净化厂换热器腐蚀影响因素及原因分析

Analysis of influencing factors and causes of heat exchanger corrosion in purification plant

关键词:  换热器  循环水  腐蚀  腐蚀防护

Key words:  heat exchanger  circulating water  corrosion  corrosion protection

摘要:

目的 分析川渝某净化厂换热器的腐蚀原因及影响因素,探讨解决措施。方法 通过微观分析换热管束泄漏的原因,采用旋转挂片法室内考察了换热器内循环水中的Ca²⁺、HCO-₃、Cl-、SO2-₄对腐蚀的影响。结果 换热管束泄漏是由腐蚀导致的,腐蚀从管束的内表面开始,逐渐形成腐蚀孔,最后导致换热管出现腐蚀泄漏。循环水中Ca²⁺、HCO-₃对水质的腐蚀性影响较大,当循环水中的ρ(Ca²⁺)低至44 mg/L时,系统中碳钢的腐蚀速率高达1.05 mm/a。结论 为了防止管束发生腐蚀失效,需要加强水质控制,提高系统的Ca²⁺含量、碱度,或者更换耐蚀性更高的材质。 

Abstract:

Objective The cause for corrosion in heat exchangers at a single natural gas purification plant located in Sichuan-Chongqing area was studied as well as the influencing factors so as to reach the technical solutions. Methods Microscopic analysis was conducted to study the cause for leakage in the tube bundles while the influences of Ca²⁺, alkalinity, Cl- and SO2-₄ in the circulating water on corrosion rate were investigated by rotary hanging plate method. Results The leakage in the heat exchange tube bundle was caused by corrosion. During the process, corrosion occurred first at the inner surface of the tube bundle, which then gradually grew to form corrosion holes and finally led to the leakage. Ca²⁺ and alkalinity were revealed to be closely related with the corrosivity of the recirculating water:when the Ca²⁺ concentration was as low as 44 mg/L, the corrosion rate of the carbon steel could reach as high as 1.05 mm/a. Conclusion sIn order to prevent the corrosion failure of tube bundle, it is necessary to enhance the water quality control by increasing the Ca²⁺ concentration and alkalinity in the system or using material with higher corrosion resistance.