Experimental study of the influence of sodium salts as additive to NOxOUT process

Zhaoping Zhong,Xiujin Liang,Baosheng Jin,Xiaolin Chen,Weiling Li,Hongge Wei,Houkun Guo 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5

An experimental study of the SNCR process with urea as reducing agent and sodium salts as additive has been carried out, and detailed analysis of the reaction mechanism has been given here. In the temperature range of 800-975 oC, NO concentration decreases at first and then increases while the concentration of N2O increases at first and then decreases with the increasing of temperature, and the turning point is 900 oC. With increasing of normalized stoichiometric ratio of reduction nitrogen to NOx (NSR), NO removal efficiency increases, while the concentration of N2O also increases, which decreases overall NOx removal efficiency. With sodium salts as additive, the concentration of N2O decreases with increasing of sodium salts addition at all temperatures, while the concentration of NO decreases at first and then increases at low-temperature side of the temperature window and increases at high-temperature side with additional increasing, whose changing extent is smaller than N2O. Since sodium salts as additive can remove N2O effectively and have no large influence on the removal of NO, the effect of sodium salts as additive is the combined effect of the production of active radicals and the removal of HNCO produced by the decomposition of urea through neutralization reactions, which is more important. To achieve the same effect under each condition, the needed addition of NaOH and CH3COONa is less than that of Na2CO3 counting as Na atom. For the decomposition of CH3COONa can produce CH3COO, its addition can promote the reduction of NO more obviously at the lower temperature than Na2CO3 or NaOH. Overall NOx removal efficiency at 900 oC with NSR=1.5 had been improved from about 30% to 70.45% through the addition of sodium salts. Sodium salts as additive caused the flue gas to become alkaline gas, but it was not serious for sodium salts existing as NaNCO.

Simulation of large biomass pellets in fluidized bed by DEM-CFD

Zhaoping Zhong,Lingli Zhu,Heng Wang,Zeyu Wang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.10

An improved numerical model was proposed to solve the problem that the traditional DEM-CFD (Discrete element method-computational fluid dynamics) method was not suitable for the flow simulation of large particles. In the improved model, the large particle was regarded as an agglomerate of many small fictitious spheres. Herein, the drag force between gas and large pellets was assumed as a combined effect of that between gas and fictitious spheres by volume penalty method. Based on the proposed model, the flow of the mixtures of large biomass pellets and quartz sands in fluidized bed was simulated. It shows that the existence of the biomass pellets has a great impact on the flow field. The flow patterns and pressure drops under different working conditions in simulation results have a good agreement with that in experimental results partially, which also tests the proposed model.

Intelligent identification of the flow regimes of two-component particles in a fluidized bed with the optimized fuzzy c-means clustering algorithm

Zhaoping Zhong,Heng Wang,Xiaoyi Wang,Feihong Guo 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.5

Flow regime identification is important in the application of fluidized beds. This paper provides a method for deciding flow regime number by objective criterion. The optimized fuzzy c-means clustering algorithm was used to cluster the flow regime classification of two-component particles in a fluidized bed. The genetic algorithm was applied to optimize the initial center clusters of fuzzy c-means clustering. Hilbert-Huang transform was applied to analyze pressure fluctuation signals and extract the characteristic parameters. Three clusters were found and respectively ascribed to three flow regimes: bubbling bed, slugging bed, and turbulent bed. A multilayer neural network was used to train and test the identification system of the flow regimes. The identification accuracies of bubbling bed, slugging bed, and turbulent bed can reach 91.67%, 92.85%, and 91.30%, respectively.

Microscopic flow characteristics in fluidized bed of cylinder-shaped particles

Chunhua Wang,Zhaoping Zhong,Xiaoyi Wang 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.12

IBM (Immersed boundary method) and DEM (Discrete element method) coupling method were used to simulate the flow of cylinder-shaped particles in a fluidized bed. The greatest advantage of IBM-DEM is that it can reveal the microscopic characteristics of dense-phase gas-particle flow in Cartesian grids. Large cylinder-shaped particles are very difficult to fluidize, and slugging flow can be observed even if the static bed height is low. The gas flow field around the particle in fluidized bed is analyzed, and the formation and development of vortex behind the particle is affected obviously by the neighboring particles. Particle trajectory is obtained, and the effect of gas phase on particle rotation becomes active as particle size increases. Compared with the experimental results, the gas-solid force in simulation results is higher. This calculation error may be reduced by decreasing the grid size.

Photooxidative removal of Hg0 from simulated flue gas using UV/H2O2 advanced oxidation process: Influence of operational parameters

Bo Zhang,Zhaoping Zhong,Kuan Ding,Lulu Yu 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.1

Element mercury (Hg0) from flue gas is difficult to remove because of its low solubility in water and high volatility. A new technology for photooxidative removal of Hg0 with an ultraviolet (UV)/H2O2 advanced oxidation process is studied in an efficient laboratory-scale bubble column reactor. Influence of several key operational parameters on Hg0 removal efficiency is investigated. The results show that an increase in the UV light power, H2O2 initial concentration or H2O2 solution volume will enhance Hg0 removal. The Hg0 removal is inhibited by an increase of the Hg0initial concentration. The solution initial pH and pH conditioning agent have a remarkable synergistic effect. The highest Hg0 removal efficiencies are achieved at the UV light power of 36W, H2O2 initial concentration of 0.125 mol/L, Hg0initial concentration of 25.3 μg/Nm3, solution initial pH of 5, H2O2 solution volume of 600 ml, respectively. In addition,the O2 percentage has little effect on the Hg0 removal efficiency. This study is beneficial for the potential practical application of Hg0 removal from coal-fired flue gas with UV/H2O2 advanced oxidation process.

