Study On The Combustion Characteristics Of Oily Sludge And The Transformation Characteristics Of Heavy Metals During Combustion Of Oily Sludge Blended With Microalgae

Oily sludge is complex in composition,containing a large number of aging crude oil,wax,bitumen,benzene,phenol,onions,heavy metals and other substances.If not treated properly,it will easily cause serious pollution.Oily sludge has high value of recycling and utilization.It will have good environmental value and high economic value for the resource and harmless treatment of oily sludge.The mixing of oily sludge with microalgae can improve the combustion efficiency,influence the migration and transformation of heavy metals,and affect the behavior of NO_X and SO₂,but the related research is scarce.In this paper,the study was conducted on the basic combustion characteristics of oily sludge,microalgae and their mixtures,and the migration and transformation rules of heavy metals during combustion process by using thermal analysis technology and the combustion test and the software simulation method.At first,the combustion and kinetic characteristics of oily sludge,microalgae and their mixtures were studied on a thermogravimetric analyzer based on thermal analysis.The thermogravimetric experiments indicated that the combustion process of mixed fuel containing oil sludge and microalgae was divided into 4 stages,namely,water release,evolve and combustion of volatile matter,fixed carbon combustion and mineral decomposition.With the increase of mixing ratio of microalgae,the comprehensive combustion characteristic index of mixed fuel increased.Kinetic compensation effect was existed for the activation energy and frequency factor of mixed fuel.Secondly,the vertical tube furnace was designed and built,the mixing ratio of microalgae,the combustion temperature and the excess air coefficient on polluted gas emission characteristics of oily sludge,microalgae and their mixtures were studied with combustion method.The combustion experiments indicated that with the increase of mixing ratio of microalgae,NO_X emission concentration decreased firstly and then increased,while SO₂ emission concentration decreased when oily sludge was burned.With the increase of combustion temperature,NO_X emission concentration decreased,and SO₂ emission concentration increased first and then decreased.With the increase of excess air coefficient,NO_X and SO₂ emission concentration increased.Finally,the effects of the combustion temperature,the mixing ratio of microalgae and the excess air coefficient on the migration and transformation of heavy metals during the incineration of oily sludge were studied with the method of combining experiment with software simulation.The results indicated that when the incineration temperature riseed from800°C to 1100°C,the release rate of heavy metals Cr,Pb,Cu,Zn and Ni increased gradually,and reached the maximum at 1100°C,and the gaseous chloride content of Cr,Pb and Cu increased,while the morphological changes of Zn and Ni were not obvious.When the mixing ratio of microalgae increased from 0%to 100%,the release rates of heavy metals Cr,Pb,Cu,Zn and Ni increased gradually,and the gaseous chlorides content of Pb,Cu,Zn,Ni increased and the gaseous hydroxides content of Cr increased.When the excess air coefficient increased from 1 to 1.4,the release of heavy metals Cr,Pb,Cu,Zn and Ni first decreased and then tended to be stable,and the gaseous hydroxides content of Cr and the gaseous chlorides content of Pb,Cu increased,while the morphological changes of Zn and Ni were not obvious.