Max gas velocity

[mathlover]

Hi Id like to know how to work out what the maximum amount of gas i can get down a pipe is.

The gas is methane. Its composition is roughly ch4 @ 59.5%, co2 @40%, 02 @ trace, h2o @0.5%, Nox & Sox = Trace, HCL = Trace. It is biogas and the temperature is around 34 C entering the pipework and 6 C before use.

The Pipework is various diameters but it has a bottleneck minimum of 6"

The pressure at the start of the system is around 15mBar / 150mm water gauge.

The pressure varies across the system with diameter.

Thanks for your help

Edited October 31, 2008 by mathlover
Hydrogen Clouride (HCl) was abbreviated as HCF

[insane_alien]

well, we would need to know the length of the pipe, the diameters the lengths of pipe at the diameters, the bends, valves etc, etc.

[mathlover]

thanks

i dont have them all but im more interested in building a spreadsheet where I can enter them into and deal with any scenario.

Do you know where there is one or do you know the equations i need to work it out.

 

Hi Please can someone point out the equations i need to search for on google to understand this. Thanks in advance :>

 

Ill try and explain a bit more about the problem I have -

 

The system is set up to supply two gas engines running big alternators producing electricity. At the same time as electric production they heat water that is used to heat 2 anaerobic digesters fed with waste to around 35C which is its optimal for biogas production. The digesters are both large covered tanks with 5000m3 capacity and 10m Diameter. The pressure in the system is produced by the digestion process as the gas is released from the sludge mixture held within.

The roofs of the digesters are floating type so they rise and fall to collect gas from the system.

 

The engines are sized at 600kWe each and theyre about 34% electrically efficient. The biogas has a CV of 35.8mj/m3 so need to supply the whole system with

 

600kW*2 =1200kW/34 = 1%

*100

3529kW = Total Energy Input Requirment

converts to MJ (/3.2) = 11294MJ

divided by cv of 1 m3 of biogas (35.8MJ) = 315m3 / hr

 

I have a new boiler on the system using the gas aswell and when the boiler is running the engines are starved of gas. I know they are because their output goes down and bounces around.

 

So I suppose what im trying to work out is what happens if I fluctuate the pressure at the top of the system or if I start to draw more than can be supplied down the pipeline.

 

I assume there must be a maximum that can be drawn down a leg at a certain diameter and pressure. A bit like if you try and breath only through your mouth with a straw and you get out of breath because you cant get enough down the straw.

 

Thanks again.