A Visit to the Drax Power Station, Selby, North Yorkshire - Case Study Example

Report: A Visit to the Drax Power Station, Selby, North Yorkshire. Coal has been used most extensively as a fuel all throughout human history. A fossil fuel most made from vegetation from the carboniferous era; there are evidences that coal was used even in the second and third centuries by the Romans in England. The Industrial Revolution played a major role in expanding the use of coal. With the path-breaking improvisations that James Watt carried out on the steam engine, the use of coal reached a different level.1 Located near Selby, North Yorkshire in Northern England, Drax is a coal fired power station with a maximum production capacity of 4000 MW power. With this huge output, Drax, owned by the Drax Group Plc. caters to about 7 % of the total electrical power requirements in the United Kingdom.2 First year students of the School of Process, Environmental and Materials Engineering at the University of Leeds visited the Drax power station on the 20th of February. This study-tour provided students with an invaluable opportunity to understand at first hand the processes involved in the production and distribution of electricity. At the visitor centre, and then during the course of the tour at the power station, students were informed about the step-wise procedure that leads to the production of electricity in detail, i.e. from the initial steps that include unloading and transfer of coal from the trains to the bunkers by the use of conveyor belts to the final production and distribution of electricity from the power plant. The aim of this report is to provide a comprehensive account of the visit to the famous power plant which claims to be the largest, cleanest and most efficient coal-fired power station in the UK.3 These processes have been described in the report in detail along with photographs as and where necessary. Also discussed in this report are the environmental threats posed due to carbon emission from the combustion of coal. The measures taken by Drax Power Station to prevent and control pollution have also been mentioned in the report. In conclusion, a brief about the visitor centre facilities has been provided and the invaluable information provided by the officials has been gratefully acknowledged. Production of Electricity in Drax Coal is discharged from coal trains with the use of bottom hoppers that automatically open and drop the coal from the running train. Discharged coal is then transferred to coal bunkers. Automatic conveyors are used for this purpose. Conveyors ensure a quick and accurate transfer of coal to the designated bunkers. In the next important step, coal is fed to the pulverizing fuel mills and ground to a fine powder. Each of the six units of the Drax power plant has ten pulverizing fuel mills. Each such mill is capable of pulverizing 36 tones of coal per hour. Ten huge, hollow steel balls weighing approximately 1.4 tones and measuring 730 millimeters in diameter crush the coal into a fine powder. Coal is crushed into a fine powder thus because it makes it easier to burn it more completely. 4 The powdered coal now needs to be transferred to the boiler burner. This function is carried out by the Primary Air Fan that blows hot air at very high speed and pressure, thus transferring the coal to the burner. Boiler Burner In the boiler burner, oil and propane gas serve as the fuel, and the combustion is initiated by a spark plug. Once the coal and air mixture catches fire, the input of propane and oil is stopped. Boiler converts energy in the form of coal, into steam at a rate of 563 kilogrammes per second. Each boiler is of the height of a fifteen storey high building and weighs about four thousand tones. The steel tubing that lines the boiler is enough to stretch for three hundred miles, i.e. the distance from London to Newcastle. Inside the steel tubing, pure feed water is converted into steam by the heat generated due to the combustion of coal.5 The production of steam is one of the most crucial steps in production of energy. As pressure is constantly exerted by the steam (due to a number of intermediate technical steps aided by apparatus like forced draught fan, induced draught fan, air heater, super heater, etc) the turbine rotates at a very high speed. Rotor Stator A shaft of the turbine is connected to a large electromagnet part called rotor. The rotor lies in the centre of a cylinder of copper windings, called stator. The action of rotor and stator (together referred to as generator) produce alternating electric current (AC) at 23,500 volts, which is about hundred times the normal voltage power.6 Transformer The electricity from the generator is then sent to a transformer. The transformer increases the voltage to 400,000 volts before sending it to the National Grid sub-station for distribution around the country.7 Two pannier mounted condensers are used to condense the steam back to water. Condensation occurs when the steam passes across the cold surface of a condenser that is made up of numerous tubes filled with river water. The water formed as a result of the condensation is and pumped back to the boiler via a series of low pressure and high pressure feed heaters.8 Coal and Environmental Hazards: Even though production of electricity and industrial activities are inevitable in this age, that the combustion of fossil fuels like coal pose serious threats to environment is an accepted knowledge. We shall briefly study the harmful effects of coal combustion before we see what steps Drax takes to combat pollution in its power station. Coal is a non-renewable source of energy. Thus, with each use of coal not only does the total amount of the source of energy available on earth gets depleted in a manner that cannot be compensated for, but the combustion and industrial use of coal is also responsible for causing pollution. It is for these reasons that judicious use of coal is very important. Combustion of coal, improper disposal treatment of its end / waste products produces pollutants like carbon dioxide (CO2), sulphur dioxide (SO2), airborne particles, nitrogen oxide, carbon monoxide, lead, arsenic, etc. are said to be produced after burning