| 摘要 |
Steam (preferably clean steam) having less noncondensible gases than steam produced by conventional black liquor flashing is produced from hot black liquor from a digester of a pulp mill. A heat exchanger (19) is utilized and the hot black liquor is passed through the heat exchanger in heat exchange contact with an evaporable liquid (18), preferably clean water. After the water is heated in the heat exchanger it is flashed in at least one flash tank (21, 22) where the heat exchanger is a liquid-to-liquid heat exchanger. The heat exchanger may alternatively include an evaporator (27) (such as a falling film evaporator) in which case the black liquor is passed through an eductor (26) before it enters the evaporator. Alternatively, the heat exchanger may be one or more boilers (42, 43), su ch as kettle boilers, in which case the black liquor preferably passes through a cooler (44) after the boilers. Heat energy and turpentine recovery are also maximized.
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