| HS Code | 441328 |
| Product Name | Caustic Soda Flakes |
| Chemical Name | Sodium Hydroxide |
| Chemical Formula | NaOH |
| Cas Number | 1310-73-2 |
| Molecular Weight | 40.00 g/mol |
| Appearance | White flakes |
| Odor | Odorless |
| Purity | 98% min NaOH |
| Melting Point | 318°C |
| Boiling Point | 1388°C |
| Solid Density | 2.13 g/cm3 |
| Bulk Density | 0.7 - 1.0 g/cm3 |
| Solubility In Water | 1110 g/L at 20°C |
| Ph 1 Solution | 13 - 14 |
| Hs Code | 28151110 |
As an accredited DCM Shriram Caustic Soda Flakes factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | DCM Shriram Caustic Soda Flakes are packed in 25 kg HDPE woven bags with inner liner, sealed for safe handling. |
| Container Loading (20′ FCL) | 20′ FCL loaded with DCM Shriram caustic soda flakes in 25kg bags, palletized, shrink-wrapped, and secured for safe transport. |
| Shipping | DCM Shriram Caustic Soda Flakes are shipped in moisture-proof HDPE/PP woven bags with inner liners, typically 25 kg or 50 kg, palletized and shrink-wrapped. Containers must stay dry and well-ventilated, segregated from acids and moisture-sensitive goods. Personnel should wear protective equipment due to the flakes’ corrosive, hygroscopic nature. |
| Storage | Store DCM Shriram Caustic Soda Flakes in a cool, dry, well-ventilated area inside tightly sealed original bags or compatible containers. Keep off the floor on pallets to prevent moisture absorption. Protect from water, humidity, acids, and incompatible materials. Avoid contact with aluminium, zinc, or tin containers. Ensure secure, labeled storage away from direct sunlight. |
| Shelf Life | Shelf life is approximately 2-3 years when stored in airtight, dry conditions away from moisture and air. |
In Bayer plants processing gibbsitic bauxite, digestion-circuit control is based on free-caustic concentration expressed as Na2O equivalent rather than total alkali. DCM Shriram caustic soda flakes are pre-dissolved in weak wash water to 50% w/w before metering into the spent liquor line; the alkali inventory is maintained at 200–250 g/L Na2O equivalent (approximately 258–322 g/L NaOH), and the molar Al2O3/caustic ratio is held between 0.60 and 0.72 for low-temperature gibbsite extraction at 140–150°C. For boehmitic bauxite processed at 200–240°C, the A/C ratio is raised to 0.65–0.75 and digestion pressure reaches 30–35 bar. Make-up flakes addition, after correction for reactive silica losses to sodalite-type desilication product and mud washing losses, typically falls between 40 kg and 150 kg per tonne of smelter-grade alumina produced, with the higher consumption associated with high-silica bauxites containing more than 4% reactive SiO2.
Downstream production steps begin with bauxite grinding to a slurry solids content of 40–55 wt%, followed by single-stream or split-stream digestion in horizontal autoclaves or tube digesters equipped with live-steam injection and slurry heaters. The digested slurry is flashed to atmospheric pressure, diluted with wash water, and clarified in thickeners and security filters operating at 0.5–1.0 m³/m²/h overflow rate; the filtrate is then cooled and seeded with fine gibbsite particles for precipitation over 60–72 h at 70–80°C. The resulting gibbsite is classified, washed, and calcined at 1000–1100°C to produce smelter-grade alumina with a typical loss on ignition of 0.8–1.2% when tested under ISO 806:2004. Terminal product types include smelter-grade alumina for Hall-Héroult cells, chemical-grade alumina trihydrate for flame-retardant fillers, and zeolite A precursors for detergent builders.
Compliance boundaries for Bayer circuits are set by the EU BAT Reference Document for the Non-Ferrous Metals Industries (2017) for liquor loop emissions, and sampling of smelter-grade alumina follows ISO 2927:2002. Occupational exposure to caustic aerosol and particulates must not exceed the ACGIH TLV-C of 2 mg/m³. Published data for the precise distribution of make-up additions in high-temperature diasporic bauxite circuits is limited because digestion conditions vary by bauxite mineralogy.
