Process for producing an aqueous polyacrylamide concentrate

Abstract

Process for producing aqueous polyacrylamide concentrates by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel, comminuting said aqueous polyacrylamide gel and mixing it with an aqueous liquid, wherein the manufacturing steps are allocated to two different locations A and B and the process comprises the step of transporting an aqueous polyacrylamide concentrate hold in a suitable transport unit from a location A to a location B. Modular, relocatable plant for manufacturing aqueous polyacrylamide, wherein the units of the plant are located at two different locations A and B.

Claims

1. A process for producing an aqueous polyacrylamide concentrate by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel and mixing said aqueous polyacrylamide gel with an aqueous liquid, characterized in that the process comprises at least the following steps: [1]Radically polymerizing an aqueous monomer solution in the presence of suitable initiators for radical polymerization under adiabatic conditions in a polymerization unit at a location A, wherein the aqueous monomer solution comprises at least water and 15% to 50% by weight-relating to the total of all components of the aqueous monomer solution-of water-soluble, monoethylenically unsaturated monomers at a location A, wherein said water-soluble, monoethylenically unsaturated monomers comprise at least acrylamide, thereby obtaining an aqueous polyacrylamide gel which is hold in the polymerization unit, [2]removing the aqueous polyacrylamide gel from the polymerization unit at the location A, [3] comminuting the aqueous polyacrylamide gel and mixing it with an aqueous liquid at the location A, thereby obtaining an aqueous polyacrylamide concentrate having a concentration of 1.0 to 14.9% by weight of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate, [4] transporting the aqueous polyacrylamide concentrate in a transport unit having a volume from 1 m.sup.3 to 40 m.sup.3 by transport means selected from the group of trucks, railcars or ships from location A to a different location B, and [5]removing the aqueous polyacrylamide concentrate from the transport unit at the location B.

2. The process according to claim 1, wherein the concentration of the aqueous polyacrylamide concentrate is from 2.1 to 10% by weight of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate.

3. The process according to claim 1, wherein the concentration of the aqueous polyacrylamide concentrate is from 3.1 to 7% by weight of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate.

4. The process according to claim 1, wherein step [1] is performed in a polymerization unit comprising a cylindrical upper part, a conical part at its lower end, feeds for the aqueous monomer solution, a bottom opening for removing the polyacrylamide gel, and means allowing to deploy the polymerization unit in a vertical manner.

5. The process according to claim 4, wherein the aqueous polyacrylamide gel is removed from the polymerization unit by applying gas pressure onto the gel and pressing it through the bottom opening.

6. The process according to claim 1, wherein comminuting the aqueous polyacrylamide gel in course of step [3] is carried out by conveying the aqueous polyacrylamide gel through at least one comminution unit together with an aqueous liquid thereby yielding a mixture of pieces of aqueous polyacrylamide gel in an aqueous polyacrylamide solution.

7. The process according to claim 6, wherein the at least one comminution unit comprises means for comminuting aqueous polymer gels selected from static cutting devices, dynamic cutting devices, perforated plates, static mixers, water-jet cutting devices or combinations thereof.

8. The process according to claim 6, wherein at least one of the at least one comminution unit is a water-jet cutting device.

9. The process according to claim 6, wherein the process comprises an additional step of homogenizing the mixture of pieces of aqueous polyacrylamide gel in an aqueous polyacrylamide solution by transferring the mixture to a vessel and allowing the mixture to stand in the vessel, or mixing the contents of the vessel by suitable mixing means.

10. The process according to claim 1, wherein the transport unit has a volume from 10 to 30 m.sup.3.

11. The process according to claim 1, wherein the transport unit is an ISO tank container.

12. The process according to claim 1, wherein the transport unit is a tank fixed on a truck which comprises an outlet at the rear end of the truck and means for tilting the tank.

13. Process according to claim 1, wherein the transport unit is filled by pumping the aqueous polyacrylamide concentrate into the transport unit.

14. The process according to claim 1, wherein the process comprises an additional step [6] of diluting the aqueous polyacrylamide concentrate with an aqueous liquid at the location B.

15. The process according to claim 1, wherein the acrylamide needed for the process is obtained by hydrolyzing acrylonitrile in water in the presence of a biocatalyst capable of converting acrylonitrile to acrylamide.

16. The process according to claim 1, wherein the process comprises an additional step [0] conducted at location A comprising hydrolyzing acrylonitrile in water in the presence of a biocatalyst capable of converting acrylonitrile to acrylamide, thereby obtaining an aqueous acrylamide solution, and wherein said aqueous acrylamide solution is used for making the aqueous monomer solution for step [1].

