Safe Dissolution of Caustic Soda Flakes & Pearls (NaOH 99%): Controlling Exothermic Heat (ΔH = -44.5 kJ/mol) Against Boil-Over
Table of contents
Dissolving solid Caustic Soda Flakes or Pearls (NaOH 99%) into industrial alkaline solutions (5% – 32% w/w) is a routine daily operation across wastewater plants, textile mills, paper mills, and food CIP lines. However, hydrating solid NaOH releases 44.51 kJ/mol (1,113 kJ per 1 kg of NaOH), capable of spiking tank temperatures by +50 °C to +85 °C within minutes. Following mass-based makeup tables, installing an upper stainless steel dissolving basket, capping bath temperature at ≤ 60–65 °C, and enforcing strict EHS eye protection are mandatory to prevent caustic boil-over and plastic tank failure.
1. Thermodynamics of NaOH Dissolution (ΔH = -44.51 kJ/mol) & 5%–50% Specific Gravity Table
- Exothermic Dissolution Reaction:
NaOH (solid) + H₂O → Na⁺ (aq) + OH⁻ (aq)(ΔH_sol = -44.51 kJ/mol = -1,113 kJ/kg NaOH)
Table 1: Specific Gravity, Baume, Makeup Recipe for 1,000 L (1 m³) NaOH Solution & Adiabatic Heat Rise
Target Concentration (% w/w NaOH) | Specific Gravity at 20 °C (d, kg/L) | Baume Degree (°Be) | Mass of NaOH 99% per 1,000 L (kg) | Equivalent 25 kg Bags (per 1,000 L) | Volume of Cold Water Added First (L) | Final Temp Starting from 25 °C Water (T_max) | Freezing / Crystallization Point (°C) |
|---|---|---|---|---|---|---|---|
5.0% | 1.054 | 7.4 °Be | 53.2 kg | ~2.1 bags | 1,000.8 L | 38.8 °C (Mildly warm) | -4.2 °C |
10.0% | 1.109 | 14.2 °Be | 112.0 kg | ~4.5 bags | 997.0 L | 53.2 °C (Warm) | -10.0 °C |
15.0% | 1.164 | 20.4 °Be | 176.4 kg | ~7.1 bags | 987.6 L | 68.5 °C (Hot) | -21.0 °C |
20.0% | 1.219 | 26.0 °Be | 246.3 kg | ~9.9 bags | 972.7 L | 84.6 °C (Very hot) | -26.2 °C (Eutectic min) |
25.0% | 1.274 | 31.2 °Be | 321.7 kg | ~12.9 bags | 952.3 L | 101.4 °C (Incipient boiling!) | -15.5 °C |
32.0% (Commercial Liquid) | 1.349 | 37.5 °Be | 436.0 kg | ~17.4 bags | 913.0 L | > 115 °C (Boils if single batch!) | +7.5 °C |
45.0% | 1.478 | 46.9 °Be | 671.8 kg | ~26.9 bags | 806.2 L | > 135 °C (Prohibited without cooling) | +5.0 °C |
50.0% | 1.525 | 49.9 °Be | 770.2 kg | ~30.8 bags | 754.8 L | > 145 °C (Prohibited manual batch) | +12.5 °C (Freezes in winter) |
2. Preventing Bottom Caking (NaOH·H₂O) & Why Plants Switch to Liquid NaOH 32%
- Cap Uncooled Single-Batch Dissolution at
10% – 15% w/w: Keeps bath temperature below65 °C, protecting standard PP/HDPE tanks from thermal softening. - Use a Top-Suspended Stainless Steel Dissolving Basket (
SUS304 / SUS316,3–5 mmmesh): Holds solid flakes/pearls15–20 cmbelow the waterline in the high-velocity impeller zone, preventing monohydrate (NaOH·H₂O) bottom caking. - Economic & Safety Advantage of Liquid Caustic Soda
NaOH 32%: For plants consuming≥ 3–5 tons/month, purchasing pre-cooled commercialNaOH 32%in1,000 LIBC totes or5–30-tonbulk tankers saves15–25%per dry-ton equivalent and eliminates manual bag-handling hazards.
3. Six-Step EHS Standard Operating Procedure for Dissolving NaOH 99%
- Step 1 — Mandatory Alkaline PPE: Tight-fitting chemical splash goggles + full face shield (alkali saponifies corneal tissue within
10–30 seconds), inorganic dust respirator, elbow-length Nitrile/Neoprene gloves, PVC apron, and rubber boots. - Step 2 — Verify Emergency Eyewash & Shower Station: Must be within
10 metersand capable of delivering15–20 minutesof continuous flushing. - Step 3 — Fill 100% of Cold Water (
≤ 28–30 °C) into the Tank First: Strictly NEVER pour water onto dry solid NaOH! - Step 4 — Start Mechanical Agitator (
80–150 rpm) & Exhaust Hood. - Step 5 — Feed
NaOH 99%Gradually into the Dissolving Basket: Add10–12 kgincrements every2–3 minutes, keeping bath temperature≤ 60–65 °C. - Step 6 — Cool & Verify Specific Gravity (
°Be): Mix for15 minutesafter the final addition, cool to ambient temperature, and verify density against Table 1.
4. ZDHC MRSL v3.1 Certified NaOH 99% Flakes/Pearls & NaOH 32%–50% Supply by Loc Thien Chemical
Loc Thien Investment Development Co., Ltd. (LOC THIEN INVESTMENT DEVELOPMENT COMPANY LIMITED — Tax ID: 0313650856) is a specialized commercial supplier and distributor of industrial chemicals across Vietnam:
- Official
ZDHC MRSL Version 3.1 Conformance Level 1Certification:NaOH(Sodium Hydroxide) supplied by Loc Thien holdsCERTIFICATE (ZDHC MRSL Conformance Level 1)No.ZDHC1 127736 0001 Rev. 00(Test Report No.2486017672-Q24VPS-CHM2869) issued byTÜV SÜD Product Service GmbH/TÜV SÜD Vietnam. - Complete Product Line: Caustic Soda Flakes
NaOH 99%(25 kgbags), Caustic Soda PearlsNaOH 99%(Taiwan/Thailand), and Liquid Caustic SodaNaOH 32%–50%(30 kgcans,1,000 LIBCs,5–30-tontankers). - 6 Strategic Warehouses (
3,000+ tons/month) & Delivery SLA: Ba Ria - Vung Tau (Phu My 1 IP), Dong Nai (Long Thanh IP), Binh Duong (Di An City), Da Nang (Hoa Khanh IP), Can Tho (Tra Noc IP), and Bac Ninh (Tien Son IP). Headquarters:452/6B Tinh Lo 10, Binh Tri Dong Ward, Binh Tan District, Ho Chi Minh City. Technical quotation within15 minutes; delivery within4 hoursin inner HCMC,24–48 hoursacross Southern & Mekong Delta industrial zones, and2–3 daysin Northern & Central Vietnam. Contact hotline 0979 891 929 for detailed delivery procedures.
Related Technical Resources & Products
- Product Pages: Caustic Soda Flakes NaOH 99% | Caustic Soda Pearls NaOH 99% Taiwan | Liquid Caustic Soda NaOH 32%–50%
- GHS Safety Data Sheets (MSDS): MSDS Solid Caustic Soda NaOH 98%–99% | MSDS Liquid Caustic Soda NaOH 32%
- Technical Inquiry & 15-Minute Quotation: Hotline
0979 891 929(tel:0979891929) — Email:[email protected].
