The effect of sodium alginate, lignosulfonate and bentonite binders on agglomeration performance and mechanical strength of micro-fine agricultural lime pellets

Abstract

Agricultural lime (crushed limestone) is often applied to acidic soils as the release of carbonate ions neutralize acid forming compounds, such as those added during fertilizer addition. Agglomerated micro-fine limestone is an attractive alternative to powdered limestone, mitigating product losses as a result of windy conditions during application. This article examines the production of agglomerates using sodium alginate, lignosulfonate and bentonite binders for micro-fine CaCO₃ powder. Central composite design was used to determine the optimal (i) amount of liquid, (ii) concentration of binder added to maximize the yield of agglomerates of 2–5.6 mm in diameter. Thereafter, four mechanical strength tests were carried out on the agglomerates, where strength was compared dependent on the binder and concentration thereof. The results show that lignosulfonate agglomerates performed the worst of the three binders, whereas agglomerates of >3 g/kg sodium alginate and 70 g/kg bentonite were acceptable in strength. While sodium alginate is a more expensive binder per gram, its high strength at relatively low levels may recommend its use industrially, contingent on economic modeling. This article successfully demonstrated the varying mechanical strengths of various limestone binders, which may assist with the development of novel soil amendment products.

Keywords:

• Agglomeration
• sodium alginate
• bentonite
• lignosulfonate
• limestone

Acknowledgments

The authors would like to thank Gideon Schreuder from Equalizer AG and HP Steenkamp from Lime Chem for their contribution to this study.

Additional information

Funding

AECI (Nulandis) assisted in funding with no involvement in study design; in the collection of data; analysis or interpretation of data; in the writing of the report; or in the decision to submit the article for publication.