Effect Of Mixing And Illumination On Photo-fermentation Hydrogen Production From Corn Cob

The photo-fermentation biohydrogen production system using straw as substrate has the characteristics of high solid concentration and easy deposition,which hinders the interphase transfer behavior in the hydrogen production multiphase reaction flow system.In order to enhance the contact between hydrogen production microorganisms and substrates and the mass transfer capacity of the system,corn cob was used as substrate for photo-fermentation minxing biohydrogen production by microbiome HAU-M1 in this paper.The cumulative hydrogen production was taken as the index,the effects of light intensity,substrate concentration and mixing intensity on biohydrogen production were investigated and the synergistic strengthening mechanism was optimized,the results show that:(1)In photo-fermentation biological hydrogen production,the system uniformity was was improved by adding mixing so that enhanced the hydrogen production performance.The growth and hydrogen metabolism of photosynthetic bacteria could be promoted by proper light intensity.When the light intensity was 4000,5000 and 6000 lx respectively,after adding the mixing,the cumulative hydrogen production increased by 33.2%,61.5% and 530.9%,respectively.The delay periods of hydrogen production were shortened from 66.74,64.03,61.18 h to 17.13,20.34,20.59 h,respectively.It shows that the addition of mixing can take advantage of higher light intensity,effectively improve hydrogen production performance and shorten the hydrogen production delay period.Too low or too high a substrate concentration can lead to a decrease in cumulative hydrogen production.When the substrate concentration was 27.78,41.67 and55.56 g/L,after adding the mixing,the cumulative hydrogen production at the substrate concentration of41.67 and 55.56 g/L increased by 16.7% and 56.1%,respectively,while the cumulative hydrogen production at the substrate concentration of 27.78 g/L decreased by 26.9%.The delay periods of hydrogen production were shortened from 20.21,14.13 and 8.41 h to 11.96,13.96 and 8.07 h,respectively.It shows that the hydrogen production system with the addition of mixing requires a higher substrate concentration,and a lower substrate concentration will limit the hydrogen production performance of the system.The mixing intensity had significant effect on cumulative hydrogen production.When the mixing intensity increased from 50 rpm to 150 rpm,the cumulative hydrogen production increased from 221.33 m L to395.69 m L,reaching the maximum value.The cumulative hydrogen production began to decrease as the intensity of the mixing continues to increase.It can be seen that proper oscillation intensity can significantly improve the hydrogen production capacity of the system.(2)Based on the results of single factor optimization,BBD response surface method was used to further optimize the optimal hydrogen production conditions: mixing intensity of 153.33 rpm,light intensity of 6155.56 lx,substrate concentration of 57.71 g/L,and the maximum cumulative hydrogen production was 490.41 m L.According to the optimal conditions for hydrogen production,the cumulative hydrogen production is 468.34 m L.Compared with the predicted value,the relative error is only 4.5%,indicating that the predicted value has high reliability and reference value.Model p-value < 0.0001,proving that the difference of this model is extremely significant.On the linear term,mixing intensity(X1),light intensity(X2)and substrate concentration(X3)were the most significant factors affecting the photo-fermentation biological hydrogen production(P<0.0001).According to the three-dimensional response surface diagram and two-dimensional contour diagram,the interaction between mixing intensity and substrate concentration has the greatest influence on photo-fermentation biological hydrogen production,followed by the interaction between mixing intensity and light intensity,and the interaction between light intensity and substrate concentration has the least influence.(3)According to the delay period of hydrogen production,the dynamic light supply mode is designed as follows: the light intensity within 0-20.59 h is 4000 lx;20.59-84 h light intensity is 6000 lx;The light intensity is 4000 lx in 84-120 h.The potential of hydrogen production varies significantly with different substrate concentration under dynamic light supply.When the substrate concentration is the same,the cumulative hydrogen production under constant light supply is slightly higher than that under dynamic light supply.The light supply mode was changed,when the substrate concentration was 41.67,55.56 and 69.44g/L,the cumulative hydrogen production decreased only 13.2%,1.7% and 6.8%,respectively.According to the cumulative hydrogen production,the substrate concentration of 55.56 g/L and the oscillation intensity of 150 rpm were the most suitable for dynamic light supply hydrogen production.Combined with economic benefits,Cumulative hydrogen production decreased by only 1.7%,however,the energy consumption of the whole hydrogen production process can be reduced by 9948.52 J per square meter.Considering the cumulative hydrogen production and economic benefits,hydrogen production by dynamic light supply strategy could bring higher income.In conclusion,the hydrogen production potential of light fermentation was significantly improved with the addition of mixing.The optimal illumination intensity was 6000 lx,the optimal substrate concentration was 55.56 g/L,and the optimal oscillation intensity was 150 RPM for hydrogen production.BBD response surface method was used to further optimize the hydrogen production conditions,and the optimal conditions were as follows: the mixing intensity was 153.33 RPM,the illumination intensity was 6155.56 lx,the substrate concentration was 57.71 g/L,and the maximum cumulative hydrogen production was490.41 m L.Although the potential of hydrogen production by dynamic light supply decreased by 1.7%,the energy consumption of 9948.52 J per square meter in the whole process of hydrogen production could be reduced.Considering the cumulative hydrogen production and economic benefits,hydrogen production by dynamic light supply can bring higher income.