Fan W.,Shanghai JiaoTong University |
Li Y.,Shanghai JiaoTong University |
Guo Q.,Shanghai JiaoTong University |
Chen C.,Dongfang Boiler Group Co. |
Wang Y.,Dongfang Boiler Group Co.
Energy | Year: 2017
Air-staged combustion is one of the most sophisticated and effective technologies for reducing NOx emissions. To better understand NOx formation and destruction in air-staged combustion, measurements of the major gas species and NOx profiles along the axial distance of a furnace were obtained in a 20 kW down-fired pilot-scale combustion facility. The furnace of this facility has a representative configuration of a full-scale boiler with a staged combustion system in terms of residence times and temperature characteristics. The combustion air is divided into primary air, secondary air, and burnout air, which can be heated to 80 °C, 200 °C, and 200 °C, respectively by electric heaters before entering the furnace. Under the staged case, a usual NOx trend was obtained by the measurements: coal nitrogen can be rapidly converted to NOx and then reaches a peak concentration in the primary combustion zone, followed by a significant reduction in NOx in the reduction zone. The greater the staged level is, the earlier the reduction stage starts. For the deepest air-staged case with ratio of burnout air to total air of 0.42, the NOx profile curve does not exhibit the features of the NOx peak and a pronounced reduction, as the NOx values are always at very low levels. There exists an NO reducing saturation phenomenon in an overlong reduction zone. For providing data associated with the oxygen-enriched combustion technology that will be available in the near future, low-level oxygen-enriched combustions of coal (21–30%O2) have been performed to assess their NOx emission characteristics compared to the air-staged configuration. There is no essential difference in the mechanism of NO formation and destruction between the staged combustion with oxygen enrichment and the air-staged combustion. With the increase of the staged degree, the impact of O2 concentration promotion on the rise of NOx emission gradually decreases. The NOx rises again at the point where burnout oxidizer addition is caused by the oxidation of some unknown nitrogen-containing intermediates prevailing in the oxygen-poor reduction zone. © 2017 Elsevier Ltd
You C.,Tsinghua University |
Li Y.,Dongfang Boiler Group Co.
Environmental Science and Technology | Year: 2013
Semidry flue gas desulfurization (FGD) experiments were conducted using rapidly hydrated sorbents with four different adhesive carrier particles: circulation ash from a circulating fluidized bed boiler (CFBB circulation ash), fly ash from the first electrical field of the electrostatic precipitator of a circulating fluidized bed boiler (CFBB ESP ash), fly ash from a chain boiler (chain boiler ash), and river sand smaller than 1 mm. The influences of various adhesive carrier particles and operating conditions on the desulfurization characteristics of the sorbents were investigated, including sprayed water, reaction temperature, and the ratio of calcium to sulfur (Ca/S). The experimental results indicated that the rapidly hydrated sorbents had better desulfurization characteristics by using adhesive carrier particles which possessed better pore, adhesion, and fluidization characteristics. The desulfurization efficiency of the system increased as the reaction temperature decreased, it improved from 35% to 90% as the mass flow rate of the sprayed water increased from 0 to 10 kg/h, and it increased from 65.6% to 82.7% as Ca/S increased from 1.0 to 2.0. Based on these findings, a new semidry circulating fluidized bed (CFB)-FGD system using rapidly hydrated sorbent was developed. Using the rapidly hydrated sorbent, this system uses a cyclone separator instead of an ESP or a bag filter to recycle the sorbent particles, thereby decreasing the system flow resistance, saving investment and operating costs of the solids collection equipment. © 2013 American Chemical Society.
Xue W.,Wuhan University |
Qian-Gang P.,DongFang Boiler Group Co. |
Zhi-Jun L.,DongFang Boiler Group Co. |
Hui-Qiang Z.,DongFang Boiler Group Co. |
Yong-Shun T.,DongFang Boiler Group Co.
