Degradation And Emission Of Pollutants During Co-processing Of Hazardous Waste In Texaco Gasifier

Industrial kilns co-processing technology has become one of the most important development tendency for the treatment of hazardous waste in the world.Texaco coal-water slurry gasifier(hereinafter referred to briefly as Texaco gasifier)has been widely applied to methanol and ammonia production process with the advantage of high reaction temperature,high carbon conversion efficiency and less impurity in syngas,the internal high temperature environment gave the possibility of co-processing of hazardous waste in it.The demand quantity of Texaco gasifier growing under the policy of clean energy and industrial development,so co-processing of hazardous waste in Texaco gasifier has important practical significance to improve the disposal capacity of hazardous waste in China.Now there has no research on the pollution control of co-processing of hazardous waste in Texaco gasifier.In our study,simulation test and field test were conducted to research the reaction rule,emission characteristics and distribution law of different pollutants in the gasifier during the co-processing process,pollution control requirements in the process were also proposed.Results shows that:(1)During co-processing of hazardous waste in Texaco gasifier,the temperature in gasifier ranged at 1330-1350℃,the pressure were stabled at 1.0-1.3 MPa and the gas production stabled at 12000-14000 Nm~3/h under both blank condition that slurry was made by clean water and coal and test condition slurry mixed with labeling agent of organics and heavy metals,the co-processing process has little impact on the operation stability of the gasifier.(2)When p-dichlorobenzene was used as the organic labeling agent in the co-processing process,the concentration of p-dichlorobenzene in syngas at Venturi scrubber exit,syngas at desulfurizing tower entrance,syngas at desulfurizing tower exit,high temperature black water flash steam,desulfurization solution regeneration tower exhaust gas,ammonia synthetic tower exhaust gas,carbon black,residue and recycled water were detected to calculate the destruction efficiency(DE)which is greater than 98%,improved organic matters could be fully degraded during the co-processing process.(3)Texaco gasifier co-processing of hazardous waste didn’t increase the emission risks of dioxin.The concentration of dioxin in high temperature black water flash steam,desulfurization solution regeneration tower exhaust gas,residue,carbon black and recycled water were all far below the standard limit both in China and abroad.It didn’t change the distribution trend of dioxin in waste water,exhaust gas and solid waste during co-processing process,of which 13%-16.37%PCDDs distributed in exhaust gas,0.91%-0.99%distributed in waste water,82.65%-86.09%distributed in solid waste.For PCDFs 6.10%-22.95%distributed in exhaust gas,0.59%-0.80%distributed in waste water,76.45%-93.10%distributed in solid waste.The concentration of dioxin was very low in liquid phase,which was more liable to distribute in gas phase and solid phase,the distribution in solid phase is much higher than that in gas phase.(4)Texaco gasifier co-processing of hazardous waste didn’t increase the emission risks of polycyclic aromatic hydrocarbons(PAHs).Under both blank condition and test condition,high temperature black water flash steam and recycled water need to be discharged after disposal for their concentration of PAHs are all above the relevant standard limit.It didn’t change the distribution trend of PAHs with different molecular weights in waste water,exhaust gas and solid waste during co-processing process.Of which 92.96%-93.68%2-3 ring PAHs distributed in exhaust gas,while 50.84%-71.66%4ring PAHs distributed in solid waste,and 85.3%-86.77%5-6 ring PAHs distributed in solid waste.Low molecular weight PAHs mainly distributed in exhaust gas,middle and high molecular weight PAHs mainly distribute in solid waste,the concentration of PAHs in waste water is generally low.(5)Texaco gasifier co-processing of hazardous waste didn’t increase the emission risks of heavy metal.Heavy metal mainly distributed in residue,carbon black and recycled water,which has low emission risk in exhaust gas.Of which 17.36%-40%semi-volatile heavy metals distributed in residue and carbon black,13.6%-19.3%distributed in recycled water.Volatile heavy metals mainly distributed in carbon black and syngas for 81.3%and28.9%respectively.Other heavy metals also mainly distributed in carbon black and recycled water for 4%-97%and 11%-88%respectively.In conclusion,co-processing of hazardous waste in Texaco gasifier didn’t increase the emission risks of the pollutants,organic matters were relatively fully degraded during the co-processing process.Texaco gasifier has the advantage to dispose hazardous waste of high moisture content,and may be widely used in the field of sludge disposal and other waste in the future.