Study On The Distribution Characteristics Of Nitrogen And Releasing And Transformation Of Nitrogen During Pyrolysis Of Biomass

With the need of growth, nitrogen content of biomass is high, which is easier to volatilize during biomass thermal conversion. Nitrogen volatiles would form gas pollut ants or condensate in the liquid product, which may cause environmental problems a nd inhibit the further use of the products. In order to investigate the mechanism of releasing and transformation of nitrogen, the distribution characteristics and transformat ion of nitrogen forms were explored, which is advantageous to the clean and efficient utilization of biomass.In this study 15 kinds of biomass were selected as raw materials. measured The total nitrogen and protein nitrogen content were analyzed by elemental analyzer and kjeldahl nitrogen determination apparatus, respectively. Results show that the protein nitrogen content of the agricultural and forestry waste accounted for 80% of the total nitrogen content, while that of Oil seed crops is lower, which is around 70%. The test revealed that protein is a major occurrence form of nitrogen in biomass. Then the amino acid analyzer was used to measure the amino acid content of biomass. Experiments show that the amino acid content of biomass have high homology, with the decreasing order of polar amino acid > nonpolar amino acids > aromatic amino acids > heterocyclic amino acid. Corresponding to the four types of amino acids, the highest levels for each type is glutamic acid, alanine, phenylalanine and praline, which can be used as the nitrogen model components.To explore the influence of temperature on pyrolysis characteristics, four temperatures were chosen, which are 350 ?, 450 ?, 550 ? and 650 ?. Results show that with the increase of temperature, when the cellulose blended with glutamic acid, the nitrogen content in char is decreased, while that in pyrolysis tar and gas are increased. The change is more obvious at low temperatures. NH3 in the pyrolysis gas is increased, while the HCN content has little change at low temperatures, and it increased significantly when the temperature increased to 650?. When cellulose reacted with alanine, the nitrogen content in char was increased between 350? and 450?, then decreased when temperature reached over 450?. Nitrogen content in pyrolysis tar was decreased with the increasing temperature. When the lignin blended with glutamic acid, nitrogen content of pyrolysis char and gas increased with temperature rising, nitrogen content of pyrolysis tar is just the opposite. The ammonia production increased, while the HCN content decreased. When lignin reacted with alanine, nitrogen content of pyrolysis char changed a little, while gas nitrogen content increased obviously.To investigate the releasing and transformation of Nitrogen during pyrolysis process, four kinds of amino acid were mixed with cellulose and lignin, respectively. Results show that the reactions between lignin and polar amino acid as well as aromatic amino acid aremore intense. And lignin can increase the nitrogen content in the gas. When amino acid mixed with cellulose, the higher of the amino acid concentration, the more intense of maillard reaction. The maillard reaction mainly caused the increase of nitrogen content in the pyrolysis oil. The maillard reaction between amino acids and cellulose is stronger than the interaction between the amino acid and lignin. This is determined by the structure of cellulose. The impact of lignin on biomass nitrogen migration is more intense than that of cellulose.