Kraft mills producing bleachable-grade softwood pulp set effective alkali charge at 18–22% Na2O on oven-dry wood, with sulphidity between 25% and 35%. Hardwood lines operate at 14–18% effective alkali to limit xylan degradation. DCM Shriram caustic soda flakes function outside the recausticising loop as sodium-balance make-up, compensating for sodium losses from electrostatic precipitator dust, green liquor dregs, bleach plant alkaline filtrate, and spillage. Make-up addition commonly ranges from 5 kg to 15 kg NaOH per air-dried tonne of pulp, but the exact dose is determined by the mill sodium/sulfur balance and the deadload sodium carbonate concentration in white liquor, which should remain below 20 g/L Na2O equivalent to avoid suppressed liquor reactivity.
In the production process, black-liquor solids are combusted in a recovery boiler, the smelt is dissolved in weak wash, and green liquor is recausticised with slaked lime at 95–105°C to convert sodium carbonate to sodium hydroxide, producing white liquor with causticising efficiency of 78–85%. Caustic make-up is added after the recausticising loop as a 50% w/w solution to avoid local overheating and calcium carbonate turbidity. Chips are cooked in continuous digesters with H-factor control at 1500–1800 for softwood to target kappa number 25–35 when measured under ISO 302:2015, followed by oxygen delignification and elementally chlorine-free bleaching to final brightness. Terminal product types include bleached softwood kraft pulp, unbleached kraft linerboard, and dissolving pulp for cellulosic derivatives. Intrinsic viscosity limits are verified under ISO 5351:2010, and US effluent guidelines are defined in 40 CFR Part 430.
Mercerising of cotton fabric is a cold caustic process in which DCM Shriram flakes are dissolved on-site and maintained at 220–300 g/L NaOH (20–24°Bé at 15°C) with working bath temperature held at 15–20°C; wetting-agent concentration is controlled at 0.5–1.5 g/L to accelerate alkali penetration into the fibre lumen. Fabric exiting singeing and desizing is held under warp and weft tension while the cotton fibre swells and its cross-section converts from flattened ribbon to circular, after which hot water at 50–70°C removes the bulk caustic and an acid sour containing 2–5 mL/L acetic acid neutralises residual alkalinity. Caustic drag-out is compensated by continuous addition of 25–40 kg DCM Shriram flakes per 100 L of wash water collected for recovery; the recovered weak lye is concentrated in evaporators to 30–35% NaOH for reuse.
Compliance under ZDHC MRSL V3.0 requires that the wetting agent contain no APEO surfactants; the finished textile must meet OEKO-TEX Standard 100 Annex 4 limit values for extractable residues, and EU REACH Annex XVII entry 46a restricts nonylphenol ethoxylates used in the bath. Production equipment is specified in 316L stainless steel or rubber-lined carbon steel because dissolved iron above 5 ppm catalyses oxycellulose formation and strength loss at the fibre surface. Terminal product types include mercerised cotton sewing thread, high-lustre shirting fabric, and warp-knit interlining.
Hot-process saponification converts triglycerides to sodium soap and glycerol; the caustic charge is calculated from the saponification value of the oil blend rather than from a fixed weight-percentage rule. Coconut oil with saponification values of 250–264 mg KOH/g requires 178–188 kg dry NaOH per 1000 kg oil, while palm oil with 195–205 mg KOH/g requires 139–146 kg dry NaOH per 1000 kg oil. A working excess of 0.5–2.0% NaOH above stoichiometry is maintained to drive completion, and the final free alkali in finished soap is reduced to 0.05–0.1% to prevent rancidity and skin irritation.
DCM Shriram flakes are dissolved to 30–35% w/w solution before dosing into the oil phase at 70–80°C; the batch is boiled at 100–105°C, grained with 5–8% NaCl to separate neat soap from spent lye and glycerine, then washed and fitted to a neat soap moisture of 28–32%. Undissolved flakes entering the kettle create local high-pH pockets and dark specks in the soap base, so inline dilution and filtration are used before addition. The soap base is vacuum-dried and plodded into bars. Terminal product types include laundry soap bars, toilet soap base, and industrial soap chips. Compliance under ASTM D460 covers total alkali and moisture determinations, and ISO 16128-1:2016 provides the natural-origin index for oleochemical content. Contact equipment in the saponification and salt-out stages is specified in 316L stainless steel because chlorides from the oil and NaCl graining stage cause pitting corrosion in unalloyed austenitic grades.
