Industrial HCl Production Process: Synthesis, By-products & Applications
5 Key Points to Remember:
- HCl has CAS number 7647-01-0, formula HCl, molecular weight 36.46 g/mol.
- Three main production methods: direct synthesis (H₂ + Cl₂), organic chlorination by-products, and recovery from other processes.
- 32% HCl is the most common commercial concentration, stable for storage and transportation.
- HCl gas is highly soluble in water; saturated solution reaches approximately 37–38% at room temperature.
- Contact Loc Thien for COA/MSDS and 32% HCl pricing based on quantity.
3 Main HCl Production Methods
In industry, hydrochloric acid is not “extracted” but rather produced or recovered from other chemical processes. The three main pathways differ significantly in purity, scale, and cost, so buyers need to understand the source to select the appropriate HCl grade for their application.
Direct Synthesis from H₂ and Cl₂
Chlorine gas and hydrogen gas are burned in a specialized combustion chamber (HCl synthesis unit) in a highly exothermic reaction:
H₂ + Cl₂ → 2HCl
The reaction produces HCl gas at high temperatures, which is then cooled and absorbed into water. Since both input materials are already pure, the resulting HCl gas is of very high purity, meeting stringent grades such as food or pharmaceutical grade. This method is often associated with chlor-alkali plants — where salt electrolysis produces both H₂ and Cl₂ — allowing for production volume control but with higher operating costs and safety requirements (explosive gas).
By-product from Organic Compound Chlorination
When chlorinating organic compounds (methane, ethylene, benzene…) to produce monomers and solvents, chlorine atoms replace hydrogen atoms and release HCl as a by-product. A typical example is the cracking of EDC (ethylene dichloride) into VCM (vinyl chloride monomer) for PVC production — the largest global source of HCl by-products today. This form of HCl has a very low cost advantage due to utilizing by-product streams but often contains organic impurities, requiring purification before use in high-purity applications.
Recovery from Other Production Processes
HCl is also recovered from various processes not included in the above two groups. A notable example is the Mannheim process — the reaction between NaCl and concentrated H₂SO₄ at high temperatures producing Na₂SO₄ and HCl gas — or the acid regeneration process recovering HCl from iron chloride solutions. These sources are typically small-scale, tied to specific plants, with purity and costs varying widely depending on the source.
Comparison Table of the 3 Methods
| Criteria | Direct Synthesis (H₂ + Cl₂) | Organic Chlorination By-product | Recovery from Other Processes |
|---|---|---|---|
| Production Scale | Controlled, on-demand | Very large, dependent on host plant | Small, tied to specific plant |
| Purity | Very high (usable for food/pharma grade) | Medium, may contain organic impurities | Varies widely by source |
| Relative Cost | High (requires pure H₂, Cl₂ + explosion safety) | Low (utilizes by-products) | Varies by recovery source |
| Typical Applications | High purity, pharma/food industry | Technical grade, general industry | Water treatment, on-site neutralization |
32% HCl Production Process — Step by Step
32% HCl is the most common commercial concentration in the Vietnamese market: concentrated enough to save transportation costs yet stable for long-term storage and easy to dilute on-site at factories. Whether from synthesis or by-product sources, the process of producing 32% HCl goes through the following core steps:
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HCl Gas Generation — from one of the three methods mentioned above (synthesis combustion chamber, chlorination by-product stream, or recovery source).
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Gas Purification and Cooling — hot HCl gas is cooled and impurities (acid droplets, organic impurities, dust) are removed before absorption, directly determining the final product’s purity.
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Absorption into Demineralized Water — HCl gas is directed into an absorption tower, dissolving into demineralized water to form acid. This is an exothermic reaction requiring strict temperature control.
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Adjustment to 32% Concentration — the gas/water ratio is adjusted to achieve an HCl content ≥ 32%. HCl gas is highly soluble, allowing for concentrated solutions up to 37–38% before dilution to the standard mark.
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Quality Testing and COA/MSDS Preparation — each batch is sampled for content and impurity analysis, with COA (certificate of analysis) and MSDS prepared batch-specific for traceability.
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Storage and Transportation — the acid is pumped into acid-resistant storage tanks (composite/liner) and delivered via specialized tank trucks to warehouses or directly to factory tanks.
The differences lie in steps 2 and 5: for by-product sources, purification must be more thorough to achieve technical grade; while for direct synthesis, the product is already near high purity from the start.
