The Reactor Design Project Engineering Essay

The Reactor Design Project Engineering Essay The project objective was to optimize three different adiabatic ammonia reactor configurations with respect to reactor performance in order to produce 800 tonnes of ammonia per day, or the molar equivalent of 0.5447 kmol s-1 of ammonia. The optimizations in reactor performance involved primarily, minimizing the catalyst volume and secondarily, maximizing the catalyst lifespan, as well as ensuring the final operating conditions were stable. Due to the absence of a cost function, the reactor could NOT be optimized with respect to cost minimization. Three different reactor types were considered, namely a single plug-flow reactor, a dual interstage cooling reactor and a dual cold-shot cooling reactor. Temperature, pressure and fraction of ammonia in the feed stream were found to have the greatest effect on the resultant catalyst volume. Using MATLAB, it was found that the minimum volumes were 9.61 m3, 3.94 m3 and 4.78 m3 for a single stage plug-flow, an interstage cooling configuration and a cold shot cooling reactor configuration respectively. The interstage cooling reactor allowed for a 59% decrease in total catalyst volume when modified from the single stage design, but required an increase in inlet feed temperature of 115K and 2 additional heat exchangers. The cold shot cooling method allowed for a 50.2% decrease in reactor volume from the single stage design, requiring a 75K increase in feed temperature. 1. Introduction 1.1. Background Ammonia synthesis (also known as the Haber process) is one of the most widely applied chemical processes in the world; in 2009, the total worldwide production of ammonia exceeded 133,000 metric tonnes 1, this is second only to the worldwide production of sulphuric acid. Most of the ammonia produced is used in the manufacture of fertilisers (such as ammonium nitrate), ammonia is also used in the manufacture of nitrogen-based polymers such as nylon. Another noteworthy use of ammonia is as the starting reagent for the manufacture of nitrogen-based explosives such as nitroglycerin. The reaction which generates ammonia is exothermic and equilibrium limited: N2 + H2 is in equilibrium with NH3 ΆHR (298K, 1atm) = -46.11 kJmol-1 [Eqn. 1] In the early 20th century, Fritz Haber discovered that in order to obtain a significant yield of ammonia, the reaction required both high pressures and low temperatures (in accordance with the van t Hoff-Le Chatelier principle). It was known that the rate at which N2 decomposed in the reaction was very slow (N2 is thermodynamically more stable than NH3); therefore a very efficient catalyst was required in order to facilitate ammonia formation. Nowadays, the catalyst used in most industrial ammonia reactors is usually a porous form of enriched iron. Catalysts are expensive, but they present a good trade off; reactors are able to produce sufficient amounts of product at lower, more manageable temperatures and pressures. 1.2. Design objective The overall objective was to design a continuous fixed bed plug-flow process to meet the companys daily ammonia production demand of 800 tonnes per day (exclusive of any ammonia in the feed). The primary design objective was to try to minimize the catalyst volume the process required in order to meet the production requirement. The design also had to be considered safe to operate and had to operate at conditions that were considered to maximize the lifespan of the catalyst; these two were considered as secondary objectives. The preliminary design of the reactor considered a single-stage adiabatic bed with a bed cross-sectional area of 2.0 m2. The final designs involved two different two-stage systems; one implementing interstage cooling and the other implementing cold-shot cooling. Reactor performance and sensitivity were analysed by observing the effects of altering specific operating and design variables. The cost function for the process was not known, therefore it is important to note that the reactor could not be optimized with respect to cost, however the design could be implemented such that the reactor performance was greatly improved. For example, minimizing the required catalyst volume (and hence minimizing the reactor volume) will reduce the construction cost of the reactor. However this may come at the expense of greater operating and maintenance costs and, in the case of two-stage systems, may result in additional construction costs (interstage cooling requires heat exchanger(s) to be built). The investigation will only allow qualitative suggestions to be made as to which specific design aspects contribute to the generation and/or reduction of costs. 1.3 Safety The reactor operating conditions should be stable; such that small disturbances will not lead to thermal runaway (which has important implications for safety). Other than that, there are no large risks involved with operating the ammonia reactor, provided that good process control is implemented by the operator. 2. Kinetic theory and types of reactor configurations 2.1. The kinetics of ammonia synthesis and its implications on reactor design Ammonia synthesis involves a single exothermic, reversible reaction between nitrogen and hydrogen. For reversible reactions, the conversion corresponding to thermodynamic equilibrium at the chosen operating conditions cannot be surpassed. Since the reaction is exothermic, the activation energy (which is only temperature dependent) of the backwards reaction is greater than that of the forward reaction. Therefore an increase in temperature causes a rise in the rate of the reverse reaction which is greater than the rise in the rate of the forward reaction thus decreasing the maximum attainable conversion but decreasing the required catalyst volume. On the other hand, operating at a lower temperature increases the maximum attainable conversion, whilst reducing