Method and apparatus for diluting and activating polymer

The invention comprises a combination concentrated polymer storage tank, mixing tank, and aging tank with a polymer deliver pump and water control valves to deliver the polymer and water to the mixing tank and aging tank. Additionally, the mixing tank provides a residence time for mixing of 30-45 seconds, and the aging tank provides an aging residence time of 2-10 minutes.

BACKGROUND OF THE INVENTION 
Various synthetic and naturally occurring water-soluble polymers have been 
developed which exhibit excellent thickening and flocculating properties. 
Most commonly used are acrylamide polymers which include poylacrylamide 
and its water-soluble copolymeric derivatives such as acrylamide-acrylic 
acid and acrylamide-acrylic acid salt which contains 95-5 percent by 
weight acrylamide. Copolymers of acrylamide with vinyl monomeric such as 
maleic anhydride, acrylonitrile, styrene, and the like are also useful. 
Other useful water-soluble vinyl polymers are described in detail in U.S. 
Pat. Nos. 3,418,237; 3,259,570; and 3,171,805. The polymers are generally 
available in powder form but useful only when dissolved in water. 
One method of use has been to first disperse the polymer in a carrier such 
as oil. The polymer is generally highly concentrated in the carrier and 
must be diluted to a concentration of approximately 8%-10% in water or 
other diluents before use. One such method using a oil based carrier is 
disclosed in U.S. Pat. No. 3,624,019. 
The polymers have molecular weights of up to 25,000,000. As such, they 
exist in the carrier in tight coils. The active sites for treatment of 
wastes are believed to be along the chain and in the coil form the 
polymers are not effective. In addition to being diluted, the polymers 
must also be allowed to uncoil to expose the active sites and activate the 
polymer. 
Due to the size and length of these polymers, they must be mixed gently to 
prevent breaking up of the chains into smaller, less efficient particles. 
There is, therefore, presented a problem in the mixing and dispersion of 
polymer in diluent. If the polymer becomes uncoiled during mixing, it can 
be broken up. Methods and apparatus have been designed to disperse the 
polymer gently in water--see for example U.S. Pat. No. 4,522,502. Also my 
U.S. Pat. No. 4,747,691 mixes first then activates the polymer after 
mixing in an unagitated aging tank. 
Drawbacks to both the above patents exist, in that mixing and aging times 
are not set out with particularly. For example, in my patent, the aging 
tank and mixing tank have substantially the same residence time. I have 
since discovered that this is not sufficient to get the best results from 
the polymer. Data indicate that the diluted polymer should not be agitated 
more than 30-45 seconds and should be aged for approximately 2-10 minutes. 
I have thus improved upon my earlier invention by providing an apparatus 
which provides the required mixing and aging times. 
SUMMARY OF THE INVENTION 
The invention thus comprises the mixing tank as disclosed in U.S. Pat. No. 
4,747,691 which is herein incorporated by reference as if copied in its 
entirety. Additionally I have enlarged the aging tank and provided baffles 
to prevent direct channeling of the diluted polymer from the inlet to the 
outlet of the aging. tank. To make a more compact unit, I have mounted the 
mixing tank, polymer pump, and water rotameter on top of the aging tank, 
all of which may be skid mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the FIGS. where like numerals indicate like components, 
the preferred embodiment of the invention is shown. 
In FIG. a general flow diagram, the polymer which is carried in an oil 
based liquid, is stored in agitated storage tank 1. The agitator comprises 
an impeller 29 on a shaft 3 which is driven by motor 2 through coupling 
2a. Lid 1b is provided to pour the concentrated polymer into the tank. 
The suction of a metering pump 4 is connected by flow line 5 to the tank 1 
The polymer/carrier is metered and pumped through flow line 7 to the 
polymer inlet 16 of mixing tank 9. Water is taken from a pressurized 
source 11 such as a city water system through flow line 10. A hand valve 
13 in line 10 is provided to turn on the water when needed. A pressure 
regulator 12 in the line 10 assures a constant pressure source of water. 
Rotameter 14 is provided to monitor the water flow rate. The rotameter is 
provided with a needle valve 15 to adjust the water flow rate. Flow line 
10 is connected to water inlet 8 in mixing tank 9. 
