Study On The Migration Of Pollutants In Fly Ash From Thermal Power Plants Under Different Compaction Conditions

Fly ash is an inevitable product of thermal power plants.With the continuous development of China's economy,the emission of fly ash continues to increase.At present,the comprehensive utilization rate of fly ash is still relatively low.An amazing amount of fly ash needs to be stored,every year,which has become a major factor limiting the development of thermal power plants.And fly ash will be leached by rain during its long-term storage,and the pollutants contained in the leaching filtrate may cause soil and groundwater pollution.At present,there are many related researches on fly ash,and there is a comprehensive understanding of the physical and chemical properties and leaching characteristics of fly ash.However,the feasibility study on the ash field anti-seepage measures is still relatively small.Then,In the process of landfill of fly ash,most of them are compacted,and most of the studies have not considered this actual situation.Therefore,this paper uses a power plant in Fenyang City as the research background to study the leaching characteristics of fly ash through leaching experiments;in the leaching experiment,the compaction of fly ash and soil under the ash field is changed?after named as The ash column experiment and soil column experiment?,analyze the migration law of pollutants;establish the hydrus-1d model of fly ash pollutants transported in the loess layer,and analyze the change of pollutant concentration with time at different depths.The results of leaching experiments show that there are 6 kinds of ion concentration in the fly ash leaching solution exceeding the groundwater class III water standard,which are Cd,Pb,Cr⁶⁺,Ni,F^-and SO₄^2-.Among them,Pb exceeded the standard most seriously,exceeding the standard multiple of 26.67 times.Most of the ion concentration in the fly ash leaching solution is higher than the concentration of the corresponding ions in the bottom slag.The concentration of most ions in the ash leaching solution is relatively higher than that of the ash field,The bottom slag has a similar phenomenon.The results of soil column experiments show that:?1?With the increase of compaction degree of Malan loess,the longer the leaching filtrate begins to flow out,the smaller the discharge flow.?2?SO₄^2-and F^-in fly ash can still detect higher concentrations in the leachate from the end of the experiment.The release of both ions reached the maximum in the soil column 3 with a compaction coefficient of 0.754 for the Malan loess,and the smallest in the soil column 5 with a compaction coefficient of 0.943,where in the concentration of SO₄^2-in the leaching solution was at the soil column 5 It is much smaller than the rest of the soil column.?3?The concentration of four heavy metal ions in fly ash decreased to 0 mg/L after a period of time.Comparing the ionic components before and after leaching of fly ash,it can be found that the release of these four ions is the largest in the soil column 5 with a compaction coefficient of 0.943 for Malan loess.The results of the gray column experiment show that:?1?With the increase of compaction of fly ash,the outflow time is longer of the gray column,the smaller the outflow.?2?The release of SO₄^2-and F^-anions from fly ash will last for a long time,and the emission of SO₄^2-and F^-decreases with the increase of fly ash compaction.?3?The release time of four heavy metal ions in fly ash is relatively short.The emission of the other three ions except Cd decreased with the increase of compaction of fly ash,and the emission of Cd was not much different among the five gray columns.The Hydrus-1d simulation results show that:The maximum migration depth of the six ions of SO₄^2-,F-,Ni,Cr⁶⁺,Cd and Pb after continuous leaching for 21 days in the compacted loess layer is between 130cm and 200cm.After the ions have migrated for a certain distance,the concentration begins to meet the?types of water standards in the Groundwater Quality Standard.The maximum migration depth and the maximum depth of the standard are Pb,which can be migrated to 198cm,and the standard is reached at a depth of 166cm or less.