| HS Code | 614005 |
| Product Name | Junzheng Group Caustic Soda Flakes |
| Chemical Name | Sodium Hydroxide |
| Chemical Formula | NaOH |
| Cas Number | 1310-73-2 |
| Appearance | White flaky solid |
| Purity | ≥99% |
| Melting Point | 318°C |
| Boiling Point | 1388°C |
| Solubility | Soluble in water, releasing heat; soluble in ethanol and glycerol |
| Ph | 13-14 (1% aqueous solution) |
| Grade | Industrial Grade |
| Hygroscopicity | Highly hygroscopic |
As an accredited Junzheng Group Caustic Soda Flakes factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 25 kg PP woven bags with PE inner liner, palletized and shrink-wrapped for safe transport and storage. |
| Container Loading (20′ FCL) | 20′ FCL container loading of Junzheng Group caustic soda flakes: palletized, moisture-protected, securely stowed, ventilated for safe transport. |
| Shipping | Junzheng Group Caustic Soda Flakes ship in sealed, moisture-proof woven bags or drums, packed in ventilated containers. Keep dry and away from acids, moisture, and incompatible materials. Transport by truck or sea with proper hazard labeling, ensuring safe handling and compliance with chemical shipping regulations. |
| Storage | Store Junzheng Group Caustic Soda Flakes in a clean, dry, well-ventilated warehouse, away from moisture and water sources. Keep containers tightly sealed, preferably original polyethylene-lined bags, on raised pallets. Avoid storing near acids, organic peroxides, or food products. Protect from physical damage and maintain temperatures below 35°C to prevent caking and degradation. |
| Shelf Life | Shelf life is typically 12 months when stored sealed, dry, and away from moisture. |
In alumina refineries processing diasporic bauxite, Junzheng caustic soda flakes with 98.5 wt% minimum NaOH content and GB/T 209-2018 solid caustic soda specification are dissolved into spent liquor condensate to restore free caustic concentration after digestion, liquor losses, and residue washing. The addition ratio for diasporic bauxite is maintained at 220–260 g/L Na₂O in digestion liquor, with lime charge at 3–5 wt% CaO on dry bauxite and digestion temperature 250–270 °C. For gibbsitic bauxite the caustic operating window is lower, typically 140–180 g/L Na₂O at 140–160 °C. Flake is metered through a closed screw feeder into an agitated dissolving tank with 60–80 °C condensate, and the resulting 45–50 wt% NaOH solution is dosed into the spent liquor header ahead of wet grinding. At production scale, the dominant failure modes are feeder bridging caused by moisture ingress above 60% relative humidity and calcium silicate/carbonate scale deposition on the shell-and-tube heat exchanger train. Specific caustic consumption per tonne of smelter-grade alumina ranges from 60–80 kg NaOH for gibbsitic operations to 70–120 kg NaOH for diasporic operations, depending on reactive silica content and mud washing efficiency. Downstream production proceeds through multi-chamber autoclaves or pipe digesters, atmospheric flash cooling, red mud separation in high-rate thickeners, security filtration of pregnant liquor, seeded precipitation, and calcination at 1000–1100 °C. Compliance is anchored to ISO 14001:2015 for environmental management and the IFC EHS Guidelines for Aluminum Manufacturing, 2009, Section 1.1, which requires bauxite residue slurry pH to be controlled to 9.5–10.5 before disposal. Terminal products include smelter-grade alumina with ≥98.5 wt% Al₂O₃ and bulk density 0.95–1.05 g/cm³, chemical-grade alumina for catalyst and ceramic applications, and washed residue filter cake.
