Environmental Impacts Of Burning Coal Research Paper Sample
Coal is known as the main contributor to the rapid development of human civilizations. It is considered as one of the most essential rocks due to its economic and industrial value. However, research indicates that coal is a complex source of pollutants which include several severely harming pollutants. The process of burning coal has been the main cause of the worsening of pollution all over the globe. Coal burning emits minerals and substances that are hazardous and severely damages the air, water, and soil. This research includes an in-depth overview of coal as a source of energy, the pollutants it produces and the environmental effects it has. Furthermore, mitigation strategies for the coal will also be addressed with the intention to reduce the use of coal especially in the developing countries of the world. The report will also talk about the environmental hazards associated with the utilization of coal. Furthermore, the report provided a thorough discussion of the direct and secondary effect of coal processing. Some of the effects discussed in the report include melting of glaciers, emissions of mercury, acid rain, effects on soils and forests, smog, contamination of water, ocean acidification, effects of coal mining, impacts on wildlife, and air pollution. Lastly, the paper discussed the process of coal production.
1- Introduction: 1
a) Origin and formation of coal: 3
2- Environmental impacts of burning coal .4
a) Chemical reactions: 4
b) Temperature rise: Global warming and its effects: 5
i) Melting of glaciers: 6
3- Air Pollution: 8
a) Emissions of Mercury: 10
b) Acid Rain: 10
c) Effect on soils and forests: 11
d) Acid rain and burning of coal in china: 12
e) Smoke and Fly Ash 13
f) Smog 13
4- Water pollution: 14
a) Contamination of water: 15
b) Ocean acidification: 15
5- Effects of mining: 16
6- Impact on wildlife: 17
a) Washing and refining the raw coal: 19
b) Physical processes of coal washing: 20
c) Initial Preparation and Processing of fine and coarse coal: 20
d) The final preparation process of coal: 20
e) Separation of Particulates: 21
f) Electrostatic separator: 21
g) Fabric filters: 21
h) Wet particulate scrubbers: 21
i) Hot gas filtration system: 22
7- Conclusion: 22
8- References 23
Coal is a sedimentary rock formed by the accumulation, compaction, and fossilification of plants under the soil. It is a cheap and efficient source of energy and is widely used all over the globe to fulfill industrial and domestic needs (Scott, 2002). Its main purpose is for burning and heating like running steam engines, boilers, furnaces, and coal-fueled power plants. Furthermore, coal is considered as a rock of great economic and industrial value. Also, it has been acknowledged as the main cause behind the rapid development of human civilizations and Industrial Revolution. One example is the role of coal in strengthening the economy of the British Empire by being the main fuel first used to run the steam engines. This single advancement in technology gave advantage to Great Britain over other European nations (Clark & Jacks, 2007).
Presently, the economies of many industrial countries are largely dependent on the mining and utilization of coal. The annual industrial growth or productivity of a country can be calculated using the annual utilization of coal. Thus, one cannot deny the importance of coal in the human society as it has remained one of the most significant sources of energy (Thomas, 2012).
Coal burning has been a major contributor in the domain of environmental pollution. Pollution means “any substance or a chemical substance that adversely affects the environment or changes its state.” The coal pollution badly affects the rivers, oceans fertile lands, forests and the human society (Hill, 2010). Coal burning causes release of different compounds like carbon dioxide, sulfur dioxide, and nitrogen oxides which are significantly introduces air pollution that affects the lives of people. In addition, burning of coal also causes grave damage to the water resources. Water pollution due to coal burning occur when discharges or residues from the process contaminate water which in turn affects the life of aquatic organisms. Lastly, coal also has effects of land resources. Aside from producing solid wastes, burning of coal contaminates the soil with hazardous compounds which are persistent in the environment. Thus, giving rise to larger damage and disturbance to the natural environment of organisms (U.S. Environmental Protection Agency, 2013).
In the winter of 1952, about 4,000 people died in London due to suffocation caused by the excessive burning of coal in their fireplaces. This incident forced authorities to take the matter of coal seriously. Thus, coal was recognized as a hazardous agent with a great level of toxicity which can be defined as a foreign material that is not safe for every form of life on Earth (Clark & Jacks, 2007).
