Separation Treatment Of Gasification Coal Tar Residue And Application On Phenolic Wastewater

Coal tar residue(CTR)are a kind of toxic and hazardous industrial solid waste which pose serious threats to the environment,however it can be regarded as a kind of high value of secondary energy sources which contains high fixed carbon,organic volatile and high calorific value.Therefore,it is necessary to rationally deal with CTR and recover or use efficiently as resources and energy from CTR.Although some technologies have being industrialized recently,there still exist some problems such as energy consumption,equipment cost,secondary pollution,and so on.Especially the CTR from coal gasification process which is called as gasification coal tar residue(GCTR)are rarely discharged and piled up as a waste in plant.This poses a serious threat to the surrounding environment nearby and results in a great waste of resources.In this paper,the utilization and treatment of GCTR were systematically studied through investigation of basic properties and toxicity,analysis of combustion characteristics and toxicity of pre-combustion release,solvent extraction separation,preparation of powder activated carbon and treatment of phenolic wastewater,the whole conclusions are as follows:1.GCTR is a kind of high value of secondary energy sources which contains high fixed carbon and organic volatile,as well as high calorific value.GCTR are mainly composed of aromatic structural compounds including 61.68%PAHs monitored by EPA.Some of them are easy to volatile,and the amount of carbon residue is about 43%.2.There has more than 30 mass loss from GCTR before 400?,and this volatile can not burn to release heat,but escape from sample and flow into the air in form of gases,and 8%ash is left.Moreover,the faster heating rates corresponding with higher ignition temperature for the heat transfer lag at higher heating rates.There are more than 30 kinds of organic matters detected in the emissions of GCTR as heated at 50? for 3h.Among them,the four compounds monitored by EPA are found with relative contents of 5.69%.The total content of the four compounds reaches 0.039mg per gram CGTR.The content of naphthalene is the highest,0.023mg per gram CGTR.The gas chromatogram shows that there have more than 108 kinds of peaks distributed in the emissions of GCTR when heated at 360? for 10 min.The total relative content of the eight PAHs is more than 36.37%,and the total absolute content reaches up to 20.01 mg per gram CGTR.The relative content of phenanthrene is the highest within eight PAHs,5.60 mg per gram GCTR.The next is fluoranthene,4.79 mg per gram GCTR.These results indicate that there are many highly toxic substances escaping from the GCTR under the pre-combustion stage and mainly exist in the tar component.3.Ethyl acetate,dimethyl carbonate and butyl acetate are optimized as extracting solvents from 22 solvents with low toxicity,economic,low boiling and good extraction rate.The GCTR were separated by ultrasonic extraction with the three solvents,and the highest extraction rate are 32.08%,29.25%and 29.24%,respectively,at room temperature,80 min,4 times extraction and the ratio of solvent to GCTR being 8:1.The GCTR were separated by agitation extraction with Ethyl acetate and the extraction rate above 30.58%was obtained when the ratio of EAC to GCTR and the stir time are 2 mL/g and 30min extracting 3 times at room temperature,respectively.4.The samples including GCTR and its separated substances were analyzed by using FTIR,GC/MS and DSC-TGA.Those results indicate that EA has a strong extraction capacity and can extract a certain number of aromatic compounds from GCTR.Compared with the GCTR and the extracted tar,the extracted residue from GCTR is relatively steady,and have the advantages of low ignition,more eco-friendly,fully burned,large combustion heat.Finally,A preliminary extraction and solvent recovery process with high efficiency and lower cost was established.5.The optimized preparation conditions of powder activated carbon with extracted residue is:the ratio of KOH/C4g/g,activation temperature 850? and activation time 30min,carbonization temperature 450? and carbonization time 30min.The activated carbon obtained has an iodine value 2023.11mg/g,total pore volume of 0.92 cm3/g,specific surface area of 1981 m2/g and mean pore sizes of 2.75 nm,which belongs to the meso-pore and micro-pore active carbon.The particle size of activated carbon is fine and can be dispersed evenly in solution.The color of Congo solution changes from red to pale pink after adsorbed within 3 min,and near colorless within 8 min.A fast magnetic separation can be realized by using a certain magnetic field.The separated residue and activated carbon are analyzed by XPS and XRD.The results show that there has C,O,N,Fe,Ca and Si in two samples surface and more Fe in activated carbon.This is due to the oxidation-reduction reaction(Fe2O3+C?Fe+CO2)occured and triggering the relative content of Fe increased in activated carbon,making its magnetic separation enhanced.6.The removal rate of phenol in water with powder activated carbon is very fast and has a rapid separate in the magnetic field.The phenol can be reduced from 100 mg/L to 3 mg/L in 50mL waste water under the condition of room temperature,5 min,pH=7.3 and 0.1g activated carbon.The sorption kinetics data fit the pseudo second order model,and the equilibrium adsorption value by fitting are relatively close to the experimental data(48.66 mg/g(296.15 K),48.56 mg/g(313.15 K),47.40 mg/g(328.15 K)).The adsorptive process conforms to Freundlich model,and the fitting parameter KF=24.08 and n>1.This shows that the powder activated carbon can be used to adsorb phenol from water and shows the faster adsorption speed,better adsorbability and high adsorption capacity,and adsorption for phenol is an endothermic process.