Control Of Sulphur Dioxide Environmental Sciences Essay

SO2 is an kind of industry air pollution mostly from oil and coal consumption , industry activities and traffics.According to research of EAP(U.S. Environmental Protection Agency) more than 100 million tons sulphur dioxide is discharged into the atmosphere every year all over the world.In the nature,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 which contain sulphur element discharge the sulphur dioxide to the atmosphere,which is able to lead serious environmental problem and harm human’s health.SO2 pollution may cause plants dead in a extremely high speed,and is dissolved easily into the wind,which may cause the acid rain that may distroy the outdoor buildings.The most importantly,high concentrated SO2 in the atmosphere is able to kill people or cause serious ills including bronchitis, emphysema and oculoglandular conjunctivitis.Moreover,the sulfuric acid,is a secondary 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 matter what methods people use were all included in such two research directions.

Pretreatment means separate the sulfur element from the coal mineral before it was burned. Because the main organises of sulfur element in coal are FeS2 and organic 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 which means separate the ore containing sulfur element from the coal with the differences in density. Such method is extremely financial and technical simple, however its effects sometimes are limited. Because of the differentia of the coal ore all over the world, the strainaway rate of the sulfur element is highly different. In some area the gravitational segregation can remove approximately 90% of the sulfur element in coal ore, while in some certain coal mines of 40% of the total sulfur content can be wiped off.

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For the organic sulfur element, it seems that there is not a efffective pretreatment approach to solve it. What people can do is just absorb the SO2 from burning organic sulfocompound. Unfortunately, because of the complicated organization of organic matter, generally, the sulfur contained in the coal ore would be burned in to a series of sulfocompounds including H2S,CS2,SO,SO2 instead of only SO2.So before people assimilate the SO2, people have to transform these compounds into SO2 first. Nowdays the most common way is fluidized bed.

Fludized bed is a kind 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 is designed exclusively for the supply of 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 one is energy conversion.

FIGURE 1.2 Schematic of a high 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 through 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 (CaCO3·MgCO3) 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 solve this SO2, people need some technologies including Calcium-Based Reactions and Sodium-Based Reactions, which were 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 remove the sulphur dioxide satisfactorily.

The major information of this 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 ultimate purpose of the assignment is to point out a solution 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 are able to control the SO2 letting effectively, after all the steps the SO2 discharged into the atmosphere is less then 1%. Materials of these technologies are all hackneved,. Moreover, some certain technologies can produce a series of cost efficient second products such as vitrol and compound fertilizers.

Pretreatment is best 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. Because of the characters of coal mines, the associate ore of coal is FeS2 generally. As a result the FeS2 ore occupies a big part of coal mines in anywhere of the world, and the FeS2 ore is the most common material of puddling. So the pretreatment is a both efficient and financial approach.

Fluidized bed is the second steps of the whole sulfur dioxide, the absobents of fluidized bed are very cheap and common. So this technology resently is used widly in the countries which 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 control the sulfur dioxide discharging regardless of the concentration. The ultimate consistence of SO2 in off gas which is disposed by the afterburning absorbing usually is less than 5%.

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

Disadvantages

Although pretreatment is the most efficient and financial method to control the sulfur dioxide, it has the deadliest defect: the restriction of area. Because of 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. However it is impossible to make all of the CaO be the CaSO4, because the sulphating would make the interspace fullfilled by CaSO4. As a result the most chalks would not response with the SO2 and a great deal of chalks are wasted. Moreover, the secondary products are the mixture of CaSO4, CaO and CaCO3, so that the only way to manage them is dumping which may 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 control the SO2,however, it also has irrefusable disadvantages: the finance. After the advanced two step there is 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 such as the corrosion on equipments, pipeline blocking and the lack of material use ratio.

