Xinjiang Zhongtai Chemical Caustic Soda Pearls 99%

Xinjiang Zhongtai Chemical Caustic Soda Pearls 99% is a solid sodium hydroxide grade with NaOH mass fraction not less than 99.0%. Because downstream alkali dosing is specified on a 100% NaOH basis, the pearl product is corrected by a factor of 1.01 when dry-basis additions are converted to as-received weight. The application scenarios that follow are restricted to established industrial caustic soda consumption points: Bayer alumina extraction, kraft white liquor fortification, cotton mercerization, soap saponification, finished water pH control, refinery caustic treating, and sodium hypochlorite synthesis.

What governs caustic consumption in Bayer alumina circuits?

In Bayer alumina refining, caustic soda pearls are dissolved in barren process liquor to maintain a digestible Na₂O concentration in the range 180–240 g/L, expressed as Na₂O. Fresh 99% pearl dosing is calculated against liquor volume: a 1 g/L Na₂O increase requires 1.0 kg NaOH per cubic meter, or 1.01 kg of 99% pearls per cubic meter. The make-up demand reported in public mass balance studies for refineries processing diasporic and boehmitic bauxites is 45–75 kg NaOH per metric ton of alumina, with the upper end associated with reactive silica in the bauxite feed. The governing compliance instruments are GB/T 209-2018, solid sodium hydroxide IS Type I, and for EU supply chains Regulation (EC) No 1907/2006 under REACH. Downstream production uses indirect steam-heated autoclaves operating at 200–260 °C for boehmitic and diasporic ores, followed by a flash-cooling train, red mud thickening and security filtration, precipitation seed recycle, rotary vacuum filtration, and fluid-bed calcination at 950–1100 °C. Terminal products are smelter-grade alumina with ≥98.5% Al₂O₃ and calcined hydrate fractions used for refractories and speciality aluminas. The principal process conflict is reactive silica attack on caustic liquor: desilication product formation consumes sodium hydroxide and increases energy input in the digestion circuit, which is why refineries blend bauxite feed to limit total silica loading below the point at which digestion viscosity and settled mud rheology become unstable.

In kraft pulp mills, caustic soda pearls are charged into white liquor storage to correct active alkali deficits when the recausticizing loop cannot deliver the target effective alkali to the continuous digester. The governing analytical standard is TAPPI/ANSI T 624 cm-00 for white and green liquor composition, while the production unit is operated within 40 CFR Part 430 Subpart B for bleached papergrade kraft and soda effluent discharge. The caustic addition ratio is typically expressed as 1.01 kg of 99% pearls per cubic meter per 1 g/L effective alkali increase, and the digester cooking target is 16–20% effective alkali as NaOH on oven-dry wood with sulfidity 25–35%. In a 1,000 m³ white liquor storage tank, raising effective alkali by 3 g/L requires 3.03 t of 99% caustic pearls. The downstream process includes smelt dissolving, slaker and causticizer trains, clarification, and continuous digesters with multi-stage circulation; the pearls are dissolved in a dedicated mixing tank with cooling before injection into the white liquor header. Terminal products include unbleached kraft linerboard, bleached softwood kraft pulp, and dissolving pulp grades where alkali profile influences final viscosity and cellulose reactivity in viscose processing.

Mercerization Alkali Concentration and Tension Control

Cotton mercerization uses caustic soda pearls dissolved to 200–260 g/L NaOH, corresponding to approximately 20–24°Bé, with bath temperature held at 15–25 °C. The compliance reference for the process is AATCC TM89-2019, Mercerization in Cotton, and the finished textile chemical inputs are screened under OEKO-TEX Standard 100 for restricted substances. A 5,000 L pad bath at 220 g/L NaOH requires 1,100 kg NaOH, equivalent to 1,111 kg of 99% pearls; wetting agent is dosed at 0.1–0.3% on bath weight to improve alkali penetration into the cotton fiber. The downstream production process treats fabric under controlled warp and weft tension on a chain or pad-batch mercerizing range; after caustic saturation, the web passes through hot water recovery stages and dilute acetic acid neutralization before drying on a tenter frame. The tension window is critical because slack mercerization increases absorbency but does not produce the same luster as tension mercerization, and caustic concentration below 18°Bé reduces fiber swelling while concentration above 26°Bé can increase cotton degradation if temperature and dwell time are not tightly bounded. Terminal finished products include high-lustre cotton shirting, denim, mercerized sewing thread, tubular knit goods, and sock yarns where differential dye uptake is deliberately engineered through alkali exposure.

