烟气SO3监测控制冷凝法采样方法

烟气SO₃采样多采用控制冷凝法，因SO₃易凝结，捕集率仅有80%左右。参照GB/T 21508-2008所规定的控制冷凝法，对影响SO₃捕集率的主要因素，如蛇形盘管内径及总长、抽气流量、采样枪温度等进行实验研究，得到最佳盘管型式及控制参数。研究结果表明：采样枪的加热温度应≥280 ℃；对于内径4 mm的蛇形盘管，最佳抽气流量为20 L/min，蛇形盘管总长应为240 mm。在最佳条件下，控制冷凝法SO₃捕集效率可达97%以上，能够满足现场SO₃测试需要。将研究成果应用于某600 MW超低排放机组的监测，得到了烟气排放不同阶段SO₃排放浓度及各大气污染物治理设施对SO₃的脱除效率。

The Controlled Condensation Method for the Sampling of SO3 in the Flue Gas

Controlled condensation method was adopted mostly for SO₃ sampling in the flue gas, because SO₃ is prone to condense and its capture rate is only about 80%. Based on the specifications of controlled condensation method in GB/T 21508-2008, the experiment of SO₃ capture was carried out. Through the experimental studies on the main factors affecting the capture rate of SO₃, such as the size and total length of serpentine coil, the extract flow as well as temperature of sampling, the best coil type and control parameters were obtained. The results show that, the heating temperature of the sampling gun should be at least 280℃. For serpentine coil with the inner diameter of 4 mm, 20 L/min is the optimal pumping flow rate, and the length of serpentine coil should be 240 mm. Under the optimal conditions, the SO₃ capture efficiency can reach 97% or higher, which will meet the needs of SO₃ field test. Finally by taking advantage of this sampling method, the SO₃ concentration in flue gas at each stage was measured and the SO₃ removal efficiency of various air pollutant control equipment from a 600 MW ultra low emission unit was calculated based on the measurement data.