Design of distributer/orifice plate

[MIkkelPoulsen]

Hi

i'm trying to best figure out how to calculate on a distributer/orifice plate for my column.
I have a water tank with a level of water - 0,2bar of water pressure.
Then i have a inlet pipe - where I have the volumetric flow and the speed.
This is a gas flow - of 9550m3/h with a speed of 30m/s

Then the flow enter the bottom of the column where there will be a large distributer plate with a lot of holes - where I would like to have a speed of 14m/s out of the plate.

How do i make this equation? Is it simple just Q=V*total area of holes?

Any ideas on how to best calculate the hole dimension and numbers?
Any ideas on how to best calculate or make a formular for distributing the flow out on the total surface?
The plate diameter is between 1000-1300mm - the inlet pipe will depend on the speed a above and the gas.

Best regards
Mikkel

 

[1503-44]

Certainly it must be close to V= Q/A, although water circulation may cause variations. There will be more pressure where water flow is downward, reducing gas flow out of holes in that region. You may get more gas flow at the center of the plate. Hole distribution may play a major role in determining circulation patterns, or its avoidance.

Hole number and size might be best determined by the bubble size you need to obtain sufficient surface interface for gas and water contact to achieve your cleaning targets.

So that's about 3 cu m3 of gas entering every second at an initial velocity of 30m/s, slowing to 14.
The size of the tank, or pipe, column??, or whatever it, is will need to be quite large to slow that down enough to get some contact time and avoid blowing the water out into the discharge piping.
This could be a very noisy thing.

Your plate will have an associated pressure drop with that velocity change, thereby changing the volume of the gas streaming out at the lower pressure. You kind of need to know the target operating pressure to work out the resulting volumes and velocities.


Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[MIkkelPoulsen]

Hi

Thanks for the feedback, yes the column is large.

My thoughts so far is that the inlet pipe is a 12" so around 314.14mm inside OD.
This goes into a large column where a plate covering the complete diamter is, this plate is around ø1300mm this will then have a number of holes to distribute the flow as much as possible and to create some small bubbles when the the going up through the water.

The water column pressure is 0,2 bar, and the pressure of the gas is not very large only around 0,5 bar.

 

[1503-44]

Gas outlet size: 30" diameter will give you a gas velocity of around 12m/s at 0.5bar absolute pressure.

Inlet options at 20 psig (a 25 psi pressure drop across the plate)
8.625" od 125fps at 20 psig.
10.75 od 75fps at 20 psig
12.75 od 52fps at 20 psig

That's kind of a high pressure drop, but any less of a drop will increase those diameters to hold those same velocities.

And those velocities are very high, if you want to keep water in the tank.
I think this should follow a similar design method used for gas/oil separators. In both cases the object is to allow gas to pass through without taking any liquid with it. So those velocities will have to be greatly reduced. You can see how here,

http://www.jmcampbell.com/tip-of-the-month/2015/09/gas-liquid-separators-sizing-parameter/

As you can see, a higher operating pressure will reduce the size of the equipment.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[georgeverghese]

Perforated plate sparger design is discussed on pages 14-74 and 14-75(sparger design)of Perry Chem Engg Handbook, 7th edn. It also makes references to earlier editions on how to minimise maldistribution of gas flow across the plate sparger.