Oil Shale, 2003, Vol. 20, No. 3 SPECIAL ISSN 0208-189X pp. 295-303 © 2003 Estonian Academy Publishers
ESTONIAN OIL SHALE – RESOURCES AND USAGE
M. VEIDERMA* Estonian Academy of Sciences 6 Kohtu St., Tallinn 10130, Estonia
The reserves of oil shale (OS) in the world are estimated in the amount of 1013 t, i.e. they exceed the resources of other solid fuels (coal, lignite, brown coal) all taken together. The OS (kukersite) resources in Estonia form a tiny part of the world reserves. However, Estonia is the only country where OS studies and technologies have been continuously developed during more than 80 years. The only special OS periodical – the journal OIL SHALE – has been published in Estonia for eighteen years already. The OS deposits and OS industry are located in the North-East Estonia. Two deposits – the Estonia deposit and Tapa deposit (Fig. 1) – have been explored. The reserves of the Estonian deposit lying in the area of about 2 9 9 2000 km make nearly 5 ⋅ 10 t, including 1.5 ⋅ 10 t of active reserves (in the areas with no environmental restrictions where energy rating is at least 35 GJ/m2 and the calorific value of commercial bed OS is at least 8 MJ/kg). Southward and westward the depth of OS bed increases, its thickness de- creases and quality becomes lower (Figs 2 and 3). The reserves located be- tween the 35 and 25 GJ/m2 lines form passive reserves (in the amount of 9 2 ⋅ 10 t). The OS seams in the bed (indexed from A up to F) alternate with limestone interbeds. The latter form also the main part of the overburden. The characteristics of the Tapa deposit are pitiable, and its reserves are not accounted in the balance. In Estonia we have also another type of shale – black Dictyonema argillite. Efforts have been made to extract uranium and some other metals from this shale, but it is not the subject of this paper. The Estonian OS forms a peculiar class among the world OS resources. The organic matter of OS (kerogen) represents a mixture of high-molecular polyfunctional organic compounds, the real structure of which is yet a sub- ject of studies. The composition, calorific value and oil yield (by Fischer) of pure kero- gen as well as crude shale oil are presented in Table 1. The relatively high content of oxygen and chlorine in kerogen strikes the eye. Usually the con- tent of kerogen in the OS bedrock is 30–40 %. The mineral part of OS con- sists of carbonates, sandy-clayey minerals, pyrites, and others.
* e-mail: [email protected] 296 M. Veiderma
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P – operating mines and opencasts; opencasts; and mines – operating 3 Seli KOHTLA- JÄRVE – southern boundary of Estonia deposit; Estonia of boundary – southern 7 Southern part (Estonian Oil Shale), 2000 Shale), Oil (Estonian – exhausted areas; areas; – exhausted
u 2 d u T Eesti Põlevkivi ., et. al RAKVERE – boundaries parts of deposit; Estonia of 6 – outcrop line of the shale bed; bed; shale the of line – outcrop 1 TAPA Northwestern part Western part Middle part Eastern part Eastern part Middle part Western part Northwestern – county boundary; 5 Tapa deposit Tapa J ä r v a c o un t y c o vä r a J – passive reserve. Source: – Vello passive reserve. Kattai 9 1 2 3 4 5 6 7 8 9 . Oil shale reserves by fields: fields: by reserves . Oil shale Estonia deposit: H a r j u c o u n t y L ä ä n e - V I r u c o u n t y I d a - V I r u c o u n t n u o c u r I V - a d I y t n u o c u I r V - e n ä ä L y t n u o c u j r a H field boundary; boundary; field Fig. 1 reserve; Estonian Oil Shale – Resources and Usage 297
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m PK 9 5 10 11 12 13 m 3.5 3.5 3.0 3.0 F 0.26 2 0 .25 0 F1 0.42 .29 0.3 0.3 2.5 2.5 9 0 0 .38 0.31 E 0.56 0.30 0.28 F2 0.49 0.25 0.5 F 2.0 2.0 D/E 3 0.49 0.21 1 D 0.12 0.10 0.44 C/D 0.09 0.38 E 1.5 1.5 0.08 0.08 C 0.37 0.06 D 0.36 0.41 1.0 B/C 0.37 0.32 0.28 C 1.0 B 0.61 0.58 0. 44 0.31 0.27 0.25 B 0.5 0.5 1 A/B 1 A1 0.10 0.09 0.14 0.14 0.12 0.13 A A 0.17 0.13 0.11 0.09 0.08 0.06 A 0 0
Thickness of commercial bed, m Summary 2.93 2.73 2.68 2.49 2.26 2.05 Oil shale 2.35 2.14 2.10 1.78 1.56 1.37 Limestone 0.58 0.59 0.58 0.71 0.70 0.68
Calorific value, MJ/kg (1 and 2) and energy rating GJ/m3 (3) of the commercial bed 16 50
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Fig. 2. Estonia deposit. Changes in the structure and oil shale quality on north-south profile. Source: Vello Kattai et al., Eesti Põlevkivi (Estonian Oil Shale), 2000
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Estonian Oil Shale – Resources and Usage 299
Table 1. Characteristics of Estonian Oil Shale
Oil shale kerogen Shale oil C, % 76.5–77.5 81.7 O, % 9.0–11.5 6.8 H, % 9.4–9.9 10.5 S, % 1.2–2.0 0.7 N, % 0.2–0.5 0.3 Cl, % 0.5–0.9 Calorific value , MJ/kg 37.2 36–40 Oil yield, % 67.8
Commercial oil shale Kerogen, % dry basis 30–50 Mineral part, % dry basis 50–70 Moisture, % 10–15 Calorific value, mJ/kg Oil yield, % Size, mm
Power generation 8.7 – < 25 Retorting: Galoter 8.7 11.5–13 < 25 Kiviter > 11 15–17 25–125
