由于医疗废物对人体和环境的危害性,即使是少量医疗废物也需要及时快速无害化处理,这对那些偏远而分散设置的众多中小型医疗机构十分重要。但是,目前还缺乏有效的小型医疗废物清洁高效处理成套技术,难以实现对其快速无害化和减量化处理...由于医疗废物对人体和环境的危害性,即使是少量医疗废物也需要及时快速无害化处理,这对那些偏远而分散设置的众多中小型医疗机构十分重要。但是,目前还缺乏有效的小型医疗废物清洁高效处理成套技术,难以实现对其快速无害化和减量化处理的需求。本工作针对现有小型医疗废物焚烧处理面临的燃烧与烟气净化方面的问题,基于解耦燃烧原理设计了一种适宜分散性医疗废物高度集成清洁处理的焚烧炉和系统,并进行实验测试。结果表明,解耦焚烧炉可充分实现医疗废物的高效燃烧、抑制氮氧化物(NOx)和二噁英(PCDD/Fs)的生成;两级湿法小型烟气净化装置可使烟气急速降温以避免二噁英的生成,同时可高效脱除酸性物质和粉尘(PM)。典型混配医疗废物经系统处理后,烟气污染物NO_(x),SO_(2),PM,CO和PCDD/Fs等的排放浓度按O_(2)浓度11vol%的折算值分别低于123,1.8,38,53 mg/m^(3)和0.31 ng I-TEQ/m^(3)。新开发的小型医疗废物焚烧处理系统采用燃烧与净化一体化集成设计,结构紧凑,净化效率高,可满足分散医疗机构的日常医疗废物的就地快速洁净处理需要。展开更多
Burning coal briquettes or biomass pellets in household decoupling stoves is of significance to the reduction of residential pollutant emissions such as NO and CO. In order to make full use of the superiority of decou...Burning coal briquettes or biomass pellets in household decoupling stoves is of significance to the reduction of residential pollutant emissions such as NO and CO. In order to make full use of the superiority of decoupling combustion technology, the household stoves should be specially designed and optimized to adapt to fuel types and combustion characteristics. Using numerical simulation and experimental validation, this study quantitatively clarified that the reducibility of devolatilization char plays an important role in the suppression of NO emission in the decoupling combustion of coal, while the reducibility of pyrolysis gases has a dominant effect on the reduction of NO in the decoupling combustion of biomass. An optimal parameter combination of throat height and grate angle was obtained for the simultaneous suppression of NO and CO emissions in the household decoupling stove burning coal briquettes. Two types of decoupling stoves were developed to enable the clean combustion of biomass pellets. The A-type biomass stove with a multi-pass smoke tunnel shows a better comprehensive NO and CO reduction effectiveness than the B-type biomass stove consisting of a two-stage grate structure and an S-shaped pyrolysis chamber. The optimal structural parameters provided references for the design and manufacture of commercial decoupling coal and biomass stoves.展开更多
The novel circulating turbulent fluidized bed(CTFB)technology has found wide applications in various processes owing to its high solid circulation rate and low backmixing.However,up to now,only a limited number of CFD...The novel circulating turbulent fluidized bed(CTFB)technology has found wide applications in various processes owing to its high solid circulation rate and low backmixing.However,up to now,only a limited number of CFD simulation studies on this type of reactor can be found in the literature.Moreover,there is currently no guidance available for selecting appropriate subgrid drag models that take into account the impact of mesoscale structures.In this work,a two-fluid model incorporating seven different drag models include homogeneous drag models,filtered models,and EMMS-based drag models was employed to conduct a systematic investigation into the hydrodynamics of CTFB reactors.It was found that the flow structure in the CTFB reactor differs significantly from conventional fast fluidized beds,exhibiting relatively weaker radial heterogeneity and attenuated near-wall particle downward flows.Comparative analysis demonstrates that the homogeneous drag models fail to predict reasonable hydrodynamics consistent with the experiments.In contrast,the mesoscale drag models show satisfactory performance in reproducing solid concentration profiles,while additional marker variables should be considered in the drag models to enhance the prediction accuracy of particle velocity.The EMMS-based drag model with an advanced conservation equation for cluster size achieves better accuracy in predicting both solid concentration and velocity distributions.Nevertheless,future model development should address wall boundary effects to enhance mesoscale drag applicability in CTFB simulations.展开更多
Coal remains a cornerstone of China's energy landscape,significantly contributing to primary energy production and consumption.This study investigates the combustion characteristics of coal particles using a discr...Coal remains a cornerstone of China's energy landscape,significantly contributing to primary energy production and consumption.This study investigates the combustion characteristics of coal particles using a discrete modeling approach to simulate the combustion behavior of single particles.The research reveals that larger particle sizes increase heat and mass transfer resistance,prolonging combustion duration,while higher ambient temperatures enhance convective heat transfer,accelerating combustion reactions.Additionally,the spatial distribution of inert cohesive beads significantly affects gas diffusion,with certain arrangements hindering gas release.The model is validated against current literature,demonstrating its capability to predict carbon conversion rates and combustion dynamics.These findings provide valuable insights into coal combustion mechanisms,offering a foundation for optimizing combustion processes and improving energy efficiency while addressing environmental concerns.展开更多
