The hazardous manual cleaning of heavily clogged boiler pipes can become a thing of the past, thanks to a microprocessor controlled pipe cleaning attachment developed by EUREKA project E! 3237. But as well as boosting boiler efficiency, it also offers industry far lower cost boiler solutions for heavy-duty applications that were until now, unavailable.
Steam is still one of the best ways to transfer heat at a constant temperature, and fire tube steam boilers are widely used in industrial applications, all over the world. The concept is simple, hot gases travel through tubes or pipes placed in water, and their heat is transferred to the water surrounding the pipes. However, using heavy or solid fuels such as coal or biomass to heat the gases causes boiler pipes to clog up and become dirty. This continuously reduces the boiler's efficiency and in the worst cases, can bring it to a standstill. Cleaning fire tube boilers is an arduous and intensive task considering there are generally over 100 pipes to clean. It involves a loss in production, as the boiler has to be taken out of operation. A long brush is used to scrape each pipe out by hand, exposing the cleaner to the residue of noxious and hot gases in the tubes.
"Without EUREKA funding it wouldn't have happened."
Optimum Environmental Technologies B.V., The Netherlands
Dutch firm Optimum Environmental Technologies and French company Maguin, partners in the project, have developed a system which will continuously monitor boiler performance and automatically start a cleaning cycle. The loss of efficiency from fouled or clogged pipes, leads to a change in gas temperature inside the pipes. When a particular rise in stack temperature is detected, a heat resistant mechanical arm is launched to systematically insert a brush into each pipe and clean it, while the boiler is still in operation.
The type of brush and the way the brush is fed through the tube depends completely on the fouling characteristics. The degree to which fouling occurs depends on the type of fuel used. Using natural gas causes no fouling at all, but the use of heavy fuels can mean the boiler losing up to 15% or more of its efficiency and needing to be cleaned as frequently as once a week, sometimes even once a day. The project partners have designed a set of specially shaped heat resistant brushes to take care of all eventualities.
Typical working temperatures are in the region of 400 degrees centigrade and the whole cleaning cycle can be completed in around 45 seconds per tube.
The system is controlled by a programmable logic controller (PLC). This is a microprocessor-based device like a desktop computer which can be accurately programmed to monitor and launch the cleaning cycle for each individual boiler. Unlike a desktop computer, the PLC is designed for extended temperature ranges, dirty or dusty conditions. It is immune to electrical noise, and resists to vibration and impact. The main difference with a general computer is the particular input and output arrangement. These connect the PLC to sensors which control the positioning system and read temperature indicators and actuators, which operate the electric motor and the cleaning arm's movements.
The control system has been developed in close cooperation with Siemens
Nederland and the system is standardised according to the Siemens S7 PLC concept. It can be used with a modem in order to monitor and clean the boiler tubes, remotely, from another room or building. The whole cleaning system has been designed in the form of an add-on unit, to fit on both horizontal and vertical boilers. Although it has been intended for fire tube boilers, the system can also be used for cleaning other types of heat exchangers.
Until this development, the only alternative has been to install water tube boilers, which can be cleaned in-line. Water tube boilers work on exactly the opposite principle, using water in the pipes to heat the gases that surround them. However, they are an expensive alternative costing anywhere between 3 to 5 times more than fire tube boilers, and only operate at high pressures of over 35 bars.
Industrial plants already using fire tube boilers have purchased the innovation as well as new industries which in the past had no option than the more expensive water tube boilers. "Tar production plants and recycling plants in the Netherlands have already installed our system," says Enno Nuy, director of Dutch partner Optimum Environmental Technologies B.V.
As all those involved were small companies, EUREKA was vital for the research and development of our system."
Optimum Environmental Technologies B.V.,
The system has already been granted a European patent, and a worldwide patent is pending. Nuy believes the partners will be set to exploit the mass markets of America and China with a worldwide patent. "In China, the majority of boilers are fire tube boilers using coal. It's a very relevant market for us."
A report by Maguin estimates that, "In Northwest Europe at least 150 boilers per year will be equipped with the APCS [automatic pipe cleaning system]. In other parts of the world the market potential is said to be at least 750 pieces per year, especially in regions like South Africa and the Far East."
However, "Without EUREKA funding it wouldn't have happened," says Nuy. "As all those involved were small companies, EUREKA was vital for the research and development of our system."