The chemical and physical nature of the chemical substance also affects a degree of pollution. Some chemicals are less toxic with short residence time in the environment while some chemicals are extremely toxic with long residence time. Unfortunately, coal emits varying amounts of dangerous heavy metals and non-metals like arsenic, lead, nickel, mercury, tin, antimony, cadmium and some radio isotopes of thorium as well as strontium which enters directly into the environment. When coal burns, all of these chemicals escape out of the coal which pollute the environment (Clark & Jacks, 2007).
During the start of Industrial Revolution, countries especially the USA and Great Brittan drew their attention to coal extraction and utilization. It was the source of their rapid growth and strength. However, as years passed, people started realizing hazardous effects of coal burning on the environment and their lives.
Upon identification of the toxicity associated with coal, authorities in the western world have decided to ban coal mining and burning. However, due to the accessibility and affordability of coal, underdeveloped countries continued using coal in a wide range of industrial, transportation and domestic processes.
Origin and formation of coal:
Coal is a fossil fuel which is formed when the burial process results in exceeding temperature and pressure. It is from long compaction alteration and accumulation of trees and branches buried beneath the soil as a result of natural processes. Coal is a complex compound composed of both organic and inorganic compounds. After remaining in the buried state for millions of years, the composition dries up and produces what we now call as coal.
Originally, deposits of coal were mainly found near peat swamp where plants was the source of organic matter. These remains of the plants and trees are called coal. It is a hydrocarbon based rock which can be qualified by the percentage of sulfur present in it. Coal of good quality has less amount of sulfur whereas a high quantity of sulfur depicts low quality of coal.
One of the theories concerning the origin of coal is supported by geological proofs which indicate that coal formation is the byproduct of burial processes which lead to compaction and eventually coal formation in high temperature and pressure. Throughout the processes, geologic processes result in changing the litho-structural dimensions of the globe. As a result of these activities, wood units continuously emerge and destroy.
Environmental impacts of burning coal:
The burning of coal has hazardous effects on the environment. Studies on the effects of burning coal have revealed that it directly or indirectly affects all aspects of nature, i.e. water, land and air. It also affects the lives of many species like fish, birds, mammals and men.
When coal burns, in excess of oxygen, its chemical reaction is as follows
Cx + O2 --> H2O +CO2
or coal + oxygen --> water + carbon dioxide
or coal + fire (oxidization) --> water + carbon dioxide
The scientific study indicates that the complete combustion of coal is less dangerous as compared to the partial combustion. The unburnt carbon particles serve as the smoke particles. These smoke particles cause a lot of pollution in the atmosphere along with several other diverse healthcare issues. Research indicates that the combusted coal is also a main source of smog formation (Wall, 2009).
Coal also contains contamination of other dangerous pollutants like mercury, arsenic, sulfur and many more. When the coal burns, these pollutants escape into the air and adversely harm the environment along with all of the ecosystems which are in harmony with the environment. There are several reporting of instances leading to the emissions of pollutants like arsenic and mercury. All these toxins eventually result in polluting the hydrosphere and is a major cause of bio-magnification (Wall, 2009).
There are several environmental causes associated with the consumption of coal. Temperature rise is one of them. When the coal burns, it emits carbon dioxide which is one of the most threatening greenhouse gases. These gases trap the amount of energy that enters the atmosphere from the sun. Coal is a direct contributor of greenhouse gasses which causes an average rise in temperature which eventually disturbing the whole ecosystems and negatively influences the environment.
Temperature rise: Global warming and its effects:
Carbon dioxide is the major product of coal combustion. This carbon dioxide serves as a greenhouse gas. When sunlight passes from the CO2, it absorbs the thermal radiations and radiates them in all directions. The excessive exposure to thermal radiations causes rise in the temperature. This phenomenon is called the greenhouse effect.