| Parameter | Gibbsitic Bauxite Operating Envelope | Diasporic Bauxite Operating Envelope |
|---|---|---|
| Caustic concentration in digestion liquor as Na₂O | 140–180 g/L | 220–260 g/L |
| Digestion temperature | 140–160 °C | 250–270 °C |
| Specific caustic consumption per tonne alumina | 60–80 kg NaOH | 70–120 kg NaOH |
| Residue slurry pH target before disposal | 9.5–10.5 | 9.5–10.5 |
At the white liquor dissolving station of a kraft pulp mill, Junzheng caustic soda flakes are fed through a closed screw conveyor into a 10–20 m³ agitated tank containing 60–80 °C condensate or weak wash liquor, and the resulting solution is blended with sodium sulfide to maintain target effective alkali and sulfidity. The addition ratio for hardwood pulping is 14–18 wt% effective alkali as NaOH on oven-dry wood, with sulfidity at 25–35%; softwood lines typically operate at 18–22 wt% effective alkali. White liquor alkalinity is verified according to TAPPI T 624 white and green liquor analysis, while finished pulp pH is checked by ISO 6588-1:2020. Downstream production involves pre-steaming of chips, impregnation, batch or continuous digesters, blow-line dilution, brown stock washing in a countercurrent vacuum drum washer, oxygen delignification, and bleaching in chlorine dioxide stages. Causticizing efficiency is maintained at 82–88%, and lime mud from the recausticizing plant is returned to the lime kiln. A critical operational boundary is that the flake dissolving tank must not be charged into hot black liquor without induced draft because hydrogen sulfide release increases sharply above 85 °C. Terminal products include bleached and unbleached kraft pulp, linerboard, sack paper, and hardwood market pulp. Published plant-specific dissolution rate data for Junzheng flakes in kraft dissolving tanks are limited, but the above operating envelope is applied across conventional hardwood and softwood mill configurations.
Cotton mercerizing uses a caustic soda bath prepared from Junzheng flakes at 20–24 wt% NaOH, controlled at 15–20 °C, with fabric residence time 45–60 s on a chain mercerizer. The addition ratio is set by bath refractometer or density check, corresponding to 1.22–1.26 g/cm³ solution density. Weak wash liquor from the first countercurrent wash contains 5–8 wt% NaOH and is concentrated in a triple-effect evaporator to 45–50 wt% before reconstitution to the mercerizing bath. The process runs fabric through a pneumatic padder into the caustic chain, then through a tenter frame with stenter clips under controlled tension to maintain dimensional stability. The tension during caustic impregnation is critical: low tension results in fabric shrinkage and lower luster, while excessive tension increases thread breakage in fine-count poplin. Temperature rise above 22 °C reduces mercerization efficiency because sodium-cellulose swelling decreases, so chilled water jackets and plate heat exchangers are required on the bath circulation loop. Incompatibility with aluminum fittings is absolute; the bath piping and pump casing are specified in 316L stainless steel. Finished textile compliance is verified by AATCC Test Method 81-2016 for water-extracted pH, which must be 5.5–7.5, and residual sodium is checked before dyeing to avoid uneven dye uptake. The operation is also governed by ZDHC MRSL 3.1 for discharge quality, while caustic recovery reduces effluent sodium load. Terminal products include mercerized cotton poplin, high-lye uptake apparel fabric, high-tenacity sewing thread, and mercerized cotton knit for premium T-shirts.
Neutralisation of acid mine drainage containing 600–1500 mg/L acidity as CaCO₃ requires Junzheng caustic soda flakes diluted to 20 wt% NaOH and dosed at 480–1200 mg/L dry NaOH equivalent, calculated as 0.80 mg NaOH per 1.00 mg acidity as CaCO₃. The production process routes raw AMD into a 5–10 m³ pH adjustment tank equipped with a pH 9.0 setpoint controller, followed by an oxidation cascade with coarse-bubble air sparging to convert ferrous iron to ferric hydroxide at pH 8.5–9.2. In-line static mixers are installed downstream of the caustic dosing point to prevent local boiling when acidic streams below pH 2 contact concentrated alkali. The flocculated solids settle in a high-rate thickener, and settled metal hydroxide sludge is dewatered in a plate-and-frame filter press to 35–45 wt% solids. Discharge compliance is anchored to ISO 9963-1:1994 for alkalinity measurement and to the receiving-water pH limit of 6–9 under US EPA NPDES permits. Operational boundaries include the incompatibility of NaOH with zinc, aluminum, and tin dosing hardware; only 316L stainless steel or PP/PTFE wetted parts are used. Terminal products are neutralized clarified water discharging under permit pH, and dewatered metal hydroxide filter cake suitable for controlled landfill or, in some cases, resource recovery.
