双氧水对超临界水中褐煤制氢过程的影响

采用连续式超临界水反应装置,以质量分数为20%的水煤浆为反应原料,考察氧化剂H_2O_2对褐煤制氢过程的影响。结果表明,以H_2O_2为氧化剂,在一定范围内可提高褐煤制氢过程的碳气化率和氢气产率,减少焦油产量,在一定程度上可实现系统内部供热。在反应温度600℃、反应压力25 MPa的条件下,n(O)/n(C)为0.3时,气相中H_2体积分数及其产率均达到最高值。

整体煤气化联合循环发电系统中气化参数对气化单元性能的影响

整体煤气化联合循环(integrated gasification combined cycle,IGCC)发电系统中气化岛包含气化单元和净化单元,气化单元由气化炉、废热锅炉和空分分离装置组成。合成气化学能和冷煤气效率直接影响着整个IGCC电站系统效率,是衡量合成气品质和气化炉性能的关键参数。采用Thermoflex软件对200MW级IGCC气化单元进行模拟计算。着重研究水煤浆浓度、氧碳摩尔比、气化温度、气化压力对气化单元性能的影响。计算结果表明:在较低气化温度下增加水煤浆浓度有利于冷煤气效率和合成气化学能的增加。调节氧碳摩尔比对调节气化炉温度水平具有良好的灵敏性和有效性。另外,氧碳摩尔比还能够起到分配煤中化学能的作用,即调节煤中化学能在合成气化学能和物理显热之间的分配比例。采用低温、加压方式,有利于提高合成气化学能。

Environmental Impacts of Feeding High-fiber Diet to Pigs

The concentration of volatile fatty acids （VFA） determined from a previous study was used to determine the concentration of carbon dioxide （CO2） and methane （CH4） in pig digesta using the model developed for ruminant animals. Digesta from the stomach, cecum and colon of pigs （n = 3 dietl） were used for the determination of VFA. The pigs were fed either a low fiber diet （LFD; 8.3% aNDF） as control, or one of the high-fiber diets （HFD, 22.4% aNDF; D1, D2 and D3） containing 1：2, 1：1 and 2：1, oats to barley ratios, respectively. Results indicated that the concentrations of CO2 and CH4 in pigs fed HFD were, on the average, 25.8 and 24.2%, respectively lower （P 〈 0.05） than pigs fed LFD. Pigs fed the highest oat to barley ratio also showed higher （P 〈 0.05） levels of CO2, （8.3%） and CH4 （5.1%）, compared to the average of the two lower ratios （CO2, 5.3% and CH4, 3.3%）. Molar proportions of VFA, CO2 and CH4 in the gut were in the order of VFA 〉 CO2 〉 CH4, at 53.0%, 28.6% and 18.4%, respectively, and CO2 and CH4 combined represented 47% of total gas.