the total reaction rate and increasing the required catalyst volume. With regard to pressure, the effect is the opposite; increasing the pressure causes a greater rise in the rate of the forward reaction compared the backward react ion and vice versa. Designing a reactor producing ammonia therefore requires a compromise between keeping temperatures sufficiently high such that reaction rate remains significant whilst obtaining a respectable conversion of ammonia. Similarly, the pressure should be great enough so as to maintain a significant reaction rate, but not so high as to cause the reactor to deviate from safe operation. In order to minimize catalyst volume (and meet the primary objective), it is desirable to operate at the maximum forward rate of reaction at each cross-section across the reactor; thus maximizing the average forward rate across the reactor, this allows the desired extent to be met with the minimum catalyst surface area and hence with the minimum catalyst volume. In order for this to occur, each cross-section in the reactor must be operated at the unique pressure and temperature required to achieve maximum rate for a particular extent, i.e. the reactor moves along the locus of maximum reaction rates. This is unfeasible in this investigation since there is no temperature or pressure control implemented across the reactor (the reactor is adiabatic and WSHAFT=0); and even so, maintaining specific pressures and temperatures at each point along the reactor is practically unfeasible in itself; as each point in the reactor would require its own heat exchanger and pressure control system. Therefore for exothermic reversible reactions (without heat removal), the temperature increases along the length of the reactor and the rate vs extent profile will always have a characteristic maximum because the temperature along the reactor increases due to the heat released by the reaction, causing the net production rate to increase up to a certain extent before the reverse reaction starts to become significant. As the rate of the backwards reaction tends to increase further and temperature rises, the overall reaction rate will eventually reach zero at equilibrium. 2.2. Brief description of the Plug-Flow Reactor (PFR) A plug-flow reactor is characterized by fluid flowing through one end of the reactor and out the other, whilst satisfying the assumptions of plug-flow. The assumptions state: Fluid properties and flow rate remain constant across any cross-section of the reactor. The flow is orderly, with no element overtaking or mixing with fluid ahead or behind, (i.e. the residence time is the same for all fluid elements). The above assumptions tend to hold true where there is turbulent flow (Re >105), ensuring good radial mixing, and if the ratio of reactor length to diameter of the reactor is large (ratio à ¢Ã¢â‚¬ °Ã‚ ¥ 50), where lateral mixing may be neglected 2. Figure 1: An illustration of a plug-flow reactor 3 2.3. Brief description of Interstage Cooling Interstage cooling, also known as intercooling, is a multiple reactor design suitable for exothermic reversible reactions. Heat exchangers are used to cool the output of each reactor before being passed on to the next reactor, allowing for a greater possible conversion to be achieved in each successive reactor. This process can be replicated for an indefinite number of reactors until the reactor temperature is too low for reactions to occur or until the decrease in catalyst volume is not worth the additional cost of construction and complexity of operation. This project considers only the case where two reactors are used. Figure 2: An illustration of a dual reactor interstage cooling system4 2.4. Brief description of Cold-shot Cooling Cold-shot cooling reactor designs are similar to that of interstage cooling, but allow for elimination of the intermediate heat exchangers by injecting cold feed directly into the outlets of each reactor. This addition cools down the outlet stream of the reactor and also has the effect of decreasing the composition and conversion of the flow into the subsequent reactor (corresponding to the path from point b to c in Figure 3 below). Figure 3: An illustration of a dual reactor cold-shot cooling system 5 The flow diagram of two cold-shot reactors illustrates the lack of heat exchangers as compared to interstage cooling, as well as the splitting of the initial feed stream by the splitting fraction alpha, ÃŽÂ ±, which is the fraction of the fresh feed used as the coolant. The extent of reaction remains constant after mixing (which can be proven by a mass balance). 3. Mathematical model Derivations of differential equations All the assumptions of plug-flow mentioned above were applied in the construction of the equations below; the reactor was also assumed to operate at steady state (there is no mass hold up due to the catalyst). All other assumptions are mentioned in the derivations. It should be noted that rNH3 is defined as (rNH3 generated rNH3 consumed) and is measured per unit of catalyst volume; hence the equations specify the volume of catalyst VC and not the reactor volume VR. 3.1. Change in catalyst volume with respect to the extent of reaction: Mass balance on ammonia: [Eqn. 2] The extent of reaction can be defined as: [Eqn. 3] Equations 2 and 3 were combined to obtain the following equation: Since , the equation above was rearranged to give the initial catalyst volume gradient: [Eqn. 4] 3.3. Change in temperature with respect to the extent of reaction: Figure 4: An illustration of the cross section of a plug-flow reactor An energy balance across an infinitesimally small cross section of the catalyst bed gave: Shaft work (W), changes in kinetic energy and changes in potential energy were neglected: The equation above was divided by the cross-sectional area of the tube, A: where Q denotes the heat transfer by conduction. In the equation below, the