Anaerobic Study On The Treatment Of Chinese Herb Residues Of Hubei Wushi Pharmacological Limited Company

Energy shortage and environmental pollution were two main survival pressuresaround the world, and the application of anaerobic fermentation to Chinese herbresidues and other solid organic waste treatment can eliminate pollutants as well asproduce energy, which could play an important role in energy-saving and emission-reduction. Anaerobic reactor was the key carrier of anaerobic technology, theresearch of high-rate anaerobic reactor could have forcefully pushed the furtherdevelopment of anaerobic technology.Large numbers of rehmannia glutinosa dregs were produced during theproduction of pills of six drugs with rehmannia, these herb residues were rich inorganic substances such as protein, starch, cellulose, anthrone, lignin, alkaloid and themicroelement etc. The utilization of these dregs for resource reuse by anaerobicdigestion was considered, because the conversion from organic solid waste to cleanenergy was realized by anaerobic digestion. So, it would achieve a win-win situationbetween environment and energy. In the laboratory, anaerobic characteristics ofrehmannia glutinosa dregs were studied. In order to realize the continuous steadyoperation and process controlling of the anaerobic reaction, the semi-solid anaerobicreactor was designed according to the anaerobic characteristics. Which could providebasis and experience for anaerobic reactor designing and industrialized operation ofbiogas production from the anaerobic digestion on Chinese herb residues to replacecoal fuel. In the anaerobic experiments, the substrates of rehmannia glutinosa dregswere collected from Hubei Wushi Pharmacological Limited Company in Anlu City,China and the inoculum was obtained from an anaerobic digester of a yeastproduction enterprise in Yichang City, China. The main results of this research wereas follows.1. Having shown the anaerobic characteristics of the rehmannia glutinosa dregs(1)The anaerobic experiments were conducted in self-prepared reactors under37±1℃, with the substrate to inoculum ratios were0:1,2:1,1:1and1:2(expressed as raw material). Compared the volume of methane and kinetic constant, the best ratio ofthe substrate and inoculum was1:2. Dynamic analysis shows that the0order reactiontime was0-6h, the maximum yield were657mL, and the kinetic constant k was4.06mL/h g VS.(2) Two tests were carried out at same condition, little microelement was addedin one reactor, and run against a control of reactor without microelement. The resultsshowed microelemen had little effect on gas production of anaerobic digestion ofrehmannia glutinosa dregs. So there were rich microelement contained in therehmannia glutinosa dregs to satisfy the growth of the anaerobic bacterium.2. The start-up operation of semi-solid anaerobic reactorA lab-scale semi-solid anaerobic reactor was setup to investigate the feasibilityof continuous dry fermentation of dry fermentation of the rehmannia glutinosa dregs.Under the temperature of37±1℃and organic loading rate (TS) of110g·(L·d)-1, thestable volumetric biogas production rates of three different feeding TS mass fractionswere13.15,14.37and5.19L·(L·d)-1, respectively; the biogas producing efficienciesof the reactors with feeding TS mass fractions of25%and30%were obviouslysuperior to that with feeding TS of35%. With feeding TS mass fraction increasedfrom25%to35%, the internal flow in reactor varied worse, directly affect the masstransfer process, leading to localized acidification, and the biogas production ratedecreased from135.1L·d-1to48.8L·d-1, which had decreased64.1%. Additionally,while the feeding TS mass fraction was25%~35%, the degradation rate of TS was50%. When the feeding TS mass fraction was35%, the effluent TS mass fractionachieved17.1%, and the effluent of the reactor could not be smoothly discharged. Sothe most suitable feed mass fraction of TS of semi-solid anaerobic reactor is30%,with quick start and stable operation.3. The flow characteristics of fluid in semi-solid anaerobic reactor was revealedSuppose the biogas production speed of the rehmannia glutinosa dregs remainedalmost constant in each part of the reactor, when the feeding TS mass fraction was30%. And the coalescence phenomenon of the detention biogas bubble in the reactorhad not occurred, so the bubble rising gradually and enhanced the liquidity of the surrounding fluid. The similar reynolds number formula was summaried to expressfluid turbulence of the reactor. The fluid disorder degree of the semi-solidanaerobic reactor proportional to, the height of the reactor must exceed acertain limit to make the height change have a stable effect on the fluid mixingcharacteristics of the reactor, fluid mixing characteristics of the reactor was changedfrom pushing flow to mixed flow. The further optimization design idea of the reactorwas proposed, the view of optimization design should be shaped like an "V", itsthree-dimensional shape was the inverted conical platform.