Refinery liquid hydrocarbon streams that have been amine-sweetened can still carry residual H₂S and methyl mercaptan above product specification; caustic scrubbing with 8–12 wt% NaOH solution in a fibre-film contactor reduces H₂S to below 5 ppmv and total mercaptan sulfur to below 10 ppmw when measured by ASTM D3227. DCM Shriram flakes are dissolved to a 10–15°Bé solution and circulated at 0.2–0.4 m³ caustic per m³ feed at 30–45°C. The stoichiometric consumption is approximately 2.35 kg NaOH per kg H₂S and 0.83 kg NaOH per kg methyl mercaptan, but spent caustic polysulfide formation and bicarbonate buffering require excess alkalinity to maintain pH >12 at the contactor outlet.
Downstream, spent sulfidic caustic is routed to wet air oxidation at 200–220°C and 35–55 bar, reducing sulfide to <1 mg/L and chemical oxygen demand by more than 85% before biological treatment. Carbon steel contactors and pipework operating above 50°C with NaOH above 5 wt% require post-weld heat treatment or upgrade to 304L stainless steel per NACE SP0403-2017; storage tanks for 50% NaOH at ambient temperature are typically fabricated from lined carbon steel or nickel alloy to avoid caustic stress corrosion cracking. Terminal product types include LPG, light straight-run naphtha, and isomerisation feed meeting copper-strip and doctor-test requirements.
Neutralisation of acidic wastewater streams and regeneration of strong-base anion exchange resin consume the remaining portion of DCM Shriram caustic soda flakes in industrial water treatment. Type I strong-base anion resin is regenerated with 4–6% w/w NaOH at 40–50°C, with a dosage of 64–128 kg NaOH per m³ of resin; the spent regenerant is neutralised to pH 7.0–7.5 before discharge. Acidic effluent streams containing dissolved metal sulfates are treated by pH adjustment to 8.5–10.5 for hydroxide precipitation, using 0.1–1.0 g/L flakes depending on buffering capacity. Terminal product types include demineralised boiler feedwater, softened process water, and pH-corrected plant discharge. Compliance under AWWA B501-19 governs sodium hydroxide supply quality, and NSF/ANSI/CAN 60:2021 certifies the product for drinking-water treatment chemicals. Dissolution must take place in 316L stainless steel or lined tanks with mechanical agitation because heat of solution can exceed 100°C during mixing, and direct contact with aluminium components causes hydrogen evolution and equipment attack.
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DCM Shriram Caustic Soda Flakes is a dry, white, deliquescent solid form of sodium hydroxide with chemical formula NaOH, CAS 1310-73-2, and molar mass 40.00 g/mol. The material is supplied in 25 kg and 50 kg HDPE-lined bags and is classified for transport as UN 1823, Class 8, Packing Group II. Commercial specification typically aligns with IS 252:2013 Grade 1 solid caustic soda and reports total alkalinity as NaOH 99.0–99.5% w/w on dry basis, sodium carbonate as Na₂CO₃ ≤0.5% w/w, sodium chloride as NaCl ≤0.1% w/w, and iron ≤30 mg/kg. Bulk density is 0.9–1.1 g/cm³, and a 1% aqueous solution exhibits pH 13.2–13.8. The anhydrous flakes have a melting point of 318°C and a boiling point of 1388°C.
| Parameter | Unit | Typical commercial value | Test basis |
|---|---|---|---|
| Total alkalinity as NaOH | % w/w | 99.0–99.5 | IS 252:2013, acid titration |
| Sodium carbonate as Na₂CO₃ | % w/w | ≤0.5 | IS 252:2013 |
| Sodium chloride as NaCl | % w/w | ≤0.1 | IS 252:2013 |
| Iron as Fe | mg/kg | ≤30 | acid digestion/ICP-OES |
| Mercury as Hg | mg/kg | ≤0.1 for food-processing grade | FCC monograph |
| Lead as Pb | mg/kg | ≤2 for food-processing grade | FCC monograph |
| Tapped bulk density | g/cm³ | 0.9–1.1 | vendor silo design data |
Addition of anhydrous NaOH flakes to water is strongly exothermic; heat of solution at infinite dilution is −44.5 kJ/mol. When a 20% w/w solution is prepared adiabatically, the temperature rise can exceed 60°C. Make-down vessels should therefore be initially charged with water at 15–30°C and the flakes added slowly under top-entering agitation of 0.5–1.0 kW/m³. Flake thickness in the range 0.5–1.5 mm provides a moderate surface-area-to-volume ratio, producing lower airborne dust than free-flowing prills but requiring longer wetting than 50% lye dilution. On production-scale batches, local crusting at the addition point occurs when flake addition rates exceed 5 kg/min per m² of liquid surface; use of a flake eductor or wetting cone reduces this. The solution should be cooled if the final concentration exceeds 30% w/w to avoid localized boiling. Pump components in caustic service should be 316L stainless steel or fiberglass-reinforced plastic with no aluminum, zinc, or galvanized wetted parts.
