資源工学

Energy recycling is one of the promised technology to utilize solid wastes.The power generation process of Refuse Derived Fuel (RDF) produced by solid wastes is the suitable process for widely spread smaller sources, since RDF has enough properties for the storage and also for the transportation to an integrated power slation.In this paper, RDF production process and its properties are introduced.Then, the combustion properties of the single RDF particle are shown. Experimental results of the laboratory scale bubbling type fluidized bed combustor are introduced.Combustion test data of RDF by using the industrial 70.6t/h internal circulating type bubbling fluidized bed boiler are also shown and the behavior of DXNs is demonstrated.

A Increasing amount of waste plastics which causes serious pollution problem is a cheap and abundant source of chemicals and energy.The chemical recycling method, which converts waste plastics to useful hydrocarbons and monomers of the plastics, is recognized as a useful approach. The waste generated from factories is almost a specific resin, and the chemical recycle technology is being established for each plastics.However, the waste generated from household is mixture of the waste plastics.The technology developed for each plastics from factories is scarcely applicable for the waste from household.Here, a possible process, which enables to convert the mixture of waste plastics to fuels, is proposed.The key technologies of this process are; one is the usage of steam as a carrier gas, which accelerates the hydrolysis of oxygen-containing resin, the second the iron and Ni supporting REY zeolite catalysts, which show high activity in steam atmosphere, the third is a new type reactor with moved particles as a heat-medium for the pyrolysis.The utility of this process was examined by applying it to recover fuels from the mixture of poly-ethylene and poly (ethyleneterephthalate).

In recent years, recycling of the prastic wastes has increased in importance for the environmental conservation and energy recovery.It is nessecery to develop separation techniques of the plastics from the compound wastes which consisted of plastic and metals and these materials machanically coupled with each other.In this paper, we introduce a new separation technique of plastics from compound wastes using a molten salt developed by the authors.A simple theoretical model was developed for predicting of the separation phenomena.The model includes both heating and deformation processes of the plastic.The heating process was analyzed as the boundary value problem of heat conduction involving with heat transfer.The flow of the fluidized plastic was described as a high viscosity flow driven by the buoyancy force.The separation time was theoretically derived from a combination of the heating time and the deformation time.The theoretical result was found to agree well with the experimental result.

Composting involves the biological decomposition and stabilization of organic materials under conditions that allow the development of thermophilic temperatures as a result of biologically produced heat, and should yield a final product sufficiently stable for storage and application to land without adverse environmental effects.Aerobic composting, the decomposition of organic materials in the presence of oxygen, releases significantly high energy per weight of the organics decomposed.Thus, aerobic composting is suitable for production of a thermophilic temperature under which the decomposition rate of organics is high. Further, the process results in considerable drying of the final material;this is effective for reduction of subsequent handling costs, increases the attractiveness of compost for reuse, and pathogens and parasites that may be included in the original composting material are destroyed.The present article summarizes the special conditions of moisture and aeration required for effective aerobic composting. Further, the effects of the turning of the composting material on the rate of organic matter decomposition during the aerobic composting have been overviewed.A numerical model is then introduced in order to calculate the rate and the degree of organic matter decomposition, the temperature, and the moisture content under various aerating operations.The model was used to investigate the optimum conditions to obtain sufficiently dry compost.Calculations based on this model suggest that water can be eliminated most effectively when aeration is controlled such that the reactor is kept at its optimum reaction temperature;i.e., 60°C.

The recent growing interest in the global environment protection and resourceconservation has necessitated the development of recycling technology in various fields.In the field of polymer materials for automobile as well, especially, technological development forlarge plastic parts is required.Most of large plastic parts are painted by thermoset resin orlaminated with mutually incompatible polymers.So, the recycled materials obtained bysimply melting and kneading have poor mechanical properties because the matrix resins of therecycled materials contain paint fragments or incompatible polymers to the resin.So, it isnecessary to develop the recycling technology eliminating the default by the paint fragmentsand the incompatible polymers.Recently, several recycling technologies were developedwith twin screw reactive extruder.In those technologies, paint fragments are decomposed byreactive agent and polymers are mutually compatibilized by reactive compatibilizer undershear force given by the extruder.In this paper, recent studies were introduced on recyclingtechnologies with reactive extruder for large plastic parts of automobiles, such as paintedbumpers and inner compounds containing foam material.

