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Journal of Thermal Science 2013年第3期22卷 261-268页

作者： Jianguo Zhu Ziqu Ouyang qinggang lu Institute of Engineering Thermophysics Chinese Academy of Sciences

High temperature air combustion is a prospecting technology in energy saving and pollutants reduction. Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed was presented. The down-fired combustor, taken as the calculation domain, has the diameter of 220 mm and the height of 3000 mm. 2 cases with air staging combustion are simulated. Compared the simulation results with experimental data, there is a good agreement. It is found that the combustion model and NOx formation model are applicable to simulate the pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed. The results show that there is a uniform temperature profile along the axis of the down-fired combustor. The NOx emissions are lower than those of ordinary pulverized coal combustion, and the NOx emissions are 390 mg/m3 and 352 mg/m3 in Case 1 and Case 2, respectively. At the range of 300-600 mm below the nozzle, the NO concentration decreases, mainly resulting from some homogeneous reactions and heterogeneous reaction. NO concentration has a little increase at the position of 800 mm below the nozzle as the tertiary air supplied to the combustor at the position of 600 mm below the nozzle.

关键词： Pulverized coal combustion Numerical simulation High temperature air NOx

Pressure Drop in Cyclone Separator at High Pressure

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Journal of Thermal Science 2008年第3期17卷 275-280页

作者： Zhu Zhiping Na Yongjie lu qinggang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 Graduate University of Chinese Academy of Sciences Beijing 100190

For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air leakage from the stand pipe into the cyclone was specially focused. A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage and inlet solid loading. The operate pressure, air leakage and inlet solid loading act as significant roles in cyclone pressure drop. The pressure drop increases with the increasing of pressure and decreases with the increasing of the flow rate of air leakage from the standpipe and with the increasing of the inlet solid loading.

关键词： cyclone separator pressure drop air leakage

Agglomeration Characteristics of River Sand and Wheat Stalk Ash Mixture at High Temperatures

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Journal of Thermal Science 2013年第1期22卷 64-70页

作者： Shang Linlin Li Shiyuan lu qinggang College of Mechanical and Transportation Engineering China University of Petroleum(Beijing Campus) Institute of Engineering Thermophysics Chinese Academy of Sciences

The agglomeration characteristics of river sand and wheat stalk ash mixture at various temperatures are investi- gated using a muffle furnace. The surface structural changes, as well as the elemental makeup of the surface and cross-section of the agglomerates, are analyzed by polarized light microscopy, scanning electron microscopy （SEM）, and energy dispersive X-ray （EDX）. Multi-phase equilibrium calculation is performed with FactSage in identifying the melting behavior of the river sand-wheat stalk ash mixture at high temperatures. No indication of agglomeration is detected below 850~C. At a temperature of 900-1000~C, however, obvious agglomeration is observed and the agglomerates solidify further as temperature increases. The presence of potassium and calcium enrichment causes the formation of a sticky sand surface that induces agglomeration. The main component of the agglomerate surface is KEO-42aO-SiO2, which melts at low temperatures. The formation of molten silicates causes particle cohesion. The main ingredient of the binding phase in the cross-section is K20-SiO2-Na20- Al2Oa--CaO; the agglomeration is not the result of the melting behavior of wheat stalk ash itself but the compre- hensive results of chemical reaction and the melting behavior at high temperatures. The multi-phase equilibrium calculations agree well with the experimental results.

关键词： Wheat stalk ash River sand Agglomeration Phase equilibria Microstructure

Effect of Pressure on Minimum Fluidization Velocity

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Journal of Thermal Science 2007年第3期16卷 264-269页

作者： Zhu Zhiping Na Yongjie lu qinggang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 Graduate School of the Chinese Academy of Science Beijing 100080

Minimum fluidization velocity of quartz sand and glass bead under different pressures of 0.5, 1.0, 1.5 and 2.0 MPa were investigated. The minimum fluidization velocity decreases with the increasing of pressure. The influence of pressure to the minimum fluidization velocities is stronger for larger particles than for smaller ones. Based on the test results and Ergun equation, an experience equation of minimum fluidization velocity is proposed and the calculation results are comparable to other researchers＇ results.

关键词： minimum fluidization velocity pressure Ergun equation

The Heat Transfer Coefficients of the Heating Surface of 300 MWe CFB Boiler

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Journal of Thermal Science 2012年第4期21卷 368-376页

作者： WU Haibo ZHANG Man lu qinggang SUN Yunkai Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190China . Graduate University of Chinese Academy of Sciences Beijing 100049China

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

关键词： CFB boiler heating surface heat transfer coefficient calculation

Circulating Fluidized Bed Gasification of Low Rank Coal：Influence of O2/C Molar Ratio on Gasification Performance and Sulphur Transformation

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Journal of Thermal Science 2016年第4期25卷 363-371页

作者： ZHANG Haixia ZHANG Yukui ZHU Zhiping lu qinggang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

To promote the utilization efficiency of coal resources,and to assist with the control of sulphur during gasification and/or downstream processes,it is essential to gain basic knowledge of sulphur transformation associated with gasification *** this research we investigated the influence of O_2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal,and the sulphur transformation mechanism was also *** were performed in a circulating fluidized bed gasifier with O_2/C molar ratio ranging from 0.39 to 0.78 mol/*** results showed that increasing the O_2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65%to 91.92%,and increase sulphur release ratio from 29.66%to63.11%.The increase of O_2/C molar ratio favors the formation of H_2S,and also favors the retained sulphur transforming to more stable *** to the reducing conditions of coal gasification,H_2S is the main form of the released sulphur,which could be formed by decomposition of pyrite and by secondary *** char shows lower sulphur content than fly ash,and mainly exist as sulphates.X-ray photoelectron spectroscopy(XPS)measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char,and the change is more obvious for bottom *** CFB gasification process,bigger char particles circulate in the system and have longer residence time for further reaction,which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.

