# Sodium silicate: Production route

Furnace glass or pressure cooker: two ways to make it

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

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.

Two routes make sodium silicate. The furnace route melts sand and soda ash into glass, which is dissolved or sold solid; it suits high-ratio neutral grades and large volumes. The hydrothermal route dissolves sand directly in caustic soda in an autoclave at about 150-200 C; it uses less heat and suits alkaline, lower-ratio grades, but depends on caustic soda prices. Metasilicates and powdered grades are made by further processing. Choice depends on the relative cost of soda ash, caustic soda and fuel.

#### Routes compared

| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| **Furnace route (soda ash plus sand)** | majority of world capacity (indicative) | about 0.77 t sand, 0.40 t soda ash, about 4-6 GJ natural gas per t glass at ratio 3.3 (indicative) | furnaces of 50-200 kt/yr (indicative) | near 100% on silica | CO2 from soda ash about 0.17 t per t glass | soda ash about $120-160/t of glass at $300-400/t soda ash (indicative) |
| **Hydrothermal route (caustic soda plus sand)** | minority (indicative) | about 0.3 t NaOH (100%) and 0.7 t sand per t solids at lower ratios (indicative) | 10-100 kt/yr (indicative) | high; limited to ratio about 2.5-2.8 (indicative) | none material | caustic dominated; competitive when caustic is in surplus (indicative) |
| **Solid and specialty grades (powder, metasilicate, granular)** | small (indicative) | solution plus drying energy | small | high | none | drying adds cost (indicative) |

#### How each route works
**Furnace route (soda ash plus sand)**

Sand and soda ash are melted in a regenerative tank furnace similar to a glass furnace. The glass is tapped, cooled into lumps, then dissolved under steam pressure. Most large producers (PQ, Qemetica, BASF, Nippon Chemical) run furnaces.

Lowest cost for neutral grades; high-temperature fuel use and process CO2.
 Stoichiometry; indicative **Hydrothermal route (caustic soda plus sand)**

Ground sand is reacted with 30-50% caustic soda in a pressure vessel. No glass is made, so no high-temperature melting is needed. Common where caustic soda is cheap, for example next to chlor-alkali plants.

Low energy and no process CO2 on site; depends on caustic soda and its electricity footprint.
 Indicative **Solid and specialty grades (powder, metasilicate, granular)**

Solutions are spray-dried or the glass is ground to powder; sodium metasilicate is crystallised from low-ratio solutions for industrial cleaners and detergents.

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