Vertical transportation system of solid material for backfilling coal mining technology

Intemational Journal of Mining Science and Technology 22(2012)41-45Contents lists available at SciVerse ScienceDirectInternational Journal of Mining Science and TechnologyELSEVIERjournalhomepagewww.elsevier.com/locate/ijmsVertical transportation system of solid material for backfilling coalmining technologyJu feng", Zhang jixiong, Zhang QiangState Key laboratory of Coal Resources G Mine Safery, China University of Mining 6 Technology, Xuzhou 221008, ChinaARTICLE INFOABSTRACTch as waste and fly ash from the surface to the bottom ofhe shaft in a fully mechanized backfiLling coal backfilling coal mining technology, we developed a newrevised form 27 June 201129July2011rtical transportation system to transport this type of solid backfill material. Given the demandsAvailable online 9 March 2012imposed on safely in feeding this material, we also investigated the structure and basic parameter of thisystem. For a mine in the Xingtai mining area the results show that: (1)a vertical transportation systemparts, i.e., a feeding borehole.lly mechanized backfilling coal miningwe determined thatis a suitable diameter for bore holes. the diameter of the storage silo is 6and its height 30 m in this vertical transportation system; ( 3)a conical buffer was developed to absorbTo ensure normal implementation of fully mechanized backfillingcoal mining technology and the safery of underground personnel, we propose a series of security technol-gies for anti-blockage, storage silo cleaning. high pressure air release and aspiration. This vertical trans-porting system has been applied in one this particular mine, which has fed about 4 million tons solidmaterial with a feeding depth of 350 m and safely exploited 3 million tons of coaL.9 2012 Published by Elsevier B.V. on behalf of China University of Mining Technology.According to some estimates, there are about 4.5 billion torwaste rock piled on the ground in China in 1600 comparativelyAs a developing country. China's economy is in a great-leap- large waste rock dumps. Fifteen thousand hectares of land areforward stage of development. Coal, as a primary energy source, occupied and the piled waste is increasing at a rate of 0. 15-0. 20greatly contributes to its national economic development, The billion tons per year (9-11. Furthermore the large number of flyˇm7的) on problem. this problem is particula1211 nce, removing ground wa和 e rock, fly ash and other solidield of coal increases annually which directly leads to coal mining ash emissions from power plants reached 500 million tons duringing early the "three under"(coal mining under buildings, water the last few years and increases annually by 5-7 million tonsIn order to solve this problem, some mining technologies, devel- means to achieve "three under"coal mining in Chin.oped by enterprises and colleges, achieve good results in"threeHow to transport solid material such as waste andunder"mining areas, which temporarily avoids the resource deplthe surface to shaft bottoms in a continuous and efficienon situation for mines, but it does not solve the problem funda- is a key factor in implementing fully mechanized backfmentally. In late 2005, fully mechanized backfilling coal mining mining technology. At the present stage, there are three mitechnology with solid waste appeared, which now has achieved ofndustrial applications successfully with high efficiency and highrecovery[4-71inclined shafts and adits, using conveyor belts ary shafts(1)Existing transportation passages such as auxilFully mechanized backfilling coal mining technology with solidwaste is a revolutionary technology. waste, fly ash and other solidsare the main filling material used to support gob roofs in this back- (2)Taking advantage of power pump coordination with pipe-fill technology ( 8)-lines to supply solid backfilling material(3)Driving a new shaft to undertake the material feeding task.Corresponding author. Tel: +86 13605218330.Tr国煤化工 an additional system inaddress:juf1983@163.com(FJu).existingTHCeNMHG2095-2686/5. see front matter e 2012 Published by Elsevier B.V. on behalf of China University ofdo:101016 just201107004F Ju et al /Intemational Joumal of Mining Science and Technology 22(2012)41-45mining operations, most mines cannot take advantage of theirSurface control roomexisting transportation system to convey backfill material. It is dif-ficult to solve wear and blockage problems and neither is it practi-cal to delivery solid material over long distances in pipelines.Driving a new shaft can