Coal is an ancient plant buried underground and experienced complicated biochemistry andphysical chemistrySolid gradually formed by changesflammabilitymineral。
Coal is known as black gold and food for industry. It has been one of the main energy sources used by the human world since the 18th century. Since the 21st century, although the value of coal is much lower than before, coal has been one of the indispensable energy sources for our production and life for a long time after all,The supply of coal is also related to the stability of the development of China's industry and even the whole society. The security of coal supply is also the most important part of China's energy security.
Carbon, hydrogen and oxygen are the main body of coal organic matter, accounting for more than 95%;Coalification degreeThe deeper, the higher the carbon content, the lower the hydrogen and oxygen content.Carbon and hydrogen are the elements that generate heat during coal combustion, and oxygen is the combustion supporting element.When coal is burned, nitrogen does not generate heat, but transforms into nitrogen oxides and ammonia under high temperature, which are separated in free state.Sulfur, phosphorus, fluorine, chlorine and arsenic are harmful components in coal, of which sulfur is the most important.Most of the sulfur is oxidized intosulfur dioxide(SO2), discharged with flue gas, pollutes the atmosphere, endangers the growth of animals and plants and human health, and corrodes metal equipment;When sulfur rich coal is used for metallurgical coking, it also affects the quality of coke and steel.Therefore, "sulfur content" is one of the important indicators for evaluating coal quality.
CoalOrganic matterUnder certain temperature and conditions, the combustible gas generated after thermal decomposition is called "volatile", which is composed of various hydrocarbons, hydrogencarbon monoxideAnd other compounds.Volatile matter is also the main coal quality index. Volatile matter has an important reference role in determining the way of coal processing and utilization and process conditions.Coal with low degree of coalification has more volatile matter.If the combustion conditions are not appropriate, coal with high volatile content will easily produce unburned carbon particles, commonly known as "black smoke";More carbon monoxide, polycyclic aromatic hydrocarbons, aldehydes and other pollutants are produced, and the thermal efficiency is reduced.Therefore, appropriate combustion conditions and equipment should be selected according to the volatile matter of coal.
There are few inorganic substances in coal, mainly water and minerals, which reduce the quality and utilization value of coal.Minerals are the main impurities of coal, such as sulfide, sulfate, carbonate, etc., most of which are harmful ingredients.
"Moisture" has a great impact on the processing and utilization of coal.When water becomes steam during combustion, it absorbs heat, thus reducing the calorific value of coal.The moisture in coal can be divided into external moisture and internal moisture, and the internal moisture is generally used as the index for evaluating coal quality.The lower the degree of coalification, the larger the internal surface area of coal, and the higher the moisture content.
"Ash" is the solid residue left after the complete combustion of coal, which is an important coal quality index.Ash mainly comes from incombustible minerals in coal.When minerals are burned and incinerated, they will absorb heat, and a large amount of slag will take away heat, soash contentThe higher the thermal efficiency of coal combustion is, the lower the thermal efficiency of coal combustion is;The more ash, the more ash produced by coal combustion, and the more fly ash discharged.Generally, the ash content of high-quality coal and washed coal is relatively low[1]。
Coal is distributed in all continents and oceanic islands, but the distribution of coal in the world is very uneven, and the reserves of coal in various countries are also very different.China, the United States, Russia and Germany are countries with rich coal reserves and major coal producers in the world, of which China has the highest coal production in the world.China's coal resources rank first in the world, second only to the United States, Russia and Australia[9]。
history
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coal
Although the important position of coal has been replaced by oil, for a long time, the gradual depletion of oil has led to its inevitable decline. Due to the huge reserves of coal and the rapid development of science and technology, new technologies such as coal gasification have become increasingly mature and widely used.
According to different original materials and conditions of coal formation, coal in nature can be divided into three categories, namelyHumic coal、Residual coalandSapropel coal。
China is the first country in the world to use coal.In the ancient cultural site of Xinle in Liaoning Province, there are coal handicrafts, and in Gongyi City, Henan Province, there are also ruins of making iron with coal cakes during the Western Han Dynasty.
《shanhaiching》In China, coal was called Shi Nie, and in Wei and Jin Dynasties, coal was called graphite or charcoal.the Ming dynastyLi ShizhenOf《Compendium of Materia Medica》The name coal was first used.
Greece and ancient Rome also used coal earlier. Theophrastus, a Greek scholar, wrote the Stone History about 300 BC, which recorded the nature and origin of coal;Ancient Rome started heating with coal about 2000 years ago.
formation
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coal
Coal is a layer of extremely thick black humus accumulated on the ground from the branches, leaves and roots of plants for millions of years. Due to the changes of the crust, it is constantly buried underground, isolated from the air for a long time, and under high temperature and pressure, it is formed by a series of complex physical and chemical changessedimentary rockThis is the formation process of coal.
The thickness of coal seams in a coal mine and the rate of crustal decline and vegetation in this arearemainsThe amount of accumulation is related.The coal seam of this coal mine is thick when the crust drops fast and the plant remains accumulate thick. On the contrary, the coal seam of this coal mine is thin when the crust drops slowly and the plant remains accumulate thin.And becauseCrustOftectonic movementMake the original level coal seam occurfoldandcrackSome coal seams are buried deeper underground, and some are pushed to the surface, or even exposed to the ground, which is easier to find.There are also some coal seams that are relatively thin and small in area, so they have no mining value. There is no updated statement about the formation of coal.
Formation of coal
Is coal formed this way?Whether some discussions should be further studied and discussed.A large coal mine has thick coal seams and excellent coal quality, but its area is not very large in general.If it is formed by natural accumulation of branches, leaves and roots of plants over millions of years, its area should be large.Because in ancient times there were forests and grasslands everywhere on the earth, there should be traces of coal storage everywhere underground;The coal seam is not necessarily very thick, because the branches, leaves, roots and stems of plants decay into humus, which will be absorbed by the plants again and again, so that they will not be so concentrated when finally buried underground, and the boundary between the soil layer and the coal seam will not be so clear.
However, there is no denying the fact that coal is indeed vegetablewreckageAfter a systematic evolution, this is an irrefutable truth. As long as you carefully observe the coal, you can see the traces of leaves and roots of plants;If the coal is cut into thin sections and observed under a microscope, very clear plant tissues and structures can be found. Sometimes things like tree trunks are preserved in the coal seams, and some coal seams are also wrapped with complete insect fossils.
coal
Under normal temperature and pressure on the surface, plant remains accumulated in stagnant water bodyPeatizationAction orSapropenization, into peat or sapropel;Peat orSapropelAfter being buried, the basement of the basin dropped and sank to the deep underground, which was transformed into lignite through diagenesis;When the temperature and pressure gradually increase, it will be transformed into bituminous coal through metamorphismanthracite。Peaticization refers to the process in which the remains of higher plants accumulate in the marsh and change into peat through biochemical changes.Sapropenization refers to the process in which lower biological remains are transformed into sapropel through biochemical changes in marshes.Sapropel is a muddy material rich in water and asphaltene.Glacial processes may contribute to the collection and preservation of remains of coal forming plants[2]。
Formation age of coal
In the whole geological age, there are three major coal forming periods worldwide:
Coal is the most widely distributed fossil energy resource in the world, which is mainly divided into four categories: bituminous coal and anthracite, sub bituminous coal and lignite.60% of the world's recoverable coal reserves are concentrated in the United States (25%)Soviet republics(23%) and China (12%). In addition, Australia, India, Germany and South Africa account for 29%. The coal output of the above seven countries or regions accounts for 80% of the world's total output. The proven coal reserves are more than 63 times of the oil reserves. Countries with rich coal reserves in the world are also major coal producers.
