Concentration of sulfuric acid

A method for fractionating a sulfuric acid process stream comprising:

• providing a process stream (10) comprising at least 1 wt % sulfuric acid,
• providing a treatment system (12) comprising:
• a) a first filtration assembly (20) comprising at least one hyperfiltration stage (100), said first filtration assembly (20) having a first feed inlet (22), a first reject outlet (24), and at least one first permeate outlet (26),
• b) a second filtration assembly (40) comprising at least one hyperfiltration stage (100), said second filtration assembly (40) having a second feed inlet (42), a second reject outlet (44), and at least one second permeate outlet (46),
• c) a third filtration assembly (60) comprising at least one hyperfiltration (100) stage, said third filtration assembly (60) having a third feed inlet (62), a third reject outlet (64), and at least one third permeate outlet (66),
• d) a first pump (80) having a first pump inlet (82) fluidly connected to said process stream (10) or to a junction point (18) which receives said process stream (10), and a first pump outlet (84) fluidly connected to the first feed inlet (22);
• e) a second pump (86) having a second pump inlet (88) fluidly connected to said at least one first permeate outlet (26) and a second pump outlet (90) fluidly connected to said third feed inlet (62), and
• wherein each of said first, second, and third filtration assemblies (20, 40, 60) include modules having membranes that are suitable to pass less than 10% salt in a standard test (2000 ppm NaCl, pH 8, 30 gfd (51.02 lmh), 15% recovery), and
• wherein the treatment system is arranged such that
• f) a first feed stream (28) entering the first feed inlet (22) comprises the process stream (10), a second permeate stream (52) sourced from the at least one second permeate outlet (46), and a third reject stream (70) sourced from the third reject outlet (64),
• g) a second feed stream (48) entering the second feed inlet (42) is fluidly connected to the first reject outlet (24),
• h) a third feed stream (68) entering the third feed inlet (62) is fluidly connected to the at least one first permeate outlet (26);
• and
• activating the first and second pumps (80, 86) to pressurize the first, second, and third feed streams (22, 42, 62) and to generate permeate from each of the first, second, and third filtration assemblies (20, 40 60), such that average passage of the sulfuric acid from the first and third filtration assemblies (20, 60) is less than 30% and the average passage of sulfuric acid from the second filtration assembly (40) is more than 70%;
• and
• producing a first fraction (14) of the process stream (10) that is in fluid communication with the at least one third permeate outlet (66) and has a pH between 4 and 10, and a second fraction (16) of the process stream (10) that is in fluid communication with the second reject outlet (44) and contains at least 20 weight percent of sulfuric acid.