There are also some other greenhouse gases that cause the greenhouse effect, but CO2 has a major share in the greenhouse effect. It is evident from the studies that 56.2% of the Global Warming is caused by the CO2 burning from fossil fuels, especially coal. Out of this, 25.9% of CO2 comes from the coal fueled power plants. On a large scale, an excessive amount of CO2 in the air is causing worldwide increase in average global temperature. This worldly increase in temperature is termed as Global Warming (Velikova, 2000).
Most of the CO2 in the world is produced by the natural systems and absorbed by the natural systems (forests, oceans, soil). According to recent research, human activities produce almost 6.6 billion tons CO2 each year, and natural systems are only able to absorb less than half of this generated CO2. Therefore, it is appropriate to say that more than 3.3 billion CO2 adds into the atmosphere every single year. That’s why CO2 level in the atmosphere today is approximately 370 ppm and it was 280 ppm in the Pre-Industrial time (Crichton, Nicol, & Roef, 2009).
The earth’s observed temperature was raised by 0.74±0.18 °C from the years ranging from 1996 to 2005. It is important to notice that today’s average temperature of the earth has significantly risen compared to the Ice-Age time’s temperature (Trenberth et al, 2007).
It is evident from this fact that, remarkable effects occur from the minor increase in average temperature. Earth’s temperature is consistently increasing in all continents except Antarctica, but ice melting is also occurring there. This global increase in the climatic temperature is the main cause of glacial melt on the Polar Regions which eventually result in high sea levels which abruptly alter the earthly balance.
Melting of glaciers:
The rise in temperature is dangerous for the whole environment. It is particularly threatening for Cryosphere regions. Cryosphere are the regions covered with ice. The rise in temperature causes melting of ice-glaciers. This melting causes increase in floods and ocean storms. The melting of ice also causes an increase in the water level of the oceans.
The rise in water level of oceans causes depletion of coastal areas. The melting of Alaska’s glacier is a primary example of this fact. The average temperature of Alaska has increased to 3oC. It is a dramatic change. This dramatic increase in temperature is causing rapid melting of ice glaciers in Alaska. Studies were conducted in Alaska State University and it concluded that 9% of ocean water level increase is caused by melting of Alaska’s glaciers. The increase in arctic temperature is badly affecting the lives of many people and animals. For example, melting of glaciers is destroying the natural habitat of the ice bear.
The temperature rise also has effects on the weather. The precipitation process is now accelerated due to global warming. The increase in precipitation generally influences the rainfall pattern in the different regions of the world. The projections of future rainfall suggest the reduction of rainfalls in subtropical regions and increase of rainfalls in equatorial regions.
In simply terms, the dry regions will become drier and wet regions will become wetter. This change in the environment will badly affect the life of people living in those regions.
There is another environmental impact of temperature rise, which is extreme weather. Extreme weather means, extremely hot and cold temperature. This extreme change in atmosphere is with environmental calamities like floods, droughts, and storms.
When coal burns in the air, it produces CO2 as well as some other gases and particulates which badly contaminate the air. They are nitrogen oxides (NOx), sulfur dioxide (SO2), mercury, particulate matter and fly ash. These pollutants are the source of acid rains, smog and other forms of air pollution. The air pollution causes acute respiratory diseases, chronic bronchitis, asthma, and premature death and haze obstructing visibility. Very small amounts of mercury and other heavy metals like arsenic are also present in the coal. Exposure to mercury can cause brain and heart damage. Air pollution is harmful to life on earth.
Coal burning and its waste products ( which includes, bottom ash, fly ash and boiler slag) approximately release twenty toxic compounds, which are lead, mercury arsenic, , nickel, beryllium, cadmium, vanadium, , barium, copper, molybdenum, chromium, zinc, selenium and radium, which are dangerous for the environment. Although these substances are trace elements enough coal is burned so, that significant quantities of these substances are in the atmosphere.
In the combustion of coal, the reaction between air and coal produces carbon dioxide, sulfur dioxide (SO2), and oxides of Nitrogen (NOx). Due to hydrogenous and nitrogenous constituents of coal, nitride and hydrides of sulfur and carbon are output during the combustion. They include sulfur nitrate (SNO3), Hydrogen cyanide (HCN), and other toxic impurities.
