| Crop stalk and other bio-resource is aboundant in China.There is an impotant way to utlize those bio-resource efficiently,tranfoming them into bio-gas and other organic byproducts under the technologu of naerobic fermentation.VFAs play a key role among fermentation process,which is produced in the process of bio-gas production.This article take corn as experimental materials,have an exploration of VFAs characters and the influence of its accumulation on bio-gas production,in medium fermentation temperature under the circumastance of high solid rate.Besides,adding extra regulator to provent acid restriction,for the purpose of bio-gas production smoothly.This article is expected to provide some reference for futher bio-gas production,especially in improving corn stalk fermentation with high solid rate,and adjusting fermentation technology possibly.Main conclusions are as follows:(1)The daily bio-gas production of four corn stalk groups(each group dealt with different TS respectively,15%、20%、25%、30%)increased at first and then declined.Accordingly,the cumulative production of bio-gas in 35 days reaches to 12070mL、15150mL、12970mL、7850mL.The group dealt with 20%TS produce bio-gas cumulatively most,and 30%produce least.In addition,the TS removal rate of four groups are 47.72%、55.03%、50.32%、46.12%,and bio-gas production ration are 0.235m3/kg、0.298m3/kg、0.221m3/kg、0.189 m3/kg.pH flows a bit large in the group dealt with 30%TS,for the reason of acid rectriction.(2)Acid produced in anaerobic fermentation are mainly acetic acid and propionic acid.Among them,acetic acid plays a leading role,and it achieves highest at no.14 day.The cumulative production of VFA reaches most at 7200mg/L、7460mg/L、8210 mg/L and 8300 mg/L、,acetic acid is 2900mg/L、3900 mg/L、3200 mg/L and 2400 mg/L,propionic acid is 2120 mg/L、1630 mg/L、2010 mg/L and 2470 mg/L,butyric acid are 550 mg/L、630 mg/L、550mg/L and 200 mg/L.Acetic acid is the main contents of volatile acid,and it transformed for methane rapidly.So,volatile acid declined gradually and keeps stable.(3)In the condition of 15%TS,influences on cron fermentation are explored,which comes from different kinds of VFAs,acetic acid、propionic acid and butyric acid.It shows that acetic acid concentration in anaerobic fermentation system can not more than 6g/L.Bio-gas can produce smoothly under the concentration of 2g/L and 4 g/L.Respectively the peak of daily bio-gas production is 630630mL and 660mL,and the cumulative production is 15700mL and 17180mL.Upon starting,pH changes in normal rage.Propionic acid concentration can not more than 4g/L.Daily bio-gas achieves best at 650mL and cumulative production achieves best at 14060mL when the concentration of propionic acid at 2g/L,and pH changes between 6.5 and 7.5.Butyric acid concentration can not more than 8g/L.Bio-gas can produce continually at the concentration of 2g/L、4 g/L and 6g/L.Besides,when butyric acid at 6g/L,the cumulative production achieves at 12980mL、13290mL、16260mL.pH at a low level at first,increase gradually upon starting,and maintains between 6.5 and 7.5.(4)In the experiment of adding extra different concentrations of Fe2+,results show that those groups treated with appropriate Fe2+ was significantly better than those untreated.The group which was dealt with Fe2+ at 2.0mg/L produce bio-gas daily most at 790mL,cumulative production about 17760mL in a fermentation circle.The removal of TS reaches to 55.03,VS being 53.26%.Acetic acid occupied a leading role among total VFAs.The more acetic acid is,the more bio-gas produced.Propionic acid functions on the contrary.(5)In the experiment of adding extra bio-carbon and different concentrations of Fe2+,VFAs cumulated most at 550mg/L、5780mg/L、6030mg/L、6680mg/L、5010 mg/L、4620mg/L,accordingly,acetic acid being 4240mg/L、2880mg/L、2830mg/L,propionic acid being 1640mg/L、1820mg/L、1930mg/L、2030mg/L、1540mg/L、1620mg/L.Bycomparision,we can come to conclusion that the cooperation of bio-carbon and Fe2+ promotes both acid and bio-gas production in naerobic fermentation. |
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