Simulation Of Fluidized Bed Microbial Fuel Cell

With the development of social economy and population expansion,the quantity of urban domestic sewage and industrial wastewater are increasing.The Sewage contains a lot of biodegradable organic matter,which caused a lot of water pollution.Microbial fuel cells（MFCs）are devices that use microorganisms as biocatalysts to degrade organic matter in wastewater while directly obtaining electrical energy.It has become one of the hot spots in renewable energy research in this century.The fluidized bed MFC,as a novel anode reactor configuration for microbial fuel cells has a larger reaction area,high mass transfer rate and sufficient hydraulic retention time,and has a better efficiency of wastewater treatment and electricity production.However,because of its complexity,it has great significance to construct a reasonable and accurate mathematical model to study the operation mechanism of the fluidized bed MFC and the effects of various parameters on the battery production characteristics.In this paper,the models of mass transfer,electrochemical reaction and biochemical reaction in a fluidized bed MFC were established combined with anaerobic consumption model according to the presence or absence of electron mediator in the anode chamber.The model equations were solved by MATLAB software.The effects of different factors on battery power generation and wastewater treatment were explored.Firstly,the mathematical models for the fluidized-bed MFC with electron mediator were established.The effects of initial glucose concentration,external resistance,internal battery resistance,fluidization velocity,and methylene blue concentration on the operation of the battery were simulated and analyzed.The simulation results show that increasing the initial glucose concentration is beneficial to enhance the MFC’s output voltage and maximum power density,however,further increase of glucose concentration will hinder the improvement of the electrical performance of the battery and the optimum initial glucose concentration is 0.5kgCOD·m^-3;increasing of external resistance will reduce the battery current,but it has little effect on the COD degradation of wastewater;the internal resistance of the battery has a significant impact on the electrical performance of the battery and the maximum power density is increased by 328.18%when the internal resistance of the battery ranged from 500Ωto 100Ω;increasing the flow rate of waste water is beneficial to improving the battery electricity production performance,but when the flow rate was further increased,the battery’s power generation performance decreases,and the optimal operating flow rate is 2.5 mm·s^-1;the biofilm has adsorbability to methylene blue,so increasing the initial methylene blue concentration reduces the performance of the battery,and the simulation results are consistent well with the experimental results.Secondly,the mathematical models for non-mediated fluidized bed MFC were established.The effects of initial glucose concentration,external resistance,internal resistance,and the flow rate of wastewater on the battery power generation and the wastewater treatment were simulated and analyzed.The simulation results indicate that increasing the initial glucose concentration is beneficial to improving the operating voltage and prolonging the stable discharge duration of the battery;increasing the external resistance value is conducive to improving the power of the battery at a small external resistance during operation,when the external resistance increases,the current of the battery decreases at a external resistance in excess of 400Ω,and the external resistance has little effect on the degradation of wastewater COD;the battery internal resistance size has a great influence on the battery performance,and the ability of electricity production of the battery is significantly improved when the internal resistance of the battery was reduced;increasing the flow rate of the wastewater is beneficial to increase the battery performance under the fixed bed conditions,and when the flow rate was further increased,the mass transfer resistance in the anode chamber decreases under the fluidized bed condition,and the performance of the battery is further increased.Both simulated data and experimental data indicate that the fixed bed MFC and the fluidized bed MFC have better wastewater treatment performance.In this paper,mathematical models with the presence or absence of electron mediator in fluidized-bed MFC were established.The coupling mechanism of mass transfer,reaction and electrogenesis in fluidized bed MFC was investigated and the mechanism of different factors on the battery performance were also studied.At the same time,it can be used as a reference for other more complex cases.