Análise do processo de cominuição para combustão do carvão mineral de Candiota

Abstract

The following work has as a goal to analyze coal comminution process available at Mina de Candiota (mining site located at Candiota, Rio Grande do Sul, Brazil) making it suitable for combustion in thermoelectric power plants. Coal is available in many layers, however, only the top layer and the bottom are apt for thermal purposes, even though those layers are classified from low quality to very low quality in relation to your grade. Immediate analyzes were performed daily for two months, as well as researches in annual analyzes carried out in the last eight years, finding the average contents, on a dry basis, rates ash rates of 53,86%, volatile material 21,44%, fixed carbon 23,98%, Sulphur 1,44% and superior calorific power 2818,62 Kcal/kg. After exploited from the mining site, the coal suffers processes of crushing, milling and classification. CRM has two crushers that reduce the coal to a maximum diameter of 120 millimeters, sending them to the thermoelectric power plant. At CGTEE, the coal is once again crushed until it reaches a granulometry of 30 millimeters, then it is sent to the milling machines which reduce the coal to, approximately, 0,074 millimeters particles size, equivalent to the 200 Tyler series mesh sieve size. A comparison was made between the electric energy currently spent by the mills and values determined by empirical models, where it was verified that the current energy consumption is 106% above the theoretical value. Adjustments on particles granulometry classification equipment were performed accordingly to PDCA cycle. Granulometry analysis at the classification machines showed that the coal granulometry varies accordingly to the fins adjustments, however with strong interference of other factors, as coal drag airflow for instance. Due to this interference, a standard procedure for fins adjustments could not be created. It was noticed that with the fins opening and therefore a granulometry rise, there was a boost on electrical energy generation, however, with a following rise on the ratio of unburned coal on the ashes from 2,0% to 11%. Therefore, classification machine fins adjustment is suggested seeking for a balance between unrestricted energy generation and the reduced ratio of unburned coal on ashes.