SO2 is an sort of industry air pollution largely from oil and coal ingestion, industry activities and traffics.According to research of EAP ( U.S. Environmental Protection Agency ) more than 100 million dozenss sulphur dioxide is discharged into the ambiance every twelvemonth wholly over the world.In the nature, most of the sulfur emanations are in the H2S ( hydrogen sulfide ) , CS2 ( C disulphide ) , COS ( carbonyl sulfide ) and some organic compouds.Through combustion, these organics which contain sulphur component discharge the sulfur dioxide to the ambiance, which is able to take serious environmental job and injury homo ‘s health.SO2 pollution may do workss dead in a highly high velocity, and is dissolved easy into the air current, which may do the acid rain that may distroy the outdoor buildings.The most significantly, high concentrated SO2 in the ambiance is able to kill people or cause serious ailments including bronchitis, emphysema and oculoglandular conjunctivitis.Moreover, the sulphuric acid, is a secondary pollutant.When sulfur dioxide is involved in extra chemical reactions, it can respond with O and H2O to sulfuric acid which is the component of ‘acid rain’. ( NATHANSON, J. ( 1986 ) )
By and large, to work out the serious environmental job, there are two research torwards in taking sulphur dioxide: pretreatment and afterwards absorbing. No affair what methods people use were all included in such two research waies.
Pretreatment means separate the sulfur component from the coal mineral before it was burned. Because the chief organises of sulfur component in coal are FeS2 and organic S, by and large, in industry people frequently use independent ways to make separation. For the inorganic S including FeS2, the most traditional manner is gravitative segregation which means separate the ore incorporating sulfur component from the coal with the differences in denseness. Such method is highly fiscal and proficient simple, nevertheless its effects sometimes are limited. Because of the differentia of the coal ore all over the universe, the strainaway rate of the sulfur component is extremely different. In some country the gravitative segregation can take about 90 % of the sulfur component in coal ore, while in some certain coal mines of 40 % of the entire S content can be wiped off.
For the organic S component, it seems that there is non a efffective pretreatment attack to work out it. What people can make is merely absorb the SO2 from firing organic sulfocompound. Unfortunately, because of the complicated organisation of organic affair, by and large, the S contained in the coal ore would be burned in to a series of sulfocompounds including H2S, CS2, SO, SO2 alternatively of merely SO2.So before people assimilate the SO2, people have to transform these compounds into SO2 foremost. Nowdays the most common manner is fluidized bed.
Fludized bed is a sort of organisation for gasification of coal which is created by Fritz Winkler of Germany on December 16, 1921. Since the early 1960s, Douglas Elliott put frontward that the coal should be burned alternatively of vaporizing coal in a bubbling fluidized bed, because the it can bring forth steam by plunging boiler tubings. In 1982, the first CFB boiler which can fire low-grade coal was built in the Vereingte Aluminum Werke at Luenen, Germany in 1982 which is designed entirely for the supply of steam and heat.
The general gas-solid fluidizetion has 5 major application: Energy transition, Petro-chemical processing, Mineral processing, Chemical and pharmaceutical and Physical processing, and the basic 1 is energy transition.
FIGURE 1.2 Schematic of a high temperature fluidized bed gasifier
In general coal would be fed into bubbling fludized bed at 950 grade. Steam would be fed into the base of the fluidized bed through a sparge pipe-type of distributer. Then the coal would go forth the hot solids in the bed and the cleaned and used gasification merchandises leave the bed from the top. In this procedure limestone ( CaCO3 ) and dolomite ( CaCO3·MgCO3 ) would be assorted with the coal ores to abstract the SO2 from the burning.The chemical equation is as follow:
( 1.1 )
After the fluidized bed measure, there is still about 20 % SO2 left in the offgas. To work out this SO2, people need some engineerings including Calcium-Based Chemical reactions and Sodium-Based Reactions, which were called afterburning absorbing.
Until now, there is non a inexpensive and effectual approach.The effectual methods normally are expensive and lay a heavy burdon on finance, at the same clip, the inexpensive 1s disable to take the sulfur dioxide satisfactorily.
The major information of this paper includes the benefits and defects of the traditional ways commanding the SO2, the rational of the new facet: magnetic method, the jobs may run into and the solutions of this approach..The ultimate intent of the assignment is to indicate out a solution both fiscal and efficient.All the experiments and theories mentioned in this essay are based on theories and logical tax write-offs.