17. A process for producing an aqueous polyacrylamide concentrate by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel and mixing said aqueous polyacrylamide gel with an aqueous liquid, characterized in that the process comprises at least the following steps: [1] radically polymerizing an aqueous monomer solution in the presence of suitable initiators for radical polymerization under adiabatic conditions in a polymerization unit at a location A, wherein the aqueous monomer solution comprises at least water and 15% to 50% by weight-relating to the total of all components of the aqueous monomer solution-of water-soluble, monoethylenically unsaturated monomers at a location A, wherein said water-soluble, monoethylenically unsaturated monomers comprise at least acrylamide, wherein the polymerization unit comprises a cylindrical upper part, a conical part at its lower end, feeds for the aqueous monomer solution and a bottom opening, thereby obtaining an aqueous polyacrylamide gel which is hold in the polymerization unit, [2] removing the aqueous polyacrylamide gel from the polymerization unit through the bottom opening by means of gas pressure at the location A, [3] comminuting the aqueous polyacrylamide gel and mixing it with an aqueous liquid at the location A, thereby obtaining an aqueous polyacrylamide concentrate having a concentration of 1.0 to 14.9% by weight of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate, [4] transporting the aqueous polyacrylamide concentrate in a transport unit having a volume form 1 m.sup.3 to 40 m.sup.3 by transport means selected from the group of trucks, railcars or ships from location A to a different location B, and [5] removing the aqueous polyacrylamide concentrate from the transport unit at the location B.

18. A process for producing an aqueous polyacrylamide concentrate by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel and mixing said aqueous polyacrylamide gel with an aqueous liquid, characterized in that the process comprises at least the following steps: [1] radically polymerizing an aqueous monomer solution in the presence of suitable initiators for radical polymerization under adiabatic conditions in a polymerization unit at a location A, wherein the aqueous monomer solution comprises at least water and 15% to 50% by weight-relating to the total of all components of the aqueous monomer solution-of water-soluble, monoethylenically unsaturated monomers, wherein said water-soluble, monoethylenically unsaturated monomers comprise at least acrylamide, wherein the polymerization unit comprises a cylindrical upper part, a conical part at its lower end, feeds for the aqueous monomer solution and a bottom opening, thereby obtaining an aqueous polyacrylamide gel which is hold in the polymerization unit, [2] removing the aqueous polyacrylamide gel from the polymerization unit through the bottom opening by means of gas pressure, [3] conveying the aqueous polyacrylamide gel through at least one comminution unit together with an aqueous liquid thereby yielding a mixture of pieces of aqueous polyacrylamide gel in an aqueous polyacrylamide solution followed by homogenization of the mixture obtained by transferring the mixture to a vessel and allowing the mixture to stand in the vessel, or mixing the contents of the vessel by suitable mixing means, thereby obtaining an aqueous polyacrylamide concentrate having a concentration of 3.1 to 14.9% by weight of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate.

19. A modular, relocatable plant for manufacturing aqueous polyacrylamide concentrates by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel and mixing said aqueous polyacrylamide gel with an aqueous liquid, comprising at least at a location A a relocatable storage unit for an aqueous acrylamide solution, optionally relocatable storage units for water-soluble, monoethylenically unsaturated monomers different from acrylamide, a relocatable storage unit for polymerization initiators, a relocatable monomer make-up unit for preparing an aqueous monomer solution comprising at least water and acrylamide, a relocatable polymerization unit for polymerizing the aqueous monomer solution in the presence of polymerization initiators, a relocatable unit for comminution of the aqueous polyacrylamide gel and mixing it with an aqueous liquid thereby obtaining an aqueous polyacrylamide concentrate, at locations A or B a transport unit for transporting an aqueous polyacrylamide concentrate from location A to location B, at a location B means for removing the aqueous polyacrylamide concentrate from the transport unit.

20. A modular, relocatable plant according to claim 19, wherein the plant additionally comprises a dissolution unit at location B.

21. The modular relocatable plant according to claim 19 wherein the relocatable comminution unit comprises at least one means selected from rotating water-jets, rotating knives or and a hole perforation plate.

22. A modular, relocatable plant for manufacturing aqueous polyacrylamide concentrates by polymerizing an aqueous solution comprising at least acrylamide thereby obtaining an aqueous polyacrylamide gel and mixing said aqueous polyacrylamide gel with an aqueous liquid, comprising at least a relocatable storage unit for an aqueous acrylamide solution, optionally relocatable storage units for water-soluble, monoethylenically unsaturated monomers different from acrylamide, a relocatable storage unit for polymerization initiators, a relocatable monomer make-up unit for preparing an aqueous monomer solution comprising at least water and acrylamide, a relocatable polymerization unit for polymerizing the aqueous monomer solution in the presence of polymerization initiators, a relocatable unit for comminution of the aqueous polyacrylamide gel and mixing it with an aqueous liquid thereby obtaining an aqueous polyacrylamide concentrate.