The production route for DCM Shriram caustic soda flakes is membrane-cell chlor-alkali electrolysis. Purified brine is electrolyzed in a perfluorinated cation-exchange membrane cell, producing 32% w/w cell liquor with NaCl reduced to low levels before evaporation. The liquor is then concentrated in a multi-effect evaporation train to 98–99% NaOH melt and cooled on a rotating flaker. This route yields lower chlorate and heavy-metal carryover than mercury cell or diaphragm cell methods. The low chloride specification is important in rayon spinning, food processing, and Bayer circuits where chloride promotes corrosion and precipitation.
In high-temperature Bayer digestion of boehmitic bauxite, dry flake caustic is used to maintain free Na₂O in the range 140–180 g/L when the liquor-to-bauxite mass ratio is 4–6. The flakes are pre-dissolved in spent wash or dilute liquor before injection into the digestion train to prevent localized alumina precipitation. The molar ratio of Na₂O to Al₂O₃ in the pregnant liquor after digestion is typically maintained at 1.35–1.55; deviations below 1.30 reduce precipitation yield, while deviations above 1.60 increase caustic loss in red mud washing. Chloride in the flake feed is a critical contaminant in Bayer circuits because chloride concentrations above 0.2 g/L can alter passivation and increase pitting risk in carbon steel digesters. DCM Shriram flake material with NaCl ≤0.1% w/w contributes less than 0.061 kg chloride per 100 kg product, which is acceptable for most refinery liquor balances when combined with regular purging.
Dry flake logistics typically become favorable when total site alkalinity demand is below 1,200–1,500 t/year or when the consuming plant is more than 400 km from a membrane-cell chlor-alkali terminal. Liquid 50% w/w NaOH has a freezing point near 12°C; therefore outdoor storage in northern Indian winter conditions requires tank heating and recirculation. Flake caustic has no free-water phase and is stored at ambient temperature in dry warehouses. The water-free form reduces transported mass by about 50% for equivalent NaOH content and eliminates heated tanker unloading. The operational boundary is humidity: above 20–25% RH, the flake surface sorbs moisture and carbon dioxide to form a sodium carbonate crust. Conveying and storage should use dry-air purge with dew point below −40°C or sealed HDPE-lined bags. Manual bag dumping stations require dust collection with a minimum face velocity of 0.5 m/s to control caustic dust exposure to the ACGIH TLV-C of 2 mg/m³ for sodium hydroxide.
Kraft mill causticizing loops require sodium hydroxide make-up to replace alkali lost in lime mud, knots, and unwashed pulp. Flake caustic is added to weak wash or oxidized white liquor to hold effective alkali at 90–120 g/L as Na₂O and sulfidity at 20–30%. A modern continuous digester processing hardwood chips at 150–165°C operates at a liquor-to-wood ratio of 3.5–4.5 L/kg. The chloride specification of the make-up caustic matters because chloride accumulation above 1 g/L in white liquor increases the risk of stress corrosion cracking in digester and recovery boiler tubes. Using solid flakes with NaCl ≤0.1% w/w minimizes chloride addition without altering the sodium/sulfur balance, unlike sodium sulfate make-up.
Cotton mercerization is run at NaOH concentration 220–280 g/L and bath temperature 15–18°C; at higher temperature the alkali becomes less effective in converting Cellulose I to Cellulose II. The flake product is dissolved to 26–30°Bé strength, and the bath is monitored by titration every 30–60 minutes to hold concentration within ±5 g/L of setpoint. Impurities in caustic soda, particularly chloride and carbonate, alter fiber swelling and dye uptake; membrane-cell flakes with low chloride are therefore preferred over diaphragm-grade solid caustic. Tension mercerization tests such as AATCC TM 89 are used to assess dimensional stability of treated cotton. Recovered wash lye from mercerization can be concentrated to 48–50% NaOH in multiple-effect evaporators and returned to the bath after clarification.
