Typically, the industrial evaporation process is operated at a high evaporation rate in nonequilibrium stable or dynamic state within the temperature range of 323 to 393 K. During this process, both the solubility and the crystallization of salt are affected by organic impurities in the system. In this work, glutaraldehyde, one of the main organic compound in wastewater produced from coal-chemical, was selected to be representative organic impurity and chemical oxygen demand (COD) to simulate the high-salt coal-chemical wastewater. The stable and metastable solidliquid equilibria of (Na2SO4 - NaCl - H2O) system containing organic impurity at 333.15K was studied. The results showed that the solubility and supersolubility of Na2SO4 increased with the increase of COD. However, the solubility and supersolubility of NaCl had begun to increase when the COD value around 450 mg L1. When the COD value reached to 3290 mg L-1 (the content of actual wastewater), the solubility and supersolubility of both Na2SO4 and NaCl exhibited a dramatic change. Meanwhile, the metastable zone widened and the salt-forming zone moved remarkably. These results suggest that when the removal of organic impurities in the system cannot be achieved cost-effectively, the effect of organic impurities on NaCl salts in the system can be significantly decreased by reducing COD value to within 450 mg L-1 before salt crystallization.
Compounds
#
Formula
Name
1
Na2O4S
sodium sulfate
2
ClNa
sodium chloride
3
H2O
water
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.