Description

EXAMPLES

(1) The invention is illustrated in detail by the examples which follow.

(2) Polyacrylamide friction reducers to be tested:

Example 1

(3) Aqueous Polyacrylamide Concentrate Made by Mixing an Aqueous Polyacrylamide Gel with an Aqueous Liquid

(4) Step 1:

(5) Preparation of an Aqueous Gel of a Copolymer Comprising 69.4 wt. % (75.0 Mol %) of Acrylamide and 30.6 wt. % (25 Mol %) of Sodium Acrylate Stabilized with 0.25 wt. % Na-MBT Relating to Polymer by Adiabatic Gel Polymerization (Solids Content of 23% by Weight Relating to the Total of the Gel)

(6) A 5 L beaker with magnetic stirrer, pH meter and thermometer was filled with 1600 g of distilled water, 702.04 g of sodium acrylate (35% by weight in water), and 1071.69 g of acrylamide (52% by weight in water). Then 10.5 g of diethylenetriaminepentaacetic acid pentasodium salt (Trilon C; 5% by weight in water), and 4 g of the stabilizer sodium 2-mercaptobenzothiazole (Na-MBT; 50% by weight in water) were added. After adjustment to pH 6.4 with sulfuric acid (20% by weight in water) and addition of the rest of the water to attain the desired monomer concentration of 23% by weight (total amount of water 1690.08 g minus the amount of water already added, minus the amount of acid required), the monomer solution was adjusted to a temperature of approx. −3° C. The solution was transferred to a Dewar vessel, the temperature sensor for the temperature recording was inserted, and the flask was purged with nitrogen for 45 minutes. The polymerization was initiated at 0° C. with 21 g of a 10% aqueous solution of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V-50; 10 h t.sub.1/2 in water 56° C.), 1.75 g of t-butyl hydroperoxide (1% by weight in water) and 1.05 g of a 1% sodium sulfite solution. With the onset of the polymerization, the temperature rose to 54.6° C. within about 63 min. A solid polymer gel block was obtained.

(7) After polymerization, the gel block was incubated 4 hours at 60° C. Then, the block was cut vertically into two pieces. One part was sealed in a plastic bag for use in step 2. The other part was kept for comparative example 2.

(8) Step 2:

(9) Preparation of an Aqueous Polyacrylamide Concentrate (Polymer Concentration: 5 wt. %)

(10) The aqueous polyacrylamide gel obtained in course of step 1 was first chopped to small particles ranging in size from 2 to 5 mm. To give a final concentration of 5.0 weight % polymer, 58.82 g of these chopped particles were then dispersed into a 600 ml beaker containing 241.18 g of distilled water. The gel particles were added while mixing via an overhead mixer with a 75 mm diameter half-moon propeller. The mixing rate was initially set at 300 rpm for the first 5 min, then lowered to 30 rpm for an additional 18 hours.

Comparative Example 1

(11) Inverse Emulsion of Polyacrylamides

(12) Inverse emulsion of a copolymer comprising 69.4 wt. % (75.0 mol %) of acrylamide and 30.6 wt. % (25 mol %) of sodium acrylate stabilized with 0.25 wt. % Na-MBT relating to polymer (solids content 23% by weight relating to the total of the inverse emulsion).

(13) A 600 mL beaker with magnetic stirrer, pH meter and thermometer was charged with 150.44 g of sodium acrylate (35% by weight in water), 128.97 g of distilled water, 229.65 g of acrylamide (52% by weight in water), 0.5 g of diethylenetriaminepentaacetic acid pentasodium salt (Trilon C; 5% by weight in water), and 0.86 g of the stabilizer sodium 2-mercaptobenzothiazole (Na-MBT; 50% by weight in water).

(14) After adjustment to pH 6.4 with sulfuric acid (20% by weight in water), the rest of the water to attain the desired monomer concentration of 23% by weight (total amount of water 138.61 g minus the amount of water already added, minus the amount of acid required) was added.

(15) A high 1 L beaker was charged with 12.2 g sorbitan monooleate (Span® 80) and 189.9 g of a high-boiling dearomatized hydrocarbon mixture (Exxsol® D100) was added and stirred with a spatula.