enthalpy change upon mixing was neglected (a perfect solution was assumed). It was also assumed that the gases in question were ideal and hence their enthalpy was independent of pressure, the energy balance then took the form: [Eqn. 5] is the standard heat of formation of compound. i denotes each species present. Recalling that for a tubular reactor, and : does not have a negative sign as rproduct is calculated as the main subject) [Eqn. 6] The heat of reaction was simplified as shown below: [Eqn. 7] Equation 7 was substituted into Equation 6 which was then substituted into Equation 5: [Eqn. 8] The chain rule was used to combine and : Since the reactor was assumed to be adiabatic, Q = 0: [Eqn. 9] 3.4. Change in pressure with respect to the extent of reaction: The chain rule was used to find using the formula for , bed cross-sectional area A and since A dl = dVC. Substituting the components of the three terms above, we get the initial pressure against extent gradient formula: [Eqn. 10] 4. Simulation theory and strategy 4.1. Main simulation objectives Regardless of the design used, these objectives are overarching and apply to all three reactor types: The first two bullet-points define what is meant by optimizing the reactor: Minimizing catalyst volume; Operating temperatures and pressures are limited by safety considerations (preventing thermal runaway), material construction and catalyst degradation conditions. These degradation conditions are specified by actual limits set by ammonia process operators in industry: these are above 823 K and above 300 bar 6; Interstage and cold-shot cooling designs are only dual reactor designs. The derivation of the required total extent for all simulations is as follows: The MATLAB coding incorporating the required data and was used to solve the differential equations described earlier in the mathematical model for the outlet temperature, pressure and catalyst volume; all the assumptions applied in the mathematical model were thus applied in the coding, unit consistency was also maintained in the programming. 4.2. Single stage simulation strategy It is clear that a plug-flow reactor can take advantage of concentration profiles present in the reactor in order to minimize the total catalyst volume. Near the desired extent, adiabatic plug-flow reactors (running exothermic reversible reactions) operate ideally somewhere between the equilibrium line, where the rate of the forward and backwards reaction are equal, and the optimum line, which is a curve connecting the maximas of all the different rate curves, also known as the locus of maximum rates. Figure 5: A graph displaying the variation of forward rate with extent It is opted to run the reactor under conditions such that the inlet rate is exactly equal to the outlet rate where the reactor exits at the desired extent of 0.5447. The rin = rout condition limits the maximum average rate by a small amount but provides a greater amount of kinetic stability in the event of a disturbance; a small increase in the inlet temperature may push the reaction closer to equilibrium whilst a small decrease in the inlet temperature will decrease the outlet rate slightly but still allow the reactor to operate in a region of higher rates. The locus of rin = rout is found between the optimum line and the equilibrium line. As shown in Figure 5, this condition also means that the region of maximum reaction rate is taken advantage of; i.e. the rate in the reactor is always greater than or equal to the inlet rate. Therefore, although the temperature increases along the reactor, the forward rate is kept as high as possible. As the extent of reaction increases across the reactor for a fixed set of inlet conditions, it is expected for the surface area of catalyst to increase; if more product is generated, more catalyst is required to facilitate this generation. There is a limit in the MATLAB coding such that the catalyst volume decreases whilst the reaction extent continues to increase; the code is such that results after this point are treated as erroneous and are not used, thus the code finds the inlet conditions needed to achieve the maximum possible extent for an adiabatic reactor. To apply the simulation strategy, a MATLAB program was created to find the inlet conditions which satisfy the rin = rout condition for a desired final extent (0.5447 in this case). A separate program was also created to vary operating and design conditions individually and examine their effect on the catalyst volume. Graphs of the locus of maximum reaction rate, locus of rin = rout rates and the equilibrium curve were constructed using the desired inlet conditions determined from the single stage simulation. 4.3. Interstage cooling simulation strategy The overall reaction follows the adiabatic operating curve (it may not necessarily be a straight line due to the pressure drop across the reactor). It was desirable for the reaction to end at the same point as in the single stage simulation (with the same final extent); where the rate at the outlet of the second reactor lies on the rin = rout line for the desired extent. It was also desirable for the rate at the exit of the first reactor to be equal to the rate at the entrance of the second reactor; so that the reactor can continue onwards from the same rate in the second reactor (and maintain the average forward reaction rate). For this code, there was no condition that the rate at the inlet of the first reactor must equal the rate at the outlet of the first reactor (and likewise for the second reactor); since it was unfeasible to make the rates equivalent at all the inlets and outlets. Instead it was specified that rate1 OUT= rate2 IN and that rate2 OUT = rate OPTIMIZED SINGLE STAGE OUT. The extent in the first reactor (and therefore in the second reactor) had to be specified for each set of results. If the extent was too high, the outlet of the first reactor