Staged Condensation Of Oil Shale Pyrolysis Volatiles For Dedust And Fractionation Of Shale Oil

Oil shale is an unconventional solid fossil fuel with abundant resources in China.Shale oil obtained from pyrolysis of oil shale is similar to crude oil,which has become a significant supplementary oil resource.However,high contents of dust and heavy components in shale oil obtained from solid heat carrier technology impair its quality and are disadvantageous for its high-value utilization.To solve above problems,it is proposed to fractionate the oil into maj or fractions online by staged condensation,one of which contains the maximum content of dust and heavy components and the other contains the maximum light components with minimum dust.By the above method,the shale oil can be separated into several products preliminary in the condensation of pyrolysis vapor.On the basis of proposed technology,the impact of condensation temperature on the removal of dust and separation of components is studied by experiments and numerical simulation.The main findings are summarized as follows:1.A model was built to simulate the evolution of particle size distribution(PSD)at high number concentration by heterogeneous condensation.By the model,the effects of particle number concentration,initial diameter and initial vapor concentration were studied on the particle size distribution.It was found that a low particle number concentration or a high vapor concentration were beneficial to shift the PSD toward larger particles with a narrower distribution.The fluctuation of initial particle size(1-3 ?m)had weak influence on the final particle size,which was around 8 ?m.This feature was beneficial to the separation of dust from pyrolysis vapor at high temperature.Vapor depletion had greater effects than heat release on the final PSD at high particle number concentrations,which prevented the further increase of particle size.Based on the results,the condensation of vapor was preliminarily verified for the removal of dust.2.The staged condensation with three stages of condensers was applied in the pyrolysis of oil shale via a lab-scale fluidized bed.The temperature of the second stage and the third stage were 16 ? and-2 ?respectively.The effect of cooling temperature of the first stage(66-247 ?)on the distribution and characteristics of liquids was investigated.The results showed that the yield of shale oil and dust(defined as toluene insoluble matter)in the first stage increased with the decreasing temperature,which proved that the condensation of oil vapor had a positive influence on the removal of dust.The optimum temperature in this study was 158 ?.On the basis of above condensation temperatures,the yield,contents of heavy components and dust in the oil of the first stage were 18.03%,75.66%and 6.99%respectively.The mixture of the oil in the latter stages accounted for 81.97%of the total oil,whose content of heavy components and dust were 30.38%and 1.83%respectively.The results preliminarily showed that it was feasible to apply staged condensation to the removal of dust and separation of components.3.When the temperature of the first stage was higher than 158 ?,the particles were dispersed uniformly,while the small aggregates were formed at 158 ?.As the temperature decreased,the aggregates became larger.The temperature gap defined as the difference vapor temperature between the inlet and the outlet of the condenser influenced the way of vapor condensation.When the gap was less than 242 ?,vapor condensation tended to occur on the particle's surface called as heterogeneous condensation at low supersaturation,resulting in the agglomeration by the collision between particles.When the gap was larger than 242 ?,great amount of droplets could be formed by homogeneous condensation at high supersaturation and may collide with particles to induce agglomerates.4.A CFD model with the condensation of multicomponent was built to investigate the distribution of components in the condenser.The results showed that the distribution of temperature in the condenser had great influence on the condensation of each components.For the tested pyrolysis vapor,the dew point temperatures of the atmospheric gas oil and gasoline were 157.3 ?and 79.9 ?,which were in accordance with the experimental data and could be used to guide for the determination of the cooling temperature in the technology of staged condensation.5.The technologies of dust collector with three-stage condensers and dust collector with rectification column were simulated respectively.When the yields of the obtained products were close to each other,the purities of products obtained from the technology of dust collector with rectification column were higher than the other.With the optimum parameters,the pyrolysis vapor was condensed into crude heavy oil,crude atmospheric gas oil and crude gasoline,whose purities were 93.26%,93.43%and 69.19%respectively.