Article Comprehensive Technical Support for High-Quality Anthracite Production: A Case Study in the Xinqiao Coal Mine, Yongxia Mining Area, China

Wei Zhang 1,2, Dongsheng Zhang 3,*, Hongzhi Wang 3 and Jixin Cheng 3

Received: 14 September 2015; Accepted: 8 December 2015; Published: 14 December 2015 Academic Editor: Saiied Aminossadati

1 IoT Perception Mine Research Center, China University of Mining & Technology, Xuzhou 221008, China; [email protected] 2 The National and Local Joint Engineering Laboratory of Internet Application Technology on Mine, China University of Mining & Technology, Xuzhou 221008, China 3 School of Mines, China University of Mining & Technology, Xuzhou 221116, China; [email protected] (H.W.); [email protected] (J.C.) * Correspondence: [email protected]; Tel./Fax: +86-516-8359-0501

Abstract: The effective production of high-quality anthracite has attracted increasing global attention. Based on the coal occurrence in Yongxia Mining Area and mining conditions of a coalface in Xinqiao Coal Mine, we proposed a systematic study on the technical support for the production of high-quality anthracite. Six key steps were explored, including coal falling at the coalface, transport, underground bunker storage, main shaft hoisting, coal preparation on the ground, and railway wagon loading. The study resulted in optimized running parameters for the shearers, and the rotating patterns of the shearer drums was altered (one-way cutting was employed). Mining height and roof supporting intensity were reduced. Besides, loose presplitting millisecond blasting and mechanized mining were applied to upgrade the coal quantity and the lump coal production rate. Additionally, the coalface end transloading, coalface crush, transport systems, underground storage, and main shaft skip unloading processes were improved, and fragmentation-prevention techniques were used in the washing and railway wagon loading processes. As a result, the lump coal production rate was maintained at a high level and fragmentation was significantly reduced. Because of using the parameters and techniques determined in this research, high-quality coal production and increased profits were achieved. The research results could provide theoretical guidance and methodology for other anthracite production bases.

Keywords: coal mining; high-quality anthracite; lump coal production rate; fragmentation-prevention; mining optimization

1. Introduction As one of six approved domestic anthracite production bases, Yongxia Mining Area (YMA) of Henan Province in China has an intended capacity of 10 million tons yearly. The quantity of anthracite is about 20% of all coal produced, but contributes 45% of total coal income. Despite the poor performance of the coal market over the past three years, anthracite sales have not been plagued with overstocking and sluggish demand. Therefore, it is significant to provide a series of customized technical supports for producing high-quality anthracite. The Lump coal production rate (LCPR) is a key index of anthracite’s quality. Among the various factors affecting the LCPR, physical properties and occurrence conditions of the coal seam are the most important ones [1–3]. The LCPR of anthracite has been intensively studied over the past few

Minerals 2015, 5, 919–935; doi:10.3390/min5040533 www.mdpi.com/journal/minerals Minerals 2015, 5, 919–935 decades and various reports have been published, all of which can be categorized into the following five aspects: (1) Reformations of shearer drums [4–8]. Since 1972, attempts have been made to increase the LCPR by enlarging the chipping areas of cutting picks, optimizing their arrangements and improving drum parts in Poland, Russia and China. (2) Improvements in blasting methods [9–13]. The Cardox blasting technique (CBT) has been widely applied to increase LCPR in Turkey and Colombia. Also, based on the controlled blasting principle, loose control blasting, uncoupled water medium millisecond blasting, and high-pressure gas millisecond blasting have been developed to improve the blasting effect. (3) Adjustments in mining techniques. Zhao et al. [14] proposed a method that combines the blasting mining workface and fully mechanized workface to achieve enhanced LCPR. Song et al. [15] proposed a technique involving low cutting depth and fast traction two-way cutting using an AM-500 Shearer (TMM Group, Taiyuan, China), and achieved to enhance LCPR from raw coal. Zhang et al. [16] introduced a coal planer (DBT Company, Lünen, Germany) used in the mining of thin coal seam with a thickness of 1 m. The LCPR was increased using effective mining of workface obviously. (4) Optimizations of transport and storage. Li et al. [17] reported a stretchable mini-sized bin to mitigate the high drop damage on coal in the bunker. As a result, lump coal losses were reduced by 6%. Kozan et al. [18] proposed a demand-responsive decision support system by integrating the operations of coal shipment, coal stockpiles and coal railing within a whole system. A generic and flexible scheduling optimization method is developed to identify, represent, model, solve and analyze the coal transport problem in a standard and convenient way. Zhang et al. [19] reported the air-supported membrane shed as a new building structure for storing coal. Wang et al. [20] reported wave-like coal drops with horizontally attached transloading points and spiral coal drops with vertically attached transloading points based on the in situ analysis of underground conditions. As a result, the fragmentation of mined anthracite was reduced. Lv et al. [21] introduced a massive vertical bunker on-wall buffer system with a unique structure and fixing patterns. Compared with conventional column coal drops placed in the bunker center, this buffer system effectively prevented coal from fragmenting during its dropping process, thus lessening lump coal loss. Liu et al. [22] reported an innovative methodology for optimizing the coal train scheduling problem. To construct feasible train schedules, an innovative constructive algorithm called the SLEK algorithm is proposed. To optimise the train schedule, a three-stage hybrid algorithm called the SLEK-BIH-TS algorithm is developed based on the definition of a sophisticated neighbourhood structure under the mechanism of the Best-Insertion-Heuristic algorithm and Tabu Search metaheuristic algorithm. Singh et al. [23] described a MILP (Mixed Integer Linear Programming) model for determining the capacity requirements, and the most cost effective capacity improvement initiatives, to meet demand while minimizing the total cost of infrastructure and demurrage. Then, they presented results of computational experiments on the model’s performance along with a comparison of the model’s output with detailed analyses from the coal chain analysts and planners. (5) Innovations in coal preparation plants. Wang et al. [24] reported that an ultrasonic wave sensor was placed on top of the lump coal buffer bunker, and the work site was equipped with coal level alarms. The dropping height was maintained between 2–3.8 m, and in this way, both the LCPR and safety were enhanced. Xie et al. [25] introduced a sizing crusher (FP5012, ZGME Company, Zhengzhou, China) was used to increase the size uniformity of crushed particles and decrease the over-crushing rate. Chen et al. [26] introduced attempts made to adjust the unloading opening size, optimize the separating density, and perform separate storage of filtrated coal. As a result, the LCPR of anthracite has been increased by 4.5%. In summary, despite great achievements made in producing high-quality anthracite, previous reports focus on only one key step, and few attempts have been made to investigate the entire production process in an integrated way. As we know, underground mining in itself is a complicated process, which is easily affected by several determining factors (e.g., geological conditions, mining

920 Minerals 2015, 5, 919–935 techniques, and production systems). Therefore, a significant improvement in the quality of mined Minerals 2015, 5, page–page anthracite is a systematic undertaking that can only be achieved by modifications in all relevant productionthe quality links. of In mined other words,anthracite overall is a productsystematic quality undertaking is determined that can by only the poorestbe achieved performance by of individualmodifications processes in all relevant (Cannikin production Law). Basedlinks. In on other the words, occurrence overall of product the coal quality seam is in determined YMA and the miningby the conditions poorest performance of a coalface of inindividual Xinqiao processe Coal Mines (Cannikin (XCM), Law). we proposedBased on the a systematicoccurrence of study the on the technicalcoal seam supports in YMA forand thethe productionmining conditions of high-quality of a coalface anthracite in Xinqiao in thisCoal paperMine (the(XCM), remaining we sectionsproposed includes a systematic mine conditions study on andthe technical mining techniques,supports for techniquesthe production for of increased high-quality LCPR anthracite of raw coal, fragmentation-preventionin this paper (the remaining techniques sections for includes lump coal, mine and conditions economic and benefits). mining techniques, It should techniques be pointed out for increased LCPR of raw coal, fragmentation-prevention techniques for lump coal, and economic that the proposed coal mining methods are only used for underground mining. The results of this benefits). It should be pointed out that the proposed coal mining methods are only used for studyunderground have been widely mining. adopted The results for high-quality of this stud anthracitey have been production widely adopted in other coalfor high-quality mines, YMA. anthracite production in other coal mines, YMA. 2. Mine Conditions and Mining Techniques As2. Mine shown Conditions in Figure and1, XCM Mining is locatedTechniques in the southwest part of Yongcheng City, Henan Province, ˝ 1 11 ˝ 1 11 ˝ 1 11 ˝ 1 11 China. ItsAs terrestrial shown in coordinates Figure 1, areXCM 116 is 13located34 –116 in 18the07 southwestEast longitudes, part of 33Yongcheng47 21 –33 City,53 58 NorthHenan latitudes. Province, With aChina. length Its of terrestrial 14 km (North coordinates to South) are and 116°1334 a width″–116°18 of 1.6–4′07″ km East (East longitudes, to West), the mine33°47 has a′21 total″–33°53 area′58 of″ 36North km2 .latitudes. As one ofWith the largesta length coal of mines14 km managed(North to by South) Yongcheng and a Coalwidth & of Power Company1.6–4 km Limited (East (YCPLC),to West), the XCM mine has has been a total designed area of with 36 km a capacity2. As one ofof 1.2the millionlargest coal tons mines each year and amanaged service lifeby Yongcheng of 56.6 years. Coal A & pair Power of shaftsCompany was Limi establishedted (YCPLC), in a uni-verticalXCM has been up designed and down with pattern a capacity of 1.2 million tons each year and a service life of 56.6 years. A pair of shafts was established and with a horizontal elevation of ´550 m. Mining is executed in a bottom up fashion; the bottom in a uni-vertical up and down pattern and with a horizontal elevation of −550 m. Mining is executed coal seam (#22) is mined before mining the top coal seam. In addition, horizontal mining occurs in in a bottom up fashion; the bottom coal seam (#22) is mined before mining the top coal seam. In a forwardaddition, pattern. horizontal mining occurs in a forward pattern.

