Comparison of Flotation and Screening as Separation Method in Coal Recovery From Tailings by Agglomeration

Dependency of Turkey on foreign energy adversely affects the economy of the country and may cause energy shortage in the near future. As a primary domestic energy source, coal is used for energy production in addition to imported oil and gas. However, significantamount of fine coal is lost together with tailings in coal washeries. Recovering of fine coals from these tailings will make an economiccontribution to country. In the present study, fine coals were recovered from tailings of a coal washery in Turkey by using oil agglomeration method. Flotation was used in agglomerate separation stage of oil agglomeration. Results were compared with that of previousstudy in which agglomerates were recovered by screening. The performance of the process increased sharply when flotation was usedinstead of screening in agglomerate separation stage. A clean coal with 28% ash was recovered from the washery tailings containing55% ash by 85% combustible recovery.

Research and Application of an Innovative 110 Mining Method in Gob-Side Half Coal Rock Entry Retaining

In order to solve the problems of the high cost and time consumption of half coal rock entry driving, low coal recovery rate, and stress concentration on filling support body of retained entry along gob, the innovative 110 mining method based on pressure relief by roof cutting was adopted in 6302 thin coal seam working face of Baoshan Coal Mine. First the technical principle and key technology of this mining method was presented. Then, through theoretical analysis and calculation, engineering experience, and field test, the key parameters such as the length of constant resistance anchor cable, the cutting angle and height of presplitting blasting, the charge structure, and the blocking-gangue support structure were determined and conducted in the retained entry. The broken expanded coefficient varying law of caved gangue with time and space was obtained, which revealed roof movement characteristic. The displacement monitoring curve of the roof and floor indicated that the maximum subsidence of the roof was about 150 mm and the maximum amount of floor heaving was 100 mm, which were quite small. The field monitoring data indicated that the entry retaining effect is good, which indicated that the innovative 110 mining method can be an effective way for reducing the high cost and time consumption of half coal rock entry driving, enhancing the coal recovery rate and preventing the dynamic mine pressure disasters.

Techno-Economic Feasibility of the Longwall Top Coal Caving Method Based on the FTCD Index: A Parametric Case Study in India

An extraction method for deep-seated thick seam deposits by underground mining with high resource recovery has remained a great challenge for Indian mining engineers, whereas the longwall top coal caving (LTCC) method has evolved as an effective method for various geo mining conditions in China and other counties. The percentage of top coal recovery (TCR) plays a predominant role in determining the feasibility of LTCC, which relies on the First Top Coal Caving Distance (FTCD). In this paper, the critical geotechnical parameters are identified, numerically simulated, and statistically analyzed, and the FTCD for Indian geo-mining conditions is developed and validated. A financial assessment is conducted, considering 70% top coal recovery at 85% performance level, cost of production escalated by 20% and fall in coal grade by two grades. The internal rate of return (IRR) for LTCC is 30.24% as per the sensitivity analysis where it is only 18% in single pass longwall method. This study contributes to evaluating both the technical and economic feasibility of introducing LTCC in Indian geo-mining conditions.

Mechanical Properties of Clay Based Cemented Paste Backfill for Coal Recovery from Deep Mines

Fly ash cement is used to solidify marine clay to prepare marine-clay-based cemented paste backfill (MCCPB) to fill the underground goaf of mines, which not only utilizes solid waste such as fly ash and marine clay, but also controls surface subsidence and protects the environment. To simulate the complex underground mine water environment of the filling body, a dry-wet cycle aquatic environment test under different material ratios and curing ages was designed. The water absorption and unconfined compression strength (UCS) of MCCPB with curing ages of 7 and 28 days under the action of 0, 1, 3, and 7 dry-wet cycles were investigated. The results indicate as the number of dry-wet cycles increases, the surface of MCCPB becomes significantly rougher, and the water content and the solid mass decrease accordingly. Different ratios and curing ages of MCCPB in dry-wet cycles of the UCS tend first to increase, then decrease. Meanwhile, the stress-strain curve of the specimen shows that the trend in the elastic modulus is consistent with that of UCS (first increasing, then decreasing), and that, the minimum UCS value of the specimen still meets the early strength requirements of cemented paste backfill in coal mine geothermal utilization. On the one hand, it proves the feasibility of fly ash cement-solidified marine clay for use as cemented paste backfill in coal mines; on the other hand, it also expands the available range of cemented paste backfill materials in coal mines.

