Reducing superheater corrosion in wood-fired power plant

One of the major drawbacks to the combustion of 100% wood and waste wood fuels in power station boilers is the increase in the fouling and corrosion of superheaters, which increases operation and maintenance costs. Wood fuels have a high content of potassium and chlorine, but they contain very little sulphur compared to fossil fuels. To combat corrosion, boiler tests have been performed with ammonium sulphate which is sprayed into the flue gases after combustion but before the superheaters and effectively converts gaseous KCl into potassium sulphate, K2SO4. This is much less corrosive than KCl. Long-term probe measurements showed that the corrosion rates were reduced by 50%. This concept, together with an instrument for measuring alkali chloride levels in the flue gas has been patented and is known as "ChlorOut". Probe tests with different steels showed that superheater corrosion can also be greatly reduced by the choice of the right material.