# Hydrochloric acid: Production route

Three ways acid appears, mostly as someone else's leftovers

Source page: https://www.materialinsights.org/chemicals/hydrochloric_acid/routes/

Three ways acid appears, mostly as someone else's leftovers What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.

Hydrochloric acid comes from three main sources. Most is by-product from chlorination and phosgenation, which makes HCl in proportion to chlorine consumed. Chlor-alkali producers also burn chlorine with their own hydrogen to make synthetic acid of high purity. A smaller share comes from the Mannheim process (salt plus sulphuric acid, making potassium or sodium sulphate). Much by-product HCl is recycled to chlorine or used in oxychlorination.

#### Routes compared

| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| **By-product from isocyanates, chlorinated organics and fluorocarbons** | majority of HCl (indicative) | not applicable (by-product) | 100-500 kt/yr at large MDI sites | not applicable | not applicable | near zero or negative: producers pay to dispose of surplus |
| **Direct synthesis from chlorine and hydrogen** | a large share in India and China (indicative) | about 0.97 t Cl2 and 0.028 t H2 per t of 100% HCl | 50-200 TPD units at chlor-alkali plants | near 100% | heat | opportunity cost of chlorine; often near zero when chlorine is negative |
| **Mannheim process (salt plus sulphuric acid)** | small | about 2.0 t KCl (or 1.6 t NaCl) and 1.34 t H2SO4 per t HCl (stoichiometric) | small | high | potassium or sodium sulphate (the main product) | set by sulphate market |

#### How each route works
**By-product from isocyanates, chlorinated organics and fluorocarbons**

Phosgenation for MDI, TDI and polycarbonate, chlorination of methane and aromatics, and HCFC/fluoropolymer production each release HCl gas, which is purified and absorbed or recycled.

cheap; purity varies (organics, fluorides)
 indicative **Direct synthesis from chlorine and hydrogen**

Chlorine is burned with excess hydrogen in a graphite or silica burner and absorbed in water. This turns surplus chlorine into a saleable product and gives high-purity acid for food, pharma and electronics.

pure product; ties up chlorine
 stoichiometry; indicative **Mannheim process (salt plus sulphuric acid)**

Potassium or sodium chloride reacts with sulphuric acid in a furnace, giving sulphate of potash or sodium sulphate and HCl.

HCl is a co-product of SOP fertiliser
 stoichiometry Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.

## Other sections

- [Summary](https://www.materialinsights.org/chemicals/hydrochloric_acid/index.md)
- [Overview](https://www.materialinsights.org/chemicals/hydrochloric_acid/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/hydrochloric_acid/correlation/index.md)
- [Production](https://www.materialinsights.org/chemicals/hydrochloric_acid/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/hydrochloric_acid/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/hydrochloric_acid/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/hydrochloric_acid/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/hydrochloric_acid/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/hydrochloric_acid/regulation/index.md)
- [Characteristics](https://www.materialinsights.org/chemicals/hydrochloric_acid/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/hydrochloric_acid/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/hydrochloric_acid/links/index.md)