Kibbled Alum to solution calculation

[NZNIROY]

Hi all,
Firstly, I just want to say hello (my first time posting).
I need a bit of help with undertaking option analyses on alum dosing. We currently use liquid alum which is transported to our dosing plants. I have been asked to look into the use of kibbled alum to see if we can make a saving to our operation.

If the liquid alum has a specific gravity of 1.32 and Al content of between 4.3-5.8% how would one process kibbled alum to create a solution product of the same specification as the liquid alum we currently purchase?

I believe the kibbled alum has an alumina oxide content of 17% (9% Al) and a specific gravity of 2.71. It would be great if I could work it out as a ratio of x amount of kibbled alum/litre of water would achieve the solution im after.
Any help would be much appreciated.
N

 

[bimr]

Assume you are feeding 10 mg/l alum to a stream of 20 MGD

Chemical feed = 20 MGD × 10 mg/L × 8.34 lbs/gal

Chemical feed = 1,668 lbs/day

And determine the alum feeder should be set to a rate of 2,252 lbs/day.

For 8.25% Al2O3 solution Alum):
Density (lb. per gal. @ 60oF): 11.074
Concentration (lb. Of dry alum (17% Al2O3) per gal.): 5.37
Concentration (lb. Al2(SO4)3 per gal.) 3.07

The gpd solution of alum to feed = 1,668 lbs/day/5.37 = 310 gallons per day Alum

Not familiar with Kibble, however with a 2.78 S.G., that would be 22.6 lbs per gal and
concentration of 22.6 X 0.09 / 0.17 = 11.96 lbs per gal.

The gpd solution of alum to feed = 1,668 lbs/day/11.96 = 139 gallons per day Kibble

 

[bimr]

"Kibble" means dry so the 2.7 S.G. that you listed is incorrect. Liquid alum (48.5%) is already saturated at 1.31 S.G. so the 2.7 S.G. is not possible.

People use liquid alum for the convenience as it is difficult to hydrate alum.

Commercial liquid alum (aluminum sulfate) is typically a solution near its saturation point, where the “Dry Alum” equivalent is approximately 48.5% on a weight/weight basis. Dry alum can be expressed as Al2(SO4)3•14H2O. The 14 waters of crystallization are included in the formula for Dry Alum. Because of the difficulty of creating a solution of liquid alum at 48.5% dry alum equivalent strength starting from a dry product, it is usually recommended that batches of alum solution are created, targeting 10 - 25 % by weight as dry alum equivalent (too dilute - hydrolysis takes place; too concentrated - takes too long to dissolve). Typically, it is recommended to follow a procedure using a 50 lb. bag of dry alum, made up to 55 gallons in a standard drum (lined/poly) with water. Warm water dissolves dry alum faster than cool water. The resulting alum solution will be 10.3 % dry alum solution by weight with the following properties: Specific Gravity = 1.062; Liquid Density = 8.86 lbs./US gallon. The 55 gallon drum is usually filled up half-way with water, and the alum is added slowly under mixing conditions. After the alum is added, the drum is brought up to the 55 gallon volume level with water, and mixing is continued until the dry alum is completely dissolved.

In summary, if you desire to use kibble alum, use a solution of 10.3% alum. The 10.3% solution will have an alum content of 0.91258 lbs alum per gallon of solution.

http://www.generalchemical.com/assets/pdf/Dry_Alum_Product_Profile_2014.pdf

http://www.generalchemical.com/assets/pdf/Liquid_Alum_Product_Profile_2014.pdf