Figure 1. The geographical location of XCM. Figure 1. The geographical location of XCM.

The #22 coal seam of the North Second Panel (NSP) was mined first. The generalized column of Thethe NSP #22 coalis presented seam of in the Figure North 2. The Second geological Panel st (NSP)ructure was and minedoccurrence first. conditions The generalized of this field column are of the NSPfavorable is presented for mining; in Figure the coal2. seam The geological thickness ranges structure from and 1.69 occurrenceto 4.34 m and conditions the average of thickness this field are favorableis 3.33 for m. mining; The dip theangle coal ranges seam from thickness 10° to 16° ranges and the from average 1.69 toangle 4.34 is m 13°. and The the roof average of the #2 thickness2 coal is seam is made up of fine sandstone and˝ sandy˝ mudstone, with magmatic rock˝ in some local regions. 3.33 m. The dip angle ranges from 10 to 16 and the average angle is 13 . The roof of the #22 coal seamThe is made base of up the of #2 fine2 coal sandstone seam is andmade sandy up of mudstone,mudstone and with siltstone. magmatic In this rock area, in somestrike locallongwall regions. fully mechanized mining (FMM) (mining height is equal to 2.85 m) and roof caving (for mined-out The base of the #2 coal seam is made up of mudstone and siltstone. In this area, strike longwall fully areas) were employed.2 mechanized mining (FMM) (mining height is equal to 2.85 m) and roof caving (for mined-out areas) were employed. 3

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Number Lithology Thickness Remarks

1 Siltstone 8.26 m / Number Lithology Thickness Remarks 2 Fine sandstone 8.61 m Main roof 1 Siltstone 8.26 m / 3 Sandy mudstone 0.22 m Immediate roof 2 Fine sandstone 8.61 m Main roof 4 Coal 3.33 m #22coal seam 3 Sandy mudstone 0.22 m Immediate roof 5 Mudstone 2.85 m Immediate floor

4 Coal 3.33 m #22coal seam 6 Siltstone 9.46 m Main floor 5 Mudstone 2.85 m Immediate floor

6 Siltstone 9.46 m Main floor

Figure 2. The generalized column of the NSP. Figure 2. The generalized column of the NSP.

3. Techniques for Increased LCPR of Raw Coal 3. Techniques for Increased LCPRFigure of 2. Raw The generalized Coal column of the NSP. In coal mining, the LCPR is positively related to the unit price of the product and decrease of Inpulverized3. Techniques coal mining, coal for rate. the Increased Mostly, LCPR rawLCPR is positively coal of miningRaw Coal related is th e key to the stage unit of lump price coal of the formation. product Moreover, and decrease the of pulverizedparametersIn coalcoal (running rate.mining, Mostly, theparameters LCPR raw is coal andpositively miningdrum parameterelated is the keytors) the of stage unitthe shearer ofprice lump of and the coal the product formation. mining and methods decrease Moreover, play of the parametersapulverized key role (running in coal the rate.formation parameters Mostly, of rawlump and coal coal. drum mining parameters) is the key stage of the of shearerlump coal and formation. the mining Moreover, methods the play a keyparameters role in the (running formation parameters of lump and coal. drum parameters) of the shearer and the mining methods play 3.1. Optimization of Shearer’s Parameters a key role in the formation of lump coal. 3.1. Optimization of Shearer’s Parameters 3.1.1. Mathematical Description of Shearer’s Cutting Thickness 3.1. Optimization of Shearer’s Parameters 3.1.1. MathematicalThe cutting Descriptionthickness of a of shearer Shearer’s refers Cutting to the thickness Thickness cut by each pick in one rotation of the drum.3.1.1. Mathematical This parameter Description is not an intrinsicof Shearer’s one; Cutting instead, Thickness it is a condition parameter that is determined The cutting thickness of a shearer refers to the thickness cut by each pick in one rotation of the by the arrangement of cutting picks, the rotating speed of the drum, and traction speed of the drum. ThisThe parameter cutting thickness is not anof a intrinsic shearer refers one; instead,to the thickness it is a conditioncut by each parameter pick in one thatrotation is determined of the shearer [27,28]. Due to the effects of the drum rotation and shearer traction used for this study, by thedrum. arrangement This parameter of cutting is not an picks, intrinsic the one; rotating instead, speed it is a ofcondition the drum, parameter and tractionthat is determined speed of the arc-shapeby the arrangement cutting was of generated cutting picks,and the the cutting rotating shape speed was ofa crescent the drum, [29] and(Figure traction 3). speed of the shearer [27,28]. Due to the effects of the drum rotation and shearer traction used for this study, shearer [27,28]. Due to the effects of the drum rotation and shearer traction used for this study, arc-shape cutting was generated and the cutting shape was a crescent [29] (Figure3). arc-shape cutting was generated and the cutting shape was an crescentc [29] (Figure 3).

vq nc D vq hmax O D hmax O

Figure 3. The ranges of drum cutting thickness.

The cutting thickness along the traction direction in one rotation can be expressed as [30]: Figure 3. The ranges of drum cutting thickness. Figure 3. The ranges of drum1000v cutting thickness. = q The cutting thickness along the tractionh maxdirection in one rotation can be expressed as [30]: (1) z1nc The cutting thickness along the traction direction1000 inv one rotation can be expressed as [30]: =2 q hmax= (1) h hzmaxn (2) π10001 cvq hmax “ (1) 42 z1nc h = h π max (2) 2 h “ 4 hmax (2) π

922 Minerals 2015, 5, 919–935

where: vq is the traction speed of the shearer, m/min; z1 is the number of picks in a transversal Minerals 2015, 5, page–page (determined by the picks arrangement and the number of helical blades); nc is the rotating speed of the drum, r/min; hmax and h are the maximum and minimum cutting thickness, respectively. where: vq is the traction speed of the shearer, m/min; z1 is the number of picks in a transversal According(determined to by Equations the picks arrangement (1) and (2),cutting and thethickness number of is helical also determined blades); nc is by the the rotating picks speed arrangement of and the number of helical blades. the drum, r/min; hmax and h are the maximum and minimum cutting thickness, respectively. According to Equations (1) and (2), cutting thickness is also determined by the picks 3.1.2. Optimization of Running Parameters arrangement and the number of helical blades. According to the relationship between traction/rotating speeds and cutting thickness, the ratio of 3.1.2. Optimization of Running Parameters traction speed and rotating speed must be optimized to improve the LCPR. For instance, the traction speed/rotatingAccording speed to the ratio relationship is decreased between for hardtraction/rotating coal while speeds increased and forcutting soft thickness, coal. Previous the ratio studies haveof revealed traction speed that tractionand rotating speed/rotating speed must be speedoptimized ratio to shouldimprove bethe kept LCPR. within For instance, 0.0762–0.1524 the traction [31 ,32]. The parametersspeed/rotating of speed the double-drumratio is decreased shearers for hard (MG200/500-QWD, coal while increased for TST soft Company, coal. Previous Beijing, studies China) have revealed that traction speed/rotating speed ratio should be kept within 0.0762–0.1524 [31,32]. currently used in XCM are as follows: traction speed is 0–6 m/min, drum diameter is 1600 mm, cutting The parameters of the double-drum shearers (MG200/500-QWD, TST Company, Beijing, China) depth is 630 mm, and designed drum rotating speed is 42 r/min. With consideration to the situation in currently used in XCM are as follows: traction speed is 0–6 m/min, drum diameter is 1600 mm, this study,cutting traction depth is and 630 rotatingmm, and speeds design wereed drum adjusted rotating to speed 4–5 m/min is 42 r/ andmin. 35With r/min, consideration respectively, to the so that the ratiosituation remained in this at study, 0.11–0.14. traction As aand result, rotating the LCPRspeeds was were enhanced adjusted byto 3.8%.4–5 m/min and 35 r/min, respectively, so that the ratio remained at 0.11–0.14. As a result, the LCPR was enhanced by 3.8%. 3.1.3. Optimization of Cutting Pick Parameters In3.1.3. theory, Optimization the LCPR of Cutting can be enhancedPick Parameters by either increasing the pick length or decreasing the pick density. Nevertheless,In theory, the bothLCPR measures can be enhanced lead to increasingby either increasing shearer vibrations,the pick leng thusth or lessening decreasing the the service life ofpick the density. shearer. Nevertheless, To counter this, both a measures novel shearer lead to drum increasing with unique shearer picks vibrations, (Figure thus4) was lessening used inthe XCM. As shownservice in life Figure of the4a, shearer. the cutting To counter blades this, presented a novel large shearer cutting drum depth with unique and digging picks (Figure capabilities. 4) was Each drumused had in three XCM. blades As shown and each in Figure transversal 4a, the cutting had three blades cutting presented picks; large the distances cutting depth between and digging transversals capabilities. Each drum had three blades and each transversal had three cutting picks; the distances could be 100, 122, 142, or 162 mm. The cutting cross-section of kerfs is shown in Figure4b. Herein, between transversals could be 100, 122, 142, or 162 mm. The cutting cross-section of kerfs is shown in A –A ,B –B , and C –C sketch the cross-sections of picks No. 1 to No. 4 on the blades. 1 Figure4 1 4b.4 Herein, 1A1–A4 4, B1–B4, and C1–C4 sketch the cross-sections of picks No. 1 to No. 4 on the blades.

