A demand exists to reduce environmental impacts caused by the consumption of energy and the generation of wastes in chemical manufacturing processes. Throughout the life-cycle of a chemical process opportunities can be identified to reduce potential impacts. In terms of intrinsic waste generation and energy consumption, design modifications are most cost effective during conception. However conceptual design is often limited by resource constraints and principally driven by economic considerations. The identification and comparison of design modifications is not typically practised consistently or routinely in the context of pollution prevention. In this research the prototype of a computer based system was developed, P2TCP (Pollution Prevention Tool for Continuous Processes), to help d...[ Read more ]

A demand exists to reduce environmental impacts caused by the consumption of energy and the generation of wastes in chemical manufacturing processes. Throughout the life-cycle of a chemical process opportunities can be identified to reduce potential impacts. In terms of intrinsic waste generation and energy consumption, design modifications are most cost effective during conception. However conceptual design is often limited by resource constraints and principally driven by economic considerations. The identification and comparison of design modifications is not typically practised consistently or routinely in the context of pollution prevention. In this research the prototype of a computer based system was developed, P2TCP (Pollution Prevention Tool for Continuous Processes), to help designers systematically identify pollution prevention opportunities and assess designs in terms of environmental impacts on a scientific basis. The tool is applicable for continuous chemical processes and can be used during conceptual as well as retrofit design therefore facilitating the development of inherently cleaner processes.

Available resource limited methodologies for the assessment and comparison of process designs in terms of regional scale environmental impacts are often limited by subjectivity. No consensus has been reached. Relative Impact Potentials (RIPS) are proposed in this research as a scientific basis for assessment in terms of regional scale impacts. A resource limited approach was developed for P2TCP, based on generally available data and associated assumptions, to render RIPs readily usable. Unlike typical methodologies, transfer between environmental compartments, degradation processes and increased exposure associated with bed sediment concentrations are taken into consideration. The suitability of the proposed RIP approach to provide a discriminatory basis is assessed quantitatively in terms of uncertainty.

An expert system, developed for P2TCP, facilitates the systematic identification of process design modifications which may result in reduced energy consumption and waste generation. The heuristics were derived by applying fundamental chemical engineering principles. Case studies are not used as the principle knowledge source but for validation and for the identification of further extensions. In the context of pollution prevention and unlike sequential methodologies used for design synthesis, each system of a process (reaction and separation) is analysed independently and then potential interactions are considered. The analysis performed is resource limited and does not require prior specification of a process flow diagram facilitating the use of P2TCP during conceptual as well as retrofit design.

Using P2TCP design modifications were identified and alternatives compared in the context of pollution prevention for a number of continuous chemical processes. Processes considered include the production of allyl chloride, the manufacture of chlorobenzenes and the separation of a mixed hydrocarbon stream generated in naphtha reforming units of oil refineries. The resources required to systematically identify opportunities and the degree of subjectivity associated with comparison were significantly reduced.