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Low F.,Monash University | De Girolamo A.,Monash University | Wu X.,Monash University | Wu X.,Shanghai Boiler Works Ltd. | And 2 more authors.
Fuel | Year: 2015

In this paper, the emission, partitioning, and characterisation of twelve trace elements (As, Ba, Be, Co, Cr, Cu, Mn, Ni, Pb, Sr, V, and Zn) in the ash deposits from different sections of an industrial pulverised lignite-fired boiler and in the flue gas have been thoroughly examined. Apart from the combustion of the raw lignite, the combustion of coal mixed with 4 wt% of a silica-based additive for the inhibition of ash slagging and fouling has also been conducted to investigate the influence of silica on the behaviour of the aforementioned trace elements. In terms of relative enrichment (RE) in the combustion zone (i.e. coal flame zone), the vaporisation tendencies of the individual trace elements in the lignite studied showed a remarkable deviation from the conventional classification reported by the International Energy Agency (IEA) Coal Research Centre. Irrespective of the use of the additive, Zn in the classic group II and Ba, Co, Cu, and Ni, which are commonly presented as intermediates between group I and II, have been elevated to group III elements for the lignite tested. On trace element partitioning trends across the boiler, the group encompassing As, Cr, Mn, and V, witnessed a noticeable reduction in enrichment across all boiler positions upon using the silica-based additive. The group; Ba, Co, Ni and Zn, have depleted concentrations irrespective of the use of the silica-based additive. For the rest of the trace elements particularly Be, Cu, and Pb, they have intertwining trends between the different RE sections, and also between the two combustion cases of the raw coal and coal mixed with the silica-based additive. Out of all the trace elements studied, addition of the silica-based additive had an opposite effect on Sr where its RE factors was increased throughout. Upon statistical analysis for the case of raw coal alone, As was found to mainly correlate with Ca and Si; Ba, Cr, and Cu was found to correlate with Fe; and V, to correlate with Ca. Addition of the silica-based additive was shown to provide competing reactions for the heterogeneous transformation of the trace elements and hence altering their relationships. This was further supported by X-ray absorption near-edge structure spectroscopy (XANES) analysis of Cr in ash deposits. The amount of highly hazardous Cr(VI) was found to be in between 0% and 14%, with the addition of the silica-based additive incurring an overall reduced Cr(VI) capture/fixation, partially due to significant Cr contamination effect derived from the silica-based additive itself. © 2014 Elsevier Ltd.

Dai B.-Q.,Monash University | Low F.,Monash University | De Girolamo A.,Monash University | Wu X.,Monash University | And 2 more authors.
Energy and Fuels | Year: 2013

In this paper, an intensive characterization of ash deposits collected from different positions of a pulverized-coal (PC) boiler has been conducted to diagnose the ash slagging and fouling issues within this boiler and to clarify the mass balance/flow of individual major elements and their role on ash slagging and fouling. A lab-scale drop-tube furnace has also been employed to elucidate the partitioning of the major metals during coal pyrolysis and char oxidation, to interpret the PC boiler results. The lignite tested is rich in Na and Ca, which are mostly present as organically bound cations and superfine mineral grains. In the air-fired boiler, the refractory minerals of silicates, aluminates, or aluminosilicates preferentially remained in fireside slag and bottom ash, forming low-temperature eutectics via the interaction with CaO and Fe2O3 on the receding char surface. The complex eutectic Ca-Al-Si consists of the liquidus matrix of the dense layer of fireside slag, in which Fe2+-bearing oxide was highly crystallized into a diamond-shape crystal on the water-tube surface. The ash fouling on Feston and superheater tubes was formed with a thinner Fe-rich layer that is followed by the deposition of Na2SO4 liquids. The abundance of Fe 2O3 and CaO in the char matrix is crucial, which triggered the formation of around 80% liquids in the fireside slag with a viscosity of approximating 100 poise at 1200 C. On the reheat tube surface, about 60% of the fully oxidized hematite was even reduced by the metallic iron into magnetite. Na2O and MgO in the char matrix preferentially escaped into flue gas as vaporized metallic vapor and fine oxide particles, respectively. The sulfation of Na-bearing vapor and CaO particle in flue gas was controlled by the partial pressure of Na2SO4 vapor and reaction rate, respectively. © 2013 American Chemical Society.

