Coal Mining And Production - MIGA

2m ago
209.67 KB
5 Pages
Last View : 17d ago
Last Download : n/a
Upload by : Elise Ammons

Coal Mining and ProductionIndustry Description and PracticesCoal is one of the world's most plentiful energyresources, and its use is likely to quadruple bythe year 2020. Coal occurs in a wide range offorms and qualities. There are two broadcategories: (a) hard coal, which includes cokingcoal (used to produce steel) and otherbituminous and anthracite coals used for steamand power generation; and (b) brown coal (subbituminous and lignite), which is used mostlyas on-site fuel. Coal has a wide range ofmoisture (2-40%), sulfur (0.2-8%), and ashcontent (5-40%). These can affect the value ofthe coal as a fuel and cause environmentalproblems in its use.The depth, thickness, and configuration ofthe coal seams determine the mode ofextraction. Shallow, flat coal deposits are minedby surface processes, which are generally lesscostly (per ton of coal) than underground minesof similar capacity. Strip mining is one of themost economical surface processes. Hereremoval of overburden and coal extractionproceed in parallel strips along the face of thecoal deposit, with the spoil being depositedbehind the operation in the previously minedareas. In open pit mining, thick seams (tens ofmeters) are mined by traditional quarryingtechniques. Underground mining is used fordeep seams. Underground mining methodsvary according to the site conditions, but allinvolve the removal of seams followed by moreor less controlled subsidence of the overlyingstrata.Raw coal may be sold as mined or may beprocessed in a beneficiation/washing plant toremove noncombustible materials (up to 45%reduction in ash content) and inorganic sulfur(up to 25% reduction). Coal beneficiation isbased on wet physical processes such as gravityseparation and flotation. Beneficiation producestwo waste streams: fine materials that aredischarged as a slurry to a tailingsimpoundment, and coarse material (typicallygreater than 0.5 millimeters (mm) that is hauledaway as a solid waste.Waste CharacteristicsKey impacts of surface mining are typicallymassive disturbances of large areas of land andpossible disruption of surface and groundwaterpatterns. In some surface mines, the generationof acid mine drainage (AMD) is a majorproblem. Other significant impacts includefugitive dust and disposal of overburden/wasterock.In underground mines, the surfacedisturbance is less obvious, but the extent ofpossible subsidence can be very large. Methanegeneration and release can also be a problemunder certain geological conditions. Ifgroundwater systems are disturbed, thepossibility of serious pollution from highlysaline or highly acidic water exists. Impacts maycontinue long after mining ceases.The following table presents the levels ofliquid effluents, solid waste, and dust generatedfor the major mining techniques.Beneficiation plants produce large volumesof tailings and solid wastes. Storage andhandling of coal generates dust at rates whichcan be 3 kilograms (kg) per metric ton of coalmined, with the ambient dust concentrationranging from 10 to 300 micrograms per cubicmeter (µg/m3) (above the background level) atthe mine site.341

Coal Mining and Production342Loads Per Unit of Production*ParameterMining TechniquesLiquid effluentsSurface mining(t/1000t coal produced)ContourAreaUnderground mining(t/1000t coal produced)ConventionalLongwall0.241.211.6Solid waste101035Dust0.10.060.0060.01Source: Based on Edgar, 1983* (Note: Local conditions will form the basis for choosing the appropriate mining method)Pollution Prevention and ControlEarly planning and careful design of operationsare the key to minimizing pollution associatedwith mining activities. Specific responsibilitiesshould be assigned for the implementation andmonitoring of environmental measures. Beforemining begins, a mining plan and a mineclosure and restoration plan must be preparedand approved. These plans define the sequenceand nature of extraction operations and detailthe methods to be used in closure andrestoration. These plans should be updatedregularly (every three to five years) as miningprogresses.Development PlanThis plan defines the sequence and nature ofextraction operations and details the methods tobe used in closure and restoration. At aminimum, the plan must address the following:

