There exist hundreds of soda lakes in Inner Mongolia Autonomous Region and other provinces of China

with their main constituents Na2CO3

NaHCO3

NaCl and Na2SO4. If the brine is processed by simple carbonization to precipitate NaHCO3 as an intermediate product and the mother liquor is discarded

the utilization of sodium will be rather low. An ammoniation-carbonation process was proposed[5]

in which a large proportion of NaCl and Na2SO4 will be converted to NaHCO3 also. In addition

NH4Cl and the unreacted Na2SO4 may be separated as final products from the NaHCO3 mother liquor. For the purpose of optimizing operation

the phase diagram of Na+

NH4+//HCO3-

Cl-

SO42-

H2O system at 35℃ was studied and some operating problems were discussed. The phase diagram showed that in order to raise the NaHCO3 yield

the[2NH3]/([Cl22-]+[SO42-])ratio in the ammoniated brine must be increased. Take the Dabusu Soda Lake brine as example

if the[2NH3]/([Cl22-] +[SO42-]) ratio is raised to 0.738

the sodium utilization UNa would be increased to 78.9%. But this is the limit value for [2NH3]/([Cl22-]+[SO42-]) ratio. If it is exceeded

NH4HCO3 would be precipitated together with NaHCO3.