Tongmo Xu

Study on fusion characteristics of biomass ash.

The ash fusion characteristics (AFC) of Capsicum stalks ashes, cotton stalks ashes and wheat stalks ashes that all prepared by ashing at 400 degrees C, 600 degrees C and 815 degrees C are consistent after 860 degrees C, 990 degrees C and 840 degrees C, respectively in the ash fusion temperature test and TG. Initial deformation temperature (IDT) increases with decreased K(2)O and went up with increased MgO, CaO, Fe(2)O(3) and Al(2)O(3). Softening temperature (ST), hemispherical temperature (HT) and fluid temperature (FT) do not affected by the concentrations of each element and the ashing temperature obviously. Therefore, the IDT may be as an evaluation index of biomass AFC rather than the ST used as an evaluation index of coal AFC. XRD shows that no matter what the ashing temperature is, the biomass ashes contain same high-temperature molten material. Therefore, evaluation of the biomass AFC should not be simply on the proportion of elements except IDT, but the high-temperature molten material in biomass ash.

Burning Low Volatile Fuel in Tangentially Fired Furnaces with Fuel Rich/Lean Burners

Pulverized coal combustion in tangentially fired furnaces with fuel rich/lean burners was investigated for three low volatile coals. The burners were operated under the conditions with varied value N-d, which means the ratio of coal concentration of the fuel rich stream to that of the fuel lean stream. The wall temperature distributions in various positions were measured and analyzed. The carbon content in the char and Nox emission were detected under various conditions. The new burners with fuel rich/lean streams were utilized in a thermal power station to burn low volatile coal. The results show that the N-d value has significant influences on the distributions of temperature and char burnout. There exists an optimal N-d value under which the carbon content in the char and the Nox emission is relatively low. The coal ignition and Nox emission in the utilized power station are improved after retrofitting the burners.

Catalytic reduction of SO2 during combustion of typical chinese coals

The catalytic effects of doping agents on SO2 emission as well as the coal combustion behavior were investigated by thermogravimetry. All experiments were carried out in a flowing air atmosphere at a heating rate of 20 or 30 °C/min up to 1000 °C. The doping agents employed were NaCl, CaCl2, FeCl3, FeCl2 and Fe2O3. The experimental results show that the agents added in coal reduce SO2 emission of coal, with CaCl2 being the most effective. The doping agents work with different mechanisms. The catalysis of NaCl, CaCl2, and Fe2O3 promotes the reactions between SO2 and the minerals in coal, and enhances the sulfur retention capacity of coal ash, thus decreasing SO2 concentration in flue gas. They have weak effects on the combustion behavior of the coal. FeCl3 and FeCl2 have strong effects on coal combustion behaviour. They accelerate the combustion and improve the ignition of the char subsequently formed, increasing SO2 concentration in flue gas in the region from 300 to 520 °C. However, they reduce the total amount of SO2 emission during combustion. The reduction of SO2 yield by FeCl3 and FeCl2 mainly results from the Fe2O3 created from them at high temperatures.

Kinetics investigation on the reduction of NO using straw char based on physicochemical characterization

NO reduction using straw-char has been investigated in a fixed bed, and the effects of char-preparation temperature, reduction temperature, char concentration C(char) and NO concentration C(NO) were considered. Straw char was prepared at three temperatures, 873, 1073 and 1273K. The characterization was conducted by employing SEM-EDS, XRD, BET and TGA. Results show that the char prepared at 1073K holds the most developed pore structure and surface area, the best combustion activity, and the highest NO reduction rate. The reduction rate of NO linearly increases with increasing char concentration, but decreases with increasing NO concentration following a power-function relation. A transition temperature region from dynamic-control to diffusion-control is found to be around 1173K. In the dynamic-control region, the apparent activation energy E of char-NO reaction is in the range of 89.78-95.41kJ mol(-1), affected inconspicuously by the char-preparation temperature. The reaction rate between NO and straw-char is given by r(NO)=k(0)·exp(-11,069/T)·C(NO)(0.89)·C(char).

The Effect of Particle Size and Heating Rate on Pyrolysis of Waste Capsicum Stalks Biomass

With pyrolysis as an attractive way to reduce CO2 and degrade residues, the effect of particle size and heating rate on pyrolysis of capsicum stalks has been investigated by thermogravimetry-differential gravimetric analysis and kinetic studies. Results show that pyrolysis reaction rate increases with increasing particle size. It is supposed that the contents of hemicelluloses, cellulose, lignin, and ash of various particle sizes have significant influence on the pyrolysis of biomass. Meanwhile, high heating rate does not mean high reaction rate, there is a complex competition effect between thermal hysteresis effects and the driving force originated from different heating rates.

