Properties Affecting the Reactivity of Lime

Lime reactivity is the most used identification parameter for lime quality. The reaction may vary in its rate and maximum reached temperature. In this study, the influence of the properties of limestone on the course of the reaction is studied. The samples are thoroughly examined from a geological point of view (geological age and origin, genesis and diagenesis) and their physicochemical properties are described (total porosity, limestone category, chemical analysis, insoluble residue). Different temperatures and isothermal loads were selected to study the effect of the burning process on the lime microstructure. The newly formed CaO is observed by scanning electron microscopy (SEM images). Lime reactivity analysis is performed, and different reaction courses are compared.

Decomposition of Crystalline Limestones during the Burning Process

The decomposition of limestone during the firing process is mainly based on the decarbonation of CaCO3. In the case of crystalline limestone, it is the decomposition of calcite crystals. In this study, different limestone properties on the course of decarbonation are studied. Therefore, the samples are determined from a geological and physicochemical point of view (geological age and origin, total porosity, limestone category, chemical analyses and insoluble residue). After thorough identification of the samples, various analyses focused on limestone and lime microstructure are performed, such as SEM image analysis or lime reactivity. For these analyses, the samples are burned at different temperatures. The decrepitation amount of limestones during burning process is determined.

Evolution of physicochemical properties of quick lime at converter-smelting temperature

The volume stability caused by the hydration of f-CaO is one of the main obstacles to the comprehensive utilization of steel-making slag. In view of the f-CaO produced by incomplete dissolution of lime, it is necessary to strengthen the dissolution behavior of lime in the converter process. The reactivity of lime determines the dissolution efficiency and is closely related to its microstructure. The experimental results show that the reactivity and porosity of quick lime decrease and the average diameter of pore increases with an increase in temperature. The CaO crystals gradually grow up under the action of grain boundary migration. When the temperature increased from 1,350 to 1,600°C, the lime reactivity decreased from 237.60 to 40.60 mL, the porosity decreased from 30.55 to 15.91%, the average pore diameter increased from 159.10 to 1471.80 nm, and the average CaO particle size increased from 0.33 to 9.61 µm. The results indicate that reactivity is decreased because of the deformation and growth of CaO crystals and the decrease in porosity in reactive lime. This will cause an obstacle to the dissolution of lime and is not conducive to the control of f-CaO in slag.

CALAGEM E SILICATAGEM EM SOLO INCUBADO COM DIFERENTES UMIDADES

The lime is theacidity correctivemore used inbrazilian agricultural soils, but important benefitscan be obtained fromcalcium and magnesiumsilicates. The aim ofthisstudy was to comparethe effectofneutralizingsoil aciditybyapplication of lime andsilicate, with incubationof the correctivesin soil conditionsmore orless moisture. The experiment was conductedin the Soil Chemical Analysis Laboratoryat the UNOESTE, using soil collected in the layer0-20cmof a Sandy Loam Argisol. The experiment was carried out in acompletely randomizedina 2x2x5 factorial scheme, with twocorrectives(lime and silicateof Ca andMg), twosoilmoistures(80 and20% moisturesoil saturation) and five times (60, 90, 120, 150 and180 daysafter incubation) ofsoil chemical properties. It was submitted to variance analysis and the effects of soil moisture and correctives were evaluated by Tukey test (p<0,05) and the incubations time were evaluated by regression analysis.The silicatehas a higherneutralizing capacityof soil aciditythan lime, and thusits dosageshould be further investigated, because the use of the calculationto determine thelime requirementcan overestimatethe need forsilicate applied. The lime reactivity in the soil is not influenced with soilmoisturebetween 20and 80% moisturesaturation, unlike silicate,which has itssoilreactivityenhancedin thecondition ofhigher moisture.Thesoil corrective actionacidityby bothcorrectiveremainsincreasingup to 180days ofincubation,however,satisfactory resultsare alreadyobtainedwith 60days ofsoil incubation