Process Integration Methods in Pulp and Paper Industry for Water Usage Reduction

The Pulp and Paper industry has struggled to solve problems related to high water consumption. One alternative is to use tools like Process Integration (PI) which includes "Water Pinch", a graphical method, and mathematical programming, which can be used to optimize the water circuit. In a case study in Brazil these two techniques were applied. Data was collected in real time from an integrated thermo mechanical pulping and newsprint mill and then used to develop a simulation that served as the base case model. The analysis is based on residual water reuse in other parts of the process under constraints of concentration limits of dissolved solids and fine fibers. The concentration limits of contaminants were frequently exceeded as shown when recalculated by simulation. Therefore, the results had to be corrected before they became valid. So if the predicted value for reduction of fresh water consumption is 31%, in actual fact is only 23%, which is still a good result.