Techno-economic assessment for black liquor concentration system of chemical pulp integrating mechanical vapor recompression

Abstract

Mechanical vapor recompression (MVR) is mostly used for the evaporation of black liquor in chemical pulp production process because of low operating cost, high thermal efficiency and small footprint. This paper designed a black liquor concentration system of Chemical pulp integrating MVR (BLCS-MVR), modeled the energetic and economic requirements of BLCS-MVR. The results found that the total cost increases as the solid content of black liquor leaving MVR segment increases, MVR has lower operation cost than the traditional evaporation technology when the solid content of black liquor after MVR segment is less than 37.5%. Compared with the traditional evaporation system, the total energy cost of new system is reduced by 21.0%, and the latter three-effects of the traditional six-effect evaporation can be replaced by MVR system. Steam consumption can be reduced by 48.2%, and the payback period is only 2.72 years. Sensitivity analysis showed the steam price impacts the economy of BLCS-MVR most, followed by the electricity price, the investment cost and the production scale. This research provides a theoretical basis and technical reference for the application of MVR in the black liquor concentration of chemical pulp, which contributes to the realization of “carbon neutralization”.