Biomass Syngas Conditioning Technology And Intensive Puirfication

Biomass is a kind of clean and renewable energy, rational utilization of which is aneffective method for relieving the pressures of conventional energy resources shortage andserious environment pollution. To expand the utilization of biomass gasification, Funded bySino-Italian cooperation program: Key technology research of Biomass oxygen richgasification (2009DFA61500), a cold bubbling fluidized bed, a fluidized bed gasificationsystem of which maximum capacity is50kg/h, the effect of different gasification conditionson results, regulating and controlling the gas compositions through selective appropriate craft,developing product gas decontamination plant, completing product gas cleaning technology,coming up with product gas deeply cleaning craft, performance and emission of vehiclefueled with product gas and the effect of different conditions on methanol were studied in thepresent paper.The application and research status of biomass gasification technologies were firstlyinvestigated in the thesis. It is founded that there are some problems in biomass gasificationfor application, such as CO content is too high while CH4content is too low in biomassgasification for fuel gas; H2content is too high to detonation in the engine in biomassgasification power plant; H2selectivity is too low in biomass gasification for hydrogen;H2/CO volume ratio is too low in biomass gasification to methanol. All in all, how to regulateand control the compositions of product gas is one of the most important problems in biomassgasification technology. Moreover, there are some kinds of impurities in product gas, such assolids, tar, NOx, NH3, HCN, HCL, SOx, H2S, C2S and so on, to which lead some kinds ofproblems in application. Therefore, optimizing product gas cleaning crafts and developingnew effectively cleaning devices to strip the impurities is a key technology for product gasapplication.Due to advantages of excellent gas-solid mixing, uniform bed temperature, intensivemass and heat transfer and easy scale-up, fluidized bed gasifier is thought as one of the mostpromising reactors. It is necessary to design and produce a fluidized bed gasification systemto solve the problems about which are talked above. In order to get the parameters of fluidizedbed, a cold model was trial-produced with organic glass firstly and series of cold experimentswere carried out to measure the minimum fluidized velocity on different diameters of solidsand get the pressure drop of distributor. Then combining the results of cold experiment withselecting feed rate50kg/h, the parameters of bubbling fluidized bed system are calculated.Ruled by similarity principal, a bubbling fluidized bed system is produced. Aimed at testingthe reliability and stability of the system, cold test and hot debugging were carried out. Theresults as follows: the aperture ratio of distributor is1%, which gets adaptable pressure dropand distributes well; the minimum velocity of quartz sand (0.38mm), sawdust (0.83mm), themixture of quartz sand quartz sand sawdust is0.21m/s,0.13m/s,0.16m/s, respectively; through 3h running, it is indicated that the bubbling fluidized bed system is reliable and stable; the lowheating value of product gas is between6200kJ/m3and6500kJ/m3.Design experiment for mastering the effect of different conditions on biomassgasification, which mainly investigates the react temperature, the characters of feedings,gasification agent, the structure of reactors and so on. It is founded that equivalence ratio andreact temperature is a key factor on gasification result; biomass oxygen rich gasification is aeffective way to produce medium heating value product gas; the effect of using steam ongasification is pros and cons, on the one hand, it is obvious to increase the H2content, on theother hand, it makes the react temperature decrease which is disadvantage to gasification; thecharacters of feedings and structure of reactors are both important factors on product gascomposition; compared with other gasification agent, steam-oxygen rich biomass gasificationis a reliable way to make up syngas.Based on the effect of different factors on product gas composition, the fixed bed gasifierhigh equivalence ratio biomass oxygen gasification for medium heating value product gas andthe bubbling fluidized bed oxygen-steam gasification for syngas were designed. The fixed bedexperimental results show that the react temperature, carbon conversion and gas yield allincrease, while the low heating value decrease, with the equivalence ratio increase from0.31to0.4; via increase equivalence ratio to increase react temperature is a effective way todecrease the tar content,1075℃is an important point on tar desorption. The fluidized bedexperimental results show that both H2and CO content increase, while H2/CO ratio is changelittle with the input of external heat; H2and CO2content increase, while CO, CH4and CnHmdecrease, and tar content decrease from1210mg to38mg, with the increase of secondary flowrate; when the equivalence ratio is0.34, the steam to biomass ratio is1.7, the H2/CO ratio ofproduct gas is1.593, which is the maximum one in the trial stretch.Because of the high cleaning demand of biomass syngas for methanol, the tar cracking,physical denitrification, chemical dechlorination and desulfuration are investigated mainly inthis chapter. The experimental results indicate that H2content in tar cracking gases increasesquickly, while CH4、C2H6、C2H4content decreases slowly, CO and CO2content changes littlebut getting the opposite trend, the yield rate of tar cracking increase sharply and cracking rateis79.03%at1000℃，with the cracking temperature increas；using silica gel as filter materialto denitrification, the NH3and HCN content is0.32ppm and0.17ppm in the product gas,respectively; using LG-02as catalyst to desulfuration, the H2S and CS2content is0，the COScontent is46ppb in the product gas; based on the experimental results, a product gas deeplycleaning craft is designed, which supplies technical support for biomass gasified syngas.Performance and emission of vehicle fueled with gasified biomass gas is carried out toinvestigate the dynamic property and emission features. The product gases derived from airand oxygen rich biomass gasification were used as the vehicle fuel for testing the runningperformance and its emission behavior. The results were as following: under the same roadcondition and for the same vehicle, the kilometers of travel with air gasification producer gas as fuel were one third of that with oxygen rich gasification producer gas as fuel, and thekilometers of travel with oxygen rich gasification producer gas as fuel were one third of thatwith CNG as fuel; the producer gas composition had little influence on the carbon monoxideemission in the exhaust gas, but the excess air ratio had crucial impact on the carbonmonoxide emission; with air gasification producer gas as fuel, the content of the hydrocarbonsin the exhaust gas was lower, and it was higher when being with oxygen rich gasificationproducer gas as fuel, for both fuel gases, the content of the hydrocarbons had the sametendency of increasing along with the increasing of the RPM of the engine; the producer gascomposition had definite influence on the NOxemission in the exhaust gas, meanwhile, thetemperature was the dominating factor of the thermal NOxemission. The results showed thatthe biomass gasification producer gas could be a kind of clean and renewable substitute fuel.Design match experiments for mastering the effect of synthesis (H2and CO) and syngason synthetic methanol. The experiment results show that the optimum temperature ofsynthesis and syngas for methanol is250℃and255℃, respectively; under the sametemperature and for the same space velocity, the space-time yield of methanol and conversionof CO increase, while the conversion of CO2decrease, with the increase of react pressure; themaximum space-time yield of synthesis and syngas is82%and47%, respectively; under thesame temperature and for the same react pressure, the space-time yield of methanol increase,while the conversion of CO decrease, the conversion of CO2and the selectivity of methanol inliquid-phase production change little, with the increase of space velocity increase.