Using an emulsion polymer first requires that it be diluted to a 1% (or less) solution. Mixing between the polymer and water is critical. A failure to mix the polymer into the water will always result in poor polymer performance for any given application. A simple, inexpensive, effective device used to mix the polymer and water together to form a dilute polymer solution is illustrated in Figure 1. A turbulent flow low in shear is provided by the static mixer does the job nicely.
Figure 1: Static Mixer Used to Mix Polymer into Water
The static mixer itself is the key part of a polymer “makedown” system as shown in Figure 2. A rotameter is needed in order to set the flow rate to make a particular solution strength that may range from 0.10 to 1.0 percent. The makedown system includes backflow preventers, a pressure relief valve, and a pressure gage. The unit shown in Figure 2 uses two static mixers in series to provide rapid, complete dilution. Instructions for using the makedown system are provided below.
Figure 2: Polymer Makedown System
1. Connect the dilution water to the line below valve “A”.
2. Connect the discharge from the polymer feed pump to the line below valve “B”.
3. Pipe the discharge from the pressure relief valve back to an empty polymer tank (tote or drum or even a 5-gallon pail if nothing else is available).
4. Connect a drain line below valve “C” so the polymer dilution panel can be flushed when it is not in use.
5. Connect to the point-of-use line at valve “D” (or to a day tank for polymer aging).
6. Operation of the polymer dilution panel requires that valves “A”, “B”, and “D” be open prior to adding dilution water and/or starting the polymer feed pump. Valve “C” (to drain) should be closed. Valve “E” to the pressure gage is optional.
7. Always start the dilution water flow before starting the polymer feed pump. Doing so will minimize fouling of the static mixers from the “neat” polymer. Set the rotameter to approximately 3 gallons per minute when first starting the system.
8. Start the polymer feed pump and perform a drawdown to determine the required feed rate for the polymer. You will want to confirm your dilution water flow rate after starting the polymer feed pump to see if the water flow has dropped.
Note: More dilution water is better than less and having a sufficient flow and pressure for dilution water is often a problem. The goal is to get the polymer into solution has rapidly as possible and doing so takes energy. It is the water flow through the static mixers that imparts enough energy to provide sufficient mixing. The polymer solution should be at a maximum concentration of 1 percent. If the solution strength is less than this you will not experience any operating problems regardless of the application. In fact, more dilute polymer solutions often provide “better” results because the polymer achieves a better distribution in the waste stream being treated.
There are many ways in which the polymer makedown system can be incorporated into an overall polymer system. One such configuration is shown in Figure 3.
Figure 3: Polymer Makedown System - Complete
Figure 4 shows a polymer makedown unit in a refinery where it is mounted to a stainless steel panel with the chemical feed pump below the unit. The chemical pump shown is a diaphragm metering pump. This is not the ideal pump for pumping viscous emulsion polymers. A better pump, though more expensive, is a progressive cavity pump such as Moyno or Seepex (see Figure 5). The guy posing as the model is Bill C.
Figure 4: Polymer Makedown Panel Mounted
Figure 5: Seepex Progressive Cavity Pump -- Very Rugged