DEPARTMENT OF MINING Risk Assessment in the Quality Control of Oil Shale in Estonian Deposit Sergei Sabanov 28th Oil Shale Symposium October 13-17, 2008
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determination of oil shale quality Oil shale enrichment Selective mining Conclusion
Oil shale in Estonia GULF OF FINLAND ESTONIA IDA VIRU COUNTY Kiviõli 15 Uus Kiviõli 40 50 50 50 50 50 50 50 50 50 25 30 35 20 Aidu open cast 10 Kohtla Ojamaa Underground oil shale mining area, abandoned mines Ahtme Viru Sirgala open cast 20 15 10 Oandu 60 60 Estonia 30 30 30 30 30 30 30 30 30 25 25 25 25 25 25 25 25 25 Narva open cast 80 80 80 80 80 80 80 80 80 70 70 70 Seli UNDERGROUND OIL SHALE MINING FIELDS 45 55 40 Puhatu 35 Puhatu OIL SHALE RESEARCH FIELDS 35 GJ/m2 MINED OUT AREAS 65 25 35 GJ/m2 OIL SHALE OPEN CAST FIELDS OIL SHALE BEDDING DEPTH, meters CALORIFIC YIELD, SHOWS ACTIVE DEPOSIT 25 GJ/m2 Peipsi 80 Permisküla RUSSIA
Annual production of oil shale Million tones Viru mine 2 Estonia mine 5 Narva open cast 5 Aidu open cast 2 Põhja kiviõli open cast 1 Ubja open cast 0.3 Average 15-16
Characteristics of the oil shale and limestone seams 1 kwh ~ 1.4 kg of oil shale Shale oil ~16 % Layers Calorific value Kerogen Compressive Volume weight Lithology Thickness, m index GJ/t % strenght, MPa t/m3 F 2 0.17 6.7 19 24 1.72 F1/F2 0.18 2.9 8 65 2.10 F1 0.20 11.5 31 19 1.51 F 0.42 11.5 33 18 1.51 E 0.58 17.5 50 18 1.28 D/E 0.07 2.9 8 67 2.10 D 0.06 9.4 27 29 1.59 C/D 0.29 0.6 2 82 2.45 C 0.41 14.2 40 26 1.38 B/C 0.12 2.9 8 75 2.10 B 0.38 19.2 54 40 1.22 A1/B 0.18 1.3 4 65 2.25 A1 0.09 7.5 21 26 1.42 A/A1 0.06 2.9 8 32 2.10 A 0.12 15.1 43 32 1.37
Problems Raw material - extracted rock mass without enrichment does not meet requirements of customers for calorific values Decreasing calorific values in peripheral sides of the commercial oil shale deposit will demand additional enrichment of oil shale
Aim Elaboration of the risk assessment methods for quality control of oil shale in according with technical opportunities of extraction and enrichment processes for various parts of Estonian deposit
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determining quality of oil shale Oil shale enrichment Selective mining Conclusion
Oil Shale Mining Technology Losses in pillars 20-28 % Technological losses 13%
Open mining
Selective (surface) mining
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determining quality of oil shale Oil shale enrichment Selective mining Conclusion
Why is Risk Assessment? RISK ANALYSIS RISK EVALUATION Risk identification Risk mitigation Risk estimation Risk acceptance RISK ASSESSMENT Risk assessment is the process of deciding whether existing risks are tolerable and risk control measures are adequate
Risk Analysis Risk analysis is used for performing safety assessment for many different mining systems. Risk analysis includes: scope and risk analysis plan definition, risk identification, risk estimation Risk identification is the process of determining potential risks and starts with the source of problems, or with the problem itself. Failure can be described on many different levels. Conceptualization of the different possible failure modes for mining systems is an important part of risk identification. Risk estimation entails the assignment of probabilities to the events and responses identified under risk identification. Probability estimation can be grouped into three general approaches depending on the type and quality of the available data: analytical approach uses logical models for calculating probabilities; empirical approach uses existing databases to generate probability; judgmental approach uses experience of practicing engineers in guiding the estimation of probabilities
Risk Evaluation The principal role of risk evaluation in risk assessment is the generation of decision guidance against which the results of risk analysis can be assessed Risk mitigation is a selective application of appropriate techniques and management principles to reduce either likelihood of an occurrence or its consequences, or both Risk acceptance is an informed decision to accept the likelihood and the consequences of a particular risk
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determining quality of oil shale Oil shale enrichment Selective mining Conclusion
Main factors determining oil shale quality Environmental Oil shale seam quality deterioration is controlled by two factors - increasing fraction of limestone and decreasing calorific value. Calorific value and layer thickness vary from place to place within a deposit. These parameters decrease from the center to the border of a deposit. The variation in the value of the calorific value comes to 0.07 MJ/kg per km.