343 Removal and proper storage of topsoil. Early restoration of worked-out areas andof spoil heaps to minimize the extent of openareas. Diversion and management of surface andgroundwater to minimize water pollutionproblems. Simple treatment to reduce thedischarge of suspended solids may also benecessary. (Treatment of saline groundwatermay be difficult.) Identification and management of areaswith high potential for AMD generation. Minimize the of generation of AMD byreducing disturbed areas and isolating drainagestreams by avoiding contacts with sulfurbearing materials. A water management plan for operationsand post-closure including minimization ofliquid wastes by methods such as recyclingwater from tailings wash plant. Minimization of spillage losses by properdesign and operation of coal transportation andtransfer facilities. Reduction of dust by early revegetationand by good maintenance of roads and workareas. Specific dust suppression measures maybe required for coal handling and loadingfacilities such as minimizing drop distances,covering equipment, and wetting storage piles.Release of dust from crushing and other coalprocessing and beneficiation operations shouldbe controlled. Controlling the release of chemicals(including floatation chemicals) used inbeneficiation processes. Minimization of the effects of subsidenceby careful extraction methods in relation tosurface uses. Control of methane, a greenhouse gas, (toless than one percent by volume) to minimizethe risk of explosion in closed mines. Recovermethane where feasible. When methane contentis above 25 percent by volume, it normallyshould be recovered. Development of suitable restoration andrevegetation methods, appropriate to thespecific site conditions. Proper storage and handling of fuel andchemicals used on-site to avoid spillages.Mine Closure and Restoration PlanCoal Mining and ProductionThe plan should include reclamation of openpits, waste piles, beneficiation tailings,sedimentation basins, and abandoned mine,mill, and camp sites. Mine reclamation plansshould incorporate the following: Return of the land to conditions capable ofsupporting prior land use, equivalent uses, orother environmentally acceptable uses. Use of overburden for backfill and topsoil(or other plant growth medium) forreclamation. Contour slopes to minimize erosion andrunoff. Plant native vegetation to prevent erosionand encourage self-sustaining development of aproductive ecosystem on the reclaimed land. Management of post-closure AMD andbeneficiation tailings. Budget and schedule for pre- and postabandonment reclamation activities.Upon mine closure, all shaft openings andmine adits should be sealed or secured.There is a need to reserve money over thelife of the mine to cover the costs associatedwith mine closure. The amount of money andthe type of financing required will depend on anumber of factors such as the projected life ofthe mine, the nature of the operations, thecomplexity of environmental issues, thefinancial and environmental managementcapacity of the borrower/project sponsor, andthe jurisdiction in which the mine is located.The mine reclamation and closure plan, thetiming of its submission, and its financingshould be discussed and agreed with theborrower/sponsor as early as possible.Target Pollution LoadsImplementation of cleaner production processesand pollution prevention measures can provideboth economic and environmental benefits. Thetarget loads presented in the WasteCharacteristics Section should be used as aguide for pollution prevention purposes. Thefigures relate to each of the productionprocesses before the addition of pollutioncontrol measures.There is a need to reserve money over thelife of the mine to cover the costs associatedwith mine closure. The amount of money andthe type of financing required will depend on a