transport the material continuously, butit is different from an auxiliary shaft, considering the cost of drivng and shaft maintenance. So developing and investigating anoptimum transportation passage is a key to transport solid backtaterial from the surface to shaft bottoms2. Structure of vertical transportation system for solid materialThe transport of solid material underground through a verticaltransportation system is a continuous process, including surfacetransportation, feeding and a discharge process. while the verticalfeeding bore hole is a channel expected to convey backfill materialonly a complete vertical transportation system can ensure thatother backfilling processes run normally.Fig. 2 structure of feeding bore hoie.2.1. Feeding technologyFor solid materials, the feeding bore hole constitutes the longestdistance of their entire conveying journey from the pile dump toWaste, fly ash and other solid materials originate in general the underground working face. In general, a bore hole is verrom debris depositories and coal preparation [ 14]. In the first in- dug from the surface and the borehole wall is fixed with a layer ofstance, it is these materials that need to be transported to the steel tubing. In order to reduce the wear of the wall caused by fric-mouth of the feeding bore hole.tion with the solid material when it falls down we use tubes as ag When waste, fly ash and other solid materials are conveyed into direct feeding bore hole. This means that the solid material fallsvertical feeding bore hole, several types of material will be down to the underground from the surface in this tube with doubleautomatically mixed, where the feeding ratio of different materials wear-resistant layersand feeding speed will be simultaneously controlled by a controlIn order to construct the storage silo, we installed related equip-system. The solid material falling into the storage silo after being ment and carried out normal monitoring and maintenance work, abuffered near the bottom of the feeding bore hole is then trans- detour is tunneled from the feeding bore hole to a nearby roadwayported to the working face by a conveyor belt after discharging which connects these two drifts.from a feeder under the exit of the feeding bore hole the surfaceThe storage silo is used to store a specific amount of solid mate-transportation system and feeding system will be stopped when rials, on the one hand to ensure material for storage remains in thethe piling height of the mixed material in the storage silo reaches feeding bore hole when the surface transportation system hasits blocking alarm level. this feeding process is shown in Fig. 1stopped; on the other hand it ensures balanced underground trans-The concrete feeding process is as follows: fly ash and other fine port and meets the need for backfilling the working face. We expectgranular solids are directly transported to the feeding mouth from this arrangement will avoid affecting normal coal production.the power plant by a pipeline; waste and other bulk solids aredelivered to the loading hopper with loaders and a conveyor from 2.3. Structure of vertical transportation system for solid materialsthe waste dump, then thrown into the surface surge bin afterscreening and crushing and finally fed into theal feedinghole by a conveyor belt.A complete vertical transportation system should be composeof a production system, a feeding-buffer, a system that guaranteety and aalized control system. The proon system2.2. Structure of vertical feeding bore hole(15-17consists mainly of surface transportation, introduced in the previous section. The feeding-buffer system includes buffers, a shockThe vertical feeding bore hole is the major gateway for trans- absorption beam and a supporting base. the shock absorptionporting solid material. This structure should be suitable for the beam supports the buffer with both ends inserted into the supportfeeding system. Considering that in some situations there still re- ing base left at the body of the ends of the storage silo. The systemains some material to be dropped down when the surface trans- guaranteeing safety includes such components as an anti-blockageportation system has stopped and the balance of the solid material system, a silo cleaning system, a high pressure air release systemis in the underground transportation system, we designed a verti- and an aspirating system. the system not only ensures safe feedingcal feeding bore hole with three parts, i. e, a feeding tube a main- but also simultaneously and effectively prevents storage silo andtenance chamber and