Can binders improve SSP fertilizer granule hardness and storage characteristics?

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A junior engineer at a fertilizer production company is tasked with enhancing the hardness and storage characteristics of SSP granules, which are currently too soft and require lengthy drying times. The engineer is exploring binding agents such as sodium silicate, potassium silicate, lignosulfonates, and bentonite clay but is struggling to find reliable information on their application. Concerns have been raised about sodium silicate potentially lowering water solubility of the granules after drying. Advice suggests that bentonite clay could be beneficial, particularly if used in a slurry form with a biodegradable surfactant to enhance hydrophobic properties. However, there are concerns about adding bentonite in slurry form due to potential neutralization of acids and issues with reactor plugging. The discussion emphasizes the need for careful consideration of the form and method of incorporating these agents to avoid operational challenges and improve granule strength.
rommie
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Dear Forum

I am a junior engineer newly appointed by a fertilizer production company. I have been given the assignment to improve the SSP granule hardness and storage characteristics. Currently the granules are too soft and the drying time prior to bagging is also long. I am considering adding a binding agent to the fertilizer. I have considered sodium silicate, potassium silicate, lignosulfonates or bentonite clay as possible agents. However I am having considerable trouble finding reliable information regarding the use of these agents and the application methods. For example I am worried that if I should use sodium silicate, the granules' water solubility would be lowered considerably after drying in the drier. The fertilizer powder is granulated using drum granulators and water. Any advice or information is sincerely appreciated.

Regards
Rommie
 
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I am sure you will find literature from bentonite producers, and it can be added as a slurry to bind or act as a final coat. It should also become somewhat hydrophobic if a small amount of biodegradable surfactant is used in formulating. Look in patent literature with appropriate boolean search terms.

I would steer clear of silicates as they could render any micronutrients as insoluble rock. Also silicates can be hard to dry compared to clays.
 
Hi

Thank you for the advice!I have started to research bentonite clay. According to the plant manager it cannot be added in slurry form, he didn't explain why though, I'm assuming the clay might neutralize the acid in the slurry and influence the reactions. I am not sure whether adding it in a powder form to the powdered fertilizer and then granulating it using water would have any notable increases in granule strength. I am still searching for information and will post as soon as I have something that may be of interest.

Regards
Rommie
 
I can understand if the reactor is a tube or other reactor than a tank; plugging with clay would be very bad indeed... I thought however, that the fertilizer xtal slurry might be able to withstand the introduction of a clay slurry that is very dilute and held suspended with surfactant. The lines that feed the slurry would always have to be moving or plugging would be a problem due to the thixotropic effects of bentonite slurries.

If you are using a spray drier, the bentonite could be suspended in the drying air and may coat the prills and produce some of the results- I suspect it will also cause a lot of extra downtime chipping away coated walls... !>)
 

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