would be very near equilibrium whilst if it was set too low the outlet of the first reactor would be reached before the maximum rate had been obtained; therefore a degree of overshoot past the maximum reaction rate was desirable; the program ensured that there was a degree of overshoot past the maximum reaction rate in both reactors before validating a result. The locus of maximum reaction rates (from the single stage optimization) was used to determine the feed temperature for which the rate is a maximum at the start; this temperature was roughly 790K (located graphically). Above this temperature, the region of maximum reaction rates was not utilised at all; and the maximum extent achievable (using the gradient of the operating line) at equilibrium was roughly 0.28. This specified the minimum extent of reaction in reactor 1. If the feed temperature were too low, the first reactor would perform similar to a single PFR, defeating the purpose of having two reactors. Thus a moderate extent range of 0.3 0.4 was chosen for the first reactor as it was unworkable to put an excessive production load on either reactor. In order to apply this strategy, a program was used to specify the inlet conditions to the second reactor; the program moved along the operating curve using the initial conditions obtained in the single stage reactor up to the desired extent in the first reactor. This gave the inlet rate to the second reactor as well as the flow rate, temperature and composition of this stream. Following this, the rate1 OUT = rate2 IN condition was used to acquire the inlet and outlet temperatures and pressures of the first reactor and its volume. Lastly, the inlet conditions to the second reactor and the remaining extent were used to calculate the volume of the second reactor. The combined volumes and degrees of cooling between the reactors were compared for the chosen range of extents. 4.4. Cold-shot cooling simulation strategy Figure 6: A graph displaying the variation of extent with temperature for a cold-shot system The rate identity rin=rout used to optimize the single PFR was used in the cold-shot cooling reactor design. With reference to Figure 6, optimization was achieved by ensuring that the reaction moved from points aÆ’Â  bÆ’Â  cÆ’Â  d , with the following rate identities; ra = rb and re = rd. The second reactor would operate along the path that the optimum single PFR would operate on (e Æ’Â   d). By adhering to the above conditions, there were three variables left to define, namely alpha (ÃŽÂ ±), initial feed temperature Tini and the interstage extent ÃŽÂ ¾1. Fixing alpha and Tini would automatically define ÃŽÂ ¾1 and outlet temperature of the first reactor as the rates at points a and b must be the same. This optimized the first reactor for the given inlet conditions. By constructing enthalpy and mass balances on the mixing point of the outlet from the first reactor with the cold stream, the inlet temperature into the second reactor was determined, thereby finding outlet conditions of the second reactor, should it achieve the required extent of 0.5447 kmol s-1. Finally, in order to ensure that total optimization had occurred for the specified alpha and temperature, the difference in rates at points e and d was confirmed to be as close to zero as possible. Several iterations would be required to home in on the best inlet temperature for a given extent. The temperature of the feed used for cooling, Tf, was 298K; significantly lower than the temperature of the fluid exiting the reactor. This imposed an upper limit on the split fraction ÃŽÂ ±, beyond which the feed temperature into the second reactor would be too low for reactions to operate at an acceptable rate; catalyst volume would need to be larger to counter this effect, meaning optimization would not achieved. Therefore, by varying ÃŽÂ ± for 50 equal intervals from 0.01 to 0.5, and finding the 50 corresponding Tini values that satisfied the above stated rate identities gave the optimum reactor for each value of ÃŽÂ ±. The best cold-shot reactor specification was easily deduced from the setup which had the smallest overall catalyst volume. Results and Discussion 5.1. Single Plug-flow Reactor 5.1.1. Varying the ammonia composition in the feed Figure 7: A graph displaying the effect of ammonia feed mol % change on catalyst volume The composition of ammonia in the feed was changed while keeping the molar feed rate constant. (Change ratio: 4% decrease in NH3 = 1% increase in N2 + 3% increase in H2, etc). Figure 7 shows that decreasing the ammonia fraction from the original 8 mol % (while increasing the reactant mol %) lead to a significant drop in catalyst volume required. The greater concentration of reactants favoured the forward reaction, increasing the rate of formation of ammonia, leading to a smaller catalyst volume. When the ammonia fraction was too high (à ¢Ã¢â‚¬ °Ã‚ ¥0.16), the initial concentration of reactants was insufficient to achieve the required extent. Also, as the partial pressure of ammonia increased in the reactor, a greater proportion of the catalysts active sites became blocked and the forward rate decreased, increasing the required catalyst volume 7. It was decided to keep the mol % of ammonia in the feed at 8% in subsequent simulations; although the lowest mol % of ammonia in the feed produces the minimum catalyst volume, it is impractical for this to occur since ammonia is normally recycled in industrial reactors 8. 5.1.2. Varying the reactor cross-sectional area Figure 8: A graph displaying the effect of cross-sectional area on catalyst volume Figure 8 shows that increasing the cross-sectional area reduced the catalyst volume, but this reduction was more significant only at the smaller area values. Increasing the area increased the number of catalyst pellets available at the reactor cross-section; therefore a greater reaction rate was initially facilitated as the volume increased. However, the inlet flow was fixed, and beyond a certain area, the flow into the reactor did not utilise the additional pellet area at the cross section; and thus the catalyst volume was less affected. The cross sectional area for the remainder of the investigation was kept at 2m2 because the increase in cross-sectional area above 2m2 does not justify the relatively minimal reduction in catalyst volume. 