Industrial HCl Quality Standards
HCl buyers should carefully read batch-specific COAs rather than just looking at concentration numbers. Key indicators include actual HCl content, iron impurities (affecting color), sulfates, and free chlorine residues. Specific values vary by product grade (technical or high purity) and by production batch.
| Indicator | Typical Value | Notes |
|---|---|---|
| HCl Content | ≥ 32% | Per batch COA, not rounded |
| Density (20°C) | Corresponding to 32% concentration | See batch COA |
| Color | Colorless to light yellow | Light yellow often due to iron impurities |
| Iron Impurities (Fe) | Limit by grade | Per batch COA |
| Sulfates (SO₄) | Limit by grade | Per batch COA |
| Free Chlorine | At low levels | Per batch COA |
Safety note when reading specifications: HCl is a strong corrosive acid, fuming, with vapors irritating the respiratory tract. Any shipment must come with complete MSDS (hazard identification, first aid measures, spill handling) and COA stating actual analysis values for that specific batch — not general specifications printed on websites.
HCl Applications in Production Processes
32% HCl is an input chemical for many industrial processes, not limited to neutralization roles.
pH Adjustment and Water Treatment
In water and wastewater treatment plants, HCl is used to lower alkaline pH to operational levels, aiding coagulation and disinfection processes. It is also the standard chemical for cation exchange resin regeneration — displacing Ca²⁺, Mg²⁺ ions adsorbed on resin beads to restore resin activity.
Steel Pickling
HCl reacts with iron oxide layers on hot-rolled steel surfaces before coating or painting, providing a clean surface and faster pickling rates than sulfuric acid at room temperature. The iron chloride solution after pickling can be regenerated to recover HCl.
Water Treatment Chemical Production
HCl is a direct raw material for producing many water treatment chemicals. Notably, PAC (polyaluminium chloride) is prepared by reacting aluminum hydroxide with hydrochloric acid; FeCl₃ is also formed from the reaction of HCl with iron or iron oxide. Thus, HCl input quality directly affects PAC and FeCl₃ product stability.
Mining and Oil & Gas
In mining, HCl is used for ore leaching; in oil & gas, it is injected into wells to treat carbonate scale (well acidizing) to restore production flow rates.
Loc Thien — Supplying Batch-specific 32% HCl with Traceability
When purchasing HCl for factories, the deciding factor is not the lowest price but supply reliability and quality documentation. Loc Thien supplies 32% HCl with:
- Batch-specific COA/MSDS — each shipment comes with analysis certificates and safety documents for that specific batch, serving traceability and audit needs.
- Fleet of 20 specialized tank trucks — transporting acid according to standards, delivering directly to factory tanks in industrial zones, without intermediate bulk transfer.
- Warehouse system in key industrial zones — shortening delivery times and reducing supply chain disruption risks.
- Technical consultation before order confirmation — assisting in concentration selection, dilution calculations, and tank material compatibility checks.
Frequently Asked Questions
What’s the difference between 32% HCl and 37% HCl?
They differ in actual HCl content in the solution. 32% HCl is the common commercial concentration, stable for storage and transportation; 36–37% HCl is more concentrated, fumes more strongly, and requires stricter storage conditions. Choose concentration based on dilution needs and factory transportation costs.
What is the CAS number of HCl?
The CAS number of hydrochloric acid (HCl) is 7647-01-0. This is the standard identifier used in safety documentation, customs declarations, and MSDS.
How to distinguish directly synthesized HCl from by-product HCl?
Read batch COA and clarify the source with the supplier. Directly synthesized HCl typically has high purity, fewer organic impurities; by-product HCl may contain organic impurities and requires purification steps. Food/pharma grade applications require synthesis sources.
Does HCl corrode storage tanks?
Yes, HCl strongly corrodes common metals. Storage tanks must use acid-resistant materials like composite liners, HDPE/PP plastic, or rubber-lined steel. Do not use bare steel or aluminum tanks.
How should HCl be stored?
Store in a dry, ventilated area, away from alkalis, oxidizers, and metals. Tanks must be sealed to limit HCl fumes escaping, which can corrode surrounding equipment and affect respiratory health.
Does Loc Thien deliver 32% HCl to industrial zone factories?
Yes. Loc Thien delivers 32% HCl via specialized tank trucks to industrial zones, with batch-specific COA/MSDS. Contact for quantity-based pricing and specific delivery schedules.
Get 32% HCl Pricing
Need 32% HCl for your factory? Call 0979 891 929 — get a quote within 15 minutes, with batch-specific COA/MSDS and tank truck delivery schedules to your storage tanks.
LOC THIEN INVESTMENT DEVELOPMENT CO., LTD Hotline: 0979 891 929