Weiguo Pan

The Effect of Heat Decomposition Temperature on the Dissolution Rate of Magnesium-based Materials for Wet Flue Gas Desulfurization

Magnesium hydrate is the absorbent in magnesia scrubbing wet flue gas desulfurization. Its dissolution rate has a great impact on the performance of SO2 removal. Further, magnesia is the heat decomposition product of magnesite. The effect of magnesite heat decomposition temperature on the dissolution rate of magnesium hydrate is investigated in this study. As can be seen from the experimental results, magnesium hydrate dissolution rate increased with increasing heat decomposition temperature up to 700°C and then decreased with the increase of heat decomposition temperature. This is caused by the change of magnesite heat decomposition mechanism at a different heat decomposition temperature.

A Thermodynamic Study of Simultaneous Removal of SO2 and NO by a KMnO4/Ammonia Solution

Molar reaction Gibbs function change, molar reaction enthalpy change, equilibrium constant, and the equilibrium partial pressure of SO2 and NO for the reaction of simultaneous removal of SO2 and NO by using aqueous KMnO4/ammonia solution are calculated based on the principle of chemical thermodynamics. The results show that simultaneous removal of SO2 and NO by using KMnO4/ ammonia solution is available.

Neural network construction and its predication for coal-blending at coal combustion power station

With the coal consumption increasing gradually, coal blending is becoming a routine work in power stations. Due to the fluctuation of the coal quality, coal blending is in fact an optimization problem under uncertain conditions, so that it is difficult to solve with the traditional linear programming model. On the other hand, BP neural network, a nonlinear optimization tool, has been successfully applied to coal blending. In this paper, the prediction effects of different BP neural network model were analyzed and the main factors affecting the prediction effects were also studied. These factors included network structure, learning sample quantities, hidden nodes, learning accuracy and etc. Based on the above analyses and studies, BP neural networks were built to predict characteristics, such as low heat and others, of blended coals, and the prediction accuracy is extremely high. Three cases were predicted in this paper. In addition, the optimization of coal blending was conducted with exhaustive method, and it is very directive to the practical coal blending. The characteristics of neural network are with close relation with the data extension of the input and output samples, so it is universal and has strong expansion.

Study on the photovoltaic (PV) system's application possibility

From summary of the solar photovoltaic project status, the cost and life returns of power generation systems and networks were calculated. The applied possibility of solar photovoltaic system and the promoted factors were technically and economically analyzed . By comparing solar photovoltaic with conventional power generation costs, investment period of the solar photovoltaic systems covered by the regional power grid was calculated, and the results demonstrated that the basic cost of the investment can be recovered. At the same time, the factors on the promotion of solar energy into the possibility were analyzed. According to geographical features of the analysis, it is reasonable to introduce independent photovoltaic power generation system in a field with the transmission distance greater than 50 kilometers.

The Status of Mercury Emission from Coal Combustion Power Station

Mercury is considered a dangerous heavy metal to both humans and the ecosystem because it is highly toxic to the central nervous system and it tends to bioaccumulate in the human body. Coal-fired power plants are one of the main sources of mercury emission to the environment. During combustion, the mercury in the coal is transformed into three species: particle-bound mercury, vapor-phase elemental mercury, and vapor-phase oxidized mercury. Particle-bound Hgp is easily removed by dust control equipment such as baghouse filters and electrostatic precipitators (ESPs). Vapor-phase oxidized mercury is water soluble which makes its removal in wet flue-gas desulfurization units (FGD) possible. Vapor-phase elemental mercury is extremely volatile and insoluble. Therefore, the conversion of mercury from one form to another is important for selecting the appropriate mercury removal technology.

Mercury and Its Effects on Environment and Human’s Health

Mercury (Hg) is one of the most toxic heavy metals commonly found in the global environment including the lithosphere, hydrosphere, atmosphere, and biosphere. Hg is released to the atmosphere from natural and anthropogenic sources. Coal combustion, waste incineration, metal mining, refining and manufacturing, and chlorine-alkali production are currently major anthropogenic source categories in the industrialized world.

The Influence Factors on Mercury Speciation

During coal combustion at a coal-fired power plant, the mercury (Hg) in coal is volatilized and converted to elemental mercury (Hg0) vapor in the high-temperature regions of coal-fired boilers. As the flue gas is cooled, a series of complex reactions begin to convert Hg0 to oxidized mercury (Hg2+) compounds and/or Hg compounds (Hgp) that are in a solid phase at flue-gas cleaning temperatures or Hg that is adsorbed onto the surface of other particles.

Coal-Fired-Derived Flue Gas Mercury Measurement

Coal-fired-derived flue gas mercury measurement mainly includes Ontario Hydro Method, semicontinuous emission monitor, and Appendix K. The Ontario Hydro Method (OHM) is the standard method of measuring and speciating mercury in flue gas, and its solutions were analyzed using a Leeman Labs Hydra AA. The semicontinuous emission monitor (Hg SCEM) uses a gold trap to collect the mercury from the flue gas before analysis with an atomic fluorescence detector. Appendix K (or EPA method 324) is for the continuous sampling of mercury emissions in combustion flue gas streams with sorbent traps. The resulting leachate is analyzed by a cold vapor atomic fluorescence spectrometer (CVAFS) or by a cold vapor atomic absorption spectrometer (CVAA).

Coal-Fired Flue-Gas Mercury Control Technologies

A cost-effective mercury emission control technology is required to reduce the global emission of mercury. Oxidized mercury can be removed in the wet flue-gas desulfurization (WFGD) facilities of coal-combustion processes. Particle-bound mercury can be captured along with fly ash in electrostatic precipitators or baghouses. Due to Hg0 being difficult to control for its insolubility in water, the mercury control technologies are to convert or transfer mercury speciations to each other.

A novel computational scheme and its application for simulation of the flow characteristics of flue gas

In this paper, a novel computational scheme, local whole-information difference scheme (LWDS), was proposed to solve significant pseudo diffusion in recirculating flow zone during numerical simulation. In LWDS, the effect of all of the local around points on the control volume was considered to demonstrate the spatial characteristics of the flow, and the weighted value at each point is adjusted according to the local velocity field, so as to reduce the numerical diffusion. LWDS is with more accuracy than upwind and power difference schemes, and it is applied to compute the flow characteristics of air in a reactor. The results show that the flow characteristics in the reactor affect the mercury speciation distribution in the flue gas, and it also affects the mercury removal efficiency of the mercury sorbent and fly ash. The possible reasons are that different flow characteristics makes the contents in the flue gas be with different resident time in the reactor and affects the chemical reaction between the contents with mercury. In the multiphase flow reactor, when other conditions were same, four injection ports were with high mercury removal efficiency since it was with more uniform distribution of the sorbent in the flue gas.