Temperature dependence on reaction of CaCO_3 and SO_2 in O_2/CO_2 coal combustion

The temperature dependence on the reaction of desulfurization reagent CaCO3 and SO2 in O2/CO2 coal combustion was investigated by thermogravimetric analysis,X-ray diffraction measurement and pore structure analysis. The results show that the conversion of the reaction of CaCO3 and SO2 in air is higher at 500-1 100 ℃ and lower at 1 200 ℃ compared with that in O2/CO2 atmosphere. The conversion can be increased by increasing the concentration of SO2,which causes the inhibition of CaSO4 decomposition and shifting of the reaction equilibrium toward the products. XRD analysis of the product shows that the reaction mechanism of CaCO3 and SO2 differs with temperature in O2/CO2 atmosphere,i.e. CaCO3 directly reacts with SO2 at 500 ℃ and CaO from CaCO3 decomposition reacts with SO2 at 1 000 ℃. The pore analysis of the products indicates that the maximum specific surface area of the products accounts for the highest conversion at 1 100 ℃ in O2/CO2 atmosphere. The results reveal that the effect of the atmosphere on the conversion is temperature dependence.

Influence of constricted air distribution on NO_x emissions in pulverized coal combustion boiler

This paper reports a field testing of full scale PCC (Pulverized Coal Combustion) boiler study into the influence of constricted air distribution on NO x emissions at unit 3 (125 MW power units, 420 t/h boiler) of Guixi power station, Jiangxi and puts forward the methods to decrease NO x emissions and the principle of boiler operation and regulation through analyzing NO x emissions state under real running condition. Based on boiler constricted air distribution, the experiment mainly tested the influence of primary air, excessive air, boiler load and milling sets (tertiary air) on NO x emissions and found its influence characteristics. A degraded bituminous coal is simply adopted to avoid the test results from other factors.

Experimental research on mercury emission from one-dimensional combustion test facility

The research of mercury release from coal combustion and mercury speciation in flue gas was conducted in a one-dimensional combustion test facility. The experimental results indicated that combustion temperature was the primary factor in affecting mercury vaporization and release. Experimental measurements showed high mercury levels in the particulate phase. Hg(S) is enriched in fly ash and dispersed in bottom ash. Hg(B) content decreases and the Hg^2+(g) content increases with higher furnace temperature. At 1 100℃, the levels of Hg2+(g) are 17%-48% for limited chemical kinetics .The mercury equilibrium in the flue-gas is frozen below some temperature.

Inventory of CO2 emissions driven by energy consumption in Hubei Province： a time-series energy input-output analysis

Based on an input-output analysis, this paper compiles inventories of fuel-related CO2 emissions of Hubei economy in the years of 2002, 2005, and 2007. Results show that calculated total direct CO2 emissions rose from 114,462.69 kt （2002） to 196,650.31 kt （2005）, reaching 210,419.93 kt in 2007, with an average 22.50% rate of increase. Raw coal was the dominant source of the direct emissions throughout the three years. The sector of Electric Power, Heat Production, and Supply was the main direct emissions contributor, with the largest intensities observed from 2002 （1192.97 g/CNY） to 2007 （1739.15 g/ CNY）. From the industrial perspective, the secondary industry, which is characterized as manufacture of finished products, was still the pillar of the Hubei economy during this period concerned, contributing more than 80% of the total direct emissions. As a net exporter of embodied CO2 emissions in 2002 and 2007, Hubei reported net-exported emissions of 4109.00 kt and 17,871.77 kt respectively; however, Hubei was once a net importer of CO2 emissions in 2005 （2511.93 kt）. The CO2 emissions embodied in export and fixed capital formation had the two leading fractions of emissions embodied in the final use. The corresponding countermeasures, such as promoting renew- able and clean energy and properly reducing the exports of low value added and carbon-intensive products are suggestions for reducing CO2 emissions in Hubei.

Numerical Validation of Brenner’s Hydrodynamic Model by Force Driven Poiseuille Flow

Recently Brenner[Physica A 349,60(2005)]proposed a modified NavierStokes set of equations.Based on some theoretical arguments and some limited experiments,the model is expected to be able to describe flows with a finite Knudsen number.In this work,we apply this model to the plane Poiseuille flow driven by a force,and compare the results with the Direct Simulation Monte Carlo(DSMC)measurements.It is found that Brenner’s model is inadequate for flows with a finite Knudsen number.

MULTIPLE TEMPERATURE GAS DYNAMIC EQUATIONS FOR NON-EQUILIBRIUM FLOWS

In an early approach, a kinetic model with multiple translational temperature [K. Xu, H. Liu and J. Jiang, Phys. Fluids 19, 016101 （2007）] to simulate non-equilibrium flows was proposed. In this paper, instead of using three temperatures in the x, y and z-directions, we define the translational temperature as a second-order symmetric tensor. Under the new framework, the differences between the temperature tensor and the pressure tensor will be explicitly pointed out. Based on a multiple stage BGK-type collision model and the Chapman-Enskog expansion, the corresponding macroscopic gas dynamics equations in three-dimensional space will be derived. The zeroth-order expansion gives 10 moment closure equations similar to that of Levermore [C.D. Levermore, J. Stat. Phys 83, pp.1021 （1996）]. The derived gas dynamic equations can be considered as a regularization of the 10 moments equations in the first-order expansion. The new gas dynamic equations have the same structure as the Navier-Stokes equations, but the stress-strain relationship in the Navier-Stokes equations is replaced by an algebraic equation with temperature differences. At the same time, the heat flux, which is absent in Levermore＇s 10 moment closure, is recovered. As a result, both the viscous and the heat conduction terms are unified under a single anisotropic temperature concept. In the continuum flow regime, the new gas dynamic equations automatically recover the standard Navier-Stokes equations. Our gas dynamic equations are natural extensions of the Navier-Stokes equations to the near continuum flow regime and can be used for microfiow computations. Two examples, the force-driven Poiseuille flow and the Couette flow in the transition flow regime, are used to validate the model. Both analytical and numerical results are presented. Theoretically, the Boltzmann equation can be also applied to the current multiple stage gas evolution model to derive generalized macroscopic governing equations in the near continuum flow regime. Instead of using Maxwellian as an expansion point in the Chapman-Enskog method, the multiple temperature Gaussian can be used as an expansion point as well.

Lattice Boltzmann Method:A Powerful Numerical Tool for Fluid Dynamics and Beyond

Computational Fluid Dynamics(CFD)is playing a more and more important role in both fundamental researches of fluid dynamics and practical applications.Usually CFD methods are developed to solve Navier-Stokes(N-S)equations and their simplified forms.The CFD solvers often involve numerical discretization of partial differential equations and solution of resultant ordinary differential equations or algebraic equations.The process is quite tedious,and may encounter stability and convergence problems.In addition,since N-S equations are valid for continuum flows,the conventional CFD solvers may have difficulties for their applications to the micro flow,rarefied gas flow,and other non-continuum fluid systems.

Lattice Boltzmann Method for Thermocapillary Flows

In this paper,we apply a recently proposed thermal axisymmetric lattice Boltzmann model to the thermocapillary driven flow in a cylindrical container.The temperature profiles and isothermal lines at the free surface with Prandtl(Pr)number fixed at 0.01 and Marangoni(Ma)number varying from 10 to 500 are measured and compared with the previous numerical results.In addition,we also give the numerical results for different Ma numbers at Pr=1.0.It is shown that present results greed well with those reported in previous studies.