1 1

4

2

5 C4 C3

Direction of rotation C C 2 1 B B 4 B 3 B 2 1 6 A4 A3 A2 A1 C C 4 C 3 C 2 3 1 B4 B3 B2 B1 A4 A3 A2 A1 100 122 142 162 100 122 142 162 (a) (b)

Figure 4. A novel shearer drum with large cutting depth and digging capabilities: (a) arrangement Figure 4. A novel shearer drum with large cutting depth and digging capabilities: (a) arrangement of cutting picks on blades; (b) cutting cross-section of kerfs; 1, transversals; 2, cutting picks; 3, blades; of cutting picks on blades; (b) cutting cross-section of kerfs; 1, transversals; 2, cutting picks; 3, blades; 4, anthracite; 5, kerfs; 6, cracks. 4, anthracite; 5, kerfs; 6, cracks. 5

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The 18 cutting picks on the plate were maintained, while the picks on the blade were reduced fromThe six 18to cuttingfour. Three picks oncutting the plate picks were were maintained, installed whileon each the transversal picks on the and blade the were inter-transversal reduced from sixdistance to four. was Three increased cutting from picks 80 were to 162 installed mm. onTo eachmitigate transversal the increased and the cutting inter-transversal resistance, distance a more waspowerful increased drum from (Kennametal 80 to 162 mm. Company, To mitigate Fort the increased Mill, SC, cutting USA) resistance, was employed. a more powerful Meanwhile, drum (Kennametalhigh-strength Company,point-attack Fort picks Mill, (U92 SC, USA)and U94) was employed.were used Meanwhile,in different high-strengthsituations: extended point-attack U92 picks (U92(from and 92 to U94) 125 were mm) used were in used different for completed situations: cutting extended cases, U92 and picks U94 (from picks 92 were to 125 used mm) for were coal usedseams for with completed small structures. cutting cases, Since and then, U94 compared picks were to used the production for coal seams using with conventional small structures. drums, Since the then,LCPR compared was enhanced to the by production 5.1%. using conventional drums, the LCPR was enhanced by 5.1%.

3.2. Allocation of Reasonable Mining Techniques

3.2.1. Selection of Rotating Direction of the Drums and CuttingCutting ApproachApproach To improve improve the the stability stability of the of shearer, the shearer, the two the drums two rotated drums in rotated opposite in directions opposite (front/rear directions (front/rearequals clockwise/anti-clockwise equals clockwise/anti-clockwise or anti-clockwise/c or anti-clockwise/clockwise,lockwise, as shown in Figure as shown 5). Therefore, in Figure 5the). Therefore,cutting resistances the cutting on resistancesthe different on drums the different worked drums in opposite worked directions. in opposite Usually, directions. a clockwise/ Usually, aanti-clockwise clockwise/anti-clockwise pattern was patternemployed. was employed.This can be This attributed can be attributedto the fact to that the factthe thatspecific the specificpower powerconsumption consumption was minimized was minimized when the when front the and front rear and drums rear drums were wereresponsible responsible for cutting for cutting and andloading, loading, respectively. respectively. Additionally, Additionally, the thefloating floating dust dust was was also also reduced. Nevertheless, thethe anti-clockwise/clockwise pattern pattern was was used used in inXCM. XCM. In Inthis this case, case, the thefragmentation fragmentation of lump of lump coal coalwas wasreduced reduced by 4.9%, by 4.9%, as loading as loading of both of both drums drums did not did involve not involve the rocker the rocker arm. arm.

1

2

Advance direction

3

Figure 5. Clockwise/anti-clockwise or anti-clockwise/clockwise patterns of front and rear drums: Figure 5. Clockwise/anti-clockwise or anti-clockwise/clockwise patterns of front and rear drums: 1, front drum; 2, rear drum; 3, rocker arm. 1, front drum; 2, rear drum; 3, rocker arm.

Currently, two-way and one-way cutting approaches are both widely used in the mining industry.Currently, Theoretically, two-way andtwo-way one-way cutting cutting approa approachesches are are bothmore widely effective used than in the one-way mining industry.cutting. Theoretically,However, two-way two-way approaches cutting approaches are limited are by more various effective issues than in one-waypractice. cutting.For instance, However, the height two-way of approachesthe shearer body are limited is limited by variousby the thickness issues in practice.of the coal For seam, instance, and low the underneath height of the clearance shearer bodymay be is limitedmet. The by maximum the thickness underneath of the coal clea seam,rance and of the low shearer underneath was 468 clearance mm in may this bestudy, met. and The coal maximum cut by underneaththe front drum clearance would of accumulate the shearer at was the 468 front mm end in thisof the study, shearer and in coal front-rear cut by the cutting, front drumwhich would could accumulateresult in undesired at the front fragmentation. end of the shearer On the in ot front-rearher hand, cutting, one-way which cutting could approaches result in undesired showed fragmentation.reasonable efficiency, On the otherand the hand, LCPR one-way could cutting be enhanced approaches by using showed this reasonable method. efficiency,Therefore, andin this the LCPRstudy, coulda rear-front be enhanced one-way by using cutting this approach method. Therefore,was used inand this the study, coal a rear-frontwas kept one-wayaway from cutting the approachbracket. Using was used one-way and the cutting coal wasapproach, kept away the NSP from has the an bracket. average Using yield one-way of 100,000 cutting tons approach, each month, the NSPwith hasthe anhighest average monthly yield ofyield 100,000 of 180,000 tons each tons. month, with the highest monthly yield of 180,000 tons. 3.2.2. Reduction of Mining Height and Roof Supporting Intensity 3.2.2. Reduction of Mining Height and Roof Supporting Intensity In cases of strong coal walls and roof, mining height and roof supporting intensity would be In cases of strong coal walls and roof, mining height and roof supporting intensity would be reduced accordingly to allow spontaneous caving of the top coal upon cutting (Figure6). In this reduced accordingly to allow spontaneous caving of the top coal upon cutting (Figure 6). In this way, massive coal cubes can be gained at a relatively low drum rotating speed. At the same time, way, massive coal cubes can be gained at a relatively low drum rotating speed. At the same time, cutting resistance on the unit area is lessened. Mining height of the NSP was designed to 2.85 m cutting resistance on the unit area is lessened. Mining height of the NSP was designed to 2.85 m and and a dual-column shield hydraulic support (ZY4000/17.5/38, ZMJ Company, Zhengzhou, China, a dual-column shield hydraulic support (ZY4000/17.5/38, ZMJ Company, Zhengzhou, China, supporting height is 1.75–3.8 m and initial support is 3077 kN) was used. For practical purposes, the 9246 Minerals 2015, 5, 919–935

Minerals 2015, 5, page–page supporting height is 1.75–3.8 m and initial support is 3077 kN) was used. For practical purposes, the mining height was was reduced from from 2.85 to 2.80 m, and the initial support was lowered from 3077 to 2800 kN. As a result, the LCPR was enhanced by 3.7%.

Figure 6. SchematicSchematic illustration illustration of the coalface mining process.

3.2.3. Implementation of LPMB on Coal Mass 3.2.3. Implementation of LPMB on Coal Mass In mining, many specific situations arise. For instance, some mines are located in geological In mining, many specific situations arise. For instance, some mines are located in geological crack zones, while others have issues of parting bands. Without additional measures, the LCPR of crack zones, while others have issues of parting bands. Without additional measures, the LCPR of the the product could be extremely low. Previous studies reported positive effects on the LCPR using product could be extremely low. Previous studies reported positive effects on the LCPR using blasting. blasting. In accordance with that, LPMB was executed on the coal body based on the variation of In accordance with that, LPMB was executed on the coal body based on the variation of the coal seam the coal seam thickness. More specifically, a loose blast was conducted once a day so that the thickness. More specifically, a loose blast was conducted once a day so that the presplitting depth met presplitting depth met the need during working progress. Blasting was carried out while mine the need during working progress. Blasting was carried out while mine maintenance was conducted. maintenance was conducted. In situ measurements revealed that the LCPR was increased by 12.37% In situ measurements revealed that the LCPR was increased by 12.37% (Table1) with LPMB and FMM. (Table 1) with LPMB and FMM. Table 1. LCPR comparison of two different mining techniques. Table 1. LCPR comparison of two different mining techniques.

