lovesouthernsocial.com

Electricity production from coal can be harmful to the environment

Brian Patrick Tagalog image on Unsplash

Coal is a fossil fuel extracted from the earth through mining. Its origin comes from the decomposition of organic matter (remains of trees and plants) that accumulated under a layer of water millions of years ago. Burial of this organic matter by clay and sand deposits causes an increase in pressure and temperature, which contributes to the concentration of carbon atoms and expulsion of oxygen and hydrogen atoms (carbonification).

Coal is subdivided according to the calorific value and the incidence of impurities, being considered of low quality (lignite and sub-bituminous) and high quality (bituminous or coal and anthracite). According to the Geological Survey of Brazil, coal can be subdivided according to its quality, which depends on factors such as the nature of the organic matter that formed it, climate and geological evolution of the area.

Peat

Peat extraction takes place before the area is drained, which reduces its moisture. It is often deposited in the open to lose more moisture.

Uses: it is cut into blocks and used as fuel in furnaces, thermoelectric plants, obtaining fuel gas, waxes, paraffin, ammonia and tar (a product from which oils and other substances of great use by the chemical industry are derived)

lignite

It can occur in two forms, as a brown or black material, and has different names.

Uses: gasogens obtaining tar, waxes, phenols and paraffins. Ash from combustion can be used as pozzolanic cement and ceramics.

Coal

Hard coal can be subdivided into two main types: energy coal and metallurgical coal. The first, also called steam coal, is considered the poorest and is used directly in ovens, mainly in thermoelectric plants. Metallurgical coal, or coking coal, is considered noble. Coke is a porous material, light and with a metallic shine, used as fuel in metallurgy (blast furnaces). Coal is also used in the production of tar.

anthracite

It has slow combustion and is suitable for home heating. It is also used in water treatment processes.

Composition and application of coal

In any of its phases, coal is composed of an organic part and a mineral part. Organic is formed by carbon and hydrogen and small proportions of oxygen, sulfur and nitrogen. The mineral consists of silicates that make up the ash.

As it is subdivided into several types, the uses of coal are many. The main use of coal is as an energy source. According to the International Energy Agency (IEA), coal is responsible for 40% of the world's electric energy production. Coal is also used in the metallurgical sector.

Another type of charcoal found in nature is vegetable, which is formed from the carbonization of firewood. Charcoal is frequently used in industrial processes, but it is not a significant source for the production of electrical energy.

Incentives for the production of electricity from coal

Although non-renewable, there are strong incentives for the production of electricity from coal. The two main arguments in favor of energy production from coal are the abundance of reserves, which guarantee the security of supply and the low cost of the ore (compared to other fossil fuels) and the production process.

According to data from the National Electric Energy Agency (Aneel), world coal reserves total 847.5 billion tons. This amount would be enough to supply current coal production for a period of approximately 130 years. Another incentive is that, unlike oil and natural gas, coal reserves are found in significant quantities in 75 countries - although approximately 60% of the total volume is concentrated in the United States (28.6%), Russia (18, 5%) and China (13.5%). Brazil appears in the 10th position.

The world's biggest coal producers are China and the United States, according to World Coal Association, followed by India, Indonesia and Australia, respectively. In addition, most of the energy matrix, both in China and in the United States, is based on the production of electricity from coal, which is also representative in the energy matrix of other countries, such as Germany, Poland, Australia and South Africa.

However, despite the economic advantages, the production of electricity from mineral coal is one of the most aggressive forms of energy production from a socio-environmental point of view. Negative externalities are present throughout the entire production process, from the extraction of coal.

coal extraction

Coal extraction or mining can be underground or open-pit. This will vary depending on how deep the coal is found.

When the layer that covers the ore is narrow, or the soil is not suitable (sand or gravel), exploration tends to be carried out in the open. If the mineral is in deep layers, it is necessary to build tunnels.

According to Aneel, open-pit mining is the predominant form of ore extraction in Brazil, and also more productive than underground. This does not correspond to the international reality, in which exploration by underground mining prevails, equivalent to 60% of the world's coal extraction.

Acid mine drainage and tailings production are negative environmental impacts common to both types of extraction.

