Coal Mining Facilities Descriptions
Coal mine sites vary in size, but typically involve a large commitment of land, especially for surface mining. Coal seams vary in depth and quality, and the mining of the coal will only occur in seams that are economically viable and in locations that are technically feasible to mine. The size of the mining operation will depend on the site characteristics, the coal reserve, and the method chosen for mining.
Primary Facility Components
The development of a coal mine includes construction of roads, utility line connections, and the mine plant. Depending on the amount of coal produced and where it is to be used, construction of a railroad spur may be required. For coal that contains excessive impurities, a beneficiation or washing plant may be required. Otherwise, the mine plant consists of coal handling and storage facilities, offices, shops and laboratories, equipment storage buildings, and waste disposal areas. If the coal is to be mined by underground methods, the mine plant is constructed near the main portal or entrance. For coal mined by surface methods, the mine plant would be located off the outcrop, if possible.
Access to coal deposits at an underground operation is provided by drifts, slopes, or shafts. The coalbed is developed for further operations by driving entries. Although terminology varies, the following system of entries is universal in the industry. Main entries are extensions of access openings and often run several miles in one direction. Three or more parallel entries, 12 to 22 feet wide and 40 to 100 feet between centers, are driven in a given direction and connected at intervals by crosscuts to provide proper air circulation. These are the major routes of underground transport and access, and serve for the life of the mine. Panel entries are driven from the main entries, resulting in a subdivision of the coalbed into blocks or panels having dimensions that may be as much as 1 by 1/2 mile. Panel entries serve as routes from the main entries to the working places, and for air circulation. Although coal is removed during the driving of the main and panel entries, the production cycle begins upon completion of the panel entries.
Access to coal deposits at a surface operation involves the use of large equipment such as bucket-wheel excavators, draglines, and shovels to remove overburden from the coal so extraction can begin. As mining progresses, development consists mainly of extending paved roads and power lines, and constructing new roads for access to the coal deposit.
Coal Preparation Plant (Coal Beneficiation Plant)
Crushing and cleaning of mine-run coal is commonly referred to as beneficiation or preparation. Often, crushing and sizing is all that is required, but many coal seams, especially those in eastern and midwestern states, contain enough impurities to necessitate further cleaning. Whether the cleaning process is wet or dry, it is commonly referred to as washing. The dry washing method uses high pressure, pulsating airflow to blow dust from the coal. Wet washing starts with breaking and screening the coal to remove the large, hard pieces of impurities. Additional cleaning depends upon the amount, size, and nature of impurity, how it is dispersed in the coal, and how the coal is to be used. Equipment can include any or all of the following: jigs, screens, landers, heavy-medium cyclones, tricone separators, concentrating tables, froth flotation, cells, filters, and driers.
Coal Transport System
The coal transport system will depend on site-specific and project-specific factors and could be a conveyor system within the mine site to the coal preparation plant or a rail system. A system of haul roads is also likely to be present. Transporting coal off-site may be accomplished by rail, truck, barge, or some combination thereof. A coal-slurry pipeline also may be used to send coal off-site.