| 摘要 |
The invention relates to a process for the production of phosphoric acid containing calcium phosphates, i.e. Ca-containing phosphoric acid, by evaporating Ca-containing mother liquor from Odda process, whereby practically all the remaining nitrate and fluorine are removed in the form of HNO3, HF and SiF4, in which process the Ca-containing mother liquor is given a Ca/P weight ratio which is lower than 0.45 and is evaporated while recycling Ca-containing phosphoric acid, the recirculation being so controlled that the liquor has a phosphorus concentration during evaporation which is always adequate to prevent the liquor from forming a paste-like mass. Thus, it was discovered that the undesirable paste-like consistency experienced when calcium is present during evaporation can be avoided by controlling the phosphorus content. More particularly, it was found for most types of rock phosphate that the phosphorus concentration should be below about 15% by weight or above about 22% by weight in order to avoid the formation of a paste-like mass during evaporation of the liquor. |
