Hemihydrate Process (HH)

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.

DH process flowsheet.jpg

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:

  • high efficiency of reaction volume usage and Р2О5 surface efficiency at filtration unit (2÷3 times higher than at dihydrate plants of the same capacity);
  • low capital and operating costs of high efficiency reaction slurry air cooling method in the foam layer;
  • long operating time of the plant (not less than 325 days per year);
  • low electricity consumption per 1 ton of Р2О5 (~ 75 kW for Khibiny apatite concentrate);
  • high content of Р2О5 in product WPA - 31÷37%;
  • low energy costs for WPA concentration (by ~ 2 times relative to WPA dihydrate process).

Main disadvantages of the HH process:

  • particular quality of the used phosphate raw materials (not lower than 70BPL);
  • relatively low process yield - up to 96÷96.5% (for Khibiny apatite concentrate);
  • high operating temperatures of operating mediums (87÷94 °C);
  • sufficiently high emission of fluorine gases at the extraction and filtration stages.

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