With the increasingly stringent national environmental protection policies,the ultra-low emission transformation of industrial coal-fired grate boilers and the highly efficient utilization of biomass resources or wast...With the increasingly stringent national environmental protection policies,the ultra-low emission transformation of industrial coal-fired grate boilers and the highly efficient utilization of biomass resources or wastes are becoming increasingly urgent in China.This study first proposes a novel and simple configuration for industrial grate boilers to integrate the decoupling combustion and flue gas recirculation or co-firing technologies,so as to reduce pollutant emission but improve thermal efficiency.Burning coal briquettes in the novel grate boiler,the original NO_(x) emissions can be remarkably decreased to as low as 56 mg· m^(-3),corresponding to the reduction efficiency of 82.8% in comparison with the average value in traditional coal-fired grate boilers.Co-firing coal briquettes with straw pellets in the novel grate boiler,the strongest synergistic effect of NO_(x) reduction is observed at the blending mass fraction of 50%,in which the NOxemissions can be further mitigated by at most 16.0% on top of the already reduced amount by decoupling combustion to reach less than about 165 mg· m^(-3).The novel grate boiler allows co-firing Chinese medicine residue with high water content at the blending mass fraction of up to 30% on the premise of low NO_(x) and CO emissions.All experimental results in this study demonstrated the obvious superiorities of the novel grate boiler in reducing NO_(x) and CO emissions and mitigating both slagging tendency and slag carbon content,which can be attributed to either the cumulative effects of decoupling combustion with flue gas recirculation or the synergistic effects of cofiring coal-biomass blends.The newly-developed travelling-grate decoupling combustion technology can be expected to provide an economical and convenient measure for the ultra-low NO_(x) emission transformation of industrial coal-fired grate boilers as well as the clean and highly efficient consumption of biomass wastes with high water content or difficulty to burn in China.展开更多
Dual-loop circulating fluidized bed(CFB)reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability.However,the design of such reactors is...Dual-loop circulating fluidized bed(CFB)reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability.However,the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms,meaning it has been heavily based on empiricism and stepwise experiments.Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them.This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale(EMMS)principle.A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors,to achieve the mass conservation and pressure balance in each circulation loop.Based on the modularization strategy,corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor.This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.展开更多
Cocurrent gas-solid downer reactors have many applications in industry because they possess the tech- nological advantages of a lower pressure drop, shorter residence time, and less solid backmixing when compared with...Cocurrent gas-solid downer reactors have many applications in industry because they possess the tech- nological advantages of a lower pressure drop, shorter residence time, and less solid backmixing when compared with traditional circulating fluidized bed risers. By introducing the concept of particle clusters explicitly, a one-dimensional model with consideration of the interphase interactions between the fluid and particles at both microscale and mesoscale is formulated for concurrent downward gas-solid flow according to energy-minimization multi-scale （EMMS） theory. A unified stability condition is proposed for the differently developed sections of gas-solid flow according to the principle of the compromise in competition between dominant mechanisms. By optimizing the number density of particle clusters with respect to the stability condition, the formulated model can be numerically solved without introducing cluster-specific empirical correlations. The EMMS-based model predicts well the axial hydrodynamics of cocurrent gas-solid downers and is expected to have a wider range of applications than the existing cluster-based models.展开更多