Coal Classification Table
According to the China Coal Classification Plan recommended by the National Science and Technology Commission, China's coal is divided into ten categories, generally referred to as lean coal, coking coal, fat coal, gas coal, weak caking, non caking, long flame coal, etc. as bituminous coal;Lean coal is called semi anthracite;Lignite refers to coal with volatile matter greater than 40%.
Anthracite can be used for manufacturing gas or directly as fuel, while bituminous coal is used for coking, coal blending, power boiler and gasification industry;Lignite is generally used in gasification, liquefaction industry, power boiler, etc.
Coal classification table (mainly coking coal)
category
anthracite
Lean coal
Lean coal
coking coal
Fat coal
Gas coal
Weak viscosity
Coalification
Nonstick
Coalification
Long flame coal
lignite
Volatile matter
0~10
>10~20
>14~20
14~30
26~37
>30
>20~37
>20~37
>37
>40
Characteristics of coke residue
-
0 (powder)
0 (in blocks)
8~20
12~25
12~25
9~25
0 (in blocks)~8
0 (in blocks)~9
0 (powder)
0~5
-
Coal particle size classification
classification
Oversize block
Large block
Midblock
Small pieces
Fine coal
Blended coal
Particle size (mm)
>100
50~100
25~50
13~25
0~13
0~50
0~100
National standard coal classification
The national standard divides coal into three major categories, namely anthracite, bituminous coal and lignite, 29 sub categories in total.Anthracite is divided into three sub categories. The numbers are 01, 02 and 03. The "0" in the number represents anthracite, the single digit represents the degree of coalification, and the small number represents the high degree of coalification;Bituminous coal is divided into 12 coal categories and 24 sub categories. The ten digits (1-4) in the number indicate the degree of coalification, while the small number indicates the high degree of coalification;The single digit (1~6) indicates cohesiveness, while the large number indicates strong cohesiveness;Lignite can be divided into two sub categories, the numbers are 51 and 52. The "5" in the number indicates the lignite, the single digit indicates the degree of coalification, and the small number indicates the low degree of coalification.
In the digital numbering of various coals, ten digits represent the size of volatile matter. For example, the volatile matter of anthracite is the smallest, the ten digit is 0, the volatile matter of lignite is the largest, the ten digit is 5, and the ten digit of bituminous coal is between 1 and 4. For bituminous coal, the single digit represents its caking property or coking property. For example, the larger the single digit is, the stronger the caking property is,For example, bituminous coal with a single digit of 6 is fat coal or gas fat coal with a maximum thickness of Y greater than 25 mm, while bituminous coal with a single digit of 1 is non caking coal, such as lean coal, non caking coal and long bituminous coal.The cohesiveness of bituminous coal whose single digit is 2-5 increases with the increase of the number[1]。
quality index
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(1) Moisture (M)
The moisture of coal is divided into two types. One is the internal moisture (Minh), which is the moisture contained when plants become coal;The second is the external water (Mf), which is the water attached to the coal surface and cracks during mining and transportation. The total water is the sum of the external water and internal water of coal.Generally speaking, the greater the degree of metamorphism of coal, the lower the internal moisture.The intrinsic moisture of lignite and long flame coal is generally high, while that of lean coal and anthracite is low.
The existence of water is extremely unfavorable to the utilization of coal. It not only wastes a lot of transportation resources, but also when coal is used as fuel, the water in coal will become steam and consume heat during evaporation;In addition, the moisture of clean coal also has a certain impact on coking.The calorific value decreases by 100kcal/kg (kcal/kg) when the general moisture increases by 2%;The coking time will be prolonged by 5-10min when the water content in refined coal is increased by 1%.
(2) Ash content (A)
The residue left after the coal is thoroughly burned is called ash, which consists of ash outside and ash inside.The external ash is from the roof and the rock fragments in the intermediate research, which has a great relationship with the rationality of the mining method.Most of the external ash can be removed by sorting.The internal ash content is the inorganic matter contained in the original plant itself, and the higher the internal ash content, the worse the coal washability.Ash is a harmful substance. With the increase of ash content in steam coal, the calorific value decreases, and the amount of slag discharged increases, the coal is prone to slagging;Generally, every 2% increase in ash will reduce the calorific value by about 100kcal/kg.With the increase of ash in refined coal, the utilization coefficient of blast furnace decreases, coke strength decreases, and limestone consumption increases;When ash content increases by 1%, coke strength decreases by 2%, blast furnace production capacity decreases by 3%, and limestone consumption increases by 4%.
(3) Volatile matter (V)
When coal is heated at high temperature and isolated from air, the gas and liquid products discharged are called volatile matter.The main components of volatile matter are methane, hydrogen and other hydrocarbons.It is one of the important indicators to identify the type and quality of coal.Generally speaking, with the increase of coal metamorphism, the volatile matter of coal decreases.Lignite and gas coal have higher volatile matter, lean coal and anthracite have lower volatile matter.
(4) Fixed carbon content (FC)
Fixed carbon content refers to the residue of removing moisture, ash and volatile matter, which is an important indicator to determine the use of coal.The difference after subtracting the moisture, ash and volatile matter of coal from 100 is the fixed carbon content of coal.The dry basisDry ash free baseAnd other fixed carbon content of different benchmarks.
(5) Calorific value (Q)
Calorific value refers to the heat generated when the unit mass of coal is completely burned, which is mainly divided into high calorific value andLow calorific value。The gross calorific value of coal minus the heat of vaporization of water is the gross calorific value.The international unit of calorific value is million joules/kg (MJ/kg), and the common unit is large calorie gram. The conversion relationship is: 1MJ/kg=239.14kcal/kg?1J=0.239gcal?1cal=4.18J。For example, the calorific value is 550kcal/g, 550kcal/kg=550 ÷ 23914=23MJ/kg. To facilitate comparison, when measuring coal consumption, we need to convert coal with different calorific values actually used into standard coal, and the calorific value of standard coal is 29.27MJ/kg (7000kcal/kg).The commonly used calorific value standard in domestic trade is the received basis low calorific value (Qnet, ar), which reflects the application effect of coal. However, external factors, such as moisture, have a greater impact, so Qnet and ar cannot reflect the true quality of coal.The general calorific value standard for international trade is the high calorific value on air drying basis (Qnet, ar), which can accurately reflect the true quality of coal and is not affected by external factors such as moisture.Under the same moisture and ash content, the high calorific value on the air drying basis is about 1.25 MJ/g (300 kcal/kg) higher than the low calorific value on the received basis.
