Process and plant for manufacturing aqueous polyacrylamide gels

Process for making polyacrylamides by polymerizing an aqueous solution comprising at least acrylamide and acrylic acid or salts thereof in the presence of initiators for radical polymerization under adiabatic conditions, wherein the process comprises:

• [1] providing an aqueous solution of acrylic acid or salts thereof in at least one pressure-resistant storage tank (1) having a volume of 10 to 500 m3 and comprising a heat-insulation layer and means for controlling temperature of the aqueous solution in step [1], wherein a concentration of acrylic acid or their salts is from 2.5 mole/kg to 5 mole/kg relating to a total of the aqueous solution in step [1], and wherein step [1] comprises at least the following sub-steps
• [1.1] providing in a transport unit a first liquid chemical product selected from
• pure acrylic acid, or
• an aqueous solution of acrylic acid or a salt thereof having a concentration of more than 5 mol/kg of acrylic acid relating to a total of the aqueous solution in step [1.1],
• [1.2] discharging the first liquid chemical product from the transport unit and diluting it with water in such a manner, that a resultant aqueous solution in step [1.2] has a concentration from 2.5 mole/kg to 5 mole/kg of acrylic acid or salts thereof, relating to the total of the aqueous solution in step [1.2], and
• [1.3] transferring said aqueous solution of acrylic acid or salts thereof having a concentration from 2.5 mole/kg to 5 mole/kg of acrylic acid or salts thereof in step [1.2], to the at least one pressure-resistant storage tank (1), and
• [2] providing an aqueous solution of acrylamide in at least one pressure-resistant storage tank (2) having a volume of 10 to 500 m3 and comprising a heat-insulation layer, means for controlling temperature of the aqueous solution in step [2], wherein a concentration of the aqueous solution is from 2.5 mole/kg to 5 mole/kg of acrylamide relating to the total of the aqueous acrylamide solution in step [2], and wherein step [2] comprises at least the following sub-steps
• [2.1] providing in a transport unit a second liquid chemical product which is an aqueous acrylamide solution having a concentration of more than 5 mol/kg of acrylamide, relating to the total of the aqueous acrylamide solution in step [2.1], and
• [2.2] discharging the second liquid chemical product from the transport unit and diluting it with water in such a manner, that a resultant aqueous acrylamide solution has a concentration from 2.5 mole/kg to 5 mole/kg of acrylamide relating to the total of the aqueous acrylamide solution in step [2.2], and
• [2.3] transferring said aqueous acrylamide solution in step [2.2] to the at least one pressure-resistant monomer storage tank (2),
• [3] preparing an aqueous monomer mix comprising at least water, acrylamide and partially or fully neutralized acrylic acid in a pressure-resistant mixing vessel (3) having a volume of 10 to 150 m3, comprising a heat-insulation layer and means for controlling temperature of the aqueous monomer mix, wherein step [3] comprises at least the following sub-steps
• [3.1] transferring an aqueous solution of acrylic acid or salts thereof from the at least one pressure-resistant storage tank (1) into the pressure-resistant mixing vessel (3),
• [3.2] transferring an aqueous solution of acrylamide from the at least one pressure-resistant storage tank (2) into the pressure-resistant mixing vessel (3),
• [3.3] adding an aqueous base into the pressure-resistant mixing vessel, while mixing components in the pressure-resistant mixing vessel (3) and controlling temperature of the mixture in the vessel (3) to maintain a temperature of not more than 40° C.,
• wherein an amount of all monomers in the aqueous monomer mix is at least 2 moles/kg, relating to the total of all components of the aqueous monomer mix, and
• [4] transferring the aqueous monomer mix prepared in course of step [3] to a pressure-resistant polymerization unit (5) having a volume of 10 to 150 m3, adding initiators for radical polymerization and polymerizing the aqueous monomer mix under adiabatic conditions, thereby obtaining an aqueous polyacrylamide gel.