Main factors determination of oil shale quality Technological Oil shale quality depends on the enrichment process Oil shale enrichment process depends on the grain-size, the calorific value, the size category distribution and the availability of karst clay Distribution of size and calorific value directly depend on excavation technology: drilling-and-blasting and mechanical cutting
Drilling-and-blasting Size destribution Drill/Blast Content 0,90 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00 y = 0,0491x 0,519 R 2 = 0,9906 0 50 100 150 200 250 300 Size, mm The share of fine grain-size material (0-30 mm) comprises 30-40% and calorific value is 2.5-3.0 MJ/kg higher than calorific value of raw material (rock mass)
Drilling-and-blasting Power distribution Drill/Blast Calorific value, MJ/kg 14 12 10 8 6 y = -0,265Ln(x) + 11,015 R 2 = 0,7052 0 25 50 75 100 125 150 175 200 225 250 275 300 Size, mm The fine grained fraction (3.0-10.0 mm) has calorific value of 11.6-12.4 MJ/kg, but about 5 % of the fine grain > 1 mm which includes clay material will complicate the enrichment process.
Selective mining (Mechanical cutting) Size distribution Selective mining 1,00 0,80 y = 0,1124Ln(x) + 0,1639 R 2 = 0,8677 Content 0,60 0,40 0,20 0,00 0 10 20 30 40 50 60 70 80 90 100 110 120 130 Size, mm
Selective mining (Mechanical cutting) Power distribution Selective mining Calorific value, MJ/kg 14,0 13,5 13,0 12,5 12,0 11,5 11,0 y = -0,1114Ln(x) + 12,869 R 2 = 0,6328 0 25 50 75 100 125 150 175 200 225 250 275 300 325 Size, mm To achieve oil shale with calorific value 11.8-12.5 MJ/kg it is necessary to realize selective cutting not only of limestone and oil shale layers, but separately oil shale layers with concretions
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determining quality of oil shale Oil shale enrichment Selective mining Conclusion
Oil shale enrichment Advantage Structure of oil shale and accompanying breed (limestone) has differences in properties. It gives possibility to easily enrich by gravitational methods. Disadvantage As a result of the deterioration of oil shale quality in peripheral areas of the deposit, there arise problems in enrichment of the fine grain (0-25mm) fraction.