Analisis coal losses pada kegiatan penambangan di Pit Inul Middle Panel 3 PT Kaltim Prima Coal

Coal Losses merupakan proses hilangnya batubara yang terjadi pada saat proses penambangan berlangsung sampai pada saat pengiriman batubara ke tujuan. Proses penambangan batubara seperti clean up roof batubara, proses pemuatan batubara, serta saat pengangkutan batubara menuju stockpile berpotensi menimbulkan coal losses. PT Kalimantan Prima Coal menetapkan coal recovery criteria sebesar 98,5%, lebih ketat dari yang ditetapkan Kementerian Energi dan Sumber Daya Mineral (ESDM) sebesar 90%. Penelitian ini bertujuan untuk menghitung coal losses pada proses clean up batubara, pemuatan batubara di loading point, dan pengangkutan batubara; mengetahui faktor-faktor yang menyebabkan terjadinya coal losses; dan memberi rekomendasi upaya penanganan coal losses.Penelitian dilakukan di Pit Inul Middle Panel 3 pada PT KPC bulan Mei dan Juni 2019. Ada lima seam batubara yang diamati, yaitu seam K17LR, K13, K12, K9 dan K4. PT KPC menggunakan survey yang dibandingkan dengan truck count untuk menghitung coal recovery. Total coal losses yang didapat dari setiap seam dibagi menjadi tiga proses penambangan batubara, yaitu coal losses pada saat clean up roof batubara, di loading point, dan saat hauling.Coal Losses yang didapatkan pada seam K17LR bulan Mei dan Juni 2019 sebesar 4,49% dan 3,93%; seam K13 bulan Mei dan Juni 2019 sebesar 2,83% dan 1,47%; seam K12 bulan Mei dan Juni 2019 sebesar 3,57% dan 2,71%; seam K9 bulan Mei dan Juni 2019 sebesar 4,24% dan 4,15%; seam K4 bulan Mei dan Juni 2019 sebesar 4,3% dan 1,11%. Coal losses yang terjadi masih di atas dari kriteria yang diberikan oleh ESDM sehingga masih memenuhi batas kriteria. Persentase coal losses terbesar terjadi di loading point sehingga dilakukan simulasi pengurangan coal losses di loading point. Total losses 19.43% pada Bulan Mei and dan 13.38% pada Bulan Juni berhasil diturunkan menjadi 9,44% and 6,98%. Kata-kata kunci : batubara, recovery, clean up, loading point, hauling

Numerical simulation of realistic top coal caving intervals under different top coal thicknesses in longwall top coal caving working face

In the process of longwall top coal caving, the selection of the top coal caving interval along the advancing direction of the working face has an important effect on the top coal recovery. To explore a realistic top coal caving interval of the longwall top coal caving working face, longwall top coal caving panel 8202 in the Tongxin Coal Mine is used as an example, and 30 numerical simulation models are established by using Continuum-based Distinct Element Method simulation software to study the top coal recovery with 4.0 m, 8.0 m, 12.0 m, 16.0 m, 20.0 m and 24.0 m top coal thicknesses and 0.8 m, 1.0 m, 1.2 m, 1.6 m and 2.4 m top coal caving intervals. The results show that with an increase in the top coal caving interval, the single top coal caving amount increases. The top coal recovery is the highest with a 0.8 m top coal caving interval when the thickness of the top coal is 4.0 m, and it is the highest with a 1.2 m top coal caving interval when the coal seam thickness is greater than 4.0 m. These results provide a reference for the selection of a realistic top coal caving interval in thick coal seam caving mining.

