| Coal coking industry occupies an important position in the field of energy and chemical industry in China.With long process and many adverse reactions,coal coking may produce a large number of solid wastes with complex compositions.Most of these solid wastes contain pollutants such as polycyclic aromatic hydrocarbons and heavy metals,and improper treatment,utilization and disposal can cause serious environmental pollution.Therefore,the study on the composition and pollution characteristics of coal coking solid waste is of great significance for improving the utilization and disposal technology and safety management level of coal coking solid waste.Coal coking solid wastes were chosen as the research object in this paper,the coal coking process and waste production nodes are systematically analyzed.The classification method and list representing the common characteristics of coal coking solid waste are constructed based on the classification principle of generation sources.Based on the classification results of common generation sources,the composition characteristics and pollution characteristics of coal coking solid waste are studied.At the same time,the secondary pollution characteristics of tar residue during incineration and disposal were discussed,and the following main research results were obtained:（1）The classification method and list of common generation sources of solid waste from coal coking were constructed.39 kinds of solid waste from coal coking production process were determined through industrial node analysis.Based on the principle of source classification and analysis,the coal coking solid waste with similar generation source characteristics was classified into four common generation sources:gas purification unit,by-product deep processing unit,screening and dust removal unit,and waste water treatment unit,and a classification list of common generation sources of coal coking solid waste was formed.（2）The composition characteristics of solid waste in different common source of coal coking were identified.In the gas purification unit,the content of solid waste volatile and fixed carbon is high,while the content of moisture and ash is low.The main component element is C,and the material composition is mainly Al2O3,Fe2O3 and Si O2.The by-product deep processing unit has the highest content of solid waste volatile,higher content of fixed carbon,lower content of moisture and ash.The main component element is C,and Fe2O3 is the main material composition.The content of fixed carbon in solid waste of the screening and dust removal unit is high,while the content of moisture,ash and volatile matter is low.The main component element is C,and Si O2 and Al2O3 are the main material components.Solid wastes in the wastewater treatment unit have the highest content of moisture and the lowest content of fixed carbon,the content of ash and volatile is high.The main elements are C and O,and the main material composition is Fe2O3.（3）The characteristics of pollutants in solid waste of different common source of coal coking were identified.The PAHs content of solid waste from the gas purification units ranged from 9638～271800mg/kg,mainly consist of 2～3 rings of PAHs,and the contents of heavy metals Pb,Cr,Zn and Ni were relatively high and Pb>Cr>Zn>Ni>Cu>Cd>As>Hg;The PAHs content of solid waste from the by-product deep processing unit was 59250～138190mg/kg,mainly composed of 4～6 rings of PAHs,and the heavy metal Pb content was high and Pb>Zn>Cr>Ni>Cu>Cd>As>Hg;The PAHs content of solid waste from the screening and dust removal unit ranged from 8.17～5172.20mg/kg,mainly consist of 4～6 rings of PAHs,and the content of heavy metals Cr,Cu,Zn and Pb was high and Cr>Cu>Zn>Pb>As>Ni>Cd>Hg;The PAHs content of solid waste from the wastewater treatment unit ranged from 278.04～6682.90mg/kg,which was mainly composed of 4～6 rings of PAHs,and the content of heavy metals Zn and Cu was relatively high and Zn>Cu>Ni>Cr>Pb>As>Cd>Hg.（4）The incineration characteristics of coal,tar residue and blended fuel（coal with20%tar residue）in air atmosphere were analyzed.The weight loss of coal mainly occurs at 400℃～850℃,and the weight loss rate is the largest at 680℃,and the total weight loss rate is 63.28%.The weight loss of tar residue can be divided into three stages.The first stage has the maximum weight loss rate at 140℃,the second stage is slow,and the third stage is the main stage with the maximum weight loss rate at 640℃,and the total weight loss rate is 90.81%.The weight loss of the mixed fuel is divided into three stages.The first stage is the maximum weight loss rate at 120℃,the second stage is not obvious weight loss,and the third stage is the maximum weight loss rate at 700℃,and the total weight loss rate is 80.51%.（5）The emission characteristics of PAHs and heavy metals from coal,tar residue and blended fuel（coal with 20%tar residue）incinerated at different temperatures were discussed.With the increase of incineration temperature,PAHs emission factors of coal incineration flue gas showed a trend of increase first and then decrease,tar residue showed a trend of decrease first ing and then increase,and mixed fuel showed a trend of gradually decrease.The flue gas is dominated by 2～3 rings of PAHs,and the bottom slag is dominated by 4～6 rings of PAHs.The distribution rate of PAHs in the flue gas is much higher than that of the bottom slag,and the incineration of PAHs poses a higher environmental risk to the atmosphere.With the increase of the incineration temperature,the emission factors of heavy metals in the flue gas showed an increase trend,with little change at 500～700℃and significant increase at 900～1200℃.The distribution of volatile heavy metals Cu,Ni and Cr in flue gas and bottom slag is not significantly affected by temperature.With the increase of temperature,the distribution of volatile heavy metals Pb,Zn,Cd and As in flue gas significantly increased,and the environmental risk to the atmosphere increased.This study constructed the coal coking solid waste source classification list,analyzed the common source of coal coking of solid waste and pollution characteristics of the typical coal coking solid waste incineration disposal of pollutants discharge characteristics of tar residue,provided the reference to establish a classification method based on the characteristics of solid waste also provided theoretical support and scientific basis for the use of coal coking waste disposal and safety management. |