Cai H.,Shanghai Boiler Works Ltd. | Wu Y.,Xi'an Jiaotong University | Yang D.,Xi'an Jiaotong University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

Under sub-critical, near-critical and supercritical pressure, this paper experimentally investigated the heat transfer characteristics of vertical upward low mass-flux optimized rifled tube, which is applied in supercritical W-shape flame boiler. The wall temperature distribution in rifled tube was obtained and the effects of pressure, inner wall heat flux and mass flux on heat transfer characteristics was analyzed. The results illustrate that low mass-flux optimized rifled tube has good heat transfer performance and can efficiently prevent the occurrence of departure from nucleate boiling (DNB). In sub-critical pressure region, with the increase of pressure and inner wall heat flux and the decrease of mass flux, dryout occurs ahead and the wall temperature in post-dryout region increases obviously. Compared with the heat transfer characteristics of rifled tube at sub-critical pressure, that in near-critical pressure region gets worse, the wall temperature significantly rises and the critical quality decreases with increasing pressure. At supercritical pressure, heat transfer enhancement occurs in pseudo-critical enthalpy region in rifled tube; while the pressure approaches critical pressure, the heat transfer is enhanced more; the wall temperature increases with increasing pressure and heat flux and with decreasing mass flux. © 2011 Chin. Soc. for Elec. Eng.

Zhang J.,Xi'an Jiaotong University | Chen K.,Xi'an Jiaotong University | Wang C.,Xi'an Jiaotong University | Xiao K.,Shanghai Boiler Works Ltd. | And 2 more authors.
Energy and Fuels | Year: 2013

A 3-MW pilot-scale facility was used to study the effect of separated overfire air (SOFA) on NOx emissions from utility boilers. Experiment results showed that NOx emissions decreased as the excess air ratio in the main combustion zone first decreased, but remained unchanged when the excess air ratio was above a certain value; the carbon content in fly ash increased with the decrease of the excess air ratio in the main combustion zone; NOx emissions decreased and the heat loss due to unburned carbon increased as the residence time in the reduction zone (the zone in the furnace from the middle of combustion zone to the middle of the SOFA zone) increased. Based on the experiment results, a residence time of 2.12-2.68 s is recommended for the reduction zone. Besides, numerical simulations were conducted about the pilot-scale facility and a 600-MW boiler firing the blended coal of Shenhua coal (80 wt %) and Baode coal (20 wt %). The simulations, together with the experiments, showed that there was a critical excess air ratio with value of ∼0.8 for the minimum NOx emissions with relatively low unburned carbon. This critical value, together with the residence time of 2.35 s, which is in the range recommended by our experiments, were used in the retrofit of the 600-MW boiler by SOFA technology, leading to a reduction of NOx emissions as high as 60%. © 2013 American Chemical Society.

Chen K.,Xi'an Jiaotong University | Zhang J.,Shanghai Boiler Works Ltd. | Che D.,Xi'an Jiaotong University
Applied Thermal Engineering | Year: 2016

In order to provide references for designing boilers with separated over-fire air (SOFA), numerical simulation was applied for studying the effect of SOFA on temperature, heat flux and fuel combustion in a 3 MW pilot-scale facility. Simulation results agrees well with measureable data. Results show the temperature and the sensible heat flux of the flue-gas at the furnace outlet first decrease, and then increase with the excess air ratio in the combustion zone. As the SOFA ports rises, the temperature and the sensible heat flux of flue-gas decrease at the furnace outlet. These variations are caused by variations of the sensible heat flux of air injected into furnace. Moreover, as the SOFA ratio increases, both the total heat flux from furnace walls and the fuel combustion heat decrease. The maximum decrease of the heat flux from furnace walls occupies 10% of the total in the case without SOFA. The maximum decrease of the fuel combustion heat occupies 8% of the total, which is caused by the unburnt carbon in bottom ash. The SOFA position has little influence on the total heat flux and the fuel combustion heat. These results are valuable for designing boilers with SOFA. © 2016 Elsevier Ltd

Zhang Y.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhu L.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Ql A.,Shanghai Boiler Works Ltd. | Lu Z.,Shanghai Boiler Works Ltd.
ISIJ International | Year: 2010

In this paper, the mechanical properties and microstructural evolution of S30432 heat-resistant steel during aging at 650°C were investigated, and the effect of microstructural evolution on the yield strength, tensile strength, hardness and impact toughness was discussed. The results show that, the change of strength and hardness can be divided into three stages. In the first stage (before 500 h), the precipitation of fine ε-Cu plays a main role in the significant increase of the strength and hardness. In the second stage (500-5000h), the coarsening of εe-Cu is the key factor to decrease the strength and hardness. After 5 000 h of aging, there is no obvious change in the strength and hardness. Similarly, the change of impact toughness during aging of S30432 steel at 650°C can also be divided into three stages. The sharp decrease of impact toughness in the first stage results from the precipitation of M23C6 and ε-Cu particles. At stage II, the impact toughness keeps on declining as a result of gradual coarsening of M 23C6, ε-Cu and Nb(C, N). Finally, M 23C6, ε-Cu and Nb(C, N) are relatively stable, so that the impact toughness tends to be stable gradually. © 2010 ISIJ.