Nitrogen oxide and SO2 react in the atmosphere to form ground-level ozone (O3) and fine particulate matter. These are transported to other regions through air, and make it difficult to achieve healthy levels of pollution control for other states.
Coal fired power stations use wet cooling towers. These cooling towers produce fog and drift. These pollutants have severe effects on the environment. Drift contains suspended inhale-able particulate matter. If cooling towers are linked with the sea sodium salt starts depositing on the nearby land of the sea that increases the alkalinity of the soil. This rise in alkalinity of water results in the corrosion of nearby structures and the reduction in fertility of the soil.
Underground coal beds sometimes catch fire. Exposure of coal beds to the open environment increases the risk of fire. The weathered coal also causes an increase in temperature of the earth. All fires on solid coal are by surface fires by people or lightening. A spontaneous combustion occurs when coal oxidizes in the absent of sufficient air flow for dissipating heat, this mostly happens in waste piles and stockpiles, but seldom happens in underground bedded coal. Coal fire has a reasonable contribution to air pollution.
Noxious fumes and smoke enter the atmosphere from these fires. Coal-layer fires can burn underground for many years, and threatens demolition of homes, forests, roadways and important infrastructure. A famous coal-layer fire was one that led to the permanent removal of Centralia, Pennsylvania, United States.
Approximately 75 Tg/S of Sulfur Dioxide (SO2) is per year from coal burning in the U.S. Sulfur dioxide oxidizes to H2SO2 in the atmosphere. This gaseous H2SO2 scatters radiations of the Sun., hence an increase of H2SO2 in environment causes a cooling effect on the climate, which covers some portion of the warming caused by greenhouse gases. SO2 emission also contributes to the extensive acidification of the environment.
Emissions of Mercury:
Coal combustion is the major source of mercury emission in the atmosphere. Winds are depositing the mercury in different places like New York, Catskills Mountains, and Great Lakes. After the deposition of mercury in land and water resources, some microorganism convert it to a more deadly and persistent form known as methylmercury which destroys both people and wildlife that depend upon freshwater fish. Methylmercury accumulate in different organisms like fishes, shellfishes, and even humans. Due to the difficulty of the breaking down of methylmercury, the amount of mercury accumulates as it moves up the food chain. In Catskill Mountains, bald eagles that have eaten methylmercury contaminated fishes suffered from mercury poisoning. Another example of mercury emission is the pollution of mercury in Great Lakes. The high mercury content of the lakes was due to the large number of coal-fired power plants surrounding it. Since a large region depend on the Great Lakes for their survival, the consequences of mercury emission also affected a large number of people in the area (Stamper, Copeland, & Williams, 2012).
Acid rain is a term used for the rain containing acidic compounds like sulfuric and nitric acid. Sulfur dioxide (SO2) and Nitrogen Oxides (NOx) are emitted during coal burning due to the burning of sulfur and nitrogenous compounds present in the coal. When they react with water vapors, they produce sulfuric acid and nitric acid. These acids are the cause of acid rain. Acid rain destroys forests, agricultural lands, and acidifies ground water resources. Acid rain also erodes buildings and pottery (Likens, Discroll, & Busso, 1996). The adverse effects of acid rains are described below.
Surface water and soil are the sinks of acid rain deposits, but increase in the acid deposits decreases capacity of surface water to dilute these deposits. Acid rains lower the pH of water and thus badly affect the habitats of fish, birds and humans. Acidic water also increase the mobility of heavy metals. These heavy metals like mercury, cadmium, and arsenic are hazardous for the people who drink that water or eat the fish from that particular water.