Engineering Failure Analysis | Year: 2011
This paper describes the creep rupture behaviour, hardness distribution and microstructure of weldment made by submerge arc welding for W strengthened P92 steel. The cross-weld creep tests were carried out at 923K and at stress ranging from 100 to 130MPa. For stress below 120MPa, weld-joints ruptured by the type IV crack, which located in their fine-grained heat-affected zone (FGHAZ) with the smallest measured cross-weld hardness. A strong drop in creep rupture strength of weldment was induced by brittle type IV failure. In addition to coarsening of M23C6 carbides and an equiaxed fine grains in FGHAZ, intermetallic Fe2(Mo,W) Laves phase precipitated on grain boundaries during creep is probably the significant factors caused the type IV failure. © 2010.
Peng Z.,Wuhan University |
Dang Y.,Wuhan University |
Peng F.,Dong Fang Boiler Group Co.
Jinshu Xuebao/ Acta Metallurgica Sinica | Year: 2010
Long-term creep-rupture properties are usually evaluated from short-term data by time-temperature parameter (TTP) method, such as Larson-miller parameter (LMP) and Orr-Sherby- Dorn (OSD) methods. However, the conventional TTP methods sometimes overestimate long-term creep rupture properties if the prediction is based on their short-term test data for 9%-12%Cr ferrite steels. The following concepts/methods are thus proposed in this paper in order to reduce the property overestimation tendency caused by the conventional TTP methods and to obtain a better agreement of the predicted property values with the observed ones. They include the C-value optimization and the multi-C region analysis, the long-term (5×103-1×105 h) creep rupture property prediction using short term test data (5×103 h), the optimization of function used for property prediction, and the effect of d[g(σ)]/d(P) vs P on the stability of steel properties based on the improved LMP method. All the data sets for the 9%-12%Cr steels are from NIMS database for the related calculations and analyses. The results show that the C-value in LMP is not only different from steel to steel type but also varies with the multi-region stress levels, and the new approach to rupture life prediction proposes procedures for extrapolations of the short-term results, with rupture time measurements from tests lasting up to only 5×103 h providing reasonable estimates of 105 h rupture strengths, as well as the variation tendency of d[f(σ)]/d(P) vs P can reflect directly the long-term property stability of the steels investigated. Therefore, the concepts/methods proposed could improve effectively the accordance of predicted property values with observed ones and overcome obviously the overestimation tendency of 105 h strengths, which are more suitable and easily realized to assess the long-term creep-rupture properties of the advanced high Cr ferritic steels. © Copyright.
Wang M.,Southwest Jiaotong University |
Wang M.,Dongfang Boiler Group Co. |
Dongming T.,Southwest Jiaotong University
Applied Mathematics and Information Sciences | Year: 2012
The signcryption scheme plays an important role in the applications which need privacy and authentication simultaneously. In order to get high efficiency in one-to-many communication environment and simplify the management of keys, a novel biometric signcryption scheme, identity-based and group-oriented, is proposed in this paper. In the scheme, the sender signcrypts the message and broadcasts it, but only the members of the receiver group can unsigncrypt the cipher text correctly. The implement of the scheme does not need bilinear pairing computation and modular exponentiation computation, hence it is very efficient. The analysis results show that the scheme is secure. © 2012 NSP Natural Sciences Publishing Cor.
Peng Z.,Wuhan University |
Dang Y.,Wuhan University |
Peng F.,Dongfang Boiler Group Co.
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2012
TP347HFG is an austenitic stainless steel which is considered to be among the grades with the highest potential for use in super critical boilers. It has been reported that micro-addition of Nb and a relatively low level of carbon content can obviously enhance creep resistance in this class of materials. Thus, C and Nb content optimization is of significant interest within the composition range from ASME standard. In this study, the effect of carbon and niobium contents on phase parameters (phase composition, volume fraction and size) and creep rupture time and the related mechanism were investigated for TP347HFG steel. Creep rupture tests were carried out under applied stresses of 230 and 150 MPa, respectively, at 650°C. The rupture times of two samples with different C and Nb contents were 199 and 420 h at 230 MPa, 2426 and 8837 h at 150 MPa, respectively. The sample with lower C content and higher Nb content corresponded to longer rupture time at each of the stress level. The EPMA-EDS+MPSM (multiphase separation method) and TEM-EDS results show that the creep rupture times were remarkably increased for the sample with relatively lower C and higher Nb contents, which correspond to increasing the volume fraction of nano-scale MX and decreasing that of M 23C 6 as well as retarding the coarsening of M 23C 6.On the other hand, more Cr maintained in matrix could also benefit the creep rupture lives. In addition, Thermo-Calc software was used to calculate the mole fraction and the concentration of precipitated phases with various combinations of C and Nb contents over the range of 500-1300°C and the results were in good agreement with the experimental ones.
