6 replies to this topic

[sjordan1]

I am currently working on designing an NGL recovery process in HYSYS, but there is one point that has extremely cold temperatures (-80C) and I am trying to price them out.  I was wondering if any of you knew any guidelines to estimate the costs for this because I cannot seem to find published figures for the costs of these units.

[shan]

-80 C refrigeration units are customer built.  You may send RFQ's to the vendors.

[paulhorth]

Sjordan1,

Most NGL recovery units that I am aware of do not require any external refrigeration. The cold is generated within the flowsheet by the use of a turboexpander on the main gas stream and well-designed heat exchange to recover cold. The power from the expander is used to partially recompress the treated gas. Further compression may be required to meet the specified gas oulet pressure.

 

Maybe you should research this type of flowsheet to see if it will meet your process needs. There are several proprietary flowschemes as well as typical unpatented "open-art" flowschemes,

 

Paul

[Art Montemayor]

I think Shan's English is mixed up or there is a typo error.  These type of refrigeration units are CUSTOM built (built to suit the specified conditions) and not built by the customers.

[shan]

Hoops.  Thank you for correcting my typo.

[junaid8942]

For propane dew point unit (mechanical refrigeration) the propane enters in chiller gas exchanger at the inlet temperature -15 F with vapour fraction zero and out let temperature -14F or same(-15F) with vapour fraction 1 so that all heat exchange due to the phase change. and the dew point of water in outlet  gas after condenser drum can be taken lower than 25 F. Furthermore, propane flow is adjusted by the water dew point at oulet gas.

[ColinR33]

As Paul noted, -80°C is typically a turboexpander plant.  Depending on the gas composition a supplemental refrigeration unit may or may not be required.  The "richer" the gas (ie. more C3,C4 etc) the more likley you are to need a supplemental refrig unit.  It also depends on what sort of recovery you are looking at.  There are a number of processes out there that can get you up to 99%+ C3 recovery, and C2 extraction to this level is also possible.  You need to be a little more specific as to what you are looking for.  There are a number of companies that do just the process engineering design (typically they have a patented process such as Ortloff, Linde, Lurgi, CB&I or the like), and there are a number of companies that can do "design-build" (this is what I did for 20 years), meaning they do the complete design with off-patent designs and actually fabricate a modular plant that can be shipped out to you.  They may be able to get you some budgetary numbers.  Information that is needed includes:

Feed Gas Flow Rate

Feed T&P

Feed Composition

Recovery and Product specifications

Residue gas pressure

Note that this sort of unit also requires the gas to be "bone dry", ie. <0.1ppm H2O, so if the gas is water saturated it will need a mole sieve unit upstream.  CO2 content may also be an issue due to CO2 solids formation at very low temperatures.  If you are below 1.5% you are likely OK but it should still be checked.  If you are going C2 extraction you will have to have a CO2  removal unit (amine unit) upstream of the dehy.  Needless to say, H2S will have to be 4ppmv or less as well.

 

Is this for an AFE or a school project?

 

Cheers,

Colin

Edited by ColinR33, 09 April 2013 - 12:32 PM.