(6) Maximum thickness of colloid layer (Y)
When bituminous coal is heated to a certain temperatureMaximum thickness of colloid layerIt's bituminous coalGlial layer indexThe maximum value of the difference between the upper and F layers of the colloid measured by the probe during the measurement.It is one of the important standards for coal classification.Steam coalThickness of colloid layerLarge, easy to coke;Smelting clean coal has clear requirements on the thickness of colloid layer.
(7) Bond index (G)
The ability to bond special anthracite with bituminous coal after heating under specified conditions is one of the important standards for coal classification and an important indicator for smelting clean coal.The higher the withering index is, the stronger the coking property is.
Scope of application
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The use of coal is very extensive, which can be summarized into three main uses according to its purpose: steam coal, coking coal, coal for coal chemical industry, mainly including coal for gasification, low temperature dry distillation, and hydrogenation liquefaction.
Steam coal
Coal power generation
(1) Coal for power generation: more than 1/3 of China's coal is used for power generation, and the average coal consumption for power generation is about 370g/(kW · h) of standard coal.Power plants use the calorific value of coal to convert heat energy into electric energy.
(2) Coal consumption of steam locomotive: accounting for about 3% of power coal consumption, the average coal consumption index of steam locomotive boiler is about 100kg/(10000 tons · km).
(3) Coal for building materials: accounting for more than 13% of power coal, the coal consumption for cement is the largest, followed by glass, brick, tile, etc.
(4) Generalindustrial boiler Coal consumption: In addition to thermal power plants and large heating boilers, industrial boilers for general enterprises and heating are of various types, large in number and scattered, and the coal consumption accounts for about 26% of steam coal.
(5) Domestic coal: The amount of domestic coal is also large, accounting for 23% of fuel coal.
(6) Power coal for metallurgy: the power coal for metallurgy is mainly anthracite for sintering and blast furnace injection, and its consumption is less than 1% of the power coal consumption.
coking coal
steel-making
Although China is rich in coal resources, coking coal resources are relatively small, and coking coal reserves only account for 27.65% of China's total coal reserves.
Coking coal includesGas coal(13.75%),Fat coal(accounting for 3.553%),Main coking coal(5.26%),Lean coal(4.01%), and other coals without different grades (0.55%);Non coking coal includesanthracite(10.93%),Lean coal(5.55%), weakly caking coal (1.74%), non caking coal (13.8%), long flame coal (12.52%),lignite(12.76%), natural coke (0.3%), undifferentiated coal (13.80%) and unclear coal (1.06%).
The main purpose of coking coal is to make coke, which consists ofcoking coalOr high temperature of mixed coalsmeltGenerally, only 1.3 tons of coking coal can be used to produce one ton of coke.Coke is mostly used for steelmaking and is the main raw material for steel and other industries. It is known assteel industry"Basic food".
China is a large coke producer and a major exporter of coke in the world market.In 2003, the global coke output was 390 million tons, and China's coke output reached 178 million tons, accounting for about 46% of the global total output.In terms of exports, China exported 14.75 million tons of coking coal in 2003, of which 4.58 million tons were exported to the EU, accounting for about 1/3.In 2004, China exported 14.72 million tons of coke, equivalent to 56% of the total global coke trade. The international coke market is still in short supply.In 2008, China's coke output totaled about 327 million tons, and from January to September 2009, the coke output was 252.7687 million tons[1]。
Situation in China
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Resource Overview
China is rich in coal resources, which are distributed in all provinces except Shanghai, but the distribution is extremely uneven.In the area between the Great Khingan Mountains Taihang Mountains and Helan Mountains in northern China, the geographical scope covers all or most of the six provinces and regions of Inner Mongolia, Shanxi, Shaanxi, Ningxia, Gansu and Henan with coal resources of more than 100 billion tons. It is the area where China's coal resources are concentrated, accounting for about 50% of the country's coal resources,It accounts for more than 55% of the coal resources in northern China.In southern China, the coal resources are mainly concentrated in Guizhou, Yunnan and Sichuan provinces. The total coal resources of these three provinces are 352.574 billion tons, accounting for 91.47% of the coal resources in southern China;The proven reserve also accounts for more than 90% of the proven reserve in southern China.
In 2007, the newly proved resource reserves of China's energy minerals increased significantly. There were 62 new large mineral sites for 17 major minerals, including 41 new large mineral sites for coal, 14 of which were super large mineral sites with resource reserves of more than 1 billion tons, with a net increase of 44.8 billion tons.The verified coal reserves in China have reached 724.116 billion tons, of which 186.822 billion tons have been occupied in production and under construction, and 453.896 billion tons have not been used.
From January to December 2006, China's coal mining and washing industry realized a total industrial output value of 698829619000 yuan, an increase of 23.45% over the same period of the previous year;The accumulated product sales revenue was 709234867000 yuan, an increase of 23.72% over the same period last year, and the total accumulated profit was 67726662000 yuan, an increase of 25.34% over the same period last year.
From January to December 2007, China's coal mining and washing industry realized a total industrial output value of 916447509000 yuan, an increase of 28.06% over the same period of the previous year.From January to October 2008, China's coal mining and washing industry achieved a total industrial output value of 1155383579000 yuan, an increase of 57.81% over the same period of the previous year.
The 11th Five Year Plan period is the best period for the structural adjustment and industrial transformation of the coal industry.Coal is China's basic energy, accounting for about 70% of the primary energy composition.The basic strategy of "coal based and diversified development" has been further established in the proposal of the 11th Five Year Plan, laying the foundation for the prosperity of China's coal industry.During the "Eleventh Five Year Plan" period, about 300 million tons of coal mines need to be built, of which 200 million tons will be put into production and 100 million tons will be carried forward during the "Twelfth Five Year Plan" period.China's coal industry will continue to maintain a vigorous development trend, and in a long period of time in the future, the development prospects of China's coal industry will be very broad.
According to the data released by the General Administration of Customs, in August 2014, China's coal imports fell to 18.86 million tons, down 18.11% month on month and 27.3% year on year, which has been falling for six consecutive months, and the decline has further expanded.[3]
On December 1, 2015, the website of Shaanxi Provincial Government reported that in order to solve the problems of insufficient demand and low prices in the coal market, Yulin City actively innovated the regional cooperation mechanism, created the terminal sales market and unblocked the transportation network.From January to October 2015, the cumulative sales of coal in Yulin reached 310 million tons, including 110 million tons of coal in Hebei Province, 40 million tons in Shanxi, 28 million tons in Guanzhong, Shaanxi, 24 million tons in Inner Mongolia, 18 million tons in Henan, 17 million tons in Shandong, 10 million tons in Ningxia, 8 million tons in Gansu, 7 million tons in Beijing and 4.5 million tons in Hubei, accounting for 86% of the total sales of coal in Yulin.
