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Control Of Sulphur Dioxide Environmental Sciences Essay

SO2 can be an kind of industry polluting of the environment mostly from oil and coal consumption, industry activities and traffics. According to analyze of EAP(U. S. Environmental Protection Agency) more than 100 million tons sulphur dioxide is discharged into the atmosphere each year all over the world. In the type, most of the sulphur emissions are in the H2S(hydrogen sulphide), CS2(carbon disulphide), COS(carbonyl sulphide) and some organic compouds. Through burning, these organics that have sulphur aspect discharge the sulphur dioxide to the atmosphere, which can lead serious environmental problem and harm human's health. SO2 pollution could cause plants dead in a extremely high speed, and it is dissolved easily in to the wind, which may cause the acid rain which may distroy the outdoor buildings. The most of all, high concentrated SO2 in the atmosphere can kill people or cause serious ills including bronchitis, emphysema and oculoglandular conjunctivitis. Moreover, the sulfuric acid, is a second pollutant. When sulphur dioxide is involved in additional chemical reactions, it can react with oxygen and water to sulfuric acid which is the constituent of 'acid rain'. (NATHANSON, J. (1986))

Generally, to solve the serious environmental problem, there are two research torwards in removing sulphur dioxide:pretreatment and afterwards absorbing. No real matter what methods people use were all included in such two research directions.

Pretreatment means separate the sulfur component from the coal mineral before it was burned. Because the key organises of sulfur factor in coal are FeS2 and organic and natural sulfur, generally, in industry people often use independent ways to do separation. For the inorganic sulfur including FeS2, the most traditional way is gravitational segregation this means separate the ore containing sulfur element from the coal with the distinctions in density. Such method is incredibly financial and technical simple, however its effects sometimes are limited. Due to the differentia of the coal ore all over the world, the strainaway rate of the sulfur component is highly different. In some area the gravitational segregation can remove approximately 90% of the sulfur factor in coal ore, while in a few certain coal mines of 40% of the full total sulfur content can be wiped off.

For the organic and natural sulfur element, it seems that there isn't a efffective pretreatment approach to solve it. What people can do is merely absorb the SO2 from burning organic sulfocompound. Unfortunately, as a result of complicated organization of organic matter, generally, the sulfur contained in the coal ore would be burned directly into a series of sulfocompounds including H2S, CS2, SO, SO2 rather than only SO2. So before people assimilate the SO2, people have to transform these compounds into SO2 first. Nowdays the most frequent way is fluidized bed.

Fludized bed is some sort of organization for gasification of coal which is created by Fritz Winkler of Germany on December 16, 1921. Since the early 1960s, Douglas Elliott put forward that the coal should be burned instead of gasifying coal in a bubbling fluidized bed, because the it can generate steam by immersing boiler tubes. In 1982, the first CFB boiler which can burn low-grade coal was built in the Vereingte Aluminum Werke at Luenen, Germany in 1982 which was created exclusively for the way to obtain steam and heat.

The general gas-solid fluidizetion has 5 major application: Energy conversion, Petro-chemical processing, Mineral processing, Chemical and pharmaceutical and Physical processing, and the basic you are energy conversion.

FIGURE 1. 2 Schematic of a higher temperature fluidized bed gasifier

In general coal would be fed into bubbling fludized bed at 950 degree. Steam would be fed into the base of the fluidized bed by having a sparge pipe-type of distributor. Then the coal would leave the hot solids in the bed and the cleaned and used gasification products leave the bed from the top. In this process limestone (CaCO3) and dolomite (CaCO3MgCO3) would be mixed with the coal ores to abstract the SO2 from the burning. The chemical equation is as follow:

(1. 1)

After the fluidized bed step, there is still approximately 20% SO2 left in the offgas. To resolve this SO2, people need some technologies including Calcium-Based Reactions and Sodium-Based Reactions, that have been called afterburning absorbing.

Until now, there is not a cheap and effective approach. The effective methods usually are expensive and lay a heavy burdon on finance, at the same time, the cheap ones disable to eliminate the sulphur dioxide satisfactorily.

The major information of the paper includes the benefits and defects of the traditional ways controlling the SO2, the rational of the new aspect: magnetic method, the problems may meet and the solutions of this approach. . The best reason for the assignment is to indicate a remedy both financial and efficient. All the experiments and theories mentioned in this essay are based on theories and logical deductions.

