Study On A New Continuous Regeneration Evaluation Method Of FCC Spent Catalyst

Catalyst regeneration is an essential process in a fluid catalytic cracking（FCC）process of petroleum refineries.How to obtain accurate catalyst regeneration characteristics close to the operation of industrial FCC regenerator is an important part of the successful development of new catalysts or additives.At present,the laboratory evaluation of catalyst regeneration characteristics is generally carried out through small fixed fluidized bed or pilot plant,but both methods have their limitations.Especially,the reaction and hydrodynamics properties in the evaluation units are greatly different from those in industrial FCC regenerators.Therefore,the obtained evaluation results have only limited value in the applications of actual industrial units.In order to solve the above problems,a laboratory-scale continuous catalyst regeneration evaluation method based on continuous quantitative feeding and overflow discharge was proposed in this study.Due to the limited time,only the cold model validation experiment and the design hot model evaluation unit were finished in this study.The main purpose of the cold model experiment is to verify the feasibility of the measures such as continuous feeding and discharging of catalyst and whether the catalyst inventory in the regenerator of the small scale evaluation device can be kept stably.In addition,some hot experiments on pollutant conversion characteristics in FCC regeneration process were also carried out to further familiarize the traditional evaluation methods and catalytic conversion characteristics of FCC additives,thus laying a foundation for the development of the evaluation methods of FCC additives based on the new continuous catalyst regeneration evaluation device in the future.The thesis first carried out the design of the steady continuous catalyst regeneration device based on revamping an old fixed fluidized bed FCC reaction evaluation unit.Main process parameters and equipment sizes were obtained based on mass and heat balances as well as the revamping object.Then,cold model experiments were carried out in a same-dimension small fluidized bed to verify the feasibility of the determined reactor structure and the other auxiliary components,the influence of changing operating conditions and the exploration of the optimal structure arrangement.The bed fluidization quality is evaluated by the measured pressure profiles and pressure fluctuations.By measuring the carbon content of particles entering and leaving the bed at different time,a new solids residence time distribution（RTD）measurement method was proposed.The RTD characteristics of the evaluation reactor were also studied.Subsequently,temperature-programmed pyrolysis,temperature-programmed oxidation and rapid burning experiments were carried out on a conventional small-scale fixed fluidized bed evaluation device.By monitoring the emissions of CO,CO₂,SO₂,NO,HCN and other flue gas pollutants,the effects of temperature and oxygen concentration on the conversion characteristics of flue gas pollutants in the regeneration process of FCC treatment agent were studied.The results of cold model experiment show that,within the operating range of superficial gas velocity of 0.06～0.18m/s and solids circulation rate of 0.6～1.8g/s,the small fluidized bed evaluation regenerator has an inner diameter of 60mm for its lower dense bed and an overflow pipe of ID 8mm.Despite its small scale,the quantitative continuous steady feeding and discharging of catalyst particles can be maintained in a very long period which is sufficient to achieve a steady continuous evaluation of FCC regeneration process.When the superficial gas velocity increases,the bed pressure fluctuations increase and the catalyst inventory decreases slightly.The gas distributor with small opening area and large pressure drop has smaller pressure fluctuations in bed,and the annular gas distributor with large ring diameter can realized the best fluidization quality.Superficial gas velocity has small influences on the residence time distribution of particles,while the circulation rate has more pronounced effect.The results of flue gas pollutant conversion experiments showed that SO₂is generated during pyrolysis of FCC catalyst at 500～600^oC,but no N pollutant is detected.In the temperature-programmed oxidation and rapid burning experiments,CO,CO₂,SO₂and NO increased with increasing temperature and O₂concentration,while HCN increases first and then decreased with increasing O₂concentration.In the regeneration experiment at 550～750^oC,N compounds such as NO and HCN begin to appear and reach their peaks,whose time are later than those of CO,CO₂and SO₂.Finally,based on the validation results of cold model experiment and the small hot experiments on FCC regeneration pollutants,the process design and structural design of the hot new continuous catalyst regeneration evaluation device have been finished and authorized to a partner for manufacturing.