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Title: Production and chemical utilization of bio-oil by fast pyrolysis of sewage sludge
Other Titles: 下水汚泥の急速熱分解によるバイオオイルの生産と化学利用
Authors: 曹, 景沛
ソウ, ケイハイ
Chao, Jin-Pei
Keywords: bio-oil
chemical utilization
fast pyrolysis
sewage sludge
Issue Date: 23-Mar-2011
Publisher: 群馬大学工学部
Abstract: Fast pyrolysis of sewage sludge (SS) fbr bio-oil production is considered as a promising alternative technology instead of its less acceptable common disposal processes, including agriculture application, landfi11, and incineration. However, high nitrogen content in SS represents a drawback of pyrolysis use due to the fbrmation of NH3, HCN, and organic nitrogen species (ONSs), which are converted to NO. and N20 during combustion, causing severe environmental pollution, including acid rain, the greenhouse effect, and ozone layer depletion. Great care should be taken to study the fbrmation, distribution, and chemical composition of nitrogen containing species (NCSs) in pyrolysis products of SS in order to minimize the nitrogen content in products fbr fuel use or effe ctively convert them fbr chemical us e. In chapter 3, fast pyrolysis of a SS sample, which contains a high content of nitrogen, w as investigated in a drop tub e furnac e to underst and the effects of pyrolysis temper ature and sweeping gas flow rate (SGFR) on the yields of pyrolysis products and the distributions of carbon and nitrogen. The maximum oil yield of ca. 48.7% (daD was ac hieved at a pyrolysis temp erature of 5 00 OC and a SGF R of 600 cm3/min. NH3 was fbund to be the pre domin ant nitrogenous gas under all the conditions, and its yield incre as ed with raising pyrolysis temperature and decreasing SGFR. The significant release of NH3 at temp erature s lower than 5 00 OC should be related to the hi gh prote in content in the sludge. The N yield in HCN was lower than 2% during pyrolysis below 550 OC, and sharply increased to 5.8% at 700 OC due to thermal cracking of volatile matter. Water-insoluble nitrogen- and carbon-containing species were significantly decomposed to water-soluble ones during secondary reactions. At high temperatures, heavy hydrocarbons were mainly cracked to gaseous products, while the NCSs tended to fbrm water-soluble species. This study provides a basic insight into the nitrogen transfbrmations during fast pyrolysis of SS, which would benefit the clean utilization of SS as an energy source. In chapter 4, fast pyrolyses of SS, pig compost (PC), and wood chip (WC) were investigated in an internally circulating fluidized-bed (ICFB) to evaluate bio-oil production. The pyrolyses were perTfbrmed at 500 OC and the bio-oil yields from SS, PC, and WC were 45.2,44.4, and 39.7% (daD, respectively. The bio-oils were analyzed with an elemental analyzer, Karl-Fischer moisture titrator, bomb calorimeter, gel permeation chromatograph, Fourier transfbrm infiTared (FTIR) spectroscopy, and gas chromatography/mass spectrometry (GC/MS). The results show that the bio-oil from SS is rich in aliphatic and ONSs, while the bio-oil from PC exhibits higher caloric value due to its higher carbon content and lower oxygen content in comparison with that from SS. The bio-oils from SS and PC have similar chemical composition of ONSs. Most of the compounds detected in the bio-oil from WC are organooxygen species. Because of its high oxygen content, low H/C ratio, and caloric value, the bio-oil from WC is unfeasible fbr use as fuel feedstock but possible fbr use as chemical feedstock. In chapter 5, the bio-oil from the SS fast pyrolysis was separated by silica-gel column chromatography (SGCC) with different solvents, including mixed solvents, as eluants. A series of alkanenitriles (Ci3-Cis), alkenenitrile, oleamide, fatty acid amides, and aromatic nitrogen species were fractionated from the bio-oil by SGCC and analyzed with GC/MS and FTIR. The possible precursor and fbrmation route of ONSs detected were also discussed. Most of the GC/MS-detectable ONSs are lactams, amides, and N-heterocyclic compounds, among which acetamide is the most abundant. N-heterocyclics with 1-3 rings, including pyrrole, pyridine, indole, benzoimidazole, carbazole, norharman, and harman, were observed. The lactams detected include pyrrolidin-2-one, succinimide, phthalimide, glutarimide, piperidin-2-one, and 3-isobutylhexahydropyrrolo[1,2-a]-pyrazine-1,4-dione, all of which sho uld be fbrmed via decarb o xylation and cyc lization of y- and 6- amino acid s. Such a procedure provides an effective approach to fractionation and identification of ONSs from bio-oil pro duced by fast pyrolysis of SS. In chapter 6, when fast pyrolysis of SS at 500 OC and SGFR of 300 cm3/min, triacetonamine (TAA) was detected with GC/MS as major component in the resulting bio-oil using acetone as the absorption solvent and proven to be a product from the reaction of NH3 in the bio-oil with the absorption solvent acetone. TAA yield increased with storage time and reached a level about 28.4% (% sludge fed, daD after 175 h. Since the reaction ofpure NH3 with acetone does not proceed, some species in the bio-oil must catalyze the reaction of NH3 with acetone. TAA was isolated in a high yield (27.9%, daD and high purity (80.4%) by SGCC with different solvents, including mixed solvents, as eluants. The study revealed the possibility of SS as potential resource of TAA.
Description: 学位記番号:工博甲419
URI: http://hdl.handle.net/10087/6243
Academic Degrees and number: 12301甲第419号
Degree-granting date: 2011-03-23
Degree name: 博士(工学)
Degree-granting institutions: 群馬大学
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