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Calculation For Chemical Injection Rate


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#1 sadia

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Posted 29 December 2014 - 07:31 AM

Dear All,

 

Kindly help on calculations for " Chemical Injection Rate".

 

I have gas flow rate and line size on which corrosion inhibitor is need to be dosed. How can I calculation injection rate of corrosion inhibitor.

 

Gas Flow Rate: 5 MMSCFD

Gas Line Size: 6''

 

Please also help on selection of proper dosing chemical.

 

Thanks & Regards



#2 hianbotech

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Posted 29 December 2014 - 10:41 AM

Ask  chemical vendors about your system, for example Nalco. They will recommend you the type of chemical and the recommended dosage based on your system.



#3 P.K.Rao

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Posted 29 December 2014 - 11:02 AM

The injection would depend upon the composition of the gas and the impurities present in it. As suggested above by hianbotech, you please contact Nalco, Dorf Ketal, Shell chemicals etc


Edited by P.K.Rao, 29 December 2014 - 11:03 AM.


#4 sadia

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Posted 30 December 2014 - 10:02 AM

Dear Friends,

 

Thanks for your reply. 

 

I have also the data of gas composition in mole% as given below:

 

Methane : 87.29 %

Ethane :0.2 %

Propane: 0.0006

Nitrogen: 2%

CO2: 10.5%

H2S: 0.000020%

H2O: 1000 ib/MMSCF

 

Now elaborate how i can calculate chemical dosing injection rate?



#5 hianbotech

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Posted 30 December 2014 - 10:33 AM

you should provide that infomation to the chemical vendor in order to determine the type of chemical and the dosage to be used. Additional you shall provide more information: material of of pipe and equipment to be protected, operational pressure and temperature, indicate if condensation of some liquid could happen inside of the pipe/equipment, etc.

 

The purpose of the chemical injection is protect the metallurgic of the pipes and equipment. A whole description of your system shall be supplied to the chemical vendor in order to have the right answer.



#6 sadia

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Posted 30 December 2014 - 10:54 AM

Sir i want to get knowledge about dosing system calculations. Your understanding is correct. we want to protect the metallurgic of pipe lines.
The material of Pipe Line is Cs and operating conditions are as follow:
Temp: 180 deg F
Press: 260 Psig

Please also note that chemical vendors neither treat individual inquires nor provide the calculations.



#7 RockDock

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Posted 31 December 2014 - 11:55 AM

How long is your pipeline? What is your pressure? The corrosion you may be trying to avoid may be caused by free water in the liquid or solid phase. That is easily avoided by methanol or EG injection. That calculation may also be easily done by modeling it with a simulator capable of modeling polar environments. Use a property package like Peng-Robinson-Polar, which is at least available in ProMax to calculate it. A non-polar property package will be pretty useless for methanol injection.

 

If that is not the corrosion inhibitor you are referring to, you will need to go to a vendor.



#8 RockDock

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Posted 31 December 2014 - 12:04 PM

I see your pressure is noted in an earlier post. I don't think you will have any liquid water forming anywhere around that pressure. As long as you keep it in the vapor phase, I don't think you need any corrosion inhibitor.



#9 sadia

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Posted 14 January 2015 - 11:18 PM

Thanks for your reply.

Kindly suggest me manual calculations for methanol injection. Please also tell me free software from which I can calculate the injection systems calculations.

 

Regards



#10 RockDock

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Posted 19 January 2015 - 10:11 AM

I don't know of any company that would trust a "free software" to make such a calculation. Your best free option would be to study the GPSA manual and use their correlations to make your calculation. The most robust and accurate calculation would be to use ProMax's polar model. That is the industry standard for such a calculation.






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