MiningMining Technique Technique Total Total Output Output (t) (t) Lump Lump Quantity Quantity (t) (t) LCPR LCPR (%) (%) Cutting Cutting Way Way 1st:1st: 390 390 186.5 186.5 47.82 47.82 LPMBLPMB + +FMM FMM 2nd:2nd: 390 390 174.3 174.3 44.69 44.69 Average:Average: 46.4746.47 One-way One-way 3rd:3rd: 390 390 182.9 182.9 46.90 46.90 1st:1st: 390 390 134.5 134.5 34.49 34.49 Average: 34.10 One-way FMMFMM 2nd:2nd: 390 390 131.9 131.9 33.82 33.82 Average: 34.10 One-way 3rd: 390 132.6 34.00 3rd: 390 132.6 34.00

4. Fragmentation-Prevention Fragmentation-Prevention Techniques Techniques for for Lump Lump Coal Coal As itit willwill undergo undergo long long transport transport routes routes (including (including coalface coalface end transloading, end transloading, transport transport through throughheadgate, headgate, panel, and panel, main and roadway), main roadway), lump coal lump mined coal from mined the from coalface the bycoalface the shearer by the is shearer stored inis storedan underground in an underground bunker and bunker hoisted and to the hoisted surface. to Raw the coalsurface. will beRaw also coal washed will be and also sieved washed in a series and sievedof processes in a series that involveof processes repetitive that squeezing,involve repeti collidingtive squeezing, and abrading colliding (as well and as abrading secondary (as crushing well as secondaryof massive crushing cubes), which of massive results cubes), in reduction which ofresults LCPR. in Indeed,reduction a large of LCPR. amount Indeed, of coal a large is pulverized amount ofinto coal powder, is pulverized causing ainto severe powder, decline causing in the quality a severe of anthracite. decline in In the this quality section, of we anthracite. proposed aIn study this section,of fragmentation-prevention we proposed a study techniques of fragmentation-prevention for lump coal in view techniques of the whole for lump coal flow coal system. in view of the whole coal flow system. 4.1. Principles of Coal Fragmentation 4.1. PrinciplesFragmentation of Coal Fragmentation refers to the process in which large lumps are crushed into smaller ones. The collision of coal cubes against one another is believed to be the main cause of fragmentation [33,34]. Fragmentation refers to the process in which large lumps are crushed into smaller ones. The It is generally believed that the LCPR of the final product is positively related to the percentage of large collision of coal cubes against one another is believed to be the main cause of fragmentation [33,34]. It is generally believed that the LCPR of the final product is positively related to the percentage of large lumps in the raw coal. However, the LCPR925 of the final product is also affected by various reasons from the transport and transloading systems. Particularly, collision is regarded as a main 7 Minerals 2015, 5, 919–935 lumps in the raw coal. However, the LCPR of the final product is also affected by various reasons from the transportMinerals 2015 and, 5, page–page transloading systems. Particularly, collision is regarded as a main reason for the LCPRreason of the for final the product. LCPR of Despite the final the limitedproduct. understandingDespite the limited of lump understanding coal fragmentation of lump principles, coal the collisionsfragmentation can be principles, generally the described collisions by can the followingbe generally equation described (Momentum by the following Theorem) equation [35]: (Momentum Theorem) [35]: mpvt ´ voq F “ − (3) m(vtt vo ) F = (3) t where: F is the force experienced by the cube during collisions; m is the mass of the cube; t is the where: F is the force experienced by the cube during collisions; m is the mass of the cube; t is the collision time; vo and vt are the velocities before (vo “ 2gh) and after collisions, respectively. collision time; v and v are the velocities before ( v = 2gh ) and after collisions, respectively. According to Equationo t (3), the collision forceo experienceda by the lumps is determined by the collision timeAccordingt, lump to massEquationm, and(3), velocitiesthe collision before force andexperienced after collisions by the lumps (vo and is vdeterminedt). In most by cases, the vt is negligible,collision as time lumps t, lump after mass collision m, and are velocities static. According before and to after classical collisions physics, ( vo andvo isvt positively). In most cases, related to the falling height (vo “ 2gh). As the inner surface (made of concrete) of bunker is rigid, the collision vt is negligible, as lumps after collision are static. According to classical physics, vo is positively time is extremely short. As a result, the collision force is large and the lumps are easily fragmented. related to the falling aheight ( v = 2gh ). As the inner surface (made of concrete) of bunker is rigid, Additionally, the force on each lumpo increases with its mass. Therefore, the LCPR is reduced as the averagethe collision lump mass time increases. is extremely short. As a result, the collision force is large and the lumps are easily fragmented. Additionally, the force on each lump increases with its mass. Therefore, the LCPR is 4.2. Reconstructionsreduced as the average of Coalface lump End mass Transloading increases.

Because4.2. Reconstructions of the large of Coalface height End difference Transloading (1.2–1.5 m) between the transloader end and the extensible belt conveyer, lumps falling from the transloader gain a large amount of speed causing violent collisions Because of the large height difference (1.2–1.5 m) between the transloader end and the betweenextensible the lumps belt conveyer, and the conveyerlumps falling surface. from Asthe atransloader result, the gain overall a large LCPR amount is reduced of speed in causing this process. To solveviolent this, collisions an additional between buffer the lumps unit wasand the installed convey ater thesurface. transloader As a result exit, the to lessenoverall theLCPR collisions is betweenreduced the lumpsin this process. and the To conveyer, solve this, so an as additional to reduce buffer lump unit fragmentation was installed by at 4.7%. the transloader exit Theto lessen basic the configurations collisions between of the the lumps buffer and unit the conveyer, are shown so as in to Figure reduce7 lump. As fragmentation viewed, the by buffer 4.7%. unit mainly consistsThe basic of sideconfigurations protecting of plate the buffer components unit are (Figureshown 8in) andFigure buffer 7. As axis viewed, components the buffer (Figure unit 9). Symmetricalmainly consists side protecting of side protec platesting were plate attached components to the (Figure spill plates 8) and at thebuffer sides axis of components the transloader. Components(Figure 9). of Symmetrical the side protecting side protecting plate plates included were a attached fixed flange to the beam, spill plates fixed at side the protectingsides of the plate, transloader. Components of the side protecting plate included a fixed flange beam, fixed side movable side protecting plate, fixed bolt, connection plate, and damper. The components of the buffer protecting plate, movable side protecting plate, fixed bolt, connection plate, and damper. The axis included a buffer axis, connection plate, buffer chain, and split ring. components of the buffer axis included a buffer axis, connection plate, buffer chain, and split ring.

9 6 5 4 7 1

2

3 8

10

Figure 7. Basic configuration of the buffer unit: 1, fixed flange beam; 2, fixed side protecting plate; Figure 7. Basic configuration of the buffer unit: 1, fixed flange beam; 2, fixed side protecting plate; 3, movable side protecting plate; 4, buffer axis; 5, guide slot; 6, buffer chain; 7, fixed bolt; 3, movable side protecting plate; 4, buffer axis; 5, guide slot; 6, buffer chain; 7, fixed bolt; 8, connection 8, connection plate; 9, damper; 10, extensible belt conveyor. plate; 9, damper; 10, extensible belt conveyor. 8

926 Minerals 2015, 5, 919–935 Minerals 2015, 5, page–page

1 7 Minerals 2015, 5, page–page 5 9 1 7 5 9 2

2

8

8 3

3

(a) (b) (a) (b) FigureFigure 8. 8. SchematicSchematic illustration illustration of of a a side side protecting protecting plate plate:: (a (a) )front front view view;; ( (bb)) side side view view.. Figure 8. Schematic illustration of a side protecting plate: (a) front view; (b) side view. 4 4

6 6

(a(a)) (b(b) )

Figure 9. Schematic illustration of a buffer axis: (a) front view; (b) side view. FigureFigure 9. 9. SchematicSchematic illustration illustration of of a a buffer buffer axis axis:: (a (a) )front front view; view; (b (b) )side side view view..

