Tatsushi Matsuyama

Maximum organic loading rate for the single-stage wet anaerobic digestion of food waste.

Anaerobic digestion of food waste was conducted at high OLR from 3.7 to 12.9 kg-VS m(-3) day(-1) for 225 days. Periods without organic loading were arranged between the each loading period. Stable operation at an OLR of 9.2 kg-VS (15.0 kg-COD) m(-3) day(-1) was achieved with a high VS reduction (91.8%) and high methane yield (455 mL g-VS-1). The cell density increased in the periods without organic loading, and reached to 10.9×10(10) cells mL(-1) on day 187, which was around 15 times higher than that of the seed sludge. There was a significant correlation between OLR and saturated TSS in the sludge (y=17.3e(0.1679×), r(2)=0.996, P<0.05). A theoretical maximum OLR of 10.5 kg-VS (17.0 kg-COD) m(-3) day(-1) was obtained for mesophilic single-stage wet anaerobic digestion that is able to maintain a stable operation with high methane yield and VS reduction.

Charge relaxation process dominates contact charging of a particle in atmospheric conditions

A new model is proposed for a mechanism dominating the charge generated on a particle due to impact or contact with metal plate. In this model, the impact/contact charging of a particle is determined as the remaining charge by the charge relaxation process due to gaseous discharge in atmospheric conditions; here, some difficulties of the simple condenser model are avoided. The model prediction is in good agreement with the `equilibrium charges` given as the result of impact charging experiments. Furthermore, the impact charging experiments conducted in Ar gas indicated that the impact charging characteristics changed corresponding to the breakdown limit potential of the environmental gas; this was also predicted quantitatively by the model. As a result of the proposal of this new model, hereafter in the case of treating charge generating phenomena due to impact or contact, in atmospheric conditions at least, consideration of the charge relaxation process due to gaseous discharge should be essential.

The effect of the labile organic fraction in food waste and the substrate/inoculum ratio on anaerobic digestion for a reliable methane yield.

Influence of the labile organic fraction (LOF) on anaerobic digestion of food waste was investigated in different S/I ratio of 0.33, 0.5, 1.0, 2.0 and 4.0g-VSsubstrate/g-VSinoculum. Two types of substrate, standard food waste (Substrate 1) and standard food waste with the supernatant (containing LOF) removed (Substrate 2) were used. Highest methane yield of 435ml-CH4g-VS(-1) in Substrate 1 was observed in the lowest S/I ratio, while the methane yield of the other S/I ratios were 38-73% lower than the highest yield due to acidification. The methane yields in Substrate 2 were relatively stable in all S/I conditions, although the maximum methane yield was low compared with Substrate 1. These results showed that LOF in food waste causes acidification, but also contributes to high methane yields, suggesting that low S/I ratio (<0.33) is required to obtain a reliable methane yield from food waste compared to other organic substrates.

Impact charging experiments with single particles of hundred micrometre size

Abstract This paper reports the results of an ongoing program, which investigates the electrostatic charge generated when a particle impacts and rebounds from a metal plate. Previous studies were conducted with particles, which were several millimetres in size. From those experiments, a theory of ‘charge relaxation’ was developed which predicts the equilibrium charge, which a particle will acquire after multiple impacts. In this paper, we report the development of a new apparatus, which is more sensitive by several decades. With this equipment, the experiments could be repeated with particles as small as 100 μm. The results show that the charge relaxation theory is still relevant in this range. However, it is necessary to modify this theory, both for the larger and the smaller particles, to account for the distribution of the charge on the surface of the particle.

Characterizing the electrostatic charging of polymer particles by impact charging experiments

Abstract Impact charging experiments were systematically conducted using four kinds of polymers for impacting particles and three metal targets with different work functions in all of their combinations. The equilibrium charges were independent of the work function of the metal target and were almost constant for each polymer. Discussion of the results of this experiment suggested that the charge relaxation in the particles separating process determines the impact charge if this impact charging is generated under atmospheric conditions. One important reason for studying this charge relaxation process is to understand the particle charging mechanism. Furthermore, these discussions and experimental results suggested that the characteristic which decides the amount of charge generation, in charge generation in the dry powder processes etc., is the dielectric constant of the polymer material of which the particle consists.

