Study On The Clean Catalytic Pyrolysis Characteristics Of Oil Sludge

Oil sludge is one of solid wastes that produced in the oil industry.It contains oil,water,heavy metals and solid particles,which are toxic,mutagenic and carcinogenic.Due to the existence of high concentration of petroleum hydrocarbons(PHCs),oil sludge has been recognized as a kind of hazardous wastes that threatens environment and human health.However,the recovery of oil sludge is gaining ever-increasing interests,as an alternative method of waste management,to produce energy and fuels to mitigate the demand of fossil fuels.Pyrolysis has been considered as an attractive technology for the treatment and disposal of oil sludge.However,the pyrolysis of oil sludge could generate solid fine particles,such as sands and fly ashes.These particles will be carried from the reactor by gas and cause fouling and blockage in downstream equipments and connections,which could reduce the quality of the pyrolysis oil and gas.Based on these considerations,therefore,a study on the clean catalytic pyrolysis of oil sludge was carried out,by incorporating a ceramic membrane inside the reactor for the pyrolysis of oil sludge,aiming to significantly enhance the removal of fine particles from the pyrolysis vapors.The detailed conclusions are drawn as follows:(1)The clean pyrolysis of oil sludge was carried out on the fixed bed reactor.The effect of the reaction temperature on the product distribution and properties of oil sludge pyrolysis with ceramic membrane was investigated.It was found that when the reaction temperature was 500?,the production rate of the pyrolysis oil was the highest of 14.30%,and the oil recovery rate is 78.83%.Pyrolysis oil was the light brown,clear and transparent liquid.When the temperature was 700?,pyrolysis oil changed into dark brown liquid,and the production rate and recovery rate of oil were decreased.The yield of pyrolysis gas was around 5.23?39.24 L/(kg·h)when the temperature varied from 400 to 700 0C.With the increasing temperature,the H2 content was decrease from 89.67%to 28.14%,while the content of C1?C3 increased gradually.The LHV of the pyrolysis gas,pyrolysis oil and pyrolysis residue were 15.92?45.78 MJ/Nm3?41.69?38.09 MJ/kg and 1.02?0.73 MJ/kg,respectively.Therefore,the optimal reaction temperature of sludge pyrolysis with ceramic membrane is 500?.(2)The clean pyrolysis of oil sludge was carried out on the spiral reactor.The effect of the ceramic membrane on the particulate matter removal in pyrolysis volatiles and the pyrolysis products was investigated.It was found that the ceramic membrane played an important role in particulate removal.When the oil sludge was reacted with the ceramic membrane,the PM contents of the pyrolysis gas and oil were 0.17 mg/L and 234.62 mg/L,respectively.The obtained pyrolysis oil was clear,transparent and brown.It can be seen clearly that a mass of solid particles with inhomogeneous particle sizes were scattered in the pyrolysis oil.On the contrary,the pyrolysis oil generated from the reactor without the ceramic membrane was turbid,non-transparent and ashen.There were no obvious solid particles found in the high magnification microscope image.The PM contents of the pyrolysis gas and oil were 2.74 mg/L and 3708.88 mg/L,respectively.(3)The clean catalytic pyrolysis of oil sludge was carried out on the spiral reactor to study the effect of the Ni/ceramic membrane on the products of oil sludge pyrolysis.It was found that the Ni catalyst-loaded ceramic membrane could improve the yield of the pyrolysis gas,and reduce the recovery rate of pyrolysis oil.The yield of the pyrolysis gas produced from the reaction with Ni/ceramic membrane was 15.74 L/(kg·h),while the recovery rate of pyrolysis oil was 48.21%.On the contrary,the yield of the pyrolysis gas produced from the reaction with ceramic membrane was 8.96 L/(kg·h),while the recovery rate of pyrolysis oil was 62.63%.In addition,a long-time catalytic pyrolysis experiment was carried out.With the feeding speed of 4.17 g/min,reaction temperature of 500? and WHSV of 0.58 h-1,the Ni/ceramic membrane could be used continuously for 420 min.In the experiment,the differential pressure of the inside and outside of ceramic membrane increased gradually.