某660 MW超临界锅炉深度调峰过程中分隔屏超温计算分析及改造方案研究

Calculation and Analysis of the Platen Superheater’s Over-temperature During a 660 MW Supercritical Boiler’s Deep Peaking Shaving and Research on Modification Plan

针对660 MW超临界褐煤锅炉分隔屏实炉数据分析发现,在175 MW负荷下,分隔屏的超温报警主要发生在屏3、屏4靠近炉内的管子。为解决分隔屏超温报警问题,采用流动网络系统法,结合质量、能量和动量守恒方程建立了分隔屏水动力计算数学模型,提出添加节流圈以及升级管子材料两种改造方案。对分隔屏进行回路及管段划分,采用175 MW负荷实炉测量数据反推计算得到炉内实际热偏差,对低、中、高负荷下添加节流圈与升级材料为Super304H的分隔屏出口汽温进行计算。计算结果表明:添加节流圈后分隔屏出口汽温偏差变小,且屏3、屏4出口汽温降低至材料TP347H报警温度以下;升级材料为Super304H后分隔屏出口汽温均小于材料的报警温度,分隔屏可安全运行。对添加节流圈以及将材料升级为Super304H两种方案进行壁温计算及强度校核,结果显示两种改造方案在各个负荷下,壁温以及强度均是安全的。为给锅炉运行留出更大的安全裕度,建议在分隔屏最后一片屏上添加节流圈的同时将材料由TP347H升级为Super304H。

Analysis of the furnace data for the platen superheater of the 660 MW supercritical lignite fired boiler revealed that,under 175 MW load,the over-temperature alarm mainly occurred at the tubes close to the flame in the 3rd and 4th platens.To address this issue,a mathematical model to calculate the hydrodynamics of the platen superheater was established using the flow network system method,combining conservation equations for mass,energy,and momentum,and two modification plans were proposed:adding a throttle orifice and upgrading the tube materials.The platen superheater was divided into loops and tube sections,and the actual thermal deviation in the furnace was calculated using measured data at 175 MW load.The outlet steam temperatures of the platen superheater were then calculated with a throttle orifice and upgraded Super304H material under low,medium,and high loads.The calculation results demonstrate that the addition of the throttle orifice reduces the deviation of the outlet steam temperature for the platen superheater,ensuring that the outlet steam temperature for 3rd and 4th platens remains below the alarm temperature of TP347H material.Similarly,upgrading the material to Super304H leads to that the outlet steam temperature for the platen superheater is below the alarm temperature,thus ensuring safe operation.The tube wall temperature calculations and the strength checks were carried out for both modification options,and the results indicate that the wall temperature and strength are safe under various loads.To provide a greater safety margin for boiler operation,it is recommended to add a throttle orifice to the last platen and at the same time upgrade the material from TP347H to Super304H.