It is essential for old coke ovens to avoid pushing trouble because this trouble, which has increased gradually with the aging of coke oven, negatively affects coke stable production and coke oven service life. As one of effective approaches to improve pushing condition is to maintain sufficient clearance between coke cake and heating wall, it is important to clarify control factors for the lateral shrinkage of coke cake. At the beginning, the relationship between fissure existence form to the inside of coke cake and clearance was investigated by using X-ray computed tomography scanner and image processing system. And it was clarified the importance of controlling fissure ratio, especially total fissure length closely correlated with fissure density. Then, the influence of Ro variance (σRo/Ro) as the characteristic factor of coal blend on fissure in coke cake and clearance was estimated. As a result, the clearance was strongly dependent upon σRo/Ro and its effect was verified at the commercial operation. Eventually, it was cleared that σRo/Ro of coal blend was one of the important parameter to control clearance.
Volume and surface breakage rate parameters of conventional and formed cokes were evaluated by using drum test data. Finer crushing of coal lowered both the volume and the surface breakage rate. Conventional and formed cokes, some of which had been partially reacted with CO2 gas, were compared. The formed cokes had higher post reaction strength indices than conventional cokes, because their increases in surface breakage rate caused by the reaction with CO2 gas were less than those of conventional cokes. One of the formed cokes had lower post reaction strength indices because of the high volume breakage rate.
Displacement of coke oven chamber wall and gas pressure in the chamber was measured during carbonization, especially focused on the coal charging, in order to realize the load to the actual chamber wall. Maximum wall displacement and very large gas pressure peak were observed at CMC coal charge with 6-7% moisture. They started with coal charging and reached maximum at the end of the charging. The gas pressure at charging was higher at oven bottom and smaller for upper part. The gas pressure peak at charging was larger than the pressure in the later carbonization period or internal gas pressure. Wall displacement and gas pressure peak at coal charging were both small in a case of wet coal charge with over 9% moisture. High gas pressure generation in CMC coal charge was thought due to the carbonization gas and the low gas permeability of coal bed. The permeability of CMC coal bed is lower than that of wet coal due to not only the higher bulk density but also moisture itself. The difference in permeability together with the gas generation was large enough to explain the observed difference in the peak gas pressure.
Coke making is becoming more expensive because of the sudden rise in the price of caking coals due to the decreasing supply, and so a technology to manufacture good-quality coke from coal blends containing low-quality slightly caking or non-caking coals is strongly required. "HyperCoal" (ash-free coal, HPC) is produced by thermal extraction using cost-effective industrial solvents below 400 °C in an inert atmosphere. It has originally a wider temperature range of thermoplasticity during heating than ordinary caking coals. HPC can be produced from various ranks of coals including lignite and subbituminous coal, however, the chemical property of HPC is different depending on the coal rank. HPCs produced from low-rank coals such as lignite and subbituminous coal, showed a high thermoplasticity from lower temperature range than those from high-rank bituminous coals. In addition, HPCs from low-rank coals possess a higher permeability due to the lower viscosity in the thermoplastic region. As a result, the addition of HPCs from low-rank coals to a coal standard blend showed a higher effect on the tensile strength of cokes produced by carbonization of the HPC-blending coals at 1000 °C, than that of HPCs from caking coals.
It is well known that the excessive deposition of pyrolytic carbon on coke oven walls causes some troubles such as increase of pushing force during discharging of coke from coke chamber and damage to the oven walls. A purpose of this study is to clarify the influence of coal properties and temperature on carbon deposition rate on oven wall. The effect of the volatile mater, pyrolysis gas components of coal and the temperature of the wall on carbon deposition rate was quantitatively examined. By using this empirical formula, the correlation of calculated carbon deposition rate and change of pushing force was confirmed.
A new production method from waste plastics to high quality solid fuel has proposed in order to overcome the disadvantage in thermal utilization of waste plastics such as low bulk density, difficult handling. The concept proposed lies in the prevention of a massive waste plastic and the adhesion to the equipment inner wall by the addition of an inexpensive material. Through examination of several combinations with waste plastics and additives, it was found that fine carbon material was suitable additive to form a granular solid without fusion and massive. Thus prepared granular solid had excellent properties; easy burning, easy grindability, and safety handling. In addition, it was confirmed that the proposed method realized high thermal recovery efficiency more than 90% from the calculation of energy balance. From these results it was clarified that the proposed method will be an efficient utilization way to utilize waste plastics as a high quality fuel solid feedstock for present commercial plants such as pulverized coal burner.