This reduction of pH causes increase in aluminum deposits in the water. (Gorham, E, Bayley, & Schindler, 1984) aluminum is dangerous for fish. It deposits on the gills of fish and reduces its ability to get oxygen from the fresh water. Fish that suffer from these deposits on their gills eventually die. It is that, eggs of some species of fish do not hatch under the low pH water. In 1990 The USA’s National Acidic Precipitation Assessment Program (NAPAP) mentioned in its reports that surface water acidification had adversely affected many species of fish, snail and crustaceans in the 15% lakes of New England. Adirondack lakes of New York are suffering even more. Approximately 40% of the lakes found in New York are chronically or episodically acidic (Schindler, 1988). The reduction in the fish population results from an increase of aluminum in water bodies and decrease in PH. Acid deposits also store in the winter snow, and when snow melts after the winter, the acid soaks into the soil or dissolves into the water.
Effect on soils and forests:
The acid rain is the cause of acidity of soils. This increase in acidity is hazardous for the plants. Acid deposition on soils decreases the immunity of trees which limits their ability to withstand extreme weather conditions. Studies have been conducted for the investigation of the cause of this problem and proved that the acidified soils are a serious threat to the population of plant life (Velikova, 2000).
It has been reported that the major cause of this decrease in the immunity of trees is the decrease in the calcium and magnesium level in the soil (Velikova, 2000). Plants utilize the calcium and magnesium of the soil for their growth and strength. But acid rain leaches out the whole calcium and magnesium from the soil. This reduction of calcium and magnesium causes destruction of forests. Acid rain also increases the concentration of aluminum in the soil. Aluminum is dangerous for the plants because it penetrates onto the cell membrane and stops the uptake of minerals through the water from the soil. The increase in aluminum deposits in the tissues of trees cause the death of trees.
The soil biology is adversely affected due to low pH rain water. Many microbes are killed due to low pH Low pH water mostly denatures enzymes of microbes, and they become inactive (Velikova, 2000).
Acid rain and burning of coal in china:
China is the second largest economy in the world. China also has the large reservoirs of the coal. 90-95% energy requirement of China are fulfilled by the burning of coal. China is new building a coal based power plant in each week. The burning of coal is the cause of high acid depositions in China. It was said in the report that in one-third of china pH of rainfall was lower than 5.6. It is that, SO2 emissions increased 27% from 2000 to 2005. Thus making China a big emitter of SO2. This acidic rainfall is causing destruction of forests of pine in the country. (Ando, et al., 1998). The SO2 emissions from the burning of coal is one of the major contributors for the production of acid rain. The rain becomes acidic when the oxides of sulfur and nitrogen become sulfuric acid and nitric acid upon its mixture with rain. The acidic pH of the rain is known to have corrosive characteristics. Thus, leading to the destruction of pine trees (Sawyer, et al., 2003).
Smoke and fly ash:
Burning of coal also contributes to the emission of particulate matter. Particulate matters are very fine solid particles of very small size that cannot be seen through the naked eye. Air carries these particulate matters. When coal burns, very small particles of carbon are and these particles are through air and move from one place to another. The air containing these particles of carbon and other dangerous compounds is termed as smoke. Most of the smoke is from the power plants and other incineration places.
Burning of coal also produces fly ash. Fly ash contains reasonable concentration of carbon, hydrocarbon metal oxides, and silicon dioxides. It also traps dioxins produced during combustion. Silicon dioxide only becomes dangerous when found in glass windows but its presence in air or blowing sand has also reported hazardous effects.
Most of the particulate matter is from domestic and inefficient combustion. The amount of fly ash depends upon the efficiency of the combustion process. A highly efficient combustion produces small amounts of fly ash whereas less efficient combustion leads to large amount of fly ash.
Smog is the combination of two words smoke and fog. It is by the dissolution of water droplets, particulate matter or smoke in the air. The product of this combination is smog. Smog mostly contains particulate matter largely and some other hazardous photochemical oxidants like Peroxi Acyl Nitrate (PAN), Nitrogen dioxide and a reasonable amount of ground level ozone (O3). We also sometimes refer it as photochemical smog. Smog also contains reasonable amount of sulfur dioxide (SO2), soot and carbon monoxide (CO).
