| Oil sludge is a kind of hazardous waste generated in the process of petroleum extraction,storage,transportation,and refining.Oil sludge has the characteristics of large quantity,difficult to dispose,high toxicity,and high recovery value.The problem of oil sludge has become a prominent problem in the field of petroleum applications,and governance is imperative.The current treatment technologies of oil sludge are relatively traditional,such as solidification/stabilization,biodegradation,incineration,pyrolysis,cannot take into account harmless and resourceful.The exploration of treatment technology is imminent.Smoldering is a slow,low-temperature,flame-free combustion,which can maximize the combination of the recycling of pyrolysis and the harmlessness of incineration.At the same time,smoldering combustion has been proven to be an effective mechanism for processing high-water waste,which has the possibility of oil sludge treatment.Therefore,this paper carried out the feasibility exploration and evaluation of method of smoldering combustion to treat oil sludge.This article first introduces the source,basic physical parameters and pretreatment methods(pre-drying and blending)of oil sludge samples;And designs and builds a smoldering test bench of oil sludge,and introduces the design concept and function of its each part in detail;The detection equipment involved in the analysis of products(trace moisture analyzer,automatic calorimeter,X-ray fluorescence spectrometer,gas chromatograph,refinery gas analyzer,and ultraviolet absorption flue gas monitoring system)fully describe the function,basic principle and method used.Through a large number of orthogonal experiments,the effects of initial moisture content,material ratio(mass ratio of hollow ceramic column to oil sludge),air flow,and filling thickness on smoldering characteristics(ignition temperature,ignition time,peak temperature of smoldering propagation and propagation time)were studied.The specific research contents and conclusions include:(1)After pre-drying and blending,oil sludge can achieve self-sustaining smoldering in the experimental device.It is feasible to treat oil sludge with smoldering combustion;(2)The initial moisture content is the key factor that affects the success of smoldering combustion.The reduction of initial moisture content is beneficial to increase the generation and propagation rate of smoldering combustion;(3)The mixing of hollow ceramic column and oil sludge can improve the permeability of oil sludge,which is conducive to smoldering.However,too much hollow ceramic column will reduce the stability of smoldering propagation.Too little hollow ceramic column will increase the time of smoldering propagation;(4)Proper air supply is an important condition to ensure the smoldering of oil sludge.Too low air flow is not conducive to improving the smoldering propagation speed;however,too large air flow will make the smoldering to be converted into flaming combustion or the smoldering will be extinguished because the heat is quickly taken away,and more energy needs to be consumed;(5)Properly increasing the thickness of oil sludge can improve the propagation rate of smoldering combustion,but the peak temperature is from the upper limit.The smoldering products of oil sludge were collected and analyzed,and it was found that:(1)The solid residue in the reactor only accounted for 14.6%of the total mass of oil sludge before smoldering combustion.In terms of waste treatment,the reduction of oil sludge was achieved.By condensing the off-gas,36.1%of oil in the oil sludge and a large amount of water were recovered,and the resource of oil sludge was achieved;(2)The oil sludge before smoldering combustion was black-brown,viscous,with irritating odor.The solid residue was brick red solid particles without irritating odor.It can be known from XRF detection that metal elements(such as Fe,Ca,Al,Mn,Ti)and non-metallic elements(such as Si)mostly contained in the solid residue are present in the form of oxides with extremely low hazards.Through gas chromatography detection,the petroleum hydrocarbon(C10-C40),a typical pollutant in oil sludge,was completely eliminated.The above analysis shows that method of smoldering combustion can realize harmless of oi sludge;(3)The oil recovered from the smoldering off-gas is detected by gas chromatography and calorific value analysis.Its composition is similar to "black diesel" and has a higher calorific value than kerosene and diesel.After a certain treatment,it has the potential for resource utilization;(4)After it was found that the concentration of SO2 and NOx in the smoldering off-gas is low by ultraviolet absorption flue gas monitoring system and refinery gas analysis,but some H2,CO,and a large amount of H2S are generated,and the off-gas needs to be purified accordingly. |
