Industrial Area-wide Layout Optimization Based On Surplus Rectangle Fill Algorithm

Plant layout problem is a creative task that requires project experience.Various factors need to be considered.It influences the logistics,efficiency,capital cost and safety of the entire system in the design of new plant or the retrofit of old plant.At present,most researchers studied on the layout design of facilities in a plant but not plants in an area.And few researchers studied on the relationship of area-wide layout and facility layout.In this paper,the area-wide layout problem and the relationship of area-wide layout and facility layout are considered.Plants and facilities are simplified as rectangles.A new algorithm which combines surplus rectangle fill algorithm and genetic algorithm is proposed to solve the layout problem.The objective function of the proposed mathematical model in the first part of this paper is to minimize the occupied area in the area-wide layout.Those plants with material relationships are put together.Considering the requirement on the natural conditions,transport conditions and other factors around the area,the positions of some specified plants are fixed.These consideration makes the layout more reasonable and practical.A refinery is optimized and the optimized layout is compared with original layout.The result shows that the optimized layout is better than the original layout.The occupied area is reduced and the land utilization is increased which demonstrates the effectiveness of proposed methodology.Then,occupied area and material connections are both considered.Three different objective functions are set to optimize area-wide layout.The results are discussed.As the land cost accounts for a large proportion of the total cost,some plants are regarded as the key plants whose aspect ratios are adjusted to optimize the area-wide layout and reduce land cost.The optimized-layout is compared with the layout with fixed-size plants.Results show that optimizing the occupied area and material connections simultaneously obtains the best area-wide layout and changing the aspect ratio of key plant can effectively reduce occupied area.The relationship of area-wide layout and facility layout is considered.The plant whose area or aspect ratio change can significantly reduce the area-wide layout area is taken as the key plant among all plants.Then,the area and aspect ratio of the key plant are changed.The surplus rectangle fill algorithm and genetic algorithm are combined to optimize the facility layout inside key plant.Many constrains are considered to make the layout more reasonable and practical.The tall facilities such as towers and reactors are arranged across the floor.The objective function of the facility layout is to minimize the total cost including land cost,piping investment cost,pumping operating cost and floor construction cost.The key plant after construction has new area and aspect ratio.The optimized area-wide layout with constructed plant is compared with original layout.The results show that the area-wide layout cost is reduced effectively after the construction of the key plant.The mathematical model and algorithm in this paper can solve large-scale layout problems and provide some reference to engineers in the plant design.