Coal is the most widespread kind of fuel. Coal covers about 23% of world’s energy needs. About 39% of electricity is produced with this source of energy. Coal is extremely important for production of steel. About two thirds of steel is manufactured with the use of coal. According to International Energy Agency, during next 10 years the use of coal will increase to about 43%.
It should be noted that coal is considered the dirtiest fossil fuel. During the process of burning fuel, more than 10 billion tons of carbon dioxide is emitted annually into the atmosphere. The main sources of these emissions are power generation plants and factories (Dowdey n.p.; World Nuclear Association n.p.).
Use of coal has doubled during the last 10 years. According to the statistics, within the nearest 10 years coal will be the most commonly used source of energy in the world. Popularity of coal is conditioned by its low cost and high volumes spread all over the world. However, during the combustion of coal, carbon dioxide, nitrogen dioxide ad sulfur dioxide are emitted, which are the main causes of the greenhouse effect.
The main task of modern science is to develop technologies of fuel combustion, which will help reduce carbon dioxide emission and its harmful effect on people and the environment. Decreasing of harmful effect caused by mining and burning of coal will improve current environmental situation, thus allow leave clean and safe place of living for future generation. Scientists try to minimize the impact on a climate by implementation of various clean coal technologies.
Scientists are searching for ways not only to decrease harmful effect of coal use, but to make new processes economically competitive.
Process of coal burning is associated with the release of various harmful wastes. Modern clean coal technologies control these wastes and decrease their amount. These technologies can be divided into two categories: repowering and retrofit. Retrofit technologies are used for decreasing harmful emissions, but they do not increase efficiency of factory. Repowering technologies are developed for increasing the lifetime of factory by reducing the level of emissions and improving fuel efficiency while increasing its overall capacity.
There are different types of clean coal technologies:
Cleaning coal by means of washing is used for decreasing sulfur dioxide and ash emissions during the process of burning.
Fabric filters and electrostatic precipitators are used for removing ashes from fuel gases. These technologies are very popular because they help remove up to 99% of ash.
Desulfurization of fuel gases decreases about 97% of output of sulfur dioxide, thus minimizes its harmful effect on the environment.
Factories, which use coal burning technologies, use low-NOx burners, which allow them decrease nitrogen oxide emissions by about 40%.
Pressurised Fluidised Bed Combustion (PFBC) and Integrated Gasification Combined Cycle (IGCC) can cause elimination of harmful emissions by about 50%.
Implementation of Ultra-clean coal (UCC) technologies decreases sulfur emissions to extremely low amounts and ash below 0,25%. Thus, pulverized coal can be used in the marine industry for large engines as an environmentally friendly alternative to heavy fuel oil.
Use of various technologies of gasification, such as underground coal gasification (UCG) in combination with oxygen and steam turns coal into hydrogen and monoxide. This technology of coal gasification is usually used in non-mined coal seams. During underground coal gasification, injection of oxidizing agent (air r oxygen) is performed. Thus, manufactured gas comes to surface through drilled production wells.
The above technologies are very expensive, and their implementation considerably increases the cost of clean coal.
However various legislative regulations are adopted for decreasing of harmful effect of using coal. For example, Kyoto Protocol is created for implementation of projects and performing activities which are aimed at decreasing of harmful substances emissions. Humanity should think about the environment and its saving notwithstanding the increasing energy demand.
Technologies of carbon capture and storage or sequestration (CCS) plays a significant role in producing clean coal. Capture technologies are based on carbon dioxide captured from the gas stream. They are usually implemented at the power plants. Captured carbon dioxide is stored and used for enhanced oil recovery (EOR) operations. Such technologies are implemented in West Texas and North Dakota. More than 72 million tons of carbon dioxide are transported for the needs of the oil industry in the USA annually. Such carbon dioxide is used for producing more than 280,000 barrels of domestic oil daily, or about 6% of production of crude oil in the country.
Additionally, ocean storage is used for injection liquid carbon dioxide into the water on the depth from 500 m to 3000 m. Liquid carbon dioxide dissolves under the water pressure conditions. However, this method has some negative effects. During its implementation, pH is decreasing and this harms ocean inhabitants and plants (Dowdey n.p.).
Storage of carbon dioxide should be performed very carefully in order to eliminate any possible harm to the environment.
A National Enhanced Oil Recovery (NEOR) program has been adopted in 2011. It improves realization of carbon dioxide EOR potential, thus enabling energy security for the country. NEOR is part of environmental and economic strategy of the USA. Its central recommendation is tax crediting of companies, which realize procedures for capturing of carbon dioxide.
Also, special project, FutureGen, was developed and adopted for development, building and operating of a hydrogen production plant in pursuit of having emission-free coal-based electricity. This project unites such initiatives as gasification of coal (IGCC) factories and plants with using of water-shift reactor for producing carbon dioxide and hydrogen. FutureGen provides separating about 700,000 tons of carbon dioxide annually, by capturing approximately 90% of carbon dioxide.
Process of gasification transforms coal into burnable gas with the maximum amount of potential energy. The first step of gasification in Integrated Gasification Combined Cycle (IGCC) is pyrolysis, whereby coal without oxygen yields char rich carbon and hydrogen volatiles at the temperature of 400C and higher. Next to this, at 700C the char is transformed into gas, without any ash. Being accompanied by oxygen, the gas is not nitrogen diluted.