344number of factors such as the projected life ofthe mine, the nature of the operations, thecomplexity of environmental issues, thefinancial and environmental managementcapacity of the borrower/project sponsor, andthe jurisdiction in which the mine is located.The mine reclamation and closure plan, thetiming of its submission, and its financingshould be discussed and agreed with theborrower/sponsor as early as possible.Emission GuidelinesEmission levels for the design and operation ofeach project must be established through theEnvironmental Assessment (EA) process, basedon country legislation and the PollutionPrevention and Abatement Handbook as applied tolocal conditions. The emission levels selectedmust be justified in the EA and acceptable toMIGA.The following guidelines present emissionlevels normally acceptable to the World BankGroup in making decisions regarding provisionof World Bank Group assistance, includingMIGA guarantees; any deviations from theselevels must be described in the projectdocumentation.The guidelines are expressed asconcentrations to facilitate monitoring. Dilutionof air emissions or effluents to achieve theseguidelines is unacceptable.All of the maximum levels should beachieved for at least 95% of the time that theplant or unit is operating, to be calculated as aproportion of annual operating hours.Coal Mining and ProductionLiquid EffluentsSettling ponds to catch stormwater and toreduce suspended solids should be provided forall effluent before discharge from the site.Where treatment of AMD or other effluentsis required, the following effluent levels shouldbe achieved during operation and after mineclosure.Acid Mine Drainage and Liquid Effluentsfrom Coal MiningParameterpHTotal suspendedsolids*Oil and greaseIronTotal metals6-950103.510* A level of 35 mg/L should be the monthly average.Ambient NoiseNoise abatement measures should achieveeither the following levels or a maximumincrease in background levels of 3 dB(A).Measurements are to be taken at noise receptorslocated outside the project property boundary.Ambient NoiseMaximum Allowable Leq(hourly), in dB(A)Air EmissionsControls may be required on individual sourcessuch as ventilation exhausts if they have asignificant effect on ambient particulate levels.If coal crushers or dryers are used, fabric filtersor other systems should be used to recover coaland reduce particulate emissions to levels below50 milligrams per normal cubic meter(mg/Nm3).Maximum valuemilligrams per liter(mg/L) except for pH)ReceptorDaytimeNighttime07:00 - 22:0022:00 - strial;commercial7070The emission requirements given here can beconsistently achieved by well-designed, well-

345operated and well-maintained pollution controlsystems.Monitoring and ReportingFrequent sampling may be required duringstart-up and upset conditions. All wastewaterdischarges from the operations should bemonitored weekly for pH, total suspendedsolids, and oil and grease. A full analysiscovering iron and other trace metals should becarried out quarterly. Where salinity is apotential problem, appropriate parameters(chloride, total dissolved solids (TDS),conductivity) should be monitored.Ambient air levels of particulate material,including PM10 (particles less than 10 microns insize), in and around mining operations shouldbe measured quarterly. Methane levels shouldbe monitored where appropriate, at leastannually even after mine closure.Monitoring data should be analyzed andreviewed at regular intervals and comparedwith the operating standards so that anynecessary corrective actions can be taken.Records of monitoring results should be kept inan acceptable format. These should be reportedto the responsible authorities and relevantparties, as required, and provided to MIGA ifrequested.Coal Mining and Production Develop and implement a comprehensiveenvironmental and mine management planto include:- Restoration and rehabilitation of disturbed areas.- Minimize land subsidence.- Identification and management of AMD sources.- Water management for operations and post-closureconditions.- Management and sealing of pyrite containing pilesto reduce AMD formation.- Develop and implement a post-closure plan toinclude: Restoration of disturbed areas. Long-term geotechnical and geochemical stabilityof waste piles. Restoration of acceptable long-term surface- andgroundwater flow patterns.Further InformationThe following are suggested as sources ofadditional information (these sources areprovided for guidance and are not intended tobe comprehensive):Edgar, T.F. 1983. Coal Processing and PollutionControl. Houston: Gulf Publishing.Key IssuesHartman, Howard L. (ed.) 1992. SMEEngineering Handbook. 2nd ed., Vol.2. Littleton,Colorado: Society for Mining, Metallurgy, andExploration.The following box summarizes the keyproduction and control practices that will leadto compliance with emission guidelines.World Bank, Environment Department. 1996."Pollution Prevention and Abatement: CoalMining." Technical Background Document.

Coal Mining and Production 342 Loads Per Unit of Production* Parameter Surface mining (t/1000t coal produced) Underground mining (t/1000t coal produced) Mining Techniques Contour Area Conventional Longwall Liquid effluents 0.24 1.2 1 1.6 Solid waste 10 10 3 5 Dust 0.