Effect of particle size in a limestone–hydrochloric acid reaction system

Experimental characterization of the wet flue gas desulfurization process is carried out using a model limestone-hydrochloric acid reaction system, with in-situ measurement of the dissolution rate and particle size distribution. The limestone source, initial particle size distribution, working temperature and pH value are varied in large ranges. The dissolution rate is found to be higher when the average particle size is smaller, the temperature is higher, or the pH is lower. An empirical equation is established to correlate the dissolution rate with the particle size and working conditions, which agrees well with measurements. The results may be useful for providing insights to improve the efficiency of the wet flue gas desulfurization process, as well as other solid particle-liquid solution reactions.

Effects of minerals on the release of nitrogen species from anthracite

Abstract Experiments have been carried out to investigate the effects of minerals on nitrogen species emission including NO and its precursors from a high rank coal during temperature-programmed combustion by TG/EGA method at 10°C/min. Sodium was found to be an excellent catalyst for the reduction of NO and HCN evolution due to its higher catalysis of sodium on the char-NO reaction. However, iron can induce an increase of NO release. Calcium and titanium additives can be classified as inactive constituents because of their weak catalysis on HCN and NO emission. All the metallic additives can promote NH3 emission except sodium. Parent coal has higher fractions of nitrogen release as NO and NH3 and lower fraction of nitrogen release as HCN than demineralized coal, which can be attributed to the catalysis of indigenous minerals in parent coal.

IDENTIFICATION OF GAS–SOLID TWO-PHASE FLOW REGIMES USING HILBERT–HUANG TRANSFORM AND NEURAL-NETWORK TECHNIQUES

This work presents a new methodology for flow regime identification in a gas–solid two-phase flow system. The approach of identification employs the artificial neural network (ANN) technique, considering the applications with electrostatic sensor as a measuring device and Hilbert–Huang transformation (HHT) as the post-processing method. The electrostatic fluctuation signals detected from an electrostatic sensor are processed using HHT to gain the Hilbert marginal spectrums. Then four characteristic parameters of the marginal spectra are extracted as the input of BP neural network for flow regime identification. They are subband energy (SE), first-order difference of subband energy (DSE), subband energy cepstrum coefficients (SECC), and first-order difference of the subband energy cepstrum coefficients (DSECC). The results show that the characteristic parameters of the Hilbert marginal spectrum of the electrostatic signal can identify the three flow regimes of gas–solid two-phase flow in a horizontal pipe, especially the DSECC.

Experimental Study on Limestone Dissolution in Acid Solution

Hydrochloric acid is used to simulate sulfur dioxide in flue gas to measure the dissolution rate of limestone. The influence of pH value and temperature of reaction on the limestone dissolution rate in acid solution is investigated. The dissolution rate of limestone from two sources is studied. A mathematic model of dissolution rate is built and experimental data are fitted by the model. The experimental system and mathematic model is verified to be feasible for studying activity of limestone. The experimental system is simple and convenient to operate, so it can be used in engineering application to obtain dissolution rate of limestone for design of wet flue gas desulfurization system.

Prediction of Calorific Value of Coal Using Real Power Plant Data

With the depletion of coal in the world, coal quality fluctuates and deviates greatly from the designed coal in many large scale coal-fired power plants. This increases the coal consumption while reduces the boiler combustion efficiency and stability. Thus, it is very important to conduct real-time measurement to the quality of the coal for optimizing the operation. The calorific value analysis is a significant part of the coal quality analysis, and regular proximate analysis method can’t meet real-time control requirements. In this chapter, an artificial neural network (ANN) model using real plant data for prediction of net calorific value of coal in a China power plant is reported. A three-layer BP neural network has been adopted. The input parameters selection was optimized with a compromise between smaller number of parameters and higher level of accuracy through sensitivity analysis. The activation function selection was also discussed in details. The results indicate that when the pureline was selected as the activation function for hidden layer and logsig was selected as the activation function for output layer, the prediction is most accurate. The results have shown good potential for predicting the net calorific value of coal using the real time data. This information will enhance the performance of the combustion control system for power utilities.