how to calculate standard liquid flow rate 3

[gcet007]

hi all,

Can anyone tell me how to calculate normal liquid flow rate to standard liquid flow rate.

@ 345 F, 500 psig, I have liquid flow rate of 1400 gpm, molecular weight 60. I want to calculate flow rate in standard condition i.e. what will sgpm ?

thanks

 

[pleckner]

I think you are confusing liquids with gases/vapors. There is no "standard" gpm.

 

[Montemayor]

Is this a joke? Are you a practicing Chemical Engineer?
Where did you hear about "Normal" and "Standard" liquids?

 

[CJKruger]

gcet007, the difference between "actual", "normal" and "standard" volumetric flow rates for both gases and liquids are as follows:

W = mass flow (kg/h)
Q actual = W / density at actual T+P
Q normal= W / density at "normal" T+P
Q standard= W / density at "standard" T+P

"Normal" T+P = 0 C and 1 atm typically.
"Standard" T+P = 60 F and 1 atm typically.

In refineries we typically express gases in "normal" flow and liquids in "standard" flow.

 

[katmar]

CJKruger, this surprises me. I have heard "standard" used for gases, but not for liquids. Do refinery liquids change density with pressure and temperature that much that it is routine practice to correct them to "standard" conditions?

It also surprises me that in a particular refinery gases would be referred to a base case in Celsius units while liquids are referred to Fahrenheit. In my experience either Celsius or Fahrenheit is used consistently for both gases and liquids on one site.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[dcasto]

The calculations by CJKruger are on. Next, where to get the densities?

There are tables in the GPSA that could be used for hydrocarbons, if thats what you have. If you have hydrocarbons, you may have a difficult time finding the answer. At 60 MW, you've got nearly a Butane molecule and it won't be a liquid at at the conditions stated. It is really close the the criticle point too.

 

[JJPellin]

Some of these replies are surprising to me. I work in an oil refinery and I have to convert actual flow (hot flow) to standard flow all the time. In order to make their mass balance monitoring work properly, the vast majority of the flows in our plant (liquid products) are given in units of Standard Barrels per Day. The density of hydrocarbon liquids changes quite a lot with temperature. For a hot gas oil stream, running at 600 °F, the conversion from standard units to hot units would be about 1.15. Young chemical engineers regularly get themselves mixed up with this. They measure a flow in standard units and plot it on the pump performance curve. Then they send out an e-mail declaring that the pump is running below the curve by 10%, 15% or more. When I analyze it after correcting the flow to standard units, it shows the pump is right on the curve. Your process engineers should be able to give you to standard and hot specific gravity for your stream. The conversion simply involves multiplying the standard flow by the ratio of the specific gravities. If you don't have the hot specific gravity, there are standard charts for hydrocarbons that are quite accurate. I don't have one handy I cam post or link to.

Johnny Pellin

 

[djack77494]

I share some of Jonny's experience and believe the misunderstanding occured when it was assumed that the fluid must be a gas or vapor. Though it is more common (and necessary) for people to carefully define conditions when discussing gas flowrates, conditions (standard or hot) are also commonly defined for liquid hydrocarbons, at least in refining and production.

 

[SeanB]

I agree with Johnny. I too work at a refinery and we define "standard barrels per day" at 1 atm and 60 °F. Most instrument datasheets that you complete ask for density at flowing and at standard conditions. To correct to flowing conditions to standard conditions you use a ratio of the flowing density to the standard density. This seems very common to me so I too am surprised by some of the responses.

 

[katmar]

Thanks to all the refinery guys for the input. I have learnt something new today. I suppose it is a combination of the high temperatures and high expansion factors for refinery liquids that makes it necessary. I have never come across this in the industries I have worked. I agree that it is "standard" (or is it "normal"?) practice to fill in actual and reference conditions on a spec sheet, but I have never regarded this as a "standard" in the way I use standard and normal in relation to gas conditions.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[25362]

I've seen the acronym sgpm being used by Honeywell on measuring instrumentation for liquids.

