DEVELOPING NETWORK MODELS OF INDUSTRIAL SYMBIOSIS

Abstract

: This study aimed to examine whether industrial symbiosis (IS) could be applied on the Point Lisas Industrial Estate (PLIE) in Trinidad and Tobago for the reuse of process carbon dioxide (CO 2 ) within the estate. To acquire optimal networks, initially simplified petrochemical complexes were posed as transportation-type problems and solved with linear programming and mixed integer linear programming techniques. Network models were developed in which process CO 2 was optimally allocated between existing ammonia (sources) and methanol plants (sinks) on the PLIE. Multiple scenarios were considered including possible restrictions on CO 2 -transfers from sources or to sinks. The functionality of the developed network models was confirmed with three test cases. Multi-objective optimization (MOO) was applied to a fourth model, with a secondary objective of minimising operational network costs. In the second stage, an enterprise input-output (EIO) model was developed from both process engineering and economic data. It incorporated performance indicators, which had been proposed in the literature, to calculate the level of industrial symbiosis and benefits - based on “the three pillars of sustainability” - realized in the representative industrial network. On the representative petrochemical network, 17% of the process CO 2 emissions were reused in chemical manufacturing and the eco-connectance, which is one measure of the level of IS, was determined as 1.33. This demonstrates the presence and level of IS in the industrial park. Furthermore, optimized flow networks were created, with and without a CO 2 -reusing propylene carbonate plant. MOO was used to determine how to add the CO 2 -reusing plant to the industrial network to minimize both CO 2 emissions and implementation costs. The addition of a CO 2 -reusing plant reduced the CO 2 emissions by 1.1%, demonstrating there is scope for improving the existing IS network. examine how CO 2 , produced on the PLIE, could be reused within the estate through exchanges between various petrochemical plants and secondly to assess the level of industrial symbiosis occurring in the industrial park. The aim was to develop a simple representative model of this nascent symbiotic industrial system, in terms of CO 2 exchanges at PLIE. Our model was then used to perform an integrated process engineering and economic analysis to quantify the level of exchanges and benefits beneath “the three pillars of sustainability” and thence determine the scope for improvement. for proposed base, current cases. cases EIO for the current case approximately 17% of the CO 2 was in methanol and plants and the was vented a new plant, CO the CO 2 usage by approximately 1.1%, amount of CO 2 the the EIO table, the direct and total coefficients were Analysis of the direct coefficients that the largest direct coefficient for the by-products and was attributed to the nearly pure CO 2 being emitted from the ammonia plants. The core EIO model gives an idea of the material and flow exchanges within the network, but does not measure the level of industrial symbiosis. The calculated values for the performance indicators, used to measure IS in these three cases, are shown