A major source of smog is the intensive industrial and domestic burning of coal. Improper burning of wood and burning of coal containing a large quantity of sulfur are major contributors to the smog. Inefficient burning produces Particulate Matter and increased quantity of Sulfur dioxide. These two compounds form 70-80% part of the smog (Giebel & Seemayer, 1984).
Smog badly affects the life of people especially in the big cities where industrial activities are high. It causes severe health problems like damage of lungs and respiratory system, heart problems and obstruction of visibility. Smog also causes suffocation and decrease in ground level oxygen. Too much decrease in oxygen level and increase in smog sometimes causes death (Giebel & Seemayer, 1984).
Water is an essential element for life on earth. Approximately 70% of the earth is composed of water whereas 30 percent is land. Every living creature depends on water. Water is a habitat of about three-fourth of bio-mass. People use water for drinking, washing and cleaning purposes. The burning of coal also adversely affects the quality of water.
The hazardous products of coal combustion process badly contaminate drinking water risking the lives of many people drinking that water. (Goel, 2006).
Contamination of water:
Coal burning has a major contribution in the contamination of drinking water. The water of lakes, rivers, and other areas is getting polluted from the dissolution of heavy metals and sludge of the combustion process. Whenever the coal fragment is burnt, several toxins enter the atmosphere which eventually settles down in the water bodies. Later the contaminants are consumed by the aquatic lives which results in bio-magnification. Coal burning causes emission of nitrate and sulfates. These are acidic in nature. These nitrates and sulfates convert the heavy metals into a water soluble state. These soluble heavy metals are hazardous for the people who drink that water. It is also dangerous for the fish and other fish species present in water.
Coal contains a reasonable amount of mercury, arsenic, and sulfur in it. These metals are dangerous for the health. Mercury is dangerous for the brain. It severely affects growing children because it stops the growth of their intellectual. Children who drink mercury- contaminated water are usually suffering incomplete or abnormal growth of their mind and intellectual. Arsenic is toxic in nature. It lowers the immunity of people and reduces the life of people.
On a large scale, seawater is also acidified from the high dose of CO2 produced from the burning of coal in the large industrial and power scales. Oceans are the source of income and food for 40-50% of world population. Seafood has a major share in world food supplies. The economy of many countries like Brazil, USA, and Zimbabwe are largely dependent on the ocean.
The acidity of water increases with the increased absorption of CO2. The rise in acidity causes the death of many species of fish and other creatures. It also increases the aluminum level in the water. As stated earlier, aluminum is dangerous for the respiration system of fish. So, it causes death of fish. Heavy metals start dissolving in water due to rising in acidity of water. The compounds of these metals and other toxic chemicals concentrate in many species of fish. When birds or men eat this kind of fish, they suffer diseases, toxicity and deaths from such pollutants.
The acidification of oceans is alarming for many species of fish, snail, and other sea creatures. It is evident from the studies that the number of fish and other marine creature is near industrial cities of the world. So it is the requirement of time to decrease the concentration of CO2 from the environment by minimizing the coal burning process.
Effects of mining:
Mining is the process of extracting the metals and other useful materials from the earth by digging it. Most of the coal in the world is obtained through mining. Coal mining causes destruction of the normal landscape. Another dilemma of coal mining is escape of methane gas. The Methane gas has 25 times more potential for global warming than CO2. The escape of CO gas also sometimes causes death of miners in the coal mines. So coal mining itself is a very dangerous process.
Coal mining also has some adverse effects for the acid mine drainage. When rocks are broken down, air passes through their cracks. This air interacts with the rocks of iron pyrite; they produce SO2. This sulfur dioxide reacts with the moisture to form sulfuric acid. This sulfuric acid reacts with other rocks of heavy metals and dissolved them in it. With the passage of time, acid concentration increases in the mine. This acid flows out of the creeks of the mine and enters the land. It sometimes reaches the underground water resources and pollutes them. This much exposure of acid to the land causes destruction of land. It destroys the plants and reduces the fertility of the land.
