Abstract
The depletion of fossil resources and the ever increasing demand on the reduction of GHG emissions have driven the process industry towards incorporating renewable feedstock, i.e. biomass, for producing energy, chemicals, and materials. Given the vast amount of possibilities in selecting the types of biomass feedstock, conversion technologies, and target products, a systematic approach is highly desirable to support the decision making process. Along this direction, tools including simulation analysis and process synthesis and integration have already been applied to the investigation and optimisation of individual plants or processes for biomass conversion. As opposed to the study of individual processes, the Department of Environment, Food and Rural Area (DEFRA) in UK has supported the development of a systematic approach to screen biomass feedstocks and design options that may involve multiple interconnected processes. In this work, a Unit of Synthesis (UoS), typically representing a complete conversion process, e.g. that of bioethanol or biodiesel production, can be connected with other UoS to form a production chain, which is referred to as a processing route. An example of a two-step processing route is the production of ethanol by fermentation (UoS 1) followed by a dehydration process (UoS 2) to eventually produce ethylene. Furthermore, multiple feasible routes, often involving common processing steps or UoS, may be formulated into a superstructure to represent all the possibilities for converting a set of feedstocks to a set of products. The optimisation of the superstructure against economical, energy, and/or GHG objectives will allow to systematically identify promising configuration(s) of the production system, represented by the best combination(s) of chosen feedstocks, processing steps, and products. The above functionalities are currently being implemented in a systems platform to meet different levels of industrial needs. The platform consists of a central spreadsheet-based database, a spreadsheet-based simulation tool to allow the evaluation of pre-defined processing routes, and a GAMS-based synthesis tool to perform superstrcuture-based optimal screening/configuration. The contral database holds data of individual Units of Synthesis and other common data such as prices of chemicals/utilities. This database is shared by both the simulation tool and the synthesis tool. The DEFRA-funded project aims to study eight chemicals, which include two key chemicals namely ethylene and propylene glycol. A number of routes have been identified for producing each of the two key chemicals. The systems platform will be tested in the first pace by case studies addressing these two chemicals separately or jointly.