The Pressurized Fluidized Bed Combustion (PFBC) combined cycle has become a subject of world attention in terms of better plant operation, improved plant efficiency, lower flue gas emission and fuel flexibility. The 71MWe PFBC combined cycle power plant at Wakamatsu, Electric Power Development Company (EPDC) (funded by Ministry of International Trade and Industry (MITI) and Center of Coal Utilization Japan (CCUJ)) achieved approximately 11, 500h accumulative operation while extremely low dust emission (<0.2mg/m3N) was succeeded by a hot gas cleaning system combining cyclones and full scale Ceramic Tube Filter (CTF). The gas turbine installed at the downstream of the CTF was thus completely protected from the possible severe erosion problem with fly ash. Two different configurations of cyclones and CTF were examined in Phases 1 (Conventional PFBC) and Phase2 (Ash Re-circulating PFBC) where several coals, petroleum coke, and two kinds of domestic limestone as absorbent were tested successfully. CTF is one of key technology for hot gas cleaning. Its major items to be concerned such as the reliability of filter element and dust seal mechanism, the pressure drop performance, the optimization for reverse cleaning conditions and system maintenance-ability are summarized in this paper. Since it's most concerned how long the filter tubes made from Cordierite material can really survive in the commercial use, its life time is confirmed at least several years, based on the physical/chemical analysis of the used filter (approximately 8, 000h) and the accelerated corrosion test with potassium and/or sulfur dioxide gas flow. Increased resistance of gas passage at the seal portion improved the seal between ceramic filter element and metallic parts, avoiding dust leakage. The on-site inspection tool for the filter elements to find any damage suffered and the watching system of plant stability during operation were developed to avoid the catastrophic filter breakage. In conclusion, CTF was confirmed to be applicable for the commercial use. The future perspective and the application of CTF system are discussed to respond the strong demands for the better environment and the higher efficiency plant using coal.
Solid particles, accumulated or deposited in the reactors, hot-highpressure separator (HHPS) and downstream transfer lines of the letdown valve (LDV) were observed after long continuous operation of a 150t/d Pilot Plant of Coal Liquefaction at Kashima. During the operation, two types of solid particles were produced, i.e., particles with cores, and particles without cores. The average size of the former particles was 10-200μm, while that of the latter particles was 1-80μm. The size of the core, included in the larger particles, was as equivalent in size to that of the smaller particles without cores. The cores, as well as the particles without cores, were largely composed of SiO2, with lesser amounts of FeS and CaCO3. These materials were probably formed from coal minerals and catalyst. It is to note that the particles of 10-100μm in the reactors were missed after a long operation. These results suggested that the fine particles are produced in the reac-tor, flow out from the reactor before their size reach to 10-100μm, or increase their size above 100μm to be accumulated or deposited within the reactor. The mineral particles found in the HHPS and downstream transfer lines of LDV were basically same to those found in the reactor, those of high gravity being deposited on the wall together with heavy oil to be coagulated solid.
The condensation products of glucose and 15N-glycine, and xylose and 15N-ammonium sulfate were prepared in order to clarify the origin and the formation of nitrogen in coal by using solid-state 15N NMR. The mixtures were heat-treated in water at 180°C for 50h, and the insoluble products were compressed (100kgf/cm3) at 300 or 400°C for 25 h in He atmosphere (50kgf/cm2). The obtained solid materials were crushed and washed by tetrahydrofuran. Solid-state 13C NMR spectra were measured for the condensation products, and after the thermal decomposition at 180°C, glucose or xylose structures were disappered and the spectra were similar to those of coal, indicating the structural similarities between the condensates and coal. In the case of the mixture of glucose and 15N-glycine, glucose underwent condensation reaction, and 15N-glycine was incorporated in the condensation sturucture during the process of glucose condensation. Nitrogen became incorporated to the condensates mainly in the form of amide at first, and later converted to the form of pyrrole and pyridine by cyclization and aromatization. The process also occurred in the case of the mixture of xylose and 15N-ammonium sulfate. It was considered that the changes of nitrogen functionality of the condensation products in this study are similar to that of coal during coalification.
Photo-evolution of hydrogen from water using tris (2, 2'-bipyridine) ruthenium (II) complex, methylviologen, disodium dihydrogenethylene-N, N, N', N'- tetraacetate and colloidal platinum was examined for long time over 14h. The evolution of hydrogen terminated at about 8 h in spite of presence of reactants. When solid ethylene-N, N, N', N'-tetraacetic acid was added to the system, the evolution of hydrogen proceeded over 14 h; added solid ethylene-N, N, N', N'-tetraacetic acid remained solid and the pH of the reaction solution was below 4.5 throughout the reaction.