TheThe buffer buffer axis axis and and chains chains were were placed placed at at thethe exitexit of the transloader to to set set up up a asemi-confined semi-confined The buffer axis and chains were placed at the exit of the transloader to set up a semi-confined spacespace with with the the side side protecting protecting plates. plates. As As a a result, result, thethe lumpslumps were convconvergederged in in the the center center part part of o thef the space with the side protecting plates. As a result, the lumps were converged in the center part of conveyerconveyer belt belt and and decelerated, decelerated, which which result result in in reduced reduced collisionscollisions withwith thethe conveyer conveyer belt. belt In. In case case of of a a the conveyer belt and decelerated, which result in reduced collisions with the conveyer belt. In case suddensudden increase increase in inimpact impactss on on the the buffer buffer axis, axis, itit movemovedd upwards alongalong thethe guide guide grooves grooves on on the the offixed a sudden side protecting increase in plates impacts to avoid on the severe buffer damage axis, it movedto the unit’s upwards components. along the Once guide the grooves impacts on fixed side protecting plates to avoid severe damage to the unit’s components. Once the impacts thewere fixed balanced side protecting by gravity, plates the buffer to avoid axis severe stayed damage in place. toUnlike the unit’s buffer components. teeth, the buffer Once axis the actively impacts were balanced by gravity, the buffer axis stayed in place. Unlike buffer teeth, the buffer axis actively wereresponded balanced to byvarying gravity, impacts the buffer and the axis lump stayed speeds in place. were Unlikekept without buffer severe teeth, damage the buffer to axisthe buffer actively responded to varying impacts and the lump speeds were kept without severe damage to the buffer respondedunit. A fixed to varying protecting impacts plate and and movable the lump protecting speeds were plate kept replaced without the transloader severe damage folding to plate the buffer so unit. A fixed protecting plate and movable protecting plate replaced the transloader folding plate so unit.that A the fixed plate protecting length could plate be and adjusted movable according protecting to variations plate replaced in the roadway the transloader floor. folding plate so that the plate length could be adjusted according to variations in the roadway floor. that the plate length could be adjusted according to variations in the roadway floor. 4.3. Applications of Wheel Crusher 4.3. Applications of Wheel Crusher 4.3. ApplicationsIn practical of Wheelsituations, Crusher large anthracite lumps mined from the coalface are pulverized by a In practical situations, large anthracite lumps mined from the coalface are pulverized by a coalfaceIn practical crusher situations, connected large to anthracitethe transloader. lumps minedIn this from process, the coalfaceconvention are pulverizedal crushers by(e.g., a coalface jaw coalface crusher connected to the transloader. In this process, conventional crushers (e.g., jaw crushercrushers connected and hammer to the crushers) transloader. rely on In compressive this process, forces conventional to crush the crushers lumps. (e.g., Nevertheless, jaw crushers cracks and crushers and hammer crushers) rely on compressive forces to crush the lumps. Nevertheless, cracks hammerare formed crushers) in the rely lumps on compressive as the loading forces area to crushof lumps the lumps.is large. Nevertheless, Meanwhile, their cracks mechanical are formed are formed in the lumps as the loading area of lumps is large. Meanwhile, their mechanical instrengths the lumps degrade as the loadingafter compression. area of lumps As a is result large., the Meanwhile, lumps become their mechanicalextremely small strengths and may degrade be strengthspulverized degrade into powderafter compression. in consecutive As processes,a result, theand lumps then reduce become the extremely LCPR of thesmall anthracite. and may To be pulverized into powder in consecutive processes, and then reduce the LCPR of the anthracite. To 9279 9 Minerals 2015, 5, 919–935 after compression. As a result, the lumps become extremely small and may be pulverized into powder in consecutiveMinerals 2015, processes,5, page–page and then reduce the LCPR of the anthracite. To avoid it, a Wheel Crusher (PLM 1000, ZMJ Company, Zhengzhou, China) that works well with the coalface end transloader is avoid it, a Wheel Crusher (PLM 1000, ZMJ Company, Zhengzhou, China) that works well with the applied in XCM. coalface end transloader is applied in XCM. SpecificallySpecifically designed designed for for domestic domestic coal coal mines,mines, this this wheel wheel crusher crusher consists consists of a of pulley, a pulley, crushing crushing chamber,chamber, unloading unloading chamber, chamber, crushing crushing axis axis components, components, and and dust dust curtains curtains (Figure (Figure 10)[ 10)36 ].[36]. The The crusher Minerals 2015, 5, page–page is connectedcrusher is to connected the transloader to the attransloader both ends at by both connection ends by holes.connection An additionalholes. An additional joint is designed joint is at its loadingdesigned endavoid so atit, thatitsa Wheel loading a rigid Crusher end connection so (PLM that 1000, a rigid between ZMJ conne Company, thection crusher between Zhengzhou, and the the crusherChina) transloader that and works the couldtransloader well with be established. the could Conventionally,be established.coalface end transloader coal shows is applied an average in XCM. lump size below 100 mm after crushing, with 84% having a diameterConventionally, noSpecifically larger than designed coal 100 shows mmfor domestic andan average 30% coal being mines, lump ofthis size fine wheel below grade. crusher 100 As consistsmm a result after of ofacrushing, pulley, crushing, crushing with the 84% overall LCPRhaving is reducedchamber, a diameter byunloading 5%. no By larger chamber, using than the crushing 100 wheel mm axis crusherand components, 30% proposed being ofand fine in dust this grade. curtains study, As a the(Figure result LCPR of10) crushing, loss[36]. wasThe reducedthe overallcrusher LCPR is connectedis reduced to by the 5%. transloader By using atthe both wheel ends crusher by connection proposed holes. in this An study,additional the jointLCPR is loss by only 2%. According to market surveys and customer feedback, this was achieved by optimizing the wasdesigned reduced at by its only loading 2%. end According so that a rigidto market conne ctionsurveys between and thecustomer crusher feedback, and the transloader this was couldachieved gear and crusher exit diameter (200–400 mm). by optimizingbe established. the gear and crusher exit diameter (200–400 mm). Conventionally, coal shows an average lump size below 100 mm after crushing, with 84% having a diameter no larger than 100 mm and 30% being of fine grade. As a result of crushing, the overall LCPR is reduced by 5%. By using the wheel crusher proposed in this study, the LCPR loss was reduced by only 2%. According to market surveys and customer feedback, this was achieved by optimizing the gear and crusher exit diameter (200–400 mm).

(a) (b)

Figure 10. PLM 1000 Wheel Crusher: (a) left front view; (b) right front view. Figure 10. PLM 1000 Wheel Crusher: (a) left front view; (b) right front view. 4.4. Adjustments in Transport(a) Systems (b) 4.4. Adjustments in Transport Systems Before being Figurestored 10. in PLM underground 1000 Wheel Crusher: bunkers, (a) left crushed front view; raw (b ) coalright frontis transported view. over a long Beforedistance being and storedtransloaded in underground several times. bunkers, Because crushed of the rawlong coal transport is transported distance overand athe long height distance 4.4. Adjustments in Transport Systems and transloadeddifferences in severaloverlapping times. sections, Because the lumps of the fall long a large transport distance distance at transloading and the points, height resulting differences in overlappingin lump Beforefragmentation sections, being stored theand lumpsreducedin underground fall LCPR. a large Thebunkers, LCPR distance crushed loss at eachraw transloading coaltransloading is transported points, point overis resulting estimated a long in to lump distance and transloaded several times. Because of the long transport distance and the height fragmentationbe 0.5%. To and mitigate reduced this LCPR. loss, the The following LCPR loss adjustments at each transloading were made pointto optimize is estimated the transport to be 0.5%. systems:differences (1) The in overlappingroadway layout sections, was the improved lumps fall soa large that distance the number at transloading of transloading points, resultingpoints and To mitigate this loss, the following adjustments were made to optimize the transport systems: (1) The heightin lump differences fragmentation was lessened; and reduced (2) theLCPR. height The LCPRof overlapping loss at each sections transloading of transloading point is estimated points to was roadway layout was improved so that the number of transloading points and height differences was reducedbe 0.5%. so thatTo mitigatethe falling this heights loss, the of followingthe lumps ad wojustmentsuld be lesswere than made 0.5 to m; optimize (3) the thesteel transport wire mesh systems: (1) The roadway layout was improved so that the number of transloading points and lessened;and flakes (2) the were height replaced of overlapping with a buffer sections device at of transloading transloading points points (Figure was 11). reduced so that the falling heights ofheight the lumpsdifferences would was lessened; be less than (2) the 0.5 height m; (3) of theoverlapping steel wire sections mesh of and transloading flakes were points replaced was with reduced so that the falling heights of the lumps would be less than 0.5 m; (3) the steel wire mesh a buffer device at transloading points (Figure 11). and flakes were replaced with a buffer device at transloading points (Figure 11).

(a) (b)

Figure(a) 11. Buffer device: (a) rubber belt; (b) impact(b idler.)

Figure 11. Buffer device: (a) rubber belt; (b) impact idler. Figure 11. Buffer device: (a) rubber belt; (b) impact idler. 10 10 928 Minerals 2015, 5, 919–935page–page

4.5. Optimizations of Underground Storage 4.5. Optimizations of Underground Storage As a key component of the coal production system, underground bunkers show significantly varyingAs astock key levels, component resulting of the in coalunpredictable production falling system, heights underground of the lumps. bunkers Collisions show in significantly the falling varyingprocess caused stock levels, great resultinglosses of lumps. in unpredictable Statistics revealed falling heights that the of losses the lumps. of LCPR Collisions in this process in the falling were processas high causedas 6%–12% great [37,38]. losses ofTherefore, lumps. Statistics it was esse revealedntial and that urgent the losses to reduce of LCPR the in lump this process coal loss were by asimproving high as 6%–12%the design [37 of,38 underground]. Therefore, bunkers. it was essential and urgent to reduce the lump coal loss by improvingDesigned the designbunker of height underground of XCM bunkers.was 28 m, which exceeded the optimized value for bunker bottomDesigned protection bunker and lump height preservation. of XCM was To 28 mitigate m, which this exceeded issue, spiral the bunkers optimized are value sometimes for bunker used. bottomHowever, protection because andconstruction lump preservation. and maintenance To mitigate of spiral this issue,bunkers spiral require bunkers significantly are sometimes increasing used. However,costs and time, because a novel construction bunker anddesign maintenance was proposed of spiral. Specifically, bunkers requirethe cross-section significantly of the increasing bunker costswas designed and time, to a novelbe circular bunker and design permanently was proposed. supported Specifically, with theanchor cross-section rod/anchor of themesh/concrete bunker was designed(concrete tosupport be circular thickness and permanently is 0.4 m). Hanging supported spiral with chutes anchor were rod/anchor installed mesh/concrete on the outside (concrete wall of supportthe bunker thickness and the is junctions 0.4 m). Hanging of these chutes spiral chuteswere pr wereocessed installed to strengthen on the outside its resistance wall of to the corrosion, bunker andrust, theand junctions wear. As of a theseresult, chutes the final were speed processed of the tolumps strengthen was reduced its resistance and their to corrosion, collisions rust,with andthe wear.bunker As were a result, lessened, the finalindicating speed that of the the lumps LCPR was was reduced enhanced and and their damages collisions to the with bunker the bunker were werereduced. lessened, Additionally, indicating bunker that blockings the LCPR were was enhancedalso lessened. and Practical damages applications to the bunker revealed were reduced. that the Additionally,LCPR of bunkers bunker equipped blockings with were spiral also chutes lessened. increased Practical by 30%. applications revealed that the LCPR of bunkersThe equippedapplication with of hanging spiral chutes spiral increased chutes had by 30%.a significant effect on the LCPR. However, in the coal Thedumping application process, of hangingit is difficult spiral for chutes operators had a to significant make reasonable effect on thedecisions LCPR. based However, purely in theon coalvisual dumping observations, process, resulting it is difficult in over-dumping. for operators toAs make a result, reasonable the LCPR decisions is reduced based to purely a higher on extent visual observations,than expected resultingin this process. in over-dumping. To mitigate this As is asue, result, a stock the LCPR level monitoring is reduced tosystem a higher (Figure extent 12) thanwas expectedinstalled at in the this bunker process. opening To mitigate to promote this issue, the du amping stock level process. monitoring In this way, system both (Figure underground 12) was installedand ground at the operators bunker openingcan accurately to promote control the the dumping bunker process. level. Additionally, In this way, both an alarm underground is triggered and groundonce the operators stock level can is accurately below a controlprescribed the bunkervalue (1 level.7 m in Additionally, this case) so an that alarm over-dumping is triggered once would the stockbe prevented. level is below a prescribed value (17 m in this case) so that over-dumping would be prevented.

