Method for generation of clean steam in a continous digester system

The invention relates to an improved method for generating clean steam in a digester plant of a chemical pulp mill. By feeding a steam-to-steam converter (SSC) with venting steam from a black liquor flash tank (FT) as well as venting steam from chip steaming (SV) could the volume of clean steam produced be increased by over 40-50%， and to such an extent that the volume of clean steam covers the needs for preheating of chips in the digester system also in severe operational conditions. The total consumption of clean steam from the steam net of the mill may be reduced and used for other purposes such as electricity production， which meets the requirements for converting the pulp mill to an environmental friendly pulp mill.

本发明公开了一种用于化学制浆厂蒸煮工段制备清洁蒸汽的改进方法。通过向汽-汽转换器（steam-to-steam converter，SSC）通入源自黑液闪蒸罐（black liquor flash tank，FT）的闪蒸汽与木片汽蒸（chip steaming，SV）工序产生的闪蒸汽，可使清洁蒸汽的产量提升40%~50%以上；即使在严苛运行工况下，清洁蒸汽的供应量亦可满足蒸煮系统内木片预热的全部需求。同时，该方法可降低该厂蒸汽管网的清洁蒸汽总消耗量，将节约的清洁蒸汽用于发电等其他用途，契合化学制浆厂向环境友好型制浆厂转型的发展要求。