In this work, the conventional scenario of the black liquor (BL) concentration and combustion is compared with the BL upgrading gasification process for ammonia production. The chemical processes synthesis, modeling and simulation are performed by using Aspen Plus® software. The determination of the heat recovery and the solution of the energy integration problem is handled by a mixed integer linear programming model. An incremental financial analysis incorporates the uncertainty related to the acquisition and selling costs of the feedstock and fuels produced and carbon taxation by using the Monte Carlo method. As a result, the incremental financial analysis found that only the integrated pulp and ammonia production route with partial electricity import may economically outperform the conventional kraft pulp mill for moderate carbon taxations (40-90 EUR/tCO2), depending on the interest rate adopted. In this regard, middle-to-high carbon taxations may render ammonia co-production attractive in the Brazilian context of a highly renewable electricity mix.