Desmet Ballestra is a Prayon Technology permanent licensee since 2009. Offered processes are based on both Di-Hydrate (DH) and Hemi-Hydrate (HH) gypsum formation and different combinations of the two processes, to be selected according to several factors as rock quality, required acid concentration, water availability, steam consumption.
Features of the proposed solutions
All available process allows the production of 52-54% Phosphoric Acid, after a concentration step. The phosphoric acid is mainly used as feedstock component in the fertilizers production plants.
High efficiency in the conversion of phosphates and in the control of the phosphate, granted by the adoption of Best Available Technology together with Prayon process design, minimizing the risk of plant packing and extending plant availability.
Air pollution control, by means of a dedicated scrubber, to comply with plant emissions level required by the most stringent laws and standards.
Well proven know-how in selecting the most suitable materials of construction to grant acid resistance.
The plant configurations allow the recovery of fluosilicic acid (FSA) as process by-product, with concentration up to 18%. The FSA can be sold as such to the market, or further transformed into valuable AHF (Anhydrous Hydrofluoric Acid) or AlF3 (DBI collaborates with Buss ChemTech for such technology) or neutralized for disposal.
Tailor made configuration
Desmet Ballestra Phosphoric Acid plants are highly customizable to process several types of phosphate rocks and maximize the plant efficiency.
Phosphoric Acid Plants Technology
Desmet Ballestra offers plants based on the following Prayon Technology processes:
- DH : Di-Hydrate (single crystallization)
- HH: Hemi-Hydrate (single crystallization)
- CPP: Central Prayon Process (double crystallization DH-HH)
- HDH: Hemi-hydrate to Di-Hydrate (double crystallization HH-DH)
- DA-HF: Di-hydrate attack, Hemi-Hydrate filtration (double crystallization DH-HH)
The choice of the most suitable process will take into consideration several factors as rock quality, required performances and economics (CAPEX, raw materials consumption, water-steam consumption). Each plant design is specific to Customer needs.
The table below compares the different phosphoric acid processes (bars provide relative magnitude):
These processes have been widely applied in many phosphoric acid projects around the globe, becoming the leading processes in the market due to their versatility and specific advantages:
- Well proven process
- Ability to efficiently convert different types of phosphate rock (sedimentary and igneous)
- Lower maintenance cost and higher operating factors
- Single/double stage filtration
- Ease of operation/shut-down, flexibility and easy transport of gypsum
- Lower grades of construction materials required
- Easier control of water balance
Double crystallization solutions, in particular DA-HF, can be adopted to revamp existing plants, e.g. to debottleneck DH process plants, increasing the production capacity with a limited investment cost.
Each technology process route incorporates the most updated Prayon technological solutions and Profile (part of Prayon Group) proprietary components, such as:
- Multi-compartment reactor design, allowing flexibility and easy control of the sulphate in the attack section, reducing P2O5 losses in the calcium sulphate.
- Sulphate gradient of the slurry in the attack tank or in the conversion tank, which minimizes the insoluble losses and/or regulates gypsum crystal type.
- The level of sulphate gradient from one zone to the other can be adjusted based on process parameters and the origin of phosphate rock.
- Low Level Flash Cooler (LLFC), which is more accurately controllable than air cooling, especially when the cooling rate must exceed nominal capacity.
- Prayon Proprietary Agitators, having high efficiency and low power consumption, which is a critical parameter for the economical sustainability of the phosphoric acid production.
- Prayon Tilting Pan Filter, incorporating the latest development (“fast drain” cells, central valve, the inverting track design), which is recognized to be the best available filter in the phosphoric acid industry, having the highest washing efficiency. Horizontal Belt Filters can be also used for filtration.
Phosphoric Acid Technical Grade (Purified Phosphoric Acid)
Desmet Ballestra has Phosphoric Acid Purification in its Chemicals technology portfolio since 2015, when it has been awarded a large Phosphoric Acid project, including Phosphoric Acid Merchant Grade purification.
Phosphoric Acid purification process is the result of several removal steps put in sequence and with recycles to achieve the target quality (main impurities removed include Arsenic, Gypsum, Heavy Metals, Fluorine, Chlorine) and recovery yield.