Basic information
Coal mining
China has a vast territory and rich resources. The Chinese nation depends on it to live, multiply, grow and stand onWorld nationThe forest needs material foundation.Among the 142 minerals discovered, coal occupies a particularly important position. It is rich in resources and widely distributed. The coal field covers an area of about 550000 square kilometers, ranking among the world's coal producing countries.
The geological age of coal accumulation period in China from old to new is mainly: early Cambrian of early Paleozoic; early Carboniferous, late Carboniferous early Permian and late Permian of late Paleozoic;Late Triassic of Mesozoic, Early and Middle Jurassic, Late Jurassic Early Cretaceous and Tertiary of Cenozoic.Among them, the coal accumulation is the strongest in the four coal accumulation periods of Late Carboniferous Early Permian, Late Permian, Early Middle Jurassic and Late Jurassic Early Cretaceous.China's coal bearing strata are all over the country, including the Proterozoic, Early Paleozoic, Late Paleozoic, Mesozoic and Cenozoic. Each province (region) has coal fields of different sizes and economic values.
The coal accumulation period and coal bearing strata in China are distributed in six coal accumulation areas, namely, North China, South China, Northwest, Southwest (Yunnan, Tibet), Northeast and Taiwan.
Issued by the State Council in 2014《Strategic Action Plan for Energy Development(2014-2020), we will focus on the construction of 14 large coal bases of 100 million tons in northern Shanxi, central Shanxi, eastern Shanxi, Shendong, northern Shaanxi, Huanglong, eastern Ningxia, western Shandong, Huaihe and Huaihe River, Yunnan Guizhou, central Hebei, Henan, eastern Inner Mongolia and Xinjiang.According to the data, the output of 14 large coal bases in 2013 was 3.36 billion tons, accounting for 91% of the total national output.[4]
Most of the coal mining is based on underground mine mining, which will inevitably lead to surface collapse, and the area of surface collapse is about twice that of coal mining. Long term surface collapse will lead to ponding and flooding in plain areas, and salinization of land resources in some areas, which is extremely serious for the destruction of land resources,In mountainous areas, serious surface collapse will also cause landslides and debris flows, which will have a very adverse impact on land resources and ecological environment, and will greatly damage the ecological balance.
(2) Water pollution
In the process of coal mining, a lot of water resources will be used. These water resources are generally discharged directly without treatment after being used up. The waste water resources from coal mining are very harmful to land and surface plants, and also cause waste of water resources.For example, there are a large number of farmland near the coal mine resources. If the abandoned water source in the coal development is not treated and infiltrates into the farmland, it will cause crop yield reduction or death;If it infiltrates into groundwater, it will pollute drinking water and directly threaten human health.Therefore, the waste water discharge in coal development has caused a very serious disaster to the environment and human beings, which must be highly valued.
(3) Air pollution
SO2 pollution
In the process of coal resource development, miningopencut coal mine, spontaneous combustion of gangue in the mine, gas drainage in the coal seam and other operations will produce or release a large amount of harmful gas and dust, and the waste gas mainly includes CO, COtwo、SOtwo、CHfourEtc.Wherein, CO, COtwo、CHfourWill cause greenhouse effect;SOtwoIt will not only pollute the air, but also affect the growth and development of plants in the mining area, and even lead to acid rain.Acid rain can not only destroy forests and crops in a large area, but also lead to acidification of water quality and death of most aquatic organisms, as well as corrosion of some buildings and other outdoor materials.
(4) Solid waste pollution
In the process of coal development, a kind of solid waste called coal gangue will be produced. This material is the most important solid waste in coal development. Since it has no use value, it is also piled up all the year round after being discharged, which will occupy a large amount of land around the mining area. At the same time, it will produce spontaneous combustion after weathering,The toxic gas discharged after spontaneous combustion has caused very serious damage to the natural environment near the mining area, and has accumulated into mountains of coal gangue after encountering rainstorm.[5]
(5) Geological damage
The unreasonable development and utilization of coal resources will have a serious impact on the geological environment.There are three main hazards to geology caused by unreasonable mining of coal mines, namely, destroying resources, polluting the environment, and causing geological disasters in mines.The destruction of resources caused by excessive coal mining is mainly manifested in the destruction of surface water storage and circulation and groundwater storage, resulting in the loss of surface water flow and the decline of groundwater level near the coal mine area. Not only the coal resources are seriously lost, but also the land resources are severely damaged;The problem of environmental pollution is mainly manifested in the migration and diffusion of hazardous substances such as gangue and coal seams, and the environmental indicators such as water quality, air and soil near the coal mine area seriously exceed the standard. There are two forms of common mine geological disasters, namely, underground geological disasters and surface geological disasters.Many mountain collapses and landslides in the coal mine area are caused by rock movement, and debris flow disasters are very common near the coal mine area.The various geological problems caused by the unreasonable development and utilization of coal resources not only have a great impact on the normal production and labor of employees in the coal mine area and the life of nearby residents, but also have a restrictive effect on the long-term stable development of coal enterprises.The most important thing is that the geological environment damage caused by unreasonable coal resource development and production is irreversible.[6]
concrete measure
1. Supplement and improve laws and regulations related to coal resource development and environmental protection
At the initial stage of the outbreak of environmental problems, the State promulgated and implemented the Coal Law of the People's Republic of China《Environmental Protection Law of the People's Republic of China》And other relevant laws and regulations, which are used to restrict the development of resources and other behaviors, increase the protection of the environment, so that natural resources can be more reasonably allocated and have achieved obvious results.However, through the practice of laws and regulations, it is found that although these regulations have guaranteed the coal development work to a certain extent, there are still many areas that need to be improved. The national macro-control and natural resource integration policies are difficult to carry out in some areas, so it is more important to further supplement and improve the relevant national policies and laws and regulations.In order to contain the resource waste and environmental pollution problems caused in the process of coal development to a certain extent and minimize the ecological loss, we should adhere to the concept of prevention first and treatment second, formulate and strictly implement the legal provisions used to restrict the ecological environment damage in the mining area. In the early stage, coal development projects must go through a strict approval process, and in the later stage,Environmental impact assessment must be carried out.
2. Integrate regulatory and law enforcement forces
The development of coal resources is a very systematic large-scale project. If the relevant departments are allowed to enforce the law separately, it is not conducive to the efficient development of ecological compensation for coal resources development. Therefore, if you want to coordinate a series of ecological compensation actions, you should prepare a full-time ecological management department of the mining area to take full charge of the related charges and supervision of ecological compensation in the mining area.
3. Reasonable collection of management taxes
The fund management of ecological compensation for coal resources is closely related to its implementation effect.The use of compensation funds must be transparent and earmarked for specific purposes.Coal resource mining enterprises shall pay ecological compensation fees according to laws and regulations. In order to urge enterprises to fulfill their ecological compensation obligations, they can collect ecological compensation reserve funds from enterprises in advance.The use of such funds shall comply with various laws and regulations.In addition, when inviting pollution control enterprises to restore ecology,Financial transfer paymentThe use of national compensation funds such as the recovery governance fund should be open and transparent, and the efficiency of fund utilization should be improved as much as possible.