For the purpose of utilization of waste plastics, waste plastics recycling system was installed in NKK Keihin No.1 Blast Furnace at Oct.1996.To investigate the optimum particle size of plastics injected into a blast furnace, the combustion and gasification behavior of waste plastics has been studied with the drop tube furnace, raceway hot model and the commercial blast furnace.From the observation of a single plastic combustion by the drop tube furnace experiments under around 1200°C, the burning rate of coarse plastic was slower than that of pulverized coal.On the contrary, from the results of plastics injection test with the raceway hot model and commercial blast furnace, it was estimated that combustibility of coarse plastics was much different from that of pulverized coal.The combustion point of coarse plastics located to deep domain in raceway compared with those of fine plastics and pulverized coal.The coarse plastics gave high combustion and gasification efficiency compared with fine plastics and pulverized coal.Moreover, the decomposition products of plastics in the blast furnace top gas and dust were the same as that of pulverized coal operation, although hydrocarbons due to the decomposition of plastics was detected in in-furnace.Thus, it was concluded that waste plastics was completely consumed in the blast furnace, and furthermore, coarse plastics particle was effectively utilized as a reducing agent.On the basis of above results, it is considered that waste plastics injection into the blast furnace is a favorable way to realize material recycling of waste plastics and to solve environmentalissue.

Biogasification occurs in the process of anaerobic fermentation for organic materials.The gas from the anaerobic fermentation process consists of 60%methane gas and 40% carbon dioxide and we call it Biogas.We can use it as the fuel for gas diesel generator obtaining the electricity and heat simultaneously or for CNG automobile.The biogas comes from solar energy and carbon dioxide, so we can also call it “Renewable Energy”. The Anaerobic fermentation is not new technique, but is rather regular technique such for the sewage sludge treatment.The anaerobic fermentation that I am going to describe here is for the organic solid wastes such as kitchen waste, yard waste or food waste and the technique for them has been newly developed in Europe this latest decade.In Japan, we treat the solid wastes by incineration as usual. But the imperfect incineration often yields contaminants that contain unknown material such as dioxins.The organic waste contains a lot of water and it makes the incineration unstable and the risk of emission of contamination increases.More over, the packaging material recycling act that is going to run from 2000 will reduce papers and plastics from the domestic wastes, so the ratio of organic wastes in the domestic wastes will increase relatively then.Biogasification process will become necessary technique to reduce the organic waste from the domestic wastes then and it can yield safe energy and compost.Biogasification technique will become one of most important techniques for environmental safeguards and recycling.

Entrained-flow biomass gasification is one of the most promising technologies for utilizing biomass as energy and chemical resources because of its high gasification rate (carbon conversion rate from biomass to gas), low GHG(greenhouse gas) emission and high controllability of synthesized gas compositions. These advantages are attributable to its unique gasification reaction of solid biomass entrained in gas of upstream, one of the typical examples of multiphase flow. However, basic gasification reactions, such as behavior of biomass in gas and time-dependence of gas compositions, are not clarified enough. In this report, simple and basic phenomena are qualitatively overviewed.

A lot of forest-biomass exists on the steep mountain in Japan. However, it is very difficult to obtain the forest-biomass like brushwood, from the deep mountain to human habitation. Using by chute, brushwood can be transported automatically if we can keep an appropriate slope gradient. The most important point is a repose angle of chip on the slope. These angles are strongly depending on the figure of chip, the aspect ratio, and the surface roughness of the chute bed.

In resource-starved Japan, sea water resources have attracted attention until now. However, there is no utilization example technology except for a salt and water. It is apprehensive about resource reservation becoming difficult in the near future. Then, it is required to investigate the integrated utilization technology of sea water and brine-concentrate resources in detail. In this report, the following five contents were mainly investigated. (1) Evaluation of concentrated brine produced by desalination process. (2) Re-consideration of the resources which dissolved in sea water. (3) Reappraisal of the production economy of the resources which dissolved in sea water and brine-concentrate and investigation of the high-value-added technology of the chemical compounds originating in the resources which dissolved in sea water. (4) Combination with salt and bitten treatment processes. (5) Proposal of integrated utilization process for sea water and brine-concentrate resources.

There are growing needs for seawater desalination plants all over the world in order to secure stable water resources. Hitachizosen has seawater desalination technologies for three processes (MSF, MED and RO). A significant amount of research and development (R&D) has been carried out in order to constantly improve the technologies and reduce the cost of desalination. This paper describe the features of the processes, overviews of our recent R&D activities and future trends in thermal seawater desalination technologies.