Immobilization of glucoamylase on ceramic membrane surfaces modified with a new method of treatment utilizing SPCP–CVD

Glucoamylase, as a model enzyme, was immobilized on a ceramic membrane modified by surface corona discharge induced plasma chemical process-chemical vapor deposition (SPCP-CVD). Characterizations of the immobilized enzyme were then discussed. Three kinds of ceramic membranes with different amounts of amino groups on the surface were prepared utilizing the SPCP-CVD method. Each with 1-time, 3-times and 5-times surface modification treatments and used for supports in glucoamylase immobilization. The amount of immobilized glucoamylase increased with the increase in the number of surface modification treatments and saturated to a certain maximum value estimated by a two-dimensional random packing. The operational stability of the immobilized glucoamylase also increased with the increase in the number of the surface treatment. It was almost the same as the conventional method, while the activity of immobilized enzyme was higher. The results indicated the possibility of designing the performance of the immobilized enzyme by controlling the amount of amino groups. The above results showed that the completely new surface modification method using SPCP was effective in modifying ceramic membranes for enzyme immobilization.

Electrostatic field and force calculation for a chain of identical dielectric spheres aligned parallel to uniformly applied electric field

Abstract We apply the re-expansion method proposed by Washizu to a linear particle chain aligned in the direction of a uniform electric field. The calculated results show that the potential distribution around the particles becomes very complicated and the electric field is highly concentrated near the contact points of particles. The pearl-chain forming force rapidly increases with increasing number of particles and reaches a saturation value for chains consisting of some tens of particles. The force at a contact point in a particle chain is reduced near both the ends of the chain but is still much stronger than the interaction force of the two particles. The present method can be extended to cases of coated particles. One example of the application is a new model for the surface roughness of electro-rheological (ER) particles. A layered particle model, in which the surface roughness is replaced with an equivalent surface layer, provides a more reasonable method for the force calculation, because the existing gap model is too sensitive to the fictitious interstice representing the roughness. Another example is the effect of surface coating to reduce the electric field at the contact points. Such a coating will be preferable for ER particles to prevent electrical breakdown in the fluid.

Transformation of Diffraction Pattern due to Ellipsoids into Equivalent Diameter Distribution for Spheres

If a particle is not spherical, the Fraunhofer diffraction pattern is not circular, however the particle size distribution obtained from conventional particle sizer are made under the assumption of spherical particle. It is, therefore, necessary to discuss or interpret the relationship between the obtained equivalent diameter and the diffraction pattern. In this paper, this transformation problem was discussed principally for the case of ellipsoid particle. A relationship between an original size of ellipsoid and obtained equivalent particle size distribution was given in an analytical expression. The equivalent particle size clearly had double peaks in the size corresponding both to the minor and major diameter of the original ellipsoid. On the other hand, if the original particle had its own size distribution, the double peak was eliminated due to the effect of this original size distribution. In the case of random orientation of the ellipsoid in the sensing zone, the double peak was also eliminated and a rather clear single peak appeared at the minor diameter of the original ellipsoid.

Electrification of single polymer particles by successive impacts with metal targets

Electrification of single polymer particles by successive impacts with separated metal targets was measured separately for each impact. From these experiments, the process of the electrification of the polymer particle due to successive impacts was traced. At the second impact, the initial charge of the particle becomes nonuniform because of the presence of the impact charge generated by the first impact. In order to account for the contribution of this nonuniform initial charge on the impact charging, a new model was proposed in which the electrostatic field around the particle was considered. Our experimental results were discussed based on the new model.

Shape distinction of particulate materials by laser diffraction pattern analysis

Abstract A pattern of a diffraction image depends on the particle shape, while the size of the pattern depends on the sectional area of the particle. In this work, the method to extract differences from the diffraction patterns due to different shapes of non-spherical particles was studied conceptually. In this respect, a radial segment (wedge) photo-detector was assumed as a detector. Diffraction patterns and intensity patterns detected by the radial segment detector were calculated for many kinds of two-dimensional shapes, corresponding to the projections of particles, as a circle, ellipses, triangles, quadrangles, other anonymous shapes, also shapes extracted from real phytoplanktons. From these detected light intensity patterns, we extracted (or define) two indexes: “circular index” and “peak number.” It was shown that various shapes can be distinguished by means of two-dimensional mapping with these parameters. In addition, an applicability of a concentric detector was examined to estimate the particle size when the particle is non-spherical but is a single particle in the measurement. As a result, it was found that the circle equivalent diameter determined with usual scheme agreed well with the sectional area equivalent diameter of the original particle even in any cases of non-spherical samples. From these results, it was shown that the particle size and shape in wide range can be distinguished from the three-dimensional mapping with “circular index”, “peak number” and “particle size”.