4. Research on groundwater environmental protection measures
Do a good job in hydrogeology andEngineering geological surveyAnd forecast, standardize mining, and reduce theWater diversion fissure zoneTo protect the aquifer structure;The treated domestic sewage is used for farmland irrigation, and the treated construction waste water is reused without discharge.The mine drainage is mainly polluted by coal dust, and the concentration of suspended solids is high, so the high-efficiency coagulation sedimentation process should be adopted for treatment;The main pollutants of domestic sewage are COD, BOD and SSContact oxidation processIntegrated treatment equipment to prevent groundwater pollution caused by infiltration after surface water pollution;The main forms of subsidence are surface cracks, local landslides or collapses, which are mainly caused by water level decline. Methods such as strengthening floor conditions, reducing water inrush from the floor, or setting protective coal pillars for special structures should be adopted to effectively control the water level decline and slow down the impact on land subsidence;Do a good job of water circulation system and roadway water balance and safety support in the mining area to avoid serious impact on the groundwater environment and geological environment due to surface water expansion or groundwater inflow.
5. Mine geological environment protection and restoration measures
(1) Ground collapse: The ground collapse in the mining area is mainly the potential ground collapse in the goaf, and its protection, treatment and recovery are mainly to keep the roof of the roadway with a certain thickness to ensure its safety and prevent ground collapse.The main protection and treatment measures are as follows: intercepting and drainage ditches are set around the mobile basin due to ground collapse in the goaf to prevent the surface from flowing into the mobile basin and infiltrating into the goaf;In the process of mining, waste ore is used for backfilling;If the roof is unstable, metal anchor bolt and metal mesh can be used for auxiliary support.During mining, roof management should be strengthened to ensure the stability and safety of the stope;The newly added mined out areas shall be sealed, and the individual scattered mined out areas shall be isolated by concrete masonry rock sealing walls.The mined out area is closed after the mine is closed.
(2) Slope instability: the production shall be carried out in strict accordance with the design requirements of the mining scheme. In case of rock fragmentation zone, the slope gradient or height can be appropriately reduced;Intercepting and drainage ditches shall be set on the surface 5~8m away from the slope top to prevent the surface infiltration of soft rock and soil from affecting the slope stability;Plant trees and grass on exposed slopes, set retaining walls on potentially unstable slopes, and set retaining wall engineering measures to intercept and support waste rock piles and spoil piles;set upslope stability Monitoring points shall be monitored regularly, and treatment measures shall be taken in time in case of instability.
(3) Debris flow: set retaining wall engineering measures to intercept and support waste rock heap and spoil heap, build waste rock heap and intercepting and drainage ditches around the dump to prevent potential instability.Sand retaining dam shall be built in the valley downstream of waste rock dump and ore dump to prevent debris flow;Sand retaining dam shall be built in the valley downstream of waste rock dump and ore dump to prevent debris flow;Renovate the damaged or abandoned land and cover it with topsoil, waste rock heap and spoil heap for reclamation, plant trees, implement greening, and reduce water and soil loss.
6. Optimization of coal mining technology
Improve the coal mining technology, redefine the mining thickness, reduce the amount of coal gangue discharged, and effectively control the mixing amount of floor rock strata, so as to reduce the amount of washed gangue and gangue content of coal, change the traditional collapsed management roof to semi filled or filled management roof, and fill abandoned roadways and gobs with coal gangue,It can not only prevent the surface from sinking, but also reduce the area of coal gangue stacked on the ground, and reduce the impact of coal mining on aquifers, which is beneficial to protecting the ecological environment.[7]
Environmentally friendly coal mining
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(1) Innovating coal mining technology
For the innovation of coal mining technology, the first thing to consider is the clean production of the coal mine, that is, the coal gangue should not be treated out of the well, and the protective materials should be carried out safely. The main measures are as follows: First, the layout of the coal mine roadway should be changed, and the semi coal rock roadway and the multi layout coal roadway layout can be used, which not only reduces the cost of mine construction,It can also reduce the discharge of coal gangue solid waste;Secondly, the mining method and technology should be innovated. In the process of mining, the thickness should be reasonably determined in order to reduce the mixing amount of floor strata, so as to reduce the amount of washed gangue and gangue content in raw coal;Third, enrich the coal mining methods, such as short wall, combined house and housing mining, and improve the original fully collapsed roof management, such as half filled and half collapsed roof management, and filled and collapsed roof management.In addition, coal gangue solid waste is used to fill the goaf or abandoned roadway, which not only controls the discharge of coal gangue, but also improves the surface subsidence, at the same time, reduces the height of the water diversion fissure zone, so that the underground aquifer will not be affected by coal mining activities,So as to minimize the damage to the ecological environment.
(2) Comprehensive application of coal gangue
Although coal gangue is a kind of solid waste, it has the same burning value as ordinary coal, and can also be made into building materials through refining. Therefore, coal gangue should be effectively used and actively treated to achieve the goal of turning waste into treasure.In addition, because coal gangue also has certain combustion value, the combustible part of coal gangue shall be utilized by boiling combustion technology. At the same time, the mineral part of coal gangue shall be used as the raw material for extracting sulfur or preparing sulfuric acid to further exert its value.Because the comprehensive application of coal gangue is affected by certain conditions and constraints, such as economic, technological and market factors, it requires a certain amount of financial, human and material resources to achieve the above practices. If the best and effective treatment method is selected to solve the problem, the reclamation method can be selected, that is, the reclamation technology based on the gangue yard,It can be said that it is the best way to combine biological reclamation technology with engineering reclamation technology. This kind of reclamation method has greatly reduced the cost of "turning waste into treasure" of coal gangue, and also restored the ecological environment of the coal mine area, thus providing a strong guarantee for the joint realization of coal mining and ecological balance development.
(3) Surface anti damage technology
First, control measures for ecological collapse.In view of the collapse in the process of coal mining, land reclamation technology, building anti mining deformation technology and ecological engineering technology can be used to control it;Second, control methods to prevent mining collapse.The control method of collapse in the process of coal mining can be realized by applying reasonable mining technology and methods, in order to reduce the occurrence rate of surface subsidence, or minimize the scope of surface subsidence, thus providing a strong guarantee for the stability of ground buildings in the mining area.In general, the purpose of preventing surface collapse can be achieved by innovating the traditional caving mining technology and applying the strip mining method, so as to ensure the stability and safety of the surface while mining coal resources, so as to achieve the win-win goal of obtaining higher economic and social benefits.
