Liquid Addition Systems
The PHLAUER™ mixer can add more liquid and we have more technology than most other mixer companies. Both the single and dual shaft are good for adding liquid.
The rotor has organized transport with all particles moving at 210 feet per minute or one meter per second. This feature allows several methods of adding liquids depending upon particles size and weight, viscosity of the liquid, and absorbency without creating agglomerations.
Understanding agglomeration or lumps allows judgment to be applied. In this case an agglomerate is two or more particles held together by a liquid bridge where the strength of the bridge exceeds the weight of the particles and all other forces in the mixer.
Pipes with spray nozzles inside
a single rotor mixer.
Here are some usual methods:
Slug loading using a pour or distribution pipe.
The purpose of a distribution pipe is to slug load liquid, and in a curtain, all the way across the length of the mixer. It works great with limited absorbency and pelletized ingredients, or at the other extreme end of highly absorbent like peat moss. Another major advantage is that they rarely have to be cleaned.
If the liquid will stay on the surface for just a few seconds, the high particle movement will wipe it from particle to particle and coats all surfaces including the ends.
All tanks are stainless steel and the stands
are on load cells for weighing. The tanks on the
left are heated,insulated and clad.
When slug loading causes agglomerates or spotty material, the first move is to go to spraying and/or lengthen the application time.
Spray nozzles should be selected to get a minimum spray time, 20 seconds, and get as much coverage across the mixer as we can get. There also has to be enough liquid to hold for 20 seconds. There is too much air current in a mixer to use air atomizing sprays because they will deposit the liquid on the machine rather than the products.
A flat fan spray hydraulic nozzle is better for keeping the liquid off the paddles and hitting the particles as they pass. We have put them at 30 degrees in pet food. You need a minimum of 540 ml of liquid. If you are trying to do less than that, we need to bulk it up, and can do it per batch if there are many recipes.
Our stainless is the same as everybody’s—if it gets wet, powders stick to it, and also coffee beans. Liquids should be applied on the upside in single rotor machines and in the center of double rotor machines.
If the spraying is creating lumps, there are several ways to overcome it:
1. Use a finer spray and more time.
More pressure creates small droplets. A pressure pot can go to the available plant air, (typically 80 psi is highest you can rely on), and above that you can go to high pressure spraying.
2. High pressure spaying is done using a gear or lobe pump that can develop infinite pressure, and a return line through a process flow valve that can be adjusted for application pressure.
Don’t forget the gauge. Viking pumps and Fulflo process valves are our preferred brands. We have done tests to 400 psi. Do not use a pump with a poppet in the impeller to control pressure because of risk of fire on some liquids.
3. Using a High Powder Flow Bar (HPFB) to speed up the particles under the spray nozzles.
The HPFB is a spike bar that has none or very little shear. It is sized to fit at the edge of material between the rotors on a double machine. A single has not been tried, but may be possible.
The speed of particles in the machine from the rotor is sin 45 x 300 fpm or about 210 fpm. The speed of the HPFB has to be adjustable so the particles just go over the rotor and not up against the cover. Typical speeds are 600 to 1200 fpm on the periphery, and this additional speed is useful for putting “sticky” liquids on fine particles. We are using them to put hot melted tallow on dextrose of 200 mesh. We also use it to apply resin to a fibrous material along with high pressure spraying.
4. Use a Shearmaker to take the lumps out.
This can be done with either spraying on top, or putting it through a sparger just above the SM. A sparger is a spray nozzle buried in the material.
I believe that spraying on top gives the best opportunity of hitting all the particles directly, whereas a sparger tends to create lumps and have the lumps broken and mixed in. The result could be two different products.
The above statements are how to apply liquid inside to the product. In addition, the spray nozzle needs a minimum of 8” to develop a droplet. This space can be provided in a tower, or increasing the height of the mixer and putting a pipe inside. Typically, when we increase mixer height it is 14” to allow to make the pipe removable, and have space for a check valve if needed to stop drips.
The liquid also has to be measured and propelled. Weighing the liquid is the most accurate and will save liquid. Because of increased cost of liquids like fat, the savings from a good system will justify itself. To weigh, we use a pressure vessel on a load cell, and then compressed air to enter it into the mixer and clean the nozzles.
Other measuring devices can be used such as flow meters or using a loss-in-weight feeder. If you have varying recipes be aware that your spraying needs constant pressure, and these devices offer constant flow and generally can only be sized based on one volume unless a pressure pot is also used in the system.
If you are using multiple vendors, it is always a good idea to put the total liquid system under one vendor.
Vacuum infusion is a method of adding high quantities of liquids to porous materials. The mixer is a pressure vessel to withstand one atmosphere of external pressure. Product is entered, vacuum is pulled, liquid is applied, and vacuum released. The atmospheric pressure at your elevation drives the liquid inside the product. This is proven successful with extruded feed kibble and has some effect on pressure formed pellets.
A & J can specify or supply all the hardware necessary for liquid handling and applying.