Additive to an aluminum sulfate and water solution to lower pumping pressures

Question

I am currently looking for a surfactant (powder form) that I can add to a solution of aluminum sulfate and water. My current solution is comprised of 34 gallons of water and 4 (four) 50 lbs bag of aluminum sulfate. It has a specific gravity of 1.275

It is used as an additive to a gypsum based fireproofing product to lower the density as well as help with a quick set of the fireproofing material. It is injected into the fireproofing material at the base or a 1" hose that is 20 feet long. I was hoping to find an additive (surfactant?) that would reduce the pumping pressure of the fireproofing material thru the 1" hose without affecting the chemical nature of the aluminum sulfate and water combination.

The aluminum sulfate and water are mixed in a 50-gallon drum with a high propeller blade that is fairly aggressive. I worry that a normal surfactant will foam up too much and make the product unusable.

If a non-foaming agent can be added to the water that will offer to lower the pumping pressures of the material thru the 1" hose that would be what I am looking for.

Answer 1

The gypsum-based fireproofing material probably also contains fireproof/insulating additives like vermiculite or perlite. A commercial material like this is sold in bags, dry, and dumped into a mixer where water is added. Mixing might generate some air, and it is advisable to keep the air developed under control, but a lot of the air is eliminated during the spraying operation. In any case, it is necessary to keep the wet fireproofing material fluid enough to pump easily, but "dry" enough after spraying to stick to the surface to be fireproofed.

The aluminum sulfate solution viscosity is not the issue here. When it is added to the wet fireproofing mass, it begins to accelerate the set of the plaster of Paris ("gypsum"), and the mass begins to thicken. One way to reduce pumping pressure is to increase the hose diameter, say to 1.5 inches; or to shorten the hose a bit. Another way is to add a bit more water to the dry fireproofing in the mixer - make it just a bit too wet. As it begins to set, it may reach an optimum spraying consistency with a somewhat reduced hose pressure.

Controlling the air content is extremely important, because it makes the wet material less viscous, but when put under pressure, the air compresses and fluidity is lost. This is a problem that occurs before spraying and is not cured by air loss during spraying. These items are a matter of experience and "feel". It can get better if you keep looking for ways to adjust, although there is some amount of variation from bag-to-bag, and in the exact amount of water added, and the exact amount of mixing that occurs.

One possibility for development of a fireproofing material, which might require fire-testing on a large scale (at UL labs), would be addition of long-chain polyethylene oxides (https://www.industrialcellulosics.com/products/polyox) - the materials that produce pituosity in water and are used in concrete pumping applications to reduce pump pressures. Since they do act at the surface interface, they might affect the adhesion of the fireproofing material to the intended substrate.

Answer 2

The needed pressure depends on liquid viscosity. The significant decrease of water solution viscosity cannot be achieved by adding of minor additives.

It could be achieved by methods that may not be applicable:

• Decreasing concentration of the solute

• Decreasing viscosity of solvent by different solvent composition

• Increasing temperature of solution. A rule of thumb says viscosity decreases by 3% by increasing temperature by $1 ^{\circ}\mathrm{C}$.

Answer 3

Brother Aluminium Sulfate is a coagulant. Its used in order to bind to molecules suspended in water. You add any insoluble ions to the solution, it will bind to them and get thicker. Only thing you can do is increase temperature