Acid mine drainage (DAM)

The mine's acid drainage is carried out by means of pumps, which release sulfurous water into the external environment, producing changes in the soil of a mineralogical order (formation of new compounds), chemical (reduction in pH) and physical (low water retention capacity and permeability), which vary according to the geology of the terrain.

Acid mine drainage is considered one of the most significant impacts of mining processes in general, according to the Ministry of Science and Technology report.

As a result of these changes in the soil, the quality of groundwater is also compromised. There may be a reduction in the pH value of the water, which contributes to the solubilization of metals and to the contamination of groundwater which, in case of ingestion, can affect human health.

Mitigation of chemical and physical soil problems caused by mining is the first step in the recovery of impacted areas.

Impacts of open pit mining

Excavations of large volumes of rocky soil generate visible environmental impacts on vegetation and fauna, being responsible for the degradation of large areas and visual pollution, not to mention the intensification of erosion processes. In addition, the use of machines and equipment also generates noise pollution (noise).

Impacts of underground mining

Regarding worker health, the main problem is Pneumoconiosis of coal workers (PTC). Pneumoconioses are diseases caused by inhaling particulate matter above the immune system's clearance capacity. It is the chronic exposure to the inhalation of coal dust, followed by the accumulation of dust in the lungs and the alteration of lung tissue.

PTC triggers an inflammatory process, which can develop massive progressive fibrosis FMP, a disease known as “black lung”.

According to the Ministry of Health report, there are more than 2,000 cases of pneumoconiosis diagnosed among coal miners.

Other impacts associated with underground mining are the lowering of the water table, which can contribute to the extinction of sources, the impact on the surface hydrological network and the vibrations caused by the explosions.

Charcoal processing

According to the Brazilian Association of Mineral Coal, beneficiation is the set of processes to which raw coal (run-of-mine - ROM), obtained directly from the mine, is subjected to the removal of organic matter and impurities, in order to ensure their quality. The treatment of coal depends on its original properties and intended use.

According to the Aneel report, the processing generates solid tailings that are normally deposited in the area close to the mining area and released directly into water courses or tailings dams, creating extensive areas covered by a liquid material. The toxic substances present in the tailings are diluted in rainwater (leaching), which, in the form of a fluid, slowly penetrates into the soil (percolation), contaminating the groundwater.

These tailings typically contain large concentrations of pyrite (iron sulfide - FeS2) or other sulphide materials, which contribute to the generation of sulfuric acid and to intensify the “acid mine drainage” process.

Transport

According to Aneel, transport is the most costly activity in the coal production process. For this reason, normally, the coal that is transported is only that which has a low content of impurities, and greater added economic value.

When the intended use of coal is the generation of electricity, the thermoelectric plant is built in the vicinity of the mining area, as occurs in the five coal-fired thermoelectric plants operating in the country.

From an economic point of view, it is more advantageous to invest in transmission lines to distribute the electricity already produced than in transporting coal over long distances.

For short distances, the most efficient method is conveyor belt transport. Pipelines are also used, through which coal, mixed with water, is transported in the form of slurry.

Power generation from coal

After extracted from the ground, coal is fragmented and stored in silos. It is then transported to a thermoelectric power plant.

According to Furnas, a thermoelectric plant is defined as a set of works and equipment with the function of generating electricity through a process that is conventionally divided into three stages.

The first step consists of burning fossil fuel to transform boiler water into steam. In the case of coal, before the burning process, it is transformed into powder. This guarantees the greatest thermal use of the burning process.

The second step is the use of steam produced under high pressure to turn a turbine and drive an electric generator. The passage of steam through the turbine causes movement of the turbine and also of the generator, which is coupled to the turbine, transforming mechanical energy into electrical energy.

The cycle is closed in the third and last step, in which the steam is condensed and transferred to an independent refrigeration circuit, returning to a liquid state, as boiler water

The energy that was generated is transported from the generator to a transformer via conductor cables. The transformer, in turn, distributes electricity to consumption centers through transmission lines.

Emissions

When coal is burned, the elements contained in it are volatilized (evaporated) and emitted to the atmosphere along with part of the inorganic matter that is released in the form of dust particles (flying ash).

here

Coal is a material with a high concentration of carbon. Thus, when burned, coal emits large concentrations of carbon monoxide.