Acid waste neutralization with sodium hydroxide flakes is carried out by preparing 10–20% w/w solution and injecting it into a flash mixer with a residence time of 2–5 minutes. The target discharge pH is set by the site permit, commonly 6.5–9.0; automatic dosing adjusts flow based on pH probes calibrated per ASTM D1293. Control of carbon dioxide absorption in the flake dissolution water is important because absorbed CO₂ forms sodium carbonate, which buffers the pH and can delay endpoint response. For acid streams containing aluminum or zinc, pH overshoot above 9.0 can redissolve amphoteric metal hydroxides and violate total suspended solids permits.
Soap saponification uses sodium hydroxide flakes to saponify triglycerides in fats and oils. The required NaOH charge is calculated from the saponification value of the feedstock; for palm stearin with saponification value 195–205 mg KOH/g, the stoichiometric NaOH demand is approximately 0.139–0.146 kg NaOH per kg oil. A finishing kettle retains free alkali at 0.05–0.10% as NaOH after neat soap separation to avoid rancidity and ensure complete saponification. The low chloride and carbonate content of the flake product reduces the risk of calcium and magnesium salt precipitation when hard water is used for dilution. Batch mixers with anchor agitators at 20–40 rpm are typical for flake addition to hot oil at 70–85°C.
Sodium hydroxide flakes attack aluminum, magnesium, zinc, tin, brass, and galvanized surfaces with release of hydrogen. Storage bins and transfer lines should be 304 or 316L stainless steel, with elastomer seals of EPDM or PTFE; natural rubber gaskets degrade slowly in strong caustic. The material also reacts violently with strong acids, chlorinated solvents, nitro compounds, and ammonium salts, releasing heat and, in some cases, toxic gases. In flake feed systems, bridge formation is a known production bottleneck when warehouse relative humidity exceeds 60% or when bags are left open; rotary valves with 6–8 mm clearance and bin vibrators set at 30–40 Hz are used to maintain flow. Grounding of pneumatic conveying lines is required because triboelectric charging of anhydrous flakes can accumulate static charge. Dust exposure is controlled below the ACGIH TLV-C of 2 mg/m³ using P100 filters and local exhaust ventilation during bag opening.
The flake product differs from diaphragm-grade solid caustic primarily in chloride and chlorate profile, because membrane-cell electrolysis yields cell liquor with lower NaCl content and avoids mercury cell emissions. Compared with 50% lye, the flakes carry no water ballast; transport mass is reduced by approximately 50% for equivalent NaOH. The storage penalty is that dry caustic requires humidity-controlled warehousing, while 50% lye requires heated tanks in winter. Relative to pearl caustic soda, flakes may offer faster initial wetting in low-speed mixers due to larger planar surface area, but pearl products exhibit lower dusting in automated silo systems. Relative to potassium hydroxide flakes, NaOH provides 25.0 mol of hydroxide per kg versus 17.8 mol for KOH, but KOH is preferred when potassium soaps or liquid drilling fluids require specific cation chemistry.
| Product form | Typical NaOH/KOH content | Major impurity constraint | Handling and logistics condition |
|---|---|---|---|
| DCM Shriram caustic soda flakes | 99.0–99.5% w/w NaOH | NaCl ≤0.1% w/w | dry bags, hopper, dust extraction |
| Membrane-cell 50% lye | 50% w/w NaOH | NaCl typically ≤0.05% w/w | heated tanker and storage near 12°C freeze point |
| Diaphragm-grade solid caustic | 98.0–99.0% w/w NaOH | NaCl 0.2–0.5% w/w | dry handling, higher chloride carryover |
| Pearl caustic soda | 99.0–99.5% w/w NaOH | NaCl ≤0.1% w/w | silo, pneumatic conveying, lower dust |
| Potassium hydroxide flakes | 90.0–92.0% w/w KOH | K₂CO₃ ≤1.5% w/w | dry, hygroscopic, lower hydroxide per kg |
Organic synthesis operations use sodium hydroxide flakes as an anhydrous base in nucleophilic substitution and hydrolysis. For example, preparation of sodium phenoxide from phenol and caustic flakes is run at 60–80°C under nitrogen to avoid carbonate formation. The water content in flake caustic is lower than in 50% lye, which is important in reactions where water hydrolyzes intermediates or reduces yield. Batch records on production-scale reactors show that free water above 1% w/w can shift equilibrium in ester hydrolysis and reduce conversion to the sodium salt. The flakes are added through a solid-addition hopper over 30–45 minutes to control the exotherm; jacket cooling with chilled water at 5–10°C is maintained. Published data for this specific configuration is limited, so reaction calorimetry is recommended before scale-up.
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