The importance of resource efficiency within industry has gained significant traction in recent years, and is now firmly established as an effective means of cost reduction for manufacturing companies of all sizes. This focus has been driven by a number of factors including the rising cost of energy and raw materials, market volatility, declines in resource availability/accessibility, and external regulation pressures. The ability to simultaneously reduce processing costs and reduce environmental impact has allowed resource efficiency to act as key bridge between business operators and environmental policymakers. From an economic and environmental perspective, it’s a win-win situation.
Despite a wider consensus on why resource efficiency is important, effective methods of optimisation are still poorly established. There are a number of analytical process techniques which are suitable for use in the chemical industry (including material flow networks, flow sheet simulation, material-flow cost accounting, heat integration and life-cycle analysis); however the isolated use of any of these presents significant drawbacks. Effective action requires not only process scalability and full supply-chain analysis, but also method integration combining aspects of process and chemical engineering, operations research, environmental assessment and managerial accounting. Such systematic approaches are currently rare, primarily due to a lack of platforms available to do so.
Recognition of this need for more established integrative methods was the basis for the design of InReff (Integrated Resource Efficiency Analysis for Reducing Climate Impacts in the Chemical Industry)—an interdisciplinary project created and partly funded by the German Federal Ministry of Education and Research (BMBF), featuring the collaboration of three chemical industry producers, an IT software-based company, and two academic partners based in thermal and chemical engineering. The overall aim of InReff is to develop an integrated IT-based support platform which companies (primarily aimed at small and medium-sized enterprises; SMEs) can utilise to optimise resource efficiency—tackling both cost reduction and carbon emissions within the chemical industry.
Traditional resource efficiency enhancement methods typically involve the use of material and energy flow analysis (MEFA). In simple terms, this involves an average measurement of material and energy inputs and outputs of a system over a given period of time; calculating the balance of inputs and outputs in each process allows a business to identify their largest waste streams. MEFA methods prove effective for broad, high-level identification of whole-process inefficiencies. However, the black box approach is insufficient at capturing the complexity of chemical processes including non-linear transitions, material loops and recycling, and design-level thermodynamic specifications. The integration of higher resolution, process specific causalities to coarse-grained MEFA methods forms the basis of the InReff integrative techniques.
The InReff approach can be broken down into four key steps:
Step 1: Material Flow Networks (MFNs) can be modelled using Umberto software tools (developed by ifu Hamburg), and form the backbone of the overall production process. Step one involves the integration of MFN models with Flow Sheet Simulation (FSS) techniques. In contrast to MFNs, FSSs are much finer-grained and describe the interactions between processing unit operations (e.g. pumps, heat exchangers, flashes). FSSs involve the population of chemical transitions with specific thermodynamic and substance properties, allowing for calculation of further properties such as pressure or enthalpy, not explicitly given in the initial model.
As with MFNs, there are several reasons why the isolated use of FSSs presents significant weaknesses for resource efficiency modelling. Due to the number of substance and thermodynamic properties which must be considered, the complexity of some FSS calculations means that results don’t necessarily converge, often making it unsuitable for modelling large facilities or processes. FSSs are also often not populated with cost accounting and impact assessment data, meaning that any enhancements in process operations can’t be analysed in terms of the true savings returned to the company or regulators.
MFNs and FSSs, despite their relative drawbacks, represent two key complementary modelling techniques which can be effectively integrated for use in the chemical industry. A coarse-grained model of a whole facility can be setup using MFN techniques in Umberto, with the most relevant sub-processes then modelled in more detail using FSS software techniques. The plug-in software tool used for FSS analysis in the InReff project is CHEMCAD. The ease with which software tools can be connected to spreadsheet applications makes spreadsheet-based data exchange methods the preferred option for the project.
In other words, the MFN serves as the main process model, calling upon the FSS software for data requests for specific sub-models when needed. The material and energy inflows and outflows from FSS calculations can then be analysed in terms of cost and ecological impacts via the MFN tool.
Step 2: The compatibility of the main process model means that additional modelling techniques can be easily integrated for more specific analysis. In the case of the InReff project, a key additional plug-in involves a Heat Integration connector. A widely-used method for Heat Integration analysis is the pinch point method.
Such techniques can support efficiency gains by helping to identify potential areas where heat surpluses can be recycled and utilised elsewhere. Heat generation and cooling processes are often energy-intensive—analysis for potential internal heat integration and external supply requirements can therefore result in significant efficiency gains. After investigating the potential for heat integration, optimised energy and cost balance data can then be re-imported back into the Umberto tool.
Step 3: Once efficiency analysis has been completed, key outputs are summarised and converted for effective visual understanding. Sankey diagrams—a flow diagram in which the width of the arrows are proportional and representative of the flow quantity (energy, material or cost in this case)—are used by Umberto to present a visual display of the key flow routes and waste streams. Sankey diagrams are effective in providing users with a quick overview of dominant economic and environmental flows within their facilities.
These overall results allow for a total process or product footprint to be calculated, and for potential efficiency gains to be quantified in terms of economic and environmental benefit.
Step 4: Users can carry out Steps 1-3 manually or using “what if” scenarios in order to derive resource efficiency gains. However, the InReff project has developed a process optimisation plug-in, Umberto Optimizer, which calculates the optimal process design conditions according to the company’s optimisation goals. In this mathematical-based optimisation stage, visual material flows can be converted into mathematical equations, for which solver engines deliver optimal parameter solutions for a given goal (such as waste minimisation or revenue maximisation).
The InReff project has so far developed an IT-based platform which offers an integrated, holistic software tool which can be used for effective resource efficiency optimisation in the chemical industry. Such methods provide an effective means of improving both the ecological and economic prospects of a company’s operations—it therefore incites attention from business as well as policymakers. Effective sustainability progress requires the bridging of these stakeholder groups; InReff has used a bridge of conventional analytic methods to do just that.
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