The main chemical reactions are:
C + O2 yields CO,
C + H2O yields CO & H2,
CO + H2O yields CO2 & H2 (the water gas endothermic reaction).
These reactions lead to zero-emissions of coal because the amount of various emissions (like carbon dioxide) is very low. This way of modernization of coal process increases the cost of electricity by some 10%. Hence, this technology is rather competitive with conventional coal combustions processes currently used.
Implementation of clean coal technologies has both positive and negative sides.
Clean coal technologies considerably reduce emission of carbon dioxide and sulfur. Harmful effect on the environment and people’s health also decreases. Obtained carbon dioxide is used in oil recovery technologies, which decreases the cost of oil. Funds, which are necessary for implementation of clean coal technologies, are significantly lower as compared to funds necessary for manufacturing of gas and nuclear sources of energy. Clean coal technologies eliminate devastating effect of coal mines on the surrounding environment, as well as radiation from coal factories and plants. Implementation of clean coal technologies will lead to psychological understanding that people reduce harmful effects on the environment, climate and their lives. This understanding fosters the idea of leaving clean planet to future generations.
Implementation of clean coal technologies supposes future use of coal that is nonrenewable source of energy. New technologies used for decreasing of carbon dioxide and sulfur emission are expensive and lead to growth of cost of the end product. Currently, these technologies are only developing and cannot totally displace carbon and sulfur from coal (Siegel n.p.).
Implementation of clean coal sources is aimed at eliminating emission of smoke, grime, various disasters and destroying of natural landscapes. One of the methods of providing clean coal energy is Underground Coal Gasification (UCG). This method significantly decreases negative natural effect and at, the same time, it is in compliance with the NSPE code of ethics.
Underground Coal Gasification is performed by drilling a well into a seam of coal for reaching a subsurface. Miners use this well for pumping oxidants in to ignite and provide the fuel for transformation of coal into a gas. Separation wells are used to remove the obtained gas (syngas) and for bringing this gas to a plant for future production of energy. Syngas is widely used for development of various sources of energy, such as natural gas.
Underground Coal Gasification provides a lot of advantages. Mining companies use this method for removing emissions, thus eliminating damage for the surface. This method makes transportation and high cost equipment needless.
Underground Coal Gasification removes almost all sulfur dioxide and nitrogen dioxide and makes this removal safer for people and environment because it is performed underground. Maximization of hydrogen in the cavities and transformation of carbon oxide into carbon dioxide leads to a considerable decrease of carbon dioxide. It is removed by means of acid treatment.
Additionally, this method eliminates solid wastes, which are produced by coal factories.
Coil contains uranium and thorium. During the burning of coal, these components are released in the form of ash. Scientific researches show that radiation emanating around coal factories are higher by approximately 50-200% as compared to the surrounding environment (Hvistendahl n. p.).
Underground Coal Gasification reduces production of harmful ass and decreases negative impact on the environment. Moreover, the ash from coal burning is additionally recycled for producing energy.
Therefore, mining companies that implement this method of cleaning coal do not need to buy heavy mechanisms and various equipment used for coal transportation. Moreover, pollution of the environment from the process of transportation, for example, from trucks is also reduced.
The National Society of Professional Engineers (NSPE) outlined ethical requirements to the job description of an engineer. Underground Coal Gasification is regulated by Section II and Section III of the NSPE code of ethics.
Section II states requirements and rules of practice. According to the Section III of these rules, engineers have to issue statements to the public in truthful and objective way. Furthermore, Section V of these rules stipulated that engineers have to avoid deceptive and misleading acts. Thus, engineers have to provide truthful, accurate and correct information and description of a process. Information about coal cleaning and the process of Underground Coal Gasification is very complex and precise. Engineers describe all steps of the process in great detail.
Section III has the name Professional Obligations. In this section, it is noted that engineers have to think about other people and their health. They develop projects and perform actions for securing people’s health and clean environment. Engineers have to provide upright information about used technologies and any consequences. Therefore, all positive and negative sides of Underground Coal Gasification and implementation of clean coal technologies are described accurately.
Additionally, engineers have to improve life quality and create a safe environment. Underground Coal Gasification and other coal cleaning methods considerably decrease emission of carbon dioxide, sulfur dioxide and other harmful substances which leads to decreasing the negative impact on the environment and people’s lives.
Underground Coal Gasification and use of other methods of cleaning coal fully apply to code of ethics of the National Society of Professional Engineers.
Choi, C. “The Energy Debates: Clean Coal.” LiveScience, 5 Dec. 2008: n. pag. Web. 5 October 2013.
Dowdey, Sarah. “What is Clean Coal Technology?”
Fultz, K. “Perspectives on the Potential of Clean Coal Technologies to Reduce Emissions From Coal Fired Power Plant.” 1989. Web. United States General Account Office.
Hvistendahl, Mara. “Coal Ash is More Radioactive Then Nuclear Waste.” Scientific American, 13 Dec. 2007: n. pag. Web. 5 October 2013.
Siegel, R. P. “Clean Coal: Pros and Cons.” Triple Pundit: People, Planet, Profit, 19 April 2012: n. pag. Web. 5 October 2013.
World Nuclear Association. “Clean Coal” Technologies, Carbon Capture & Sequestration, April 2013: n. pag. Web. 5 October 2013.