Abstract: The present invention relates to a method for the removal of mercury from a gas stream. The method is characterized in that at a temperature above 170° C. the gas stream is contacted with a sorbent that as the active component is comprised of a mixture of substantially silica-alumina compounds and/or calcium compounds. According to a preference, the sorbent is kaolin, that may or may not be in the dehydrated form of meta-kaolin and is optionally obtained by thermal conversion of a material chosen from paper waste or residue from the paper industry. By this method it is possible to remove mercury at temperatures higher than room temperature. The invention also relates to a method for the removal of mercury from a gas stream, wherein the gas stream is contacted with a sorbent at a temperature above 50° C., which sorbent comprises as active substance a mixture of substantially silica-alumina compounds and/or calcium compounds, as well as with an oxidator.

Abstract: The invention relates to a method of improving a material comprising a pozzolanic component. According to the invention the material is treated with an aqueous liquid resulting in treated, calcium-depleted material and a calcium-enriched aqueous solution, which are subsequently separated.

Abstract: A method of making a hydraulic material which contains metakaolinite and calcium hydroxide from a kaolin-containing compound. The method is performed in a fluidized bed installation having a freeboard under conditions such that the amount of calcium oxide formed is minimized. Preferably, the method is performed at a fluidized bed temperature of 780.degree. C. and a freeboard temperature of no more than 780.degree. C. By minimizing the amount of calcium hydroxide formed, the use of an additional installation for converting calcium oxide to calcium hydroxide is avoided. The starting material is typically waste paper and other residues from recycling of waste paper for reuse in the paper industry. The product may be used to form concrete having a high compression strength.