(4) Comprehensive utilization of gas
Make full use of the combustible characteristics of gas, promote the application of new technologies, establish a gas drainage system, carry out the pre drainage technology of coal seam gas, and realize the comprehensive utilization of gas in local areas through the extraction and purification of gas in the coal roadway, and the combustion of gas to generate electricity. On the one hand, it improves the gas safety status of underground operations of coal mining enterprises, on the other hand,Realize the comprehensive utilization of gas resources, reduce the operating cost of the enterprise, and improve the efficiency of the enterprise[8]。
Industry development
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Status analysis
1. Analysis of market development status
——Balance between supply and demand in the industry
Coal is mainly used in power, steel, cement and chemical industries.Judging from the growth of major downstream coal consuming industries, the growth rate of output in a single month has declined, but it still remains at a relatively high level.From January to August, the thermal power generation capacity was 222.1 billion kWh, up 18.47% year on year;The pig iron output was 403.63 million tons, up 12.76% year on year;The cement output was 1178480000 tons, up 14.66% year on year;The output of synthetic ammonia was 34.39 million tons, up 0.93% year on year.
The output of raw coal from January to August was 2164.85 million tons, up 18.10% year on year, of which the output in August was 295.8 million tons, up 13.10% year on year and 0.27% month on month;The output of coal has not significantly exceeded the growth rate of downstream demand. From the perspective of the growth rate of supply and demand, there is no situation of supply exceeding demand. According to Bohai Securities, today's coal demand level is about 3.25 billion tons, and the supply level is about 3.24 billion tons. The annual supply and demand are basically balanced.
——The fundamentals of the whole industry may remain stable in the fourth quarter
Since the central government has included energy conservation and consumption reduction into the binding assessment indicators of various regions, in order to ensure the completion of the energy conservation goals of the "11th Five Year Plan", some regions have begun to take mandatory measures such as limiting production and electricity or shutting down high energy consuming industries, so the energy demand in the fourth quarter may face some pressure compared with the past.
However, the fourth quarter is the winter heating season in northern China, which is also the traditional peak season for coal sales. The purchase and sales of winter coal storage are gradually starting. The downstream power plants are more active in replenishing inventory. Market transactions will gradually become active, and sales may increase.
With the superposition of two factors, it is expected that the coal price in the fourth quarter will continue to remain stable and may maintain a slightly volatile trend.However, if the weather experts expect, Europe will encounter the lowest temperature winter in a thousand years, which may affect the price trend and supply and demand relationship of the coal industry.
2. Analysis of market characteristics
(1) Ultra high power coal inventory once again suppresses coal supply, demand and price.In the first ten days of October, the coal inventory of the national key power generation enterprises once again climbed to an ultra-high level of 62.3 million tons, and the number of days of inventory availability also exceeded 21 days. This situation not only significantly reduced the pressure of power enterprises to carry out "winter storage" of power coal, but also suppressed the supply, demand and price of power coal.
(2) The expectation of "cold winter" and the coal reserve in winter may increase vitality.After October, it is the time for "winter storage" of coal. Although the current coal inventory of power enterprises is still at a high level, the pressure of "winter storage" is not great, but the probability of "cold winter" is high, which may have a positive impact on the supply and demand of coal in winter.
(3) The supporting effect of coal import on domestic coal supply and demand may decline.The support effect of coal import on domestic coal supply and demand in the future period or will decline is judged based on two factors. First, considering all aspects of the situation, the international coal supply and transportation environment is developing in a direction that is not conducive to China's coal import, bringing variables to the coal import in the future period.Since September, the price of steam coal in Australia has gradually risen, and low calorific value Indonesian coal has increasingly become the first choice for China's coal import, which has promoted the rise of Indonesian coal export price.Secondly, China's coal imports reached 11.138 million tons, 12.653 million tons and 16.385 million tons in October, November and December 2009, respectively. Due to the large base, there is little room for further increase on the above basis in the fourth quarter. At that time, the increase of coal consumption demand will have to rely on the growth of domestic coal supply.
(4) On October 13, 2015, the latest data released by the General Administration of Customs showed that from January to September 2015, the country had imported 156.36 million tons of coal, a year-on-year decrease of 66.47 million tons, or 29.83%.In addition, China exported 730000 tons of coal and lignite in September 2015, an increase of 290000 tons year on year, and the monthly export volume was the highest since July 2013.Although the import volume continues to decline and the export volume continues to increase, the contradiction of oversupply in the domestic coal market is still prominent.
Development factors
Favorable factors
(1) Policy aspects
On the whole, first, affected by multiple factors such as freezing rain and snow disaster, tight transportation capacity during the Spring Festival, some coal mines' shutdown for rectification and early holidays in early 2008, the National Development and Reform Commission and the transportation department issued emergency notices to ensure coal supply and material transportation when power coal supply was tight in some regions.
Second, in the middle of the year, when the price of coal, especially steam coal, rose rapidly, the State Council issued an announcement to ensure the supply of power coal, and the National Development and Reform Commission twice intervened in the temporary price of power coal.
Third, starting from the long-term healthy development of the coal industry, the Ministry of Finance and the Ministry of Land and Resources strengthened the management of the payment of mining rights by stages in the reform pilot;The State Council raised the coal export tariff;The National Development and Reform Commission and the Energy Administration have issued a notice on the plan to close small coal mines three years after the 11th Five Year Plan.
(2) Technical aspects
With the rapid development of modern science and technology, modern new concepts, new processes and new technologies continue to penetrate into the field of coal science and technology, effectively promoting the rapid development of coal science and technology.
First, the level of exploration and mining technology has been continuously improved.
Secondly, the equipment level has been improved, and great achievements have been made in the construction of high-yield and high-efficiency mines.
Third, coal mine gas, fire control and other safety production technologies have been continuously improved.
Fourth, clean coal technology accelerates the development of comprehensive processing and utilization of resources.
Adverse factors
(1) Increased volatility in the coal market
The price of coal is affected by many factors, and market supply and demand is the most important factor.In 2009, China's coal preliminary investment will be released centrally.In the short term, the scale of coal mine under construction is too large, the pressure of overcapacity increases, and the demand is relatively insufficient.In the short term, the macro-economic development slows down, and the coal demand of power and other industries is declining.The investment in coal fixed assets has experienced rapid growth for more than five years, the construction scale has been expanding, and the production capacity has increased rapidly.The successive completion and release of these capacities will intensify the pressure of overcapacity.
(2) The state's requirements for production safety have increased.
risk analysis
(1) Market competition risk
With the deepening of marketization, coal construction enterprises have also been pushed to the market. However, the management system of coal construction enterprises has not changed greatly, and the mechanism is not active.Whether the coal construction project can be fully and smoothly implemented is the key to solving the relationship between the project and the enterprise. The unclear responsibility, fuzzy relationship, insufficient incentives, loose constraints, and too many uncertain factors between the project and the enterprise seriously affect the normal implementation of the coal project construction management. The coal project construction management must adapt to the requirements of modern enterprise system construction through innovation.
It is still a common phenomenon that coal construction enterprises have excessive competition in project bidding, and win the bid at a low price.The coal construction enterprises can not fully follow the laws of the market economy, some laws and regulations are not perfect, there are many human factors, policy guidance, industry behavior and even gray transactions, but in any case, the trend of the market economy is unstoppable,The gradual improvement and internationalization of the coal construction market will inevitably require our coal construction project management to constantly innovate to adapt to the laws of market economy.
