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目前新建火力发电厂的烟气脱硫多采用石灰石-石膏湿法脱硫工艺,湿法烟气脱硫系统不设置烟气加热系统(GGH)时,烟气进入烟囱的温度只有50℃左右,湿度大并处于饱和状态。处理后的烟气中SO2含量大大减少,但对烟气中造成腐蚀的主要成分SO3脱除效率并不高,一般还含有氟化氢和氯化物等,在饱和烟气中,将形成腐蚀强度高、渗透性强的低温高湿稀酸型物质,对烟囱结构和防腐设计提出了严格的要求。
套筒式和多管式烟囱作为湿烟囱常用的结构型式,钢内筒一般采用普通钢、耐硫酸露点钢和钛钢复合板,支承方式主要有自立式和悬挂式。自立式即钢内筒承受自身重量,整体性较好,但用钢量较大,经济性差。悬挂式分为整体悬挂式和分段悬挂式,整体悬挂式将整段钢内筒直接悬挂在烟囱顶部的承重平台,而分段悬挂式则将钢内筒烟囱分成多段,分别悬挂在各承重平台,各段之间设置膨胀伸缩节连接。相比自立式钢内筒,采用悬挂式的钢内筒截面以受拉为主,充分利用了钢材的材料特性,避免了自立式钢内筒钢板易于局部压屈的缺点,因而其厚度大为减小,可明显降低总用钢量,同时高耸烟囱的强度主要受风荷载控制,筒身弯矩大、轴力小,钢内筒悬挂在外筒上,也有利于提高外筒的受力性能。据已建的分段悬挂式烟囱的运行情况反馈,伸缩节的防渗漏防腐处理是分段悬挂式烟囱的突出问题。而采用整体悬挂式,则可以有效避免膨胀伸缩节的渗漏问题,且用钢量更省。
对于分段悬挂式钢内筒的设计和施工,国内已有不少学者[1,2,3,4,5,6,7]进行了相关的研究,但整体悬挂式钢内筒的筒身、膨胀伸缩节、悬挂平台的设计与施工均要复杂很多,目前应用的工程实例较少。刘付浩[8]进行了整体悬挂式烟囱设计的尝试,张凌伟[9]则提出了内、外筒相互作用影响下的钢内筒内力计算方法,吴留恩[10]采用液压提升倒装法完成国内首座整体悬挂式烟囱钢内筒的施工。某发电厂的烟囱钢内筒采用悬挂式的超长内筒,其作为我国目前单机容量最大的高效超超临界火电机组工程,内筒直径大,悬挂段长,国内少见,本文对其关键设计难题进行探讨,以供类似工程参考。
Structural Design of Entire Suspension Steel Inner Cylinder in Chimneys
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摘要:
[目的] 整体悬挂式烟囱的钢内筒截面以受拉为主,接头少利于防渗漏,具有受力合理,用钢量省,利于烟囱运行和维护的优点,但整体悬挂式钢内筒的筒身、膨胀伸缩节、悬挂平台的设计与施工均要复杂很多。为解决悬挂平台、钢内筒、止晃点及膨胀伸缩节的设计关键问题,提出了一种整体悬挂式烟囱钢内筒的结构设计方案。 [方法] 通过具体工程实例,结合计算分析,最终确定采用桁架式悬挂平台结构以及新型的悬挂点设计方案,建立了考虑悬挂平台转动刚度的钢内筒连续梁计算模型,采用承插式膨胀伸缩节,并用密封液进行封闭。 [结果] 结果表明:该设计方案受力合力,满足烟囱的密封性和耐久性要求,且便于施工和缩短工期。 [结论] 通过对整体悬挂式烟囱钢内筒结构设计问题进行探索和研究,所采用的设计方案取得了较好的经济效益,可为类似工程提供参考。 Abstract:[Introduction] The section of the entire suspension steel inner cylinder in chimney is mainly in a state of tension, and the joints are less conducive to leakage prevention. The design and construction of the entire suspension steel inner cylinder, expansion joint and suspension platform are much more complicated. In order to solve the key problems in the design of suspension platform, steel inner cylinder, guide point and expansion joint, a structural design scheme of integral suspension chimney steel inner cylinder was proposed. [Method] Through specific engineering examples, combined with calculation and analysis, the truss suspension platform structure and new suspension point design scheme were finally determined, and the calculation model of continuous beam considering the rotational stiffness of suspension platform was established for steel inner cylinder. The socket expansion joint was adopted and sealed with sealing fluid. [Result] The results show that the design scheme meets the requirements of sealing and durability of chimney, and is convenient for construction and shorten the construction period. [Conclusion] Through exploring and researching the structural design of steel inner tube of entire suspension chimney, the design scheme adopted has achieved better economic benefits, which can provide reference for similar projects. -
Key words:
- entire suspension /
- chimney /
- steel inner cylinder /
- suspension platform /
- guide point /
- expansion joint
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