Dissipation Rate Analysis And Optimization In Photosynthetic Hydrogen Production Process

Photosynthetic hydrogen production is a clean and green way of energy utilization.In the process of hydrogen production,the mass transfer and structural characteristics of the reactor will affect the hydrogen production performance.In order to improve the hydrogen production performance of the photosynthetic biological reactor,it is necessary to study the transfer and transformation process in the photosynthetic biological reactor,so as to reduce the unnecessary energy dissipation in the process of hydrogen production.In this paper,a non-equilibrium thermodynamic(dissipation rate model)was established for the mass transfer and chemical reaction process of hydrogen production by photosynthetic bacteria,and the model were determined.The effects of substrate concentration,temperature and initial pH on hydrogen production characteristics,dissipation rate and phenomenological coefficient of photosynthetic bacteria were studied.Taking the minimum energy dissipation as the optimization objective,the structure size of the reactor was optimized.The main results were as follows:(1)Based on the theory of mass transfer and the kinetic equation of reaction,a model of dissipative rate in the process of photosynthetic hydrogen production was established by using the method of non-equilibrium thermodynamics,combining the logistic model and the modified Gompertz model.The non-equilibrium thermodynamic model is applied to the complex hydrogen production process with life activities,which provides a new method to evaluate the hydrogen production performance of the reactor.(2)The variation laws of mass transfer dissipation rate,chemical reaction dissipation rate and total dissipation rate in the process of hydrogen production from glucose and acetic acid were obtained respectively.Compared with the existing experimental results,the dissipation rate model was verified.The dissipative rate of different substrates increased first and then decreased.Under the conditions of 30℃,pH 7.0 and 20%inoculation amount,the maximum mass transfer dissipation rate,chemical reaction dissipation rate and total dissipation rate of 10 g/L glucose were 5.9741 J/h,7.7803 J/h and 14.1585 J/h respectively at 72 h.Under condition of 30℃ and 20%inoculation amount,the maximum mass transfer dissipation rate,chemical reaction dissipation rate and total dissipation rate of 40 mmol/L acetic acid appeared at 66 h,which were 6.5358 J/h,9.1247 J/h and 15.6605 J/h,respectively.(3)The effects of substrate concentration,temperature and initial pH on the dissipation rate and phenomenological coefficient were obtained,and the reactor parameters were optimized.The substrate concentration was set as 15 g/L,20 g/L and 25 g/L,the pH was 7.0,the inoculation amount was 30%,and the temperature was 30℃.The total dissipation rate was the lowest,the phenomenological coefficient of mass transfer was the lowest,and the maximum dissipation rate was 7.7288 J/h at 20 g/L.When the temperature was set at 25℃,30℃ and 35℃,the substrate concentration was 20 g/L,the pH was 7.0 and the inoculation amount was 30%,the lowest dissipation rate was found at 30℃.The higher the phenomenological coefficient of chemical reaction,the higher the maximum dissipation rate was 6.0596 J/h.When the initial pH is used as the variable,the pH values are set to 6.5,7.0 and 7.5.The maximum dissipation rate is 11.2271 J/h when the initial pH is 7.0.At high pH value,the phenomenological coefficient of mass transfer is high,but the chemical phenomenological coefficient is completely opposite.When the mass transfer area is 0.3938×10-3 m2 and the height of reaction liquid is 0.1 m,the dissipation rate is the smallest.Small mass transfer area can reduce the energy dissipation in the process of mass transfer.