LAYOUT OF PROCESS PLANTS - A NOVEL-APPROACH

Plant layout is concerned with the spatial arrangement of processing e quipment, storage vessels and their interconnecting pipework. This is an important aspect in the design of chemical and process plants since a good layout will ensure that the plant functions correctly and will provide an economically acceptable balance between the many, often co nflicting, design constraints. These constraints are derived from safe ty, environmental, construction, maintenance and operational considera tions. Process relationships, for example the use of gravity flow, and issues such as the provision of space for future expansion must also be taken into account. Traditional methods for locating equipment with in chemical plants are based on mixtures of process heuristic rules an d exact-to-the-inch distance information. Such techniques are unsystem atic and they do not make use of all the relevant and appropriate data . In this paper an optimization based approach is used to determine a good preliminary plant layout, subject to all of the above constraints . A novel mathematical formulation is presented which addresses the pr oblem of locating items of equipment within a given two or three dimen sional space. The objective function to be minimised is the sum of the relevant operation, connection and floor construction costs. Detailed cost factors ate used to account for the flow direction between two c onnected units. The problem is formulated as a mixed integer linear pr ogramming problem. Specific attention is paid to constructing a formul ation which is suitable for the solution of large scale problems. The method presents the rigorous solution of problems with around 30 proce ss equipment and of essentially unlimited size problems when combined with single heuristic rules. The approach is demonstrated with several practical scale problems, including an industrial multi-purpose plant .