Proposed modifications to the method for the determination of available lime

Lime is an important industrial chemical used widely in the steel manufactu ring and water treatment industries. One of the major procedures employed t o control the quality of lime during its production process is the so-calle d available lime (Av CaO) method. This method measures the theoretical amou nt of lime available for neutralisation purposes, and also gives an indicat ion of the degree of conversion from limestone to lime. It entails the diss olution of the material in a sugar solution. followed by subsequent titrati on of the resultant solution with a standardised acid. The standard SABS pr ocedure requires a shaking time of at feast four hours. This is followed by a prolonged period of standing to allow colloidal metal oxides (mostly Fe2 O3 and MnO2), as well as grit, to settle from the solution. Usually it is o nly possible to remove a clear aliquot from the solution for titration purp oses after at least six hours of standing. This all result in the method re quiring at least 1-2 days to perform before a final value cart be obtained. This investigation describes proposed changes to the current method, with t he aim to save both time and quantities of reagents used in the process. It entails alternative methods of agitation, variation in the concentration o f reagent used and employing microwave extraction of the lime from the suga r solution. It was found that the current method can be streamlined to yiel d similar results in a much shorter time period and with vastly smaller amo unts of reagents consumed. The time and materials savings can be translated into significant financial benefits in everyday plant operations. (C) 2001 Elsevier Science Ltd. All rights reserved.