Analysis

Advantages

Nowdays in technology aspect people have the ability to control the SO2 letting effectively, after all the steps the SO2 discharged in to the atmosphere is less then 1%. Materials of these technologies are all hackneved, . Moreover, some certain technologies can create a series of cost efficient second products such as vitrol and compound fertilizers.

Pretreatment is most beneficial method to control the sulfur dioxide, personally. Not only because the FeS2 can be separated from the coal ore easily, but also FeS2 can be another useful materials in industry. Due to the characters of coal mines, the associate ore of coal is FeS2 generally. As a result the FeS2 ore occupies a large part of coal mines in anywhere of the world, and the FeS2 ore is the most typical material of puddling. So the pretreatment is a both efficient and financial approach.

Fluidized bed is the next steps of the whole sulfur dioxide, the absobents of fluidized bed are extremely cheap and common. So this technology resently is employed widly in the countries that are occupying a roomy area such as China and American as a normal skill. And such technology is extraordinary suit for the large-scale factories.

Afterburning absorbing is the most efficient way to regulate the sulfur dioxide discharging regardless of the concentration. The best consistence of SO2 in off gas which is disposed by the afterburning absorbing usually is significantly less than 5%.

In summary, the technologys resent used in the SO2 control are highly mature, however you may still find some disadvantages can not be ignored.

Disadvantages

Although pretreatment is the most efficient and financial solution to control the sulfur dioxide, it has the deadliest defect: the restriction of area. Due to the difference of the organization of coal ore in different area, such technology disables to be spreaded.

For the fluidized bed the problems are secondary products and the processing ratio. When the chalks go into the boiler the active principle, CaCO3 would be resolve into CaO and CO2. The burned CO2 would sepatate out and enlarge the interspace on the CaO to form the lacunose CaO which can response with the SO2 easily. Nonetheless it is impossible to make all of the CaO be the CaSO4, because the sulphating would make the interspace fullfilled by CaSO4. Because of this the most chalks would not response with the SO2 and significant amounts of chalks are wasted. Moreover, the secondary products are the combination of CaSO4, CaO and CaCO3, so the only way to control them is dumping which might cause the salinized land.

Afterburning absorbing is an efficient approach including wet limestone, wet soda ash/caustic lime spray dryer, circulating lime reactor and sodium bicarbonate/trona injection to regulate the SO2, however, it also has irrefusable disadvantages: the finance. After the advanced two step there's a lot of SO2 in the offgas, most of which is CO2, so that afterburning absorbing usually is extremely expensive. Moreover such technology has a great deal of problems including the corrosion on equipments, pipeline blocking and the lack of material use ratio.

Discussion

Rationale

Personally, the basic solution to control the sulfur dioxide from the coal, is to split up the sulfur element from the coal ore before burning. In other words, to forbide the shaping of sulfur dioxide is the ultimate way to control it. This kind of ideas is not impossible. If we can make most of the sulfur factor separated from the coal before burned into sulfur dioxide, we do not need the afterburn aborbing.

Personally people should use another aspect to take into account the coal burning. The coal ore is contain FeS2, ash content and organic organizations. After the pretreatment, the vast majority of the FeS2 would be remove from the coal ore, so most of the substance left is organics and ash content.

In the fluidized bed, the coal would be transfor into gas, nearly all which is CO2 and sulfide gas. Fortunately the CO2 molecule organizationis nonpolar, and the almost all of sulfide gas is polar molecule, such as SO2. As we know gaseous phase and solid phase don't have the material difference, nowdays the magnetic force is employed widely in the solid waste control. So it can be done that use the magnetic force in separating two sorts of gas which have dissimilarities in magnetism.

Problems may meet and solution

The biggest problem people may meet is the distinctions between CO2 and sulfur dioxide are too small. This sort of force is merely just a little bigger than VDW(Van der Waal's force), it is impossible to split up all the CO2 and sulfide gas completely.

