Abstract: This invention is directed to a method for removing calcium material from a substrate or catalytic converter. In particular, this invention is directed to a method for removing calcium material, particularly in the form of calcium-containing fly ash, from a substrate using a partially protonated or non-protonated polycarboxylic acid treatment material.

Abstract: The invention relates to a method for the regeneration of deNOx catalysts with a reduced activity caused by the accumulation of phosphor and phosphorous compounds. The method is characterized in that the catalysts are treated with an essentially aqueous solution of water-soluble alkaline reacting alkaline earth salts, ammonium hydroxide, or alkaline reacting ammonium salts, or water-soluble organic amines with an approximate pK value ranging between 2.5 and 5.5 and that the excess alkali is neutralized by subsequent treatment with inorganic or organic acids.

Abstract: This invention is directed to a process for removing a catalyst inhibitor from a substrate or catalytic converter containing at least one nitrogen oxide (NOx) catalyst using a phosphoric acid composition. The process is particularly suited for removing the catalyst inhibitor, arsenic, from a fly ash-coated substrate or converter. A substantial amount of catalyst inhibitor can be removed from a fly ash-coated catalytic converter without removing a significant portion of one or more of the NOx reduction catalysts in or on the substrate.

Abstract: The invention relates to a method for regenerating denox catalysts having an increased SO2/SO3 conversion rate as a result of the cumulation of iron compounds, and is characterized in that the catalysts are treated with an essentially aqueous acid solution, preferably having a pH between 0.5 and 4, and with an addition of antioxidants.