Nitrogen oxides （NOx） emission during the regeneration ofcoked fluid catalytic cracking （FCC） catalysts is an en- vironmental issue. In order to identify the correlations between nitrogen species in coke and diffe...Nitrogen oxides （NOx） emission during the regeneration ofcoked fluid catalytic cracking （FCC） catalysts is an en- vironmental issue. In order to identify the correlations between nitrogen species in coke and different nitrogen- containing products in tail gas, three coked catalysts with multilayer structural coke molecules were prepared in a fixed bed with model compounds （o-xylene and quinoline） at first. A series of characterization methods were used to analyze coke, including elemental analysis, FT-IR, XPS, and TG-MS. XPS characterization indicates all coked catalysts present two types of nitrogen species and the type with a higher binding energy is related with the inner part nitrogen atoms interacting with acid sites. Due to the stronger adsorption ability on acid sites for basic nitrogen compounds, the multilayer structural coke has unbalanced distribution of carbon and ni- trogen atoms between the inner part and the outer edge, which strongly affects gas product formation. At the early stage of regeneration, oxidation starts from the outer edge and the product NO can be reduced to N2 in high CO concentration. At the later stage, the inner part rich in nitrogen begins to be exposed to 02. At this period, the formation of CO decreases due to lack of carbon atoms, which is not beneficial to the reduction of NO. There- fore, nitrogen species in the inner part of multilayer structural coke contributes more to NOx formation. Based on the multilayer structure model of coke molecule and its oxidation behavior, a possible strategy to control NOx emission was discussed merely from concept.展开更多
In coking process, the production quality, equipment life, energy consumption, and process safety are all influenced by the pressure in gas collector pipe of coke oven, which is frequently influenced by disturbances.T...In coking process, the production quality, equipment life, energy consumption, and process safety are all influenced by the pressure in gas collector pipe of coke oven, which is frequently influenced by disturbances.The main control objectives for the gas collector pressure system are keeping the pressures in collector pipes at appropriate operating point. In this paper, model predictive control(MPC) strategy is introduced to control the collector pressure system due to its ability to handle constraint and good control performance. Based on a method proposed to simplify the system model, an extended state space model predictive control is designed,which combines the feedforward strategy to eliminate the disturbance. The simulation results in a system with two coke ovens show the feasibility and effectiveness of the control scheme.展开更多
A heterogeneous model is developed for the regeneration of the Cr2O3/Al2O3 catalyst for the propane dehydrogenation process by considering the internal mass transfer and external mass/heat transfer during the coke com...A heterogeneous model is developed for the regeneration of the Cr2O3/Al2O3 catalyst for the propane dehydrogenation process by considering the internal mass transfer and external mass/heat transfer during the coke combustion.Simulation shows that under practical operating conditions,multi-steady states exist for the catalyst pellets and the catalyst temperature is sensitive to gas temperature.However,at increased mass flow rate or lowered oxygen concentration,multi-steady states will not appear.Under the strong influences of film diffusion,the coke in the packed bed reactor will first be exhausted at the inlet,while if the film diffusion resistance is decreased,the position of first coke exhaustion moves toward the outlet of the reactor.展开更多
基金Supported by the National Natural Science Foundation of China(21476263)the National Natural Science Foundation for Young Scholars(21206198)
文摘Nitrogen oxides （NOx） emission during the regeneration ofcoked fluid catalytic cracking （FCC） catalysts is an en- vironmental issue. In order to identify the correlations between nitrogen species in coke and different nitrogen- containing products in tail gas, three coked catalysts with multilayer structural coke molecules were prepared in a fixed bed with model compounds （o-xylene and quinoline） at first. A series of characterization methods were used to analyze coke, including elemental analysis, FT-IR, XPS, and TG-MS. XPS characterization indicates all coked catalysts present two types of nitrogen species and the type with a higher binding energy is related with the inner part nitrogen atoms interacting with acid sites. Due to the stronger adsorption ability on acid sites for basic nitrogen compounds, the multilayer structural coke has unbalanced distribution of carbon and ni- trogen atoms between the inner part and the outer edge, which strongly affects gas product formation. At the early stage of regeneration, oxidation starts from the outer edge and the product NO can be reduced to N2 in high CO concentration. At the later stage, the inner part rich in nitrogen begins to be exposed to 02. At this period, the formation of CO decreases due to lack of carbon atoms, which is not beneficial to the reduction of NO. There- fore, nitrogen species in the inner part of multilayer structural coke contributes more to NOx formation. Based on the multilayer structure model of coke molecule and its oxidation behavior, a possible strategy to control NOx emission was discussed merely from concept.
基金Supported by the State Key Laboratory of Synthetical Automation for Process Industriesthe National Natural Science Foundation of China(61374110,61333009,61104078,61221003)the Minhang Technology Project of Shanghai(2012MH211)
文摘In coking process, the production quality, equipment life, energy consumption, and process safety are all influenced by the pressure in gas collector pipe of coke oven, which is frequently influenced by disturbances.The main control objectives for the gas collector pressure system are keeping the pressures in collector pipes at appropriate operating point. In this paper, model predictive control(MPC) strategy is introduced to control the collector pressure system due to its ability to handle constraint and good control performance. Based on a method proposed to simplify the system model, an extended state space model predictive control is designed,which combines the feedforward strategy to eliminate the disturbance. The simulation results in a system with two coke ovens show the feasibility and effectiveness of the control scheme.
基金Supported by the National Natural Science Foundation of China（20736011） the Ministry of Education of China（IRT0721）
文摘A heterogeneous model is developed for the regeneration of the Cr2O3/Al2O3 catalyst for the propane dehydrogenation process by considering the internal mass transfer and external mass/heat transfer during the coke combustion.Simulation shows that under practical operating conditions,multi-steady states exist for the catalyst pellets and the catalyst temperature is sensitive to gas temperature.However,at increased mass flow rate or lowered oxygen concentration,multi-steady states will not appear.Under the strong influences of film diffusion,the coke in the packed bed reactor will first be exhausted at the inlet,while if the film diffusion resistance is decreased,the position of first coke exhaustion moves toward the outlet of the reactor.
