GDAP granulation

 

CEAMAG offers the granulation technology based on pipe reactor plus granulation drum. This technology is applied in the most modern plants and gives excellent products qualities with easy operation and maintenance management.

Process features

  • Use of a proven technology,
  • Can accommodate fluctuation of phosphoric acid concentration,
  • Optimization of energy consumption and recycle ratio leading to optimized CAPEX and OPEX,
  • Technology is environmentally friendly with reduced effluent emissions in accordance with the most stringent regulations.

The proposed process route is a slurry granulation process, which enables use of phosphoric acid with a P2O5 content from 39% to 58%. The process which operates with an ex granulator moisture content below 2.5 %, offers the advantages of a low recycle ratio, typically 3 / 1, plus an excellent quality with high granules hardness.

The proposed process is very flexible and can be later easily adapted for production of other products as for instance:

  • MAP,
  • NPK - several types of formulas.

Protection of the environment is a top priority in the design of CEAMAG plants. The gaseous effluents removal and control systems meet the demands of EFMA BAT standards or other local specific requirement. The granulation plant does not export liquid effluent during normal operation.

The modern pipe reactor + drum granulation process for the production of granular MAP/DAP is well proven with optimised equipment size. Application of the pipe reactor process allows a low granulation moisture content and therefore the needs for drying and scrubber equipment are minimised.

The process is using the layering also called “onion skin” method for creating granules. Formation of even-sized particles, selection of screening and crushing items are key features for ensuring a low recycle ratio at high production rates and recycle of ¨small size product¨ - not dust.

The DAP product shows excellent storage and transportation properties with high solubility, hardness, and bulk density.

Process Description

Introduction

A mono-pipe reactor process is implemented in a granulation loop. The process includes the following operations:

  • Granulation,
  • Drying,
  • Screening and crushing,
  • Gas treatment.

The plant is designed for continuous operation.

Ammonium phosphate slurry at the required N/P ratio is sprayed directly onto the cascading bed of recycle material in the Granulator to create optimum granulation conditions. Ammonia is added via a sparger pipe to the Granulator to adjust the N/P ratio and thus achieve the required analysis of the DAP.

The heat of reaction is removed by evaporation of water from the ammonium phosphate slurry as it sprays out from the pipe reactor nozzles. The vapours are removed from the Granulator and pass to a gas scrubbing section where any ammonia in the gaseous stream is recovered.

Granulation

The granulator is a rotating drum of a specific design.

The granulator B 110 is fed with:

  • Dry recycled product coming from screening, crushing and dedusting; it is constituted with fine particles,
  • Slurry from the pipe reactor R 100,
  • Liquid ammonia,
  • The filler agent.

Gaseous ammonia is fed to the Pipe Reactor under ratio control with the phosphoric acid feed. The phosphoric acid and ammonia react to produce slurry of ammonium phosphate which discharges from the Pipe Reactor onto the rolling bed of solids and causes the solids to form into granules.

At the inlet of the granulator, the fine recycled particles are coated with the slurry then ammoniated by injection of liquid ammonia. The reaction between ammonia and free acid of the slurry is exothermic, which permits to evaporate part of the water content of the slurry. The granulated product at the outlet of the granulator, discharges directly into the dryer B 120. The hot gases leaving the granulator containing vapor and un-reacted ammonia are sent to the scrubber of the wet section.

Drying

The goal of the drying operation is to lower the water content of the DAP at the outlet of the granulator in order to facilitate further screening, crushing and improve its storage properties.

The wet product at the outlet of the granulator B 110 is dried in a co-current flow of hot air which is generated in the combustion package F 110. The fuel flowrate in the combustion package is monitored according to the gases temperature at the outlet of the dryer B 120.

The inlet section of the dryer is designed with flights to direct the product away from the inlet and prevent back spillage. The remaining section is designed with lifting flights, which ensures that the product cascades over the full cross-section of the dryer thereby optimizing contact between the drying air and the product.

The dusty gases at the outlet of the dryer are treated first in a battery of multi-cyclones S 120, which recovers major part of the dusts, then sent to the scrubber of the wet section. The recovered dusts are recycled to the granulator B 110.

Screening, Crushing and recycling

The dry product at the outlet of the dryer which contains fines medium and coarse particles is sent to the screens by the means of a series of belt conveyors and elevator. The screens S 130 are of double deck type. The upper deck retains the coarse product, while the lower deck retains the merchant grade particles. The screens separate the incoming product into oversize, on spec and undersize granules.

Oversize granules fall directly into the crushers C 130, then fall on the recycling belt conveyor M 110. Part of the product, which corresponds to the production, is sent to the cooler E 140, while the other part falls on the recycling belt conveyor. The undersize granules fall directly from the screens to the recycling belt.

The recycled product which consists of undersize, crushed oversize and part of the product granules is sent back to the granulator. Depending on the product formulation, a filling agent is added to the recycle.

Final Product Cooling

The product which is extracted from the granulation loop is handled towards the cooler E 140 in order to insure the suitable temperature for storage. This cooling allows to prevent caking of the DAP during storage.

At the outlet of the cooler E 140, the DAP is sent to the coating drum B 301, where it is coated with a special coating agent, in order to insure good storage and transport properties of the merchant product.

Process Gas Scrubbing

The plant generates a number of contaminated process air streams, which must be treated to remove dust, ammonia and fluorine before discharge to atmosphere.

An air stream is drawn from the Granulator B110 to remove water vapour and small quantities of ammonia and passes to the Granulator Scrubber. Phosphoric acid is recirculated around the scrubber. The partially cleaned air is discharged to the Final Scrubber where any fluorine, which was stripped from the phosphoric acid in the Granulator Scrubber is removed.

The air stream from the Dryer is withdrawn and passed through the Dryer Cyclone S120 where most of the entrained dust is removed. The partially cleaned air is passed to the Dryer Scrubber where the scrubbing medium is phosphoric acid. The partially cleaned gases from the Dryer Scrubber pass directly to the Final Scrubber.

A blowdown from the dryer and granulator scrubbers which consists of partially neutralised phosphoric acid and recovered dust, is discharged to the Pipe Reactor Feed Tank T100.

 

Typical figures
Typical Productions: From 500 to 1500 mtpd
Product Quality:  
Nitrogen content 18%
P2O5 content 46 %
Moisture 1 % max
Granulometry (typical) 90% min between 2.0 and 4 mm
GDAP granulation
GDAP granulation
GDAP granulation
GDAP granulation