Hu Z.,Shandong Electric Power Research Institute |
Hao W.,Shandong Electric Power Research Institute |
Xue M.,Hefei University of Technology |
Wang J.,Dongfang Boiler Group Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2010
For getting higher efficiency and lower NOx emission, a test to optimize combustion system is conducted in a 1000 MW bituminous coal-fired boiler in opposed firing pattern. During the test, the gas temperature distribution in furnace is measured, combustion and NOx emission characteristic is studied by varying such factors as type of coal, O2 at economizer exit, mass flow of over fired air (OFA), air damper position of burner and after air port (AAP), combinations of burners and boiler load. It indicates that O2 at economizer exit and mass flow of OFA have great effect on boiler efficiency and NOx emission. It's better to keep these two parameters at 3.0% and 750 t/h respectively , which can also eliminate slagging on platen superheater. O2 deviation along furnace width can be eliminated by setting outer second air damper of burners in same horizontal row at different proper positions. Unburned carbon in fly ash can be decreased by using design coal, closing outer second air damper of AAP, setting burner's core air damper at 50% and shutting down one-layer upper row burners at full load if possible. After adjustment, the measured efficiency of boiler is above 94.4% and NOx emission concentration is lower than 300 mg/m3. They are obviously better than those of boilers in service in China. © 2010 Journal of Mechanical Engineering.
Liu J.-C.,Dongfang Boiler Group Co.
Energy and Environment | Year: 2010
Fossil fuels (i.e., petroleum, natural gas and coal), which meet most of the world's energy demand today, are being depleted rapidly and will be exhausted in decades or several hundred years. Also, their combustion products are causing global problems, such as the greenhouse effect, ozone layer depletion, acid rain and pollution, which are posing great danger for our environment, and eventually, for the total life on our planet. It is the controlled thermonuclear fusion hydrogen energy system that would overcome all these problems and be the permanent solution of the world's energy supply lasting for billions of years.
Cao L.,Dongfang Boiler Group Co. |
Zhou S.-R.,Dongfang Boiler Group Co.
Xiandai Huagong/Modern Chemical Industry | Year: 2011
The coal gas purification process in the integrated gasification combined cycle (IGCC) is divided into wet purification at room temperature and dry purification at high temperature. Special attentions are paid to the dust removal and desulphurization technology and their related equipments of the cleaning system. The merits and shortcomings of the cleaning process are also introduced. Some suggestions on the selection of IGCC's purification process and equipments are put forward finally.
Liu T.-S.,Dongfang Boiler Group Co.
American Society of Mechanical Engineers, Power Division (Publication) POWER | Year: 2011
The bias combustion technology has been widely used in the swirling burner. Take the distribution of the pulverized-coal concentration at the primary air outlet as the division principle, there are three kinds of bias combustion models: radial model with inside dense and outside lean, radial model with outside dense and inside lean, and circumferential model. Considering stable ignition and low NOx emission, at the phase of the pulverized-coal ignition, the dense pulverized-coal flow should be heated by the high temperature flue gas intensively and quickly to ensure the coal's timely ignition and form an In-flame NOx reduction zone for low NOx emission. Hence the bias combustion technology should be in accordance with the recirculation zone. So the radial bias model with inside dense and outside lean suits to central recirculation zone while radial bias model with outside dense and inside lean suits to annular recirculation zone. The circumferential bias model suits to both recirculation zones. Furthermore, appropriate measures should be taken on the burner's arrangement and furnace's design to prevent the obvious increase of slagging problem and unburned carbon in fly ash when using bias and air staged combustion technology. Copyright © 2011 by ASME.