HWAHAK KONGHAK, Vol.24, No.3, 203-213, June, 1986
석회석의 소성기구
Calcination Mechanism of Limestone
초록
석회석의 소성반응은 흡열반응으로써 석회석과 생석회의 반응계면에 뚜렷한 경계면을 형성하면서 석회석의 중심부를 향하여 구형을 유지하면서 진행된다. 석회석의 소성반응은 첫째, 주위의 기체와 석회석 크기 사이의 복사와 대류에 의한 열전달, 둘째 생석회 층에서의 전도에 의한 열전달, 셋째 석회석과 생석회 사이의 계면에서 일어나는 화학반응, 넷째 생성된 생석회 층을 통한 CO2가스의 외부로의 확산 등에 의해 이루어지며 이 속도과정 중 생석회 층에서의 열전도가 율속단계임을 알았다. 위의 속도과정을 고려하고 미반응학 모델을 적용하여 석회소성반응에 대한 이론식을 유도하였고 이 이론식에 의해 소성온도, 소성시간 및 석회석의 크기 변화 등의 상관관계를 살펴보았다. 석회석의 소성반응에서 반응속도를 시간에 따른 CO2 무게의 감량으로 표시할 때 반응속도는 외부에서 전달되는 온도와 석회석의 분해가 일어나는 온도와의 차에 비례하였으며, 비정상상태법에 의해 600 ℃ 이하에서 석회석 및 생석회의 열전도도를 측정하였다.
It has been shown that calcination of limestone is endothermic reaction and takes place on a definite boundary between the undecomposed limestone and the layer of porous lime formed outside it. This boundary moves towards the center of the limestone but remains spherical in shape. The rates of reaction occurring during the calcination of limestone are involved the following four processes.
The first two processes are heat transfer between gas and limestone by radiation and convection and conduction of heat in the product layer （lime）. The other two processes are chemical reaction in the reaction interface and CO2 gas diffusion in lime. Especially the rate of reaction was controlled by the conduction of heat in lime.
Applying to the unreacted-core model, rigorous expressions based on heat transfer rate have been derived for the prediction of relations between time required for complete calcination, temperature, and sizes of limestone.
When the rate of reaction of limestone was given by ignition loss weights of CO2 at any time, it was proportional to the difference between the temperature supplied from the surroundings and the decomposition temperature of limestone. The experimental values of the thermal conductivities of limestone and lime were determined by the unsteady state method in the temperature ranges below 600 ℃.
The first two processes are heat transfer between gas and limestone by radiation and convection and conduction of heat in the product layer （lime）. The other two processes are chemical reaction in the reaction interface and CO2 gas diffusion in lime. Especially the rate of reaction was controlled by the conduction of heat in lime.
Applying to the unreacted-core model, rigorous expressions based on heat transfer rate have been derived for the prediction of relations between time required for complete calcination, temperature, and sizes of limestone.
When the rate of reaction of limestone was given by ignition loss weights of CO2 at any time, it was proportional to the difference between the temperature supplied from the surroundings and the decomposition temperature of limestone. The experimental values of the thermal conductivities of limestone and lime were determined by the unsteady state method in the temperature ranges below 600 ℃.