Saponification of palm stearin in a 10,000 L jacketed crutcher proceeds with Junzheng caustic soda flakes dissolved to 30°Bé solution, approximately 24 wt% NaOH. The addition ratio is calculated from the saponification value of 190–205 mg KOH/g, yielding 0.135–0.146 kg NaOH per kg oil on dry basis, plus 0.5–1.0% excess free caustic for phase separation. Oil is pre-melted at 70–75 °C, and the caustic solution is added under high-shear mixing with a counter-rotating anchor agitator and scraped-wall blades. The exothermic reaction raises the mass to 105–110 °C, after which 1–2 wt% sodium chloride is introduced to salt out the neat soap and separate the glycerine-rich spent lye. A critical production failure is local caustic excess at the addition point, causing yellowing and poor bar surface; this is controlled by metered injection through a ring distributor rather than direct top dumping. Free caustic alkali in the finished soap is measured according to ISO 456:1973, and total alkali plus fatty matter is determined by ISO 685:1975. The operation must reject flakes with sodium carbonate content above 0.8 wt% because carbonate salts reduce soap clarity in transparent bar formulations. Terminal products include laundry bar soap with 63–78 wt% total fatty matter, toilet soap noodles for downstream plodding, and neat soap chips for industrial cleaning compounds.
Lye peeling systems for tomato and potato lines operate with a 316L stainless steel dissolution tank feeding a tubular lye heater that holds the peeling solution at 85–93 °C. For tomatoes the addition ratio is 8–12 wt% NaOH with contact time 15–30 s; for potatoes the bath is adjusted to 10–18 wt% NaOH at 75–90 °C for 2–4 min depending on tuber size and skin thickness. Junzheng caustic soda flakes used in this application must meet the food chemical codex monograph for sodium hydroxide with assay 95–100.5% NaOH, lead content ≤2 mg/kg, and conform to FDA 21 CFR 184.1763 generally recognized as safe status. The downstream process passes product through a drum lye peeler fitted with rubber disc scrubbers, followed by a countercurrent rinse and a 0.5–1.0 wt% citric acid neutralization bath. The acid rinse is mandatory to prevent residual surface pH above 7.5, which accelerates enzymatic browning in peeled potatoes and reduces tomato texture. Incompatibility with chlorinated cleaning solutions must be controlled because hypochlorite disinfectant entering the lye bath releases chlorine gas under alkaline conditions. Terminal products include canned diced tomatoes, aseptic tomato paste, peeled whole tomatoes in juice, and pre-peeled vacuum-packed potatoes for foodservice and retail chill chains.
Chlorine absorption into 18–20 wt% caustic soda solution is exothermic and requires an FRP-lined batch reactor with a Hastelloy C-276 chlorine sparger and external cooling to keep the reaction temperature at 25–30 °C. The addition ratio for sodium hypochlorite production using Junzheng caustic soda flakes is an initial 18–20 wt% NaOH solution; chlorination continues until available chlorine reaches 150–180 g/L, with final excess sodium hydroxide remaining at 3–5 g/L. Temperature above 40 °C promotes sodium chlorate formation and shortens shelf life, so cooling water to the reactor jacket is interlocked with chlorine flow. A packed scrubber charged with 5 wt% caustic solution guards the vent line. Finished hypochlorite must comply with ANSI/AWWA B300-18 Hypochlorites and, for drinking water treatment use, NSF/ANSI/CAN 60 certification. Operational boundaries include the incompatibility of sodium hypochlorite with acid dosing, which releases chlorine gas, and the requirement to use low-iron flakes because iron above 5 mg/kg accelerates decomposition and oxygen gas formation in storage containers. Terminal products include 12.5 wt% trade sodium hypochlorite solution, industrial bleach, and chlorinated disinfectant for water disinfection and surface sanitation.
