Study On Biohydrogen Production System Of Sweet Sorghum Press Juice CSTR

With the rapid economic development,the energy dispute has become the focus of the global political economy.The exploration,development,and use of new energy are increasingly drawing attention from governments around the world.In response to rising fossil fuel prices and slower environmental pressures,hydrogen is recovering globally as a clean,economical,and scalable energy source.However,the rapid and large-scale preparation and safe use of hydrogen is the biggest obstacle to the generalization of hydrogen energy.There are five sources of hydrogen generation:water electrolysis,thermochemistry,photoelectrochemistry,plasma chemistry,and biohydrogen production.These fore methods have their own advantages and disadvantages.The hydrogen production method has a high cost and cannot be the main means of hydrogen production.Therefore,the biohydrogen production method has gradually entered the field of vision and attracted many researchers on its utilization and development.Biohydrogen is divided into two types,one is photosynthesis and hydrogen production;the other is hydrogen production by fermentation.Hydrogen produced by fermentation is mainly produced by the use of facultative anaerobic bacteria for anaerobic fermentation.In addition to the hydrogen production from hydrogen production by fermentation,there is also the rapid propagation of bacterial species,easy transport and preservation,and low overall cost,so hydrogen production from fermentation has a better prospect.Therefore,in this experiment,according to the principle of anaerobic fermentation biohydrogen production,using the CSTR reactor,sweet sorghum straw pressing juice was used as the substrate,and brown sugar was used as the control group to investigate whether the sweet sorghum straw pressing juice had superior hydrogen production performance.The initial parameters of the experiment were set as:hydraulic retention time of 6 h,temperature of(35±1)?,and system OLR of 16 kg/(m3·d).The experimental results show that the higher OLR can rapidly perform population iteration-The 5d microflora of the system using sweet sorghum press juice as a substrate was basically screened.On the 7th day,OLR was reduced to 10 kg/(m3·d)to promote the recovery of ethanol-producing bacteria,and the 13-day start was successful.Gas product yields tend to be stable.Ethanol and acetic acid accounted for 77%of the liquid phase end product,typical of ethanol fermentation.Gas production is stable at 3.4L/d,hydrogen production is stable at 1.OL/d,and hydrogen is about 29%;while brown sugar system basically ends at 6d population iteration,OLR is reduced to 10kg/(m3·d)at the 9th day.,Started successfully on the 16th day,its fermentation type was also ethanol fermentation,gas production was 2.7L/d,hydrogen production was 0.7L/d,and hydrogen was 26%.After comparison,it was found that the sweet sorghum press juice started more quickly.The reason for the analysis may be that the specific gravity of monosaccharide contained in the fresh juice of sweet sorghum is larger than that of brown sugar,and microorganisms are more easily absorbed and utilized.The experiment started the reactor with a higher concentration of the influent substrate.This practice not only allows the bacteria to quickly generate a large number of volatile organic acids,but also screens out acid-tolerant ethanol-producing bacteria,and reduces the OLR in the middle of start-up.Repeated changes in environmental conditions can maximally stimulate the environmental adaptability of microorganisms,increase their buffer capacity,and prepare for the subsequent increase in OLR and determination of their maximum hydrogen production capacity.After the start of the reactor,the influent substrate was increased by 2000mg/L in increments of frequency every 20 days.The organic load was divided into four stages from low to high to explore the "sweetened wastewater"(ie,The maximum concentration of sweet sorghum juice is used for processing,and whether the sweet sorghum pressing juice has better hydrogen production performance.The experiment found that when the influent substrate concentration was 6000mg/L,the main flora was ethanol-producing bacteria.At this time,the highest COD removal rate was 32%,and the maximum hydrogen production was 5.75L/d.By the end of the experiment,when the influent concentration was adjusted to 8000 mg/L,the pH of the system began to increase,indicating that the volatile organic acids were greatly reduced,and the COD removal rate,hydrogen production,ethanol production,and biomass all gradually decreased.This suggests that excessively high concentrations of substrates may inhibit the growth and reproduction of organisms.The brown sugar also has a similar change.When the substrate concentration is 6000mg/L,the COD removal rate is the highest,reaching 27%,and the hydrogen production rate is up to 5.02L/d;when the influent substrate concentration reaches 8000mg/L,COD removal rate,hydrogen production also began to decrease.This shows that simple sugars have commonalities.It is speculated that if other simple sugars are used as substrates,the optimal influent COD concentration should also be around 6000 mg/L.Compared with sweet sorghum and brown sugar systems,it can be found that sweet sorghum juice has slightly better hydrogen production than brown sugar.After repeated changes to the living environment and microbial screening of the bacterial flora,the species in the system is relatively simple and the structure is relatively simple.Therefore,the stability of recovery force is good.Even if the environment suddenly changes,it can quickly return to the previous state.However,even if the ethanol-producing strains with good recovery power are unable to return to their peak state with high concentration of influent COD,it can be seen that too high substrate concentration is not conducive to the biochemical metabolism of the bacteria.In summary,the system after successful startup has a certain ability to adapt to the impact caused by the increase of substrate concentration,but when the concentration of the substrate exceeds a certain limit,it may cause the system to collapse.