文摘由于医疗废物对人体和环境的危害性,即使是少量医疗废物也需要及时快速无害化处理,这对那些偏远而分散设置的众多中小型医疗机构十分重要。但是,目前还缺乏有效的小型医疗废物清洁高效处理成套技术,难以实现对其快速无害化和减量化处理的需求。本工作针对现有小型医疗废物焚烧处理面临的燃烧与烟气净化方面的问题,基于解耦燃烧原理设计了一种适宜分散性医疗废物高度集成清洁处理的焚烧炉和系统,并进行实验测试。结果表明,解耦焚烧炉可充分实现医疗废物的高效燃烧、抑制氮氧化物(NOx)和二噁英(PCDD/Fs)的生成;两级湿法小型烟气净化装置可使烟气急速降温以避免二噁英的生成,同时可高效脱除酸性物质和粉尘(PM)。典型混配医疗废物经系统处理后,烟气污染物NO_(x),SO_(2),PM,CO和PCDD/Fs等的排放浓度按O_(2)浓度11vol%的折算值分别低于123,1.8,38,53 mg/m^(3)和0.31 ng I-TEQ/m^(3)。新开发的小型医疗废物焚烧处理系统采用燃烧与净化一体化集成设计,结构紧凑,净化效率高,可满足分散医疗机构的日常医疗废物的就地快速洁净处理需要。
基金financial supports from the “Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of Chinese Academy of Sciences (XDA21040400)。
文摘Burning coal briquettes or biomass pellets in household decoupling stoves is of significance to the reduction of residential pollutant emissions such as NO and CO. In order to make full use of the superiority of decoupling combustion technology, the household stoves should be specially designed and optimized to adapt to fuel types and combustion characteristics. Using numerical simulation and experimental validation, this study quantitatively clarified that the reducibility of devolatilization char plays an important role in the suppression of NO emission in the decoupling combustion of coal, while the reducibility of pyrolysis gases has a dominant effect on the reduction of NO in the decoupling combustion of biomass. An optimal parameter combination of throat height and grate angle was obtained for the simultaneous suppression of NO and CO emissions in the household decoupling stove burning coal briquettes. Two types of decoupling stoves were developed to enable the clean combustion of biomass pellets. The A-type biomass stove with a multi-pass smoke tunnel shows a better comprehensive NO and CO reduction effectiveness than the B-type biomass stove consisting of a two-stage grate structure and an S-shaped pyrolysis chamber. The optimal structural parameters provided references for the design and manufacture of commercial decoupling coal and biomass stoves.
基金supported by the“Low-carbon transformation technologies and demonstrations in chemical engineering and metallurgical processing”,Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDA0390501)the National Natural Science Foundation of China(grant Nos.22378396,22008240)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(grant No.2022046)the Fund of State Key Laboratory of Mesoscience and Engineering(grant No.Meso-23-A02).
文摘The novel circulating turbulent fluidized bed(CTFB)technology has found wide applications in various processes owing to its high solid circulation rate and low backmixing.However,up to now,only a limited number of CFD simulation studies on this type of reactor can be found in the literature.Moreover,there is currently no guidance available for selecting appropriate subgrid drag models that take into account the impact of mesoscale structures.In this work,a two-fluid model incorporating seven different drag models include homogeneous drag models,filtered models,and EMMS-based drag models was employed to conduct a systematic investigation into the hydrodynamics of CTFB reactors.It was found that the flow structure in the CTFB reactor differs significantly from conventional fast fluidized beds,exhibiting relatively weaker radial heterogeneity and attenuated near-wall particle downward flows.Comparative analysis demonstrates that the homogeneous drag models fail to predict reasonable hydrodynamics consistent with the experiments.In contrast,the mesoscale drag models show satisfactory performance in reproducing solid concentration profiles,while additional marker variables should be considered in the drag models to enhance the prediction accuracy of particle velocity.The EMMS-based drag model with an advanced conservation equation for cluster size achieves better accuracy in predicting both solid concentration and velocity distributions.Nevertheless,future model development should address wall boundary effects to enhance mesoscale drag applicability in CTFB simulations.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA29020401)the National Natural Science Foundation of China(Grant Nos.22373104,22373105 and T2394501)+1 种基金Additionally,it receives support from IPE Project for Frontier Basic Research(Grant No.QYJC-2023-04)the Open Research Fund of the State Key Laboratory of Mesoscience and Engineering(Grants Nos.MESO-23-E01 and MESO-23-A01).
