Ethylene Pipeline 1

[peedco]

Recently I have started my new job in the world most longest ETHYLENE PIPELINE Project. Since the geographical and topographical characteristic and climatic conditions at different segment of right of way of the pipeline is different from each other, it has made is as the most complicated one in operation point of view.
Ethylene is compressed supercritical gas in summer conditions, when it passes the pipeline located in mountainous area and it is compressed supercritical liquid in winter conditions, when it passes same rout. So it is completely different, comparing to the natural gas pipeline.
For this reason I am wondered which type of machines (compressors or pumps) we should select for transferring of ethylene, to provide required head and maintain the pressure of the ethylene at the required level at different section of the pipeline.
If any one who has experience in Ethylene pipeline please help me to find:
*)Which criteria I should consider for selection of the right machines (compressors or pumps) for transferring ethylene?
*)Which skills we should consider in design of pipeline to minimize risk of two phase flow in abnormal operating conditions?
*) Do we need pig launcher and receivers for pipeline what should be the pigging procedure?
*) What safety factor we should consider for Right Of Way regarding the supercritical conditions of ethylene which is different from natural gas.

 

[europipe]

I know Dow Chemical and Basf have very long lines in our country with boost stations inbetween.
When you are with Dow try asking Plant engineering Terneuzen.
Never heard of dirty eth. lines never heard of pigging that lines.

 

[dcasto]

Fist, no such thing as super critical liquid. I worked on the longest in the US. We used thre different compressors. IR HHE slow speed. Bingham splitcase pumps, and cryodynamics pumps Ebara.

You need to keep the pressure over the criticle pressure, about 850 psig. The higher the pressure, the more dense, the less pressure drop.

Typically ethylene pipelines run at inlet pressures over 2000 psig, 2400 psig would be good. Then recompress it when the pressure is about 900 psig.

The cryodynamic and bingham pumps are modified liquid pumps. The impellars need to be very light, not SS! They are limited to about 2 ratios (8 to 16 stages). The reciprocating compressos, IR, Ariel, Nouve Pignoi (sic), can have up to 3 ratios per stage, so 2400 psig is no problem with 900 psig inlet.

Most vendors will have some problems with the concept of using a reciprocating compressor or a water pump (we had both in parallel.

You need to model your pipeline using Hazen Williams and not Panhandle equation. Iterate the density change every 2 to 5 miles.

 

[peedco]

This Pipeline (WEP) is the longest ethylene pipeline in the world. Length of WEP is about 2300 Km and capacity of transferring is 3.5 Million Ton per Year for feeding 11 Petrochemical plant. This pipeline feed from 2 Olefin plants from Assaluyeh & Gachsaran in south of Iran. Pipeline was designed to transfer supercritical ethylene. Operating pressure is 60 ~ 93 Bara and eight (8) compressor stations are considered to compensate frictional & static pressure drop of pipeline. Productions of polymer in pipeline increase the roughness of pipeline and there are comments that Pipeline shall be pigged for increasing capacity of pipeline (Reference: Polymer cleaning of Wilton-Grangemouth Ethylene Pipeline – 1997). We assumed that Compressor stations consist of Variable speed Electro-centrifugal compressors. Electro-compressor can be operate in
50 ~ 105 % of design RPM.
Elevation change in pipeline is about 2700 m and some of compressor stations located for compensate static pressure loss of pipeline in winter (dense-phase of ethylene).
Anybody knows information about these procedures for ethylene pipeline:
1- Safety area around the pipeline (Area of Right of Way)
2- Purging of pipeline (limitation of water & oxygen content in ethylene pipeline before startup)
3- Pre-commissioning & startup
4- Pigging procedure

 

[dcasto]

There is a properitary method to limit polymer formation in an ethylene pipeline. You might be able to pay the operators of the lines in Texas (Lyondell/Occidental Chemical)on how they reduced the polymer growth, I cannot tell you, it is a trade secret, it includes two seperate processes.

1. Safety around pipelines. We followed typical UD safety rules, nothing special.

2 Purging. The line has to be dried to -60 C. Inerting has to be almost absoltue, no O2. Nirogen is the inerting agent of choice. I've seen plant's exploded when the O2 was not removed and nitrogen was left in the line and compressed by the commisioning process.

3. Precommisioning. Again there are patentented processes for commisioning ethylene pipelines held by BJ services. We had a process that came out about the same time BJ had their patent, but was simplier and used common oilfield equipment instead of specialized equipment, both saved lots of money and time over the previous ways.

Pigging. Typical proceedures, but use jet pigs after the line has been in service. We never pigged, it was not worth the risk of stopping the line because of build up.

There are lots of papers out there on ethylene piplines. Operations can be a challange.

 

[peedco]

Thank you.