Natural Fragmentation Model of Zirab Coals, Iran

Abstract

Iran's coals occur in the Alborz range (north) and Central Iran basins. The Zirab is typical coalfield in the Al- borz coal basin. From litho types of view, the coals are mainly clarovitrinite to clarodurite type which are used as source of coking coal for metallurgical factories. During the research we used 10 typical samples from Zirab coal mine to esti- mate fragmentation model of natural particle-size distribution of these coals. Prediction of natural fragmentation proper- ties from coals was the main aim of this research. In order to calculate the natural fragmentation model at any stage of the extraction (or sizing) operation, we tried to find similar models that combine both natural fragmentation and degradation through natural crushing. The results our research suggest a power-law and a log-normal behavior for the distribution of the smaller and larger coal fragments, respectively. We show that the probability function that models the production of particles of different size from an initial mass and sorts that distribution is related to mass and compositional factors of coal particles. Also, our studies showed that during the fall of coals from 4m height, fragmentation followed a range of 10 percent, per time for particles smaller than 5 mm diameter. It means that if the processes would repeat 10 times, 100 per- cent of coals would crush to the size of less than 5 mm. natural fragmentation is usually the first step in creating size distribution. Natural fragmentation during the excavation, blast- ing and subsequent ore minerals. Previous models of fragmenta- tions in soft and hard rocks are useful for economics of many operations in the minerals industry. This paper presents an in- vestigation about amount of coal particles produced during min- ing, handling and transporting before crushing and milling. MATERIALS AND METHODS Iran's coals occur in the Alborz range (north) and Central Iran basins. The Zirab is typical coalfield in the Alborz range coal basin. The coal bearing sequences in this range are con- tained in the Upper Triassic to Middle Jurassic Shemshak Formation, which consists mainly of sandstone, shale, silt- stone, and claystone. From litho type's point of view, these coals are mainly clarovitrinite to clarodurite type which are used as source of coking coal for metallurgical factories. The coking coals have relatively high vitrinite (60-90%), and low inertinite (10-20%) and liptinite (5%) contents. The domi- nant macerals of the vitrinite group are telinite and collinite. Syngenetic pyrite, marcasite, detrital quartz, siderite, calcite, illite, and kaolinite are the main minerals in these coals. These coals seem to have strength of 5 to 10 MPa similar to those tested before in the Zirab coal mine (4-6). During the research we used 10 typical samples from Zirab coal mine. For this experiment, samples of bright banded pure coal were collected from coal seams. The coals were chosen such that they represent a wide variety of coal type and textures.