| The increasing depletion of fossil fuels and the urgent situation of environmental protection, biomass energy, as an important renewable energy, has been attracted a great number of concerns in the worldwide, the study of migration and transformation of fuel-N during thermochemical conversion process is also in progressing smoothly. However, the existing analytical testing methods could not do the qualitative and quantitative analysis about biomass N on molecular level, thus most researchers study the transformation of fuel-N in the indirect way, for example, by selecting the N-containing model compounds and changing the reaction conditions to study the emission of N-contaning pollutants during the pyrolysis/gasification, consequently the study on the transformation of fuel-N with real biomass as feedstocks is seldom reported. In addition, some industrial waste biomass which have a high heating value, has not attracted enough attention yet. The study of thermochemical conversion process of migration and transformation characteristics of fuel-N is still rare.In order to find out the characteristics of N transportation in pyrolysis or gasification with the real biomass, the following experiments were studied.3 biomass which have a high, medium and low mass content of N, the wood dust(SGF), wheat straw(MG) and pine wood(SM) were pyrolized or gasified in a fixed bed reactor, the study mainly focused on the behavior of fuel-N transportation with the changing of temperature, atmosphere(CO2, Ar, CO2+H2O) and biomass type. And N-contained functionality and N mass content in biomass and biochars were characterized by XPS and elemenary analysis respectively,The main conclusions are as follows:1) To elucidate the emission behavior of N-contained gas pollutants, the influence of temperature, atomesphere, and biomass type during pyrolysis/gasification process were studied in this essay. The effect of the temperature:when at the same atmosphere and using the same biomass feedstock, the increment of temperature will promote the release of HCN and NH3; at the temperature range of 55O-8OO℃, the generateted amount of HCN was not obvious as the temperature increased, at 850-950℃, the amount of HCN exibited a rapid growth tendency, however, the amount of released NH3 showed a steady fast increment above 550℃.2) The effect of atmosphere:when at the same atmosphere and using the same biomass feedstock, the effect of atmosphere on the release of HCN and NH3 was different. When the temperature increased from 550℃ to 900℃, the influence on HCN and NH3 emissions was found to be not obvious; but when the temperature increased to the temperature range of 850℃ and 950℃ and the atmosphere is under CO2-H2O, the release of NH3 was continuously increase rapidly, while under CO2and Ar atmosphere, the release of NH3 would decrease slightly after reaching the maximum value at 900℃.3) The effect of biomss type:When at the same temperature and the atmosphere, the effect of biomss type on release of HCN and NH3 was rather complex. By analysis the value of HCN/NH3, it can be found that the fuel-N of MG favoured to form a large amount of HCN than that of SGF and SM, SGF and SM inclined to generate NH3. As SGF included a certain amount of N-contained additives, the release amount of NH3 is significantly higher than that of MG and SM.4) The release sequency of the fuel-N of 3 biomass during pyrolysis/gasification: SGF>MG>SM. N in SGF consists of N-contained additives its own N of biomass, in wichi the N-contained additives accounted for a larger number. The stability of N-contained additives was rather more sensitive to temperature, and a large amount of that were released during pyrolysis/gasification, which was the main reason of its fuel-N easy to release; due to its low mass content of N in SM(0.07%,wt), so its fuel-N is harder to release than other two biomass. The change of 3 N-contained functionality during pyrolysis/gasification:under Ar atmosphere and at the temperature ranges from 750℃ to 900℃,the percentage of amino in MG and SGF was lower than raw material and the percentage of pyridinic N increased; The percentage of amino N in SM is higher than its raw material and the percentage of pyrrolic N decreased. SM has a greater different evolution of N-contaned functionalities than MG and SGF, which might be due to the unique structure of SM.5)N distributions in gas, solid, liquid phases:During the pyrolysis/gasification of 3 biomass, the percentage of gas N increased and the percentage of solid N thus decreased along with the increasing temperature, while the change of othe N has no uniform tendency. When the temperature increases from 550℃ to 950℃ and under above atmosphere, released gas-N from MG increased from 0.92%-3.2% to 16.7%-41.4%, and its solid-N decreased from 35.5%-49.3% to 7.4%-22.9%; gas-N from SGF pyrolysis/gasification increased from 16.4%-16.7% to 47.3%-59.3%, and its solid-N decreased from 24.2%-24.5% to 1.3%-5.4%; gas-N from SM pyrolysis/gasification increased from 10.8%-22.5% to 50.8%-59.3%, and its solid-N decreased from 59.7%-85.9% to 11.5%-21.8%. |
PDF Full Text Request