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Junzheng Group Caustic Soda Flakes is an anhydrous solid sodium hydroxide product supplied as white deliquescent flakes with a nominal NaOH mass fraction of 99.0%. The material is produced through membrane-cell electrolysis of sodium chloride brine at an integrated chlor-alkali site in Inner Mongolia. It carries CAS registry number 1310-73-2, UN 1823, hazard class 8, packing group II, and a formula weight of 39.997 g/mol. The commercial grade is designated under GB/T 209-2018 as solid sodium hydroxide, IS-IT type, and is commonly traded as 99% caustic soda flakes. Lot release testing typically follows the GB/T 4348 chemical analysis series for sodium hydroxide, sodium carbonate, sodium chloride, and iron content. In comparison with diaphragm-cell or mercury-cell material, the membrane-cell route provides a different carryover profile for sodium chloride, chlorate, and trace metal species, which is of operational significance in chloride-sensitive processes.
Within storage and handling operations, the flake form imposes two constraints: moisture exclusion and carbonate pickup control. Each lot is controlled against a certificate of analysis reporting sodium hydroxide content, sodium carbonate, sodium chloride, and iron as Fe₂O₃. The representative membrane-cell flake specification is NaOH ≥ 99.0%, Na₂CO₃ ≤ 0.5%, NaCl ≤ 0.03%, Fe₂O₃ ≤ 0.0005%. Packaging is normally 25 kg three-layer laminated polypropylene sacks with an inner polyethylene liner, or 1,000 kg flexible intermediate bulk containers for bulk handling. Unopened sacks should be stored on pallets in a covered area with relative humidity maintained below 60% where feasible, because the flakes rapidly absorb atmospheric moisture and carbon dioxide, producing surface caking and an increase in sodium carbonate assay. For dissolution rate as a function of flake size distribution and agitator power, published data for this specific configuration is limited; site-specific addition trials are required to establish batch dissolution time and residual solids screening.
The defining difference of Junzheng Group Caustic Soda Flakes from older diaphragm-cell grades is the absence of direct contact between the chlorine gas stream and the sodium hydroxide stream during electrolysis. In diaphragm cells, chloride ion migration and cell liquor separation can leave residual sodium chloride in the final dried product, whereas membrane cells use a perfluorinated cation-exchange membrane that suppresses chloride transport. Consequently, membrane-cell flakes are specified with NaCl ≤ 0.03%, while diaphragm-cell material commonly carries higher sodium chloride. The membrane-cell route also lowers chlorate formation and reduces iron uptake during evaporation and flaking, provided that downstream equipment is constructed of corrosion-resistant materials. Mercury-cell caustic soda, though high in purity, requires separate mercury-trace verification and is not part of this product route. For end uses such as chlor-alkali balance calculations, ion-exchange resin regeneration, or food-contact processing, the reduced chloride and chlorate carryover can alter stoichiometric additions and minimize undesired chlorinated byproduct formation.
The following table summarizes the commercial specification matrix and recognized test designations for the anhydrous flake product.
| Parameter | Limit | Unit | Standard testing method |
|---|---|---|---|
| Sodium hydroxide as NaOH | ≥ 99.0 | % m/m | GB/T 4348.1 |
| Sodium carbonate as Na₂CO₃ | ≤ 0.5 | % m/m | GB/T 4348.1 |
| Sodium chloride as NaCl | ≤ 0.03 | % m/m | GB/T 4348.2 |
| Iron as Fe₂O₃ | ≤ 0.0005 | % m/m | GB/T 4348.3 |
The matrix is a compliance checklist for commercial release; it is not an exhaustive certificate. Trace mercury, nickel, and copper should be confirmed on the supplier certificate for regulated applications. As a dry flake, the product differs from 50% liquid caustic soda and from prilled or granular anhydrous forms in shipping moisture, dusting, and dissolution behavior. The flake form generally reduces airborne dust relative to prill during manual charging, while the anhydrous 99% assay reduces freight mass versus liquid grades. However, dissolution rate is governed by surface area and solution agitation; an unheated, low-shear tank will require substantially longer wetting and residual flake dissolution than a recirculating eductor system.