a storage silo. Its structure is shown in fig. 2. bore whole blockages〔 Timely closedown)Vertical feeding-Buffering system中国煤化工Dustfall systemCNMHGtemageFig 1. Flow chart of feeding process.F Ju et aL /Intemational Joumal of Mining Science and Technology 22(2012)41-453. Basic parameters of vertical feeding bore holeTable 1Parameters for calculating of storage silos.The system of a vertical feeding bore hole to production in coalItemsDesign parametmining is similar to the intestines in the human body: the selection Time filof suitable parameters not only reduces construction cost andshortens the construction period, but it also ensures normal feed-ing. Major basic parameters include the inner diameter of a feedingbore hole the length of the bore hole, the diameter and depth ofOne day 2.7270604the storage silo.3. 1. Inner didThe size of the bore hole depends on two factors: its madiameter and the required amount of backfill material. In other1088702726words, the speed of surface transportation must match the feedingOne cut 03658215speed. It directly affects the transportation of the backfill materialand leads to blockage if the diameter of the bore hole is too small.17330In contrast, if the diameter is too large it will increase costs andmake the reception difficult for carrying the falling material toof the bore hole is usually more than 3 times larger than the max- be absorbed in the buffering process. Practice has shown that solidimum diameter of backfilling grains.material experiences a"scattering-slipping-deceleration"courseduring the process of direct, frontal impact with the buffer which3.2. Length of feeding bore holeis set at the bottom of the feeding bore hole. Given the reductionin speed, it achieves a reduction in energy consumption and finallyThe length of the feeding bore hole relies on the depth of the buffering.storage silo. In general, once the depth of the storage silo is con-firmedthelengthisobtainedbysubtractingthedepthofthestor-4.2.compoSitionofbuffeage silo from the depth of the coal seam.3.3. Diameter and depth of storage silosigne cording to the magnitude of the force of the impact, we de-signed the buffer in an"umbrella shape", suggesting that the directcontact surface is conical. Hence we called the buffer a conical buf-The diameter and depth of the storage silo should be deter- fer, as shown in Fig 3The main buffer system includes a double shock absorptioined based on actual mine conditions. In general, the size or arched beam, an elastic buffer, an anti-impact wearable alloy, athe storage silo must meet the need of depositing one entire hole combined shock absorber and a buffer director. when freely fallingwith solid material. In order to ensure normal production, the silodown to the upper entrance of the storage silo, the solid materialmust be larger than the volume necessary for the amount of back- impacts the anti-impact wearable alloy set at the bottom of thefill material for one web cut. Table 1 shows the requirements forthe design of storage silos in China.feeding bore hole, causing its velocity and direction to changeGiven the actual condition of Xingtai Mine and the level of techand slip down to the storage silo along its conical surface. Simulta-nology in the construction of storage silos we determined, in the by the" elastic buffer-combined shock absorber-double shockend, that a diameter of 6 m, a height of 30 m and a volume of absorption arch beam"in turn, finally achieving its buffer function.725 m would satisfy the production requirement.It should be noted that the actual underground situation mustSuch a buffer system has been applied in one mine of thebe taken into consideration for determining of size of the storageXingtai mining area since 2008. This mine has backfilled two work-ing panels, mined 3 million tons of coal and deposited about 4 mil-silo. Considering the level of difficulty in construction the detour lion tons of solid material within its buffer system, where theas well as economic factors, it would be appropriate to reduce feeding height is 350 m and the maximum affordable cushioningthe height of the storage silo if there is no available roadway nforce 20 KN5. Security guarantee technology4. Buffering technologyA vertical transportation system is the focus of a4.1. Buffering principlenized backfilling mining system. Complete and reliable securityIn the process of vertical falling into the feeding bore hole, thespeed at which the solid material falls gradually accelerates to aCombined shockuniform motion, causing an enormous impact and leads to thedestruction of equipment