Use of booster fans in underground coal mining to advantage

第31卷第6期西安科技大学学报Vol 31 No 62011年11月JOURNAL OF XI AN UNIVERSITY OF SCIENCE AND TECHNOLOGYNov 2011Article I:1672-9315(2011)06-0760-06Use of booster fans in underground coal mining to advantageHabibi A Gillies AD SDept. of Mining and Nuclear Engineering, University of Missouri Science and Technology, Rolla MO 65409-0450, USA)Abstract a booster fan is an underground main fan which is installed in series with a main surface fanand used to boost the air pressure of the ventilation to overcome mine resistance. Currently booster fansare used in several major coal mining countries including the United Kingdom, australia, Poland andChina. In the United States booster fans are prohibited in coal mines although they are used in severalmetal and non-metal mines. a study has been undertaken to examine alternatives for ventilatan un-derground room and pillar coal mine system. A feasibility study of a hypothetical situation has shownthat current ventilation facilities are incapable of fulfilling mine air requirements in the future due to in-creased seam methane levels. A current ventilation network model has been prepared and projected to amine five years plan. Ventsim visual"software simulations of different possible ventilation options havebeen conducted in which varying methane levels are found at working faces. The software can also un-dertake financial simulations and project present value total costs for the options under study. Severalscenarios for improving the ventilation situation such as improving main surface fans, adding intakeshafts, adding exhaust shafts and utilizing booster fans have been examined. After taking into accountthe total capital and operating costs for the five years mine plan the booster fan scenarios are recommen-ded as being the best altematives for further serious consideration by the mine. The optimum option is aproperly sized and installed booster fan system that can be used to create safe work conditions, maintainadequate air quantity with lowest cost, generate a reduction in energy consumption and decrease minesystem air leakageKey words: booster fan; mine ventilation; optimization design; ventsim simulationCLC number. TD 72Document A0 IntroductionBooster fans are technically main fans which are installed underground to maintain required airflow by over-coming the mine resistance. In United States the use of booster fans is permitted in metal and nonmetal mineshowever legislation prohibits their use in underground coal mines with the exception of anthracite mines( Title 30Code of Federal Regulations 2010). The demand for fresh air at working faces leads engineers to design or up-grade the existing ventilation system( Wempen and others, 2011). Booster fans can reduce the pressure of themain fan and decrease the system leakage and total required air power( Martikainen et al 2010). The objectiveis to find the optimum method for ventilating an underground US coal mine. The optimal ventilationdesidetermine the best combination of fans and regulators that will fulfill the airflow requirements in themine and minimize the operating cost( Calizaya and McPherson 1987). Both booster fans and regulators are used中国煤化工Received date. 2011-08-15CNMHGFundation item: Supported by National Institute for Occupational Safety and Health( NIOSH)of USA(200-2009-30328)Corresponding author Habibi A, Professor, Rolla, Mo, Tel 001-(573 )303-6011, E-mail: xx 5@ mail. mst.edu第6期Habibi A, et al: Use of booster fans in underground coal mining to advantage761to control air distribution throughout the mine network. Regulators destroy energy initially put into the mineflow control through use of booster fans will be more efficient than use of regulators' balance point of view air-ventilation system by fans ) while booster fans add energy to the system; from an energyThe paper presents a number of different scenarios by simulating the ventilation network ofnderground coal mine. Different approaches examined have involved improvements to the main surface fans, addingintake, or exhaust shafts or adding booster fans to the system. a current ventilation network model of a hypothet-ical mine has been prepared and projected to a mine five years plan. Seven "Ventsim Visual"software simulations of different possible ventilation options have been conducted. The project was initiated by expanding themodel from the current workings to the mine's five years production plan. Airflow and contaminant simulationhave been undertaken. In addition a cost study has determined the uneconomic and impractical scenarios in re-gard to power consumption. Scenarios 4 and 6 can meet the required face airflows however after taking into ac-count total cost and expected life of the new infrastructure scenario 6 with the use of two booster fans is recom-mended as being the best altermative in the five year plan1 General information on the mineThis underground coal mine uses the room and pillar method. The coal seam is horizontal with thickness of1.8 m. Development mains are driven with eleven entries( four intakes, four returns and three neutral airways)Sub-mains are driven with two intakes, two returns and three neutral airwaysCurrently the mine has five active working faces ventilated by a 670 kw axial fan using a pull system. Themine currently exhausts 230 m' /s of air at static pressure of 1. 