Case 1

This boiler is a CE wall fired unit with a gross load of 650 MW burning Powder River Basin Sub bituminous coal. The installation of a fully automatic Intelligent Sootblowing system improved boiler efficiency by 1.7% . As well as the efficiency improvement a temperature reduction of 22°C was seen at the economiser gas outlet and a reduction of 15°C was seen at the air heater gas outlet. Also side to side temperature variation was also eliminated.

This boiler is currently the subject of a demonstration project into Intelligent Sootblowing by EPRI.

Case 2

This boiler is a CE tangentially fired unit burning Lignite with the latest technology low NOx burners and overfired air. In this case automating the sootblowers in an intelligent manner provided a sootblower operations reduction of 50% whilst actually increasing the furnace heat transfer.

Case 3

This boiler is a 900 MW CE tangentially fired, split furnace, super critical unit burning Lignite. The unit is fitted with across the boiler water cleaning devices which are automatically controlled by an Intelligent Sootblowing system. Introduction of the ISB provided an additional 30 MW capacity while reducing the NOx emissions by 15-20%. A reduction in FEGT of 85°C was also seen.

Case 4

This is a B & W opposed wall fired unit. It can be seen from the graph below that the furnace had a high FEGT and low heat rate when baseline investigations took place. Following the installation of an ISB system and training sessions for the operators this situation the boiler heat rate increased by 22% and the Boiler exit gas temperature fell be 19°C .

Case 5

This boiler is a CE 500MW unit fitted with Low NOx burners. The furnace has a central division wall and burns bituminous coal.

When a full furnace sootblow is initiated the overall heat transfer will increase. This sudden, large increase causes corresponding reductions in backpass temperatures. This can be seen in Fig 1. Each time a full furnace sootblow takes place the superheater and reheater temperatures (and of course all other backpass temperatures) fall. These perturbations in temperature inevitably cause efficiency loss.

Also as the furnace exit gas temperature decreases attemporation spray rates will increase as in Fig 2.

If the furnace is cleaned in an intelligent manner, and only in the regions that need cleaning, this disruption of furnace exit gas temperature is much lower and the efficiency losses are also smaller.

Installation of an Intelligent Sootblowing System also eliminated a serious drum imbalance problem in this boiler.

Conclusions

The financial benefits of Intelligent Sootblowing have been proven beyond doubt by organisations such as EPRI and by real time system implementation in power plants. Although this type of system is virtually essential for lower ranked coal (Lignite, Sub bituminous) fired plants in order to compete successfully on price and availability it also provides many advantages to users of higher ranked coals.

As more markets become deregulated competition will become a driving force in virtually all management decisions. Cost reduction and maximum availability will attain a live or die type of importance. Systems such as ISB, where a current operating method (probably very ineffective in its¹ current form) can be automated and provide cost and efficiency benefits in many diverse areas should be part of the thinking of senior engineering management.

Improvement of the performance of existing plant by optimising its operation is a relatively low cost option. In some cases payback times can be in days.