In this paper, the environmentally friendly recycling systems are introduced. The environmentally friendly mineral resource extraction, recycling and environmental technologies that utilize the multi phase flow are classified into different kinds of multiphase. In the mineral resources extraction, grinding, wet separation, flotation, magnetic separation and electrostatic separation are introduced. As for recycling technologies, short time crushing, jigging, heavy dense media separation, sink and float separation using magnetic fluid, fluidized bed, liquid-liquid separation, magnetic separation, triboelectrostatic separation are discussed. Water purification and recycling resources are also listed as the environmental technologies.

Biodiesel as fatty acid methyl esters is an alternative for fossil diesel that is commercially produced by transesterification of oils with methanol under vigorous stirring with an alkaline catalyst. This is because oils and methanol cannot be miscible each other to have two phase reaction system. For further dissemination, waste oils and unused plant oils with toxic substances should be efficiently used as biodiesel. However, the alkali-catalyzed method is not simply applicable to the lower-grade waste oils, because such oils contain not only triglycerides as major component but also free fatty acids as minor component, the latter of which reacts with alkaline catalyst to produce saponified products. Therefore, non-catalytic supercritical methanol methods such as one-step supercritical methanol method (Saka Process) and two-step supercritical methanol method (Saka-Dadan Process) have been developed. By these methods, transesterification of triglycerides and esterification of free fatty acids proceed simultaneously without any catalysts, because the ionic products of methanol is increased in its supercritical condition, while a dielectric constant of methanol is decreased such that triglycerides and methanol can become miscible each other in its supercritical state and its reactivity can be tremendously enhanced. After completion of its reaction, however, fatty acid methyl esters as biodiesel can be phase-separated from methanol in an ordinary condition. Thus, pure biodiesel can be readily achieved. Such attracting behaviors of supercritical fluid technology were discussed to overcome problems in two-phase reaction system in the alkali-catalyzed method.

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is operating a scientific drilling vessel CHIKYU which is an ultra-deep water drillship. The CHIKYU is operated under an international science program, the Integrated Ocean Drilling Program (IODP), and her primary mission is to drill the deep sea floor and to explore the deep earth for science research. She is sometimes engaged in the exploration of natural resources. In this paper, outline of the CHIKYU and drilling techniques for deep ocean floor are described.

On March 11 in 2011, a very big earthquake occurred in Tohoku district in Japan. Huge tsunami was generated by this earthquake and the coastal area of Tohoku district had catastrophic damage. Many houses were destroyed by tsunami and huge amount of rubble was generated. At the same time, a large amount of tsunami sludge deposited on land. We carried out the actual construction to create the artificial ground by recycling tsunami sludge. The physical properties of tsunami sludge were different if the places were different. However, it was confirmed through the actual construction that creation of artificial ground was possible even if the properties of tsunami sludge were different.

A paradigm for river management was shifted after a legal reform of the river act in 1997, where preservation and mitigation of natural environment became an essential engineering issue in addition to flood control and water use. After then, multi-phase flow researches in river engineering have tremendously changed their direction from hydrodynamics to ecohydraulics that is an integrated engineering disciplines consisting of hydraulics, ecology and biochemistry. Hydraulic engineers are required to develop engineering management tools of river ecosystem that is one of most critical issues for our sustainable life in the next era. There is a wide range of hydraulic engineering disciplines that are closely related multi-phase flows found in issues from disaster mitigation to preservation of nature. In this article, hydraulic engineering researches in the last decades are briefly overviewed focusing on multi-phase flows in a river system.

Slurry and paste (highly concentrated slurry) transportation in mining industry are　overviewed. In the case of slurry, three types of trends are noticeable. Firstly, long and large capacity pipelines have been constructed to transport concentrates of various ores. Secondly, to protect pipelines from abrasion and corrosion, newly constructed pipelines are lined with high-density polyethylene (HDPE). Thirdly, pipelines from mines at high elevation over 4,000 m have been constructed. These pipelines are controlled by state of art technologies to prevent slack flow and over-pressure.  Paste technology in mining industry is getting popular all over the world. At early stage of the paste technology, mining engineers paid attention to use this technology for back filling inside mines. Recently this technology is applied to surface disposal of paste without using conventional dams or ponds

In order to synthesize methane hydrate at high formation rate, finebubbles were utilized. The finebubble generator consisted of a liquid pump and a special line mixer. Finebubbles shortened an induction time of hydrate formation because the nucleation of hydrate was enhanced. With increasing liquid circulation flow rate, the induction time of hydrate formation shortened and the formation rate of hydrate increased because the number of finebubbles increased. The induced air flotation of oil droplets was conducted by the finebubble generator for oil-in-water emulsion separation. Compared with millibubbles, the dispersion of finebubbles effectively separated oil droplets. This was because finebubbles had high efficiency of collision with droplets and it was difficult to detach droplets because of the low rising velocity of finebubbles. The oil separation was largely enhanced at the solution pH below 4.5 because the electrostatic attraction between oil droplets and finebubbles was generated.