95 kPa. The input power of 460 kW is requiredA pressure and air quantity survey has been conducted to construct the base ventilation model. Working Units 1and 3 dump retum air to Main West Return, Unit 2and 4 dump air to Main East Returm. Unit 5"dumps air toMain North Return. Main East Return and Main West Return then dump air to Main North Return which goes toaust upcastingshaftStudy assumptionsThe original five year plan and seven different altemative hypothetical scenarios have been simulated to determine the optimal option which offers the lowest total cost( capital cost plus operating cost )as well as providesrequired airflows at working faces. In this hypothetical exercise higher coal seam methane contents (either Im3CH,t or 2mCH,/t)are presumed to be being encountered in extraction in five years. Options examined look atcases where more ventilation is made available underground from alternatives of1)The driving of more intake or return shafts2) The use of various surface main fan combinations3)The use of various booster fan combinationsFinancial simulation modeling estimates optimum ventilation infrastructure size by considering mining costsas well as life of mine ventilation operating costs 2). These simulations can, for instance, help to optimize airwaysizes and save substantial money over the life of a mine. This approach optimizes the size of the development airways to maximize cost savings in ventilation while minimizing mining costs. Increasing airway size is the easiestway to reduce frictional pressure losses and decrease ventilation costs in a mine. However it causes additionalmining capital costs and this is further exacerbated by "time value of money"considerations. Operating costs include electricity, maintenance and installation charges over five years中国煤化工resent valueAnother factor to consider is how long the airway is required to carryMethane dilution calculations have been undertaken. These are basCNMImum oI 1, m /g of fresh airbeing required at each of the working faces762西安科技大学学报2011年The Safe Scenario: A liberation rate of 2.0 mCH, /t from broken coal. The mining rate of 345 th(265moal/h)at density 1.3 tm has been used. An airflow rate of greater than 15 m'/s is deemed to be required togive CH, concentrations of less than 1. 0% in face air. The steady state contaminant simulation has been per-formed based on the requirement of an allowable concentration of methane at each individual working face. Thespread of methane concentrations in downstream airways is identified.The Very Safe Scenario: A liberation rate of 1.0 mCH,/t from broken coal. The mining rate of 345 th(265 m'coal/h)at density 1.3 t/ has been maintained. The airflow rate of greater than 15 m/s is deemed toe required to give CH, concentrations of less than 0. 5% in face air. The simulation has been performed byadding 0. 5% methane to each individual faces and tracking the spread of the contaminant. The results show theconcentrations of the methane in the network which emphasizes that the predicted concentration in all networkairways is lower than 0. 5%3 Simulation alternatives3. 1 Scenario oneThe simulation has been conducted based on the expanded model and current ventilation infrastructure forthe next five years. Measured resistance values for standard mine airways were used in the projected modelTab 1 Scenario 1 predicted airflows on working faces Tab. 2 Scenario 2 predicted airflows on working facesAir quantitiesExhaust ShaftExhaust shaft206.1take Shaft73.0Intake Shaft121.438.1Intake Shaft 2Unit 213.4Unit 2Unit 37.9Unit 3Unit 4"15.013.2Input Power/kW813.4Operating Cost/s693270712511It was determined that unit 1and are the furthest distant sections and so due to airways resistance available airflow at their working faces is less than the minimum required. Unit #4 also does not have the minimum required airflow also. From these tests it is concluded that current surface fan infrastructure is not capable of ventilating the mine in 5 years. Table 1 shows the simulation results. Scenarios 2 to 7 are based on ventilation changes from this expanded five years plan model3.2 Scenario twoThis scenario has an intake shaft added in 1"Main East. The simulation adjusts the flow through the airwaThe quired airflow. The schematic view of the shaft and the simulation results can be found in table 2abased on the resistance of each airway size. The required shaft diameter can be determined from the mining ceThe main fan operates at static pressure of 2. 2 kPa and exhausts 206. I m/s of air The total quantity ofthe air has not increased but an improved air distribution at the east part of the mine has been fulfilledFinancial Simulation estimates optimum ventilation infrastructure size by considering mining costs as well aslife of mine ventilation operating costs. This simulation can help opti中国煤化工over the life of a mine. The study has optimized the size of the shaft deyIze cost sav-CNMHGings in ventilation, while minimizing mining costs. Increasing airway sizw Iduce inctonapressure losses and decrease ventilation costs in a mine. However it creates additional mining cost and this is fur-第6期Habibi A, et al: Use of booster fans in underground coal mining to advantage763ther exacerbated by the "time value of money? which dictates that a dollar saved in mining costs now is worthmore than a dollar saved in ventilation costs in the future. Thus it was found that the optimum diameter of the in-3.3 Scenario 3Two intake shafts were added to the model in order to supply the 4133 Individual Fan Static PresuireCurvee360required air at faces. Intake shaft 1"has been added to 1"Main East E2480and Intake shaft 2 added to 2d Main West. The total exhausted air 2 653827quantity has not been increased. An optimized diameter of 3. 