Soda ash (sodium carbonate) is the alkali behind glass, soap, paper and water softening, and there are three ways to get it: mine natural trona and heat it, extract it from plant ash or make it by the Leblanc process, or run the Solvay process from salt, limestone and ammonia. Check for natural trona or soda deposits first, because a deposit needs only heating. The Solvay route works only if the ammonia is recovered and recycled, and it produces about 1.05 tonnes of calcium chloride waste per tonne of soda ash.
Part of Industrial Chemistry
The sources and routes to sodium carbonate, and how to choose among them for a rebuilding community.
Choose The Route By What The Ground Offers
The carrier says soda ash is essential for glass, soap, paper, water softening and chemical processing, and gives a decision rule: before building a Solvay plant, check for natural soda ash deposits. Trona (natural sodium sesquicarbonate) occurs in evaporite deposits and arid lake beds; where you can mine it, you can produce soda ash by simple heating, with no Solvay process.
- Natural deposit (trona). Heat the mined mineral. No plant needed.
- Plant ash, seaweed ash and Leblanc. The route the corpus covers in Soda Ash Production, including burned seaweed or plant ash and the Leblanc process.
- Solvay (ammonia-soda). Salt, limestone and ammonia, with ammonia and carbon dioxide recycled. Chemistry in Solvay Chemistry, hardware in Equipment Needed.
What You Need
- A deposit survey, salt sources (Salt Production and Sourcing), and limestone (Limestone Sourcing).
- Fuel for kilns (Lime Kiln).
- For Solvay: an ammonia supply (Simplified Ammonia) and the means to recover it.
- A test for the product: soda ash dissolved in water and acidified fizzes vigorously (the carrier’s quick test).
Method: Deciding
Step 1: Look for trona or natural soda in dry lake beds and evaporite deposits.
Step 2: If none, consider plant ash and Leblanc at small scale from the Soda Ash Production page.
Step 3: Consider Solvay only for sustained demand and only after ammonia recovery has been designed.
Step 4: Test the product with acid fizz and a hydrometer if you sell or store it in solution.
Worked Example: Raw Material And Waste Per Tonne
From the overall reaction 2NaCl + CaCO3 → Na2CO3 + CaCl2 (masses: 117 + 100 → 106 + 111).
- Salt per tonne of soda ash at 100% yield: 117 ÷ 106 = 1.10 tonnes.
- Limestone: 100 ÷ 106 = 0.94 tonnes.
- Waste calcium chloride: 111 ÷ 106 = 1.05 tonnes.
Real plants use more of each because yield is below 100% (see Yield and Efficiency). The waste is as large as the product, which is why the carrier lists calcium chloride in its waste table, and why Waste Treatment has to plan for it.
Common Mistakes
- Building a Solvay plant when trona exists.
- Neglecting ammonia recovery. The carrier says ammonia costs dwarf the soda ash’s value without it.
- Ignoring the waste volume.
- Using soda ash on skin or eyes. It is alkaline and burns.
Safety
Soda ash is a caustic powder, and the Solvay route carries ammonia and hot kilns
Soda ash dust and strong solutions burn skin and eyes. The Solvay route handles ammonia (toxic) and a lime kiln above 900 °C, and releases carbon dioxide, which pools in low places. See Toxic Gases and Protective Gear.
What’s Next
- Learn next: Solvay Chemistry — the reactions in order
- Combine with: Caustic Soda — soda ash is a precursor to lye