6 replies to this topic

[stu]

Dear all,
Based on the hydrate formation temperature arrived from hysys , I had calculated the temp. to be depressed by using inhibitor.
Based on the Hammerschmidt equation & Nielsen-Bucklin Equation , the injection rate of Methanol and MEG is calculated manually.
When I feed the same rate in the Hysys , the temperature is not depressed for the calculated flow rate for the both Methanol & MEG.
Please suggest how to rectify.
Regards,
Stu

[ankur2061]

Stu,

At higher natural gas pressures, HYSYS tends to underpredict the hydrate formation temperature. Some experts in the gas processing field consider hydrate formation conditions as predicted by the HYSYS hydrate utility to be some what unreliable.

Another aspect that needs to be looked into, is that when methanol is used as a hydrate inhibitor the vaporization losses to the gas phase need to be considered and added to the methanol consumed for hydrate prevention. The vaporization losses can be read based on the final gas pressure and temperature from the chart (Figure 20-51) given in the GPSA engineering databook, 11th Edition, SI units.

I have developed a spreadsheet for Hydrate Inhibitor Injection calculations and if you provide me the following inputs I can calculate and inform you the injection quantities for both methanol & MEG:

Gas flow rate in SCFD or SCMD

Upstream (Higher) Gas Pressure

Upstream (Higher) Gas Temp.

Downstream (Lower) Gas Pressure

Downstream (Lower) Gas Temp.

Gas Composition or gas specific gravity, preferably gas composition if the gas is sour and with high CO2 content

Regards,
Ankur.

[stu]

Dear Sir,
Please find the data
Gas flow rate : 6.5 MMscfd
Upstream (Higher) Gas Pressure : 255 barg

Upstream (Higher) Gas Temp:50 deg c

Downstream (Lower) Gas Pressure:45 barg

Downstream (Lower) Gas Temp.:10 deg C

Gas specific gravity:23

Regards,
Stu

[ankur2061]

Dear Sir,
Please find the data
Gas flow rate : 6.5 MMscfd
Upstream (Higher) Gas Pressure : 255 barg

Upstream (Higher) Gas Temp:50 deg c

Downstream (Lower) Gas Pressure:45 barg

Downstream (Lower) Gas Temp.:10 deg C

Gas specific gravity:23

Regards,
Stu

Stu,

What you have mentioned as gas specific gravity is gas molecular weight.

Based on he data you have provided the MeOH injection rate (100% methanol) is 100 kg/day.

The MEG injection rate is calculated as 40 kg/day (80% aqueous MEG solution).

Hope this helps.

Regards,
Ankur.

[vvsastry66]

Dear Ankur,

Could you pls provide the hydrate calculation spread sheet.

vemparala.sastry@exterran.com

Rgds
Sastry

Dear Sir,
Please find the data
Gas flow rate : 6.5 MMscfd
Upstream (Higher) Gas Pressure : 255 barg

Upstream (Higher) Gas Temp:50 deg c

Downstream (Lower) Gas Pressure:45 barg

Downstream (Lower) Gas Temp.:10 deg C

Gas specific gravity:23

Regards,
Stu

Stu,

What you have mentioned as gas specific gravity is gas molecular weight.

Based on he data you have provided the MeOH injection rate (100% methanol) is 100 kg/day.

The MEG injection rate is calculated as 40 kg/day (80% aqueous MEG solution).

Hope this helps.

Regards,
Ankur.

[ankur2061]

Sastry,

This spreadsheet is not for free distribution at this moment of time. If and when I decide to distribute I will post it on "Chereosurces" forum for everybody to download and use.

Regards,
Ankur.

[Moses Gideon]

Please sir, i need this spreadsheet very seriously,
Thanks
moses