Straw quality for its combustion in a straw-fired power plant

ENERGIA HIDROELECTRICA DE NAVARRA, S.A. (Navarra, Spain) is erecting a 25 N M power generation plant using straw for electricity generation. Cereal str aws have proved to be difficult to burn in most existing combustion systems . During the last two years, a study has been carried out in Navarra to inv estigate the possibilities of improving the fuel quality of straw by a redu ction in its K+ and Cl- contents. The simple leaching of K+ and Cl- with wa ter by exposure to natural rainfall in the field resulted in considerable r eductions of these two elements. A reduction in the K+ content of the cerea l plants caused by exposure to natural rainfall has been observed during pl ant ripening (before crop harvesting). Some varieties of straw show lower i nitial K+ contents, making them more suitable for this purpose. There seems to be no clear correlation between the relative decrease in K+ content and the amount of accumulated rainfall. Our results have also shown a very clo se correlation between K+ content and electrical conductivity. The simplici ty of this latter measurement makes this parameter a very interesting optio n to test the straw quality directly in the field. Structural components of the straw were not decomposed during the time when we left the straw in th e field. Finally, the Cl- content in straw was increased when the Cl- dose from the fertilizer was increased, On the other hand, the content of K+ was not influenced by the applied amount of K+ fertilizer. (C) 2001 Elsevier S cience Ltd. All rights reserved.