The solution to solve this problem actually is very easy, which is magnify the dissimilarities of force suffered. As we realize, at the same temperature and pession, the density of SO2 is bigger than that of CO2, which means the climbing velocity of CO2 is bigger than SO2. All the factories need chimneys which are being used to allow off gas to upper atmosphere to forbid the impact on daily life. If we add a magnetic field at the bottom of the chimney, it is sure CO2 would climb up much faster than SO2. That means we can magnify the variations of suffered force between SO2 and CO2.

The second problem of this view is how to gather the SO2. In my way, it is still to utilize the magnetic force.

The chimney in my plan is not simple one, it will the a concentric tube. There would be a lot of interspace all over the inside tube, which is utilized to separate the SO2 from the off gas. In the complete chimney, there will be a magnetic field, so that SO2 in the off gas would suffer the magnetic force which is able to make the SO2 stepped on the within tube. The outside tube is obfurage, so that SO2 wouldn't normally be discharged in to the atmosphere.

The last problem is finance. It appears that the technologies and skills used nowdays play an improved role in financial problems than the method mentioned above because of the high cost of basic built and daily power consumption.

Although I can not submit the compellent datas about the basic built and daily consumption, I strongly think that it performs better on the finance than the technologies and skills used now. Most skills of afterburning absorb would consume 15% electronic of the total vield for power plant. Which means only 85% power is useful. Alternatively the power consumed in establishing magnetic field is actually much less. All of the power plants in the world could have chimneys, therefore the basic building cost wouldn't normally be unacceptable. Furthurmore the secondary product: sulfur dioxide is the resource of manufacturing vitriol. For me, the consumption in power even would be significantly less than the amount of money earned from the secondary product.

Advantages and disadvantages

In comparison of some other technologies and skills, the best advantage of magnetic force is not a secondary pollution. No real matter what kind of skills used will have the problem of secondary pollution, including the combination of CaCO3 and CaSO4. These substances can't be recycled and don't have financial values, the simple managements such as landfill may cause the salinization and soil erosion. On the other hand the secondary products of the magnetic method is the combination of SO2 and CO2. This mixture can react with O2 under the catalysis of V2O5 to produce vitriol which may be the chemical engineering material. Furthurmore, this approach is extremely ideal for the 3rd World Countries. As we realize, due to financial problems environmentally friendly problems in the 3rd World Countries usually are usually negelected. Controlling the sulfur dioxide is a heavy burdon on the companies and coutries of the Third World. If they can gain monetary advantages from controlling SO2, it is obvious that there would not be any problems on the popularize in the 3rd World countries.

However, it also has some problems the most evident an example may be the challenge of strainaway rate. Due to the restriction of circumstance, I can't do any experiment as yet, so nobody knows how much the strainaway rate is. Probably the most urgent and effective solution does experiments. Any valuable and successful technologies and skills derive from doing a mass of experiment to find problems and change the process. Moreover it seems that to reach the prospective mentioned above, there would be a simple but endless process, which means it is only suitable to the sweeping factories.

Conclusion

In conclusion, just how that author submit obviously is a new aspect to regard the control of sulfur dioxide. After more than a century research on the original methods, they are all extremely ripe and difficult to improve. The magenic approach has the innate superiorities in comparision of the traditional ways. It is a definit physical technology which means there wouldn't normally be any new extra pllutant to harm the environment. Moreover compared with the other new methods researched now, it is incredible convinient. All of the basic building can be remaked from the prevailing equipments such as chimney and fluidized bed. In developing countries such as China and Africa countries that are not willing to pay attention on the environmenal protection, this technology can enhance their enthusiasm, because they can gain a higher economical benefits from the secondary products: vitrial with only a little investment. Although you may still find some undeniable problems on this magenic way, it must be a valuable toward to research.

The method mentioned in this paper is dependant on the 4 years experience in studying environmental subject of the writer. Even though the perspective and theoretical knowledge are sometimes naive and idealize, I strongly think that this method must be valuable. Not merely because the method itself, but also the aspect to deliberate and research. Environmental science is a wide ranged major which is not restricted in chemistry or biology, but also physics, physical chemistry, manage and biochemistry. The staff of protecting environment should expanse their own field of vision to all the relational knowledge rather than the major itself. In such a career, not matter the organizations and physical properties, not matter the fields people consentrate on, as environment protection workers, we can all learn a lot of things and acquire inspiration from the whole science and engineering region.

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