Coupling Process Plants and Utility Systems for Site Scale Steam Integration

Abstract

The refining and petrochemical industries generally own process plants and utility systems. Process plants are configured to finish the transformation and separation of materials, and utility systems supply the energy requirements for the process plants. Therefore, integrating two of them is more favorable than optimizing them individually. A coupling mixed integer nonlinear programming model is presented in this work to integrate process plants and utility systems; the objective is to minimize the energy costs to meet the requirements of the process operations and to maintain a steam balance in the total site. The mathematical model includes three parts: the heat integration of the process plants, the optimization of the utility system, and the coupling equations for the site-scale steam integration. The heat integration of the process plant is formulated on the basis of pinch analysis involving heat loads of the process heaters and steam generation and requirements. An optimization of the utility system is also proposed to provide the relationship between steam balance, power generation, and fuel requirements. Coupling equations are used to balance the steam streams in each level between the process plants and utility systems. Two real industrial examples are also investigated to demonstrate the performance of the presented mathematical model. The solution results indicate not only a more profitable integration scheme but also increases in energy utilization efficiencies and the operational capacities of the utility systems.

Energy-efficient scheduling in manufacturing companies: A review and research framework

“…Additionally, without using the energy storage capabilities, the external cold utility requirements decrease by 25%; when using the storage system, the external cold utility requirements decrease by 25%. Simultaneously, the profit increases by 5.22% and 6.45%, respectively Zhang et al (2013a). analyse two refineries (both of which are classified as (PS,iCS|H,O,CHP,ERS|MR)) and three energy integration levels.…”

“…analyse two refineries (both of which are classified as (PS,iCS|H,O,CHP,ERS|MR)) and three energy integration levels. In the first case, the resulting energy costs of 7,508 CNY/hour, 6,509 CNY/hour, and 6,013 CNY/hour indicate that the lowest cost can be achieved with "a complete steam integration between process plants and utilityZhang et al, 2013a). This observation is confirmed by the energy costs for the second case: 12,168 CNY/hour, 956 CNY/hour, and -3,323 CNY/hour, where the energy expenses become revenue for the level-3 integration.…”

Quantitative tools for cultivating symbiosis in industrial parks; a literature review

“…Kim et al [101] presented a model along with a case study which produced environmental and economic optimized results with seasonal fluctuations. A petrochemical and refinery system was modelled by Zhang et al [102] to couple process plants with utility systems allowing for three increasing levels of integration between the processes and the steam network.…”

A multi-period mathematical model for simultaneous optimization of materials and energy on the refining site scale

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“…Recently, a retrofit framework for total site heat recovery systems was presented to determine the most cost-effective retrofit options and maximize potential savings, and a petrochemical site was tested [32]. The transshipment model was extended in some works to allow direct hot discharges/feeds between units for heat integration between process units and steam streams [33,34]. Heat integration between processes and utility systems were also investigated for some process industries, such as pulp and paper mill evaporation plants [35,36], juice processing plants [37], and industrial sawmill sites [38].…”