(a) (b)

Figure 12. Bunker stock level monitoring system: (a) bunker opening; (b) sensor layout. Figure 12. Bunker stock level monitoring system: (a) bunker opening; (b) sensor layout.

4.6. Improvements to the Main Shaft Skip Unloading Processes 4.6. Improvements to the Main Shaft Skip Unloading Processes The main shaft is regarded as the core of a coal mine production system. In large and The main shaft is regarded as the core of a coal mine production system. In large and medium-sized mines, coal lifting is carried out at the main shaft with a skip. The raw coal is then medium-sized mines, coal lifting is carried out at the main shaft with a skip. The raw coal is then lifted to the ground by the shaft skip and transloaded to the conveyer on the ground. Because of lifted to the ground by the shaft skip and transloaded to the conveyer on the ground. Because of production rate needs, transloading rates are kept at a high level [39,40], resulting in violent production rate needs, transloading rates are kept at a high level [39,40], resulting in violent collisions collisions between the lumps and wellhead bunker walls. Therefore, a buffer chute (Figure 13), a between the lumps and wellhead bunker walls. Therefore, a buffer chute (Figure 13), a flexible damper flexible damper (Figure 14) and interval blocking units (Figure 15) were installed at the (Figure 14) and interval blocking units (Figure 15) were installed at the transloading sections to relieve transloading sections to relieve the collisions and reduce lump loss of about 15%. the collisions and reduce lump loss of about 15%.

92911 Minerals 2015, 5, 919–935 Minerals 2015, 5, page–page Minerals 2015, 5, page–page Minerals 2015, 5, page–page

Figure 13. Buffer chute. Figure 13. Buffer chute. Figure 13. Buffer chute.

Figure 14. Flexible damper. Figure 14. Flexible damper. Figure 14. Flexible damper.

(a) (b) (a) (b) (a) (b) Figure 15. Interval blocking units: (a) bending section; (b) horizontal section. Figure 15. Interval blocking units: (a) bending section; (b) horizontal section. Figure 15. Interval blocking units: ( a) bending section; ( b) horizontal section. 4.7. Fragmentation-Prevention in Washing Processes 4.7. Fragmentation-Prevention in Washing Processes 4.7. Fragmentation-Prevention in Washing Processes 4.7. Fragmentation-PreventionAccording to previous studies, in Washing fragmentation Processes in washing process contributes significantly to According to previous studies, fragmentation in washing process contributes significantly to the overallAccording lump to loss previous [41,42]. studies, To improve fragmentation the washing in washingprocess and process overall contributes LCPR, measures significantly such asto the overallAccording lump to loss previous [41,42]. studies, To improve fragmentation the wash ining washing process process and overall contributes LCPR, significantly measures such to the as theprocess overall flow lump optimization, loss [41,42]. screening, To improve transloading the wash modifications,ing process and and overall storag eLCPR, adjustments measures were such used. as overallprocess lumpflow optimization, loss [41,42]. To screening, improve thetransloading washing processmodifications, and overall and LCPR,storage measures adjustments such were as process used. processIn flowcases optimization, where the screening,screening transloadingplant is under modifications, maintenance, and storag raw ecoal adjustments from the were shaft used. is flowIn optimization, cases where screening, the screening transloading plant modifications, is under maintenance, and storage adjustmentsraw coal from were the used. shaft is immediatelyIn cases transloadedwhere the toscreening the storage. plant To is avoidunder this,maintenance, a heavy mediaraw coalseparator from forthe lumpsshaft is immediatelyIn cases wheretransloaded the screening to the plantstorage. is under To avoid maintenance, this, a heavy raw coal media from theseparator shaft is for immediately lumps is immediatelycommonly used. transloaded In XCM, ato +25 the mm storage. heavy Tomedia avoid bevel this, wheel a heavy for lumps, media a 0.5–25separator mm forheavy lumps media is transloadedcommonly used. to the In storage.XCM, a +25 To avoidmm heavy this, media a heavy bevel media wheel separator for lumps, for lumpsa 0.5–25 is mm commonly heavy media used. commonlycyclone for used. fines, In and XCM, a − a0.5 +25 mm mm fl heavyotation media slime bevel unit wheelwas integrated for lumps, and a 0.5–25 used. mm However, heavy medialump Incyclone XCM, for a +25 fines, mm and heavy a − media0.5 mm bevel flotation wheel slime for lumps, unit was a 0.5–25 integrated mm heavy and mediaused. cycloneHowever, for lump fines, cyclonefragmentations for fines, resulting and a −from0.5 mm high-speed flotation rotationslime unit in wasthe integratedpumps, squeezing and used. in However,the pipes, lump and andfragmentations a ´0.5 mm flotationresulting slime from unit high-speed was integrated rotation and used.in the However, pumps, lumpsqueezing fragmentations in the pipes, resulting and fragmentationscollisions in heavy resulting media from cyclones high-speed were observed rotation. inTherefore, the pumps, the sievesqueezing size wasin the reduced pipes, fromand fromcollisions high-speed in heavy rotation media in thecyclones pumps, were squeezing observed in the. Therefore, pipes, and the collisions sieve size in heavy was mediareduced cyclones from collisions25 to 13 mm in soheavy that lumpsmedia overcyclones 13 mm were were observed injected. intoTherefore, the heavy the media sieve bevelsize waswheel reduced separator. from In 25 to 13 mm so that lumps over 13 mm were injected into the heavy media bevel wheel separator. In 25this to way, 13 mm the so LCPR that waslumps increased over 13 bymm 5.4%. were injected into the heavy media bevel wheel separator. In this way, the LCPR was increased by 5.4%. this way, the LCPR was increased by 5.4%. 930 12 12 12 Minerals 2015, 5, 919–935 were observed. Therefore, the sieve size was reduced from 25 to 13 mm so that lumps over 13 mm were injected into the heavy media bevel wheel separator. In this way, the LCPR was increased by 5.4%. MineralsMinerals 2015 2015, 5,, page–page5, page–page In the washing, and particularly the screening and transloading processes, lumps gain much energyIn while Inthe the washing, being washing, relatively and and particularly particularly brittle. As thethe a result, screeningscreening significant and transloadingtransloading lump fragmentation processes, processes, lumps occurs.lumps gain gain To much mitigate much thisenergyenergy issue, while severalwhile being being measures relatively relatively were brittle. brittle. adopted: As As aa (1)result,result, A cushion significant was lumplump placed fragmentation fragmentation on the feeding occurs. occurs. chute To To ofmitigate themitigate sizing sievethisthis toissue, decelerateissue, several several fast-moving measures measures were lumpswere adopted:adopted: entering (1)(1) the A sieve cushion and was reducewas placedplaced lump on on loss the the aboutfeeding feeding 5.8%. chute chute (2) of The ofthe frontthe endsizingsizing chute sieve sieve of the to to medium-removingdecelerate decelerate fast-moving fast-moving sieve lumpslumps was adapted entering to thethe decelerate sievesieve andand the reduce reduce falling lump lump lumps. loss loss Specifically,about about 5.8%. 5.8%. the chute(2)(2) The angle The front front was end end optimized chute chute of of theand the medium-removing medium-removing buffer plates were siev placede waswas inside adaptedadapted the to chute.to decelerate decelerate In this the the way, falling falling the lumps. traveling lumps. timesSpecifically,Specifically, of lumps the the in chute thechute chute angle angle were was was increased,opoptimizedtimized and resultingand buffer in platesplates a collection werewere placed placed of coal. inside inside (3) the Heightthe chute. chute. differences In Inthis this way, the traveling times of lumps in the chute were increased, resulting in a collection of coal. atway, various the transloadingtraveling times points of lumps were reduced.in the chute For were those increased, with height resulting differences in a largercollection than of 500 coal. mm, (3) Height differences at various transloading points were reduced. For those with height buffer(3) Height systems differences (rubber and at plasticvarious strips) transloading were installed points to were reduce reduced. lump fragmentation For those with as shown height in differences larger than 500 mm, buffer systems (rubber and plastic strips) were installed to reduce Figuredifferences 16. larger than 500 mm, buffer systems (rubber and plastic strips) were installed to reduce lumplump fragmentation fragmentation as as shown shown in in Figure Figure 16.16.

