Neural network to cut pollutants?
22 Aug 2002
The US Department of Energy has signed an agreement with Tampa Electric Power Company to demonstrate how advances in 21st century computer technology can make a 1970s coal-fired power plant run cleaner and more efficiently.
According to a statement, the agreement calls for engineers to install a new neural network-driven computer system in one of the boiler units at the Big Bend Station near Apollo Beach, Florida. Designed to prevent soot from building up in coal plant boilers, the system will also enable the plant to reduce the emission of pollutants such as nitrogen oxides.
The $2.38 million project is the latest in the Energy Department's efforts to apply the capabilities of advanced computing to the operation of coal-fired power plants. Already, an artificial intelligence system pioneered in the department's Clean Coal Technology Program is being used commercially to fine-tune the performance of low-NOx burners.
Now the capability of new computer software to recognise patterns and make decisions accordingly is being applied to other aspects of a power plant's operation.
In the Big Bend project, a computerised system will replace conventional, manually operated 'sootblowers.' Sootblowers use high-velocity jets of steam or air to blow carbon residue off the inside surfaces of coal-fired boilers. A typical mid-size coal-fired power plant can have a hundred or more sootblowers. Most operate on an automated, time-based sequence and indiscriminately clean the boilers whether they are dirty or not.
In a 445-megawatt unit of the Big Bend plant, engineers will install a 'Neural Network-Intelligent Sootblowing' process. The system is designed to recognise soot build-up and manage the sequence of cleaning based on the actual 'real time' need. Moreover, it can detect which specific sections of a boiler need cleaning and activate an individual blower or sets of blowers for just that area.
The result is optimal cleaning of the coal boiler's tubes and interior walls. But the benefits are said to extend well beyond just a clean boiler.
Because heat is transferred more efficiently in a clean boiler, the plant's overall power efficiency is improved, which equates to more energy sent to the grid. In the Big Bend project, electricity output will be raised by two percent.
There are also said to be environmental benefits. Although coal plants have devices to capture soot in the flue gases exiting boilers, the more soot that can be collected inside the boiler means that less finds its way up the smokestack and potentially escapes into the air.
The most significant air quality benefit will be a reduction in nitrogen oxides (Nox). In a boiler, some NOx comes from nitrogen in the coal, but a large amount can also be created when temperatures spike high enough to cause nitrogen in the combustion air to recombine into the pollutant.
By keeping the inside surfaces of the boiler clean, heat from coal combustion can be distributed more evenly, preventing the sudden formation of hot spots that can produce NOx. At the Big Bend plant, the new sootblowing system is expected to reduce NOx by an additional 30 percent.
The new technology is also expected to extend the life of the power plant's equipment, saving the utility and ratepayers expensive maintenance and replacement costs.
