Study On Removing Solid Particles In Slurry Via Centrifugal-Electrostatic Combination Technology

Fluidized catalytic cracking(FCC)units can produce up to 15 million tons of slurry each year in China.Owing to FCC slurry generally has the characteristics of high viscosity,low carbon residues content,and high solid content,it is often used as fuel oil or mixed with the residuum as coking feedstock,therefore,it has a low economic value.However,FCC slurry contains many aromatic molecules,and if the solid particles are removed,they can be used to produce high value-added products such as carbon black,needle coke and carbon fiber.Therefore,it is important to study on the removal of solid particles in FCC slurry.The solid particles in the FCC slurries are small in size,have a bulk density close to that of the slurry,and are both dispersed phase and stabilizer in the slurry.Therefore,it is difficult to remove the solid particles.This study compares several common methods of removing solid particles.In order to reduce the solid content in the FCC slurry,increase the efficiency of removing solid particles and decrease the energy at the same time,the method of preprocessing the slurry and then removing the solids by centrifugal-electrostatic combination process(CEEP)was put forward.When the Multifunctional composite additives(MCA)were used to pretreat the slurry and the solids in the slurry were then removed by CEEP,the best operating conditions were determined: MCA-B was the best additive,and the addition proportion was 150wt%;the centrifugal force was 3819×g,and centrifugation time was 10min;electrostatic voltage was 14 kV,and electrostatic temperature was 70°C,with electrostatic treatment time of 30 min..When the solid particles in the FCC slurry were removed by using flocculant pretreatment before treatment with CEEP,the processing conditions were also optimized.The optimized conditions were as follows: Toluene was used as the diluent,and the ratio was 100wt%;PAM was used as the flocculant,with an adding ratio of 0.03wt%;centrifugal force was 3819×g,and centrifugal time was 15min;upper oil proportion was 75wt%;electrostatic voltage was 14 kV,and electrostatic temperature was 100°C,with static treatment time of 30 min.The solid-removal efficiency of the two treatment methods reaches more than 96%,and the solid content of the FCC slurry can be reduced to less than 30 ppm to meet the solid content requirements as a raw material for producing high-value-added products.The solid particles in the slurry before and after treatment were respectively enriched by the gravimetric method,and then the solid particles were analyzed by FT-IR,SEM and EDS.The analysis found that about 90wt% of the solid particles solid particles solid particles are catalysts and about 10wt% are coke particles.The addition of additives or diluents can effectively reduce the density viscosity of the slurry.Both pretreatment methods can effectively reduce the content of the polar components,and promote the accumulation of solid particles in the slurry in the electrostatic treatment process,effectively increase the efficiency of removing solid particles.By comparing the energy consumption of the two treatment methods in the electrostatic treatment,it was found that the energy consumption was lower with the aid of additives pretreatment and the centrifugal-electrostatic combination process.This process is most suitable when reagent dosage is not considered.