Control of particle circulation rate in circulating fluidized bed by a pulsed gas flow

As a coal-fired power generation technology for further improvement of power generation efficiency of coal-fired power generation, exergy regeneration type coal gasification power generation technology (1), a triple-bed circulating fluidized bed (2), has been proposed. The authors analyzed the flow characteristics of the triple-bed circulating fluidized bed, it has the flow characteristics of the riser and downer perform the proposed approach to representation by the equivalent circuit model. The equivalent circuit model of the riser and downer are shown in Figure 1. This equivalent circuit has the nature of the low-pass filter. A combination of the low-pass filter and the pulse voltage is used as a switching power supply. Then, we applied that the pulsed gas supply to the riser combined with a low-pass filter characteristics to control the particle circulation rate of the triple-bed circulating fluidized bed. Figure 2 shows the input output characteristics of the equivalent circuit of the riser/downer inputting a pulse voltage. We used an electric circuit simulator SPICE to calculation of circuit behavior. Circuit constant is to use the value of the reference 3, the input pulse height is set to 80V. When the input pulse width is changed, the output current is changed depending on the pulse width. Moreover, when changing the density of the pulse, the output current is changing depending on the pulse density. This result by giving a pulsed gas supply to the riser, it shows the possibility controlling the particle circulation rate of the triple-bed circulating fluidized bed. Please click Additional Files below to see the full abstract

Investigation of agglomerates growth mechanism for thermal seawater desalination

Desalination technology has been paid large attention because water demand has been increasing due to the industrial development and high growth rate of population. To develop a novel desalination process with high energy efficiency and with high recovery ratio, a self-heat recuperative seawater desalination process using a fluidized-bed evaporator has been proposed (1). The fluidized-bed evaporator was employed to prevent scale deposition on the heat transfer surface during seawater evaporation. The seawater evaporation experiment using a lab-scale fluidized bed showed that the proposed evaporator prevents scale deposition on the heat transfer surface (2). However, it was also found that the seawater feed into the bed causes agglomeration of fluidized particles, which has the possibility to cause defluidization. In this research, seawater evaporation experiments using the lab-scale fluidized-bed evaporator were conducted and the influence of operating conditions such as fluidizing gas velocity, seawater feed rate and bed temperature on the agglomeration behavior of fluidized particles was examined. Furthermore, the mechanism of agglomerates growth was investigated and the optimal operating conditions of the fluidized bed for thermal desalination were examined. REFERENCES H. Mizuno, Y. Kansha, M. Ishizuka and A. Tsutsumi. A Novel Thermal Desalination Process Using Fluidized Bed. Chem. Eng. Trans., 39: 181-186, 2014 H. Mizuno, Y. Kansha, M. Ishizuka and A. Tsutsumi. Agglomeration behavior in fluidized-bed evaporator for thermal seawater desalination. Appl. Therm. Eng., 89: 1096-1103, 2015

DESIGN AND TEST PLAN OF THE SUPERCRITICAL CO 2 COMPRESSOR TEST LOOP

ABSTRACT Supercritical carbon dioxide (CO 2 ) gas turbine systems can generate power at a high cycle thermal efficiency, even at modest temperatures of 500-550°C. That high thermal efficiency is attributed to a markedly reduced compressor work in the vicinity of critical point. In addition, the reaction between sodium (Na) and CO 2 is milder than that between H 2 O and Na. Consequently, a more reliable and economically advantageous power generation system can be created by coupling with a Na-cooled fast breeder reactor. In a supercritical CO 2 turbine system, a partial cooling cycle is employed to compensate a difference in heat capacity for the high-temperature -low-pressure side and low-temperaturehigh-pressure side of the recuperators to achieve high cycle thermal efficiency. In our previous work, a conceptual design of the system was produced for conditions of reactor thermal power of 600 MW, turbine inlet condition of 20 MPa/527°C, recuperators 1 and 2 effectiveness of 98%/95%, Intermediate Heat Exchanger (IHX) pressure loss of 8.65%, a turbine adiabatic efficiency of 93%, and a compressor adiabatic efficiency of 88%. Results revealed that high cycle thermal efficiency of 43% can be achieved. In this cycle, three different compressors, i.e., a low-pressure compressor, a high-pressure compressor, and a bypass compressor are included. In the compressor regime, the values of properties such as specific heat and density vary sharply and nonlinearly, dependent upon the pressure and temperature. Therefore, the influences of such property changes on compressor design should be clarified. To obtain experimental data for the compressor performance in the field near the critical point, a supercritical CO 2 compressor test project was started at the Tokyo Institute of Technology on June 2007 with funding from MEXT, Japan. In this project, a small centrifugal CO 2 compressor will be fabricated and tested

Full QCD hadron spectroscopy with two flavors of dynamical Kogut-Susskind quarks on the lattice

