CEAMAG offers the TSP manufacturing technology based on slurry granulation process. This technology is widely applied in modern plants and gives excellent products qualities with easy operation and maintenance management.
The process proposed by CEAMAG presents the following advantages:
- Process uses a proven technology,
- Process can accommodate fluctuation of phosphoric acid concentration,
- Process can accommodate a variety of phosphate rocks,
- Process is simple and is of lower CAPEX compared to other routes,
- Increased density and hardness of the granules,
- Lower recycle ratio,
- Technology is environmentally friendly with reduced effluent emissions.
The proposed process route is a slurry granulation process. The process offers the advantages of a comparatively low recycle ratio plus an excellent quality with high granule hardness.
The proposed process is very flexible and can be later easily adapted for production of ammonium phosphates and NPK.
Protection of the environment is a top priority in the design of CEAMAG plants. The effluent removal and control systems are designed to comply with local regulations or with EFMA BAT standards related to the dust and fluorine emissions levels. The liquid effluents are minimized. The process can be adapted to suit the client needs and constraints for liquid effluents discharge.
The modern granulation process for the production of granular TSP is well proven and has optimised the equipment size. The process is ¨granulation-controlled¨ (not only controlled by the mass-and heat-balance). It uses the layering or “onion skin” method of creating granules. In order to ensure a low recycle ratio at high production rates, it is important that efficient screening and crushing equipment is selected. This allows the recycle of ¨small size product¨ - not dust.
Another feature of the process is the formation of even-sized particles which is the key to low recycle.
For a product like TSP with a high solubility, the granulation performance is important in order to produce hard, dense granules with excellent storage properties.
Because the process is granulation–controlled, there is no need for recycle bins or any other control of the recycle. For plant start-ups, product material may be recycled.
The main advantages of the process are:
- A simple flow-sheet without excess equipment which reduces investment and makes the process easy to operate,
- The process is almost self-controlled,
- Excellent product quality.
The finely ground phosphate rock is fed to the stirred reactor T 401 where it is mixed with phosphoric acid from storage, and the recycled scrubbing liquor. The resulting reaction slurry is circulated, homogenized and maintained in suspension by the agitator A 401.
From the reactor T 401, the slurry overflows to the slurry maturing vessel T 402, where the reaction proceeds. The vessel T 402 is equipped with the agitator A 402 and is maintained at the same conditions prevailing in T 401.
The reaction vessels T 401 and T 402 provide for the necessary residence time to achieve high completion level of the reaction between the phosphate rock and the phosphoric acid. In order to meet the quality standards related to water and citrate soluble P2O5, the TSP product is stored for curing for a period ranging between 1 to 3 weeks depending on phosphate rock quality before final conditioning and shipping.
The reaction gases and vapours evolved from the reactor T 401 and 402, are extracted and directed towards the scrubbing section, where fluorine compounds abatement takes place.
The reaction slurry is pumped from T 402, by the means of the pump P 401 towards the slurry sprayer X 410 at the inlet of the granulator B 410. The slurry spray is directed towards the curtain formed by the recycled dry product from the screening station. A process of size enlargement of the granules by layering takes place in the granulator. The rate of increase of granules size depends on the recycle rate. The granules are discharged to the dryer B 420.
The granules are contacted co-current wise with hot air from the hot air generator F 410. At the exit of the dryer, the humidity of the granules is lowered. As fresh TSP, these granules contain also free acid, which allows for continuation of reaction in the curing store. Dryer exit gases entrain TSP fine particles which are largely recovered in the cyclones S 420 and recycled with screening TSP fines to the granulator.
TSP Screening and crushing
From the outlet of the dryer B 420, the product is directed to the screening station. The vibrating screens S 430 separate the product in three fractions according to granules size. The coarse granules are removed by the primary sieve and directed through chutes to the coarse granules crusher C 430. They are subsequently discharged on the recycle conveyor M 410. The granules retained by the secondary sieve have the grain size specification of the product and are collected in the double chute hopper X 430. Part of this on spec fraction is extracted by the production belt conveyor W 440, and directed to the product cooler E 440 where their temperature is reduced, and then handled towards the curing store. The remaining on spec product is discharged by gravity on the recycle conveyor M 410.
The objective of gas scrubbing is the abatement of dust and fluorine compounds before discharge of gases in the atmosphere.
The main streams subjected to scrubbing are the reactor gas, the granulator gas, the dryer gas and the plant de-dusting gas. The recovered fines in the scrubbing liquor are recycled towards the reactor.
The scrubbing system is optimized according the phosphate rock and phosphoric acid quality and for the best integration with the production process.