Nowdays in engineering aspect people are able to command the SO2 lease efficaciously, after all the stairss the SO2 discharged into the ambiance is less so 1 % . Materials of these engineerings are all hackneved, . Furthermore, some certain engineerings can bring forth a series of cost efficient 2nd merchandises such as vitrol and compound fertilisers.
Pretreatment is best method to command the S dioxide, personally. Not merely because the FeS2 can be separated from the coal ore easy, but besides FeS2 can be another utile stuffs in industry. Because of the characters of coal mines, the associate ore of coal is FeS2 by and large. As a consequence the FeS2 ore occupies a large portion of coal mines in anywhere of the universe, and the FeS2 ore is the most common stuff of puddling. So the pretreatment is a both efficient and fiscal attack.
Fluidized bed is the 2nd stairss of the whole S dioxide, the absobents of fluidized bed are really inexpensive and common. So this engineering resently is used widly in the states which are busying a spacious country such as China and American as a normal accomplishment. And such engineering is extraordinary suit for the large-scale mills.
Afterburning absorbing is the most efficient manner to command the S dioxide dispatching regardless of the concentration. The ultimate consistency of SO2 in off gas which is disposed by the afterburning absorbing normally is less than 5 % .
In drumhead, the engineering resent used in the SO2 control are extremely mature, nevertheless there are still some disadvantages can non be ignored.
Although pretreatment is the most efficient and fiscal method to command the S dioxide, it has the deadliest defect: the limitation of country. Because of the difference of the organisation of coal ore in different country, such engineering disables to be spreaded.
For the fluidized bed the jobs are secondary merchandises and the processing ratio.When the chalks go into the boiler the active rule, CaCO3 would be resolve into CaO and CO2. The burnt CO2 would sepatate out and enlarge the interspace on the CaO to organize the lacunose CaO which can response with the SO2 easy. However it is impossible to do all of the CaO be the CaSO4, because the sulphating would do the interspace fullfilled by CaSO4. As a consequence the most chalks would non response with the SO2 and a great trade of chalks are wasted. Furthermore, the secondary merchandises are the mixture of CaSO4, CaO and CaCO3, so that the lone manner to pull off them is dumping which may do the salinized land.
Afterburning absorbing is an efficient attack including wet limestone, wet sodium carbonate ash/caustic calcium hydroxide spray drier, go arounding calcium hydroxide reactor and Na bicarbonate/trona injection to command the SO2, nevertheless, it besides has irrefusable disadvantages: the finance. After the advanced two measure there is a batch of SO2 in the offgas, most of which is CO2, so that afterburning absorbing normally is highly expensive. Furthermore such engineering has a great trade of jobs such as the corrosion on equipments, grapevine blocking and the deficiency of stuff usage ratio.
Personally, the basic method to command the S dioxide from the coal, is to divide the sulfur component from the coal ore before firing. In other words, to forbide the defining of S dioxide is the best manner to command it.This sort of thoughts is non impossible. If we can do most of the sulfur component separated from the coal before burned into S dioxide, we do non necessitate the afterburn aborbing.
Personally people should utilize another facet to believe about the coal combustion. The coal ore is consist of FeS2, ash content and organic organisations. After the pretreatment, about all of the FeS2 would be take 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 bulk of which is CO2 and sulfide gas. Fortunately the CO2 molecule organizationis nonionic, and the most of sulphide gas is polar molecule, such as SO2. As we know gaseous stage and solid stage do non hold the stuff difference, nowdays the magnetic force is used widely in the solid waste control. So it is possible that use the magnetic force in dividing two sorts of gas which have differences in magnetic attraction.
Problems may run into and solution
The biggest job people may run into is the differences between CO2 and sulfur dioxide are excessively little. This sort of force is merely a small bigger than VDW ( Van der Waal ‘s force ) , it is impossible to divide all of the CO2 and sulfide gas wholly.
The method to work out this job really is really easy, which is magnify the differences of force suffered. As we know, at the same temperature and pession, the denseness of SO2 is bigger than that of CO2, that means the mounting speed of CO2 is bigger than SO2. All the mills need chimneys which are used to allow the off gas to upper atmosphere to prohibit the impact on day-to-day life. If we add a magnetic field at the underside of the chimney, it is certain that CO2 would mount up much faster than SO2. That means we can amplify the differences of suffered force between SO2 and CO2.
