Flue Gas Desulfurization - Essay Example

The Running Head: Gas Treatment     Your name:   Course name:             Professors’ name: Date: Flue gas treatment technology (FGD) (Q1) Flue gas desulfurization (FGD) is a technology which is employed to remove sulfur dioxide (SO2) from industrial flue gases of power plants (Soud, 2000). In fuel power plants, they usually burn coal or crude oil to produce steam that will then drive electricity generators to produce electricity. In Flue gas desulfurization, SO2 is one of elements which is produced and forming acid rain when it mixes with water from the rain (Soud, 2000). (Q2) Most Flue gas desulfurization (FGD) technology will employ two stages, the first stage will involve fly ash removal and the second stage will be for SO2 removal. In wet scrubbing systems, flue gas that is found in power plants will first pass through a fly ash removal system and that will be either an electrostatic precipitator or a wet scrubber, thereafter it will pass through the SO2 absorber. However, when the gas has passed through a spray dry operations-dry injection, SO2 will then be reacted with the sorbent and then flue gas will be passed through a controlled device. The flue gas that is coming out of the absorber is mixed with water, but it will still contain some traces of SO2, this mixture is known to be highly corrosive (Soud, 2000). (1) SO2 + Ca(OH)2 ® CaSO3 · ½ H2O + ½ H2O (2) 4SO2 + 3Mg(OH)2 ® 2MgSO3 + Mg(HSO3)2 +2H2O There are two methods which are being employed to minimize the corrosiveness of SO2: the first method is that the gas is reheated to above dew point, or the second method is that materials which are being used in constructions should be designed in such a way they will allow the equipment to allow the corrosiveness of SO2 (3)CaSO3 · ½H2O + ½O2 + 3/2 H2O ® CaSO4 · 2H2O (4) MgSO3 + ½O2 ® MgSO4 (5) Mg(HSO3)2 + O2 ® MgSO4 + H2SO4 (Q3) (Q4) The following are advantages of this technology: SO2 is 95 per cent are common removed but the system can attain as high as 98 per cent SO2 removal, this technology is adequately and commercially viable, the reagents that are used in the process of SO2 are readily available, the waste gypsum which is produced is stable for landfills and cannot be blend with fly ash and lime (Soud, 2000). The following are the disadvantage of Flue gas desulfurization: the system will circulate large quantities of slurry which will make pumping to be high, therefore high power consumption, the pressure drop which is found across the absorber will increase the induced draft (ID) fan power consumption, high potential for corrosion will require engineers to use costly corrosion resistant materials during construction, and lastly, large volume of gypsum will depend on the market that is available near the plant (Soud, 2000). Fractional distillation Technology (Q1) This technology involves separation of a mixture into it’s constitute component parts or fractions, such as separation gases by their boiling point and this is achieved when these gases have been heat to a temperature at which several constitute gases compound will evaporate (Gulf Research & Development Co, 2006), actually fractional distillation is a special type of distillation. The component part of gases will boil at less than 25 °C from each other and this is under a pressure of 1 atm, but if the different in boiling points of respective gases is greater than 25 °C, then a simple distillation process will be used. Consider two gases, one of the gases evaporates at 78.5 °C and the other gas evaporates at 100 °C, a person should be able to separate the two individual components of gases by fractional distillation. (Q3)  (Q2) However, a mixture of two gases will be volatile than the individual gases but when the gases mixture is gentle heated, that gas which is more volatile will separate from the rest of the other gases first. Fractional distillation technology is widely used in refineries to separate crude oil and natural gases into useful fractions. The fractions consists of different boiling points, those gases with higher boiling points will consist of larger molecules and are more difficult to ignite and to burn. At all the time the new feeds in the fractional distillation is continuously added to the distillation column, and the constitute gases are continuously removed (Gulf Research & Development Co, 2006) (Q4). The following are advantages of fractional distillation: it is a cheap way of separating gases into its constituent components when you compare it with other technology, it is the fastest way of gas purifications, and lastly it is easy to construct (Gulf Research & Development Co, 2006). The following are its disadvantages: the setup process of fractional distillation is more complicated than a simple distillation, it will take longer for gases to be distilled, fractional distillation process will consume a lot of energy than a simple distillation, and lastly the constitute gases are sometime lost during fractional distillation and therefore the recovery of purified gases will be less than it was expected from the crude gases (Gulf Research & Development