Free Meta Tag Generator

PAKPAS GROUP OF COMPANIES Engineering Excellence  


Fossil fuel power stations,have rotating machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal combustion engine. All plants use the energy extracted from expanding gas - steam or combustion gases. Very few MHD generators have been built which directly convert the energy of moving hot gas into electricity.By products of thermal power plant operation must be considered in their design and operation. Waste heat energy, which remains due to the finite efficiency of the Carnot, Rankine, or Diesel power cycle, is released directly to the atmosphere, directly to river or lake water, or indirectly to the atmosphere using a cooling tower with river or lake water used as a cooling medium. The flue gas from combustion of the fossil fuels is discharged to the air. This gas contains carbon dioxide, water vapour, as well as substances such as nitrogen oxides (NOx), sulfur oxides (SOx), mercury, traces of other metals, and, for coal-fired plants, fly ash. Solid waste ash from coal-fired boilers must also be removed. Some coal ash can be recycled for building materials.Fossil fueled power stations are major emitters of CO2, a greenhouse gas (GHG) which according to a consensus opinion of scientific organisations is a contributor to global warming as it has been observed over the last 100 years. Brown coal emits about 3 times as much CO2 as natural gas, and black coal emits about twice as much CO2 per unit of electric energy. Carbon capture and storage of emissions is not expected to be available until governmental regulations force big polluters to reduce or eliminate their CO2 emissions. Typical emmissions are given below for different fuels. (for unit conversions go below link)




Environmental impacts The world's power demands are expected to rise 60% by 2030.[7] In 2007 there were over 50,000 active coal plants worldwide and this number is expected to grow.[8] In 2004, the International Energy Agency (IEA) estimated that fossil fuels will account for 85% of the energy market by 2030.[7]World organizations and international agencies, like the IEA, are concerned about the environmental impact of burning fossil fuels, and coal in particular. The combustion of coal contributes the most to acid rain and air pollution, and has been connected with global warming. Due to the chemical composition of coal there are difficulties in removing impurities from the solid fuel prior to its combustion. Modern day coal power plants pollute less than older designs due to new "scrubber" technologies that filter the exhaust air in smoke stacks; however emission levels of various pollutants are still on average several times greater than natural gas power plants. In these modern designs, pollution from coal-fired power plants comes from the emission of gases such as carbon dioxide, nitrogen oxides, and sulfur dioxide into the air.Acid rain is caused by the emission of nitrogen oxides and sulfur dioxide. These gases may be only mildly acidic themselves, yet when they react with the atmosphere, they create acidic compounds such as sulfurous acid, nitric acid and sulfuric acid which fall as rain, hence the term acid rain. In Europe and the U.S.A., stricter emission laws and decline in heavy industries have reduced the environmental hazards associated with this problem, leading to lower emissions after their peak in 1960s.

 Carbon dioxide, Electricity generation using carbon based fuels is responsible for a large fraction of carbon dioxide (CO2) emissions worldwide and for 34% of U.S. man-made carbon dioxide emissions in 2010. In the U.S., 70% of electricity generation is produced from combustion of fossil fuels, coal is much more carbon intensive than oil or natural gas, resulting in greater volumes of carbon dioxide emissions per unit of electricity generated. In 2010, coal contributed about 81% of CO2 emissions from generation and contributed about 45% of the electricity generated in the United States. In 2000, the carbon intensity of U.S. coal thermal combustion was 2249 lbs/MWh (1,029 kg/MWh). while the carbon intensity of U.S. oil thermal generation was 1672 lb/MWh (758 kg/MWh or 211 kg/GJ) and the carbon intensity of U.S. natural gas thermal production was 1135 lb/MWh (515 kg/MWh or 143 kg/GJ).







Carbon dioxide (CO ) is an essential element of photosynthesis required for growth and food production in plants. Photosynthesis is a process by which CO and water are absorbed by plants and then converted in the leavesinto sugars, cellulose and starch under the influence of light energy. More photosynthesis means more growth although there are optimal CO levels

There are a number of ways of increasing the levels of CO in a greenhouse. Lindesupply options for CO offer a purity above most onsite generation - meaning you are not introducing toxic flue gas - while our application systems ensure consistent application, optimising the addition of CO . In a closed environment like a greenhouse, this level could fall to about 120-180 ppm (due to the plants consuming CO ) with the result that photosynthesis would no longer take place and the plants would stop growing.

A Worked Example, Let us assume that the air in the greenhouse contains a CO level of 400 ppm; that equates to 0.72 g/m3. At an average greenhouse height of 6 m, that amounts to 4.32 g of CO per square metre. Now, to increase production, we want to increase the level of CO to 1000 ppm. This would equal 1.8 g/m3, or 10.8g/m2 with our average greenhouse height of 6 m. We therefore need to add around 6.5 g per square metre. CO also escapes from the greenhouse, e.g. through ventilation, leaks, and of course also through the plants and crops. This means that an additional 2.3 g of CO needs to be added per square metre per hour. In this example, the total CO to be added would amount to 88 kg per hour for an entire hectare.

Assuming, 595,000 ton/year/ha CO2 required for better and healthy growth of green house plants. and



Since 1974 "Pakpas©Group"  All rights reserved. Rev-14-3