The quality characteristics of commercial OS depend on the composition of OS bed, mining technology (bed as whole or selective mining, impover- ishment by rock of neighboring layers, etc.), results of enrichment and the purpose of OS use. The quality of Estonian OS may be rated as one of the best OSs in the world, but preserving the quality level in the longer perspec- tive will become still more difficult due to the mining activities advancing towards the peripheral part of the deposit. To the present time, OS has been mined in Estonia in the amount of 109 t. 6 The mining activities reached maximum (30 ⋅ 10 t per year) in the early 80s 6 and have been stabilizing during the last years at the level of 12–13 ⋅ 10 t. More than 80 % of mined OS is used in the power production complex (fine- grained OS with the average calorific value of 8.7 MJ/kg), the rest for proc- essing by the use of Kiviter retorts (lumpy OS with calorific value >11 MJ/kg), heat and cement production. The ratio of OS mined in under- ground mines and opencasts (at the depth < 25 m) is about 50 : 50 with a de- creasing tendency towards opencasts in the future conditioned by the in- crease of the OS bed depth. When the quality of mined OS does not correspond to the requirements of consumers, OS is enriched by either jigging or benefication in heavy suspen- sions. Lately some old mines have been closed, new mining equipment put to use, a direct rail communication for OS transport to power plant con- structed, and as a result the price of OS has dropped. Recultivation and reforestation of exhausted opencast areas is progress- ing. The problems and difficulties in the mining complex are connected with 300 M. Veiderma big losses of OS at mining and enrichment (more than 30 %), big seasonal wavering of production, voluminous dewatering (25 m3 water per ton of OS) and changes in the hydrogeological condition of surroundings, later setting of the surface above closed mines, and also complicated social situation be- cause of personnel reduction. In the course of restructuring the Estonian en- ergy system, the Estonian Oil Shale Company and the Narva Power Plants have merged to form a unified state-owned value chain. Before and in the first years after the World War II, electricity production was a side-branch in the OS use as the preference was given to its processing into oil products and fuel gas. Still in the 1950s two plants were constructed for heat and power supply to the OS region. Electricity generation increased rapidly in the 1960–1970s when two big power plants (with the total capac- ity of 3100 MW) based on burning pulverized OS were commissioned (Table 2).
Table 2. The Development of Power and Heat Production from Oil Shale
Construction time Plant MWe MWth 1930s Tallinn 11 1949–1967 Kohtla-Järve 39 534 1952–1957 Ahtme 20 338 1959–1971 Balti (BSEJ) 1624 686 1969–1973 Eesti (EEJ) 1610 84
4 blocks á 200 MW BSEJ 8 blocks á 100 MW Pulverized firing boilers, max 1400 ºC, efficiency 28 % EEJ 8 blocks á 200 MW
1995 – renovation of turbines extrarepairs of boilers new electrostatic precipitators demolition of old blocks etc. 2001 – installation of 2 blocks CFB boilers á 215 MW, ca 900 ºC, efficiency 32–34%
The aim of the Soviet authorities was to meet the electricity demand of the Northwest region of the former SU as possible on the basis of the local fuel. The electricity production reached its peak in 1980 (18.9 TWh) and from that time on has been gradually decreasing. In 2001, the OS-based elec- tricity production was about 7.5 TWh (including auxiliary power consump- tion of plants which forms about 10 % of production). After Estonia regained independence, the OS complex has guaranteed self-sufficient electricity supply at a temperate price for Estonia. OS covers 60 % of the country’s primary energy demand and 90 % of electricity pro- duction. Today the generating capacity of OS power plants exceeds much Estonian Oil Shale – Resources and Usage 301 the maximum demand of Estonia, but at the same time the working resource of the power plants is nearing the end, they are extremely obsolete, which results in increased expenses for repairs and high specific consumption of fuel. In the flue gas 80 % of SO2 formed by firing OS is bound by CaO in the ash. However, in 2000 the SO2 emission to the atmosphere was about 3 80 ⋅ 10 t (still twice less than in 1990). The emission of fly ash was reduced even more as a result of installation new electrostatic precipitators. Imple- mentation of fluidized-bed combustion units (beginning with two blocks, 215 MW each) should improve the production efficiency and reduce SO2 emissions essentially. However, extremely large investments are required for the major recon- struction of power plants, which in turn would bring along pressure on the electricity price. Besides the problems with high CO2 emission (for OS 0.106 kt CO2/TJ, the highest among primary fuels), those related to storing and making harmless huge amounts of alkaline ash and also to increased en- vironmental and resource taxes will remain. Utilization of ash (for the pro- duction of cement, autoclaved concrete elements, neutralizing of acid soils, etc.) has decreased and makes now a small part of the ash output, mainly for the efficiency and quality reasons. The use of the joint implementation and quota trade, foreseen by the Kyoto protocol, is of interest for Estonia, too. Taking into account the big changes in the daily and seasonal loads in power supply in Estonia, in the future the OS power plants should cover the basic or continuous (possibly also intermediate) power supply. For the sup-