(a) (b) (a) (b) Figure 16. The buffer systems at transloading points: (a) rubber strips; (b) plastic strips. Figure 16. The buffer systems at transloading points: (a) rubber strips; (b) plastic strips. Figure 16. The buffer systems at transloading points: (a) rubber strips; (b) plastic strips. A fragmentation-prevention system (LKK-1, Figure 17) was installed in the bunker to mitigate lumpAA fragmentation-prevention fragmentation-prevention fragmentation in the storage systemsystem process. (LKK-1, The Figure coal lumps 17)17) was was dropped installed installed into in inthe the the chutebunker bunker after to to mitigatebeing mitigate lumplumpprocessed fragmentation fragmentation through inthein thesizingthe storagestorage screens. process.process. The impeller The The coal coalcoal lumpsfeeder lumps atdropped dropped the coal intochute into the exit the chute monitored chute after after andbeing being processedprocessedproperly through through adjusted the the the sizingsizing fall of screens. screens.the screened TheThe impellerlumps into coal the feeder feedersurge bunkerat at the the coal coalso that chute chute the exitstock exit monitoredmonitored level of the and and properlyproperlybunker adjusted adjustedwas kept the theat suitable fallfall ofof the thelevels. screenedscreened lumpslumps intointo the surge bunker bunker so so that that the the stock stock level level of of the the bunker was kept at suitable levels. bunker was kept at suitable levels. 2 1 2 4 31 4 3

6 5

6 5

9 8 7 10 9 8 7

10 Figure 17. LKK-1 fragmentation-prevention system: 1, signal relay of low stock level; 2, signal relay of high stock level; 3, electrode of low stock level; 4, electrode of high stock level; 5, coal chute; 6, surge bunker; 7, electromotor; 8, gearbox; 9, impeller coal feeder; 10, main conveyor. FigureFigure 17. 17.LKK-1 LKK-1 fragmentation-prevention fragmentation-prevention system: system:1, 1, signal signalrelay relay of of low low stock stock level; level; 2, 2, signal signal relay relay of of high stock level; 3, electrode of low stock level; 4, electrode of high stock level; 5, coal chute; 4.8.high Fragmentation-Prevention stock level; 3, electrode in of Railway low stock Wagon level; Loading 4, electrode Processes of high stock level; 5, coal chute; 6, surge 6, surge bunker; 7, electromotor; 8, gearbox; 9, impeller coal feeder; 10, main conveyor. bunker; 7, electromotor; 8, gearbox; 9, impeller coal feeder; 10, main conveyor. To overcome the limits of the conventional wagon loading processes, a novel fragmentation- 4.8.prevention Fragmentation-Prevention system was designed in Railway (Figure Wagon 18). This Loading system Processes consisted of a feeder, belt conveyer, and a To overcome the limits of the conventional93113 wagon loading processes, a novel fragmentation- prevention system was designed (Figure 18). This system consisted of a feeder, belt conveyer, and a 13 Minerals 2015, 5, 919–935

4.8. Fragmentation-Prevention in Railway Wagon Loading Processes To overcome the limits of the conventional wagon loading processes, a novel Minerals 2015, 5, page–page fragmentation-prevention system was designed (Figure 18). This system consisted of a feeder, belt conveyer,chute stock and level a chute control stock unit. level The control feeder unit. was The plac feedered wason top placed of the on topbelt ofconveyer the belt conveyerand a storage and ahopper storage between hopper betweenthe conveyer the conveyer and the chute and the was chute incorporated. was incorporated. A stock level A stock control level unit control consisting unit consistingof a sensor of aand sensor display and displaywas installed was installed at the ho atpper the hopper entrance. entrance. The hopper The hopper exit was exit wasconnected connected with withthe thebuffer buffer chute chute and and a gravity-controlling a gravity-controlling valve valve was was installed installed at atthe the chute chute exit, exit, which which was was on on top top of ofthe the railway railway wagon. wagon. This This fragmentation-prevention fragmentation-prevention system presentedpresented distinctdistinctadvantages. advantages. First, First, the the hopperhopper acted acted as as a buffera buffer unit unit and and the the falling falling heights heights of theof the lumps lumps were were kept kept within within a suitable a suitable range range by controllingby controlling the valve.the valve. Consequently, Consequently, both both noise noise and and lump lump loss loss was was reduced reduced by by 9.2%. 9.2%. This This system system isis also also expected expected to to adapt adapt coal coal lumps lumps of of various various sizes, sizes, demonstrating demonstrating great great potential potential for for industrial industrial applications.applications. Another Another noteworthy noteworthy benefit benefit of this of systemthis system is that is it isthat highly it is automatic highly automatic and few operators and few areoperators needed, are which needed, can greatlywhich can reduce greatly working reduce costs. working costs.

1 1 5

6 2

3 2 7

4 8 9 3 4

(a) (b)

Figure 18. Railway wagon loading processes: (a) conventional loading system; (b) fragmentation- Figure 18. Railway wagon loading processes: (a) conventional loading system; prevention loading system; 1, feeder; 2, belt conveyor; 3, chute; 4, railway wagon; 5, display of stock (b) fragmentation-prevention loading system; 1, feeder; 2, belt conveyor; 3, chute; 4, railway level; 6, sensor of stock level; 7, storage hopper; 8, winch; 9, valve. wagon; 5, display of stock level; 6, sensor of stock level; 7, storage hopper; 8, winch; 9, valve.

5. Economic Benefits 5. Economic Benefits The application of the techniques and optimization processes developed in this study The application of the techniques and optimization processes developed in this study significantly significantly improved the quality of the coal products and increased the anthracite yield, and improved the quality of the coal products and increased the anthracite yield, and finally increase finally increase profits of the coal mine. As shown in Table 2, an increase of 12 million CNY profits of the coal mine. As shown in Table2, an increase of 12 million CNY (113,851,993 ˆ 10.54% = (113,851,993 × 10.54% = 12,000,000) per year was viewed from the increased LCPR alone. 12,000,000) per year was viewed from the increased LCPR alone.

Table 2. Quantity and quality situation of coal products in 2009. Table 2. Quantity and quality situation of coal products in 2009. Contents Raw Coal Ash Moisture Calorific Value Incomes LCPR (%) Contents −1 Months Raw CoalQuantity Quantity (t) LCPR (%) Ash ContentContent (%) Moisture(%) ContentContent (%) (%) Calorific Value(kcal·kg (kcal¨ kg´1)) Incomes(CNY) (CNY) Months January 155,736 20.65 10.10 4.9 6399 - January 155,736 20.65 10.10 4.9 6399 - FebruaryFebruary 151,808151,808 22.21 22.21 9.859.85 5.1 5.1 6449 6449 - - MarchMarch 171,138171,138 21.0821.08 9.909.90 4.9 4.9 6369 6369 - - AprilApril 168,369168,369 19.2219.22 10.2110.21 4.8 4.8 6193 6193 - - May 168,631 23.05 9.79 5.4 5960 - JuneMay 162,735168,631 21.7423.05 12.119.79 5.2 5.4 6072 5960 - - 2009 JulyJune 160,838162,735 19.3121.74 11.1012.11 4.8 5.2 6131 6072 - - 2009 August 159,737 19.19 10.26 5.2 5820 - SeptemberJuly 167,610160,838 20.8719.31 10.6411.10 5.3 4.8 5651 6131 - - OctoberAugust 157,847159,737 22.34 19.19 9.8910.26 4.9 5.2 6057 5820 - - NovemberSeptember 153,856167,610 19.98 20.87 9.71 10.64 5.2 5.3 5848 5651 - - December 177,511 23.69 10.36 5.4 5943 - Indexes ofOctober 2009 1,955,816157,847 21.11 22.34 10.339.89 5.09 4.9 6074 6057 586,744,800 - IndexesNovember of 2008 1,681,680153,856 10.57 19.98 19.46 9.71 6.05 5.2 5876 5848 472,892,807 - Difference values 274,136 10.54 ´9.13 ´0.96 198 113,851,993 December 177,511 23.69 10.36 5.4 5943 - Indexes of 2009 1,955,816 21.11 10.33 5.09 6074 586,744,800 Indexes of 2008 1,681,680 10.57 19.46 6.05 5876 472,892,807 Difference values 274,136 10.54 -9.13 -0.96 198 113,851,993 932

14 Minerals 2015, 5, 919–935

6. Conclusions (1) Based on the analysis of the cutting thickness of the shearer drums, the influence factors have been understood, including traction speed, drum rotating speed, arrangement of cutting picks, and the number of helical blades. (2) For optimized shearer performance in XCM, the following parameters should be employed: traction speed of 4–5 m/min, drum rotating speed of 35 r/min (initial design speed is 42 r/min), and 30 cutting picks (initial design number is 36). Additionally, the pick length was increased while the pick density was decreased. Moreover, a rear-front one-way cutting approach was used in the mining process, and the mining height and roof supporting intensity were reduced accordingly. A combination of LPMB and FMM was also applied. (3) Based on the principles of lump fragmentation, the coalface end transloading, coalface crushing, transport systems, underground storage, and main shaft skip unloading processes were all improved. Fragmentation-prevention techniques were also applied in the washing and wagon loading processes. As a result, fragmentation of the lump coal was obviously reduced. The LCPR was maintained at a high level, and a great increase in annual profits was achieved. (4) In order to widely and confidently use the parameters and techniques determined in this study, some research directions should be required in future studies such as more on-site measurements of LCPR, laboratory analysis of mechanical mechanisms for coal fragmentation, and techniques for high-quality anthracite production of open-pit mining.

Acknowledgments: The research is financially supported by the National Basic Research Program of China (No. 2015CB251600), the National Natural Science Foundation of China (No. 51404254), the China Postdoctoral Science Foundation (Nos. 2014M560465 and 2015T80604), the Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1302050B) and the Fundamental Research Funds for the Central Universities (No. 2013QNB24). We wish to thank the XCM for supporting to conduct this important study, as well as Rong Zhou from YCPLC for the assistance of data collection. Special thanks are given to Jie-qing Yu from the China University of Mining & Technology, for his assistance with making illustrations, and Cheng-guo Zhang from the University of New South Wales, Australia, for his language assistance. The authors are also grateful to the two anonymous reviewers for their constructive comments and helpful recommendations. Author Contributions: All the authors contributed to publishing this paper. Wei Zhang performed the technological development and prepared and edited the manuscript. Dong-sheng Zhang revised and reviewed the manuscript. Hong-zhi Wang and Ji-xin Cheng partially participated in the literature research and data processing during the research process. Conflicts of Interest: The authors declare no conflict of interest.

