No abstract

The fluidization technology has a wide range of applications. In chemical synthesis, fluidized bed is used to enhance heat and mass transfer between the reacting species. More application of this technology can also be seen in pneumatic transport and circulation of solid particles. The different applications require different flow regimes. This study investigates the influence of initial bed height on the fluidized bed regime transition using the Computational Particle Fluid Dynamics (CPFD) software, Barracuda VR. The simulations are performed for a specific powder with a narrow particle size distribution. The results from the simulations are compared with the experimental data and correlations in the literature. The minimum fluidization velocity drop to a stable value and the bubbling velocity remains constant with an increase in the bed height. The gas velocity at onset of slugging decreases while that of turbulent increases to a stable value as the bed height increases.

renewable energy sources have significant potential for limiting climate change and reducing greenhouse gas emissions due to the increased global energy demand. Fluidized bed gasification of biomass is a substantial contribution to meeting the global energy demand in a sustainable way. however, ashrelated problems are the biggest challenge in fluidized bed gasification of biomass. bed agglomeration is a result of interaction between the bed material and alkali metals present in the biomass ash. The agglomerates interfere with the fluidization process and might result in total de-fluidization of the bed. The study focuses on ash challenges related to the fluidization behavior in gasification of biomass. a model is developed and verified against results from previous performed experiments in a cold flow model of a bubbling fluidized bed. The commercial computational particle fluid dynamics (CPFD) software barracuda Virtual reactor is used for the computational study. The simulations show that the CPFD model can predict the fluidization process of an agglomerated fluidized bed gasifier.

Management of spent mushroom substrate (SMS) is causing a global environmental concern due to tremendous increase in mushroom production globally. Therefore, in this research, the performance of a two-stage anaerobic co-digestion (TS-AD) of spent mushroom substrate and chicken manure was evaluated in terms of methane and biogas production and process stability with respect to single stage anaerobic digestion (SS-AD). Activation of anaerobic sludge using aeration or heat treatment in the first stage at mesophilic temperature followed by thermophilic co-digestion with chicken manure in the second stage was investigated. TS-AD exhibited better performance and enhanced methane generation over SS-AD. The optimal temperatures were determined as 35°C and 50°C for the first and the second stage of TS-AD, respectively. C/N ratio of 10 was the most suitable for biogas and methane production. TS-AD with C/N ratio of 10 and mesophilic digestion of SMS and sludge for 3 days at 35°C followed by co-digestion of the first stage effluent with chicken manure at 50°C was the optimized state producing 1359 mL of biogas of which 614.42 mL was methane, showing an increment by 59.44% in methane production as compared to SS-AD. TS-AD might be promising approach for utilization of SMS as feed stocks for biogas and methane production.

Method of identifying an operating regiMe in a bubbling fluidized bed gasification reactor rajan jaiswal, nora c. i. s. furuvik, rajan k. thapa & britt M. e. Moldestad department of natural science and Maritime science, university of southeastern norway, porsgrunn, norway abstract this work presents a new method for identifying the bubbling regime of a fluidized bed gasification reactor. the method has been developed using experimental measurements and a computational model. pressure drops are measured in experiments, and pressure drop as well as solid volume fraction fluctuations are calculated by implementing the model. experiments are carried out with sand and limestone particles of mean diameter 346 m µ and 672 m µ , respectively. a computational particle fluid dynamics (cpfd) model has been developed for the reactor and implemented using a commercial cpfd software barracuda vr. the model is validated against experimental measurements. the validated model is used to analyse the fluctuation of pressure drop and solid volume fraction as a function of superficial air velocity. the change in standard deviation of pressure drop and solid volume fraction fluctuation is used to predict the transition from one regime to another. the method can be used in the design and operation of a bubbling fluidized bed gasification reactor. the results show that the minimum fluidization velocity for sand and limestone are 0.135 m/s and 0.36 m/s, respectively and are independent of the particle aspect ratio. both types of particle beds make the transition into bubbling regime as soon as they get fluidized. the bed aspect ratios have almost no effect on the onset of bubbling fluidization regime. the slugging velocity decreases with increasing aspect ratio for both types of particles. the operating range of the bubbling fluidized bed for sand particle is 0.2-0.4 m/s and 0.5-0.8 m/s for the limestone particles.