Table 3. The Development of Thermal Processing of Oil Shale
Low-temperature (500–550 ºC) thermal processing
The use of lumpy oil shale (25–125 mm) 1924 – up to now Internally heated vertical retorts (Pintsch retorts →Kiviter process) 10 → 40 →100 →200 →1000 (→ 1500, designed) t OS per day 1928–1960s Tunnel ovens (horizontal, internally heated) 400 t OS per day 1931–1961 The Davidson rotary retorts (horizontal, externally heated) 25 t OS per day
The use of fine-grained oil shale (<25 mm) 1980– up to now Galoter process with solid heat carrier 3000 t OS per day
High-temperature (> 700 ºC) thermal processing of lumpy oil shale (25–125 mm) 1948–1970 Chamber ovens for gasification of oil shale 400 million m3 gas per year 302 M. Veiderma ply in peak-hours more flexible and efficient units based on natural gas and in the future probably also on shale oil have to be put in operation.* Resign- ing from the monopolistic energy concern that holds in our days the whole chain from power generation up to local grids and opening of electricity market should contribute to the efficiency improvement of the power com- plex and transition to contemporary energy regulation in Estonia. In the world stock OS is usually taken as a resource for oil and oil prod- ucts. The Estonian experience in producing shale oil, fuel gas and some chemicals as by-products is quite long-term and rather diverse, both by the way and amount of production and implemented technologies (Table 3). From 1948 to the 1970s the production of town gas for Leningrad and Tal- linn was the main direction of OS processing, later, in connection with the growing use of natural gas, it was reoriented again to the production of oil and chemicals. The composition of crude shale oil is distinguished by the high content of oxygen compounds (phenols, neutral oxygen compounds, etc.) in addition to aliphatic and aromatic hydrocarbons. In the middle 1990s, the production of shale oil reached nearly 400,000 t. Also oil coke, phenols, resins, glues, im- pregnates, tanning agents, mastic, and other products were produced. After that time the shale oil output came down due to the price changes both of OS and crude oil in the world market. Now the production is about 250,000 t per year, including almost 60 % for export – probably for the purposes where its lower viscosity and thickening temperature are of importance. During the last decades, two methods were used for OS processing. The Kiviter process (vertical retorts with internal heating, 1000 t OS per day) with the use of enriched OS ensures the oil yield of 15–17 %. However, the efficiency of the process is low (almost 30 % of organic matter gets lost with semicoke) and harmful semicoke accumulates in large waste piles. The Ga- loter process (of solid heat carrier, 3000 t OS per day) with the use of poorer pulverized OS gives the oil yield of 11.5–13 %. Although the energy effi- ciency of this process is higher and environmental impact lower, it requires bulky and less reliable equipment. At the same time, connectedness of OS retorting by Galoter process with the power plant is an essential advantage in both ways. The future of OS processing depends on the elaboration of new efficient technologies and prospects of enhancing the commercial value of products. The latter is the main goal of the studies, which are carried out in the frame- work of the US – Estonian joint programme of oil shale research or sup- ported by the EU and Estonian funds. More profound OS studies with the implementation of positive results in industry and attracting young people to the sustainable development of the OS complex are important for Estonia. The present changes in the Estonian energy system remind much about the period of restructuring coal and metal industries in the West Europe
* Ilmar Öpik. Oil Shale, 2002, Vol. 19, No. 2 Special, p. 197–210. Estonian Oil Shale – Resources and Usage 303 some decades ago and are similar to the processes going on in the countries of Central and Eastern Europe where solid fuel is dominating in the energy production. As a result of the unification negotiations with the EU, the Euro- pean Commission agreed to give OS temporarily a specific status and post- poned implementation of some requirements in Estonia otherwise foreseen by EU directives. International co-operation in the OS research and development, exchange of experience between research institutions, companies and people may ac- celerate the progress in the field of OS utilization. I hope that the present international symposium will give an impulse for that co-operation.