Suction Blower for Open-Top Anthracite Filter?

[TexasCHe]

Inheriting equipment is great. I have an open-top anthracite filter that uses compressed air and water to backwash. Anthracite is supported by a plenum a couple feet off grade and the air is injected into this plenum. In the same plenum where the air is injected the original Walker Process drawing shows what we believe is an optional suction blower. Current Walker Process staff have not been responsive to questions on this 1980s vintage equipment. They don’t make it any longer. The question is . . . what is the purpose of this suction blower that’s rated at 250 CFM and 15 inches H2O? This is more than curiosity as I’m sizing a blow and need to ensure this suction device does not need to be considered.

Thanks

 

[bimr]

Like everyone else, Walker does not have much of a knowledge base on the staff anymore.

It looks like it was some cockamamie idea to pull carbon dioxide out of the water while at the same time you are filtering. It probably never worked as intended when it was installed.

I ran across another obsolete weird walker device a few years ago. The device was still in service after 50 years although the small town municipality that was faithfully operating it was unaware that it was not working as intended.

"When both carbon dioxide and iron are to be removed or when carbon dioxide is to be removed without iron, it is desirable to have a constant flow of air through the bed ll. Although the either upwardly or downwardly, it is preferred to have it flow downwardly so that there will be no danger that the filter bed will be air-locked with the resultant cessation of the flow of water downwardly there through. Theoretically the air can be made to flow downwardly through the filter either by applying suction at the bottom of the filter, or by applying pressure at the top of the filter. The suction method is preferred because of simplicity and because it lowers the pressure somewhat throughout the filter bed. portion thereof, and hence tends to draw the carbon dioxide out of the water so that the water flowing from the filter has an exceptionally low carbon dioxide content.

Air is drawn from the chamber 23 through pipes 20 by a suction fan II which may discharge through a pipe II to the outside atmosphere to avoid corrosive effects of the air drawn A baffle plate 32 may be provided around the end of the pipe 2| or any other means may be used for preventing water from being drawn into the pipe it, though probably none will be necessary. 1

At the present time it is desired to use a suction equal to 36 to 48 inches of water. Accordingly, the trap 25 should be four feet deep and its outlet should be at least four feet below the lower portion of chamber 23.

For less efficient use of the invention blower it can be omitted, in which case some circulation of air will be forced by the pulsating action of the sheets of water from the rotary distributor. Measurements in one installation have indicated that the flow of air out through the pipe II without a blower is about only one-tenth of that provided with the blower 28. The carbon dioxide content of the effluent water would have been objectionable for some purposes. although it was much lower than would have been possible without the circulation of air provided by the rotary distributor action together with the outlet 20 communicating below the false bottom."

http://www.google.co.in/patents/US2439764

 

[TexasCHe]

bimr,

If I had not read the link you sent I would not have believed it! The only thing that seems inconsistent is the patent unit, based on a quick look, seems to drop water in from the top and filter down through the unit likely in a non-flooded condition. Our unit remains flooded in the lower plenum. I guess a 15-inch vacuum would pull CO2 out of water but not as much is the water was indeed trickeling into the bottom plenum from the bed. Great site to investigate equipment patents!

Thanks a bunch,

TexasChe

 

[bimr]

Somewhat humorous descriptions in the patent:

"the water can be treated at unheard of flow rates per square foot"

Earlier, I only skimmed the patent as it is somewhat difficult to read and contains many incorrect technical assumptions.

My exposure to a 1950's era Walker unit consisted of a deep bed iron removal device. The bed consisted of 3/4" anthracite and this device also operated at unheard of flow rates. The city operated this device for 60 years and it probably did nothing for these years because the iron content was very low in the first place.

Some yahoo where I worked thought this device was a filter and changed the media to fine sand. The City then sued him because the device (with a sand bed) would no longer pass the unheard of flow rates. The case ended when the attorney paid off the City to make the case go away.

Some commonalities in these applications are high flow rates, anthracite, iron, and carbon dioxide.

In looking at your drawing, there does not seem to be any method of level control/flow control. At high flow rates through gravity filters or when the filter is fouled, it is possible to create a vacuum in the bottom of the filter bed. For this reason, there is usually some type of flow control on the outlet or a water level maintained on top of the filter.

For this Walker filter, if the gases came out of solution below the filter, then the suction blower could then be used to remove the gases.

Anyway, it was likely that it was an attempt to remove carbon dioxide or make the filter operate at an "unheard of flow rate" and never worked as advertised.