 

[zdas04]

Oil & Gas upstream operations talk about "Stock Tank Barrels" which are defined as liquids that have been allowed to reach ambient temperature and have sat long enough to allow the most volatile components to flash. Since "ambient temperature" varies considerably with time and there is no clear definition of how long is "long enough", it has never really felt very "standard" to me.

I suppose the exotic liquids along with very high and very low temperatures and pressures in a refinery or chemical plant would force some sort of standard into volume reporting. Either that or report everything in mass flow rates (come to think of it every PFD I've ever seen has been in mass units).

David

 

[gcet007]

Thank you for reply particularly who works in petroleum industry. And for Montemayor & pleckner, i hope now you realize the fact of standard and normal flow rate.
If you are still not cleared about standard and normal condition, go to any simulator like Promax and select any hydrocarbon stream with providing temp, pressure,composition & flow rate and when it converged, it will show you standard and normal flow rate which are totally different. And now i understand it's because of ratio of specific gravities.

thank you,

 

[JJPellin]

The concept of Standard flow units for refinery liquids is fundamental. It would be impossible to size a new control valve or evaluate the performance of an existing control valve without understanding this principle. The performance of a control valve or a centrifugal pump can only be evaluated after the standard flow rate (either standard volumetric flow or mass flow) is converted to actual volumetric flow (hot gpm is typical in the US refining industry).

I come to this site in order to discuss engineering issues with professionals. Personal attacks and insults have no place here. I feel some applogies are in order.

Johnny Pellin

 

[mbeychok]

Johnny Pellin:

I realize that English may not be the first language of the original poster. I think perhaps some of the confusion arose when he asked how to convert "normal" liquid flow rates to "standard" liquid flow rates.

Many of us think of "normal" flow rates as the metric connotation of Nm3 per unit of time, as used for gases.

I think the confusion would not have arisen had the original poster said he wanted to convert "actual" liquid flow rates at the given temperature to "standard" liquid flow rates at a defined temperature.

I worked in refinery operations and refinery design for about 50 years myself and we used "actual" and "standard" to describe liquid flow rates at different temperatures, and we used tables to obtain hydrocarbon liquid densities at the different temperatures.

So perhaps you could find it in your heart to forgive Phil Leckner and Art Montemayor who have made many, many important contributions to this forum as well as to other forums.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[pleckner]

First, I want to thank Milton.

Second, in re-reading my post I don't see where this can be considered an "attack" as I was only seeking to understand if the OP was confusing fluid states.

Third, just to educate me in the ways of the refinery world, are you talking about standard "gpm" or standard barrels? It seems everyone here is answering the question in what appears to me at least to be in terms of standard barrels and not standard gpm.

 

[gcet007]

to all,

thank you for excellent remarks and understanding. i used wrong word "normal" instead of "actual" in discussion. so, it's my mistake. Montemayor and pleckner, i know u guys are expert in your area and my intention of reply is not to hurt any of you.

thank you,

 

[JJPellin]

The most common "Standard" unit I see for flow is Standard Barrels per Day. I occasionally use Standard GPM. But this is because my specialty is pumps and I am so used to thinking of everything in GPM, be it standard or actual. That may be peculiar to me and not indicative of the entire refining industry. I think we have probably beaten this poor dead horse enough.

Perhaps I overstated my concerns. Mr. Leckner, I did not intend to insinuate that you insulted or attacked anyone. You did not. I was referring to Mr. Montemayor's reply. I am sorry if I stirred up hard feelings. As gcet007 makes clear, no harm, no foul. He took no offense. So the issue is best forgotten.


Johnny Pellin

 

[gedomin]

Standard liquid flow is commonly understood at 60 degF and low pressure.

From "Data Book on Hydrocarbons", page 145, we find a chart with a family of curves. Thermal expansion coefficient depends on molal average boiling point.
You divide actual flow over expansion coefficient to obtain flow at the standard 60 degF.
Expansion coefficients at 345 F, for different MABPs as follows:
MABP / Expansion @345F
200 / 1.255
300 / 1.21
400 / 1.185
500 / 1.165
600 / 1.155
800 / 1.13
1000 / 1.12