MODERN INFRASTRUCTURE CONCEPTS IN COAL MINING LARGE DEVELOPMENTS

Transcription

1 MODERN INFRASTRUCTURE CONCEPTS IN COAL MINING LARGE DEVELOPMENTS. Lyonell Fliss Pr Eng (Civil) Lyonell Fliss & Associates (LFA) Coal Mining Developments include in general large Material Handling and Storage facilities and the Civil Engineering Infrastructure for Coal Mining has its specific aspects compared with other sectors of the mining industry. Particularly specific for large coal mines, where large quantities of coal are handled and stored, are large short term containment and storage facilities, used as logistic buffers and long distance overland conveyors, all integrated in the process flow of a mining operation. Coal Mines like those proposed to be developed in the Waterberg Coalfield area will have the capacity to extract large quantities of coal for local power plants and presumably also for export to overseas consumers. Coal supplies to local consumers such power stations can be delivered through rail, road or overland conveyors transportation, individually from each mine, generally situated within a relatively short distance from the consumer. Logistics for these applications are conventional and well known. For export, the large mines are each equipped with rapid rail loading facilities which are designed to load wagon trains directly from each mine (Fig 1). These types of rapid loading facilities, which include also large rail marshalling yards, may not be the most efficient way to export coal from the mines and the case is discussed below... The problem is even more serious with minor coal miners who are not equipped with such expensive facilities and in this case rail loading of full trains takes longer, with negative effects on cost and on the number of wagons required for the railway company.

2 1. The In-Land Coal Terminal Concept The Author proposes for coal export, a new general logistic concept to overcome the export loading problems mentioned above, which will include 3 distinct elements: to be integrated in one Mine to Ocean overall system, covering for any size and number of mines in a given coalfield area : A central In-Land Coal Terminal (ILCT) equipped with a large stockyard and a rapid loading system, which will collect the export coal output of the regional Coalfield (like Waterberg for example) mine cluster.through an overland conveyor reticulation (Fig.2). A dedicated Rapid Rail connecting the In-land with the Ocean Coal Terminal (like RBCT) able to satisfy the Ocean Terminal demand and storage capacity (Fig. 3) An Ocean Terminal for export The Paper is concentrating in describing the concept of the In-Land Coal Terminal portion and its specific infrastructural components, which are all available at present in modern coal mining developments and need only to be adapted and integrated in an optimised coal collection and delivery system. ILCT effects on the Rapid Rail and Ocean Terminal, together with the logistics involved in Mine to Ocean system should be discussed in a separate paper, with the involvement of multidisciplinary specialists. The advantages of the In-Land Coal Terminal concept, compared with the present system of individual rail connection of each mine to the Ocean Terminal, are multiple as from such a system which can be optimised to satisfy the mining production and export demands,will benefit both the major and minor coal miners, the rail company and the export terminal. Without doubt there are expected difficulties to overcome, for acceptance and implementation of the new concept, as the logistic system would differ from the conventional one, requiring a complex co-ordination between the area coal producers. One possibility could be the creation of an independent company, similar to RBCT to run the ILCT. Another possibility may be joint participation of the ILCT users in creation of such a company. Any other co-operation possibilities should also be explored. 2. State of the art of structural components of coal mining infrastructure The characteristic infrastructural components of coal mining industry we are referring to are: Coal Bunkers of large storage capacities.

3 Coal bunkers of large capacities ( T) can be generally used as buffers for the mining operations or as live coal containers for rapid multiple wagons loading in load out stations. Conventionally these structures are of in-situ reinforced concrete construction which for small capacities (up to 5 000t) may be adequate, but for larger capacities it was proved to be uneconomical and difficult to construct. The state of the art alternative is precast concrete construction which not only overcomes the above mentioned problems of conventional in-situ construction, but in addition is superior in quality through usage of high strength (60 Mpa) concrete, more durable (particularly to abrasion) eliminating thus expansive linings. (Fig.4). Precast construction also permits smoother finish to the concrete surfaces in contact with coal, improving thus bunker discharge. A number of large capacity coal bunkers, at present in operation or under construction, proved the above mentioned advantages of precast versus cast insitu construction.it was also confirmed that costs and construction duration per ton capacity decrease with increased bunker size by using precast construction. Overland Coal Conveyors Overland curved conveyors used in large coal mining operations are extending at present to approx. 30km between transfer points but belt conveyor technology may permit to substantially extend this distance. Long overland conveyors can be used for creating transport reticulations covering large coal fields, eliminating or reducing internal road or rail transportation, for coal delivery to users (power stations, industry) or to export in-land terminals. Conveyor equipment (idlers, belts) needs to be supported on structural frames, conventionally consisting of steel construction on heavy gravity type sleepers (Fig.5) Modern alternatives to be considered for their performance and cost advantages are at present available, as follows: a. Precast light sleepers on minipiles (Fig.6). This system instead of using sleepers of large mass for stability is using light precast sleepers on minipiles which provide support for uplift, lateral and overturning. The cost and duration of construction for this system are substantially lower than those for the conventional gravity sleepers and it was proved in a number of applications.

4 b. Precast conveyor frames on minipiles.(fig.7 ) This system is replacing the conveyor steelwork frames with precast frames founded directly on minipiles,sleepers not being required. Using high performance concrete, the framing system is durable, economical and fast to install, requiring minimal maintenance compared with the conventional. Tests on full scale prototypes confirmed the structural reliability of the system. 3. Conclusions New developments in the coal mining industry started to make use of modern infrastructural components including large capacity precast bunkers and precast sleepers on minipiles supports for long distance overland conveyors. Usage of these innovative concepts, leads to better performance, higher durability and constructability in addition to substantial savings as it was proved by working and under construction installations. Usage of conveyor precast framing is still to come into application. Author s intention was make the coal mining industry aware of the availability of the new modern infrastructural elements to be taken into consideration for the future projects. The proposed In-land Coal Terminal concept, as an optimization of the present conventional export railing system, is recommended to be taken into consideration at feasibility stage of any new large coal field development. In planning of an In-land Coal Terminal, provisions (particularly for space) should be made for the predicted future developments. The modern infrastructural elements mentioned above, now available and proved, should positively contribute to the implementation of the in-land Coal terminal concept by making its infrastructure more reliable and economical. Minor miners who are not equipped with large rapid coal loading facilities may benefit from a common In-land Coal Terminal, serving their export needs integrated within a general export logistic system.

5 A brief description of the state of the art of infrastructural elements to be considered as components in an In-Land Coal Terminal scheme, together with results of recent tests performed on full scale prototypes, are presented, to show that technology is ready available to implement the ILCT concept. In Author s opinion, inclusion of an In-Land Terminal (ILCT) in the Master Plan scheme of the development of a large coal field (such Waterberg), should be considered at pre-feasibility study phase, to prove the advantages of this concept..

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12 FIG 7 Paper Title: Modern Infrastructure Concepts for Coal Mining Large Developments Author s Details: Name: Lyonell Fliss Pr Eng (Civil) Organization: Lyonell Fliss & Associates, Industrial Civil Engineering Consultants POB 3929 Edenvale Gauteng Tel Cell lafliss@mweb.co.za