关键词： gasification circulating fluidized bed sulphur transformation O2/C molar ratio

Experimental Study on Preheated Combustion of Pulverized Semi-coke

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Journal of Thermal Science 2015年第4期24卷 370-377页

作者： YAO Yao ZHU Jianguo lu qinggang ZHOU Zuxu University of Chinese Academy of Sciences Institute of Engineering Thermophysics Chinese Academy of Sciences

In a test rig,pulverized semi-coke was preheated to 850℃in a circulating fluidized bed(CFB)and then cornbusted at 1100℃in a down-fired combustor(DFC).Experiments were conducted to reveal the effects of three secondary air nozzle cases(co-axial jet,top circular jet and wall circular jet)on the NO *** results show that the optimized secondary air nozzle can reduce NO emission.O_2 concentration profile is the major factor affecting NO generation and emission,which is led by the secondary air *** lower O_2 concentration led to the generation of lower initial *** NO emission at the exit of the DFC was reduced from 189 to 92mg/m^3(@6%O_2)with the decrease of initial *** peak of NO at 100 mm below the nozzle should be attributed to the oxidization of NH_3 in the syngas,rather than the oxidization of fuel-N in the *** low and well-distributed O_2 concentration contributes to the reduction of initial NO,which helps to reduce the NO *** combustion effieiencies of the eases of the co-axial jet,the top circular jet,and the wall circular jet are97.88%,98.94%and 98.74%,respectively.

关键词： Pulverized semi-coke Preheated combustion Secondary air nozzle NO emission.

A Model for Agglomeration in Bio-fuel Fired Fluidized Bed

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Journal of Thermal Science 2010年第5期19卷 451-458页

作者： Shiyuan Li Linlin Shang Haipeng Teng qinggang lu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

A mathematical model has been developed to describe the agglomeration process in bio-fuel fired fluidized bed combustor. Based on the balance mechanism of the adhesive force caused by liquid bonding between two parti- cles and the breaking force induced by bubbles in the fiuidized bed, the model considers modified Urbain model and chemical equilibrium calculations using FactSage modeling. This model prediction accounts for the evolve- ment of the adhesive and breaking forces, and clearly demonstrates that the different composition of ash, the in- creasing liquid phase matter and the fiuidization velocity cause defluidization in fluidized bed. In this model, it is the first time to hypothesize that the bonding stress between two particles is proportional to mass fraction of liq- uid phase and inversely proportional to the diameter of particles and viscosity of liquid phase. The defluidization time calculated by this model shows good agreement with that from the experimental data.

关键词： Bio-Fuel Fluidized bed Agglomeration Defluidization Force balance

Experimental Study on Coal Multi-generation in Dual Fluidized Beds

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Journal of Thermal Science 2007年第3期16卷 277-282页

作者： Fan Xiaoxu lu qinggang Na Yongjie Liu Qi Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China Graduate School of the Chinese Academy of Sciences Beijing 100080 China

An atmospheric test system of dual fluidized beds for coal multi-generation was built. One bubbling fluidized bed is for gasification and a circulating fluidized bed for combustion. The two beds are combined with two valves： one valve to send high temperature ash from combustion bed to the gasification bed and another valve to send char and ash from gasification bed to combustion bed. Experiments on Shenhua coal multi-generation were made at temperatures from 1112 K to 1191 K in the dual fluidized beds. The temperatures of the combustor are stable and the char combustion efficiency is about 98%. Increasing air/coal ratio to the fluidized bed leads to the increase of temperature and gasification efficiency. The maximum gasification efficiency is 36.7% and the calorific value of fuel gas is 10.7 MJ/Nm^3. The tar yield in this work is 1.5%, much lower than that of pyrolysis. Carbon conversion efficiency to fuel gas and flue gas is about 90%.

关键词： gasification multi-generation dual fluidized beds tar char combustion

Physicochemical Properties and Gasification Reactivity of the Ultrafine Semi-char derived from a Bench-scale Fluidized Bed Gasifier

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Journal of Thermal Science 2017年第4期26卷 362-370页

作者： ZHANG Yukui ZHANG Haixia ZHU Zhiping NA Yongjie lu qinggang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Zhtmdong coalfield is the largest intact coalfield worldwide and fluidized bed gasification has been considered as a promising way to achieve its clean and efficient utilization. The purpose of this study is to investigate the phy- sicochemical properties and gasification reactivity of the ultrafme semi-char, derived from a bench-scale fluidized bed gasifier, using Zhundong coal as fuel. The results obtained are as follows. In comparison to the raw coal, the carbon and ash content of the semi-char increase after partial gasification, but the ash fusion temperatures of them show no significant difference. Particularly, 76.53% of the sodium in the feed coal has released to the gas phase after fluidized bed gasification. The chemical compositions of the semi-char are closely related to its particle size, attributable to the distinctly different natures of diverse elements. The semi-char exhibits a higher graphitization degree, higher BET surface area, and richer meso- and macropores, which results in superior gasification reactiv- ity than the coal char. The chemical reactivity of the semi-char is significantly improved by an increased gasifica- tion temperature, which suggests the necessity of regasification of the semi-char at a higher temperature. Conse- quently, it will be considered feasible that these carbons in the semi-char from fluidized bed gasitiers are rec- laimed and reused for the gasification process.

关键词： fluidized bed semi-char physicoehemical properties chemical compositions gasification reactivity