5.1.3. Variation of catalyst voidage Table 1: Displays catalyst volumes for different values of catalyst voidage Voidage 0.7 0.6 0.5 0.4 0.3 Vc at ÃŽÂ ¾ = 0.54466 (m3) 23.4642 23.4877 23.5399 23.6728 24.1043 Voidage is the ratio of the catalyst volume to the reactor volume. A larger voidage means a higher catalyst pellet density, thereby allowing a smaller catalyst volume. However, increases in voidage past 0.4 did not contribute to any further significant decrease in catalyst volume. For the purpose of subsequent simulations, the voidage was kept to the original 0.4. 5.1.4. Variation of catalyst diameter Table 2: Displays catalyst volumes for different values of catalyst diameter Catalyst Diameter 0.011 0.009 0.007 0.005 0.003 Vc at ÃŽÂ ¾ = 0.54466 (m3) 23.5881 23.6209 23.6728 23.7675 23.9954 It is seen from the data that varying catalyst diameter had a negligible effect on the catalyst volume, suggesting that although the surface area of each catalyst pellet increased, the number of catalyst pellets decreased, and thus the overall catalyst area did not change significantly. It was decided to stick to the original catalyst diameter provided. 5.1.5. Varying temperature and pressure Figure 8: A graph displaying the effect of inlet temperature on catalyst volume for different isobars As the temperature was increased, a decrease in the catalyst volume was observed. At lower pressures, the gradient of the graph (the change in VC with inlet T) was much higher and therefore inlet temperature was more effective at reducing the catalyst volume at lower pressures. This has some implications with respect to cost; if the inlet temperature is increased, there is an electricity cost associated with operating the reactor at this higher inlet temperature, but there is also a saving due to the reduction in catalyst volume. Figure 9: A graph displaying the effect of inlet pressure on catalyst volume for different isotherms As inlet pressure was increased, the catalyst volume decreased. As discussed in the theory, the increase in pressure favoured the forward reaction, thereby increasing the reaction rate per unit volume of catalyst. However, the capital costs spent on reactor materials able to withstand the high pressures have to be taken into consideration in addition to the greater maintenance cost of the catalyst bed (since a higher pressure reduces the longevity of a catalyst). 5.1.6. Results of single stage simulation Table 3: Displays the specifications and feed conditions the optimized single PFR Feed Composition Cross sectional area (m2) Catalyst Diameter (m) Voidage Extent Temperature (K) Pressure (Bar) N2 H2 NH3 In Out In Out 0.23 0.69 0.08 2 0.0007 0.4 0.5447 624.2 796.0 300 298.6 It can be observed that the pressure drop throughout the reaction was rather insignificant compared to the total pressure in the reactor. The optimization values from the single stage plug-flow reactor were essential for designing dual reactors that utilized interstage or cold-shot cooling as the second reactors were designed to follow the reaction path taken by the single stage PFR. The optimum single stage pressure of 300 bar was also the optimum pressure used for the subsequent simulations; the maximum operating pressure tolerable is 300 bar according to the catalyst degradation conditions specified in the simulation objectives. 5.2. Interstage Cooling Figure 10: A graph displaying the extents of reaction for different temperatures. The interstage path for ÃŽÂ ¾1 values of 0.3, 0.34 (optimum), and 0.4 are displayed along with the locus of maximum reaction rates, the equilibrium curve and the locus of rin = rout. Results were obtained for 10 extents between 0.3 and 0.4; these are displayed in the appendix. From the graph above, it can be seen that for all three extents; 0.3, 0.34, 0.4, the reaction in the first reactor moved past the locus of maximum rates and the locus of rIN = rOUT and then approached the equilibrium curve, thereby maximizing conversion. The outlet stream was then cooled to a point along the path taken by the volume minimizing single PFR. The graph thus shows that performance optimization occurred in the interstage cooling design as catalyst volumes in both reactors were minimized. The range of chosen extents for the first reactor, 0.3 0.4 kmol s-1, also proved to be robust, providing well performing reactors with small catalyst volumes (where all reactors had a combined catalyst volume less than half of that of the single stage reactor). Volume reached a minimum of 3.94 m3 when the extent was fixed at 0.34 kmol s-1 with an inlet feed temperature of 737.1K. 5.3. Cold-shot Cooling Table 4 Conditions and results for the optimum cold-shot system Extent Achieved Temperature (K) Catalyst volume (m3) 1st 2nd 1st 2nd In Out In Out Vr1 Vr2 0.2958 0.2489 699 795.769 717.172 796.407 1.523 3.254 (Vc 1 Vc 2 = 1st 2nd Catalyst volume respectively) Figure 11: Catalyst volume minimizing temperatures at specific alpha values During simulation of the cold-shot cooling reactor design, it was deduced that the range of ÃŽÂ ± was restricted from 0.01 to 0.38, beyond which the bulk of the reaction would occur in one of the two reactors, making the other redundant. Optimally, ÃŽÂ ± should be somewhere between the limits of the range; for ÃŽÂ ± = 0.19 and feed temperature at 699K, a minimum overall volume of 4.78 m3 was achieved. It is seen from the graph above that as ÃŽÂ ± deviates from 0.19 and tends towards 0, the first reactor behaves more like a single PFR. The same happens to the second reactor as ÃŽÂ ± tends towards the ÃŽÂ ± upper limit. Increasing the initial feed temperature causes ÃŽÂ ± to increase in order for optimization to occur, while a decrease would bring about the opposite effect. This is because a larger fraction would be required to cool the output from the first reactor to achieve optimization should the reactor operate at a higher temperature. The contrary is true; with a larger ÃŽÂ ±, the initial feed temperature cannot be too low as excessive cooling of the second fraction would occur. 6. Conclusion It can be concluded that the investigation w