The bidding risk is similar to the market risk in the general manufacturing industry. After the implementation of the bidding system in the construction field of our country, the construction enterprises basically have to win the bid in the form of bidding quotation.In order to obtain engineering projects, the competition among enterprises is very fierce.If an enterprise can't get the project, it will have no profit to talk about. The bidding enterprise can only pay for the people, money and things paid for bidding.If the bidder wins the bid at a low price or there are unfavorable clauses in the bidding documents for the contractor, or the calculation is wrong, the items are omitted, the fees are improperly charged, or the operation and management fail due to other reasons, and the loss is caused, in addition to the non-standard operation and abnormal factors in the bidding market, it will bring huge risks to the contractor.
(2) Risk analysis of raw material pressure
First, the natural occurrence conditions of the coal seams;
Second, the management level of producers;
Third, the attitude towards national coal resources;
Fourthly, the complexity of mining technology;
The fifth is the occupancy of mining investment.
The technical level and management level of township coal mines are relatively low, the mining facilities are simple and the capital occupation is small. In addition, the value of coal resources is not enough, and the raw coal production cost is far lower than that of state-owned coal mines.Township coal mines are about 50% lower, and some are even more than 65% lower.Therefore, township coal mines have the advantage of low price competition, and excessive low price competition is extremely unfavorable for state-owned coal enterprises to turn losses into profits and long-term development[4]。
Development suggestions
(1) Adjust the structure of railway transport capacity
Due to the influence of transportation bottlenecks and the imbalance of transportation capacity allocation, the coal in China's main coal producing areas has been supplied to the relatively narrow coastal areas in eastern and southern China for a long time, while the central Hunan, Hubei and Jiangxi provinces, most provinces and regions in the southwest and some regions in the west have made coal supply, especiallyElectric coalThe supply has been quite tight.Therefore, efforts should be made to adjust the structure of railway transport capacity and increase investment in railway construction in areas with tight coal supply and transport capacity shortage.
(2) Accelerate the construction of large coal enterprises
The concentration of China's coal industry is still low, the coal mining enterprises are too scattered, and there are a large number of individual mining. On the one hand, the management of coal enterprises by the central and local governments is more difficult, and the safety problem is a headache;On the other hand, it aggravates the uncertainty of coal supply and increases the volatility of the market.As a decreasing non renewable resource, the state should implement unified management and planning for its mining and use, rather than letting it go.There is no doubt that large coal production enterprises have advantages in technology, safety, controllability, etc. Therefore, it is necessary to effectively integrate the existing coal resources.On the one hand, all enterprises that do not have the conditions for safe and scientific mining should be resolutely closed. On the other hand, the government should take the lead in organizing a large number of decentralized coal mining enterprises to form large coal groups and bases in the form of shareholding system in accordance with the market operation mode, and implement unified mining, unified management and unified sales.
Coal and electricity are closely linked upstream and downstream industries. The coal consumption of power enterprises accounts for more than half of the national coal consumption. The coal power pool model has been widely recognized.Coal is the main source of energy in China. For a long time, coal has been transported from the west to the east and from the north to the south. Because the distribution of resources cannot be changed, in order to change the situation of periodic shortage of energy supply, we must use the market mechanism to solve the coal electricity conflict, promote the integration of coal and electricity, and promote industrial integration.The mode of coal power pool can be varied, such as setting up a pithead power plant in the place where the coal mine is located, changing "coal transportation" to "power transmission", speeding up the development of ultra-high voltage power transmission, increasing the proportion of local coal power conversion, and reducing the pressure of coal power transportation.Secondly, coal power enterprises can also sign long-term coal supply and demand agreements to carry out strategic cooperation in coal power.Thirdly, large coal enterprises and power generation enterprises can form coal power integration enterprises through mutual equity participation.Finally, make coal power enterprises promote strategic cooperation through asset restructuring, joint listing, mergers and acquisitions and other forms.
In June 2015, Inner Mongolia issued the Notice on Supporting the Reorganization of Coal Conversion Enterprises and Coal Production Enterprises.It was announced that the reorganization of upstream and downstream coal enterprises in Inner Mongolia had begun, and many coal enterprises and power enterprises had reached cooperation intentions to resolve the problem of overcapacity.The purpose is to effectively resolve the overcapacity of coal and promote the reorganization and merger of coal power and coal chemicals.
(4) Accelerate industrial restructuring
The rapid development of many industries in China is based on low electricity prices, low coal prices and high energy consumption. The rising market price of coal reflects the excessive consumption of energy in these industries.We should make determination and efforts to control the excessive growth momentum of high energy consuming industries, improve industrial policies, speed up industrial restructuring, curb unreasonable energy demand, and effectively transform the mode of economic development.On the one hand, it is necessary to tighten the opening and raise the threshold for high energy consuming industries and overheated industries in terms of project licensing, land, environmental protection, credit supply, etc.On the other hand, reform the resource price formation mechanism as soon as possible, so that resource prices fully reflect the scarcity of resources and environmental costs, so that improving energy efficiency becomes a conscious act of enterprises.
(5) Accelerate the reform of resource taxes and fees
The reform of China's resource tax system has changed from quantity based to price based, and the paid use of resources based on reserves and linked to recovery rate has increased the difficulty of obtaining coal resources, increased the initial investment and financial costs of coal production, and prevented coal mines from blindly expanding production scale;On the other hand, it will enable coal production enterprises to cherish resources more, save resources, allocate mining more scientifically and rationally, and to some extent, curb the behavior of "picking fat and losing lean" and blindly increase output.
(6) Accelerate the construction of market system
Northeast Asia Coal Trading CenterFounded in July 2009, it is committed to promoting the construction and development of the coal market system and establishing a highly information-based, standardized and open coal electronic trading platform and coalSupply Chain ServicesPlatform.
With the profound change of the coal industry environment and the acceleration of the marketization process, the Northeast Asia Coal Trading Center proposed the vision of "becoming a leading global coal industry chain integrator", and "building coal trading and coal supply chain service standards, optimizing the allocation of coal industry resources, promoting the efficient coordination of the industrial value chain, and promoting the construction and development of the coal market system"For its mission, it clearly proposed the strategic positioning of building a "coal trading and coal supply chain service platform".
Relying on the world's major coal producing areas such as China, Mongolia, North Korea, Russia's Far East, Vietnam, Indonesia, Australia, etc., and radiating the major coal consumption markets in Northeast Asia, it provides an open, efficient and public trust spot coal trading service platform through an intensive trading platform and electronic trading system, while introducing and integrating professional service providers such as finance and logistics,Provide integrated service solutions such as information, warehouse receipt pledge supervision, advance payment, settlement, inventory management, agency procurement, transportation agency, integrated logistics, laboratory testing, etc. for transactions.