Xiong J.,Huazhong University of Science and Technology | Xiong J.,Shanghai Boiler Works Ltd. | Zhao H.,Huazhong University of Science and Technology | Zheng C.,Huazhong University of Science and Technology
International Journal of Greenhouse Gas Control | Year: 2012

Oxy-combustion technology, through adding a cryogenic air separation unit process and a flue gas treatment unit process to a conventional combustion process, has been rapidly developed because it is considered as a feasible choice to capture CO 2 from power plants for sequestration. To reach a comprehensive understanding of the thermodynamic and economic characteristics of the oxy-combustion process, a detailed thermoeconomic cost analysis of a 600MW e oxy-combustion pulverized-coal-fired power plant was carried out. Based on the detailed results of exergy analysis and the latest data of investment cost, the results of exergy cost and thermoeconomic cost were obtained. It is found that, in comparison to the corresponding conventional supercritical plant with the same gross output (600MW e), the additional power consumption in the oxy-combustion system increases the unit exergy costs (or unit thermoeconomic costs) of products for about 10%. On the other hand, the additional monetary cost, including investment cost, interest, and operation and maintenance cost, in the oxy-combustion system increases the unit thermoeconomic costs of products for nearly another 10%. The relation between the unit thermoeconomic cost change and the unit exergy cost change in the oxy-combustion system comparing to the conventional system was established. Moreover, in this paper, a new decomposition method for exergy cost was proposed to explore the formation mechanism of the exergy cost, furthermore, the thermoeconomic cost. The unit exergy cost was decomposed into three parts: fuel, exergy destruction, and negentropy. Meanwhile, the reasonable unit exergy costs of exergy destructions happened in the system can be defined. It is found that the exergy destruction part is the most important factor that affects the unit exergy costs of products for these components in the same model (such as the boiler model). © 2012 Elsevier Ltd.

Shanghai Boiler Works Ltd. | Date: 2014-08-27

A plasma oil-free ignition system in oxygen enriched environment comprises a plasma generator and a burner. The plasma oil-free ignition system comprises a sleeve group coaxially arranged with the burner, and the sleeve group comprises multiple coaxially sleeved sleeves. Annular spaces are formed between adjacent sleeves and between the sleeves and the burner. Oxygen ducts are arranged on the sleeves, and oxygen ducts are arranged on the burner. Plasmas jetted by the plasma generators form a local high temperature zone filled with high temperature plasma and pulverized coal air flow. A certain amount of oxygen is fed to the burner through the oxygen duct therein to form local oxygen enriched zones in the annular spaces and the subsequent adjacent spaces through which air flows, thus realizing oxygen enriched combustion of volatile matters or coke or mixture thereof, and combustion the pulverized coal air flow more intensely to release more heat so as to ignite the primary air pulverized coal air flow quickly and burn the pulverized coal air flow stably. The invention has simple structure, is applicable to different coal types, especially applicable to the plasma oil-free ignition system in oxygen enriched environment of coal types with low volatile matters.

A dense/dilute pulverized coal separator structure (4) of a single-fireball octagonal direct-flow burner, of which a boiler body (1) is provided with eight burner groups, each water cooled wall (9) is provided with two burner groups respectively, each of the burner groups comprises multiple nozzles toward the same burner (10), and center lines of all nozzles on the eight burner groups form an imaginary tangent circle (11) in a furnace along the same tangential direction. In the dense/dilute pulverized coal separator structure (4), eight burner groups are arranged on four water cooled walls (9) of the boiler (1), thus increasing pulverized coal concentration of a pulverized rich coal area, allowing wall heat load qHr of a lower burner area to be higher, allowing burning temperature of the area to meet requirements for anthracite burning stability, shortening distance of jet flow from a nozzle outlet to downstream adjacent air flow, being capable of using lower primary pulverized coal air flow velocity, enhancing heat flow intensity at the nozzle outlet, improving convection and radiation heat transfer capacity, and ensuring timely ignition of pulverized anthracite air flow and stable burning of the boiler at low load without oil.

Shanghai Boiler Works Ltd. | Date: 2013-05-29

A dense phase swirl pulverized coal burner comprises a primary air channel, a direct flow secondary air channel and a outermost swirl secondary air channel; and multiple levels of pulverized coal concentration rings are arranged axially at intervals along the oil gun casing in a straight tube section of the primary air channel, so that pulverized coal air flow is distributed thickly outside and thinly inside the primary air nozzle. In the invention, dense phase pulverized coal outside the primary air nozzle passes through guide vanes, forms disturbed flow, is ejected into a furnace and mixes with high temperature backflow flue gas rapidly and sufficiently at an outlet. Meanwhile, dilute pulverized coal air flow at the center is ejected into the furnace by direct flow, ensuring subsequent mixing and combustion of pulverized coal flow. The primary air nozzle and the secondary air nozzle are provided with cone flaring structures with certain angle to effectively control appropriate mixing of secondary air and pulverized coal. The invention has advantages of strong ignition and combustion stability, good coal adaptability, low nitric oxide emission, simple primary air channel structure and small resistance, which effectively slows wear rate of parts.

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