Zhang Jiaqiang and Wang Dejie

(Development Research Center of China Geological Survey, Beijing, 100037)

1. Characteristics of oil shale

Oil Shale (oil shale) is a fine-grained sedimentary rock that is rich in organic matter, has fine bedding, and can be burned. Most of the organic matter in oil shale is oil-forming substances that are insoluble in common organic solvents, commonly known as "kerogen". Therefore, oil shale is also called "oil shale".

Oil shale is an energy mineral and a low calorific value solid fossil fuel. Generally speaking, oil shale that can produce more than 0.25 barrels (i.e. 0.034 tons) of shale oil per ton is often called "oil shale mine", or oil shale with an oil production rate higher than 4% is called "oil shale mine". For mining. In the past, our country classified oil shale with an oil content of more than 5% as rich ore, and its reserves were calculated; oil shale with an oil content of less than 5% was classified as poor ore, and its reserves were not calculated; some also classified oil shale with a low oil production rate Those above 6% are classified as poor mines, and those above 10% are classified as rich mines.

(1) Geological characteristics of oil shale

The appearance of oil shale is light gray to dark brown, mostly brown; it has fine bedding; the relative density is 1.4 to 2.7 tons/ cubic meter.

The main components of oil shale are organic matter, minerals and water. The kerogen content in oil shale is about 10% to 50%. Kernel is composed of complex high-molecular organic compounds, rich in aliphatic hydrocarbon structures and less in aromatic hydrocarbon structures. Organic compounds are mainly composed of carbon, hydrogen and small amounts of oxygen, nitrogen, and sulfur elements; their hydrogen to carbon atomic ratio (H:C) is 1.25 to 1.75, which is higher than the H:C ratio of coal's organic matter. If the kerogen content is high and the hydrogen-to-carbon atomic ratio is large, the oil shale oil production rate will be high. Minerals in oil shale include quartz, kaolin, clay, mica, carbonate rock, and pyrite, but they are mainly clay minerals. Minerals in oil shale are often uniformly and finely mixed with organic matter, and the mineral content is usually higher than the organic matter. When oil shale contains a large amount of clay minerals, obvious schistosity is often formed. The moisture content is related to the micropore structure between mineral particles. Oil shale contains moisture ranging from 4% to 25%.

The organic matter:mineral ratio of oil shale used for commercial mining is about 0.75:5 to 1.5:5, which is lower than the organic matter:mineral ratio in coal. The ratio in coal is often greater than 4.75:5.

(2) Genetic types of oil shale

According to the depositional environment, oil shale can be divided into three basic genetic types: continental, lacustrine and marine. The organic matter in continental oil shale is composed of lipid-rich organic matter, mainly including resin, spores, waxy epidermis and soft tissues of terrestrial plant roots commonly found in coal-forming wetlands or swamps. They undergo coalification after being buried. The organic matter in the oil shale is formed. Therefore, this oil shale is also a saprolite with high mineral content. The organic matter parent material in lacustrine oil shale mainly refers to lower plankton algae living in fresh water, salt water and salt lakes. After the algae are buried, they undergo decay and coalification to form the organic matter in the oil shale. The organic parent material in marine oil shale is mainly seaweed, unknown single-cell microorganisms and marine flagellates. Oil shale has a wide range of depositional environments, and therefore, oil shale contains a variety of organic matter and minerals.

2. Uses of oil shale

Oil shale can not only extract various fuel oils, but also various synthetic fuel gases and chemical raw materials, and the by-products are also It can be used to make bricks, cement and other building materials. To sum up, oil shale has three main uses.

1. Preparation of shale oil and related products by carbonization

If the oil shale is crushed and heated to about 500°C, shale oil can be obtained. Our country often calls shale oil artificial oil. Generally speaking, 1 ton of oil shale can extract 38 to 378 liters (equivalent to 0.3 to 3.2 barrels) of shale oil. After shale oil is hydrocracking and refined, various chemical products such as gasoline, kerosene, diesel, paraffin, and petroleum tar can be obtained.

2. Used as fuel for power generation, heating and transportation

First of all, it is used to generate electricity. There are two ways to use oil shale to generate electricity. One is to directly use oil shale as boiler fuel to generate steam to generate electricity; the other is to retort oil shale at low temperature to generate gaseous fuel, which is then sent to an internal combustion engine for combustion to generate electricity. The former form is currently commonly used. Secondly, oil shale combustion can be used for heating. In 2001-2002, the benefits created by Estonia's use of oil shale for power generation and heating for residents and industries accounted for 76% and 14% of national tax revenue respectively, which is of great significance to its national economy. Thirdly, oil shale combustion can be used to drive engines for long-distance transportation.

3. Production of building materials, cement and fertilizers

As a by-product, shale ash after the retort and combustion of oil shale is mainly used to produce cement, bricks and other building materials. In Germany, 300,000 tons of oil shale are used in cement production every year. In my country, the semi-charred ash residue after the retorting and combustion of oil shale is used to manufacture building materials such as blocks, bricks, cement, and ceramsite.

In addition, oil shale can also be directly used in the production of organic fertilizers. For example, Huiyuan Industrial Development Corporation of Tongchuan City, Shaanxi Province, plans to invest 10 million yuan to use the existing oil shale resources in the Indo-Taiwan region to carry out technological transformation on the basis of the original 50,000-ton phosphate fertilizer production line to build an annual output of 50,000-ton oil shale. Yan organic compound fertilizer production line.

Different countries have different uses for oil shale.