Solving corrosion issues in combustion biomass
Until now temperatures in biofuel boilers have not been higher than 480ºC due to material constraints. The problem with low temperatures, however, is that they are not efficient in terms of power generation. Therefore finding a way to allow for an increase in steam temperatures while also increasing corrosion resistance meant possibly increasing power generation efficiency as much as 10%. Additionally, it meant significant savings in maintenance costs since superheaters would become more durable for longer periods. The way to achieve this was to find a proper additive and an appropriate material to use since wood and waste-wood fuels cause an increase in superheater corrosion. Thus boiler tests were conducted by spraying ammonium sulphate into the flue gas after combustion, which in turn converts gaseous potassium into potassium sulphate, a much less corrosive compound. In fact, both corrosion rates and deposit growth rates were reduced by 50%. Probe tests have also shown that another way of reducing corrosion in superheaters is by using the right kind of steel such as austenitic stainless steel. As a result of such measures, superheaters are bound to become more durable and efficient in the future.
