In this report, a packed bed of biomass particles undergoing pyrolysis has been two-dimensionally visualized. The apparent density of the biomass layer was also measured. The setting temperature of the furnace was changed from 523 K to 1073 K. The heating rate of the furnace was 400 K /hr. From the experimental results, it was found that the volume reduction process was closely connected with the pyrolysis and divided three regions; i) region of dehydration from biomass, ii) region of pyrolysis of cellulose and iii) region of pyrolysis of lignin. It was found that the reduction process of the biomass layer through the pyrolysis could be expressed by the reversible first-order chemical reaction model. The apparent density depended on the temperature. Especially, the density at T > 623 K became about 60% of that at room temperature. Furthermore, time course of average temperature in the biomass layer can be reproduced by the numerical simulation of the thermal conduction through the pyrolysis, which is included in the change of the apparent density and the change of the biomass surface by the volume reduction.
A two stage tubular reactor (TS-TR) was developed to study vapor phase cracking of nascent volatiles generated in rapid pyrolysis of food industry residues, namely residue from industrial production of liquid coffee. Changes in gas phase compositions were monitored in the TS-TR experiments at ambient pressure, τ~6 s, and T = 973-1073 K. These experiments were numerically simulated using a detailed chemical kinetic model that comprises 543 species and 8175 elementary-step like reactions. The numerical predictions were compared with the experimental data for more than 20 molecular species for critical evaluations of the developed kinetic model. The model successfully predicted time-dependent change of concentrations of major species such as H2, CO, CO2, CH4, etc. Production of benzene as well as consumptions of minor oxygenate compounds such as acetic acid, acetaldehyde, acetone, and methanol were also fairly reproduced. The reaction pathway analysis was performed to indentify the major reaction routes leading to primary aromatic species such as cyclopentadiene and benzene which are potential precursors of tar.
Lignocellulosic materials are composed of cellulose, hemicellulose and lignin. Since cellulose is surrounded by lignin, a pretreatment is required to enhance the contact with enzyme for enzymatic hydrolysis. So far, several methods: grinding, steaming, steam explosion, microwave treatment and so on have been studied for wood, however, it is still difficult to saccharify softwood very efficiently. In this study, soda and kraft cooking for chemical pulping were applied for the pretreatment of softwood (Japanese cedar) shaving. The lignin content of kraft pulp ranged from 12% to 3% with increasing cooking time from 1 to 3 hours. Saccharification efficiency after 1 day increased from 90% to 98% with decreasing the lignin content of kraft pulp. The soda and kraft pulp with the same lignin content showed similar saccharification efficiencies. The longer cooking time realized the smaller lignin content, but at the same time, the loss of carbohydrates was larger. As a result, the yields of sugar to wood were almost constant (40%) with a lignin content up to 10% whether the pretreatment was soda or kraft cooking. Even soda cooking is useful enough as a pretreatment method for saccharification of softwood.
The effect of the grinding of raw Japanese cedar chip as a model material of woody materials by a new type ball mill, namely converge mill, was studied for the effective enzymatic saccharification. We achieved almost 100% of saccharification degree from ground cedar powder prepared by the converge mill. The grinding time of the converge mill was shorter than that of a conventional tumbling mill. We found that the crystallinity index was more important factor than the mean diameter on the saccharification degree, indicating that the breaking of the micro fiblril structure of cellulose is more essential than the downsizing of the bulk particle. We also studied the effect of media ball types of the converge mill and found that chromium steel ball was more effective to obtain high saccharification degree than SUS 304 and stabilized zirconia balls. We investigated an optimum grinding condition for the converge mill and found that higher rotation speed, lower amount of reactant charge, higher amount of media ball charge, and smaller size of media ball were optimum conditions for the saccharification. It was concluded that the grinding of Japanese cedar by the converge mill was an effective pretreatment to achieve high efficient enzymatic saccharification.
Characteristics of pulverized wood were analyzed, and enzymatic saccharification was carried out with pulverized woods in order to understand the correlativity between pulverized wood characteristics and enzymatic saccharification efficiency of the pulverized woods. Woody biomass pulverized in a planetary mill in various periods, and then the particle size, crystallinity index of cellulose and cellulose microfibril width of pulverized woods were measured. Crystallinity index of cellulose of pulverized woody biomass decreased significantly with a longer pulverization period. In enzymatic saccharification, influence of the apparent particle size of pulverized powder on the saccharification efficiency was unexpectedly-minor in the case of long pulverization periods, but noncrystallization of the cellulose by the mechanical impact made a significant effect on the saccharification efficiency.
To assess a timber harvesting operations system incorporating the extraction of logging residues for supplying a biomass power plant, we developed a method to estimate the harvesting volumes and costs of logging residues from subcompartments with plus balances, including both timber and logging residue harvesting. We estimated harvesting volumes and costs using GIS (Geographic Information System) at Sano City, Tochigi Prefecture. Forest-registration data (stand ages, tree species, and site indices) and GIS data (information on roads and subcompartment layers) obtained from the Tochigi Prefectural Government were used in the study, as were 50-m grid digital elevation models (DEM) from the Geographical Survey Institute. These data were converted into 50-m grid raster data for consistency with DEM data. As a result, the minimum and average costs of a cut-to-length system with forwarders from subcompartments with plus balances were found to be 6,270 yen/t and 7,934 yen/t, respectively. Of the subcompartments, 16% were extracted as economically feasible subcompartments. In order to reduce costs, subsidy, stem extraction, and a whole tree logging system were considered. As a result, the average costs with subsidy were reduced to 6,566 yen/t, and 40% of the subcompartments were extracted. The average cost of stem extraction without branches was also reduced to 7,132 yen/t. The minimum and average costs of the whole tree logging system were significantly reduced to 1,794 yen/t and 3,658 yen/t, respectively. Moreover, costs considering timber extraction were also reduced. Therefore, the whole tree logging system may be more advantageous than the cut-to-length system for extracting logging residues.
Development of alternative fuel is urgent issue because of expectation of fossil fuel termination. Ammonia has advantages for high density of hydrogen fuel, and stop of global warming due to carbon-free fuel. However, the handling of ammonia must be careful of safety specifically, because toxicity of ammonia affects a human body and a fuel cell. On the other hand, urea can be easily changed into ammonia and dealt with safety. A hydrogen generation system fueled with ammonia from urea for fuel cells is described in this paper. The authors have studied urea properties, new recycle processes, system possibilities theoretically calculated, and appropriate applications. Furthermore, they have tested and proved urea decomposition by urease catalyst of enzyme without conventional high heat energy. By these studies, conditions of the appropriate urea decomposition could be achieved. The possibility of urea was examined as an energy career of hydrogen and a renewable energy without exhaustion of energy source in the future.
Effects of addition of waste plastic on the pelletizing and the combustibility of heavy oil ash were studied in this work. Carbon content and volatile matter of the heavy oil ash used in this study were about 80 and 20 wt% (dry basis), respectively. And the particle was very fine (below 40 μm in diameter) and porous (about 10 m2/g in surface area). The mixture of heavy oil ash and waste plastic in the weight ratio of 1 : 3 could be pelletized by heating at 180 °C for 1 h and then cooling to room temperature. From the combustion behavior of the mixed samples by thermogravimetric analysis, it was observed that experimental weight loss was much larger than theoretical weight loss, calculated as an algebraic sum of those from each separated component, in the low temperature region (300 - 400 °C). This indicates a significant synergistic effect during combustion of heavy oil ash mixed with waste plastic.