Towards sustainability in conceptual process design: improving sustainability of a crude-oil refinery
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: sustainability, modelling, refinery, CO2 reduction
Chemical design approaches are economic-based while environmental and sustainability issues are considered as constraints and included at a second level of decision. This work contributes to incorporate sustainability in the early-stages of the design procedure. This objective requires a multidisciplinary approach and therefore it integrates various tools (AspenPlus®, Matlab®, SimaPro®…) and several analysis methods (energy integration, NINLP, optimization…) to increase the sustainability of a process. In this way, the application of Life Cycle Assessment (LCA) is motivated by its holistic approach. The main goal of the LCA is to provide criteria and quantitative measures that may be used to compare the environmental merits of different process operation and design alternatives.
The methodology is applied to re-design a petroleum refinery (preflash, atmospheric and vacuum columns) with a capacity of 100000 bbl/day. The system has 4 pumparounds, 3 side strippers, 2 condensers and 3 furnaces, and therefore it represents a broad casuistic of chemical processes. Hot utility (vapor) represents 80% of the energy requirement, while the first two columns consume 80% of the utilities. The process is modeled using AspenPlus®, while the environmental loads of the process inputs were retrieved from the ETH Report and the TEAM® database. Environmental calculations were done for the whole process, for each unit and for each piece of equipment, mainly the boiler and the furnaces, to clarify calculations. As expected, most of the CO2 emissions are related with the units with higher energy consumption.
As a motivation for process diagnostic, mass and energy input/output tables and environmental impact summary are developed. A mass input/output analysis is performed on the base case flowsheet to generate the process stream information. The motivations for making an energy input/output table are to identify the amount of energy consumed in the process and to seek opportunities to reduce energy consumption by applying heat integration. The environmental impact summary quantifies the emission and impact of each chemical from each piece of equipment. It is utilized to seek opportunities to reduce the environmental impacts by process modification or pollution control.
After simulation of the flowsheet by incorporating the diagnostics, then multi-objective optimization is applied to the modified process. The utility requirements and environmental emissions are optimized for a sustainable design of the process.
This approach shows a promising advance in the effort towards sustainable design of chemical processes in general, and petroleum refineries in particular. However, there is no sharp definition for sustainability in the context of chemical process design; and as stakeholders and policy makers are becoming more concerned about the environment and energy security there is a lot to be done in this direction and this work is a milestone towards the intended objective.
Presented Monday 17, 13:30 to 15:00, in session Environmental Engineering & Management (T1-3P).
