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Zhao Y.,North China Electrical Power University | Zhao Y.,Shenhua Shendong Power Co. | Sun B.,North China Electrical Power University | Liu Z.,Shenhua Shendong Power Co. | And 4 more authors.
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2014

A measurement method was proposed for average gas velocity in a short duct by dividing the section to be measured into several units with a screen grid for flow rectification, where pressure tapping holes are distributed, and the pressure taps are to be led to a large vessel for acquisition of the average pressure. Numerical simulation was carried out to the flow rectification effected by a screen grid with cross section of 800 mm × 500 mm. Results show that the screen grid is very effective in regulating the originally disordered flow in branch duct of large wind box. The velocity distribution tends to be uniform with reducing arrayed pitch of screen grid, while the rectifying effect is not closely associated with relative location of the screen grid. The thickness of screen grid plays a determining role in influencing the rectifying effect, and the influence becomes gradually weakened when the thickness is over 200 mm. Under the condition that the pitch, location and thickness of screen grid are ideal, the average pressure of each subsection will be in good linear relation with the average gas velocity in each branch duct.


Mingming G.,Tsinghua University | Mingming G.,North China Electrical Power University | Jizhen L.,North China Electrical Power University | Yue G.,Tsinghua University | And 3 more authors.
CFB-11: Proceedings of the 11th International Conference on Fluidized Bed Technology | Year: 2014

Load control is the core of boiler operation control system and is important for the safe and stable of the power plant. The operation of the first 600MW supercritical CFB unit that was recently built in Baima, China showed that the supercritical CFB boiler, differing from the pulverized coal boilers, was featured with large thermal inertia in the furnace. With the conventional load control scheme, the boiler operation was unstable and main steam parameters remarkably deviated from the designed values. Thus, a novel load control scheme was proposed based on the concept of "Burning carbon". During the load adjustment, the amount of burning carbon was kept nearly unchanged in the furnace by controlling the changes of coal feeding, flow rates of the primary and secondary airs, and air to coal ratio. The thermal inertia effect was also considered in the control of feedwater. The application showed that the proposed load control scheme improved the dynamic performance of the boiler, shortening the response time and remaining the main steam pressure and the main steam temperature stable during the load adjustment process.


Peining W.,Tsinghua University | Wenchong X.,Tsinghua University | Qing L.,Tsinghua University | Hairui Y.,Tsinghua University | And 3 more authors.
CFB-11: Proceedings of the 11th International Conference on Fluidized Bed Technology | Year: 2014

Loop seal is one of the most commonly used non-mechanical valve in a circulating fluidized bed (CFB) boiler. When the solids conveyed horizontally from the supply chamber to the recycle chamber, the length of the horizontal section will cause much flow resistance, which not only influences the fan burden but also the mass balance between the furnace and the external loop. In this paper, a high resistant loop seal without aeration in the horizontal passage (H-type loop seal) and a low resistant loop seal with a slope passage (N-type loop seal) was used, respectively. Flow characteristic of quartz sand (Geldart-B particles) in the new type loop seals was studied by comparison with a traditional loop seal (U-type loop seal). The experimental data show that the high resistance in the horizontal passage will weaken the solids recycling capability of the loop seal obviously, so the H-type loop seal is hard to attain a high solids flow rate. However, the slope passage presents a low solids flow resistance, so the pressure drop of the N-type loop seal is much less than the traditional one. Less aeration and less bypassing air are also found with the same solids flow rate through the N-type loop seal. For the N-type loop seal, a small amount of vertical aeration on the supply chamber can further improve the solids recycling capability.