(16) The beaker with the oil solution was fixed in a Silverson high shear mixer. While mixing the oil solution at 4000 rpm, the aqueous solution was poured in quickly. Then, the Silverson high shear mixer is turned up to 8000 rpm for 2 min 48 sec.

(17) The emulsion was transferred to a double jacketed reactor, stirred at 200 rpm and adjusted to the initiation temperature of 10° C. During this time the emulsion was purged with nitrogen (for 60 minutes). The polymerization was drop-wise initiated with 9 g of a 0.1% sodium bisulfite solution and 5 g of 0.1% t-butyl hydroperoxide solution. The initiators were added with a squeezing pump, controlled by hand. When the respective 0.1% solutions were empty, the initiators were changed to 9 g of a 1% sodium bisulfite solution and 5 g of a 1% t-butyl hydroperoxide solution. Thereby, the temperature rose 1° C. per minute up to 40° C., from there the temperature was maintained at 40° C. When the second initiator was added completely, the emulsion was stirred for additional 60 minutes at 40° C. The emulsion was then filtered through a 190 μm filter.

(18) Activation of the Inverse Emulsion

(19) The activation was carried out 24 h prior to use in the Friction Loop experiment. For activation, 97.75 g of the inverse emulsion was poured in a glass beaker and stirred with an over-head stirrer at 650 rpm. With a 5 mL plastic syringe, 2.25 g of a commercially available activator was added at once to the vortex of the inverse emulsion. The mixture was stirred for additional 8 minutes.

Comparative Example 2

(20) Aqueous Polyacrylamide Concentrate Made by Mixing Polyacrylamide Powder with an Aqueous Liquid

(21) Step 1:

(22) Preparation of an Aqueous Gel of a Copolymer Comprising 69.4 wt. % (75.0 Mol %) of Acrylamide and 30.6 wt. % (25 Mol %) of Sodium Acrylate Stabilized with 0.25 wt. % Na-MBT Relating to Polymer by Adiabatic Gel Polymerization (Solids Content of 23% by Weight Relating to the Total of the Gel)

(23) Step 1 was carried out in the same manner as in example 1. A part of the polymer gel obtained in step 1 of example 1 was used for example 1 and the other part for the present comparative example 2.

(24) Step 2:

(25) Drying the Aqueous Gel

(26) The gel obtained in example 1 was comminuted with a meat grinder. The particles were dried for two hours at 55° C. in a fluid bed dryer. After drying, the dried particles were grinded in a lab mill and filtered with a 1 mm sieve. A polyacrylamide powder with an active content of 94.6% by weight (the remainder being moisture) was obtained.

(27) Step 3:

(28) Preparation of an Aqueous Polyacrylamide Concentrate (Polymer Concentration: 5 wt. %)

(29) An amount of 284.21 g of water was added into a 600 ml beaker while mixing via an overhead mixer with a 75 mm diameter half-moon propeller. The mixing rate was initially set at 300 rpm. Thereafter 15.79 g of the polyacrylamide powder (i.e. the amount to give a final concentration of 5.0 weight % of polyacrylamides in the concentrate) obtained in course of step 2 was slowly added to the vortex over a few seconds to avoid the formation of lumps. After 5 min, the mixing rate was lowered to 30 rpms for an additional 18 hours.

Comparative Example 3

(30) Aqueous Polyacrylamide Concentrate Made by Mixing Polyacrylamide Powder with an Aqueous Liquid

(31) Step 1:

(32) Preparation of an Aqueous Gel of a Copolymer Comprising 69.4 wt. % (75.0 Mol %) of Acrylamide and 30.6 wt. % (25 Mol %) of Sodium Acrylate Stabilized with 0.25 wt. % Na-MBT Relating to Polymer by Adiabatic Gel Polymerization (Solids Content of 30% by Weight Relating to the Total of the Gel)

(33) A 5 L beaker with magnetic stirrer, pH meter and thermometer was filled with 1100 g of distilled water, 915.71 g of sodium acrylate (35% by weight in water), and 1397.85 g of acrylamide (52% by weight in water). Then 10.5 g of diethylenetriaminepentaacetic acid pentasodium salt (Trilon C; 5% by weight in water), and 5.2 g of the stabilizer sodium 2-mercaptobenzothiazole (Na-MBT; 50% by weight in water) were added.

