Induction times induced in an RO system by antiscalants delaying. Induction time model, страница 4

He et al.           Magnetically            Bulk of 3M       1.5–4.3    Turbidity

[14]                  stirred (300 rpm)    NaCl           measurejacked glass              solution      ments reactor

Klepetanis Double-walled              Solution     1.5–4.8      Solution et al. [15]            glass vessel                   bulk            conductivity

decline

Keller         Droplet       Solution     4.3–6.0      Photoet al. [16]                    nucleation bulk            micrograph

None                            25                  (32.4)       20.5       1.21     4.75

                            50                  (38.0)       24.0       0.94     3.53

                            70                  (40.5)       25.6       0.66     2.47

                            90                  (52.5)       33.1       0.87     0.74

None                            20                  7.16            4.88 30      5.44  4.43

                            45                                                   2.55     5.12

                            60                                                   0.33     7.51

None                            22                  (37.9)       23.9       16.3     2.41

                            28                  (36.6)       23.1               24.2 !2.31

                            34                  (32.8)       20.7               26.8 !5.36

                            40                  (34.2)       21.6               8.44 !0.12

4.2. Feed water and antiscalants

The CaSO₄ scaling threshold tests were carried out with solutions simulating the Ca⁺², Mg⁺² and SO₄^!2 contents of Nur Springs raw water [17]. Nur Springs water contains 21.8 mM Ca⁺², 12.3 mM Mg⁺² and 9.7 mM SO₄^!2 and reaches saturation with respect to CaSO₄ at a 30% water recovery. Feed solutions were prepared by dissolving CaCl₂ and MgSO₄ in distilled water.

Table 2 shows the composition of Nur Springs concentrates at various water recovery levels. The CaSO₄ supersaturation ratio covered in the experiments was in the range of 1.6–5.2. The corresponding total salinity was in the range of 10–13 g/L (osmotic pressure of 5–7 bar).

Five different antiscalants (Table 3) were tested at two concentration levels of 6 and

12 ppm, respectively, based on zero recovery

Recovery

0%

Recovery 30%

Recovery 50%

Recovery 70%

Recovery 90%

Mg⁺², mmol/L

9.7

13.8

19.2

31.1

90.4

Ca⁺², mmol/L

21.8

31.1

43.4

70.2

203.7

SO₄^!2, mmol/L

9.7

13.8

19.2

31.1

90.4

Cl^!, mmol/L

43.7

62.2

86.7

140.4

407.5

Ionic strength, mol/L

0.1

0.15

0.21

0.34

0.97

CaSO₄ saturation level, %

64

99.2

150.2

276

1044

Osmotic pressure, bar

1.73

2.8

3.9

5.57

16.16