Oil shale enrichment Run-of-mine (0-700 mm) 100% - 9.22 MJ/kg Selective crushing Screening Sieving Flotation Separation Flotation Screening Dewatering & Drying Waste 29% Crushing Trade product 71% 14.41 MJ/kg
Oil shale enrichment Run-of-mine (0-400 mm) 100% - 8.37 MJ/kg Crushing Screening Sieving Flotation Separation Flotation Screening Dewatering & Drying Waste 38% Crushing Trade product 62% 11.62 MJ/kg
Oil shale enrichment Run-of-mine (0-50 mm) 100% - 7.6 MJ/kg Crushing Screening Sieving Flotation Separation (radiometric) Flotation Screening Dewatering & Drying Waste 51% Crushing Trade product 49% 11.8 MJ/kg
Quality-quantitive characteristic of slimes output in Estonia mine 25 20 15 10 5 Calorific value, MJ/kg 0 3.00-1.00 1.00-0.63 0.63-0.38 0.38-0.25 0.25-0.16 0.16-0.10 0.10-0.07 0.07-0.05 0.05-0.00 size, mm
Oil shale enrichment Dewatering of slime under using centrifuge is possible to exclude about 60 % of slime having sizes 0.7-1.0 mm. At the same time, slime with dampness 25-30 % will be transported together with non enriched riddling. The solids represent 50 % of size 0.01 mm Usage of the hydrocyclones, filter-press, pneumatic separators and centrifuges for enrichment of fine grained fraction of oil shale showed the possibility of increasing the calorific value
Presentation outline Introduction Mining technology overview Risk assessment in mining Main factors determining quality of oil shale Oil shale enrichment Selective mining Conclusion
Selective mining Seam Underground Lithology Thickness, Height from m A seam, m limestone 0.37 5.78 H 0.4 5.41 G/H 0.25 5.01 G 0.39 4.76 Selective mining limestone 0.05 4.37 F 5 0.06 4.32 limestone 0.22 4.26 F 4 0.06 4.04 limestone 0.17 3.98 F 3 0.37 3.81 Go to backfill 79 % of limestone IV limestone 0.11 3.44 F 1/2 0.17 3.33 limestone 0.18 3.16 Fü 0.20 2.98 Fa 0.42 2.78 2.36 Go to backfill 63 % of limestone III Extraction 2 Extraction 1 E 0.58 D/E 0.07 1.78 D 0.06 1.71 C/D 0.29 1.65 C 0.41 1.36 Go to backfill 86 % of limestone B + C I II B/C 0.12 0.95 B 0.38 0.83 A1/B 0.18 0.45 A1 0.09 0.27 A/A1 0.06 0.18 A 0.12 0.12 A+B +C limestone 27% 13% limestone A + A1 52% limestone
Selective (surface) mining Surface Miner Cutting depth up to 0.6 m Cutting width - 2.5 m
Selective (surface) mining d 0 =40mm cutting in oil-shale EF (0.43m) cutting in limestone seams A/B (0.18m) and C/D (0.25m) cutting in oil-shale B/C (0.36m)
Selective (surface) mining Surface Miner can cut limestone and oil shale seams separately and more exactly than rippers (2-7 cm) with deviations about one centimeter Primary crushing and fragmentation of mineral rock Separately extracted limestone (C/D and A'/B) can be left directly in mine, which reduces haul costs and increase run-out oil shale heating value without additional processing Less stress and strain on trucks due to minimum impact of the excavated material Reduce capacity requirements for preparation plants
Selective (surface) mining Improve mineral recovery especially in areas sensitive to blasting Due to precise cutting increase the output of oil shale up to one tonne per square meter The oil yield increase by 30%, up to 1 barrel per tone during the oil shale retorting, on account of the better quality Decrease mineral losses from 13% to 6% and dilution Reduce oil shale cost price by 20% due to less mineral losses
Summary Risk assessment allows selecting suitable means for enhancing the quality of oil shale using different mining technology in various parts of Estonian deposits and has the ability to solve problems of quality control of oil shale in accordance with technical opportunities for extraction and enrichment processes
Conclusions Risk assessment methods assist in the selection of correct technological aspects for prospective development of mining under various mine-geological conditions
DEPARTMENT OF MINING Thank You for Your attention! Estonian Science foundation (Grand No. 6558, 2006-2009) supported the research Contact information: Sergei Sabanov Ph.D., Senior Researcher Department of Mining Tallinn University of Technology, Estonia E- mail: sergei.sabanov@mail.ru sergei.sabanov@ttu.ee