A full lattice QCD simulation is carried out with two flavors of Kogut-Susskind staggered dynamical quarks using lattices of a size ranging from 44 to 204 at the gauge coupling constant β=6/g2=5.7 with the quark mass of mq=0.01 and 0.02 in lattice units. Primary emphasis is given to the study of finite-lattice-size effects in the hadron mass spectrum. It is found that hadron masses suffer from substantial finite-size effects even for a lattice size of the order of 2 fm, showing the importance of a quantitative control of the effect for a comparison with the experimental spectrum at the accuracy of a few percent level. The finite-size correction is found to be well described by a power law in the lattice size, rather than an exponential form predicted by analytic formulas derived for point particles. It is suggested that the effect arises from the size of hadrons squeezed on a finite lattice. Finite-size effects on the realization of chiral symmetry are also studied. The behavior of the pion mass, the chiral condensate, and the mass splitting between parity partners all support a spontaneous breakdown of chiral symmetry for a large lattice size. Prediction from chiral Lagrangians on the size dependence of the chiral condensate does not describe the simulation results well, however, at least for the quark mass employed for the present study. Calculation of the pion decay constant with various relations derived from current algebra and partial conservation of axial-vector current gives fπ=94(8)-105(9) MeV, with a method-dependent uncertainty contained within 10%.0 An examination is also made of the question of the dependence of hadron masses on hadron operators. Meson masses are basically operator independent, while baryon masses exhibit some operator dependence, necessitating further studies to resolve systematic uncertainties of this origin in the determination of the hadron mass spectrum

High-Flux Triple Bed Circulating Fluidized Bed (TBCFB) Gasifier for Exergy Recuperative IGCC/IGFC

The flow behavior of silica sand, of average particle size 128 μm, was investigated using a large-scale triple-bed combined circulating fluidized bed (TBCFB) cold model, which was composed of a 0.1 m I.D. ×16.6 m tall riser, a solids distributor, a 0.1m I.D. × 6.5 m long downer, a gas-solids separator, a 0.75 m × 0.27 m × 3.4 m bubbling fluidized bed and a 0.158 m I.D. × 5.0 m tall gas-sealing bed (GSB) with a high solids mass flux. The main focus of this study is to determine effect of riser secondary air injection on solids mass flux (Gs) and solid holdup. Gs slightly increased by secondary air injection when the riser gas velocity (Ugr) was less than 10 m/s. This was caused by the increase in the pressure difference between the GSB and the riser. Secondary air injection had little influence on the solid holdup in the riser. The mixing between silica sand and coal particles was investigated for two different coal feeding arrangements by coupling Computational Fluid Dynamics (CFD) with the Discrete Element Method (DEM). The results show a tangential arrangement provided better mixing than a normal arrangement except near the entrance

FLOW BEHAVIORS IN A HIGH SOLID FLUX CIRCULATING FLUIDIZED BED COMPOSED OF A RISER, A DOWNER AND A BUBBLING FLUIDIZED BED

A circulating fluidized bed coal gasifier cold model which consists of an acrylic riser, a downer, and a bubbling fluidized bed were set up. Flow behaviors were investigated using silica sand with the solid mass flux up to 336 kg/m2•s. The effects of the solid inventory and the seals between the three reaction zones on the solid mass flux were investigated and discussed

Light hadron spectroscopy with two flavors of O(a) improved dynamical quarks

We report on our study of light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks. Simulations are made with the plaquette gauge action and the non-perturbatively $O(a)$ improved Wilson quark action. We simulate 5 sea qaurk masses corresponding to $m_{PS}/m_{V} \simeq 0.8$--0.6 at $\beta=5.2$ on $12^3 \times 48$, $16^3 \times 48$ and $20^3 \times 48$ lattices. A comparison with previous calculations in quenched QCD indicates sea quark effects in meson and quark masses

K+→π+π0 decay amplitude with the Wilson quark action in quenched lattice QCD

We present a calculation for the K+→π+π0 decay amplitude using a quenched simulation of lattice QCD with the Wilson quark action at β=6/g2=6.1. The decay amplitude is extracted from the ratio, the K→ππ three-point function divided by either K and π meson two-point functions or K meson two-point function and I=2 ππ four-point function; the two different methods yield consistent results. Finite size effects are examined with calculations made on 243×64 and 323×64 lattices, and are shown that they are explained by one-loop effects of chiral perturbation theory. The lattice amplitude is converted to the continuum value by employing a one-loop calculation of chiral perturbation theory, yielding a value in agreement with experiment if extrapolated to the chiral limit. We also report on the K meson B parameter BK obtained from the K+→π+π0 amplitude using chiral perturbation theory

B meson decay constant from quenched Lattice QCD

A lattice QCD calculation of the B meson decay constant is presented. In order to investigate the scaling violation associated with the heavy quark, parallel simulations are carried out employing both Wilson and the O(a)-improved clover actions for the heavy quark. The discretization errors due to the large b quark mass are estimated in a systematic way with the aid of the non-relativistic interpretation approach of El-Khadra, Kronfeld and Mackenzie. As our best value from the quenched simulations at beta=5.9,6.1 and 6.3 we obtain fB=163±16 MeV and fBs=175±18 MeV in the continuum limit where the error includes both statistical and systematic uncertainties

K+ → π+π0 decay amplitude in quenched lattice QCD

A new study is reported of a lattice QCD calculation of the K+ → π+π0 decay amplitude with the Wilson quark action in the quenched approximation at β = 6.1. The amplitude is extracted from the K → ππ Green function, and a conversion to the continuum value is made employing a recent one-loop calculation of chiral perturbation theory. The result is consistent with the experimental value if extrapolated to the chiral limit