Application of Hilbert-Huang transformation in fluidized bed with two-component (biomass particles and quartz sands) mixing flow

Xiaoyi Wang,Zhaoping Zhong,Heng Wang,Zeyu Wang 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.1

Hilbert-Huang transformation was used to investigate the nonlinear characteristics of two-component (bio-mass particles and quartz sand) mixing flow by analyzing the pressure fluctuation signals in fluidized bed. Based onempirical mode decomposition (EMD), the Hilbert-Huang spectra in bubbling and slugging flow patterns were ob-tained and analyzed. In bubbling flow pattern, compared with one-component (quartz sand) flow, the energy of two-component mixing flow is lower in 0-5 Hz and higher in 40-50 Hz. In slugging flow pattern, the energy in pressurefluctuation mainly lies in 0-5 Hz. and the effect of biomass particles on the Hilbert-Huang spectrum is not very obvi-ous. Compared with traditional power spectral density (PSD), HHT is much more suitable for investigating pressurefluctuation signals in fluidized beds.

Flow regime recognition in the spouted bed based on Hilbert-Huang transformation

Wang Chunhua,Zhong Zhaoping,Li Rui 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1

Empirical mode decomposition has been used to decompose the pressure fluctuation signals in the spouted bed into several intrinsic mode functions, and these modes were transformed from the time domain into the frequency domain by Hilbert transformation. According to the characteristic parameters extracted from these modes, flow regimes were recognized by RBF neural network, and parameters in RBF neural network were optimized by adaptive genetic algorithm. The recognition accuracy of packed bed, spouted bed, bubbly fluidized bed and slugging bed can reach 90%,85%, 85%, 95%, respectively.

Effects of cellulose, hemicellulose and lignin on biomass pyrolysis kinetics

Lingli Zhu,Zhaoping Zhong 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.10

In order to investigate interactions among biomass components on pyrolysis kinetics, pyrolysis experiments of individual components, synthetic biomass (designed by Design-Export software) and natural biomass (rice husk and corn straw) were conducted on a thermogravimetric analyzer (TGA). The results revealed that the pyrolysis behavior of cellulose is sharp, which is with low pyrolysis reaction order (1.38), high activation energy (168.61 kJ/mol) and high pre-exponential factor (3.50E+12 /s). The pyrolysis behavior of hemicellulose and lignin is slower but more complicated, both with high pyrolysis reaction order (2.30, 1.51), low activation energy (126.31, 87.21 kJ/mol), and low pre-exponential factor (9.67E+09, 2.59E+05 /s). Comparison of the experimental and calculated kinetics of synthetic samples confirmed that interactive effects on pyrolysis kinetics exist in the co-pyrolysis process. In particular, the presence of lignin inhibited the pyrolysis reaction rate of synthetic biomass, and cellulose played the dominant role in the activation energy and frequency factor. The pyrolysis reaction order was strongly influenced by hemicellulose owing to its abundant and complex branched chains. The predicted model was also established for calculating kinetic parameters of natural biomass with known proportions of three components. The predicted results were consistent with the experimental ones, validating the effectiveness of the prediction model.

Fuel properties of bio-oil/bio-diesel mixture characterized by TG, FTIR and 1^H NMR

Jiang Xiaoxiang,Zhong Zhaoping,Naoko Ellis 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1

There has been an increasing interest in alternative fuels made from biomass which is abundant and renewable. Bio-oil and bio-diesel seem to be such promising liquid fuels. Bio-oil produced by fast pyrolysis of biomass is highly viscous, acidic, and has high water content. To overcome these problems as a fuel, a method of emulsifying bio-oil with bio-diesel was performed in the previous paper, and a stable mixture of bio-oil and bio-diesel was successfully prepared. In this paper, several properties of the mixture are discussed by using TG, FTIR and 1^H NMR. The results show us that, compared with crude bio-oil, some properties of bio-oil/bio-diesel mixture such as water content,acid number, viscosity are much improved. The thermal decomposition of the mixture under air/nitrogen is shown using a thermogravimetric analyzer (TGA). Further information about the functional groups is exhibited through Fourier Transform infrared spectrometer (FTIR) and nuclear magnetic spectroscopy (NMR).

Performance of fluidized bed electrode in a molten carbonate fuel cell anode

Jubing Zhang,Zhaoping Zhong,Jianmin Xiao,Zongming Fu,Jinxiao Zhao,Weiling Li,Min Yang 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.8

A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated in a molten carbonate fuel cell anode with an O_2/CO_2/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow rates of H_2, O_2 and CO_2, choosing suitable nickel particle content together with appropriate O_2/CO_2 ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56 mA·cm^(−2) is achieved under optimum performance as follows:a cylindrically curved nickel plate current collector, nickel particle content of 7.89%, the reaction temperature of 923 K,H_2 flow rate of 275 mL·min^(−1), O_2/CO_2 flow rate of 10/20 mL·min−1 and O_2/CO_2 ratio of 1 : 2.