and personal injuries if there are no suitarch beamable measures capable of preventing thisTherefore, from an energy point of view, the buffer principle in avertical feeding system is precisely the process required forabsorbing the energy produced by the force of the enormous im-pact, ie by changing the state of movement and reducing theH中国煤化工CNMHGvelocity of the solid material in order to reduce kinetic energy.it is this kinetic energy that is the main energy that needs toFig 3, structure of buffer system.F Ju et al/Intemational Journal of Mining Science and Technology 22(2012)41-45guarantee technology is a precondition to reduce or eliminate inertproduction time and therefore the vertical transportation of a solidmaterial feeding system should include some security guaranteetechnologies such as anti-blockage technology, storage cleaning,high pressure air release technology and aspirating technology5. 1. Anti-blockage technologyAnti-blockage technology is developed mainly to solve theblockage problem in vertical feeding processes [18]. Field practicehas shown that mounting blockage will occur along with the dis3* tubpurge port of fastcharge of solid material from the storage silo where, to somedegree, it will pile up. That is to say, it will not lead to blockage given the condition that the piling height is controlled within a cer-tain range. to ensure a normal feeding flow, there is a need toestablish an anti-blockage system.A level instrument is the core component in this anti-blockagesystem, which is installed at the bottom of the conical buffer. whenthe piling height of the material reaches a dangerous level, this levelinstrument recognizes it and transmits feedback signals to theground control system. Then the ground control system feedbackon the ground transportation equipment achieves closure and stopsfeeding. The feedback signal from the level instrument is transmitted to a square industrial feeding control room via optical fiber com-munication through an auxiliary shaft. In the Xingtai Mine the alarmsignal of the piling height is set at 5 m, with apparently good results.As well, the system needs monitoring facility in the underFlg. 4. Principle of storage silo cleaning technology.ground maintenance chamber, located on the storage silo andarranged for an person, specifically assigned to patrol, at fixed hole, the other end over the barrier of the interior walls and to havetimes. He must carry out closure of the transport equipment and contact with a slot in the roadway or with the pressure emissionstop feeding immediately when informed, from underground, that terminal in the pressure emission chamber. Generally, groundthe feeding system has lost controL.water is used as pressure power of the emission terminal. The highpressure produced from closing the ring of air flow is absorbed by5.2. Storage silo cleaning technology ( 19, 20]this pressure emission terminal.Enforced by circumstances of the storage silo, overstocking and 5.4. Aspirating technologycementation may occur. For the sake of ensuring an expeditiousfeeding flow at the exit of the silo, we must reduce inner wall adhe-Due to the reaction of compressed air in the bore hole, fine parsion from every aspect, but even so, blockage is still an unavoidable ticles of solid material are easily blown into the spaceproblem for backfilling in coal mines which, at times, may affect ground work is carried out. In order to maintain a goodThe size of the bottom exit of the silo for discharging material catch of the feeding bore hole to filter the diry a d in thenormal backfill material quite heavily.environment, industrial vacuum cleaners are installevill reduce the flow due to adhesion on the inner wall. In orderto avoid this situation, we fixed two sets of air guns at the roadway 6 Conclusions and outlookunder the bottom of the silo. the impact of their high pressure flowon the resort area throws a purge of air through the port of its fast 6. 