The potential for energy savings when reducing the water consumption in a Kraft Pulp Mill

An existing pulp and paper mill has been studied regarding the reduction of water consumption, and the resulting increased potential for energy integration. When the mill’s hot water consumption is decreased, the live steam demand for the mill also decreases. Also when decreasing the hot water consumption, the quantity and temperature of available excess heat increases. This excess heat can be used for evaporation, thereby reducing the live steam demand further by up to 1.5 GJ/t. A pinch analysis was performed and it was found that when removing pinch violations the hot water consumption is not an important factor any more. Removing all the pinch violations and using the remaining excess heat for evaporation yields a significantly larger energy savings for the mill (4.0 GJ/t). From an economic optimum perspective it is probably most profitable to do a combination of reducing water consumption, removing pinch violations, and use the remaining excess heat for evaporation.