Abbreviations YMA Yongxia Mining Area XCM Xinqiao Coal Mine LCPR Lump coal production rate CBT Cardox Blasting Technique YCPLC Yongcheng Coal & Power Company Limited NSP North Second Panel LPMB Loose presplitting millisecond blasting FMM Fully-mechanized mining

References

1. Guo, J.Q.; Kang, T.H.; Kang, J.T.; Zhao, G.F.; Huang, Z.M. Effect of the lump size on methane desorption from anthracite. J. Nat. Gas Sci. Eng. 2014, 20, 337–346. [CrossRef] 2. Huang, B.X.; Wang, Y.Z.; Cao, S.G. Cavability control by hydraulic fracturing for top coal caving in hard thick coal seams. Int. J. Rock Mech. Min. Sci. 2015, 74, 45–57. [CrossRef]

933 Minerals 2015, 5, 919–935

3. Yarushina, V.M.; Bercovici, D.; Oristaglio, M.L. Rock deformation models and fluid leak-off in hydraulic fracturing. Geophys. J. Int. 2013, 194, 1514–1526. [CrossRef] 4. Pang, L.; Hosseini, A.; Hussein, H.M.; Deiab, I.; Kishawy, H.A. Application of a new thick zone model to the cutting mechanics during end-milling. Int. J. Mech. Sci. 2015, 96–97, 91–100. [CrossRef] 5. Somanchi, S.; Kecojevic, V.J.; Bise, C.J. Analysis of force variance for a continuous miner drum using the Design of Experiments method. Int. J. Min. Reclam. Environ. 2006, 20, 111–126. [CrossRef] 6. Liu, X.H.; Liu, S.Y.; Tang, P. Coal fragment size model in cutting process. Powder Technol. 2015, 272, 282–289. [CrossRef] 7. Jiang, H.X.; Du, C.L.; Liu, S.Y.; Gao, K.D. Nonlinear dynamic characteristics of load time series in rock cutting. J. Vibroeng. 2014, 16, 292–302. 8. Saurabh, D.; Somnath, C.; Sergej, H. Investigation into coal fragmentation analysis by using conical pick. Procedia Mater. Sci. 2014, 5, 2411–2417. 9. Vidanovic, N.; Ognjanovic, S.; Ilincic, N.; Ilic, N.; Tokalic, R. Application of unconventional methods of underground premises construction in coal mines. Tech. Technol. Educ. Manag. 2011, 6, 861–865. 10. Lai, X.P.; Shan, P.F.; Cao, J.T.; Sun, H.; Suo, Z.Y.; Cui, F. Hybrid assessment of pre-blasting weakening to horizontal section top coal caving (HSTCC) in steep and thick seams. Int. J. Min. Sci. Technol. 2014, 24, 31–37. [CrossRef] 11. Reddy, S.K.; Sastry, V.R. Gallery monitoring in blasting gallery panel during depillaring—A case study. J. Mines Metals Fuels 2013, 61, 257–260. 12. Satyanarayana, I.; Budi, G.; Deb, D. Strata behaviour during depillaring in Blasting Gallery panel by field instrumentation and numerical study. Arab. J. Geosci. 2015, 8, 6931–6947. [CrossRef] 13. Wang, F.T.; Tu, S.H.; Yuan, Y.; Feng, Y.F.; Chen, F.; Tu, H.S. Deep-hole pre-split blasting mechanism and its application for controlled roof caving in shallow depth seams. Int. J. Rock Mech. Min. Sci. 2013, 64, 112–121. [CrossRef] 14. Zhao, T.B.; Zhang, Z.Y.; Tan, Y.L.; Shi, C.Z.; Wei, P.; Li, Q. An innovative approach to thin coal seam mining of complex geological conditions by pressure regulation. Int. J. Rock Mech. Min. Sci. 2014, 71, 51–52. [CrossRef] 15. Song, J.; Lian, Q.W. The relation between coal lump rate and cutting method of miner. Shanxi Coal 2003, 23, 20–21. (In Chinese) 16. Zhang, L.M. The current situation and developing trend of extremely thin coal seam mining of China. Appl. Mech. Mater. 2013, 295, 2918–2923. [CrossRef] 17. Li, Z.Q.; Oyediran, I.A.; Tang, C.; Hu, R.L.; Zhou, Y.X. FEM application to loess slope excavation and support: Case study of Dong Loutian coal bunker, Shuozhou, China. Bull. Eng. Geol. Environ. 2014, 73, 1013–1023. [CrossRef] 18. Kozan, E.; Liu, S.Q. A demand-responsive decision support system for coal transportation. Decis. Support Syst. 2012, 54, 665–680. [CrossRef] 19. Zhang, L.; Zhu, G.Q.; Zhang, G.W.; Han, R.S. Performance-based fire design of air-supported membrane coal storage shed. Procedia Eng. 2013, 52, 593–601. [CrossRef] 20. Wang, X.W.; Qin, Y.; Tian, Y.K.; Yang, X.Y.; Yang, Z.J. Analysis on flow features of bulk coal during coal unloading period based on EDEM. Coal Sci. Technol. 2015, 43, 130–134. (In Chinese) 21. Lv, H.L.; Ma, Y.; Zhou, S.C.; Liu, K. Case study on the deterioration and collapse mechanism and curing technique of RC coal bunkers. Procedia Earth Planet. Sci. 2009, 1, 606–611. [CrossRef] 22. Liu, S.Q.; Kozan, E. Optimising a coal rail network under capacity constraints. Flex. Serv. Manuf. J. 2011, 23, 90–110. [CrossRef] 23. Singh, G.; Sier, D.; Ernst, A.T.; Gavriliouk, O.; Oyston, R.; Giles, T.; Welgama, P. Mixed integer programming model for long term capacity expansion planning: A case study from The Hunter Valley Coal Chain. Eur. J. Oper. Res. 2012, 220, 210–224. [CrossRef] 24. Wang, Y. Using the limiting transferring device to increase the lump coal rate of anthracite. Coal Process. Compr. Util. 2008, 3, 10–12. (In Chinese) 25. Xie, W.N.; He, Y.Q.; Zhu, X.N.; Ge, L.H.; Huang, Y.J.; Wang, H.F. Liberation characteristics of coal middlings comminuted by jaw crusher and ball mill. Int. J. Min. Sci. Technol. 2013, 23, 669–674. [CrossRef] 26. Chen, J.; Chu, K.W.; Zou, R.P.; Yu, A.B.; Vince, A. Prediction of the performance of dense medium cyclones in coal preparation. Miner. Eng. 2012, 31, 59–70. [CrossRef]

934 Minerals 2015, 5, 919–935

27. Zeng, R.; Du, C.L.; Chen, R.J.; Wang, W.J. Reasonable location parameters of pick and nozzle in combined cutting system. J. Cent. South Univ. 2014, 21, 1067–1076. [CrossRef] 28. Reid, A.W.; McAree, P.R.; Meehan, P.A.; Gurgenci, H. Longwall shearer cutting force estimation. J. Dyn. Syst. Meas. Control 2014, 136, 1–9. [CrossRef] 29. Gao, H.B.; Yang, Z.J. Fluctuation analysis of thickness about roller shearer. Coal Mine Mach. 2013, 34, 106–108. (In Chinese) 30. Mazurkiewicz, D. Empirical and analytical models of cutting process of rocks. J. Min. Sci. 2000, 36, 481–486. [CrossRef] 31. Liao, X.; Zhang, J.; Feng, T.; Li, P. Intensity nonlinear analysis of central groove of coal shearer under limiting conditions. J. Southeast Univ. 2014, 44, 531–537. (In Chinese) 32. Bilgin, N.; Balci, C.; Copur, H.; Tumac, D.; Avunduk, E. Cuttability of coal from the Soma coalfield in Turkey. Int. J. Rock Mech. Min. Sci. 2015, 73, 123–129. [CrossRef] 33. Senneca, O.; Urciuolo, M.; Chirone, R. A semidetailed model of primary fragmentation of coal. Fuel 2013, 104, 253–261. [CrossRef] 34. Zhou, Y.D.; Liu, Y.L.; Tang, X.W.; Cao, S.Q.; Chi, C.J. Numerical investigation into the fragmentation efficiency of one coal prism in a roller pulveriser: Homogeneous approach. Miner. Eng. 2014, 63, 25–34. [CrossRef] 35. Thorpe, J.F. On the momentum theorem for a continuous system of variable mass. Am. J. Phys. 1962, 30, 637–640. [CrossRef] 36. Hao, Q.S. Increase setting in use of middle digging coalface by modifying crusher and optimizing coal drift. Northwest Coal 2008, 6, 56–57. (In Chinese) 37. Yu, T.F. Design and application of spiral chute in preventing lump coal crushing. Coal Mine Mach. 2014, 35, 207–209. (In Chinese) 38. Deng, J.J.; Huang, J.Y.; Kuang, Y.L. Design of integrated manufacturing system of coal preparation plant based on multi-agent. Procedia Earth Planet. Sci. 2009, 1, 713–717. [CrossRef] 39. Kou, B.F.; Liu, Q.Z.; Liu, C.Y.; Liang, Q. Characteristic research on the transverse vibrations of wire rope during the operation of mine flexible hoisting system. J. China Coal Soc. 2015, 40, 1194–1198. (In Chinese) 40. Peterka, P.; Kresak, J.; Kropuch, S.; Fedorko, G.; Molnar, V.; Vojtko, M. Failure analysis of hoisting steel wire rope. Eng. Fail. Anal. 2014, 45, 96–105. [CrossRef] 41. Wang, Z.G.; Kuang, Y.L.; Deng, J.J.; Wang, G.H.; Ji, L. Research on the intelligent control of the dense medium separation process in coal preparation plant. Int. J. Miner. Process. 2015, 142, 46–50. [CrossRef] 42. Noble, A.; Luttrell, G.H. A review of state-of-the-art processing operations in coal preparation. Eng. Fail. Anal. 2015, 25, 511–521. [CrossRef]

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