Study of the impacts of lime-based products in beet sugar purification process

Abstract

The purification of sugar is studied in this master's thesis. Sugar factories usually use quicklime and carbon dioxide for their purification. In order to reduce the greenhouse gas emissions associated with it and provide a better product to sugar factories, a patented product is investigated in which a part of the quicklime is substituted with milled limestone. The purification process is carried out on a laboratory scale using raw materials from sugar factories such as raw juice and sweetwater where different ratios [CaO]/[CaCO\textsubscript{3}] are tested in the form of a milk of lime. Analysis on the milk of lime shows that the theoretical ratio is not a fit parameter to observe for the interpretation of results. The principal analysis techniques employed are the CaO available and neutralizing value analysis. It is less precise for limed juices. The carbonation had not been well controlled and may have impacted the quality of the thin juice. The quality of the final product of the purification process, the thin juice is investigated. The parameters evaluated on the thin juice are the absorbance and the residual calcium ions. The absorbance seems to be constant regardless of the concentration of limestone in the thin juice. The residual calcium ions found in the thin juice might be due to some ions seeping through the filter during filtration. It is found that the protocol needs some improvements and the analysis technique on the limed juice needs to be modified. Once these modifications are implemented, different types of quicklime and milled limestone mix can be tested. From that, different process parameters such as the alkalinity of the limed juice and the flow rate of CO2 can be varied to find the best operating conditions for the best quality of the thin juice.