(34) After adjustment to pH 6.4 with sulfuric acid (20% by weight in water) and addition of the rest of the water to attain the desired monomer concentration of 30% by weight (total amount of water 1149.05 g minus the amount of water already added, minus the amount of acid required), the monomer solution was adjusted to a temperature of approx. −3° C. The solution was transferred to a Dewar vessel, the temperature sensor for the temperature recording was inserted, and the flask was purged with nitrogen for 45 minutes. The polymerization was initiated at 0° C. with 21 g of a 10% aqueous solution of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V-50; 10 h t.sub.1/2 in water 56° C.), 1.75 g of t-butyl hydroperoxide (1% by weight in water) and 1.05 g of a 1% sodium sulfite solution. With the onset of the polymerization, the temperature rose to 84.4° C. within about 20 min. A solid polymer gel block was obtained.

(35) After polymerization, the gel block was incubated 4 hours at 80° C. Then, the block was comminuted with a meat grinder. The particles were dried for two hours at 55° C. in a fluid bed dryer. After drying, the dried particles were grinded in a lab mill and filtered with a 1 mm sieve. A polyacrylamide with an active content of 95.0 wt. % was obtained.

(36) Step 2:

(37) Preparation of an Aqueous Polyacrylamide Concentrate (Polymer Concentration: 5 wt. %)

(38) An amount of 284.21 g of water was added into a 600 ml beaker while mixing via an overhead mixer with a 75 mm diameter half-moon propeller. The mixing rate was initially set at 300 rpm. Thereafter 15.79 g of the polyacrylamide powder (i.e. the amount to give a final concentration of 5.0 weight % of polyacrylamides in the concentrate) obtained in course of step 2 was slowly added to the vortex over a few seconds to avoid the formation of lumps. After 5 min, the mixing rate was lowered to 30 rpms for an additional 18 hours.

(39) Friction Loop Apparatus

(40) The friction reduction performance of the friction reducing agent was assessed using a Chandler model M5600 friction loop, which circulates fluid through a section of known diameter pipe to determine the effectiveness and longevity of a friction reducing agent added to a test fluid. Fluid in the loop flows from a ˜37.8 l (˜10 gallon) reservoir through a pump, mass flow meter and then two ˜250 cm (10 feet) long sections of pipe before returning to the reservoir to be recirculated. Pressure drop is measured over the two sections of pipe. One is 1.27 cm outer diameter (½ inch), the other is 1.91 cm outer diameter (¾″ inch), giving different ranges of Reynolds number.

(41) The friction loop was loaded with 37.85 l (10 gallons) of aqueous test fluid (fresh water or brines). The flow rate was set to 37.85 l per minute (10 gallons per minute) and once a stable, initial pressure was recorded. Thereafter, the friction reducing composition to be tested was injected into the vortex of the fluid reservoir using a plastic syringe.

(42) The injection time was taken as the start of the test (time=0 seconds). The subsequent drop in pressure measured the performance of the friction reducing composition. The pressure data from the 1.27 cm pipe is reported, because it reflected a higher Reynolds number than the 1.91 cm pipe.

(43) Pressure data was converted to friction reduction using the formula:

(44) $\%\mathrm{Friction}\mathrm{Reduction}\left(\%\mathrm{FR}\right)=\frac{\mathrm{Initial}\mathrm{Pressure}\mathrm{with}\mathrm{no}\mathrm{FR}-\mathrm{Pressure}\mathrm{with}\mathrm{FR}}{\mathrm{Initial}\mathrm{Pressure}\mathrm{with}\mathrm{no}\mathrm{FR}}$

(45) Friction Loop Tests

(46) 26.08 g of each of the aqueous polyacrylamide concentrates obtained in examples 1 to 3 (each having a concentration of 5 wt. % of polyacrylamides) was used for the friction loop testing. This dosage amount corresponds to a final concentration of 35 ppm polymer once diluted in the friction loop with additional fresh water.

(47) The aqueous polyacrylamide concentrate was added directly to vortex of the friction loop mixing tank at time=0, as mentioned in the above description of the Friction Loop.

(48) 5.67 ml of the activated inverse emulsion sample (comparative example 1) was directly injected into the vortex of the flow loop mixing tank, to achieve also a final concentration of 35 ppm polymer.

(49) All results (percentage of friction reduction vs. time) are summarized in FIG. 17.

(50) Discussion of the Results Obtained

(51) FIG. 17 shows a comparison of the % Friction Reduction of example 1 and comparative examples 1, 2, and 3 as a function of time. Each sample was measured individually under the same experimental conditions and at the same effective dosage concentration.

(52) The aqueous polyacrylamide concentrate obtained from an aqueous gel (example 1) yielded higher maximum friction reduction, as well as at a faster rate when compared to the inverse emulsion (comparative example 1).

(53) Example 1 also gave better results than the two samples prepared from powders (comparative examples 2 and comparative 3) over the 10 min interval.