Life Cycle Analysis applied to acrylic acid production process with different fuels for steam generation

Acrylic acid, one of the most important monomers, has a wide range of uses e.g. in the paints adhesives, textile finishing, leather processing or super absorbents. The production process from propylene is well known and used at industrial scale in the USA, Europe, and Asia. The present paper focuses on the evaluation of the environmental impact of the acrylic acid production process from propylene. Steam is a major raw material in the process under study, consequently different paths to obtain steam are investigated. The process was simulated using commercial software (Aspen Plus, PROII). A productivity capacity of 50,000 tones/year of acrylic acid has been considered. The environmental assessment, evaluated using Life Cycle Analysis method, depends on the material and energy balances generated by simulations. The present work uses a cradle-to-grave approach. The functional unit, to which all the environmental results for the cases under study are reported, is one tone of acrylic acid produced. The boundaries of the system cover: i) acrylic acid production; ii) upstream processes for example catalyst and molten salt production; steam production using various fuels (e.g. natural gas, anthracite, lignite, heavy fuel oil, light fuel oil and biomass) and iii) downstream processes for example: acrylic acid and acetic acid transport to other chemical plants for further processing. The CML (An LCA method developed by the Center of Environmental Science of Leiden University) 2001 impact assessment method was used for comparison between different case studies. The best value for Global Warming Potential (GWP) e.g. 1094.5 kg CO2-Equiv./tone is obtained when biomass is used to generate the steam required by the process. For other indicators such as Acidification Potential (AP), Photochemical Oxidation Potential (PCOP) and Eutrophication Potential (EP), the best value is obtained when steam is generated from natural gas. A sensitivity analysis of the environmental impact categories using the different combination of natural gas and biomass was also investigated. The study investigates also the association of the post-combustion aminebased carbon capture technologies with the conventional acrylic acid production process. Such association decreases the value of some environmental impact categories (e.g. GWP) while other impact categories are increasing e.g. AP, Human Toxicity Potential (HTP), Terrestrial Ecotoxicity Potential (TETP).