Soap kettles receiving refined tallow and coconut oil blends are charged with caustic soda solution prepared from 99% pearls, and the alkali charge is set by the saponification value of the oil blend. For an oil blend with SV 195 mg KOH/g, the stoichiometric NaOH requirement is 0.139 g NaOH per gram of oil, or 13.9% on oil charge; a 5,000 kg oil batch therefore requires 695 kg NaOH base, equivalent to 702 kg of 99% pearls. The governing compliance standard for excess alkali in the finished soap is ISO 684:1974, Determination of total free alkali, and EU detergents are labelled in accordance with Regulation (EC) No 648/2004, Annex VII. The process is run in jacketed stainless-steel kettles at 80–100 °C with recirculation and controlled salt splitting; after saponification, the neat soap is dried under vacuum, filtered through a plodder, and extruded into noodles or bars. Terminal products include laundry bar soap, toilet soap, soap noodles sold to downstream specialty formulators, and oleochemical intermediates where the residual free NaOH is limited to 0.05–0.15% in the neat soap.

Corrosion control limits are set before chlorine residual is applied

Municipal water plants use caustic soda pearls to raise pH and stabilize finished water against cement-mortar lining corrosion in distribution piping. The governing supply standard is ANSI/AWWA B501-19 for sodium hydroxide, and the treatment chemical is certified to NSF/ANSI/CAN 60 for potable water use. The addition ratio for low-alkalinity surface water is 5–25 mg/L NaOH, metered as a 1–2 wt% solution from a day tank equipped with a static mixer and downstream pH analyzer. A 100 ML/day finished water flow at 10 mg/L NaOH consumes 1,000 kg NaOH per day, equivalent to 1,010 kg of 99% pearls. The process target is finished water pH 7.0–7.8 and Langelier saturation index +0.2 to +0.5; overdosing above pH 8.5 is avoided because it can destabilize aluminium-based coagulant residuals and raise trihalomethane formation potential in chlorination. Terminal outputs include municipal potable water, industrial boiler feedwater after ion exchange, and reverse osmosis permeate stabilization prior to distribution, where the residual alkali prevents aggressive carbon dioxide attack on downstream steel and concrete infrastructure.

When naphtha and LPG streams require non-regenerative caustic extraction

Refinery caustic treating uses 99% pearls dissolved to 5–15 wt% NaOH for non-regenerative extraction of hydrogen sulfide, mercaptans, and naphthenic acids from naphtha, LPG, and kerosene fractions. The process is governed for damage mechanisms by API RP 571, specifically the section addressing caustic stress corrosion cracking, and the spent caustic is handled under facility waste permits with oxidation or wet air oxidation before discharge. The addition ratio in the treatment loop is normally 0.5–2.0 vol% caustic solution per liquid hydrocarbon feed, with spent caustic discharged once free NaOH declines to 2–8 wt%. Downstream equipment includes fiber-film contactors or caustic wash towers with mix valves, settling drums, and coalescers; mixing intensity is set to avoid stable emulsions, and the treating temperature is maintained below 50–60 °C for light-end streams to reduce sulfide re-entry. Finished products are LPG meeting copper-strip corrosion 1a per ASTM D130, gasoline blendstock with reduced mercaptan sulfur, and jet fuel components with lower naphthenic acid number. Caustic strength above 15 wt% is generally avoided because naphthenic acid sodium soap emulsification becomes severe and rag layer formation in the settler increases carryover risk.

Chlorine absorption into a 10–15 wt% NaOH solution is conducted in packed towers or externally cooled batch reactors to produce sodium hypochlorite for water disinfection and surface sanitation. The caustic pearls are dissolved to 120–180 g/L NaOH, and chlorine is metered at a stoichiometric ratio of 0.886 kg Cl₂ per kilogram of 100% NaOH; the reaction is held at ≤35 °C and final pH above 12.0 to limit chlorate formation. The governing product specifications are ANSI/AWWA B300-18 for hypochlorite and ASTM D2022-89 for sampling and chemical analysis of chlorine-containing bleaches. A 10,000 L batch at 150 g/L NaOH consumes 1,500 kg NaOH base, equivalent to 1,515 kg of 99% pearls, and yields sodium hypochlorite with 10–12% available chlorine. Terminal products include commercial hypochlorite bleach, swimming pool sanitizer, and industrial biocide for cooling water systems. The main process constraint is temperature rise from exothermic chlorine absorption; if the reactor exceeds 40 °C, accelerated decomposition forms chlorate and oxygen, reducing available chlorine and creating a gas-release hazard.