Tu D.,Anhui University of Technology |
Tu D.,Key Laboratory of Energy Resource Utilization |
Li A.,Anhui University of Technology |
He G.,Anhui University of Technology
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015
The former result of cold pressing forming experiments for rice straw showed that the rice straw cold pellets had poor quality. We found that wood chips had a high content of lignin which can take the function of the binder in high temperature condition. To improve the quality of rice straw pellets, it was proposed to take some wood chips added to the rice straw materials which could form the mixed raw material with the research carried out through the test method. We chose raw straw material which was produced in the south area of Anhui, 2012 and wood processing plant residues-pine sawdust. The equipment of closed compressing molding experiment were design by ourselves. Firstly, pellets' physical properties (loose density, shatter resistance, compressive forces and water resistance) were chosen as judgment criteria, and contrast hot pressing forming experiments was carried out to investigate the effect of different materials(rice straw, wood chips and 1:1 blends of rice straw and wood chips) on pellets. Two hours later after experiment, physical properties were tested, and the date were analyzed by DESIGN EXPERT8.0 with the orthogonal design method of multi-index analysis-comprehensive balance. By analyzing the results of contrast tests, we find that under lower compressive forces, the comprehensive physical (loose density, shatter resistance and compressive forces properties) of 1:1 blend material pellets were better than rice straw pellets and wood chips material pellets, and the results also indicated that added wood chips in the rice straw material can indeed improve the quality of single rice straw material pellets. However, because of the structural feature of wood chips material, the 1:1 blends of rice straw and wood chips material pellets were more weaker than rice straw and wood chips materials pellets in the respects of water resistance physical property. In the actual production, one or more physical properties should be requested high based on the specified use of pellets. Therefore, to further research the effect of blends on the quality of pellets, secondly, we take mixing materials of rice straw and wood chips as research object, a set of orthogonal hot pressing forming experiment with three factors and four levels were used to investigate the effect of compressive forces, mixing ratio and temperature on mixing materials pellets. It aimed to respectively get the most significant effect factors and the reasonable combination of three parameters (compressive forces, mixing ratio and temperature) for each pellets' physical property and the result will testify by test. The orthogonal experiment results indicated that each process parameter had different impact extent to various physical properties. Indexes of loose density, shatter resistance and compressive strength were strongly correlated with compressive force, and the mixing ratio has massive effect on the index of water resistance. The reasonable parameter combination for water resistance and compressive strength: the mixing ratio was 1.5:1 and the temperature was 90℃ and compressive strength was 31.11 MPa. The reasonable parameter combination (mixing ratio, temperature and compressive forces) for loose density was 0.5:1×70℃×31.11 MPa, and for shatter resistance was 2: 1×110℃×31.11 MPa. Third, in order to testified the orthogonal experiment results, each reasonable parameter combination of physical property were text contrast with the reference group. The contrast group for physical properties (loose density, shatter resistance, compressive forces and water resistance) were respectively group two, group sixteen, group eleven, group seven. Other parameters of experiment were same as much as possible. Two hours later after experiment, physical properties (loose density, shatter resistance, compressive forces and water resistance) were tested and the date were analyzed. The result showed that each estimated value of treatment group are higher than reference group value, so the orthogonal experiment results were testified. The conclusion can provide technical support for industrialized production of rice straw molding fuel. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.
Liu B.,Key Laboratory of Energy Resource Utilization |
Liu B.,Huazhong University of Science and Technology |
Chen Y.,Huazhong University of Science and Technology |
Meng H.,Key Laboratory of Energy Resource Utilization |
And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2014
To study the characteristics of biochar products from biomass pyrolysis, cotton stalk and rapeseed straw were used as raw materials to prepare pyrolytic biochar samples under various temperatures (350, 550, 750, 950°C). The combustion characteristics, hydrating properties, CO2 adsorption characteristics, phenol adsorption characteristics and antioxidant abilities of different biochar samples (marked as CS350, CS550, CS750, CS950, RS350, RS550, RS750, RS950) were compared. A thermo gravimetric analyzer (STA409, NETZSCH) was used to investigate the combustion behavior of char. In the thermogravimetric experiment, approximately 10 mg of sample was heated in TG equipment at a heating rate of 20°C/min from room temperature to 900°C. TG-DTG tangent method was employed to determine the combustion characteristic indexes, including ignition temperature (Ti), burnout temperature (Tf) and the maximum mass loss rate (DTGmax). Results showed that the Ti and Tf value of char was increased with pyrolysis temperature increment, and CS550 and RS750 had better combustion characteristics due to their higher heating values and faster combustion rates, and they were appropriate for use as fuel char. Water absorption characteristics of char were conducted in a constant temperature and humidity box (Temperature: 30°C, Humidity: 90%), and an oven setting at 55°C was used to test the dehydration characteristics of the chars. Gravimetric method was used to describe the water absorption and dehydration process of char and soil. The test results showed that CS350 and RS550 had higher water absorbing capacity and water retaining capacity than soil and other chars, and they were appropriate for biochar. CO2 adsorption characteristics of char were measured in an automatic adsorption equipment (Micromeritics, ASAP 2020, USA) at 273 K. Before the adsorption measurements, the sample was degassed at 150°C under a vacuum (pressure of 50 lmHg) for 10 h. The test results showed that the pyrolysis char had a good CO2 adsorption ability, varying from 25 mg/g to 115 mg/g. This capacity was proportional to the micropore volume of biochar, which was 4 to 30 times higher than that of soil. These chars can be used as biochar to reduce CO2 concentration of underground environment, but also can be used as CO2 absorbent to improve the quality of syngas in biomass pyrolysis system. Phenol was used as a model compound to investigate the water purification ability of char. UV-visible spectrophotometer (Lambda 35, PerkinElmer, America) was used to measure the concentrations of the filtered and blank sample. Results showed that the phenol adsorption capacity of char was proportional to their micropore volume. CS750 and RS950 had strong capacity of phenol adsorption, and they were appropriate for use as the activated carbon to remove contaminants of water. The investigation methods of antioxidant abilities of biochar were the same with combustion behavior research. A parameter, R50 was employed to evaluate the carbon sink of char. R50 can be expressed as: R50=Tbiochar,50/Tgraphite,50, where Tbiochar,50 and Tgraphite,50 are the corresponding temperature to the 50% mass loss of char and graphite in TGA experiment, respectively. Results showed that the R50 value of biochar increased with pyrolysis temperature increment, which indicated that the char prepared at high temperature was difficultly to be decomposed in aerobic environment. Meanwhile, the cotton stalk derived char had a larger R50 value than that of rapeseed straw. This demonstrated that the cotton stalk char had a more stable structure compared with rapeseed straw char. In conclusion, pyrolysis temperature had a strong impact on properties of biochar made from cotton stalk and rapeseed straw.