The Bluest Eye Essay -- essays research papers

Beauty is something that a lot of people in life strive for , because everyone has fitted in their mind what exactly beauty is. People know that it can help you out in life. But what most people don’t know is that, beauty is in the eye of the beholder. Meaning that beauty should not be characterized by what people are told it is, beauty is different for everyone, what is beautiful for you may be ugly to someone else. The characters in Toni Morrison’s The Bluest Eye are confronted with the ideal of beauty and strive for it whether they know it or not. The two characters that I think were followed the ideal of beauty in Toni Morrison’s story are Pauline and Pecola. In Toni Morrison’s story and in real life, beauty is described by people as having blond hair, blue eyes , perfect figure, etc. It’s been said that if you have good looks, you can make it in life with just looks alone. People only strive for becoming beautiful because they want attention. As is the case in Toni Morrison’s story. The characters in her story think that they are ugly , by others opinions of them , and want to become beautiful so they will be recognized and be the center of attention. But the harder both characters try, the worse things get. Pauline strived for beauty because she wanted to attention and wanted to be beautiful. Pauline seemed to have just worse case of bad luck, when she was a child she stepped on a nail and she was left with a limp forever. "The wound lef...

P1 the Functions of the Main Cell Components of the Body Cell

In this report i will be writing brief description on the functions of the main cell components of the body cell. The cell membrane : is something that lets some things in and some things out of the cell. It is an outer cover for the cell. If the cell membrane was non existences the cell would spill all over the place. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. It is composed of a thin, double-layered sheet of lipids, around the Cell and is a protective membrane layer around every Cell.Nucleus [pic] The nucleus is the control centre of a cell. It contains genetic material such as DNA and controls the cell's growth and reproduction. The nucleus also controls the synthesis of ribosomes and proteins in the cytoplasm. it also involved in cell division and stores all the information that is to be transferred to the next generation Cytoplasm cytoplasm is a homogeneous, which generall y clear jelly-like material that fills cells . The cytoplasm consists of cytosol and the cellular organelles , except the nucleus. The cytoplasm offers support for the cell.It allows the cells organelles to freely move throughout the cell. Movement is sped up in the fluid of the cytoplasm. The cytoplasm can also act as a medium for transport within the cell. Mitochondria: [pic] The mitochondria is the powerhouse of the cell it provides energy to the cell through respiration. The food that we eat is broken into simpler molecules like carbohydrates, fats and etc in our bodies. These are sent to the mitochondrion where they are further precessed to produce charged molecules that combine with oxygen and produce Adenosine TriPhosphate (ATP) molecules.This entire process is known as oxidative phosphorylation. Mitochondria also helps in the building of certain parts of the blood, and hormones like testosterone and estrogen. Smooth and rough endoplasmic reticulum :[pic] The smooth ER is a s ystem of internal membrane inside the cell which move proteins and other substance through the cell. Smooth ER has its purpose in the cell. It acts as a storage organelle. It is important in the creation and storage of steroids. It also stores ions in solution that the cell may need at a later time.Steroids are a type of ringed organic molecule used for many purposes in an organism. They are not always about building muscle mass like a weight lifter. The ion storage is important because sometimes a cell needs ions fast. It might not want to search the environment for ions, so it is easier to have them stored in a pack for easy use. Rough ER – looks rough on the surface because it is stubbed with very small organelles called ribosomes. Ribosomes are made of RNA and protein and are the site of protein synthesis. They are very important in the synthesis and packaging of proteins.Some of those proteins might be used in the cell and some are sent out. The ribosomes are attached to the membrane of the ER. As the ribosomes builds the amino acid chain, the chain is pushed into the ER. When the protein is complete, the rough ER pinches off a vesicle. That vesicle, a small membrane bubble, can move to the cell membrane or the Golgi apparatus Golgi apparatus[pic] The function of the Golgi apparatus is to modify, sort, and package proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell.Lysosome [pic] Lysosomes are single, membrane-bound sacs that contain digestive enzymes. The digestive enzymes break down all the major classes of macromolecules including proteins, carbohydrates, fats, and nucleic acids. Throughout a cell's lifetime, the lysosomal enzymes digest old organelles to make room for newly formed organelles. The lysosomes allow cells to continually renew themselves and prevent the accumulation of cellular toxins.

