Patent ID: 8512514
Filing Date: 2013-08-20
Classification: D21C

Abstract:
1. A method for generating steam in a digester plant of a chemical pulp mill comprising: producing black liquor in the digester plant; extracting a first stream of black liquor from the digester; generating vapor by evaporating the first stream of black liquor by heating the first stream with fresh steam, wherein evaporated black liquor formed by the evaporation of the first stream is separated from the vapor and the evaporated black liquor has a higher dry-solid content than the dry-sold content of the first stream of black liquor; heating cellulosic feed material in the digester with the generated vapor separated from the evaporated black liquor; extracting a second stream of black liquor from the digester; flashing the second stream of black liquor to generate flashed black liquor and flashed black liquor vapor; combining the evaporated black liquor produced by the evaporation of the first stream of black liquor and the second stream of black liquor before or during the flashing of the second stream of black liquor; introducing the flashed black liquor vapor to at least one heat exchanger to indirectly heat a clean evaporable liquid to produce clean steam from the clean evaporable liquid; and steaming, with the clean steam produced in the at least one heat exchanger, the cellulosic feed material before feeding the cellulosic feed material to the digester plant.