Question

Differentiate between solvay and dual

process​

Answer 1

Answer:

It is used for the manufacturing of soda-ash and magnesium respectively for the one process named as 'partially-desalinated' water.

Answer 2

1. Advantage of Solvay process • Less electric power • Less corrosion problem • Use of low grade brine • Not a problem of disposal of co-product • Does not require ammonia plant

2. Disadvantage of Solvay process • Higher salt consumption • Waste disposal of CaCl2-brine stream • Higher investment in ammonia recovery units than crystallization unit of NH4Cl • Higher capacity plant set up require for economic break even operation

3. • This process combines Na2CO3 production with NH4Cl production. • The importance of the process in Japan is due to the high cost of imported rock salt and use of the ammonium chloride as a fertilizer. Solution A: 4.1 mol/L NH4Cl + 1.05 mol/L NaCl; =1.108 g/cm3; t =20 ◦C Solution B: 3.45 mol/L NH4Cl + 1.1 mol/L NaCl;  =1.110 g/cm3; t =5◦C Solution C: 1.86mol/L NH4Cl + 3.73 mol/L NaCl;  =1.187 g/cm3; t =10 ◦C Dual Process

4. Dual Process • NH3 is absorbed by the NaHCO3 mother liquor, and solid NaCl is added. • On cooling, NH4Cl separates, is recovered in centrifuges, and is then dried in rotary dryers with air at 150 ◦C. • The mother liquor is recycled to the carbonation towers where sodium NaHCO3 is precipitated.

5. Dual Process Difference compared to Solvay’s process • In the dual process, NH3 is not recovered; hence no NH3 recovery tower (distillation equipment)t is required. • Also, lime kilns are not required if other sources of CO2 are available. • As the mother liquor is recycled, special attention must be paid to the water balance of the system. • The amount of water introduced into the system (e.g., for washing NaHCO3 and NH4Cl) must be controlled continuously to maintain the correct quantity and composition.