The mixing tank 9 has an agitator 17 which is driven by motor 18 through 
coupling 19. The water and polymer/carrier enter though inlets 8 and 16 
respectively, and are mixed together by agitator 17 until the polymer is 
dispersed in the water. The size of the mixing tank should be such that 
the polymer/carrier and water reside under the influence of the agitator 
for between 30-45 seconds. Less time would result in insufficient 
dispersion of the polymer/carrier in the water, and longer periods will 
break up the by then uncoiling polymer chains. 
The continuous flow of water and polymer/carrier carries the diluted 
polymer by pressure through the mixing tank where it exits nears the top 
at mixing tank outlet 20 into flow line 21 which carries the diluted 
polymer to the aging tank 23. The diluted polymer enters the aging tank 
through inlet 22 where it is allowed to reside for 2-10 minutes to allow 
the long polymer chains to uncoil and become activated. After activation 
in the aging tank 23 the diluted polymer exit the aging tank through 
outlet 24 where is carried to the desired service through flow line 25. 
Internal baffles 26a-26d insure that the incoming diluted polymer flows 
through the entire volume of the aging tank instead of simply channeling 
out through the outlet. 
The volume of the mixing tank 9 and aging tank 23 are selected upon the 
amount of polymer required and dilution desired. Usually the water flow is 
greatly in excess of the polymer/carrier and determines the residence time 
in each vessel. Knowing the water flow can thus normally allow one of 
ordinary skill to calculate the volume required to provide the required 
residence times in each of the tanks. 
FIG. 2 show the arrangement of the present invention as mounted on skid 27. 
Since the residence time required in the aging tank 23 is much longer than 
that required in the mixing tank 9, the volume is much greater. For 
convenience and compactness, the mixing tank along with metering pump 4 
and rotameter 14 are mounted on top of the aging tank 23. The storage tank 
1 for the concentrated polymer is shown mounted on legs 1a next to skid 
27. 
For a detailed description of the mixing tank 9 the reader is referred to 
U.S. Pat. No. 4,747,691 at column 3 line 33 to column 4 line 17 read in 
conjunction with FIG. 3 thereof, all of which is specifically incorporated 
by reference. The major difference between this invention and that 
disclosed in U.S. Pat. No. 4,747,691 is that the second cylindrical tank 
23 (aging tank) shown in FIG. 3 thereof is not required since it has been 
replaced. 
In operation and as illustrated in FIGS. 1 and 2, the concentrated polymer 
and carrier is loaded into the agitated storage tank 1 and the agitator 29 
started by starting the agitator motor 2. The water delivery line 10 is 
connected to a suitable water source 11 such as a pressurized city water 
supply. The valve 13 is opened fully to supply water pressure to the 
system. The needle valve 15 on the rotameter 14 is then opened and 
adjusted to achieve the desired water flow rate. This allows the water to 
flow through flow line 10 and into water inlet 8 of mixing tank 9. 
When the mixing tank 9 is filled with water, water flows out of outlet 20 
at the top of the mixing tank 9 through flow line 21 and into the aging 
tank 23 through inlet 22. Finally, when the aging tank 23 is completely 
filled with water, water flows out through outlet 24 into flow line 25 to 
the service. When the desired water flow rate has been achieved, the 
agitator 17 in the mixing tank 9 may be started by starting the motor 18. 
The flow of concentrated polymer and carrier may then be started by 
starting the metering pump 4 and setting it at the desired flow rate to 
achieve the desired dilution. The metering pump 4 takes suction from the 
storage tank 1 through the suction line 5 and pumps the concentrated 
polymer at precise rates through discharge line 7 and then through the 
polymer inlet 16 and check valve 132 into the agitated mixing tank 9 where 
it is mixed for 30-45 seconds and dispersed into the water. 
The diluted polymer is then carried by the water through the outlet 20 and 
into the flow line 21 and thus to the aging tank 23 through inlet 22. The 
volume of the aging tank allows a residence time of from 2-10 minutes to 
allow the polymer chains to uncoil and expose the active sites. Finally, 
the diluted polymer flows through outlet 24 through flow line 25 to the 
service where it may be injected in the water treating facilities. 
It should be realized that the above description is only one embodiment of 
the invention and is for illustration purposes. Many minor modifications 
may be made which fall within the scope of the appended claims.