The remains from coal mining are also very dangerous. The remains are at the end of coal extraction. These remains are mostly hazardous in nature like pyrites, oxides of heavy metals and other residue materials. When these materials are exposed to air, moisture and sunlight cause several hazardous chemical reactions to occur. These reactions cause an increase in toxicity of lands, air, and water resources.
Impact on wildlife:
Coal mining has indirect and directs impacts on environment. The effect on wildlife starts primarily from removing, troubling, and redistributing the surface of the land. Some effects are temporary, and limited to the mining place; others have extensive, lasting effects.
One direct impact of mining on wildlife is demolition or dislocation of species in regions of diggings. The spoil and pit areas of a mine are not able to provide food and cover to the species. Many mobile species like game animals, birds, and predators usually left these places. But some animals are sedentary like invertebrates, reptiles, and small mammals. The communities of microbes present in the soil are also upset by the moving storage and redistribution of soil (Huta, 2014).
Aquatic animals habitats are usually destroyed by the surface mining and it may happen many miles away from the mining site. Contamination of surface water with sediments is the common effect of surface mining (Huta, 2014). The concentration of sediments on water may increase several times with the use of strip mining.
The effect of sedimentation of water on the aquatic wildlife depends largely on the concentration of sediments, types of species and their count in the water. High concentration of sediment causes direct killing of fish, burying of spawning beds reduction in transmission of light through water, variation in temperature slopes, filling of pools, spreading of flowing streams over shallower, wider regions, and reduction of aquatic organisms used by other species as food. These variations badly affect the habitats of important organisms and even sometimes boost the habitats for undesirable organisms (Endangered Species Coalition, 2014).
Present conditions are already crucial for some freshwater fish in the USA and causing their extinction due to increased sedimentation of their habitats (Huta, 2014). The severe pollution caused by sediment of drainage occurs within five to twenty-five years after mining. Even in some regions, stagnated piles of spoil are continuous to eroding even 50 to 65 years after mining. (Pond, et al., 2008).
Some acid forming materials like pyrites, and nitrites etc., are exposed as a result of surface mining. These materials can severely destroy the wildlife by eliminating their habitats and even directly killing of some species. They also reduce productivity, growth and reproduction of many species of organisms that live in water. The presence of acids, heavy metals and high alkalinity badly affects the wildlife in some regions.
The residence time of acid deposits in the environment may be long. It is that the time required for complete leeching of exposed acidic materials in Eastern USA is almost 300 to 800 years (Johnson, 1982). Various technologies are also available for mitigating the pollution and its effects on the environment. These technologies are useful for controlling the emission of coal based pollutants. We cannot completely give up the use of coal because it is of very high economic value. It is not a good idea to completely stop the utilization of coal in the industry and domestic sector.
A good idea is to control the impacts of its pollution by reducing its toxic hazardous chemicals. When we go search for different methods for reducing the adverse effects of coal on the environment, first thing to think about is the efficiency of coal combustion process.
If we increase the efficiency of the combustion process, the emission of hazardous elements also reduces. Researchers are putting their efforts for many years for controlling and improving the efficiency of coal combustion process. Today, the modern world has employed many new techniques for improving efficiency of combustion. Despite efficiency of combustion, there are also other alternatives to consider; which are the purification of the coal and controlling the emissions. The selection of any alternative depends upon the cost, condition, location and age of power plant, furnaces or stoves, etc. (Wall, 2009).Some alternative technologies for reducing the coal pollution are described below.
Washing and refining the raw coal:
The process of washing and refining of raw coal is becoming more famous day by day, thus, it is considered as one of today’s biggest technology. After mining, raw coal contains impurities like clay, sulfur, arsenic, mercury and other toxic chemicals. These chemicals are washed out of the coal in order to increase the values of coal and to decrease the hazardous pollutants. There are two categories of methods used for washing the coal; physical processes and chemical processes. Physical processes are widely used now days. Chemical process is in the stage of development and research. Their cost, efficiency and safety limits are unknown so we will limit our discussion only on the physical processes.