coal. Burning coal is a leading cause of smog, acid rain, global warming, and air toxics. All these by-products formed due to combustion of coal are present in the atmosphere in the form of air-borne particles and have been proved to have been proved to be responsible for a number of respiratory diseases like chronic bronchitis, aggravated asthma, premature death, etc. 9 Carbon dioxide is a major greenhouse gas and in the view of global warming and climate change phenomena all over the world. Heat emitted during coal combustion depends largely on the amounts of carbon, hydrogen, and oxygen present in the coal and, to a lesser extent, on the sulfur content. Carbon, a major component of coal, is the main source of heat and generates about 14,500 British thermal units (Btu) per pound.10 Steps taken by Drax to tackle pollution: As green house effect, global warming and climate change has been largely attributed to pollution caused by the use of fossil fuels; it becomes all the more important that powerhouses exhibit a greater sense of responsibility towards the environment. Drax Power Station was the first UK power station to be retrofitted with flue gas desulphurization (FGD) plant. The construction of the FGD plant began in 1988 and was finished in 1996. At least 90% of the sulphur dioxide from the boiler flue gases is removed by the FGD plant. Temperature of the cleaned flue gas is raised and then it is discharged up the 259 meter high chimney lined with titanium plate. At full operation, about 280,000 tones of SO2 per year can be removed from the chimney gases.11 Sufficient height of a chimney of a power plant is very important to control environmental pollution. Not only the chimney of Drax Power station confirm to the requirements, standing at a height of 259 meters, it was recorded in the Guinness Book of Records at a time as the highest industrial chimney in the world. (Now it is only the tallest in the country).12 In 2003, all the original burners were replaced with low NOX burners, in an effort to reduce the amount of oxides of nitrogen produced.13 Each boiler has three precipitators which contain high voltage electrodes. These electrodes attract the dust or pulverised fuel ash (PFA) from the flue gases. The use of electrodes thus ensures that the flue gases that pass out of the chimney are free from harmful particles as far as possible. In a year Drax about 1.4 million tonnes of PFA is produced at Drax. Most of the PFA collected thus is sold to construction industries.14 In conclusion, it is essential that the Drax Visitor Centre is mentioned. It was the first stop during the visit. The visitor centre organizes tours on the power station with an aim to familiarize people with the humongous task that production of electricity is all about. Students get to see a typical day in the power station due to the well-organized tour conducted by the officials at the visitor centre and this practical experience is invaluable in getting a better understanding of the process. In the course of their discussions, they were also made aware of environmental concerns associated with the extensive use of fossil fuels and about the measures taken by Drax to prevent and control pollution as much as possible. The information provided at the centre is also related to the prescribed National curriculum. The information is relevant not only to school children, but to people from all walks of life. The officials at the centre provide a lucid, engaging manner. The interactive tours are led by an experienced guide who also answers any queries that the visitors may have. The guides use a simple, non-technical language to give an easy to understand account of the technical procedures and machinery in the power station, making it possible for people even from non-technical grounds to grasp the details. Useful information in the form of brochures, photographs and video can be availed by the visitors to familiarize themselves with the functioning of the power station. The visit brought the students face to face with the tedious process that energy production is all about. In view of the energy shortage predicted all over the world the visit to the power station reinforced the theoretical knowledge the students had prior to the visit that production of energy indeed requires a lot of effort and money. Given the realities of energy production that we witnessed at the power station, in conclusion it can be said that the visit definitely sensitized the students towards respecting the continuous energy supply that is made available to them, and to increase their efforts towards energy conservation by making a judicious use of energy. References: 1. ‘A Brief History of Coal Use’, U.S Department of Energy, viewed on April 17, 2008, URL: http://fossil.energy.gov/education/energylessons/coal/coal_history.html 2. ‘Drax Power Station, Selby, United Kingdom’, www.power-technology.com, viewed on April 17, 2008, URL: http://www.power-technology.com/projects/drax/ 3. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/aboutus/ 4. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1867 5. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1873 6. Drax (2008), the official website, viewed on April 17, 2008, URL http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1904 7. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1906 8. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1908 9. ‘Environmental impacts of coal power: air pollution’, Union of Concerned Scientists, viewed on April 17, 2008, URL: http://www.ucsusa.org/clean_energy/coalvswind/c02c.html 10. Hong, B.D and Slatick, E. R., ‘Carbon Dioxide Emission Factors for Coal’, Energy Information Administration, Quarterly Coal Report,1994, viewed on April 17, 2008, URL: http://www.eia.doe.gov/cneaf/coal/quarterly/co2_article/co2.html 11. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1946 12. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1887 13. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1871 14. Drax (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/explore_drax/power_station/?id=1882 15. All photographs courtesy Drax, (2008), the official website, viewed on April 17, 2008, URL: http://www.draxgroup.plc.uk/ Read More