Relevant knowledge
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Associated element
It refers to the elements enriched in coal seams and their surrounding rocks in organic or inorganic forms.Some elements are highly enriched in coal and can form industrial deposits, such as germanium rich coal, uranium rich coal, vanadium rich stone coal, etc., whose value is much higher than that of coal itself.
according toAssociated elements in coalIts properties and uses can be divided into three categories: beneficial elements, harmful elements and finger elements.The beneficial elements mainly include germanium, gallium, uranium, vanadium, etc., which can be used.The harmful elements mainly include sulfur, phosphorus, fluorine, chlorine, arsenic, beryllium, lead, boron, cadmium, mercury, selenium, chromium, etc.Sulfur is a common harmful element in coal. The content of other harmful elements in coal is generally low, but the harm is great. For example, arsenic is a toxic element.During coal combustion, sulfur is the main source of urban environmental pollution.Of course, if the harmful elements are collected and handled properly, they can also become useful wealth to people.The associated elements in coal have their own geochemical properties and are formed in different sedimentary environments.Therefore, facies and sedimentary environment can be judged according to the relative content of elements, the symbiotic association relationship of elements and the ratio of elements.
Coal liquefaction
Coal liquefactionIt is a technology that converts solid coal into liquid products (liquid hydrocarbon fuels, such as gasoline, diesel and other products or chemical raw materials) through chemical processing.Through coal liquefaction, harmful elements such as sulfur and ash can be removed to obtain clean secondary energy, which is of strategic significance for optimizing the structure of terminal energy, solving oil shortage and reducing environmental pollution.
Coal liquefaction methods are mainly divided into two categories: direct coal liquefaction and indirect coal liquefaction.
(1) Direct coal liquefaction refers to the process of transforming coal into liquid fuel through hydrocracking under the action of hydrogen and catalyst.Cracking is a reaction process that splits hydrocarbon molecules into several smaller molecules.Because the direct coal liquefaction process mainly uses hydrogenation means, it is also called the coal hydrogenation liquefaction method.
(2) Indirect liquefaction of coal is a process in which coal is used as raw material to gasify to produce syngas, and then the syngas is converted into hydrocarbon fuel, alcohol fuel and chemicals through the action of catalyst.
Coal to oil
There are usually two methods for coal to oil: direct liquefaction and indirect liquefaction.Direct liquefaction, also known as "hydrogenation liquefaction", mainly refers to the process of direct catalytic hydrocracking of coal under the action of high temperature, high pressure and catalyst, so that it can be degraded and hydrogenated into liquid oil products;The indirect liquefaction of coal is a process in which coal is first gasified to produce feed gas, then purified to produce oil through synthesis reaction.Direct coal liquefaction is to use chemical methods to add hydrogen to coal molecules to improve its hydrogen carbon atomic ratio.In the process of direct coal liquefaction, catalyst is the key to reduce the production cost and the severity of reaction conditions.
According to the processing method and quality specification of coal, it can be divided into five categories: raw coal, clean coal, granular coal, washing coal and low-quality coal.
raw coal
It refers to the coal excavated from underground or underground after screening, processing and removal of gangue, pyrite, etc.The raw coal produced by coal mines is also called raw coal.Including natural coke and inferior coal, excluding low calorific value coal, etc.
Clean coal
It refers to the products that are produced after selection (dry or wet) and meet the quality requirements.
Granular coal
It refers to the coal produced through screening or cleaning, with the lower limit of particle size greater than 6mm and ash content less than or equal to 40%.According to different particle sizes, it can be divided into washing medium block, medium block, washing and mixing medium block, mixing medium block, washing and mixing block, washing large block and large block, washing extra large block and large block, washing small block and small block, washing granular coal and granular coal.
Coal washing
It refers to the raw coal that has been washed, screened and processed to remove or reduce the gangue, sulfur and other impurities contained in the raw coal, and is divided into several varieties and grades according to different coal types, ash content, calorific value and particle size.The particle size grading is 50mm, 258mm, 20mm, 13mm and 6mm below.Coal washing can be divided into raw coal washing, blended coal washing, blended coal washing, blended fine coal washing, blended fine coal washing, blended fine coal washing, fine coal washing, powdered coal washing, etc.Except that the ash content of blended coal shall be less than or equal to 32%, the rest shall be less than or equal to 40%.
Low quality coal
It refers to various coal products with high ash content.Low quality coal is used for boiler combustion, which not only has poor economy, but also causes serious wear and tear of combustion auxiliary system and convection heating surface as well as increase of maintenance cost. Because of the high content of low quality coal ash, poor economy and large ash content, the heating surface is severely scoured and worn.
Conversion between analytical and laboratory benchmarks
The coal quality is seriously analyzed, and some benchmarks do not exist in practice, which are converted according to needs;Some benchmarks exist in practice, but for convenience, sometimes they are not tested, but converted according to the analysis and test results of known benchmarks, which is much simpler.
When conducting coal quality analysis and test in the laboratory, the coal sample used is the analytical coal sample.The analyzed coal sample is obtained after crushing and shrinking for many times, and its state is air dry.Therefore, when analyzing coal samples in the laboratory, the benchmark is the analytical basis (also called air drying basis).
The analytical basis test results of coal samples are directly measured in the laboratory, the most basic test results, and the basis for converting the analysis and test results of other benchmarks.
Conversion formula between various benchmarks:
Conversion of dry basis: Xd=100Xad/(100 Mad)%
Where: Xad -- assay result of analytical base;Mad -- moisture of analytical basis;Xd -- converted dry basis test results.
Coal quality
Coal quality refers to the physical and chemical characteristics and applicability of coal. Its main indicators include ash content, moisture, sulfur content, calorific value, volatile matter, lump coal limit rate, gangue content rate, coking property, cohesiveness, etc.
Product quality is the basis for the survival and development of an enterprise, and is the comprehensive reflection of all work of the enterprise.It is an important task of socialist production enterprises and an objective requirement of socialist production purposes to produce marketable products of good varieties.
Product quality refers to the sum of characteristics or characteristics of products, processes or services that meet the specified or potential requirements (or needs).Quality can be divided into narrow quality and broad quality.In the narrow sense, quality refers to product quality and related work quality;Broad sense quality not only refers to product quality and related work quality, but also includes the process quality and service quality of product formation. It takes product quality, process quality and service quality into consideration on the same important status, which further reflects that under the market economy, people attach great importance to product quality and quality plays a decisive role in competition.
From the definition of product quality, we can see that it contains two meanings: one is the characteristics and characteristics of the product itself, that is, the objective attributes of the product;The other refers to the degree of satisfaction of user needs during the use of the product, that is, the applicability of the product.When the two are organically combined, the product features and characteristics can be fully utilized, and the user needs can be fully met;The production purpose of society can be realized.If the smokeless lump coal is used in the production of synthetic ammonia, the characteristics and applicability of the convenient coal have reached a good combination.However, if smokeless lump coal is used as common boiler fuel, its applicability will be lost.It can be seen that the evaluation of product quality is determined by different needs of users[1]。
