The main feature of WPA production hemihydrate method is decomposition of phosphate raw materials with a mixture of sulphuric and phosphoric acids with calcium sulphate crystallization in the form of a metastable phase - CaSO4*0,5H2O dihydrate. Standard HH process flowsheet is shown in Figure 1.
Figure 1. HH process flowsheet
Plant production capacity is 160÷500 thousand tons of Р2О5 per year during processing of Khibiny apatite concentrate.
General advantages of the HH process:
Main disadvantages of the HH process:
The following types of phosphate raw materials are used as suitable for HH process: Khibiny and Kovdorsky apatite concentrates, some types phosphate rocks (China, Saudi Arabia, Jordan, Syria, Australia, etc.) as well as their mixtures.
Main parameters of JSC NIUIF HH process:
Parameter |
Apatite concentrate KOLA |
Kovdorsky apatite concentrate* |
|
Plant modernization |
New plant |
||
Plant production capacity, thousand tons of Р2О5 per year tons of Р2О5 per day |
370 1150 |
400/500 1250/1560 |
370÷400 1150÷1250 |
Reaction volume, m3 |
900 |
1150/1450 |
1800 |
Total filtration surface, m2 |
240 |
180/220 |
257,5 |
Type and number of used vacuum filters |
3 tilting pan filters |
2-3 belt filters |
2 tilting pan and 1 belt |
Р2О5 content in WPA from filteration unit, % |
35÷37 |
31÷33 |
* co-processing with other types of raw materials, plant after modernization