1. Conclusionsheadstock device after the control valve for air flow is openedwhen there is clearly adhesion on the inner wall. This instanta-Aiming at solid material transportation problems from surfaceneous energy produced by high pressure flows cleans the inner to underground in a fully mechanized backfilling coal mining techwall. Its technical principle is shown in Fig. 4.nology, we have analyzed the structure of the vertical feeding system and related security guarantee technologies. Our main53. High pressure air release technologyconclusions are as followsThe air in the vertical feed bore hole is driven and flowing rap(1)The complete vertical transportation of a solid material sysidly along with the movement of the solid material the air flow istem should be composed of a production system, a feedinga rather complex process, for this ring closure air flow engendersbuffer system, a system that guarantees safety and a central-tremendous impact pressure along the direction of the extensionized control system. This vertical feeding to the productionof the feeding shaft. Excessive impact pressure not only destroyssystem in coal mining is comparable to the intestines ofthe device at the bottom of the well, but also seriously threatensthe human body: its structure contains a vertical feedingthe life of mine personnel. The question how to transfer this highbore hole and a storage silo in two parts.pressure air is the premise to ensure normal feeding.(2)Basic parameters of the vertical feeding bore hole deter-In order to achieve high-pressure air emissions effectively, wemines the suitability of the feeding system. It is appropriateconstructed a pressure emission chamber to bypass the pressurethat the innf the uar+ical feeding bore hole isin the storage silo by building a row of interior barrier walls. the486mm中国煤化工 he size of the solidmeans of fixing the pressure emission tunnel with a suitable diam-materialeter is to ensure that one end has contact with the feeding boreenoughCNMHGmm It can supplyolume given that theF Ju et al/ntenanonal Journal of Mining Science and Technology 22(2012)41-45diameter of the storage silo is 6 m and its height 30 m in the Referencesspecific case of Xingtai Mine, cited as our example. The sizeof the storage silo should change according to the actual lll Miao xo Qian MC Researth on green mining of coal resourcondition of a particular mine.(3)Aimed at the force of the impact in the process of material Miao xknins y, coal mining. J China Coal Soc 2010: 35(1): 1-6falling this vertical system, we designed a conical buffer on [3] Guo YC, Yu B, Xu FK. Feasibility analysis of mining coal pillars with stowing inthe buffer principle and applied it in the Xingtai mining area,with a maximum affordable cushioning force of 20kN. 14 Zhang. Miao XX.GUDCLstatus of backfilling technology usingaEng20094395401About 4 million tons of solid material has been successfully [5] Zhang x Miao X MiaIng3, traction coal-pillar mining Chin i Rock uistit fion(4)We have proposed several guaranteed security technologies [6] Miao XX, Zhang jX. Analysis of strata behavior in the process of coalsuch as anti-blockage, storage silo cleaning, high pressure airrelease and aspiration technology which ensures normal I7 Zhang X Miao>ground disposal of waste in coal mine j China Univmplementation of fully mechanized backfilling coal mining [s) Zhang ec sanded coal winning technology and its engineeringMining Techco 2005, 35(2): 197-2u: China University[9] Liu CM, Wang H Creen mining technology of underground refuse disposal.A vertical transportation system is a recent, newly developedeatment and utilization. Mining Saf Eng 2007: 24(2: /3 ys for coal waste[101 Bian ZF, Dan ]. Dong JH, Mu SC, Discussion on rationalmethod for transporting solid material from the surface to under- [11 Deng J. Analysis of waste characteristics and research on comprehensiveground areas, along with the development of fully mechanized (12 Mia0 x. zhang xe. Feng Mw waste-7i2ihg in f9 oackfilling coal mining technology of solid material. This systemhas been successfully applied in most mining areas of China, [13 Deng Ys, Xu S]. Tan J. Tang M, New technology for comprehensive utilization ofthe problems associated with greater vertical depth of the feed sys-[151 Zhang BDesiem still needs more research and studyaf Eng 2009. 203: 3Bs-9 ually-mechanized coal mining technon nf,16Zhang x, Ju F, Huang Yl Zhou Y]. aoFinancial support for this work provided by the National Natu. (171 Ju E study: oh the we tent: 200010027002.9, 209.5.22.mechanized coal winning under buildings. Xuzhou: China Univof the National Natural Science Foundation of China (No. [18/ Zhang B. Study on automatic mosystem for plugging of pipeline50834004)and the innovation Project of Graduate Students ofch2008:296:128-3Jiangsu Province(No CXZZ11-0308) are gratefully acknowledged. (19 Zheng B He MS, Xiao XM. Wang Q Luo z New machine to resolve coal-The authors are also grateful to our postgraduate fellows for 120) Can r.ti Dl. oe ea p veried c. cing from pulverized coal bunker byassisting with field tests, in particular. He Qj, Zan Dongfeng andusing the multi-function high pressure water jet cleaner Coal Prep TechnolTan Fuqing.2003:1:26中国煤化工CNMHG