覆膜栽培对于保温、保墒、保肥,促进大田作物早熟增产有着明显效果.为了使覆膜栽培更好地发挥作用,常在覆盖薄膜前施足底(基)肥,提高供肥能力.但覆膜施用底肥,效果往往有很大差异,其中原因有以下几点: 一是有些农户为了急于求得高产,过量施用底肥,造成植株陡长.

Based on the mechanism of reducing NO_x emission with staged-air combustion technology, the numerical simulation using CFD (FLUEBT6.0) software on the combustion process in the cold and hot states with staged-air technology for a 330MW coal-fired power plant and the comparison of simulated NO_x emission values with the tested NO_x emission data were conducted. The results indicate that aerodynamic distribution is symmetrical in a utility boiler with opposed-installation whirl burners. The temperature first rises along with furnace height and then slightly decreases. In the combustion zone, the temperature and NO_x concentration are the highest, while the oxygen concentration is the lowest. Without reconstruction and additional equipment cost, the staged-air technology can reach a low NO_x emission by regulating some burners for the existing boilers.

Through coal, slag, botton and fly ashes sampling from a 300MW utility boiler at the rated load and analysis of total and hexavalent chromium contents of those samples.the total chromium quantity distribution in coal and its combustion products was derived by means of mass balance methods. Characteristics of chromium transformation in a large-scale utility boiler is,therefore,analyzed and discussed. During coal combustion,the total chromium quantity in flue gas to raw coal is about 84% .The total chromium quantity in slag, bottom ash is about 1.1%, 0.6% respectively. The total chromium quantity in fly ashes can be distributed as 11.1% in No.l ESP outlet, 1.2% in No.2 ESP outlet, 1.3% in No.3 ESP outlet.In combustion products,the chromium in flue gas takes a very high ratio.

在对某300MW燃煤电站锅炉的煤、渣、底灰、飞灰进行取样后,通过对煤样、灰样、渣样中的汞进行定量测量,并借助于质量平衡分析方法计算烟气中汞的浓度,获得了煤在大型电站锅炉中燃烧时汞污染物的分布特征及其排放特性.图5表1参9

After coal, slag, bottom ashes and fly ashes from a 300 MW utility boiler at the loads of 300 MW, 250 MW, 200 MW were sampled, mercury contents of those samples are measured. Mercury distribution in coal and its combustion products were therefor understood. And characteristics of mercury enrichment in fly ashes at various boiler loads are further discussed and analyzed.

高炉煤气是钢铁产业的副产品，其特点是煤气产生量大、可燃物含量少、发热量低，以及燃烧性能差等.在对钢铁企业能源消耗结构和高炉煤气特性火焰传播速度与过量空气系数关系分析研究的基础上，介绍了有效合理利用低热值高炉煤气用于燃气-蒸汽联合循环发电和燃煤-燃气混烧锅炉发电所出现的问题及实际运行状况，得出了机组稳定运行时高炉煤气性质波动的控制范围.

试验研究了在改动前分隔屏的工况下,四角喷燃锅炉屏式过热器后,左右速度偏差沿水平烟道高度方向的分布特性,改动分隔屏的各工况分别为:向左侧偏转30°、45°、60°;全部偏置在右侧以及各个前屏向左侧偏转不同角度的组合式偏屏.研究表明,屏式过热器后左右速度的偏差主要集中在水平烟道的下半部区域.在改动屏的各工况中,均能使这一区域的速度偏差系数有不同程度的下降,与标准运行工况相比,下降幅度为20%～50%.

为改善由于四角喷燃锅炉残余旋转引起的水平烟道速度分布不均匀的状况,介绍了一种将分隔屏偏置的新方法.试验表明,将分隔屏组合偏置,效果最佳,可使水平烟道内速度不均匀系数下降达85%.将分隔屏分别偏置30°、45°和60°,水平烟道内速度不均匀系数可下降30%左右.因此表明文中提出的方法是可行的,它为提高大型机组火电厂运行的安全和经济水平,防止超温爆管事故的发生提供了一种新的措施.

某300MW逆时针切向布置燃烧器锅炉在不同二次风反切方式下分隔屏向左偏置一定角度时,炉膛、烟道气流流动特性模型试验和数值模拟的研究结果表明:燃烧器上半部分二次风递增反切分隔屏偏置一定角度的燃烧技术能显著改善烟道偏流现象,可防止过大热偏差引起高温对流受热面超温、爆管,同时能降低炉内燃烧器区域结渣程度、减少NOx生成,且改造方便、效果明显.图10表1参5

Tangential firing system is widely used on utility boilers since it can burn various coals with a complete combustion. However, inherent gas imbalance on horizontal gas pass often brings about overheating and bursting of convection heating surface tubes, which affects boilers' safe and economic operation directly. Cold flow modeling experimental results of a 300 MW utility boiler show that biasing superheater division panels not only can eliminate gas imbalance effectively but also has no effect on furnace aerodynamics, which is salient to overcome heat deviation and convenient to retrofit for tangentially fired utility boilers.