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Sun Z.,Wuxi Huaguang Boiler Co. | Shen J.,Wuxi Huaguang Boiler Co. | Jin B.,Nanjing Southeast University | Wei L.,Wuxi Huaguang Boiler Co.
Biomass and Bioenergy | Year: 2010

The present work reports studies on the mixing and combustion characteristics of cotton stalk with 10-100 mm in length in FBC. Experiments on a cold model show that cotton stalk cannot fluidize, and adding bed material can improve the fluidization condition. Cotton stalk can mix well with 0.6-1 mm alumina at fluidization number N = 3-7. However, when the fluidization number is higher more than 7, the mixing bed will exist a little segregation comparing with N = 3-7. Thermogravimetric experiments show that cotton stalk can be ignited easily at a lower temperature, and its devolatilization and combustion are quick. Fluidized-bed combustion of cotton stalk was tested in a 0.2 MW th test facility. According to the temperature distribution along the bed height, when the primary and secondary air is adapted cotton stalk can be burned stably in the fluidized bed. During pure cotton stalk combustion tests, silica sand and alumina are used as bed material to compare their agglomeration characteristics. SEM/EDX analysis on agglomerate samples after combustion about 38 h suggests that the high alkali metals content causes the formation of the coating around silica sand particles. The coating consists of compounds with low-melting temperature results in agglomeration of silica sand particles. By contrast, alumina is difficult to react with alkali metals from biomass ash, and the agglomeration of alumina was not found at 910 °C. It is found that alumina is more favorable than silica sand particle for use in a fluidized bed in cotton stalk combustion. © 2010 Elsevier Ltd. All rights reserved.

Mao J.-H.,Wuxi Huaguang Boiler Co. | Tang Z.-G.,Wuxi Huaguang Boiler Co. | Jing L.,Wuxi Huaguang Boiler Co. | Xie Y.-R.,Wuxi Huaguang Boiler Co.
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2012

A An introduction is being presented to the design and operation of the first domestic 745 t/h CFB boiler with bypass temperature controlling system for the reheat steam, while influence of the operating condition on NO 2 and SO 2 emission discussed. Performance test results show that the superheater, reheater, cyclone separator and air preheater are all rationally designed; the parameters of reheat steam could be quickly and accurately adjusted by the bypass temperature controlling system; under operating conditions at a load of 220 MW, the average test value of boiler thermal efficiency and the average corrected efficiency are respectively 90.72% and 90.56%; the boiler could be stably and continuously operated at the maximum output of 745 t/h and at the lowest output without auxiliary fuel; the purposes of low NO 2 and SO 2 emission could be achieved if the boiler is rationally operated.

Li Z.-C.,Nanjing Southeast University | Duan Y.-F.,Nanjing Southeast University | Wang Y.-J.,Nanjing Southeast University | Huang Z.-J.,Nanjing Southeast University | And 2 more authors.
Ranliao Huaxue Xuebao/Journal of Fuel Chemistry and Technology | Year: 2013

The Ontario Hydro Method (OHM) was used to sample and analyze the mercury concentration in flue gas before and after ESP and WFGD in a 300 MW power plant. Mercury content in coal, bottom slag, fly ash of ESP, adsorbent (limestone) and desulfurization product (gypsum) was detected by DMA80. Mercury mass balance was calculated based on the online measurements through the boiler system. Factors affecting the distribution, transformation and removal of mercury in flue gas were discussed. The results show that the gaseous mercury (Hg0 and Hg2+) in flue gas accounts for about 95% of total mercury, while mercury in the bottom ash can be neglected. More than 95% of Hgp and a little gaseous phase mercury (Hg0 and Hg2+)were removed by ESP. The efficiencies to remove total mercury by ESP range from 12.77% to 17.38%. A removal efficiency for Hg2+(g) reaches up to 79.93%~90.53% by WFGD, however, the content of Hg0 after WFGD increases because part of oxidized mercury is reduced to elemental mercury during WFGD. The efficiencies to remove total mercury by WFGD range from 9.68% to 29.36%. ESP and WFGD can remove all of the Hgp and a majority of Hg2+ with a total mercury removal efficiency of 25.38%~38.38%. In general, the demercuration in the conventional devices of ESP and WFGD is not high, which perhaps is owing to the lower concentration of Cl in feed coal.

Ren Q.,Nanjing Southeast University | Zhao C.,Nanjing Southeast University | Wu X.,Nanjing Southeast University | Liang C.,Nanjing Southeast University | And 3 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2010

The catalytic effects of iron, aluminum or silicon on the formation of NOX precursors (HCN, NH3 and HNCO) and HCl during wheat straw pyrolysis were studied using a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared (FTIR) spectrometer in argon atmosphere. The results show that the presence of iron, aluminum or silicon decreases conversion of straw-N into NH3 with the sequence of Fe>Si>Al. The iron or silicon addition suppresses N-conversion into HCN and HNCO, and the aluminum addition has no notable influence on HCN emission during pyrolysis. The share of N-conversion to NH3 and HCN increases, but that to HNCO and NO decreases a little in the presence of added iron, aluminum or silicon. The addition of SiO2 results in the highest HCl removal efficiency. © Akadémiai Kiadó, Budapest, Hungary 2009.

Ren Q.,Nanjing Southeast University | Zhao C.,Nanjing Southeast University | Wu X.,Nanjing Southeast University | Liang C.,Nanjing Southeast University | And 3 more authors.
Fuel | Year: 2010

The release behavior tests of NOx precursors from wheat straw during pyrolysis in argon and gasification in 5%O2/95%Ar and 5%CO2/95%Ar were performed using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer. The results show that heating rate and particle size have substantial effects on the selectivity of N-conversion due to the selectivity of cracking of cyclic amides and the secondary reaction influencing the formation of NH3, HCN and HNCO. The atmosphere influences the N-selectivity to HCN, NH3, NO and HNCO. The formation of HCN and NH3 in 5%O2/95%Ar is a result of competition among the opposing effects of O2. The presence of O2 promotes the yields of HCN and HNCO evidently, and HNCO seems to be a favourable product from biomass-N compared in Ar atmosphere although HCN yield is a little bigger than that of HNCO. The use of CO2 reduces the formation of HCN, the yield of NH3 keeps essentially constant compared in Ar, and the emission of HNCO is suppressed. NH3 seems to be a favourable product from biomass-N in 5%CO2/95%Ar. © 2009 Elsevier Ltd. All rights reserved.

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