Risk Assessment and Prevention of Surface Subsidence under Buildings by Cemented Paste Filling and Strip Mining Methods: A Case Study

Intensive and continuous mining of coal resources in China implies their gradual exhaustion, especially in the eastern regions. While some mines face closure, others have to extract residual coal resources under buildings, water bodies, and industrial sites. Thus, safe and efficient mining of the residual coal resources requires innovative techniques, which would account for the particular site’s geological conditions. In this study, two schemes of roadway mining with cemented paste backfilling (RMCPB) and strip mining are put forward. After analyzing the type, construction, and protection standard of the buildings, the probability integration method and the prediction model are used to assess the surface subsidence and deformation. The research results show that both schemes can control the surface deformation to a certain extent, but RMCPB combines the advantages of a high coal recovery rate and disposal of gangue waste. According to the surface subsidence predicted and measured data, the RMCPB method can effectively control the surface subsidence, deformation, and buildings’ safety. It also yields significant economic and environmental benefits.

Dragline Stripping Method Review to Maximize Productivity and Coal Recovery at Major Fault Zone - A Case Study

Strategic mine planning is substantial to ensure maximum coal recovery across severely faulted geological conditions with predicted below water table excavation. An optimum plan would improve multiple engineering constraints to deliver high recovery with safety and best possible efficiency of machineries deployed at the problematic area. One such case is of Southern pit at Sasan coal mine, India with fault throw varying from 3m to 40m through a series of parallel merging faults located closely within strike length of 800m. It has challenged the mine for better coal recovery, machine performance and scheduled pit progression over recent corner strips. This paper describes how the mine has overcome complexities of operating in the fault area with localised consistent water seepage. It discusses new pre-strip parameters adopted to enhance dragline productivity, preparation of stable dragline operating bench under given bottom wet overburden conditions, and coal extraction plan which has been incorporated together with dragline stripping plan to improve recovery at the area of study. Several aspects of process have been highlighted during implementation, such as requirement of early dewatering setup for dragline low-wall stability and coal roof cleaning.

A numerical simulation of realistic top coal caving intervals under different top coal thicknesses in longwall top coal caving working face

In the process of longwall top coal caving, the selection of the top coal caving interval along the advancing direction of the working face has an important effect on the top coal recovery. To explore a realistic top coal caving interval of the longwall top coal caving working face, longwall top coal caving panel 8202 in the Tongxin Coal Mine is used as an example, and 30 numerical simulation models are established by using Continuum-based Distinct Element Method (CDEM) simulation software to study the top coal recovery with 4.0 m, 8.0 m, 12.0 m, 16.0 m, 20.0 m and 24.0 m top coal thicknesses and 0.8 m, 1.0 m, 1.2 m, 1.6 m and 2.4 m top coal caving intervals. The results show that with an increase in the top coal caving interval, the single top coal caving amount increases. The top coal recovery is the highest with a 0.8 m top coal caving interval when the thickness of the top coal is less than 4.0 m, and it is the highest with a 1.2 m top coal caving interval when the coal seam thickness is greater than 4.0 m. These results provide a reference for the selection of a realistic top coal caving interval in thick coal seam caving mining.

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

In longwall top coal caving (LTCC), the resource recovery ratio of the working face is directly determined by the top coal recovery ratio. An investigation of the evolution of top coal drawing characteristics and revealing the evolution of top coal drawing parameters is necessary when providing guidance for caving parameter selection and improving the top coal recovery ratio. Based on in-situ measurements of the size distribution of caved top coal blocks in Wangjialing coal mine, a finite difference method (FDM)–discrete element method (DEM) coupled method was applied to establish a “continuous–discontinuous” numerical model and the process from the first coal drawing to the common coal drawing was simulated with 17 separate working face advances. The evolution of the drawing body (DB), loose body (LB), and top coal boundary (TCB) was obtained. The results show that, the evolution of parameters of DB such as shape and size, drawing amount, length and deflection angle of the long axis of the profile ellipsoid tended to decrease first, then increase, decrease again, and finally stabilise; the increment of the LB advance coal wall distance and the coal pillar distance was close to 0 m in the common coal drawing stage, while width increment of the LB was close to the drawing interval (0.865 m). The TCB formed after each coal drawing round was fitted based on the improved “Hook” function. The evolution of height and radius of curvature of TCB’s stagnation point was analysed. This was divided into three stages: the first (first to third drawing rounds) was the initial mining influence stage, the second (fourth to ninth drawing rounds) was the transitional caving stage, and the third (after tenth drawing round) was the common coal drawing stage.