The 2nd job of this sentiment is how to garner the SO2. In my manner, it is still to utilize the magnetic force.
The chimney in my program is non simple one, it should the a homocentric tubing. There would be a batch of interspace all over the inside tubing, which is used to divide the SO2 from the off gas. In the whole chimney, there would be a magnetic field, so that SO2 in the off gas would endure the magnetic force which is able to do the SO2 tally over the inside tubing. The outside tubing is obfurage, so that SO2 would non be discharged into the ambiance.
The last job is finance. It seems that the engineerings and accomplishments used nowdays play a better function in fiscal jobs than the method mentioned above due to the high cost of basic built and day-to-day power ingestion.
Although I can non subject the compellent information about the basic built and day-to-day ingestion, I strongly believe that it performs better on the finance than the engineerings and accomplishments used now. Most accomplishments of afterburning absorb would devour 15 % electronic of the entire vield for power works. That means merely 85 % power is utile. On the other manus the power consumed in set uping magnetic field is evidently much less. All the power workss in the universe would hold chimneys, so the basic edifice cost would non be unacceptable. Furthurmore the secondary merchandise: sulfur dioxide is the resource of fabricating sulfuric acid. In my sentiment, the ingestion in power even would be less than the money earned from the secondary merchandise.
Advantages and disadvantages
In comparing of any other engineerings and accomplishments, the ultimate advantage of magnetic force is no secondary pollution. No affair what sort of accomplishments used now have the job of secondary pollution, such as the mixture of CaCO3 and CaSO4. These substances can non be recycled and do non hold fiscal values, the simple directions such as landfill may do the salinization and dirt eroding. On the other side the secondary merchandises of the magnetic method is the mixture of SO2 and CO2. This mixture is able to respond with O2 under the contact action of V2O5 to bring forth sulfuric acid which can be the chemical technology stuff. Furthurmore, this attack is highly suited for the Third World Countries. As we know, because of the fiscal jobs the environmental jobs in the Third World Countries normally are normally negelected. Controling the S dioxide is a heavy burdon on the companies and coutries of the Third World. If they can derive economic benefits from commanding SO2, it is obvious that there would non be any jobs on the popularize in the Third World states.
However, it besides has some jobs the most apparent one is the job of strainaway rate. Due to the limitation of circumstance, I can non make any experiment until now, so nobody knows how much the strainaway rate is. The most pressing and effectual solution is making experiments. Any valuable and successful engineerings and accomplishments are based on making a mass of experiment to happen jobs and alter the procedure. Furthermore it seems that to make the mark mentioned above, there would be a simple but eternal procedure, that means it is merely suited to the sweeping mills.
In decision, the manner that writer put frontward evidently is a new facet to see the control of S dioxide. After more than 100 old ages research on the traditional methods, they are all highly mature and hard to better. The magenic attack has the innate high qualities in comparision of the traditional ways. It is a definit physical engineering which means there would non be any new excess pllutant to harm the environment. Furthermore compared with the other new methods researched now, it is unbelievable convinient. All the basic edifice can be remaked from the bing equipments such as chimney and fluidized bed. In developing states such as China and Africa states which are non willing to pay attending on the environmenal protection, this engineering can better their enthusiasm, because they can derive a high economical benefits from the secondary merchandises: vitrial with merely a small investing. Although there are still some undeniable jobs on this magenic manner, it must be a valuable toward to research.
The method mentioned in this paper is based on the 4 old ages experience in analyzing environmental topic of the writer. Although the position and theoretical cognition are sometimes naif and idealise, I strongly believe that this method must be valuable. Not merely because the method itself, but besides the facet to consider and research. Environmental scientific discipline is a broad ranged major which is non restricted in chemical science or biological science, but besides natural philosophies, physical chemical science, manage and biochemistry. The workers of protecting environment should expanse their ain field of vision to all the relational cognition alternatively of the major itself. In this calling, non count the organisations and physical belongingss, non count the Fieldss people consentrate on, as environment protection workers, we can all larn a batch of things and get inspiration from the whole scientific discipline and technology part.