真空法启动降低锅炉蒸汽侧金属表面氧化膜温差试验研究

单元机组一般采用压力法冷态启动。超临界机组锅炉采用压力法冷态启动，必然出现对流受热面干烧升温再通蒸汽冷却现象，氧化膜会承受100℃左右的冷却温差产生的热应力，而较大热应力可能导致氧化膜剥落。采用真空法启动，锅炉点火前受热面内即流通低温饱和蒸汽，可有效降低启动过程中过热器管表面氧化膜的温差。在湖南华电长沙发电有限公司2号机组锅炉上进行了真空法启动试验，取得了较好的效果，锅炉点火前后受热面温差明显减小，有效减少了氧化膜脱落风险。该方法无需设备改造，操作简单可靠。

Experimental Study on Reducing Thermal Stress of Steam-Side Oxide Scales by Vacuum Method

Generally, the generation unit is started from cold state by means of pressure method. However, when this method is applied in supercritical boiler, it is inevitable that convective heating surface will be heated dry without steam and, then cooled down with steam. As a result the oxide scales will have to withstand the thermal stress from about 100℃ cooling temperature difference, which can cause the oxide scales flaking. In this paper, the vacuum method is adopted to start the unit. The low temperature saturated steam flows the heated surface of the boiler before ignition, which can effectively avoid the peeling off of the oxide scales during the startup process. corresponding experimental study is carried out in No. 2 boiler in Changsha Power Station Co., Ltd of Hunan CHD and satisfactory results are obtained. The temperature difference of the heating surface is significantly reduced before and after the ignition of the boiler, which effectively diminishes the risk of oxide scales flaking. The method is simple and reliable with no equipment modification needed.