Supercritical water gasification is a promising technology to recover energy from wet waste biomass feedstock. To properly design the supercritical water gasification plant, heat transfer characteristics of the heating section is essential. Although the supercritical water has been an object of study for a long time, report on heat transfer characteristics of the flowing biomass slurry feedstock is limited. The purpose of this study is to measure heat transfer characteristics of biomass slurry flowing in the tube. Heat transfer characteristics of the biomass slurry was measured experimentally, and correlation was made to predict the heat transfer characteristics. The resulting is applicable only to the biomass slurry tested here, but the procedure developed in this study should be applicable to other kinds of biomass slurry.
Efficient pretreatment prior to enzymatic saccharification process is essential for profitable bioethanol production from woody biomass. Microwave pretreatment is expected as an efficient and energy-cost-saving method to enhance enzymatic susceptibility. The objective of the present study is to develop an efficient, high-volume, and continuous microwave pretreatment system toward commercially-based bioethanol production. As a feasibility study, we developed prototypes of a continuous-flow-type microwave pretreatment system for bioethanol production from woody biomass. A unit of the microwave irradiation sections of a continuous-flow-type microwave pretreatment system was designed with a 3D electromagnetic simulator. Prototype experiments and quantitative estimation of energy balance were also conducted. Microwave pretreatment provided 45.9% of the total saccharide yield woody biomass weight by electric consumption of 552 kJ; whereas conventional heating pretreatment provides 43.6 % of the total saccharide yield by 498 kJ, when the mixture was composed of 70 g of woody biomass (Japanese cedar sapwood chips) and 770 g of solvents (ethylene glycol : phosphoric acid = 95 : 5). We estimated 14.8g of bioethanol and 439 kJ of bioethanol energy could be produced by the prototype microwave pretreatment. Although heat dissipation from the metal pipe to the air and the ratio of solvents to woody biomass are immediate problems, microwave is a future potential energy-saving pretreatment method without loss of the saccharide yield.
Empty fruit bunch (EFB) and bagasse, which are now and in near future quite abundant biomass residues in Southeast Asia, were gasified using steam or (steam + oxygen) as a gasification agent in an entrained-flow type gasification reactor at 900 °C. When using steam alone, EFB was gasified well (carbon conversion rate into gas was defined as "gasification rate": over 95%) and the hydrogen-rich gas suitable for liquid fuel synthesis ([H2]/[CO]=about 3-3.6) were obtained. Theoretical value of [H2]/[CO] required for many types of liquid fuel synthesis processes is about 2. However, hydrogen rich gas is desirable, because the processes are stabilized by the excess hydrogen. Bagasse was not so well gasified (gasification rate: about 90%) and the [H2]/[CO] was about 1.5-1.8, which was lower than that of EFB, in spite of being gasified under similar gasification conditions. When adding oxygen to steam, gasification rates of both EFB and bagasse were improved (over 98%). By adding oxygen, the [H2]/[CO] obtained from the EFB decreased from 3.6 to 2.7, which were still high enough for liquid fuel synthesis. The ratio from the bagasse decreased to 1.3, which was much lower than optimum value, 2, for liquid fuel synthesis. Tar yields of all the cases were quite low (<0.1 wt%), which were mainly composed of six poly-cyclic aromatic compounds, such as naphthalene. Solid residues yields of all the cases were also low. Solid residues obtained from the EFB were softened products, which partially adhered to the reactor. We also performed thermo-gravimetric (TG) analyses using a thermo-balance specially designed for analyzing feedstock in the presence of oxygen, steam, or both. The TG analyses showed that the EFB decomposed well in the presence of steam, oxygen or both, and that the bagasse did not well decompose in steam but well decomposed in oxygen or oxygen and steam. The TG analyses and the results of gasification were compared to each other and found to agree approximately. The EFB was gasified well using steam alone to produce hydrogen-rich gas suitable for liquid fuel synthesis, but treatment of solid residues would be required. The bagasse was also well gasified by adding oxygen to steam, but further adjustment of gas composition ([H2]/[CO]) would be required for liquid fuel synthesis.
Hydrogen as an alternative fuel has some problems, which include a little practical infrastructure, low volumetric energy density, explosion risk and high energy cost. In order to minimize those problems, ammonia is considered as a hydrogen career fuel. Urea is also considered as a hydrogen career for handling, safety and energy recycle, but ammonia contains such disadvantages as fossil fuel involvement in production process, high production energy cost and toxicity. In the previous paper, it was showed that the urea energy recycle system which collects ammonia or urea from human body, livestock, sewer and waste plastics converts them to hydrogen, and the co-generation system which generates electricity, hot water and cooling systems were discussed. In this paper, the authors would discuss an optimization method for conversion of urea to hydrogen fuel and experiments in a laboratory to prove the feasibility. Moreover they would like to discuss advantages and disadvantages and practical execution (method, location etc.) in the urea energy recycle system, and propose one of the possibilities in the diversity of alternative energies.