate pros and cons of both options. "WET PIPELINE SYSTEM" defines constant flow of liquid ammonia through the line irrespective of loading or not. when there is no loading, liquid ammonia will be recirculated. "DRY PIPELINE SYSTEM" define lines to be consists of ammonia vapours when there is no shipping.

Expecting your valuable advices in this matter..

[Bobby Strain]

A picture is worth a thousand (or more) words.

 

Bobby

[latexman]

My advice is to do some basic chemical engineering (PFDs, major equipment specs, cost estimating) followed by an economic evaluation (capital cost, operating cost, return on capital) of the two options the client suggested.  That's the minimum.  As you are doing this work, you may gain insight into a more optimal option.  Include that option too.

[Bobby Strain]

Your client must be out of his mind. Or has nothing better to do than study. It would be foolish to remove liquid from the line. You didn't mention loading conditions. But I presume that the ammonia is under sufficient pressure to remain liquid at ambient temperature. And that the loading is into pressured containers suitable for liquid at ambient temperature. Although your description suggests that you might be handling refrigerated ammonia. Want to share everything with us?

 

Bobby

[ccjayesh]

Loading is at @10barg pressure and -40 deg celcius. I dont have any idea about the process flow of "DRY" option. The loading will take place only once in a while, we can say once in a month or more. So looking for a option other than recirculation.

[Bobby Strain]

I can't make sense of your operation. Maybe you can provide a sketch showing the system. Including temperature and pressure throughout, including the vessel into which ammonia is loaded. You infer that you are using a 10km ? pipeline and transferring ammonia at -40 C. But this is absurd. So, share more to get something of value.

 

Bobby

[latexman]

This is beginning to smell like a student post.

[ccjayesh]

Hi

A simple sketch prepared myself is attached for your ready reference.

There are two liquid ammonia tanks of 17000MT each. The liquid ammonia will be exported from the tanks to a Jetty which is 10 km away from the plant. The loading system has two 100% pumps for a maximum 1000TPH loading rate @10barg delivery pressure. At the end of pipeline there will be a metering station and marine loading arm. There will be no vapor return line from the ship. But one return line is required to cater requirements of emergency situations.

 

Attached Files

•  liquid ammonia.JPG   19.39KB   15 downloads

Edited by ccjayesh, 17 June 2015 - 01:54 AM.

[latexman]

With this scale of operation, I recommend you look at "LPG ship loading systems" (Google this) as a best practice.  Ammonia and LPG have several similarities (vapor pressure, density, viscosity) and several differences (toxicity, environmental impact).  You will have to determine what applies to both and what does not.  I hope you abandon the process illustrated in your sketch.  It has problems.

 

Is this a student project?  If so, we will still help you, but it needs to classified properly.

[ccjayesh]

With this scale of operation, I recommend you look at "LPG ship loading systems" (Google this) as a best practice.  Ammonia and LPG have several similarities (vapor pressure, density, viscosity) and several differences (toxicity, environmental impact).  You will have to determine what applies to both and what does not.  I hope you abandon the process illustrated in your sketch.  It has problems.

 

Is this a student project?  If so, we will still help you, but it needs to classified properly.

Dear Sir,

Consider the sketch just like a Block diagram. I havent included any process in it. I have to develop a process design for option of "Dry pipeline" transfer. I have all the chemical properties of Liquid ammonia and it is easily accesible in the www.

I am looking for someone experienced in liquid ammonia.

thanks and regards

jayesh

[latexman]

Jayesh,

 

Are you a student or a degreed, working engineer?

 

I have several years experience with ambient temperature, high pressure liquid ammonia storage and distribution within a process plant.  I replaced a 1957 liquid ammonia  storage and distribution system in 2008 with a new, OSHA 1910.111 compliant pressure vessel and piping system.  It is operating very nicely today itself.  I do not have experience with low temperature, low pressure liquid ammonia, but do have this experience with a couple other chemicals.  I admit I am not a perfect match for your specific needs, but, as you can see, I am "someone experienced in liquid ammonia".

[Faisal Ghafoor]

I have experience of similar facility. We had recirculation line coming back to the main plant. The other way is to do very slow loading at the start of loading operation and once temperature are achieved (or near normal temperature), loading rate is increased as per design. Normally the big ships have refrigeration facility and safe venting also. They cannot take all normal vapor load, but starting the filling at very slow rate initially will ultimately yield the results. It of-course depends on how much time margin you are allowed to have for filling operation.

I suggest to do simple calculation of assuming very small flow to the line during loading operation and check how much time you need. In small lines of 1 km it takes 2-3 hrs to reach at acceptable temperatures.