Subsea minerals, such as seafloor massive sulfides, rare earth elements in deep-sea mud, are found in deep sea within the exclusive economic zone of Japan. However, the development of subsea resources has not reached the commercialization stage because many technical issues still need to be addressed. Then, efforts for solving these issues are conducted in Japan and other countries. Air-lift pumping systems are one of the promising methods for subsea mineral resource productions. In developing air-lift pumping systems, one of the technical issues is flow assurance for gas-liquid-solid three-phase flow. We reviewed the correlations of volume fractions and frictional pressure drops in gas-liquid and liquid-solid two-phase flows and proposed correlations for three-phase flows. We carried out some experiments of air-lift pumping systems and obtained data of volume fractions of each phase and frictional pressure drops. To validate the proposed correlation, we compared calculated results by the proposed correlations with experimental data. The comparison suggested that the volume fraction of gas-phase and the frictional pressure drops could be calculated by the proposed correlations. Meanwhile, deviations between experimental data of solid-phase and calculated results of that was large and new methods were needed for calculated them.

In this paper, the study on the performance of a 200 m airlift pump for water and highly-viscous shear-thinning slurry is introduced, mainly following the published paper [1]. The experiment was conducted using the facility in Advanced Institute of Science and Technology, Tsukuba, which had been used for the project of polymetallic nodule about 30 years ago. Here, in the present study, we investigate the airlift performance for the shear-thinning slurry which imitates the rare-earth mud water in the deep ocean. The experimental results showed that the airlift pump can work properly not only for water but also highly viscous slurry. It was confirmed that actual airlift performance obtained with the experiments does not show the reduction of the lifted liquid with increasing the gas flow rate, which the numerical results show the some deviation of the predicted value for high gas flow rate.

Air-lift two-phase and particulate three-phase flow in a vertical pipe has been measured by ultrasound with the aim of revealing the transient dynamics of the air-lift performance. Changing the gas flow rate and mass loading of solid particles, we measured the void fraction and liquid flow rate in the slug-flow regime at 55 Hz in sampling rate. We found that mixing the liquid phase with solid particles reduced the mean axial length of the bubbles and the void fraction was reduced because of the long slug destabilized by the particles.

A system for recovery of methane hydrate from the deep ocean floor has not been established. As one possible recovery system, a gas-lift system was investigated. Experiments were performed with a gas-lift system of 5 m height and 100 mm in diameter to determine the relationship between injected gas quantity and pumped water quantity. Vertical flow in the gas-lift pipe was calculated with a compressible one-dimensional two-fluid model to analyze flow in the recovery pipe of methane hydrate from the deep ocean floor. Basic equations were mass conservation equations and momentum conservation equations of each phase, the relation of volume fractions and the state equation of the gas phase. The calculation showed that optimal gas injection depths exist. Thus, the gas-lift system can be economically effective the recovery of methane hydrate from the deep ocean floor.

Methane hydrate is expected as domestic energy resources in near future in Japan. Especially the shallow-type methane hydrate and the associated methane plume are regarded as sustainable energy resources. In this paper, the investigation of the methane hydrate particle motion in the methane is presented. A quantitative analysis of the motions of the ascending methane hydrate particles seeping from the seafloor and reproduced by the numerical simulation is performed by the two-dimensional motion analysis technique and the behavior is discussed in detail.

Traditionally, it has been challenging to observe phenomena inside porous media due to their optical opacity, and the description has relied on the volume-averaged Darcy law. Recent advances in measurement techniques, such as X-ray computer tomography (CT) allow us to observe the pore structure of porous media and the multiphase flow occurring in the interior at the pore scale. In this paper, the author introduces some of the phenomena revealed by pore-scale measurements, focusing on our research on carbon dioxide capture and storage (CCS) and enhance oil recovery (EOR). Numerical simulation, which plays a leading role in digital locking technology, is omitted, but the complementary use of measurement and simulation is expected to accelerate our understanding of the phenomena. Cross-scale approaches are currently being vigorously pursued, ranging from phenomenological descriptions of Darcy law at the macroscopic scale to Navier-Stokes equation-based descriptions on the pore scale.