Physical processes of coal washing:
There are several techniques which are used under the categories of physical processes of coal washing. But all these techniques follow four general steps; preparation, processing of fine coal, processing of coarse coal and final preparation. A brief description of all these processes is described below.
Initial Preparation and Processing of fine and coarse coal:
The coal is first collected, transport, crushed, and screened to fine and coarse coal before being processed.
There are two types of coal; fine coal and coarse coal. The fine coal is in the form of fine particles whereas coarse coal is long needle like particles of coal. Methods for processing or filtering the both types of coal are similar. Only parameters vary for each type of coal.
The general method for processing the coal are passing upward currents of fluid or water for dissolving the coal in it. Hence, light particles of coal are removed, and dense, heavy particles including impurities are left un-dissolved. The coal filtered in this process is then subject to drying in the final preparation process.
The final preparation process of coal:
The primary objective of the process is the dewatering of the coal thereby reducing the weight, problems of freezing and raising the heating value. First step in this process is dewatering of coal. In this phase water is removed from coal by using thickeners, cyclones and screens. In second step, thermal drying of coal is done. Fluidized beds, multi louvered or flash are mostly used for thermal drying process. Fluidized bed is a cheap and technology less sophisticated drying process. But its efficiency is low. But it is a good alternative for poor and underdeveloped countries (Markuszeweski, 1984).
Separation of Particulates:
The particulate matter is the major pollutant of the coal combustion process. There are several technologies used to control the emissions of particulate matter into the environment. Some technologies are described below.
Electrostatic separators are widely used for controlling the emission of particulate matter into the environment. In these separators, particles are charged by using the electric field. These particles are then easily removed from the flu gas by attracting them toward oppositely charged plates.
In fabric filter separators, particulates are filtered through the gas by passing them from the tightly woven fabric. This process is highly efficient as it removes 99% particulate matter from the gas. And both ES and fabric filter process minimally disturbs the filtration process.
Wet particulate scrubbers:
These scrubbers are used to remove both particulates, as well as SO2 from the flu-gases. In this process, water droplets are injected into the gas in order to form wet by-product. This wet by product contains sulfur oxide and particulates of smoke. A small amount of lime is also added into the water for removing SO2 more efficiently.
Hot gas filtration system:
Hot gas filtration system operates 200-900oC higher temperature and pressure (1.3MPa) then previous filtering procedures. This process doesn’t require the cooling of gas. It is suitable for the modern combined cycle power plants like integrated gasification combined cycle power plants. A range of hot gas filtration technologies has under development and research for many years. More research is required for widespread commercial use of these technologies. (World Coal Association, 2011)
Coal without any doubt is harming the environment in a way no other pollutant does. The substances emitted when burning coal like carbon dioxide, mercury, and arsenic are harmful pollutants capable of destroying the environment and disturbing the natural balance between the ecosystems and the environment.
Starting from glacial melt to the average increase in geothermal gradient, coal is responsible for almost every environmental issue. Research clearly indicates that coal throughout the course of human development has polluted the environment and human for a very minimal gain have ruined their habitats and environment.
Now it is the federal responsibility to put a stop to every type of coal combustion or coal related activities. Starting from the engines to heavy machinery in the industrial sector, every coal combustion activity must be brought to an end because this is the only chance to reverse the impact of coal.
We have already lost tons of species; our global temperature is on a continuous rise, and we are facing adverse environmental issues. Starting from the thinning of the ozone to several rapid climatic changes, coal is the main cause.
It is so unfortunate that most of the nations in the contemporary settings are not focusing on mitigating coal use. In most of the under-developed countries, coal is still used as the primary source of energy following its easy accessibility and cost. Coal use for the industrial usage must be banned on international levels because without it, it is almost impossible to cease the use of coal.
Moreover, social representatives and the influential from all over the world must play their role in minimizing the extent of coal use. A lot is required in the R&D sector to seek new fuel or energy alternatives. It is also unfortunate that most of the people are not aware of the damages coal does on the environment. It is strongly recommended to launch international campaigns to make the habitants of the planet aware of the adverse environmental impacts of coal because only by doing so we can save the environment for generations to come.
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