POLISH JOURNAL OF FOOD AND NUTRITION SCIENCES www.pan.olsztyn.pl/journal/ e-mail: joan@pan.olsztyn.pl Pol. J. Food Nutr. Sci. 2007, Vol. 57, No. 1, pp. 51–56 PARTICLE SIZE DISTRIBUTION OF RE-USED CARBONATION MUD Evzen Sarka, Zdenek Bubnik, Pavel Kadlec Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Key words: carbonation mud, particle size distribution, hydrocyclones, wastes from food technology, image analysis Carbonation mud contains CaCO 3 and aggregated or adsorbed substances from sugar beet raw juice. The precipitate can be characterised as a polydisperse system. Large volumes of carbonation mud predetermine its use as a fertilizer. Other possibilities of utilization are tested – e.g. addition in animal feed mixtures, application as paper, plastic and rubber fillers, and usage for the building industry and for desulphurization of combustion gases. Re-using of carbonation mud in sugar technology enables to decrease lime consumption in a sugar factory and to minimize carbonation mud production. It involves economic aspects and environmental effects (decreasing lime stone mining and limiting carbonation mud production). For these feasible internal or external applications of carbonation mud it is necessary to know size distribution in advance. The research work was aimed at particle size distribution measurement of carbonation mud suspension, which was separated in hydrocyclones used in MZ-technology. This low-cost sugar juice purification method is based on re-using carbonation mud and following separation of mud particles. Authors have chosen an image analysis method (system LUCIA) combined with microscopic observation for particle equivalent diameter determination. At first it was necessary to work out original measuring methodology for carbonation mud, it includes choosing suitable object-lenses, design of lightning, preparing suitable subroutine in which values of contrast and threshold are defined, etc. From these size data the particle size distribution was calculated. We detected that the industrial method for the preparation of input mud suspension was not fine enough and an amount of small particles increased in comparison with the unfiltered 1 st carbonation juice. Bottom output suspension of hydrocyclones was of worse quality with small par- ticles than the 1 st carbonation juice as well. Hydrocyclones did not affect small particles. A normality of size distribution of particles from input and output suspensions in MZ-technology was tested. It can be characterised by normal distribution function for volume fraction x V or by log-normal distribution function for frequency of particles, as to input particles and upper output particles of hydrocyclones. The measured results will be groundwork for next carbonation mud applications. SYMBOLS AND UNITS A (µm 2 ) – scanned cross-area of the particle; d e (µm) – equivalent diameter of the particle; DS (%) – dry sub- stance; n (1) – frequency, number of particles; np (1) – the- oretical (expected) frequency, number of particles; pCaO (g CaO/ 100 mL) – lime addition; Sd (g/kg) – solids content; x V (%) – volume fraction of the interval in relation to whole volume of solids; d (–) – standard deviation; c 2 (–) – statisti- cal characteristic defined by equation (2) INDEXES j – interval sequence; k – number of intervals INTRODUCTION An addition of lime milk into sugar beet raw juice coagu- lates colloid substances and precipitates non-soluble or hard- ly soluble substances. Subsequently the lime surplus is pre- cipitated by carbon dioxide and originating 1 st carbonation juice or carbonation slurry concentrate is filtered (Figure 1). The precipitate, called carbonation mud, contains fine crys- tals of CaCO 3 and aggregated or adsorbed non-sugars; e.g. phosphates, magnesium, potassium and calcium salts, trace elements, nitrogenous and other organic compounds, includ- ing colour substances. Industrial and agricultural application of carbonation mud Great volumes of carbonation mud predetermine its use as a product – fertilizer. Tank cars transport liquid carbon- ation mud to fields for fertilization, where it is pumped to sprayers. It is necessary to dose about 10 t/ha of carbonation mud (DS = 70%) to increase soil pH from 6.0 to 6.5 or 7.0. Carbonation mud helps to increase calcium content; it fas- tens stabile mould structure and thereby supports active life in soil. There was tested an addition of carbonation mud to feed mixtures where it supplies calcium for nutrition of animals. But it is necessary to have veterinary and legal approval for this application. Carbonation mud can be used for cement and breeze- blocks production, etc. However, some residual sugar con- tent in mud can inhibit solidification of concrete or mortar mixtures. Author’s address for correspondence: Evzen Sarka, Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Technicka 5, 166 28 Praha 6, Czech Republic, tel.: (420) 22044 3115; fax: (420) 22044 5130; e-mail: evzen.sarka@vscht.cz © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences