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The Start-up And Operation Of CSTR Reactor Based On Starch Syrup

Posted on:2017-01-30Degree:MasterType:Thesis
Country:ChinaCandidate:Z R ZhouFull Text:PDF
GTID:2271330491951962Subject:Environmental Science
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Hydrogen is one of the most ideal clean energies. In consideration of the cost and the environment-friendly level, bio-hydrogen doesn’t cost much and have abundant raw materials, people can use all kinds of materials such as solid-wastes, domestic sewage, animal wastes and food wastes to do fermentation-hydrogen-production work, thus it can reduce the cost and purify water as well as gain hydrogen, achieving the aim of protecting environment and making the wastes both innocent and reusing.This study compared the start-up and operation of SS-CSTR(CSTR system based on starch syrup) and BS-CSTR(CSTR system based on brown sugar), discussde the practicability of producing hydrogen with starch syrup, and learned the effect of the changing of engineering control parameters pH on the SS-CSTR.To start up the two reactors, I took a method that to reduce the OLR of each system from 18 kg/(m3-d) to 9 kg/(m3·d), the seed sludge volumes were respectively 18.11 gVSS/L and 18.04 gVSS/L, temperature was 35±1℃, HRT=6 h. Both SS-CSTR and BS-CSTR systems finished starting up with in about 16 days. In the final phase of start-up, the pH of SS-CSTR and BS-CSTR was steady at 4.37 and 4.28 respectively, biogas yield was 3.00 L/d and 4.52 L/d respectively, of which the hydrogen percent was 74.60% and 75.28% respectively, the ethanol and acetic acid yield in SS-CSTR liquid phase end fermentation was 536.678 mg/L and 396.978 mg/L respectively, and took a 75.54% of the liquid phase end fermentation. While the BS-CSTR liquid phase end fermentation contained 550.395 mg/L ethanol and 412.357 mg/L acetic acid, which took a 76.49% of all. Both two systems formed typical ethanol fermentation.Comparing the two systems’condition of start-up, we could draw the following conclusions:SS-CSTR had an worse effect, and SS-CSTR was worse at adopting the change of the environment comparing with BS-CSTR. The reason was that SS-CSTR contained less easily biodegradated sugar than the BS-CSTR.By enhancing the OLR, the stability of operation in SS-CSTR and BS-CSTR was tested. Enhancing the OLR from 9 kg COD/(m3·d) to 24 kgCOD/(m3·d), both SS-CSTR and BS-CSTR achieved the stable operational status, COD removal rate enhanced from 8.30% and 18.00% respectively to 22.00% and 20.00% respectively, biogas yield enhanced from 3.00 L/d and 4.52 L/d respectively to 25.00 L/d and 29.00 L/d respectively, percent of hydrogen achieved about 65.4% and 64.6% respectively. The main products of the ethanol fermentation ethanol and acetic acid achieved about 84% and 82% respectively, of which ethanol were about 59% and 60%, proving that both two systems keeped the features of ethanol fermentation.In the operational period, comparing the standard deviations of pH, ORP, COD removol rates and hydrogen production yields of SS-CSTR and BS-CSTR, the BS-CSTRs’ were all less than the SS-CSTRs’. Thus we could draw the conclusion:both SS-CSTR and BS-CSTR could keep stable, but the SS-CSTR’s stability was worse than the BS-CSTR.On the condition of this study, the hydrogen yields of starch syrup was 1.41 mmol/(L-h), and the hydrogen yields of brown sugar was 1.62 mmol/(L-h). It could be accepted that there is possibility of producing hydrogen with starch syrup.The change of engineering control parameters pH changed the dominant microflora inside the SS-CSTR system, causing a change of the type of fermentation. The initial 10 days, pH was between 5.2-5.5, the main liquid fermentation was butyrate and acetic acid, ethanol content was low, presenting butyrate fermentation. The succedent 10 days, pH was between 3.8-4.2, liquid fermentation gradually turned to ethanol and acetic acid, presenting a typical ethanol fermentation.It will be seen from that when the microbial habitat are in a certain condition of stable status, the ecological factors of a special species exactly satisfied all the limiting factors in the environment, this species could become the dominant microflora. Therefore, in the reality apply, to urge the microflora we need to become the dominant one, we should create advantageous conditions, ensuring the environment fitting the growing and supersession of the special microflora.
Keywords/Search Tags:CSTR, anaerobic fermentation, biology hydrogen production, ethanol fermentation, starch syrup
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