Study On The Generation Characteristics Of Environmental Load During The Gasification-Reforming Of Refuse Derived Fuel

With the global shortage of fossil fuels and the ever-increasing awareness of environmental protection in every countries,making use of the pyrolysis of municipal solid waste to produce derived fuel and actively developing new and efficient waste recycling technologies can not only solve the problem of urban garbage pollution,but also provide a new way to alleviate the existing energy shortage situation in our country.In this study,RDF(Refuse Derived Fuel)was raw material,an existing gasification-reforming experimental setup was used to carry out the catalytic pyrolysis experiment of RDF.By setting up purification system and adjusting the operation agents which including gasification temperature,steam addition rate(S/C)and catalyst utilization,during this process the generation characteristics of environmental load was analyzed and effective methods to curb the pollutants generated was explored in order to establish an environmental friendly MSW gasification-reforming system.As known,tar is the most cumbersome and problematic parameter in any gasification process which affected by operational parameters significantly.The composition of the tar is very complicated and changeable.What's more,condensed tar was liable to plug the pipeline and cause failure of obtaining qualified syngas.This paper aims to investigate the characteristics of tar formation and conversion during gasification as a function of operating parameters,and a series of the relevant purification treatment was carried out to reduce the environmental load.Results show that:(1)Tar associated with waste pyrolysis process was divided into non-water-soluble tar and water-soluble tar.The non-water-soluble tar mainly existed in the filter unit,partially condensed on the bottle wall of the scrubbing unit,the content of polycyclic aromatic hydrocarbons(PAHs)was no less than 98%and the content of naphthalene was the highest.Biphenyl,Fluorene,Phenanthrene and pyrene were the main representatives of PAHs as well.Water-soluble tar mainly existed in the scrubbing water of the scrubbing unit which contained the most of Phenol and a small amount of PAHs.(2)The temperature increase was benefit to the cracking and conversion of tar,causing the concentration of tar reduced.However,when the gasification temperature was above 800? the tar content increased rapidly with increasing temperature.At the temperature of 800?,the tar concentration and the phenol concentration generated in the gasification reactor were the lowest.When the temperature was as low as 700? the concentration of polycyclic aromatic hydrocarbons reached the lowest.while the degree of gasification was insufficient and the utilization of raw materials was low at this temperature.(3)Adding steam during the operation process could promote the reforming reaction of tar and reduce the tar concentration effectively.When the steam addition S/C was 3.6,the tar concentration was the lowest and the conversion rate of tar was as high as 26.84%.At the same time,the conversion rate of naphthalene and biphenyl were more than 60%.Increasing steam addition couldn't inhibit the phenol production.The ideal steam addition for phenol was that S/C=1.2.(4)Nickel-based catalysts doped with alkali metal additives have higher stability and activity.It can effectively inhibit the corrosion and acidification of tar on the catalyst.In this experiment,the reduction rate of tar concentration reached up to 77.04%under the effect of Ni-based catalyst which mixed with Mg,Ca,Ce and Al as additives.The decrease of naphthalene and phenol concentration was the most significant among these pollutants,the concentration of PAHs with more rings increased on the contrary.(5)The activated carbon adsorption method and UV-Fenton method were used to purify the environmental pollutants contained in the scrubbing water.Commercial activated carbon had a relatively weak adsorption capacity on phenol and PAHs.Results of UV-Fenton method showed that the degradation rate of phenol was the best when the reaction time was 40 min,and the average degradation rate of PAHs reached best when the reaction time was 50 min.The more rings of PAHs with,the higher degradation rate it has.Besides,when the reaction time was 40 min,the degradation of tar by UV-Fenton method was much better than the traditional Fenton method under the same conditions.