6m hasbeen selected based on the lowest excavation cost. Table 3 shows the58116174232290quntity/(mredicted resultsFig. 1 Stalled fans characteristicsThis scenario almost meets the minimum requirements for all u-curve and operating pointnits, however the required air quantity at unit 3 which is the furthestface has not been reached. Moreover the shaft excavation operation is a time and cost consuming exercise whichcauses this scenario to have a high capital cost.Tab 3 Scenario 3 predicted airflows on working faces Tab. 4 Scenario 4 predicted airflows on working faces/sExhaust ShaftExhaust Shaft165.4Intake Shaft260.1Intake Shaft 274.5Intake Shaft*Intake Shaft 359.9174Unit I'18.31516.0nput Power/kW811Input Power/kW1624.3710407erating Cost/多14202793. 4 Scenario 4Exhaust Shaft 2has been added to 1"Main East Retum. A fan similar to the main fan added to the networkand the optimal diameter of 4. 2 is selected.The simulation results show in Table 4 that this altermative fulfills the air requirements at working faces.However the operating cost has increased dramatically. The capital cost has also increased since sinking a permanent ventilation shaft and purchasing and installing a second surface fan is expensive3. 5 Scenario 5A second surface exhaust fan 2(similar to a Jeffery 8HUA-96 Axial Vane )has been added in parallelThe air simulation ran but with warning "the lack of airflow rate causes the fans to be stalled".One of fan is exhausting 123. I m/s at static pressure of 3. 3 kPa and the later is exhausting 129 9 m/s at the same static pres-sure. The operating points drops off the curve( Fig. 1). The network efficiency is estimated 57.4%.This sce-nario does not meet the requirements at working faces.Although in this scenario two surface fans are working in parallel the total amount of exhausted air has nothigh resistance which occurs because of distance to the workings anda crease. An explanation for this is thesignificantly changed. Base on the fan laws, total air quantity should ind3.6 Scenario 6中国煤化工neter.CNMHGSince the current surface main fan alone is physically incapable offans have been added to the network to add air pressure to overcome resistance. booster fans could be installed764西安科技大学学报2011年in the main airways or in a split off the main airways. Booster fan I"has been added to the I"Main East Returnand Booster fan 2"to 2"Main West Return. Figs 2 and 3 show the fan characteristics curves. ThisscenarIomeets the required airflow at working faces with relatively low additional capital cost. Table 6 shows the simulation resultsFan installation may require the development of a bypass drift, widening of an existing drift, installation ofairlock doors, and miscellaneous civil constructions. The next task is fan testing and commissioning. Testing in-olves checking the fan for stability, and running it first at no load with the airlock doors open and then at fullload with the doors closed( Calizaya, Stephens and Gillies 2010)Tab. 5 Scenario 5 predicted airflows on working faces Tab. 6 Scenario 6 predicted airflows on working facesAir quantitiesAir quantitiesExhaust Shaft253.0Exhaust Shaft104.4Intake Shaft162.0Intake Shaft148,691.0Intake Shaft 2Intake Shaft 177.1Intake Shaft 329.9Intake Shaft 255.3Unit 1"Lnit 2Unit 2Unit 3Unit 3Unit 4Unit 413.Unit 514.81402.4Input Power/kW915.71228476Operating Cost/s802120Combined Fan Static PCombined Fan Static Pressure22982980919283747566574849309192837475665748493Fig 2 Booster fan characteristicsFig 3 Booster fan 2 characteristicscurve, 2 main westIinn inappropriate booster fan selection or installation Tab. 7 Scenario 7 predicted airflows on working facesoduces potential hazards including an increasem/slikelihood of recirculation. Addition of bulkheads andExhaust Shaft208.2changing regulators downstream of the booster fans mayIntake Shaft130.6Booster fancontrol air distribution. Most changes need to be done122.0in 2nd Main west. 1s Main East and the intersection ofMain north Vs 2 MUnit 3.3. 7 Scenario 7One booster fan was added to Main North Returnto increase air pressure and reduced overall powerInput Power/kW977.8costs. Although capital cost is lower than some otherOperating Cost/856578scenarios, the booster fan could not meet the required airflow at the we中国煤化工n exhausts 177m/s at static pressure 0. 61 kPa with 68 efficiency as shown in TahCNMHG第6期Habibi A, et al: Use of booster fans in underground coal mining to advantage7654 Contaminant SimulationThe seven scenarios show that with addition of either 1% or 0. 