Nitrogen+Syngas 391 Sep-Oct 2024
30 September 2024
Pastillation of specialty urea products
FERTILIZER FINISHING
Pastillation of specialty urea products
IPCO has expanded its Rotoform range with the high yield XG model for granulation of suspensions. Designed for applications such as sulphur bentonite and urea mixes as well as NPK and other fertilizers, this new Rotoform model can convert solid-containing product melts into consistent, high quality pastilles from 2-4 mm diameter.
IPCO has announced the introduction of the Rotoform XG, a high capacity pastillation system for fertilizer finishing, offering superior handling of low viscosity melts containing solid particles. Further enhancements incorporated into this latest addition to the company’s Rotoform range include significantly easier cleaning and maintenance.
Designed for applications such as sulphur bentonite and urea mixes as well as NPK and other fertilizers, this new Rotoform model can convert solid-containing product melts into consistent, high quality pastilles from 2-4 mm diameter. The XG is also able to process other products containing solid additives or contaminant particles up to 200 μm in size.
Offering twice the throughput rates of the base model Rotoform 4G, the XG is capable of processing slurries with melt viscosities up to 100 mPas.
The design follows the same basic principle that has seen more than 2,500 Rotoform systems installed since the process was first launched. Liquid product is delivered to a stator then deposited in drop form via a rotating perforated outer shell onto a continuously running steel cooling belt.
However, the XG incorporates a number of innovations including a sliding base frame that allows the Rotoform to be pulled out for easy access, and a floating stator that makes cleaning and maintenance much easier. A bearing system with fewer parts and increased wear resistance further reduces maintenance requirements.
“This is a major development in terms of handling slurry and abrasive products,” says Ulrich Nanz, Global Product Manager, Chemicals, at IPCO. “The high capacity of the system maximises productivity, while easier cleaning and maintenance equates to lower costs.”
IPCO can also supply upstream solutions including blending and grinding units to combine liquid and solid products into suspensions, enabling the production of specialty urea products such as:
- urea + sulphur
- urea ammonium sulphate (UAS)
- urea + potassium
- urea blended with micronutrients
Other special fertilizers that can be produced on these systems include ammonium nitrate, calcium nitrate, magnesium nitrate, and sulphur bentonite. The company can also supply a complete range of downstream handling and bagging systems.
One of the major advantages of IPCO’s in-line systems is that production can be switched from one product to another with only minimal modification. This ability to control dosing allows product ratios to be varied to meet different needs. It also means that new fertilizer products can be brought to market more economically. And if production capacities need to be increased, multiple Rotoforms can be run in parallel.
This flexibility makes IPCO’s Rotoform XG ideal for debottlenecking, for upgrade projects or for reducing overall plant emissions by transferring a proportion of existing production to pastillation.
Rotoform solidification – one principle, multiple applications
IPCO introduced the Rotoform rotary drop-forming technology in the late 1970s and while the core principle – direct-from-the-melt solidification on a steel belt cooler – remains unchanged, the technology behind it has undergone significant development over the years.
In 2013 the company – then operating as Sandvik Process Systems – introduced the Rotoform 4G, a model that today forms the foundation of an entire family of systems capable of meeting a wide range of process requirements. These include the granulation of abrasive and sediment materials, melts requiring a high feed temperature (e.g. bitumen, resins), and the pastillation of subcooling melts in supercooling plants (e.g. antioxidants).
Other previous developments include the Rotoform HS, a high speed model capable of processing up to 350 tonnes of sulphur per day.
The core Rotoform design is based on a heated stator and a perforated rotating shell that turns concentrically around the stator. A pump delivers the molten product from a vessel or pit to the Rotoform system via heated pipes and a filter.
The design of the system takes into account a number of factors including the required pastille diameter, the density and viscosity of the molten product, the surface tension, and the mechanical acceleration applied to the droplet. The droplet weight and volume, and the distance between the outer shell of the Rotoform and the steel belt must also be determined on a product-by-product basis. These parameters are calculated either by computer simulations or pilot plant testing at one of IPCO’s global productivity centres.
A system of baffles and internal nozzles built into the stator delivers uniform pressure across the whole belt width, ensuring even flow through all holes of the perforated rotary shell and a uniform end product. Precisely metered drops of the product are deposited by the nozzle bar across the whole operating width of a continuously running stainless steel cooling belt.
The rotational speed of the unit is synchronised with the speed of the steel cooling belt to allow the liquid droplets to be deposited without deformation. After the drop has been deposited, any residual product remaining on the outer shell is returned to the Rotoform by a heated refeed bar, which keeps the outer shell clean. Heat released during cooling and solidification of the melt is transferred via the steel belt to cooling water sprayed underneath.
The product droplets are then discharged as solid, hemispherical granules at the end of the cooling system. To eliminate the possibility of product damage during discharge – and to further minimise dust – a thin film of release agent can be sprayed onto the steel belt. This is managed using IPCO’s ProForm system, a purpose-designed solution consisting of two parts:
- ProMix: This automates the mixing of water and a release agent (different types used for different fertilizers), ensuring a uniform ratio for precise dosing and optimum performance.
- ProSpray: This advanced spraying bar system delivers the release agent to the steel belt in a controlled and targeted way to ensure clean discharge of the end product and most efficient use of materials.
The Rotoform process offers a number of environmental advantages. Closed loop cooling means that the cooling water never comes into direct contact with the product so there is no risk of cross contamination; the water can be collected, re-cooled and used again.
Secondly, rapid solidification results in very low emission values. And low levels of dust levels mean no need for exhaust air treatment.
Finally, with extremely low energy consumption requirements, Rotoform solidification represents an economical as well as sustainable solution for fertilizer producers, farmers, and the environment.
