Inegrated Ash Monitoring System for Control of Fouling in Coal-Fired Boilers

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17 A historical plot of the percentage fouled of the economizer is shown in Figure (IS). Sootblowing was only partially effective as it reduced the degree of fouling from 25% to 17%. This is typical of the effectiveness of all economizer sootblows. It is probable that the sootblowers do not reach all of the large surface area of tubes end the tenacity of the deposit combines to prevent complete cleaning. Figure 15. Percent fouled in the economizer. Figure (16) shows hOti the economizer gradually fouls over time. The April 30 data shows the economizer was regularly fouling to the extent of 10% and then cortpletely cleaning. The economizer was clean prior to this time because the boiler had just undergone a maintenance shutdown. The plot for May 12 shows that after less than two weeks of operation, sootblows were no longer completely effective, i.e. soot blowers cleaned the bank from 25% to only 15%. In the September period which was a particul arly high foul ing period, the economi zer was generally 30% fouled with economi zer sootblows having very little effect on the state of cleanliness.