Junjiao Zhang

Gaseous emissions from the combustion of a waste mixture containing a high concentration of N2O.

This paper is focused on reducing the emissions from the combustion of a waste mixture containing a high concentration of N2O. A rate model and an equilibrium model were used to predict gaseous emissions from the combustion of the mixture. The influences of temperature and methane were considered, and the experimental research was carried out in a tabular reactor and a pilot combustion furnace. The results showed that for the waste mixture, the combustion temperature should be in the range of 950-1100 degrees C and the gas residence time should be 2s or higher to reduce emissions.

Product gas combustion in fluidized bed for N 2 O reduction

The experimental research on removing N2O with biomass gas was carried out in a small-fluidized bed reactor tube. The decomposition rate of N2O and the production rate of NO impacted by reaction temperature, residence time, reburning position, rate of fuel, initial oxygen content of flue gas and the height of material bed were researched. The results showed that the decomposition rate of N2O was more than 99% with some biomass gas and residence time was 0.32 sec in the reducing zone. The decomposition rate of N2O was increased with the increasing of the distance from air distributor, was decreased with the increasing of the initial oxygen fraction, and was in direct proportion to the height of material bed and the fraction of ejected biomass gas.

The interaction between HCl and Fe 2 O 3 during the chemical looping combustion of MSW

In order to avoid dioxin emission from municipal solid waste combustion (MSW), chemical looping combustion was considered. The interaction between HCl and Fe2O3 was studied in this paper and experiments were carried out in a fixed bed reactor. Chlorine was measured by methyl orange spectrophotometric method. The intermediate reactions were calculated with standard Gibbs free energy and reaction equilibrium constants. The result showed that: when Fe2O3 is used as oxygen carrier, the conversion of HCl to chlorine can be suppressed, thus reduce Dioxin emission.

Modeling the gasification based biomass co-firing in a 600MW pulverized coal boiler

Gasification based biomass co-firing was an attractive technology for utilizing biomass as an additional fuel in utility boilers. Compared to directly co-firing biomass and coal, it showed following benefits: (1) avoiding biomass delivery into the boiler, (2) reduced boiler slagging, (3) avoiding altered ash characteristics. In co-firing demonstration project, higher percentage of biomass gas for co-firing was expected. But the effect of percentage of biomass gas on combustion efficiency, boiler efficiency and pollutant emission was not clear. In the study, numerical simulation of co-firing producer gas from biomass gasification and coal in a 600MWe tangential PC boiler was carried out with CFD method. Combustion behavior and pollutant emission for the coal fired only case and six co-firing cases were compared. The results showed that The effect of co-firing on combustion efficiency was slight, the reduction of NOx emission can be achieved. The NO removal rate was between 45% and 71%. In addition, slagging can be reduced for the temperature decreasing. And the convection heat transfer area should be increased or the biomass gas should be limited to a low percentage to achieve higher boiler efficiency.

Experimental research on gas-solid flow in a dual fluidized bed

Chemical-looping combustion (CLC) is a new method for the combustion of fuel gas with inherent separation of carbon dioxide. The cold interconnected fluidized beds (Ø100) were set-up for the hot model design in this work. The pressure drop of both air reactor (AR) and fuel reactor (FR) were measured and used for CLC system design. The effects of superficial gas velocity on pressure distribution of both AR and FR were presented. Before fluidization, the pressure drop characteristics of two reactors in interconnected dual fluidized bed for CLC sharply increase with the increasing of gas velocity, which just similar to that of conventional circulating fluidized bed. And after fluidization, the pressure drop of two reactors in dual fluidized bed decreased with the increasing gas velocity. It could be seen that uFR must be increased with an enhancive uAR value to ensure exchange of bed material, and the higher of the gas velocity, the more material could be exchanged.

The Resistivity Property of Nikel Loaded Winter Wheat Straw Char

In this paper, the effects of nickel ions concentration (4.0 wt%, 4.5 wt%, 5.0 wt%), carbonization temperature (700°C, 800°C, 900°C), heating rate (5°C/min, 15°C/min, 20°C/min) and particle size (0.1-0.2 mm, 0.2-0.3 mm, 0.3-0.38 mm) on resistivity of char derived from winter wheat straw were studied. The result showed that when nickel loading is 5.0 wt%, carbonization temperature is 900°C, heat rate is 5°C/min and particle size is 0.2-0.3 mm, the resistivity is lower and its value is 1.5 �·cm.

Modeling the Effect of Particle Flow on Erosion in CFB

Fly ash may cause serious erosive wear on steel surfaces along the flow path in a circulating fluidized bed (CFB) boiler. In this paper, erosion model and MFIX software were used to evaluate gas-solids flow on erosion rate. The effects of the particle size and density on the erosive wear were compared quantitatively.

Research on the Reactivity of Oxygen Carrier Fe2O3 for Chemical Looping Combustion (CLC)

Chemical looping combustion (CLC) was a promising combustion technology with inherent separation of CO 2 . In this paper, thermodynamic equilibrium approach was used to investigate the reactions between CO or biomass gas and oxygen carrier Fe 2 O 3 , and experiments were carried out in a laboratory fluidized bed reactor. The results showed that when temperature was below 1000 K, the carbon deposition on oxygen carrier was serious. When CO was used as fuel, the highest gas yield of CO to carbon dioxide reached to 99.5% at 1153 K. And when biomass gas was used as fuel, the highest gas yield of biomass gas to carbon dioxide was almost 75% at 1113 K.

Numerical Modeling of Gas Flow in a 48t/h Biomass-fired Boiler

A numerical model of the flow field of a 48t/h grate-fired boiler was presented in this paper. The air distributions in the furnace under different air supply ratio were considered in order to get the optimum air ratio. The three-dimensional Reynolds averaged Nervier-stokes equation with the Standard k-epsilon Model was solved. The result showed that the airflow ratio played a significant role on the air distribution of the furnace and the optimum airflow ratio of R PA : R SA : R IA = 4:4:2.

Modeling of straw lignin molecule

The pyrolysis of straw was one of the important ways for biomass utilization. Chemical structure of straw lignin had great impact on the decomposition process of straw. In this paper, lignin molecule was modeled with an average structure method and optimized with Density Functional Theory (DFT). The most stable conformations of structural units and structural model of straw lignin were obtained by the optimizing calculation.