Healthcare Medicine and Health Systems Essay

Healthcare Medicine and Health Systems Essay Healthcare: Medicine and Health Systems Essay Topic Explanation of the Topic Example One Example Two Horizontal Equity Horizontal equity refers to an economic theory according to which individuals with similar income should pay similar taxes irrespective of the tax system thus helping create a neutral tax system. Physicians and all other medical professionals are liable to pay taxes, based on the amount that they earn, not based on profession, and this tax is equal to any other businessman or professional. Physicians and medical practitioners are required to pay professional tax, education taxes, development tax and all other taxes that any other professional pays. Vertical Equity Vertical Equity is the concept or idea of fairness in economics, refers to equal life chances regardless of identity, to provide citizens with a basic equal minimum income, goods and services or to increase funds (Bird, 2009) As the income of a physician increases he is liable to pay higher tax in proportion to his income based on progressive taxation theory. In case of medical insurance based tax benefits all of the professionals are given the same maximum amount benefit limit, thus leading to medical professionals with higher income to get only a limited tax benefit and pay more tax. Economic Efficiency Economic efficiency refers to the use of resources including capital, labor and even technology and assets in order to maximize the production of goods and services as well as its quality (Sullivan & Sheffrin, 2003). Computer Technology like telemedicine and electronic health records being used in the healthcare to improve efficiency, continuity of care, and better outcomes of health. Quality control and Total quality management are being used in the healthcare arena. Managed Care Managed care refers to variety of techniques used in order to reduce the costs of health care and improve the quality of care for organizations that use those techniques or provide them as services to other organizations. Usage of techniques like Medicare that can help in strategic reduction in costs along with other forms of medical insurance (Lynch, 1992). Utilization of methods like cost reduction and economic optimization in medical industry leads to managed care. Formal utilization review and quality improvement programs and an emphasis on preventive care (Kongstvedt, 2001). Topic of your choice Capitation refers to the payment arrangement in a health care top pay nurses and physicians based on per person allotted to them, per hour. Nurses and doctors are paid by salary, hourly and if in private practice are paid by the amount of patients they see after they pay their expenses. Professionals like psychiatrists and psychologist charge their professionals fees on per hour basis. Topic Explanation of the Topic Example One Example Two Horizontal Equity Horizontal equity refers to an economic theory according to which individuals with similar income should pay similar taxes irrespective of the tax system thus helping create a neutral tax system. Physicians and all other medical professionals are liable to pay taxes, based on the amount that they earn, not based on profession, and this tax is equal to any other businessman or professional. Physicians and medical practitioners are required to pay professional tax, education taxes, development tax and all other taxes that any other professional pays. Vertical Equity Vertical Equity is the concept or idea of fairness in economics, refers to equal life chances regardless of identity, to provide citizens with a basic equal minimum income, goods and services or to increase funds (Bird, 2009) As the income of a physician increases he is liable to pay higher tax in proportion to his income based on progressive taxation theory. In case of medical insurance based tax benefits all of the professionals are given the same maximum amount benefit limit, thus leading to medical professionals with higher income to get only a limited tax benefit and pay more tax. Economic

The eNotes Blog Do You Live in Americas Least, or Most, LiterateCities

Do You Live in Americas Least, or Most, LiterateCities The late, great comedian Bill Hicks tells one of my favorite stories about reading.   Following one of his late night gigs, he stops at a Waffle House to eat.   Alone, he pulls out a book. A waitress comes up to him,   tray balanced expertly on her fingertips, peers over his shoulder and asks, What are you reading for? Not What are you reading? What are you readingfor.   Chances are, Hicks was in one of the towns listed below as the least literate in America. Recently, the  Wall Street Journal  crunched the numbers to make determinations about cities with the worst, and best, reading habits. The criteria for these determinations included weekly newspaper circulation rates, the percentage of adults with college degrees, the number of retail bookstores per 10,000 people, and the median income. Least Literate: 1o.   Long Beach, California 9.   Mesa, Arizona 8.   Aurora, Colorado 7.   Fresno, California 6.   San Antonio, Texas 5.   Anaheim, California 4.   El Paso, Texas 3.   Stockton, California 2.   Corpus Christi, Texas 1.   Bakersfield, California Most Literate: 10.   Portland, Oregon 9.   St. Louis, Missouri 8.   Atlanta, Georgia 7.   Boston, Massachusetts 6.   St. Paul, Minnesota 5.   Denver, Colorado 4.   Pittsburgh, Pennsylvania 3.   Minneapolis, Minnesota 2.   Seattle, Washington 1.   Washington, D.C.