Ding R.,Tsinghua University | Li J.,Tsinghua University | Zhang M.,Tsinghua University | Yang H.,Tsinghua University | And 2 more authors.
CFB-11: Proceedings of the 11th International Conference on Fluidized Bed Technology | Year: 2014

Air staging is widely adopted in commercial circulating fluidized bed (CFB) boilers due to its unique advantages on combustion and pollutant emissions. The secondary air properties, including primary/secondary air ratio, secondary air injection position and penetration depth etc., are of great importance to the design and operation of CFB boilers. This paper comprehensively analyzes the effect of secondary air injection on the combustion and emission. The penetration of the secondary air injection in the furnace is greatly influenced by the bed inventory. By decreasing the bed inventory, the particle concentration near the injection point can be decreased, which contributes to the increase of the secondary air penetration depth. The increase of penetration depth affects the distribution of the oxygen in the furnace and influences the coal combustion efficiency, which proved by the fact that the carbon contents both in the fly ash and the bottom ash drop correspondingly. Meanwhile, by moving the limestone injection points near to the secondary air injection points and increasing the penetration depths of both limestone and secondary-air, the effective residence time of limestone in the furnace is increased as the result that oxygen can meet the limestone and SO2 faster. Such modification on the limestone points can obviously reduce the SO2 emission. As the NOx generation rate is highly correlated to oxygen concentration, decreasing the primary/secondary air ratio will benefit for reducing the NOx emission due to the intensification of the reducing atmosphere in dense bed. The NOx emission is often in conflict with coal combustion efficiency and SO2 emission, so it is significant to achieve an optimization on the arrangement and adjustment of the secondary air.


Hu N.,Tsinghua University | Liu X.,Tsinghua University | Yang S.,Tsinghua University | Cao P.,Shenhua Shendong Power Co. | And 3 more authors.
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2013

Non-monotonic characteristic curves of pressure drop in cyclone of a circulating fluidized bed (CFB) system were measured using transient-blowing method, while relationship between the cyclone pressure drop and solid mass flow studied under specific gas mass flow with corrected model based on cyclone pressure drop approach proposed by Chen. Meanwhile, the stability of CFB system with two cyclones in parallel was analyzed according to the law of mass conservation and constraint conditions as equality in pressure drop of all cyclones, and the least-energy principle, etc. Results show that with the rise of inlet solid mass flow, the cyclone pressure drop first decreases quickly and then increases slowly; the calculated values of cyclone pressure drop based on corrected model fit well with experimental results; when the cyclone pressure drop and circulating flow rate of CFB system are in deviation region, the CFB system will run stably in deviation flow state.


Cao P.Q.,Shenhua Shendong Power Co. | Wang C.A.,Xi'an Jiaotong University | Liu Z.Q.,Shenhua Shendong Power Co. | Du Y.B.,Xi'an Jiaotong University | And 5 more authors.
Advanced Materials Research | Year: 2014

Zhundong coal has a huge proved reserve and many excellent properties. However, the alkali metal content in Zhundong coal is apparently high, which can accelerate the deactivation of De-NOx SCR catalysts. In the present study, the effect of alkali metal deposition on activity of SCR catalysts through solution impregnation method was experimentally investigated. The results indicate that alkali metal deposition on the catalyst surface significantly deactivates the capacity of SCR catalysts. NaOH presents the most intense poisonousness. The catalytic effect on NO reduction reduces with the increase of alkali metal content on catalyst surfaces. In addition, potassium establishes more obvious poisonousness on SCR catalyst than sodium. There is interaction effect between sodium and potassium on deactivating the SCR catalyst. © (2014) Trans Tech Publications, Switzerland.


Liu X.Q.,Shenhua Shendong Power Co. | Wang C.A.,Xi'an Jiaotong University | Du Y.B.,Xi'an Jiaotong University | Lv Q.,Xi'an Jiaotong University | And 6 more authors.
Advanced Materials Research | Year: 2014

Zhundong coal has a huge proved reserve and many excellent properties. However, the alkali metal content in Zhundong coal is distinctly high, which can accelerate the deactivation of De-NOx SCR catalysts. Using solution impregnation method, the effect of operation conditions on activity of SCR catalysts before and after poisoned by sodium was experimentally investigated. The results show that the NO reduction ratio raises with the increase of NH3/NO ratio. Longer residence time results in higher NO reduction ratio. Compared with catalyst poisoned by NaCl, residence time presents less influence on activity of fresh catalyst in 250-400°C, which is beneficial for De-NOx process. Both O2 and NO concentration have no apparent influence on NO reduction ratio. © (2014) Trans Tech Publications, Switzerland.

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