In Bayer-process alumina refining, caustic soda flakes serve as makeup soda for digestion of bauxite and for red mud washing circuits. Digestion conditions depend on mineralogy: gibbsitic bauxites are typically processed at 140–150 °C and 0.3–0.5 MPa, boehmitic feed at 200–240 °C and 1.5–3.0 MPa, and diasporic bauxites at 240–270 °C. The 99% dry flake is dissolved in spent liquor or weak wash to maintain the molar Na₂O-to-Al₂O₃ balance and restore alkali losses to red mud, desilication products, and soda-alumina species. Compared with 50% liquid caustic soda, the dry form reduces freight mass and dilution water but requires a dedicated recirculation skid with cooling because heat of dissolution can raise localized liquor temperature above 80 °C. Tanks and transfer lines in hot wet caustic service are commonly specified in 316L stainless steel or polypropylene to avoid carbon steel stress-corrosion cracking. Red mud washing efficiency and rake thickener operation are affected by residual chloride entering with caustic makeup; low chloride membrane-cell flake reduces chloride accumulation in the aluminate liquor loop.
Kraft pulping converts the solid flakes to white liquor by dissolving with lime and sodium sulfide or sodium sulfate makeups. White liquor effective alkali charge for softwood kraft is often 14–18% Na₂O on oven-dry wood, with sulfidity between 25% and 35%. The membrane-cell grade is preferred in mills where chloride accumulation in chemical recovery loops must be minimized; chloride entering with caustic makeup can accelerate deposit formation and corrosion in recovery boilers. In textile mercerization, the flakes are dissolved to form caustic baths at 18–25% NaOH by weight, often maintained below 20 °C to control swelling and luster development. Iron content is a critical parameter in this application because precipitated iron stains cellulose fabric; the Fe₂O₃ limit of 0.0005% supports low discoloration risk. Bath strength is checked by titration and density, and additions are controlled by conductivity-based dosing. In oil refinery caustic treating, sodium hydroxide solution at 5–15% is used to extract hydrogen sulfide and mercaptans from LPG and cracked naphtha. Low chloride and low carbonate in the makeup are advantageous in closed spent-caustic systems where scale and sodium chloride precipitation can restrict outlet flow.
Saponification of triglycerides with sodium hydroxide follows a stoichiometric reaction with a controlled excess. In batch soap manufacturing, the flake is dissolved to a 20–25% sodium hydroxide solution and metered into the fat blend with a slight excess of 0.5–1.5% alkali to ensure complete hydrolysis. The low carbonate specification helps avoid pseudobasic soap defects and reduces variability in the final pH curve. For neutralization of acidic wastewater, 99% flake is diluted to 10–20% solution before metering into a mixed neutralization tank. The solution should be prepared with water conforming to ASTM D1193 Type II or better to avoid hardness-scale precipitation in dosing lines. Caustic soda is incompatible with aluminum, zinc, tin, brass, and concentrated acids; it reacts violently with strong acids and generates heat when mixed with water. It should not be combined with ammonium salts or chlorinated solvents in closed systems because toxic or flammable gases may be released. For cleaning and sanitizing operations in food-processing equipment, only a lot specifically certified to food-grade criteria should be used; the industrial membrane-cell grade described here is not automatically cleared under FDA 21 CFR 173.310 or similar food-contact regulations.
Manual addition of solid flakes directly into process vessels is generally avoided when solution strength exceeds 10% because localized exotherms may exceed 100 °C. Instead, use a high-shear eductor or recirculating flake dissolution system with batch temperature control. In continuous dosing, pump seals and diaphragms should be selected from EPDM or PTFE; natural rubber and nylon are not recommended for continuous wet caustic service. Carbon steel storage tanks are acceptable for dry solid handling but not for hot wet caustic solutions; 316L stainless steel is preferred for tanks and piping. When dilution water is below 10 °C, dissolution is slower and may require longer recirculation times. All handling must use alkali-resistant gloves, face shields, and emergency eyewash stations meeting ANSI Z358.1.
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