文摘Coal remains a cornerstone of China's energy landscape,significantly contributing to primary energy production and consumption.This study investigates the combustion characteristics of coal particles using a discrete modeling approach to simulate the combustion behavior of single particles.The research reveals that larger particle sizes increase heat and mass transfer resistance,prolonging combustion duration,while higher ambient temperatures enhance convective heat transfer,accelerating combustion reactions.Additionally,the spatial distribution of inert cohesive beads significantly affects gas diffusion,with certain arrangements hindering gas release.The model is validated against current literature,demonstrating its capability to predict carbon conversion rates and combustion dynamics.These findings provide valuable insights into coal combustion mechanisms,offering a foundation for optimizing combustion processes and improving energy efficiency while addressing environmental concerns.
基金supported by the Strategic Priority Research Programs of Chinese Academy of Sciences (XDA29020401)the Fund of State Key Laboratory of Mesoscience and Engineering (Meso-23-A02)。
文摘With the increasingly stringent national environmental protection policies,the ultra-low emission transformation of industrial coal-fired grate boilers and the highly efficient utilization of biomass resources or wastes are becoming increasingly urgent in China.This study first proposes a novel and simple configuration for industrial grate boilers to integrate the decoupling combustion and flue gas recirculation or co-firing technologies,so as to reduce pollutant emission but improve thermal efficiency.Burning coal briquettes in the novel grate boiler,the original NO_(x) emissions can be remarkably decreased to as low as 56 mg· m^(-3),corresponding to the reduction efficiency of 82.8% in comparison with the average value in traditional coal-fired grate boilers.Co-firing coal briquettes with straw pellets in the novel grate boiler,the strongest synergistic effect of NO_(x) reduction is observed at the blending mass fraction of 50%,in which the NOxemissions can be further mitigated by at most 16.0% on top of the already reduced amount by decoupling combustion to reach less than about 165 mg· m^(-3).The novel grate boiler allows co-firing Chinese medicine residue with high water content at the blending mass fraction of up to 30% on the premise of low NO_(x) and CO emissions.All experimental results in this study demonstrated the obvious superiorities of the novel grate boiler in reducing NO_(x) and CO emissions and mitigating both slagging tendency and slag carbon content,which can be attributed to either the cumulative effects of decoupling combustion with flue gas recirculation or the synergistic effects of cofiring coal-biomass blends.The newly-developed travelling-grate decoupling combustion technology can be expected to provide an economical and convenient measure for the ultra-low NO_(x) emission transformation of industrial coal-fired grate boilers as well as the clean and highly efficient consumption of biomass wastes with high water content or difficulty to burn in China.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA07080400)the National Natural Science Foundation of China(Grant No.U1710251)for their financial support.
文摘Dual-loop circulating fluidized bed(CFB)reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability.However,the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms,meaning it has been heavily based on empiricism and stepwise experiments.Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them.This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale(EMMS)principle.A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors,to achieve the mass conservation and pressure balance in each circulation loop.Based on the modularization strategy,corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor.This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.
基金We appreciate financial support from the Strategic Prior- ity Research Program of the Chinese Academy of Sciences （No. XDA07080400） and the Natural Science Foundation of China （Nos. 21376244 and 91334107）.
文摘Cocurrent gas-solid downer reactors have many applications in industry because they possess the tech- nological advantages of a lower pressure drop, shorter residence time, and less solid backmixing when compared with traditional circulating fluidized bed risers. By introducing the concept of particle clusters explicitly, a one-dimensional model with consideration of the interphase interactions between the fluid and particles at both microscale and mesoscale is formulated for concurrent downward gas-solid flow according to energy-minimization multi-scale （EMMS） theory. A unified stability condition is proposed for the differently developed sections of gas-solid flow according to the principle of the compromise in competition between dominant mechanisms. By optimizing the number density of particle clusters with respect to the stability condition, the formulated model can be numerically solved without introducing cluster-specific empirical correlations. The EMMS-based model predicts well the axial hydrodynamics of cocurrent gas-solid downers and is expected to have a wider range of applications than the existing cluster-based models.