Small barges doesn't have refrigeration capacity installed in their units and there you cannot do this.

[latexman]

That is exactly how LPG loading is done.

[Bobby Strain]

Jayesh must be a student since he never replied to the question.

 

Bobby

[latexman]

Yes.  If he fesses up, the thread can be moved to Students.  If he doesn't, Admin may boot him out and banish him.

Edited by latexman, 18 June 2015 - 10:17 AM.

[ccjayesh]

Jayesh must be a student since he never replied to the question.

 

Bobby

Hi,

I do have a Engineering Degree and couple of months back entered in the field of engineering. My questions may be of sub standard,  But requesting your patience and help for my survival in this field. 

Thanking you,

jayesh

Edited by ccjayesh, 19 June 2015 - 05:49 AM.

[ccjayesh]

Yes.  If he fesses up, the thread can be moved to Students.  If he doesn't, Admin may boot him out and banish him.

Hi,

I do have a Engineering Degree and couple of months back entered in the field of engineering. My questions may be of sub standard,  But requesting your patience and help for my survival in this field. 

Thanking you,

jayesh

Edited by ccjayesh, 19 June 2015 - 05:50 AM.

[ccjayesh]

I have experience of similar facility. We had recirculation line coming back to the main plant. The other way is to do very slow loading at the start of loading operation and once temperature are achieved (or near normal temperature), loading rate is increased as per design. Normally the big ships have refrigeration facility and safe venting also. They cannot take all normal vapor load, but starting the filling at very slow rate initially will ultimately yield the results. It of-course depends on how much time margin you are allowed to have for filling operation.

I suggest to do simple calculation of assuming very small flow to the line during loading operation and check how much time you need. In small lines of 1 km it takes 2-3 hrs to reach at acceptable temperatures.

Small barges doesn't have refrigeration capacity installed in their units and there you cannot do this.

 

I have experience of similar facility. We had recirculation line coming back to the main plant. The other way is to do very slow loading at the start of loading operation and once temperature are achieved (or near normal temperature), loading rate is increased as per design. Normally the big ships have refrigeration facility and safe venting also. They cannot take all normal vapor load, but starting the filling at very slow rate initially will ultimately yield the results. It of-course depends on how much time margin you are allowed to have for filling operation.

I suggest to do simple calculation of assuming very small flow to the line during loading operation and check how much time you need. In small lines of 1 km it takes 2-3 hrs to reach at acceptable temperatures.

Small barges doesn't have refrigeration capacity installed in their units and there you cannot do this.

Dear Faisal,

During shipping, on-board re-liquefaction unit will be in operation and pipelines are cold insulated so during loading we can neglect vapor loading. My concerned areas are as follows;

* If we select "Wet Option", Ship loading is occurring once in a while. We can say once in a month. so is it feasible to run re circulation continuously.  

* If we select "Dry option", after loading there will be a liquid hold up in the line. is there any operating procedure to avoid this. other wise BOG compressor or refrigeration unit in the vapor return line is a viable option?

Thanking you,

Jayesh

[Faisal Ghafoor]

We are doing recirculation in some facilities. The second option is to provide vapor ammonia line from compressor discharge to the shipping arm and then take the vapors+liquid back to the storage tank. Being 10 km long line, it doesn't seem feasible. If you have any utility nitrogen available near loading arm, hook that up and take back in tank with inerts vent open at compressor discharge. Also not a good option. If you have flare in the plant, you can send back this ammonia+nitrogen mixture to flare.

 

Regarding cold insulation of line, even with well insulated line, in one month most of the liquid ammonia would convert to vapor ammonia if connected directly with tank. If not, line will pressurize allowing thermal PSV to play its role; which is not nice at all.

Edited by Faisal Ghafoor, 19 June 2015 - 08:25 AM.

[breizh]

Hi ,

This resource may give you clues to support your work  !

 

Breizh

[ccjayesh]

We are doing recirculation in some facilities. The second option is to provide vapor ammonia line from compressor discharge to the shipping arm and then take the vapors+liquid back to the storage tank. Being 10 km long line, it doesn't seem feasible. If you have any utility nitrogen available near loading arm, hook that up and take back in tank with inerts vent open at compressor discharge. Also not a good option. If you have flare in the plant, you can send back this ammonia+nitrogen mixture to flare.

 

Regarding cold insulation of line, even with well insulated line, in one month most of the liquid ammonia would convert to vapor ammonia if connected directly with tank. If not, line will pressurize allowing thermal PSV to play its role; which is not nice at all.

Hi Faisal,

Thank you very much for your reply. If you have and P&ID of the system.please send to me.

[ccjayesh]

That is exactly how LPG loading is done.

if you have any loading procedure or PID please send to me