Carbon monoxide is a toxic gas that is extremely harmful to human health and can, in cases of acute poisoning, lead to death. According to the Environmental Company of the State of São Paulo (Cetesb), the main route of poisoning by carbon monoxide is respiratory. Once inhaled, the gas is rapidly absorbed by the lungs and binds to hemoglobin, preventing the efficient transport of oxygen. Therefore, prolonged exposure to carbon monoxide is linked to an increase in the incidence of heart attacks among the elderly.

Also, once in the atmosphere, carbon monoxide can be oxidized to carbon dioxide.

Carbon dioxide

Carbon dioxide can be emitted directly from the combustion of coal and other fossil fuels, or it can be formed in the atmosphere from chemical reactions, for example, from the oxidation reaction of carbon monoxide.

Carbon dioxide is considered one of the main gases in the process of intensifying the greenhouse effect, being associated with the increase in global warming. And it is also one of the main types of gases emitted by burning coal.

It is important to point out that combustion is the phase of the coal production chain in which there is the greatest emission of carbon dioxide, but the tailings storage and storage phases also contribute to total emissions. However, according to the report by the Ministry of Science and Technology, the lack of knowledge of the ore storage time in each case is a limiting factor for the calculation of total emissions.

Sulfur

According to the report by the Brazilian Society for Energy Planning, of all emissions from coal-fired thermoelectric plants, the one that has caused the most concern is sulfur emissions. When burning, sulfur forms a series of gaseous compounds that are released into the atmosphere if there is no equipment for its capture. Of these, sulfur dioxide (SO2) stands out above all.

Sulfur dioxide (SO2) undergoes oxidation in the atmosphere and forms sulfur trioxide (SO3) which, in turn, when it binds to rainwater (H2O), will form sulfuric acid (H2SO4), giving rise to acid rain .

Acid rain has direct impacts on plant and animal life, especially aquatic. In vegetables, it leads to changes in pigmentation and formation and necrosis. In animals, it causes the death of organisms such as fish and frogs. Acid rain also causes damage to material goods, as it favors corrosive processes.

According to the Ministry of the Environment, the impacts of sulfur dioxide on human health may be related to the increase in the incidence of respiratory problems in general and asthma, which is indicated by the increase in hospital admissions.

Methane

Coal has a high content of methane (CH4). The combustion of coal releases methane into the atmosphere, which can be associated with water vapor and carbon dioxide and is considered one of the main greenhouse gases.

Methane is formed from the decomposition process of organic matter. For this reason, its occurrence is associated with fossil fuels.

It is important to note that despite the coal combustion process releasing significant amounts of methane into the atmosphere, methane emissions in the coal production process occur from the extraction of ore, especially in underground mines and in post-mining material storage, as can be seen in the report of the Ministry of Science and Technology

Nitrogen oxides (NOx)

Coal also has a high concentration of nitrogen. Therefore, coal combustion emits nitrogen oxides into the atmosphere. Combustion gases normally consist mostly of nitrogen oxide.When it enters the atmosphere, it is quickly oxidized to nitrogen dioxide.

Nitrogen dioxide, when binding to rainwater (H2O), produces nitric acid (HNO3) which, like sulfuric acid (H2SO4), also causes acid rain.

In addition, high concentrations of NO2 influence the formation of tropospheric ozone and processes of smog photochemical.

Particulate matter (PM)

According to Cetesb, particulate material is all solid and liquid material that remains suspended in the atmosphere because of its small size. Particulate matter also forms in the atmosphere from the aforementioned sulfur dioxide (SO2) and nitrogen oxides (NOx)

Particle size is directly related to the potential to cause health problems.

Mercury

In addition to the gases already mentioned, coal also contains significant amounts of mercury, which through combustion of the ore is volatilized into the atmosphere.

monday to EPA - Environmental Protection Agency coal-fired power plants are the largest anthropogenic source of mercury emissions.

Volatized mercury present in the atmosphere is incorporated into the rain cycle, reaching aquatic bodies and leading to environmental contamination and damage to aquatic life. Mercury contamination is also a public health issue, as the consumption of aquatic organisms contaminated by mercury can lead to acute poisoning, and in some cases lead to death.