The Research Of Continuous Pilot-scale Preparation Of Biodiesel From Waste Acid Oil Enhanced By Multi-frequency Ultrasonic

With the depletion of fossil energy day by day and serious environmental pollutionbrought by the burning fossil energy production, All over the world urgently needs to developdiversified energy system, biodiesel that regarded as a substitute for petroleum diesel is arenewable clean energy. The synthesis of biodiesel from waste acid oil with high efficiencyand low energy consumption, by mean of multi-frequency ultrasonic was investigated.The multi-frequency ultrasonic radiation was introduced in biodiesel production facility,in this paper, and the ultrasonic power meter was used to explore the multi-frequencyultrasonic energy distribution of the overflow groove. Inside the flat geometry ultrasonicoverflow tank, the ultrasonic intensity was the result of comprehensive action of mutualsuperposition and interference of sound waves near sound field area. Whether in the z axisdirection of ultrasonic overflow groove or in radial direction on the x axis, the greater thepower/frequency, the larger the ultrasonic intensity is. In any spatial location of fourultrasonic overflow tank, the ultrasonic intensity distribution was approximatelyhomogeneous, which ensured biodiesel product quality and stability.Due to acid value(AV) of raw material as high as33.07mg KOH/g, H2SO4-catalyzedesterification reaction was applied to reduce the acid value of acid oil. The optimal operatingconditions were as follows: mechanical mixing speed of200rpm, methanol to oil molar ratioof9:1, catalyst dosage of2.0wt%, reaction temperature of45℃, reaction time of300min,respectively. Meanwhile, under these conditions, esterification efficiency was94.47%, acidvalue was reduced to1.83mg KOH/g, which meet requirements of homogeneous catalytictransesterification.The material that that has been pre-treated continuously flowed into multi-frequencyultrasonic overflow tank, transesterification that was continuous replaced1time wasoptimized by using orthogonal experiment. The results showed that the primary andsecondary order of the influences of the various factors: flow rate> ultrasonic power>methanol to oil molar ratio> reaction temperature> amount of catalyst, the optimizationprocess was A2B2C1D1E1, methyl ester conversion rate of biodiesel reached97.53%. Whenmethanol to oil molar ratio of6:1, flow rate of25L/h, ultrasonic power of200W, comparingthe1.0times,1.5times,2.0times continuous displacement volume, we found that theconversion rate of methyl esters didn’t not appear significant fluctuations, which indicatedthat the system achieved the dynamic balance and the product quality was stable. With optimized conditions,50L waste acid oil produced about48L biodiesel that satisfied withstandards GB19147-2009, and the overall electricity and time consumption were only5.42kWh and8.667h, respectively.The cost of continuously producing biodiesel was accounted, which found that the costof every ton biodiesel production was7173.4yuan under the optimal operating condition andraw material cost was73%. If commercial biodiesel price was7500yuan/t，426.6yuan profitcould be obtained.