Method for reducing magnesium and aluminum impurities in wet-process phosphoric acid

Abstract

The invention discloses a method for reducing magnesium and aluminum impurities in wet-process phosphoric acid. The method comprises the following steps: adding an ammonium fluoride-containing compound into wet-process phosphoric acid, wherein the addition mount of the ammonium fluoride-containing compound is 0.5-5 percent of the mass of wet-process phosphoric acid, the aging temperature is 30-80 DEG C, and the aging time is 5-48 hours; performing free settling, wherein the supernatant liquid is purified wet-process phosphoric acid with low magnesium and aluminum content. The sediment obtained by the method is large in particle and easy to settle, and a removal rate of magnesium and aluminum impurity ions can be 5-40 percent. The method is easy to operate, low in treatment cost and easy for realization of industrial production and has high industrialization popularization value.

Description

technical field [0001] The invention relates to a method for purifying wet-process phosphoric acid by chemical precipitation, in particular to a method for reducing magnesium and aluminum impurities in wet-process phosphoric acid with fluorine-containing ammonium compounds. Background technique [0002] Wet-process phosphoric acid is an important intermediate product for the production of phosphate fertilizers, such as diammonium phosphate (DAP), monoammonium phosphate (MAP), and triple superphosphate (GTSP). However, with the substantial development and utilization of phosphate rock resources in recent years, the quality of phosphate rock has been continuously depleted, and the Fe, Al, and Mg impurities in wet-process phosphoric acid have gradually increased, resulting in an increase in the MER value of the wet-process phosphoric acid impurity coefficient (MER The value refers to Fe in wet-process phosphoric acid 2 o 3 、Al 2 o 3 , the sum of the mass percentages of MgO ...

AI Technical Summary

Problems solved by technology

However, with the substantial development and utilization of phosphate rock resources in recent years, the quality of phosphate rock has been continuously depleted, and the Fe, Al, and Mg impurities in wet-process phosphoric acid have gradually increased, resulting in an increase in the MER value of the wet-process phosphoric acid impurity coefficient (MER The value refers to Fe in wet-process phosphoric acid 2 o 3 、Al 2 o 3 , the sum of the mass percentages of MgO and P 2 o 5 The ratio of mass percentage, namely (Fe 2 o 3 +Al 2 o 3 +MgO) / P 2 o 5 ), which has a great impact on subsequent product processing, especially the production of DAP with a total nutrient content of 64%, and it is difficult for the nitrogen content of the product to meet the requirements of superior products

In response to the trend of continuous depletion of phosphate rock resources, it has been a common task for the entire industry to develop a relatively economical technology for reducing impurities in wet-process magnesium phosphate, iron, and aluminum to meet the production requirements of DAP and other products. Some work has been carried out, but all the time, little effect has been achieved. So far, there has been no industrialized report on the use of chemical precipitation to reduce the impurities of iron, magnesium and aluminum in wet-process phosphoric acid.

[0003] There are many research reports on the purification technology of wet-process phosphoric acid at home and abroad, and there are usually three methods: 1. Organic solvent extraction, which is a purification process successfully developed in recent years and has been industrialized. The purified acid obtained is of good quality and can basically be compared with Thermal phosphoric acid is comparable, but the disadvantage is that the purification cost is high, and the obtained purified acid is generally limited to the production of industrial-grade phosphorus chemical products

2. Ion exchange method, which is also a method suitable for the deep purification of wet-process phosphoric acid, the purification cost is high, and the obtained products are generally limited to the production of industrial-grade or food-grade phosphorus chemical products

But this method uses many chemicals, and potassium oxalate is expensive, the treatment process is relatively complicated, there are many influencing factors, and the treatment cost is high. In addition, this method has no effect on removing magnesium impurities

[0013] In addition, the exploratory test of magnesium removal in the process of phosphoric acid concentration, Phosphate Fertilizer and Compound Fertilizer, No. 2, 2007, described the (NH 4 ) 2 SiF 6 It is a magnesium removal precipitant, and the technical and economic indicators that meet the favorable conditions in the test are: concentrated phosphoric acid w( P2O5) 50.39%, magnesium removal rate 47.42%, M.E.R 0.0744, concentrated acid after 24 hours of precipitation, w (solid) is 0.23%, but This method is only effective for magnesium removal, and has no effect on the removal of aluminum impurities. In addition, this method needs to be under the condition of high acid concentration, and the precipitate is greatly affected by the acid temperature. Higher acid temperature is not conducive to the formation of precipitates. Basically no industrial application significance

[0014] To sum up, there are no relevant reports on the use of fluorine-containing ammonium compounds to reduce magnesium and aluminum impurities in wet-process phosphoric acid