SQM’s Thermo-solar salts specifications

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SQM offers to the CSP industry high quality Sodium Nitrate and Potassium Nitrate grades to match the specific requirements of each CSP power plant developer. The composition of these grades is described in the individual specifications sheets and is summarized in the table here below.

Parameters

Units

Thermo-Solar Grade Products

Purity NaNO3/KNO3

% min

99.5

99.6

Total Chlorine (1) as Cl

% max

0.1

0.10

Chlorine Cl

% max
typical

0.08
0.05

0.10
0.05

Perchlorate ClO4

% max

0.035

0.01

Magnesium Mg

% max

0.02

0.01

Nitrite NO2

% max

0.02

0.02

Sulphate SO4

% max

0.10

0.05

Carbonate CO3

% max

0.10

0.02

Hydroxil OH

% max

0.05

0.05

Moisture (2) H2O

% max

0.1

0.1

(1) The product does not contain other relevant sources of halogen compounds (iodide, bromide, iodate, bromate or any other).
(2) Moisture measured at SQM production site. Some absorption of moisture may occur during transportation.
Particle size guaranteed: 2mm. Insoluble particles between 0.85 mm and 2 mm represent typically less than 0.05% of the product.
Classification according to Regulation (EC) No 1272/2008 and the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).
Potassium nitrate: Oxidising solid, category 3.
Sodium nitrate: Oxidising solid, category 3. Irritating to eyes, category 2.

SQM thermo-solar salts: clean solutions from natural resources.
Our main corporate mission is to manufacture, from our own natural resources, real added-value products that sustain the growth of the businesses of our clients.

SQM has the largest mining operations in Northern Chile where the world's biggest natural reserves of iodine, sodium nitrate, lithium and potassium concentrations are currently recorded.These abundant raw materials are located very close to the surface, which allows for extensive extraction and processing in a both cost-effective and environmentally friendly way.

Because of our unparalleled vast reserves and the very high quality of our natural resources, our experience in CSP projects and the fact that we are dedicated business partners in many industries worldwide, SQM should be your natural choice when it comes to reliable CSP solutions based on thermo-solar salts.

More info :
solar_salts@sqm.com
Links of interest :


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SQM Thermo-solar salts have given positive results on corrosion already many years ago during the Solar Two project. In more recent measurements, Sandia National Laboratories in USA has concluded that at 600°C bulk molten salt temperature, the corrosion rate ranged was on average less than 16.5 microns of metal loss per year for 13 different alloys after 3000 hours of tests (table below) with only one alloy exceeding 25 microns. Most industrial applications would label that as excellent corrosion performance (ref. SAND 2013-2526, March 2013). Below a snapshot table extracted from this report summarizing the results.

Alloy

Alloy Density
[g/cm³]

Descaled Loss*
[mg/cm²]

Metal Loss*
[µm/year]

321SS

7.94

4.59

15.9

347SS

8.03

2.59

10.4

253MA

7.8

10.31

38.6

HA556

8.23

5.9

20.8

RA330

8.22

4.8

16.2

S35140

7.96

2.4

8.8

332Mo

8.13

3.4

12.2

HR120

8.07

4.97

18

HR120

8.07

4.97

18

HR224

2.27

8.3

HA230

8.97

7.25

23.6

HA214

8.05

1.56

5.7

In625

8.44

4.86

16.8

HA242

9.05

5.88

18.98

*Based off of 3000 hour data (Equation 3) a. alloy density assumed

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SQM’s Thermo-Solar Salts.

Reference: A.V. Zavoico, SAND2001-2100 Solar Power Tower Design Basis Document - Courtesy of Sandia National Laboratories Albuquerque, New Mexico 87185 and Livermore, California 94550 - July 2001).For this specific application, Sodium Nitrate and Potassium Nitrate are mixed in 60%/40% by weight ratio. The mixture is stable in air and has a low vapour pressure.

Phase change properties of Nitrate Salts.

SQM’s Molten Thermo-Solar Salts can be used over a temperature range of 260 °C (500 °F) to approximately 621 °C (1150 °F). As temperature decreases, the salts start to crystallize at 238 °C (460 °F) and solidify at 221 °C (430 °F).Heat of fusion (based on the average of heat of fusion of each component): hsl = 161 kJ/kg.Change in density upon melting: ∆V/Vsolid = 4.6% => Vliquid = 1.046 Vsolid

Thermal and fluid properties of Molten Thermo-Solar Salts mixture (60% NaNO3 + 40% KNO3) as a function of temperature.

Temp.
(°F)

Density
(lbm/ft³)

Specific
Heat
(Btu/lbm-F)

Absolute
Viscosity
(lbm/t-hr)

Thermal
Conductivity
(Btu/hr-t-F)

500

120.10

0.356

10.506

0.285

550

118.98

0.358

8.607

0.288

600

117.87

0.359

7.085

0.291

650

116.76

0.360

5.894

0.294

700

115.65

0.361

4.987

0.297

750

114.54

0.362

4.320

0.300

800

113.43

0.363

3.845

0.303

850

112.32

0.364

3.518

0.307

900

111.21

0.366

3.291

0.310

950

110.10

0.367

3.121

0.313

1000

108.99

0.368

2.960

0.316

1050

107.88

0.369

2.762

0.319

1100

106.77

0.370

2.483

0.322


Temp.
(°C)

Density
(kg/m³)

Specific
Heat
(Joule/kg °C)

Absolute
Viscosity
(mPa-sec)

Thermal
Conductivity
(W/m-c)

260

1924.64

1488

4.343

0.492

288

1906.97

1492

3.558

0.498

316

1889.31

1497

2.929

0.503

343

1871.64

1502

2.436

0.508

371

1853.97

1507

2.062

0.514

399

1836.31

1512

1.786

0.519

427

1818.64

1516

1.589

0.524

454

1800.97

1521

1.454

0.529

482

1783.31

1526

1.361

0.535

510

1765.64

1531

1.290

0.540

538

1747.97

1535

1.223

0.545

566

1730.31

1540

1.142

0.550

593

1712.64

1545

1.026

0.556


Property formulas of fluid Nitrate Salts as a function of temperature between 300 °C (570 °F) and 600 °C (1110 °F).

Density
ρ (lbm/ft³) = 131.2 - 0.02221 x T (°F)
ρ (kg/m³) = 2090 - 0.636 x T (°C)

Cp (Btu/lbm-F) = 0.345 + (2.28 x 10-5) x T (°F)
Cp (J/kg-°C) = 1443 + 0.172 x T (°C)

Absolute Viscosity
µ (lbm/ft-hr) = 60.28440 - 0.17236 x T (°F) + (1.76176 x 10-4) x (T (°F))2 − (6.11408 x 10-8) x (T (°F))³
µ (mPa-sec) = 22.714 - 0.120 x T (°C) + 2.281 x 10-4 x (T (°C))2 − 1.474 x 10-7 x (T (°C))³

Thermal Conductivity
k (Btu/hr-ft-°F) = 0.253208 + 6.26984 x 10-5 x T (°F)
k (W/m-°C) = 0.443 + 1.9 x 10-4 x T (°C)

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