Why Queen Should Be Musical Canon Essay Example | Topics and Well Written Essays - 1000 words

Why Queen Should Be Musical Canon - Essay Example Their music has appeared in many movies, television shows and commercials, and many of their songs have become part of American culture in other important ways. They changed the way that people thought about music, the way music was presented to the public, and the way that music is made. By exploring these uses of Queen's music in film and television and establishing their important role in modern social history I hope to explain why their music should be considered part of musical canon. Everyone who has attended a sporting event in the US in the past 30 years is familiar with the songs We Will Rock You and We Are the Champions by Queen. We Will Rock You, in particular, is so well known that if you play it for any crowd in America they will immediately begin singing and clapping along, for every group from elementary school assemblies to professional sporting events. It is hard to find anyone unfamiliar with the drums and clapping which open the song. The sound of We Are the Champions inspires cheers and shouts of victory all over the country. Everyone in the country knows the refrain by heart, and associates it with winning, particularly in sporting events: We are the champions, We are the champions! No time for losers 'Cause we are the champions of the world! (Queen, 1977) The movie Wayne's World, released in 1992, helped to make Queen's epic anthem of operatic rock Bohemian Rhapsody even more popular than it already had been and introduced the band to a whole new generation of fans. Originally released in 1975, Bohemian Rhapsody was Queen's first top-ten hit in the United States. In the United Kingdom, where the band was already well established, it stayed at #1 on the pop charts for nine weeks-- a record at the time. Though the song only reached #9 on US charts when it was originally released, the re-release after Wayne's World peaked at #2. (Songfacts) The popularity of this re-release led to greater demand for the rest of the band's work, and the release of several greatest hits albums in the late 90s. Bohemian Rhapsody is still one of the most complex and elegant musical pieces to achieve broad popular appeal in modern times. The background track alone, with piano, bass and drums took two days of recording to complete. Sessions for the song lasted nearly three weeks, with the opera section alone taking seven days to complete. Queen sang their "Galileos" continually for ten to twelve hours each day, producing a staggering 180 vocal overd ubs. The tapes required another two days of mixing before the band agreed that the song was complete. (Davis) The message behind the lyrics of Bohemian Rhapsody are very elegantly stated, if somewhat controversial. Most fans agree that the song is about a murderer who confesses his crime to his mother and is eventually caught and sentenced to death. Still there is some speculation as to the true meaning of Bohemian Rhapsody, the lyrics of which can be interpreted in several different ways. In interviews, Freddie Mercury, lead singer of Queen and the writer of Bohemian Rhapsody, is quoted as having said that much of the song is â€Å"random rhyming nonsense.† (Songfacts) The extremely complex vocal harmonies and guitar riffs made Bohemian Rhapsody especially difficult to perform live, so the band created a music video-- one of the earliest music videos ever created-- in order to popularize the song while avoiding playing it live for a UK television audience. In doing so they c hanged the way that music is consumed. Today music videos are considered necessary for commercial musical success, but in 1975 they were almost unheard of. The video used camera effects which were

Food truck- Entrepreneur Interview and Reflection report Essay

Food truck- Entrepreneur Interview and Reflection report - Essay Example The entire process of learning involved with this module has made me to discover the possibility of effectuation as a suitable tool for advancing on entrepreneurial career, as well as providing important suggestions on how to come up with entrepreneurial skills (Price Institute for Entrepreneurial Studies, 2000). To start with, we are going to have an over view of Tullee’s restaurant which is a Caribbean restaurant located in the northern side of London. It was started in 2008 by Glen Watson who would like to expand the business so as to earn more income. Some of the segmented customers who buy from the restaurant include the local people most of them being working class. Other customers included those who came regularly came for lunch. After careful analysis we realized that most of the restaurant restaurants do not sell Caribbean food and this made us to start serving this food. In order to be competitive, our main focus was on the quality and the prices of food. The business intends to use social media as a way of connecting with the customers. Online orders will also be used where customers can make online orders through their mobile phones. Since the original owner of the restaurant used to have only one supplier, we intend to have several of them so has to increase the supplies. In order to attract new customers, we will provide best offers like price reduction and after sales service to win customer loyalty. For the case of customers who have been loyal, we will use them as referrals who will recommend us to other customers. We will also profile our cost structure appropriately so as to reduce costs as much as possible so as to maximize profits. Most of our valued resources will include: suppliers, employees and customers. According to Baron (2012), learning and reflection is a very important process in life. It