Co, 2006). Membrane Technology (Q1) This technology is widely used in industrial applications; the importance of membrane technology is its responsibility for the gas separation process. Nowadays, membrane separation does no longer represent a flat plate or film (Muralidhara, & Cui, 2010), but it’s usually shaped in a hollow fibers. (Q2) The working of a membrane technology is used to selectively transfer certain chemical species- protons, ions, molecules, compounds or a combined transport of electrons and ions- through a membrane or a wall, this term of membrane is often used for kind of transport which is permeation (Muralidhara, & Cui, 2010). The chemical species will often transferred from a feed gas to another side of the membrane, typically gases from the other side of the membrane will be transported away from the membrane; feed gas side is referred to as the retentate side and the other side (sweep gas side) can be referred to as the permeate side (Muralidhara, & Cui, 2010). (Q3)  The characteristic of this technology is its permeability and selectivity, in permeability is the measure of how fast, protons, ions, molecules (Muralidhara, & Cui, 2010), compounds or a combined transport of electrons and ions are transferred through the other side of the membrane, while in selectivity will tell us how selective the membrane will have for different gas types in the technology. The flux of the membrane will depend on two things: membrane thickness and its driving forces that are present in the system, but the mass transfer resistance will increase with the thickness of the membrane. Therefore, a thin membrane will have a higher flux and this is usually preferred, while a thin membrane will have a lower flux, but if the membrane is very thin it is importance to have a support layer that will ensure mechanical strength for the membrane wall. The driving force that is available at the membrane is usually given by it concentration of gases, its partial pressure or the chemical potential that is available across the membrane (Muralidhara, & Cui, 2010). (Q4). The following is its advantages of membrane system: the system itself is cost-effective and is characterized by energy-efficient, and it is also environmentally friendly operation when you compare it to other technology. The following are its disadvantages: when the membrane has a default the system will fail, also the membrane need replacement to make it effective in gases separations (Muralidhara, & Cui, 2010). Benfield Technology (Q1). This process is widely used to remove H2S and CO2 from a mixture of gases, such as in natural gas crude gas and reformed gas…etc. Benfield process can be more efficiently adapted to the requirements that are needed in treating gases by combining flow types that is provided in removal of CO2 only, or CO2 and H2S, and this will reduce the heat consumption that is involved in this processes (Warburton, 2009). (Q2). In the system an activator is used to lower the pressure of acid gases, thus absorption rate will be accelerated. The heat consumption that is used for regeneration of the absorbing liquid will be reduced with the use of steam ejector in the system. The process that is involved in the system is based on the following reactions (Warburton, 2009): (Q3)  (1)K2CO3 + CO2 + H2O = 2KHCO3 (2)K2CO3 + H2S = KHS + KHCO3 In the HiPure Process, the reactions described below are added. (3)2R2NH + CO2 + H2O = (R2NH2)2CO3 (4) (R2NH2)2CO3 + CO2 + H2O = 2R2NH2HCO3 (5)2R2NH + H2S = (R2NH2)2S (6) (R2NH2)2S + H2S = 2R2NH2HS The regeneration of acid gases is the same as that of the conventional amine or carbonate processes. The gas that is to be purified will be fed to the bottom of the absorber and flows in the opposite direction to the absorbing liquid that is being supplied at the top of the absorber in the system, the acid gases is then absorbed by the absorbing liquid (Warburton, 2009). (Q4). Benfield Technology has the following advantages: no anti corrosive materials are needed in the construction of this system, the liquid that is used to absorb the gases is nontoxic and no proprietary chemicals will be used, and lastly, the liquid that absorbs the gases will not suffer degradation. The disadvantages of this equipment are that it’s not widely used; it has limitation on the amount of gases which can be produced at a go, and lastly it expensive in term of implementation costs (Warburton, 2009). Reference List Gulf Research & Development Co. (2006). A source book of technical literature on fractional distillation: published as a service to the chemical engineering profession. Dubai: Gulf Research & Development Co Moore, H. (1995). The scientific principles of petroleum technology. London: Van Nostrand Publisher Muralidhara, H.S & Cui,Z. F. (2010). Membrane Technology: A Practical Guide to Membrane Technology and Applications in Food and Bioprocessing. London: Elsevier Science Publisher. Soud, H.N. (2000). Developments in FGD. New York: IEA Coal Research Publisher Warburton, G.H. (2009). Chemical technology and analysis of oils, fats and waxes, Volume 1. London: Macmillan and co. Publisher Read More