4 replies to this topic

[annie512]

Hi,

Please i need your help urgently. I am currently working on a gas compression station/gas export pipeline project. The blow down lines on some equipment (gas manifold, pig launcher/receiver and slug catcher) will require methanol injection due to the high possibility of hydrate formation. I want to calculate methanol injection rate required for hydrate inhibition; in one system, for example, the temperature and pressure downstream the blow down device are -35.48 degree C and 790.8 kpa a respectively. I looked up the ratio of methanol vapor composition to methanol liquid composition chart in GPSA to get a value at the above temperature and pressure but the temperature range of the chart is -18 deg C to 18 deg C.

Please is there another chart with a wider temperature range or a formula i can use to calculate the ratio of methanol vapor composition to methanol liquid composition at -35 deg c and 791 kpa a?

Thanks.

annie

[Dmitry]

Annie,

If you have got Hysys sowtware, you can calculate required inhibitor flow rate using the Hydrates formation utility. With Hysys you can use your gas analysis and water content. All datas has effect on hydrates formation.

Regards,
Dmitry

[PaoloPemi]

what do you mean with "methanol vapor composition to methanol liquid composition chart in GPSA" ?
I hope you may find a solution in this thread
http://www.cheresour...-with-methanol/

[annie512]

Thanks for all your responses so far. I still haven't gotten the solution to the problem. The gas stream i am working on is dry (ie no free water). Blow down calculations i performed shows that the minimum temperature will be -88 degree C. The hydrate formation temperature is -49 degree C. There is an excel spreadsheet im using to calculate the methanol injection requirement for hydrate inhibition. Part of the data i need to supply are water content of gas downstream blow down device( to be read off a chart in GPSA; fig 20-4, page 20-5) and the ratio of methanol vapor to methanol liquid(also to be read from a chart in GPSA;fig 20-65,page 20-32). The challenge is that the temperature downstream the BD device is way beyond the ranges in the two charts so i cant determine the values. So i need to know if there are formulas i can use to determine this or other charts with wider range. Thank you

[PaoloPemi]

you can calculate the amount of inhibitor with a correlation to predict the inhibition effect of methanol (see my previous post), you may find several examples in this book

http://books.google....e for Engineers

of course you can calculate the required amount of methanol injection with many software applications, by the way I use Prode Properties (see prode.com) but other simulators have specific utilities for that.