5% methane to each working face the average of methane across all five faces examined, and consequently throughout the mine network, is respectivelyless than these figures. This is because the simulation optimizes for one critical face minimum quantity and con-sequently other faces receive more than the minimum air, a situation that is rarely a problem. The CH4concen-tration has been diluted through leakage as air travels past leaking air control devices5 ConclusionThe current ventilation model of the mine was projected to the mine five years plan. A feasibility review hasbeen completed of altermatives available to improve workings ventilation as production moves into seams withhigher methane contents. The scenarios examined alternatives that utilize additional infrastructure such as mainventilation shafts and fans or underground booster fans. Based on the five year plan model, unit #1 and #3 arethe furthest sections in the main west area from the current intake and return shafts and maintaining airflow tothem will be difficult unless additional infrastructure is installed. The following is a review of the research on thevarious scenario simulationsTab. 8 Contaminant and airflow simulation resultsAverage CH, levelModelCapital Cost·/多 Total Cost/多15 Years Plan with Current Approach 0.63205.46932702 One Intake shaft added0.61210.6356421546835539843193Two Intake Shafts added0.710.36350069515809346587884 One Exhaust Shaft added0.33361.97030455173105087619655 Double Exhaust Fans Added 0.67621319062000068336 Add Two Booster Fans Altemative 0. 65204.34875095Add one Booster Fan217.042828704648575Note: 'The steady state contaminant simulation has been performed based on the requirement of an allowable concentration of methane at each individ-ual working face to identify the path and spread concentration of methane from contaminant sourcecost: present value of electricity, maintenance and installation costs over 5 years discounted at 10%Capital Cost: Excavating and fan purchasing charges included.1)Scenario 1 expanded the network with the current infrastructure for the next five years and it was deter-mined that due to distance and airway resistance available airflow at working faces is less than the minimum re-quired2)Intake shaft 2has been added to the 1"Main East. Although this alternative maintains the required air-flow for Units 2and Unit 4. the lack of airflow at other faces is obvious3)Intake shafts 2"and 3 were added to 1"Main East and 2m Main West. The exhausted airflow increasedbut the airflow on two faces is marginal. There are drawbacks4)All airflow from working faces needs to travel a long distance in return airways to be exhausted throughthe single main fan5)Mining areas may have a relatively short life before the additional shafts'locations are by passed or areo longer in useful positions.6)Scenario 4 fulfills the airflow requirements at working faces but7)A second exhaust fan has been added to the current surface infraYH中国煤化工CNMHG第775页)第6期任森:防治矿井热害的人工制冷方案分析77543-46[6]欧晓英,杨胜强,于宝海,等矿井热环境评价及其应用[J].中国矿业大学学报,2005,34(3):323-326OU Xiao-ying, YANG Sheng-qiang, YU Bao-hai, et al. Evaluation of thermal environment in mine and its application [ J]Joumal of China University of Mining& Technology, 2005, 34 (3): 323-326[7]鞠金峰施喜书,王晓关于高温矿井热害防治的思考[J能源技术与管理,200,(3):80-96.JU Jin-feng, SHI Xi-shu, WANG Xiao. The thoughts about Heat harm control in high temperature mines[ J]. Energy Techand Management, 2009, (3): 80-96Analysis of the cooling systems for preventing mine heat hazardsREN SenSchool of Mining Engineering, Inner Mongolia University of Science and Technology, Baotou 014010, ChinaAbstract: This article, through analyzing heat dissipating capacity of each heat source, studies themain sources of heat in mines and the effect of heating-up, and evaluates the parameters of the idealcooling system and economic indicators by thermodynamics and heat transfer theory and method. By an-alyzing and comparing the characteristics of the actual cooling cycles, the economic efficiency of the various cooling devices, we propose that air compression refrigeration cycle be used to avoid unnecessarywastage of inputs and create conditions for enterprises to reduce production costsKey words: convection heat transfer; heat radiation; ideal cooling cycle; heat receptivity.Correspondingauthor:RenSen,Lecturer,Baotou014010,P.R.ChinaTel:0086-13029552070,E-mail:rensen132@163.com(上接第765页)The required airflow has not been achieved; moreover the shaft could not handle the increased airflow whichcaused the second fan to stall8)Two booster fans were modeled in 1"Main East Retum and 2 Main West Return innario 6 meets required face airflows and total cost is a little more than $5 million9)A single booster fan has been added in series in Main North Return in Scenario 7. The airflow on the twThe conclusion to the study is scenarios 4 and 6 can meet required face airflows. However scenario 4 has atotal Present Worth cost of almost $9 million. Scenario 6 meets required face airflows and total cost is a littlemore than 35 million. For this reason Scenario 6 is recommended as being the best alternative for further seriousconsideration to meet the mine ventilation requirements in the five year plan6 AcknowledgementThis paper was prepared with financial support from National Institute for Occupational Safety and HealthResearch Center. This support is gratefully acknowledged. In addition the support efforts of mine personnel arehighly appreciated参考文献 References[1] Martikainen A L, Taylor C D. Breaking the ice on the booster fan dilemma in US underground coal mines[ J]. Mining Engi-needing,2010,62(10):47-5中国煤化工[2 Kissell F N, Timko R J. Pressurization of intake escapeway with parachuteCNMH Gof smoke[CJ//Wang Y J. Proceedings of the 5 th U.S. Mine Ventilation Symposium. Colorado: Littleton, 1991