Study On Chemical Demulsification Pretreatment Of Waste Cutting Fluid And Incineration Behavior Of Separated Oily Sludge

As a representative hazardous waste from metalworking process,the waste cutting fluid has become a challenging existence in environmental protection industry because of its high concentration of organic matter and strong stability.In order to protect the environment and human health,the waste cutting fluid must be disposed under the requirements of environmental laws.However,the high cost of wastewater treatment put companies under pressure,and demulsification was considered to be a very effective method.The concentration of organic matter,oil and various additives in the waste cutting fluid could be reduced rapidly,and oily sludge would be generated inevitably.The reduction,harmlessness and recycling disposal of oily sludge was of great significance to the sustainable development of environmental protection industry.In this paper,the waste cutting fluid produced by a metal parts processing company was taken as the research object,the reduction treatment was carried out by coagulation demulsification,and the disposal of oily sludge after demulsification was studied too.Firstly,in order to separate the water and oil from the waste cutting fluid,the water quality of the upper liquid and the output of the separation oily sludge were taken as the main evaluation indexes,the influence of metal cation on demulsification was investigated,and the demulsification conditions were optimized,which provided theoretical reference for the selection of demulsification agents and process parameters.The results showed:the dosage of metal ions was 0.08 mol/L with Al³⁺:Fe³⁺ratio was1.5:1,the reaction p H was 6,the reaction time was 18 min and the temperature was 50℃.Based on this,the COD_Cr removal,the SV₃₀ ratio and the transmittance and COD_Cr/SV₃₀ratio of the waste cutting fluid were 80.21%,40.00%,95.20%and 128.33 mg/m L,respectively.Meanwhile,the operating cost of the demulsification treatment process for the waste cutting fluid occupied nearly 10.00%of the current output treatment.Therefore,this demulsification method could realize the reduction treatment of waste cutting fluid and shown good economy.Secondly,the incineration process and behavior of oily sludge was simulated and investigated respectively.TG-DTG/DSC was used to study the burning process of oily sludge.Meanwhile,SEM-EDS-Mapping,IR,XPS and XRD were used to characterize the oily sludge at 105℃,300℃and 800℃to reveal its possible burning mechanism.The results showed that the total weight loss rate of oily sludge was 58.22%in the temperature range of 105℃to 800℃.With the increase of temperature,the surface of oily sludge gradually coarsened,the concentration of C,N,Cl and some metal elements decreased greatly,only Fe element was enriched.IR test showed that the functional groups in oily sludge after burning reduced violently,and some functional groups disappeared completely.In addition,XRD and XPS tests showed that KFe O₂ and KAl Cl₂O crystals were formed on the surface of oily sludge at high temperature,and Al₂O₃ and Fe₂O₃ were formed at 800℃.Combined with TG-DTG/DSC curves,the oily sludge incineration process could be divided into three stages:physical dehydration,combustion of oil and low boiling point organic matter,and combustion of residual fixed carbon.Finally,the incineration kinetic model of oily sludge was established to describe the incineration behavior.Among them,E_αand ln（A）of the weightlessness phase were calculated based on FWO method.The thermodynamic parameters of oily sludge incineration process were analyzed,and the incineration process was determined to contain multi-step reaction according to the variation trend of E_α.The activation energy distribution function f（E_α）was obtained by model-free fitting method in accordance with Lorentz distribution.The incineration kinetic model of oily sludge was obtained,which provided a theoretical reference for the optimization of oily sludge incineration process.