Discussion

Rationale

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

Personally people should use another aspect to think about the coal burning. The coal ore is consist of FeS2, ash content and organic organizations. After the pretreatment, almost all of the FeS2 would be remove out of 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, the majority of which is CO2 and sulfide gas. Fortunately the CO2 molecule organizationis nonpolar, and the most of sulfide gas is polar molecule, such as SO2. As we know gaseous phase and solid phase do not have the material difference, nowdays the magnetic force is used widely in the solid waste control. So it is possible that use the magnetic force in separating two kinds of gas which have differences in magnetism.

Problems may meet and solution

The biggest problem people may meet is the differences between CO2 and sulfur dioxide are too small. This kind of force is only a little bigger than VDW(Van der Waal’s force), it is impossible to separate all of the CO2 and sulfide gas completely.

The method to solve this problem actually is very easy, which is magnify the differences of force suffered. As we know, at the same temperature and pession, the density of SO2 is bigger than that of CO2, that means the climbing velocity of CO2 is bigger than SO2. All the factories need chimneys which are used to let the 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 that CO2 would climb up much faster than SO2. That means we can magnify the differences of suffered force between SO2 and CO2.

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

The chimney in my plan is not simple one, it should the a concentric tube. There would be a lot of interspace all over the inside tube, which is used to separate the SO2 from the off gas. In the whole chimney, there would be a magnetic field, so that SO2 in the off gas would suffer the magnetic force which is able to make the SO2 run over the inside tube. The outside tube is obfurage, so that SO2 would not be discharged into the atmosphere.

The last problem is finance. It seems that the technologies and skills used nowdays play a better role in financial problems than the method mentioned above due to 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 believe 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. That means only 85% power is useful. On the other hand the power consumed in establishing magnetic field is obviously much less. All the power plants in the world would have chimneys, so the basic building cost would not be unacceptable. Furthurmore the secondary product: sulfur dioxide is the resource of manufacturing vitriol. In my opinion, the consumption in power even would be less than the money earned from the secondary product.

Advantages and disadvantages

In comparison of any other technologies and skills, the ultimate advantage of magnetic force is no secondary pollution. No matter what kind of skills used now have the problem of secondary pollution, such as the mixture of CaCO3 and CaSO4. These substances can not be recycled and do not have financial values, the simple managements such as landfill may cause the salinization and soil erosion. On the other side the secondary products of the magnetic method is the mixture of SO2 and CO2. This mixture is able to react with O2 under the catalysis of V2O5 to produce vitriol which can be the chemical engineering material. Furthurmore, this approach is extremely suitable for the Third World Countries. As we know, because of the financial problems the environmental problems in the Third 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 economic benefits from controlling SO2, it is obvious that there would not be any problems on the popularize in the Third World countries.

However, it also has some problems the most evident one is the problem of strainaway rate. Due to the restriction of circumstance, I can not do any experiment until now, so nobody knows how much the strainaway rate is. The most urgent and effective solution is doing experiments. Any valuable and successful technologies and skills are based on doing a mass of experiment to find problems and change the process. Moreover it seems that to reach the target mentioned above, there would be a simple but endless process, that means it is only suitable to the sweeping factories.

Conclusion

In conclusion, the way that author put forward obviously is a new aspect to regard the control of sulfur dioxide. After more than 100 years research on the traditional 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 would not be any new extra pllutant to harm the environment. Moreover compared with the other new methods researched now, it is incredible convinient. All the basic building can be remaked from the existing equipments such as chimney and fluidized bed. In developing countries such as China and Africa countries which are not willing to pay attention on the environmenal protection, this technology can improve their enthusiasm, because they can gain a high economical benefits from the secondary products: vitrial with only a little investment. Although there are still some undeniable problems on this magenic way, it must be a valuable toward to research.

The method mentioned in this paper is based on the 4 years experience in studying environmental subject of the author. Although the perspective and theoretical knowledge are sometimes naive and idealize, I strongly believe that this method must be valuable. Not only 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 workers of protecting environment should expanse their own field of vision to all the relational knowledge instead of the major itself. In this 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.