Effects Of By Sulfur Dioxide Low-temperature Corrosion To Boiler Safety Working

Abstract : Boiler is a pressurized enclosures equipment which different energy, such as fuel electricity and so on, was used to heating up the liquid in the boiler. Therefore, there was some dangerous when boiler running to some extent. The SO2 that produced in the process of boiler working not only endanger the air and soil environment, but also the boiler self. Boiler composed of pot and stove. the main reason of outer-corrosion in pressure-containing part is low-sulphur corrosion. The metal wall of pressure-containing part was becoming more and more thickness, and the safety of boiler under working condition was not ensured. Consequently, it had significant meaning to study the effect of corrosion to boiler, for avoiding and reducing accident, and ensuring and accelerating economic development. According to the data of boiler examining in recent years in Rizhao city, the degree of corrosion by different sulphor content of coal under low temperature to boiler pressure-containing member was studied,in order to offer scientific basis trenchancy data for risk evaluation of boiler safety working. The main results as fallows:1 The analyzing results from 23 coal samples showed that: there was a remarkable difference in coal sulfur content between the different region of the China. The maximum was 4.99, while the minimum was 0.41, and average was 2.13, extreme difference reached 4.58. The contents of sulfur dioxide was different in coal burning at different producing. The difference was less than sulfur content in coal relatively, the maximum was 0.276, the minimum was 0.031 and the average was 0.123, extreme difference reached 0.245. The coefficient of variation of them was not much different, the coefficient of variation of sulfur content in coal was 6.60%, while the sulfur dioxide content in fume was 6.11%. 2 The content of sulfur in coal had remarkable effects on the sulfur dioxide content in fume. The sulfur content in coal had intimated linear correlation with the content of sulfur dioxide in fume. The correlation coefficient was 0.9999. In order to decline the boiler corrosion and environment pollution, the coal which has lower sulfur should be used.3 Under laboratory condition and temperature of 25℃, the corrosion speed of carbon steel was big different under different sulphuric acid concentrations .There was no direct proportion relation between them. With the increasing of the sulphuric acid concentration , the corrosion speed increased first and then declined. The difference between different concentration was remarkable, when the concentration reached 56%, the corrosion speed declined from 76.36 mg?cm-3?h-1 to 8.696 mg?cm-3?h-1 , but after the concentration exceed 60%, the corrosion speed became stable.4 In a certain coal sulfur content and fume.sulfur dioxide content, the temperature should be the main factor that effect the boiler corrosion speed. Because the different corrosion speed, the thickness of tube wall become different and its allowed maximum press also were become different. When the tube wall was thinner than 1.6 mm, the running safety was not be ensured, it must be renewal in time. Besides that, according to the calculation of average corrosion speed, if the tube wall was had thinner or high corrosion speed and could not ensur pass the next safety test , it also should be renewal.